Directory of Open Access Journals (Sweden)
Xiurong Zuo
2012-12-01
Full Text Available A kind of medium-carbon low-alloy dual-phase steels with high-content martensite produced by intercritical annealing at 785-830 ºC for 10-50 minutes were studied in aspect of microstructures and work hardening behavior using SEM and tensile testing machine. The experimental results showed that the work hardening of the studied steels obeyed the two-stage work hardening mechanism, whose work hardening exponent of the first stage was higher than that of the second stage. The work hardening exponent increased with increasing the intercritical annealing temperature and time. For series A steel intercritically annealed at 785 ºC with starting microstructure of ferrite plus pearlite, austenite nucleated at the pearlite colonies, so the holding time of only 50 minutes can increase the work hardening exponent obviously. For series B steel with starting microstructure of martensite, austenite nucleated at lath interfaces, lath colony boundaries of primary martensite and carbides, accelerating the formation of austenite, so holding time for 30 minutes made the work hardening exponent increase obviously. High work hardening rate during initial plastic deformation (<0.5% strain was observed.
"Work-Hardenable" ductile bulk metallic glass.
Das, Jayanta; Tang, Mei Bo; Kim, Ki Buem; Theissmann, Ralf; Baier, Falko; Wang, Wei Hua; Eckert, Jürgen
2005-05-27
Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.
Microstructure, Tensile Properties and Work Hardening Behavior of GTA-Welded Dual-Phase Steels
Ashrafi, H.; Shamanian, M.; Emadi, R.; Saeidi, N.
2017-03-01
In the present study, microstructure, tensile properties and work hardening behavior of a DP700 steel after gas tungsten arc welding were investigated. Formation of bainite in the fusion zone resulted in a hardness increase compared to that for the base metal (BM), whereas tempering of the pre-existing martensite in the subcritical heat-affected zone (HAZ) led to softening. The GTA-welded joint exhibited a continuous yielding behavior and a yield strength close to that for the BM, while its ultimate tensile strength and total elongation were lower than those for the BM owing to the formation of soft zone in the HAZ. A joint efficiency of about 81% was obtained for the GTA-welded joint, and it failed in the softened HAZ. Analysis of work hardening based on the Kocks-Mecking approach showed one stage of hardening behavior corresponding to the stage III for both the DP700 BM and welded sample. It was also revealed that the DP700 BM has larger values of work hardening exponent and magnitude of work hardening compared with the welded sample. Analysis of fractured surfaces showed that the dominant fracture mode for both the DP700 BM and welded joint was ductile.
Role of work hardening characteristics of matrix alloys in the ...
Indian Academy of Sciences (India)
The strengthening of particulate reinforced metal–matrix composites is associated with a high dislocation density in the matrix due to the difference in coefficient of thermal expansion between the reinforcement and the matrix. While this is valid, the role of work hardening characteristics of the matrix alloys in strengthening of ...
Coefficient of work-hardening in stage-IV
CSIR Research Space (South Africa)
Nabarro, FRN
1994-04-15
Full Text Available The theory of work hardening in stage IV depends on the relation between the relative misorientation Psi of neighbouring subgrains and the plastic strain gamma (Psi = B gamma exp). The value of the constant B is suggested to be better related...
Mirzadeh, Hamed; Alibeyki, Mohammad; Najafi, Mostafa
2017-10-01
Ferritic-martensitic, dual-phase (DP) microstructures with different size, morphology, and distribution of martensite were produced by altering the initial microstructures using heat treatment and thermomechanical processing routes. It was revealed that the strength, ductility, and work-hardening rate of DP steels strongly depend on the volume fraction and the morphology of the martensite phase. In this regard, the fine-grained DP microstructure showed a high work-hardening ability toward an excellent combination of strength and ductility. Such a microstructure can be readily obtained by intercritical annealing of an ultrafine grained (UFG) microstructure, where the latter can be produced by cold-rolling followed by tempering of a martensite starting microstructure. Conclusively, the enhancement of mechanical properties of DP steels through microstructural refinement was found to be more beneficial compared with increasing the volume fraction of martensite. Finally, it was also demonstrated that the work-hardening rate analysis based on the instantaneous (incremental) work-hardening exponents might be an advantageous approach for characterizing DP steels along with the conventional approaches.
Ductility and work hardening in nano-sized metallic glasses
Chen, D. Z.; Gu, X. W.; An, Q; Goddard, W. A.; Greer, J. R.
2015-01-01
In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of fr...
Ductility and work hardening in nano-sized metallic glasses
Energy Technology Data Exchange (ETDEWEB)
Chen, D. Z., E-mail: dzchen@caltech.edu [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); Gu, X. W. [Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); An, Q.; Goddard, W. A. [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States); Greer, J. R. [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); The Kavli Nanoscience Institute, California Institute of Technology, Pasadena, California 91125 (United States)
2015-02-09
In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.
Disorientations and work-hardening behaviour during severe plastic deformation
DEFF Research Database (Denmark)
Pantleon, Wolfgang
2012-01-01
Orientation differences develop during plastic deformation even in grains of originally uniform orientation. The evolution of these disorientations is modelled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different...... types of boundaries are in agreement with experimental data for small and moderate plastic strains. At large plastic strains after severe plastic deformation, saturation of the measured average disorientation angle is observed. This saturation is explained as an immediate consequence of the restriction...... pressure torsion, but also rationalizes the work-hardening behaviour at large plastic strains as well as a saturation of the flow stress....
Cognitive work hardening: a return-to-work intervention for people with depression.
Wisenthal, Adeena; Krupa, Terry
2013-01-01
Mental health claims in the workplace are rising, particularly those due to depression. Associated with this is an increase in disability costs for the employer and the disability insurer, but even more important is the human suffering that results. While treatments are available for the depression there is a gap in interventions that specifically target return-to-work preparation. This paper presents cognitive work hardening, a treatment intervention that can bridge this gap by addressing the unique functional issues inherent in depression with a view to increasing return-to-work success. Cognitive work hardening applies the proven principles of classical work hardening (which has typically been applied to people with physical injuries) to the mental health domain. This paper explains how the occupational therapy principle of occupation and the core competency, enablement, are utilized and applied in cognitive work hardening. Key skills of the occupational therapist are also discussed. In addition, the paper considers the relationship of cognitive work hardening to recovery and mental illness, and the role it plays among workplace-based return-to-work interventions in the current movement toward non-clinical return-to-work interventions.
Fitting Power-laws in empirical data with estimators that work for all exponents
Hanel, Rudolf; Liu, Bo; Thurner, Stefan
2016-01-01
It has been repeatedly stated that maximum likelihood (ML) estimates of exponents of power-law distributions can only be reliably obtained for exponents smaller than minus one. The main argument that power laws are otherwise not normalizable, depends on the underlying sample space the data is drawn from, and is true only for sample spaces that are unbounded from above. Here we show that power-laws obtained from bounded sample spaces (as is the case for practically all data related problems) are always free of such limitations and maximum likelihood estimates can be obtained for arbitrary powers without restrictions. Here we first derive the appropriate ML estimator for arbitrary exponents of power-law distributions on bounded discrete sample spaces. We then show that an almost identical estimator also works perfectly for continuous data. We implemented this ML estimator and discuss its performance with previous attempts. We present a general recipe of how to use these estimators and present the associated com...
The structural dependence of work hardening in low carbon steels
Energy Technology Data Exchange (ETDEWEB)
Johnson, Patricia Elizabeth [Univ. of California, Berkeley, CA (United States)
1991-12-01
The influence of the dislocation cell structure on the work hardening behavior of low carbon steel sheets was investigated. Specimens were prestrained at low temperature to suppress cell formation and their subsequent behavior was compared with results of isothermal reference tests. It was found that the extent of cell development has little or no influence on the plastic behavior at room temperature and below. Interrupted temperature, tensile-shear tests demonstrated further that the transient behavior induced by loading path changes is also not strongly associated with the cell walls. In-situ straining studies indicate that the factor controlling the flow stress at room temperature is the limited mobility of screw dislocations moving the cell interiors, and not dislocation interactions with the cell walls. The unique properties of a/2<111> screw dislocations are known to dominate low temperature deformation behavior in bcc metals. The current work indicates that these dislocations may still control the flow stress at intermediate temperatures, even in the presence of a developed cell structure.
Work-hardening of dual-phase steel
Energy Technology Data Exchange (ETDEWEB)
Rieger, Florian
2016-07-01
Exhibiting good mechanical properties for cold-sheet forming, low-alloyed dual-phase (DP) steels are nowadays widely used for automotive applications. The composite-like microstructure of DP steels is composed of a low-carbon ductile ferrite-matrix and 10 - 60 vol.% hard martensitic inclusions. A nonlinear mean-field model and full-field finite-element simulations are applied to investigate three major topics: the influence of grain-size distribution, grain-level plasticity and derivation of an original material-model. The plastic behavior of polycrystals is assumed to be grain-size dependent in this work. The distribution of grain-sizes is taken to be lognormal. It is found that grain-size dispersion leads to a decrease of the material strength, in particular for small mean diameters around one micron. The numerical results from the mean-field model are confirmed notably well by means of a simple analytical expression. The micromechanical behavior of DP steels is investigated by full-field RVE simulations with a crystal-plasticity based ferrite-matrix and von Mises-type martensite inclusions. To examine the martensite influence, full-field simulation results of DP steels have been compared to an RVE in which martensite is substituted by ferrite. After quenching, a higher grain-boundary area covered by martensite facilitates an increased average dislocation-density. For uniaxial deformations above ∝10%, however, the grain-size dependent relation reverses. With more surrounding martensite, the local crystal-plasticity material-model exhibits hardening at a slower rate. A nonlinear mean-field model of Hashin-Shtrikman type is employed as framework for the original material-model for DP steels. The model incorporates the interaction of ferrite and martensite via incompatibility-induced long-range stresses in an averaged sense. The proposed model combines works of Ashby (1970) and Brown and Stobbs (1971a) to simulate the ferrite behavior. Based on the composite model
Stage IV work-hardening related to disorientations in dislocation structures
DEFF Research Database (Denmark)
Pantleon, W.
2004-01-01
The effect of deformation-induced disorientations on the work-hardening of metals is modelled based on dislocation dynamics. Essentially, Kocks’ dislocation model describing stage III hardening is extended to stage IV by incorporation of excess dislocations related to the disorientations...
Work Hardening Behavior of 1020 Steel During Cold-Beating Simulation
CUI, Fengkui; LING, Yuanfei; XUE, Jinxue; LIU, Jia; LIU, Yuhui; LI, Yan
2017-03-01
The present research of cold-beating formation mainly focused on roller design and manufacture, kinematics, constitutive relation, metal flow law, thermo-mechanical coupling, surface micro-topography and microstructure evolution. However, the research on surface quality and performance of workpieces in the process of cold-beating is rare. Cold-beating simulation experiment of 1020 steel is conducted at room temperature and strain rates ranging from 2000 to 4000 s-1 base on the law of plastic forming. According to the experimental data, the model of strain hardening of 1020 steel is established, Scanning Electron Microscopy(SEM) is conducted, the mechanism of the work hardening of 1020 steel is clarified by analyzing microstructure variation of 1020 steel. It is found that the strain rate hardening effect of 1020 steel is stronger than the softening effect induced by increasing temperatures, the process of simulation cold-beating cause the grain shape of 1020 steel significant change and microstructure elongate significantly to form a fibrous tissue parallel to the direction of deformation, the higher strain rate, the more obvious grain refinement and the more hardening effect. Additionally, the change law of the work hardening rate is investigated, the relationship between dislocation density and strain, the relationship between work hardening rate and dislocation density is obtained. Results show that the change trend of the work hardening rate of 1020 steel is divided into two stages, the work hardening rate decreases dramatically in the first stage and slowly decreases in the second stage, finally tending toward zero. Dislocation density increases with increasing strain and strain rate, work hardening rate decreases with increasing dislocation density. The research results provide the basis for solving the problem of improving the surface quality and performance of workpieces under cold-beating formation of 1020 steel.
Work-hardening induced tensile ductility of bulk metallic glasses via high-pressure torsion
National Research Council Canada - National Science Library
Joo, Soo-Hyun; Pi, Dong-Hai; Setyawan, Albertus Deny Heri; Kato, Hidemi; Janecek, Milos; Kim, Yong Chan; Lee, Sunghak; Kim, Hyoung Seop
2015-01-01
.... Enhanced tensile ductility and work-hardening behavior after the HPT process were investigated, focusing on the microstructure, particularly the changed free volume, which affects deformation mechanisms (i.e...
Kowser Md. A.; Mahiuddin Md.
2014-01-01
In this paper a technique has been developed to determine constant parameters of copper as a power-law hardening material by tensile test approach. A work-hardening process is used to describe the increase of the stress level necessary to continue plastic deformation. A computer program is used to show the variation of the stress-strain relation for different values of stress hardening exponent, n and power-law hardening constant, α . Due to its close tolerances, excellent corrosion resistanc...
Crauel, Hans; Eckmann, Jean-Pierre
1991-01-01
Since the predecessor to this volume (LNM 1186, Eds. L. Arnold, V. Wihstutz)appeared in 1986, significant progress has been made in the theory and applications of Lyapunov exponents - one of the key concepts of dynamical systems - and in particular, pronounced shifts towards nonlinear and infinite-dimensional systems and engineering applications are observable. This volume opens with an introductory survey article (Arnold/Crauel) followed by 26 original (fully refereed) research papers, some of which have in part survey character. From the Contents: L. Arnold, H. Crauel: Random Dynamical Systems.- I.Ya. Goldscheid: Lyapunov exponents and asymptotic behaviour of the product of random matrices.- Y. Peres: Analytic dependence of Lyapunov exponents on transition probabilities.- O. Knill: The upper Lyapunov exponent of Sl (2, R) cocycles:Discontinuity and the problem of positivity.- Yu.D. Latushkin, A.M. Stepin: Linear skew-product flows and semigroups of weighted composition operators.- P. Baxendale: Invariant me...
Work-hardening of dual-phase steel
Rieger, Florian
2016-01-01
Low-alloyed dual-phase steels are widely used for automotive applications. The favorable mechanical properties of this material class are induced by the composite-like microstructure, i.e., strong martensitic inclusions embedded into a ductile ferrite matrix. This work presents a nonlinear two-scale model that is physically-motivated. The model comprises long-range stresses and includes microstructural parameters. It is suitable to predict the mechanical behavior of different dual-phase steels.
Energy Technology Data Exchange (ETDEWEB)
Ojima, M., E-mail: 07nd602g@hcs.ibaraki.ac.jp [Graduate School of Science and Engineering, Ibaraki University, Nakanarusawa, 316-8511 Hitachi, Ibaraki (Japan); Adachi, Y. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Tomota, Y. [Graduate School of Science and Engineering, Ibaraki University, Nakanarusawa, 316-8511 Hitachi, Ibaraki (Japan); Ikeda, K. [Sumitomo Metal Industries, Ltd., Hikari, Kashima, Ibaraki 314-0014 (Japan); Kamiyama, T. [Institute of Material Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Katada, Y. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)
2009-12-15
With a focus on microstructural hierarchy, work hardening behaviour in high nitrogen-bearing austenitic steel (HNS) was investigated mainly by a combined technique of in situ neutron diffraction and in situ electron backscattering diffraction (EBSD). Stress partitioning due to difference in deformability among grains is enhanced in HNS. The larger stress partitioning among [h k l]-oriented family grains seems to realize high work hardening at a small strain. At a larger strain, dislocation density is higher in HNS than in low nitrogen austenitic steel (LNS), which is a possible reason for high work hardening after straining proceeds, resulting in large uniform elongation.
Surface hardening using cw CO2 laser: laser heat treatment, modelation, and experimental work
Muniz, German; Alum, Jorge
1996-02-01
In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.
Barreira, Luís
2017-01-01
This book offers a self-contained introduction to the theory of Lyapunov exponents and its applications, mainly in connection with hyperbolicity, ergodic theory and multifractal analysis. It discusses the foundations and some of the main results and main techniques in the area, while also highlighting selected topics of current research interest. With the exception of a few basic results from ergodic theory and the thermodynamic formalism, all the results presented include detailed proofs. The book is intended for all researchers and graduate students specializing in dynamical systems who are looking for a comprehensive overview of the foundations of the theory and a sample of its applications.
ON THE ELASTIC-PLASTIC TORSION OF A BAR MADE OF WORK HARDENING MATERIAL
Directory of Open Access Journals (Sweden)
Yaşar PALA
1995-01-01
Full Text Available In this study, we reconsider the problem of an elastic-plastic torsion of a bar made of work hardening material. Nonlinear partial differential equation derived is reduced to a well known Laplace equation by means of transformation functions and stresses τ xz, τ yz and the torque T are analytically found for elliptical and circular cross sections. It is further shown that the stresses and the twisting moment do not depend on the value of n in the stress-strain law.
Work-hardening induced tensile ductility of bulk metallic glasses via high-pressure torsion.
Joo, Soo-Hyun; Pi, Dong-Hai; Setyawan, Albertus Deny Heri; Kato, Hidemi; Janecek, Milos; Kim, Yong Chan; Lee, Sunghak; Kim, Hyoung Seop
2015-04-23
The mechanical properties of engineering materials are key for ensuring safety and reliability. However, the plastic deformation of BMGs is confined to narrow regions in shear bands, which usually result in limited ductilities and catastrophic failures at low homologous temperatures. The quasi-brittle failure and lack of tensile ductility undercut the potential applications of BMGs. In this report, we present clear tensile ductility in a Zr-based BMG via a high-pressure torsion (HPT) process. Enhanced tensile ductility and work-hardening behavior after the HPT process were investigated, focusing on the microstructure, particularly the changed free volume, which affects deformation mechanisms (i.e., initiation, propagation, and obstruction of shear bands). Our results provide insights into the basic functions of hydrostatic pressure and shear strain in the microstructure and mechanical properties of HPT-processed BMGs.
Low beryllium content Zr-based bulk metallic glass composite with plasticity and work hardenability
Energy Technology Data Exchange (ETDEWEB)
Zheng, Q., E-mail: qiangzheng616@hotmail.com, E-mail: dujuan@nimte.ac.cn [School of Materials Science and Engineering, Ningbo University of Technology, Ningbo, 315016, China and Ningbo Branch of China Academy of Ordnance Science, Ningbo, 315103 (China); Du, J., E-mail: qiangzheng616@hotmail.com, E-mail: dujuan@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS), Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, NIMTE, CAS, Ningbo 315201 (China)
2014-01-28
A modified Zr-based bulk metallic glass matrix composite Zr{sub 47.67}Cu{sub 40}Ti{sub 3.66}Ni{sub 2.66}Be{sub 6} has been produced by increasing the contents of elements of Zr and Cu with higher Poisson ratio and reducing the contents of Ti, Ni, and Be elements with lower Poisson ratio based on famous metallic glass former Vitreloy 1. A compressive yielding strength of 1804 MPa, fracture strength of 1938 MPa and 3.5% plastic strain was obtained for obtained metallic glass composite. Also, work-hardening behavior was observed during compressive experiment which was ascribed to the interaction of the in situ precipitated CuZr phase and shear bands.
Cetlin, P. R.; Corrêa, E. C. S.; Aguilar, M. T. P.
2003-03-01
The work-hardening characteristics of metals deeply affect the analytical and numerical analyses of their forming processes and especially the end mechanical properties of the products manufactured. The effects of strain, strain rate, and temperature on work hardening have received wide attention in the literature, but the role of the strain path has been far less studied, except for sheet-metal forming. Strain-path effects seem to have never been analyzed for bulk-forming processes, such as axisymmetric drawing. In the present work, drawn bars were considered as composed of concentric layers strained along varying strain paths. The tensile von Mises effective stress, effective-strain curves of two layers and of the full cross section of the drawn material, were experimentally determined. The flow behavior of these regions was compared to that resulting from pure monotonic-tensile processing. The AISI 420 and 304 stainless steels revealed a strain path and a material effect on their work-hardening characteristics. Higher or lower hardening rates were observed in axisymmetric drawing, as compared to pure tension. These phenomena were interpreted by considering the dislocation arrangements caused by initial drawing straining and their subsequent restructuring, associated with the strain-path change represented by tension after drawing. The analytical and numerical analyses of the tensile behavior of metals following axisymmetric drawing must consider the strain-path effects on the constitutive equations laws and on the hardening behavior of the material. The redundant deformation factor in axisymmetric drawing ( φ) plays a central role in the analysis of the process and on the prediction of the mechanical properties of the final products. This parameter was evaluated considering (a) the strain distribution in the bar cross section caused by drawing or (b) the mechanical properties of the drawn bars. The comparison of the results from these two approaches allowed an
Evolution of stacking fault tetrahedral and work hardening effect in copper single crystals
Liu, Hai Tao; Zhu, Xiu Fu; Sun, Ya Zhou; Xie, Wen Kun
2017-11-01
Stacking fault tetrahedral (SFT), generated in machining of copper single crystal as one type of subsurface defects, has significant influence on the performance of workpiece. In this study, molecular dynamics (MD) simulation is used to investigate the evolution of stacking fault tetrahedral in nano-cutting of copper single crystal. The result shows that SFT is nucleated at the intersection of differently oriented stacking fault (SF) planes and SFT evolves from the preform only containing incomplete surfaces into a solid defect. The evolution of SFT contains several stress fluctuations until the complete formation. Nano-indentation simulation is then employed on the machined workpiece from nano-cutting, through which the interaction between SFT and later-formed dislocations in subsurface is studied. In the meanwhile, force-depth curves obtained from nano-indentation on pristine and machined workpieces are compared to analyze the mechanical properties. By simulation of nano-cutting and nano-indentation, it is verified that SFT is a reason of the work hardening effect.
Energy Technology Data Exchange (ETDEWEB)
Cai, Y.; Wan, L.; Guo, Z. H.; Sun, C. Y.; Yang, D. J.; Zhang, Q. D.; Li, Y. L.
2017-02-01
Isothermal compression experiment of AZ80 magnesium alloy was conducted by Gleeble thermo-mechanical simulator in order to quantitatively investigate the work hardening (WH), strain rate sensitivity (SRS) and temperature sensitivity (TS) during hot processing of magnesium alloys. The WH, SRS and TS were described by Zener-Hollomon parameter (Z) coupling of deformation parameters. The relationships between WH rate and true strain as well as true stress were derived from Kocks-Mecking dislocation model and validated by our measurement data. The slope defined through the linear relationship of WH rate and true stress was only related to the annihilation coefficient Ω. Obvious WH behavior could be exhibited at a higher Z condition. Furthermore, we have identified the correlation between the microstructural evolution including β-Mg17Al12 precipitation and the SRS and TS variations. Intensive dynamic recrystallization and homogeneous distribution of β-Mg17Al12 precipitates resulted in greater SRS coefficient at higher temperature. The deformation heat effect and β-Mg17Al12 precipitate content can be regarded as the major factors determining the TS behavior. At low Z condition, the SRS becomes stronger, in contrast to the variation of TS. The optimum hot processing window was validated based on the established SRS and TS values distribution maps for AZ80 magnesium alloy.
Wisenthal, Adeena; Krupa, Terry
2014-12-12
Mental health related work disability leaves are increasing at alarming rates with depression emerging as the most common mental disorder in the workforce. Treatments are available to alleviate depressive symptoms and associated functional impacts; however, they are not specifically aimed at preparing people to return to work. Cognitive work hardening (CWH) is a novel intervention that addresses this gap in the health care system. This paper presents a theoretical analysis of the components and underlying mechanisms of CWH using Intervention Mapping (IM) as a tool to deconstruct its elements. The cognitive sequelae of depression and their relevance to return-to-work (RTW) are examined together with interpersonal skills and other work-related competencies that affect work ability. IM, a tool typically used to create programs, is used to deconstruct an existing program, namely CWH, into its component parts and link them to theories and models in the literature. CWH has been deconstructed into intervention elements which are linked to program performance objectives through underlying theoretical models. In this way, linkages are made between tools and materials of the intervention and the overall program objective of 'successful RTW for people with depression'. An empirical study of the efficacy of CWH is currently underway which should provide added insight and understanding into this intervention. The application of IM to CWH illustrates the theoretical underpinnings of the treatment intervention and assists with better understanding the linkage between intervention elements and intervention objective. Applying IM to deconstruct an existing program (rather than create a program) presents an alternate application of the IM tool which can have implications for other programs in terms of enhancing understanding, grounding in theoretical foundations, communicating program design, and establishing a basis for program evaluation and improvement.
Springback Analysis in Sheet Metal Forming of Non-linear Work-Hardening material Under Pure Bending
Lal, Radha Krishna; Dwivedi, Jai Prakash; Bhagat, Manish Kumar; Singh, Virendra Pratap
2017-04-01
This paper deals with the springback analysis in sheet metal forming for non-linear work-hardening material under pure bending. Using the deformation theory of plasticity, formulation of the problem and spring back ratio is derived using Ramberg-Osgood stress strain relationship with Tresca and Von-Mises yielding criteria. The results have been representing the effect of different value of Y/E or σo/E ratio, different values of strain hardening index ( n), Poisson's ratio (ν) and thickness on springback ratio (R0/Rf). The main aim of this paper is to study the effects of the thickness, Y/E ratio, n and Poisson's ratio in spring back ratio.
Christopher, J.; Choudhary, B. K.; Isaac Samuel, E.; Mathew, M. D.; Jayakumar, T.
2012-01-01
Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress ( σ)-true plastic strain ( ɛ) data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate ( θ = dσ/ dɛ) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ- σ and θσ- σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures.
Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Gong, Wu; Aizawa, Kazuya; Tichy, Geza; Shi, Zengmin; Ungár, Tamas
2017-09-01
A lath martensite steel containing 0.22 mass pct carbon was analyzed in situ during tensile deformation by high-resolution time-of-flight neutron diffraction to clarify the large work-hardening behavior at the beginning of plastic deformation. The diffraction peaks in plastically deformed states exhibit asymmetries as the reflection of redistributions of the stress and dislocation densities/arrangements in two lath packets: soft packet, where the dislocation glides are favorable, and hard packet, where they are unfavorable. The dislocation density was as high as 1015 m-2 in the as-heat-treated state. During tensile straining, the load and dislocation density became different between the two lath packets. The dislocation character and arrangement varied in the hard packet but hardly changed in the soft packet. In the hard packet, dislocations that were mainly screw-type in the as-heat-treated state became primarily edge-type and rearranged towards a dipole character related to constructing cell walls. The hard packet played an important role in the work hardening in martensite, which could be understood by considering the increase in dislocation density along with the change in dislocation arrangement.
Ren, Sicong; Mazière, Matthieu; Forest, Samuel; Morgeneyer, Thilo F.; Rousselier, Gilles
2017-12-01
One of the most successful models for describing the Portevin-Le Chatelier effect in engineering applications is the Kubin-Estrin-McCormick model (KEMC). In the present work, the influence of dynamic strain ageing on dynamic recovery due to dislocation annihilation is introduced in order to improve the KEMC model. This modification accounts for additional strain hardening rate due to limited dislocation annihilation by the diffusion of solute atoms and dislocation pinning at low strain rate and/or high temperature. The parameters associated with this novel formulation are identified based on tensile tests for a C-Mn steel at seven temperatures ranging from 20 °C to 350 °C. The validity of the model and the improvement compared to existing models are tested using 2D and 3D finite element simulations of the Portevin-Le Chatelier effect in tension.
Directory of Open Access Journals (Sweden)
Erin Morton
2014-10-01
Full Text Available This article will examine the development of a state-sponsored therapeutic craft regime in Nova Scotia in the early to mid-twentieth century. Built on the notion that postwar residents needed "work therapy - not a vacation, but a hardening process" (Black n.d. a: 3 - therapeutic craft emerged in Nova Scotia through a complex combination of the individualization of work habits, the desire to construct an antimodern regional identity around handwork, and the notion that both infirm patients and the province as a whole could be healed from economic stagnation through craft. Key to the success of Nova Scotia's therapeutic craft regime was occupational therapist Mary E. Black's career as director of the provincial government's Handicrafts and Home Industries Division from 1943 to 1955. Black's healthcare training led her to seek out therapeutic possibilities in everyday work activities, not to mention a therapeutic solution to what she called "the atti-tude of most Nova Scotians"[:] defeatism" (Black 1949: 46. Her ability to turn seemingly disparate things - such as Scandinavian design, the ordered work of occupational rehabilitation, and a phenomenological focus on what she called “in-dividualistic existence” (Black n.d. b: 2 - into a unified therapeutic solution demonstrates that the contemporary rise of therapeutic culture under the increased individualism of the neoliberal era has an established historical root in the postwar period that remains important to understand.
Sarkar, Rajdeep; Mukhopadhyay, A.; Ghosal, P.; Nandy, T. K.; Ray, K. K.
2015-08-01
This investigation is aimed at revealing the deformation behavior of a β-Ti alloy, namely Ti-15V-3Cr-3Sn-3Al, under various aged conditions with an emphasis on correlating the work hardening characteristics of the alloy with its corresponding microstructure. The alloy was cast, forged, hot rolled, solution treated, and aged differently to generate microstructures with varying amounts and morphologies of α- and β-phases. While microstructural characterization was carried out using scanning and transmission electron microscopy (TEM), tensile tests were conducted to study the work hardening behavior of the alloy. One may infer from the results that the strength of the alloy deteriorates, while the elongation to failure improves with an increase in the aging temperature. The strength of the alloy depends strongly on the amount of α- and the inter-α-spacing. The work hardening behavior of the alloy aged at temperatures below 808 K (535 °C) is markedly different than those aged at higher temperatures. This characteristic behavior has been explained using the deformation signatures in the α-phase revealed by TEM examinations. A stress gradient-based model and a dislocation evolution-type model are found to satisfactorily describe the strength and the work hardening behavior of the alloy aged under different conditions.
Disorientations and their role on the work-hardening in stage IV
DEFF Research Database (Denmark)
Pantleon, W.
2005-01-01
statistical reasons still lead to stage III behavior and a saturation of the ow stress, but deterministic contributions to the development of disorienta- tions, as dierences in activated slip systems across boundaries, cause a linear increase of the flow stress at large strains. Such a constant work...
Quantum critical Hall exponents
Lütken, C A
2014-01-01
We investigate a finite size "double scaling" hypothesis using data from an experiment on a quantum Hall system with short range disorder [1-3]. For Hall bars of width w at temperature T the scaling form is w(-mu)T(-kappa), where the critical exponent mu approximate to 0.23 we extract from the data is comparable to the multi-fractal exponent alpha(0) - 2 obtained from the Chalker-Coddington (CC) model [4]. We also use the data to find the approximate location (in the resistivity plane) of seven quantum critical points, all of which closely agree with the predictions derived long ago from the modular symmetry of a toroidal sigma-model with m matter fields [5]. The value nu(8) = 2.60513 ... of the localisation exponent obtained from the m = 8 model is in excellent agreement with the best available numerical value nu(num) = 2.607 +/- 0.004 derived from the CC-model [6]. Existing experimental data appear to favour the m = 9 model, suggesting that the quantum Hall system is not in the same universality class as th...
Temperature Effects on the Tensile Properties of Precipitation-Hardened Al-Mg-Cu-Si Alloys
Directory of Open Access Journals (Sweden)
J.B. Ferguson
2016-02-01
Full Text Available Because the mechanical performance of precipitation-hardened alloys can be significantly altered with temperature changes, understanding and predicting the effects of temperatures on various mechanical properties for these alloys are important. In the present work, an analytical model has been developed to predict the elastic modulus, the yield stress, the failure stress, and the failure strain taking into consideration the effect of temperatures for precipitation-hardenable Al-Mg-Cu-Si Alloys (Al-A319 alloys. In addition, other important mechanical properties of Al-A319 alloys including the strain hardening exponent, the strength coefficient, and the ductility parameter can be estimated using the current model. It is demonstrated that the prediction results based on the proposed model are in good agreement with those obtained experimentally in Al-A319 alloys in the as-cast condition and after W and T7 heat treatments.
Shao, D.; Zhang, P.; Zhang, J. Y.; Liu, G.; Wang, R. H.; Liu, W. Q.; Sha, G.; Sun, J.
2017-09-01
The effect of pre-strain on the solute clustering, mechanical properties, and work-hardening of a naturally aged Al-Cu-Mg alloy was comprehensively investigated using a three-dimensional atom probe, electrical resistivity, and hardness measurements. The pre-strain promoted the rapid formation of solute clusters but suppressed the growth of solute clusters during prolonged aging. An increase in pre-strain caused a decrease in the saturated number density of solute clusters, leading to a reduction in cluster strengthening. By taking into account the coupling effect of solute clusters and pre-existing dislocations, models were proposed to address the yield strength and work-hardening behaviors of the Al-Cu-Mg alloy, respectively. It reveals that the solute-cluster strengthening is comparable to dislocation strengthening in the naturally aged alloy. However, the work hardening is not significantly affected by the presence of the solute clusters. The findings reported in this paper will be helpful for the development of a naturally aged Al-Cu-Mg alloy with improved performance by controlling the pre-strain.
Energy Technology Data Exchange (ETDEWEB)
Esposito, Iara Maria
2006-07-01
The aluminum 6063 alloy possesses a great industrial interest, presenting characteristics that justify its frequent use, when compared to the other aluminum alloys: the precipitation hardening and high cold work capacity. These alloys present high ductility, that allows their use in operations with high deformation degrees, as the cold work. The objective of this work is to show comparative analysis of the hardness Vickers of the commercial aluminum 6063 alloy, after cold work with different area reduction degree and thermal treatment. Considering the frequent utilization aluminium 6063 alloy, this work studies the characterization and recrystallization of this alloy, after the plastic deformation in different area reduction degrees, thermal treatment and convenient treatment times - Thermo mechanic Treatments. (author)
Hardening of shear band in metallic glass
Wang, J.G.; Hu, Y. C.; Guan, P. F.; K. K. Song; Wang, L.; Wang, G.; Pan, Y; Sarac, B.; Eckert, J.
2017-01-01
Strain hardening, originating from defects such as the dislocation, avails conventional metals of high engineering reliability in applications. However, the hardenability of metallic glass is a long-standing concern due to the lack of similar defects. In this work, we carefully examine the stress-strain relationship in three bulk monolithic metallic glasses. The results show that hardening is surely available in metallic glasses if the effective load-bearing area is considered instantly. The ...
Energy Technology Data Exchange (ETDEWEB)
Ma, D.Q. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Jiao, W.T. [College of Education, Hebei Normal University of Science and Technology, Qinhuangdao 066004 (China); Zhang, Y.F. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Vocational and Technical College of Building Materials, Qinhuangdao 066004 (China); Wang, B.A.; Li, J.; Zhang, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ma, M.Z., E-mail: mz550509@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)
2015-03-05
Highlights: • Hardness of dendrite of TiZr-based BMGMCs increases. • Strong work-hardening behavior is obtained after solid solution strengthening. • Lattice distortions of dendrite suffering from rapid cooling are detected. - Abstract: A series of TiZr-based bulk metallic glass matrix composites (BMGMCs) with distinguished mechanical properties are successfully fabricated by adding different volume fractions of Ta (Ti{sub 38.8}Zr{sub 28.8}Cu{sub 6.2}Be{sub 16.2}Nb{sub 10} as the basic composition, denoted as Ta{sub 0.0}–Ta{sub 8.0}). Along with the growth of precipitated phase, typical dendritic morphology is fully developed in the TiZr-based BMGMCs of Ta{sub 8.0}. Energy-dispersive spectrometry analysis of the dendrites and glass matrix indicates that the metallic elements of Nb and Ta should preferentially form solid solution into dendrites. The chaotic structure of high-temperature precipitate phase is trapped down by the rapid cooling of the copper-mould. The detected lattice distortions in the dendrites are attributed to the strong solid solution strengthening of the metallic elements of Ti, Zr, Nb, and Ta. These lattice distortions increase the resistance of the dislocation motion and pin the dislocations, thus the strength and hardness of dendrite increase. Dendrites create a strong barrier for the shear band propagation and generate multiple shear bands after solid solution strengthening, thereby providing the TiZr-based BMGMCs with greatly improved capacity to sustain plastic deformation and resistance to brittle fracture. Thus, the TiZr-based BMGMCs possess distinguished work-hardening capability. Among these TiZr-based BMGMCs, the sample Ta{sub 0.5} possesses the largest plastic strain (ε{sub p}) at 20.3% and ultimate strength (σ{sub max}) of 2613 MPa during compressive loading. In addition, the sample of Ta{sub 0.5} exhibits work-hardening up to an ultrahigh tensile strength of 1680 MPa during the tensile process, and then progressively
Scaling exponents of star polymers
von Ferber, Christian; Holovatch, Yurij
2002-01-01
We review recent results of the field theoretical renormalization group analysis on the scaling properties of star polymers. We give a brief account of how the numerical values of the exponents governing the scaling of star polymers were obtained as well as provide some examples of the phenomena governed by these exponents. In particular we treat the interaction between star polymers in a good solvent, the Brownian motion near absorbing polymers, and diffusion-controlled reactions involving p...
Optimization of processing parameters in induction hardening using ...
Indian Academy of Sciences (India)
surface-hardened bearings, especially the induction-hardened bearings, is not well-established compared to through-hardened .... work piece. The hardness of bar when measured in rolled condition was found to be 205 BHN. (Brinell hardness number) and in normalized condition 197 BHN. This material is suitable for a.
Hardening of shear band in metallic glass.
Wang, J G; Hu, Y C; Guan, P F; Song, K K; Wang, L; Wang, G; Pan, Y; Sarac, B; Eckert, J
2017-08-01
Strain hardening, originating from defects such as the dislocation, avails conventional metals of high engineering reliability in applications. However, the hardenability of metallic glass is a long-standing concern due to the lack of similar defects. In this work, we carefully examine the stress-strain relationship in three bulk monolithic metallic glasses. The results show that hardening is surely available in metallic glasses if the effective load-bearing area is considered instantly. The hardening is proposed to result from the remelting and ensuing solidification of the shear-band material under a hydrostatic pressure imposed by the normal stress during the shear banding event. This applied-pressure quenching densifies the metallic glass by discharging the free volume. On the other hand, as validated by molecular dynamics simulations, the pressure promotes the icosahedral short-range order. The densification and icosahedral clusters both contribute to the increase of the shear strength and therefore the hardening in metallic glasses.
Directory of Open Access Journals (Sweden)
Bokota A.
2015-12-01
Full Text Available In the paper the complex model of hardening of the hot-work tool steel is presented. Model of estimation of phase fractions and their kinetics is based on the continuous heating diagram (CHT and cooling diagram (CCT. Phase fractions which occur during the continuous heating and cooling (austenite, pearlite or bainite are described by Johnson-Mehl (JM formula. To determine of the formed martensite the modified Koistinen-Marburger (KM equation is used. Model takes into account the thermal, structural, plastic strains and transformation plasticity. To calculate the plastic strains the Huber-Mises plasticity condition with isotopic hardening is used. Whereas to determine transformations induced plasticity the Leblond model is applied. The numerical analysis of phase compositions and residual stresses in the hot-work steel (W360 element is considered.
COMPLEX SURFACE HARDENING OF STEEL ARTICLES
Directory of Open Access Journals (Sweden)
A. V. Kovalchuk
2014-01-01
Full Text Available The method of complex surface hardening of steel detailswas designed. The method is a compound of two processes of hardening: chemical heat treatment and physical vapor deposition (PVD of the coating. The result, achieved in this study is much higher, than in other work on this topic and is cumulative. The method designed can be used in mechanical engineering, medicine, energetics and is perspective for military and space technologies.
Energetic model of metal hardening
Directory of Open Access Journals (Sweden)
Ignatova O.N.
2011-01-01
Full Text Available Based on Bailey hypothesis on the link between strain hardening and elastic lattice defect energy this paper suggests a shear strength energetic model that takes into consideration plastic strain intensity and rate as well as softening related to temperature annealing and dislocation annihilation. Metal strain hardening was demonstrated to be determined only by elastic strain energy related to the energy of accumulated defects. It is anticipated that accumulation of the elastic energy of defects is governed by plastic work. The suggested model has a reasonable agreement with the available experimental data for copper up to P = 70 GPa , for aluminum up to P = 10 GPa and for tantalum up to P = 20 GPa.
Energy Technology Data Exchange (ETDEWEB)
Dureja, A.K., E-mail: akdureja@barc.gov.in [Reactor Design and Development Group, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Sinha, S.K. [Reactor Design and Development Group, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Pawaskar, D.N.; Seshu, P. [Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai (India); Chakravartty, J.K. [Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Sinha, R.K. [Department of Atomic Energy, Anushakti-Bhavan, Near Gateway of India, Mumbai (India)
2014-04-01
Under a postulated accident scenario of loss of cooling medium in an Indian Pressurised Heavy Water Reactor (IPHWR), temperature of the pressure tubes can rise and lead to large deformations. In order to investigate the modes of deformation of pressure tube – calandria tube assembly, material property data defining the flow behaviour over a temperature range from room temperature (RT) to 800 {sup o}C are needed. It is of practical importance to formulate mathematical equations to describe the stress–strain relationships of a material for a variety of reasons, such as the analysis of forming operations and the assessment of component's performance in service. A number of constitutive relations of empirical nature have been proposed and they have been found very suitable to describe the behaviour of a material. Although these relations are of empirical nature, various metallurgical factors appear to decide applicability of each of these relations. For example, grain size influences mainly the friction stress while the strain hardening is governed by dislocation density. In a recent work, tensile deformation behaviour of pressure tube material of IPHWR has been carried out over a range of temperature and strain rates (Dureja et al., 2011). It has been found that the strength parameters (yield and ultimate tensile strength) vary along the length of the tube with higher strength at the trailing end as compared to the leading end. This stems from cooling of the billet during the extrusion process which results in the variation of microstructure, texture and dislocation density from the leading to the trailing end. In addition, the variation in metallurgical parameters is also expected to influence the work hardening behaviour, which is known to control the plastic instability (related to uniform strain). In the present investigation, the tensile flow and work-hardening behaviour of a cold worked Zr–2.5Nb pressure tube material of IPHWRs has been studied over
Passive Scalar Scaling Exponents and Realizability
Kraichnan, R H
1997-01-01
Realizability of the statistics of a temperature field passively advected by a rapidly-varying velocity field is a constraint on the possible inertial-range scaling exponents. Further restrictions on exponents follow if the dissipation conditioned on temperature difference is a smooth, monotonic function. Realizability of the so-called linear ansatz is verified numerically, and the form of the associated probability distribution function is computed. Monotonicity of the conditional mean of dissipation can be sensitive to small changes in the exponents.
Lyapunov exponents from geodesic spread in configuration space
Cerruti-Sola, M; Pettini, M; Cerruti-Sola, Monica; Franzosi, Roberto; Pettini, Marco
1997-01-01
The exact form of the Jacobi -- Levi-Civita (JLC) equation for geodesic spread is here explicitly worked out at arbitrary dimension for the configuration space manifold M_E = {q in R^N | V(q) < E} of a standard Hamiltonian system, equipped with the Jacobi (or kinetic energy) metric g_J. As the Hamiltonian flow corresponds to a geodesic flow on (M_E,g_J), the JLC equation can be used to study the degree of instability of the Hamiltonian flow. It is found that the solutions of the JLC equation are closely resembling the solutions of the standard tangent dynamics equation which is used to compute Lyapunov exponents. Therefore the instability exponents obtained through the JLC equation are in perfect quantitative agreement with usual Lyapunov exponents. This work completes a previous investigation that was limited only to two-degrees of freedom systems.
Gaurav, Suraj
2015-01-01
Learn what it takes to build large scale, mission critical applications -hardened applications- on the Azure cloud platform. This 208 page book covers the techniques and engineering principles that every architect and developer needs to know to harden their Azure/.NET applications to ensure maximum reliability and high availability when deployed at scale. While the techniques are implemented in .NET and optimized for Azure, the principles here will also be valuable for users of other cloud-based development platforms. Applications come in a variety of forms, from simple apps that can be bui
Hardened subtidal stromatolites, bahamas.
Dravis, J J
1983-01-28
Hardened, high-relief stromatolites have been discovered along the margins of some Bahamian platforms. They occur in high-energy (tidal) oolitic sand environments in waters ranging in depth from about 1 to 5 meters. Physical stress produced by actively migrating bed forms of oolitic sand appears to exclude grazing gastropods and subsequent community successions, permitting stromatolite growth.
Concrete, hardened: Self desiccation
DEFF Research Database (Denmark)
Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil
1999-01-01
The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...
Prediction errors and local Lyapunov exponents
Kennel, M B; Sidorowich, J J S; Matthew B Kennel; Henry D I Abarbanel
1994-01-01
It is frequently asserted that in a chaotic system two initially close points will separate at an exponential rate governed by the largest global Lyapunov exponent. Local Lyapunov exponents, however, are more directly relevant to predictability. The difference between the local and global Lyapunov exponents, the large variations of local exponents over an attractor, and the saturation of error growth near the size of the attractor---all result in non-exponential scalings in errors at both short and long prediction times, sometimes even obscuring evidence of exponential growth. Failure to observe exponential error scaling cannot rule out deterministic chaos as an explanation. We demonstrate a simple model that quantitatively predicts observed error scaling from the local Lyapunov exponents, for both short and surprisingly long times. We comment on the relevance to atmospheric predictability as studied in the meteorological literature.
Lyapunov Exponents as Functions of a Parameter
Millionshchikov, V. M.
1990-02-01
The author proves the typical nature, in the sense of Baire category, of the upper semicontinuity of the Lyapunov exponents of a family of endomorphisms of a metrized vector bundle, considered as a function of a parameter on which a point of the base of this bundle continuously depends. It is proved that the Lyapunov exponents, as functions of this parameter, belong to the second Baire class. An application of these abstract theorems to the Lyapunov exponents of nonlinear systems of differential equations continuously depending on a parameter is given. Bibliography: 14 titles.
Lyapunov exponent for aging process in induction motor
Bayram, Duygu; Ünnü, Sezen Yıdırım; Şeker, Serhat
2012-09-01
Nonlinear systems like electrical circuits and systems, mechanics, optics and even incidents in nature may pass through various bifurcations and steady states like equilibrium point, periodic, quasi-periodic, chaotic states. Although chaotic phenomena are widely observed in physical systems, it can not be predicted because of the nature of the system. On the other hand, it is known that, chaos is strictly dependent on initial conditions of the system [1-3]. There are several methods in order to define the chaos. Phase portraits, Poincaré maps, Lyapunov Exponents are the most common techniques. Lyapunov Exponents are the theoretical indicator of the chaos, named after the Russian mathematician Aleksandr Lyapunov (1857-1918). Lyapunov Exponents stand for the average exponential divergence or convergence of nearby system states, meaning estimating the quantitive measure of the chaotic attractor. Negative numbers of the exponents stand for a stable system whereas zero stands for quasi-periodic systems. On the other hand, at least if one of the exponents is positive, this situation is an indicator of the chaos. For estimating the exponents, the system should be modeled by differential equation but even in that case mathematical calculation of Lyapunov Exponents are not very practical and evaluation of these values requires a long signal duration [4-7]. For experimental data sets, it is not always possible to acquire the differential equations. There are several different methods in literature for determining the Lyapunov Exponents of the system [4, 5]. Induction motors are the most important tools for many industrial processes because they are cheap, robust, efficient and reliable. In order to have healthy processes in industrial applications, the conditions of the machines should be monitored and the different working conditions should be addressed correctly. To the best of our knowledge, researches related to Lyapunov exponents and electrical motors are mostly
Industrial Hardening Demonstration.
1980-09-01
less severe conditions than thermal cracking (850’ - 950°F and 10 to 20 psi). Zeolitic or molecular sieve- base catalysts are used. Catalytic reforming...with Potential Industrial Hardening A-1 Participants B Post-Attack Petroleum Refining (and Production) B-1 from Crude Oil V List of Figures Number Page...the Key Worker Shelter 116 viii B-1 Proportions of the Products Obtained by Distillation B-2 of Six Crude Oils B-2 Generalized Flow Chart of the
Wisenthal, Adeena; Krupa, Terry; Kirsh, Bonnie H; Lysaght, Rosemary
2018-01-01
Work absences due to depression are prevalent; however, few interventions exist to address the return-to-work challenges following a depressive episode. This mixed-methods study aimed to (a) evaluate the effectiveness of cognitive work hardening in preparing people with depression to return to work and (b) identify key elements of the intervention. A single group ( n = 21) pretest-posttest study design was used incorporating self-report measures (Work Ability Index, Multidimensional Assessment of Fatigue, Beck Depression Inventory II) with interviews at intervention completion and at 3-month follow-up. Descriptive statistics, paired-samples t test, and content analysis were used to analyze the data. Work ability, fatigue, and depression severity significantly improved postintervention. Participants identified structure, work simulations, realism of simulated work environment, support, and education as key intervention elements. Findings underscore an occupationally focused return-to-work intervention for people recovering from depression with potential for wider adoption and future research.
Estimation of Hurst Exponent for the Financial Time Series
Kumar, J.; Manchanda, P.
2009-07-01
Till recently statistical methods and Fourier analysis were employed to study fluctuations in stock markets in general and Indian stock market in particular. However current trend is to apply the concepts of wavelet methodology and Hurst exponent, see for example the work of Manchanda, J. Kumar and Siddiqi, Journal of the Frankline Institute 144 (2007), 613-636 and paper of Cajueiro and B. M. Tabak. Cajueiro and Tabak, Physica A, 2003, have checked the efficiency of emerging markets by computing Hurst component over a time window of 4 years of data. Our goal in the present paper is to understand the dynamics of the Indian stock market. We look for the persistency in the stock market through Hurst exponent and fractal dimension of time series data of BSE 100 and NIFTY 50.
Explicit predictability and dispersion scaling exponents in fully developed turbulence
Energy Technology Data Exchange (ETDEWEB)
Schmitt, Francois G. [CNRS, UMR 8013 ELICO, Wimereux Marine Station, University of Lille 1, 28 av. Foch, 62930 Wimereux (France)]. E-mail: francois.schmitt@univ-lille1.fr
2005-07-25
We apply a simple method to provide explicit expressions for different scaling exponents in intermittent fully developed turbulence, that before were only given through a Legendre transform. This includes predictability exponents for infinitesimal and noninfinitesimal perturbations, Lagrangian velocity exponents, and dispersion exponents. We obtain also new results concerning inverse statistics corresponding to exit-time moments.
Hardened plungers and piston rods for high-pressure compressors
Energy Technology Data Exchange (ETDEWEB)
1942-07-07
This report was a summary of information on dimensions, materials, and operating conditions, as well as experience in the use of piston rods and plungers at Gelsenkirchen. The surface hardening of these parts and their resulting life and wear were of prime importance. Nitriding hardening was one of the best processes for the production of wearproof surfaces. Case hardening and autogeneous hardening had been found satisfactory. Heat hardening had been found to be a cheap process in many applications. Surfaces could be obtained by hard chrome plating which would have the same or higher wear resistance as nitriding and excel in the depth of hardness. However, the heat hardening alone produced hard layers which had sufficiently good properties for plungers and piston rods of the booster compressors, gas-circulation pumps, paste presses, compressors and possibly pressure-release machines. This plant possessed a hardening installation which offered the advantage of production of most of the required equipment right at the works. This was particularly important if a grinding machine was available. This arrangement had to be supplemented with a shaft furnace in which parts could be heated to remove stresses before and after machining. 5 tables.
Nonlinearly charged Lifshitz black holes for any exponent z>1
Energy Technology Data Exchange (ETDEWEB)
Alvarez, Abigail; Ayón-Beato, Eloy [Departamento de Física, CINVESTAV-IPN, A.P. 14-740, 07000, México D.F. (Mexico); Instituto de Ciencias Físicas y Matemáticas, Universidad Austral de Chile,Valdivia (Chile); González, Hernán A. [Physique Théorique et Mathématique,Université Libre de Bruxelles & International Solvay Institutes,Campus Plaine C.P. 231, B-1050 Bruxelles (Belgium); Hassaïne, Mokhtar [Instituto de Matemática y Física, Universidad de Talca,Casilla 747, Talca (Chile)
2014-06-09
Charged Lifshitz black holes for the Einstein-Proca-Maxwell system with a negative cosmological constant in arbitrary dimension D are known only if the dynamical critical exponent is fixed as z=2(D−2). In the present work, we show that these configurations can be extended to much more general charged black holes which in addition exist for any value of the dynamical exponent z>1 by considering a nonlinear electrodynamics instead of the Maxwell theory. More precisely, we introduce a two-parametric nonlinear electrodynamics defined in the more general, but less known, so-called (H,P)-formalism and obtain a family of charged black hole solutions depending on two parameters. We also remark that the value of the dynamical exponent z=D−2 turns out to be critical in the sense that it yields asymptotically Lifshitz black holes with logarithmic decay supported by a particular logarithmic electrodynamics. All these configurations include extremal Lifshitz black holes. Charged topological Lifshitz black holes are also shown to emerge by slightly generalizing the proposed electrodynamics.
System-Level Radiation Hardening
Ladbury, Ray
2014-01-01
Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.
Contact allergy to epoxy hardeners.
Aalto-Korte, Kristiina; Suuronen, Katri; Kuuliala, Outi; Henriks-Eckerman, Maj-Len; Jolanki, Riitta
2014-09-01
Diglycidylether of bisphenol A resin is the most important sensitizer in epoxy systems, but a minority of patients develop concomitant or solitary contact allergy to epoxy hardeners. At the Finnish Institute of Occupational Health, several in-house test substances of epoxy hardeners have been tested in a special epoxy compound patch test series. To analyse the frequency and clinical relevance of allergic reactions to different epoxy hardeners. Test files (January 1991 to March 2013) were screened for contact allergy to different epoxy hardeners, and the clinical records of patients with allergic reactions were analysed for occupation, concomitant allergic reactions, and exposure. The most commonly positive epoxy hardeners were m-xylylenediamine (n = 24), 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP; n = 14), isophorone-diamine (n = 12), and diethylenetriamine (n = 9). Trimethylhexamethylenediamine (n = 7), tetraethylenepentamine (n = 4), and triethylenetetramine (n = 2) elicited some reactions, although most patients were found to have no specific exposure. Allergic reactions to hexamethylenetetramine, dimethylaminopropylamine and ethylenediamine dihydrochloride were not related to epoxy products. Tris-DMP is an important sensitizer in epoxy hardeners, and should be included in the patch test series of epoxy chemicals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Directory of Open Access Journals (Sweden)
Markus Bambach
2016-08-01
Full Text Available The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening initially and exhibits neither a plateau (stage IV hardening nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys.
Beam hardening correction algorithm in microtomography images
Energy Technology Data Exchange (ETDEWEB)
Sales, Erika S.; Lima, Inaya C.B.; Lopes, Ricardo T., E-mail: esales@con.ufrj.b, E-mail: ricardo@lin.ufrj.b [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Instrumentacao Nuclear; Assis, Joaquim T. de, E-mail: joaquim@iprj.uerj.b [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Inst. Politecnico. Dept. de Engenharia Mecanica
2009-07-01
Quantification of mineral density of bone samples is directly related to the attenuation coefficient of bone. The X-rays used in microtomography images are polychromatic and have a moderately broad spectrum of energy, which makes the low-energy X-rays passing through a sample to be absorbed, causing a decrease in the attenuation coefficient and possibly artifacts. This decrease in the attenuation coefficient is due to a process called beam hardening. In this work the beam hardening of microtomography images of vertebrae of Wistar rats subjected to a study of hyperthyroidism was corrected by the method of linearization of the projections. It was discretized using a spectrum in energy, also called the spectrum of Herman. The results without correction for beam hardening showed significant differences in bone volume, which could lead to a possible diagnosis of osteoporosis. But the data with correction showed a decrease in bone volume, but this decrease was not significant in a confidence interval of 95%. (author)
Residual stresses relaxation in surface-hardened half-space under creep conditions
Directory of Open Access Journals (Sweden)
Vladimir P. Radchenko
2015-09-01
Full Text Available We developed the method for solving the problem of residual stresses relaxation in surface-hardened layer of half-space under creep conditions. At the first stage we made the reconstruction of stress-strain state in half-space after plastic surface hardening procedure based on partial information about distribution for one residual stress tensor component experimentally detected. At the second stage using a numerical method we solve the problem of relaxation of self-balanced residual stresses under creep conditions. To solve this problem we introduce the following Cartesian system: x0y plane is aligned with hardened surface of half-space and 0z axis is directed to the depth of hardened layer. We also introduce the hypotheses of plane sections parallel to x0z and y0z planes. Detailed analysis of the problem has been done. Comparison of the calculated data with the corresponding test data was made for plane specimens (rectangular parallelepipeds made of EP742 alloy during T=650°C after the ultrasonic hardening with four hardening modes. We use half-space to model these specimens because penetration's depth of residual stresses is less than specimen general size in two digit exponent. There is enough correspondence of experimental and calculated data. It is shown that there is a decay (in modulus of pressing residual stresses under creep in 1.4–1.6 times.
Lexical exponents of hypothetical modality in Polish and Lithuanian
Roman Roszko
2015-01-01
Lexical exponents of hypothetical modality in Polish and Lithuanian The article focuses on the lexical exponents of hypothetical modality in Polish and Lithuanian. The purpose for comparing and contrasting the lexical exponents of hypothetical modality is not only to identify all the lexemes in both languages but also find the answer to the following question: whether the morphological exponents of hypothetical modality (so-called modus relativus) familiar to the Lithuanian language have/...
Nonlinearity exponents in lightly doped conducting polymers
Talukdar, D.; Nandi, U. N.; Bardhan, K. K.; Bof Bufon, C. C.; Heinzel, T.; de, A.; Mukherjee, C. D.
2011-08-01
The I-V characteristics of four conducting polymer systems such as doped polypyrrole, poly(3,4-ethylenedioxythiophene), polydiacetylene, and polyaniline in as many physical forms have been investigated at different temperatures, quenched disorder, and magnetic fields. Transport data clearly show the existence of a single electric-field scale in each system. Based upon this observation, a phenomenological scaling analysis is performed, leading to the extraction of a numerical value for a nonlinearity exponent called xM which serves to characterize a set of I-V curves. The conductivity starts deviating from an Ohmic value σ0 above an onset electric field Fo which scales according to Fo˜σ0xM. The electric-field-dependent data are shown to be described by the multistep tunneling model of Glazman-Matveev [JETP 67, 1276 (1988)] in a near-perfect manner over nine orders of magnitude in conductivity and five orders of magnitude in electric field. Furthermore, xM is found to possess both positive and negative values lying between -1/2 and 3/4. There is no theory at present for this exponent. Some issues concerning applicability of the Glatzman-Matveev model are discussed.
Hot tensile properties and strain hardening behaviour of Super 304HCu stainless steel
Directory of Open Access Journals (Sweden)
M. Vinoth Kumar
2017-04-01
Full Text Available Super 304HCu austenitic stainless steel containing 2.3–3 (wt.% of Cu is mainly used in superheaters and reheaters tubing of ultra super critical boilers which operates over 600 °C of steam temperature. Tensile tests were carried out on Super 304HCu, using nominal strain rate of 1 × 10−3 s−1, at room temperature, 550 °C, 600 °C and 650 °C. The tensile strength and elongation were found to decrease with increase in test temperature. The stress strain curves were fitted using Hollomon equation to determine the strain hardening exponent value. Differential Crussard–Jaoul (C–J analysis of the tensile curve is used to determine the variation in strain hardening exponent. Kocks–Mecking (K–M type plots were used to determine the stages of strain hardening during tensile loading of the specimen. The strain hardening capacity of the Super 304HCu is found to decrease with increase in test temperature.
Influence of degree of deformation in rolling on anneal hardening ...
Indian Academy of Sciences (India)
Unknown
increase in the electrical conductivity. The amount of strengthening increases with increasing degree of prior cold work. The X-ray analysis shows a change in the lattice parameter during annealing when anneal hardening effect was observed. ... The strength properties of cold-worked substitutional solid solutions increased ...
Onycholysis induced by nail hardener.
Helsing, Per; Austad, Joar; Talberg, Hans Jørgen
2007-10-01
Nail hardeners appeared in the market during the 1960s. They were basically solutions of formaldehyde. The first adverse effects were published in 1966 (1). Reactions were onycholysis, chromonychia, subungual haemorrhage, and hyperkeratosis. Onycholysis may be non-inflammatory or inflammatory, and is accompanied by throbbing pain. Inflammatory reactions are followed by paronychia and occasional dermatitis on the digital pulpa.
Non-trivial rheological exponents in sheared yield stress fluids.
Agoritsas, Elisabeth; Martens, Kirsten
2017-07-14
In this work we discuss possible physical origins of non-trivial exponents in the athermal rheology of soft materials at low but finite driving rates. A key ingredient in our scenario is the presence of a self-consistent mechanical noise that stems from the spatial superposition of long-range elastic responses to localized plastically deforming regions. We study analytically a mean-field model, in which this mechanical noise is accounted for by a stress diffusion term coupled to the plastic activity. Within this description we show how a dependence of the shear modulus and/or the local relaxation time on the shear rate introduces corrections to the usual mean-field prediction, concerning the Herschel-Bulkley-type rheological response of exponent 1/2. This feature of the mean-field picture is then shown to be robust with respect to structural disorder and partial relaxation of the local stress. We test this prediction numerically on a mesoscopic lattice model that implements explicitly the long-range elastic response to localized shear transformations, and we conclude on how our scenario might be tested in rheological experiments.
Laser surface hardening for cam shaft
Zhang, Dongyun; Zhang, Hongtao; Wang, Chunshan; Yan, Shi; Lu, Boliang; Xu, Chunying; Zhang, Jibin
1998-08-01
The paper introduces the laser surface hardening processing with 5 KW CNC CO2 laser for Cam Shaft made of 45 steel. The results show that spiral scanning matching with adaptable technological parameters and water cooling achieve remarkable hardenability with less deformation, which satisfy the requirements demanded by manufacturer, simplify the manufacturing technology. The advantage of laser surface hardening is very remarkable.
Process design of press hardening with gradient material property influence
Neugebauer, R.; Schieck, F.; Rautenstrauch, A.
2011-05-01
Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.
Kinematic hardening in creep of Zircaloy
Energy Technology Data Exchange (ETDEWEB)
Sedláček, Radan, E-mail: radan.sedlacek@areva.com; Deuble, Dietmar
2016-10-15
Results of biaxial creep tests with stress changes on Zircaloy-2 tube samples are presented. A Hollomon-type viscoplastic strain hardening model is extended by the Armstrong-Frederic nonlinear kinematic hardening law, resulting in a mixed (i.e. isotropic and kinematic) strain hardening model. The creep tests with stress changes and similar tests published in the literature are simulated by the models. It is shown that introduction of the kinematic strain hardening in the viscoplastic strain hardening model is sufficient to describe the creep transients following stress drops, stress reversals and stress removals.
Occupational respiratory and skin sensitization caused by polyfunctional aziridine hardener.
Kanerva, L; Keskinen, H; Autio, P; Estlander, T; Tuppurainen, M; Jolanki, R
1995-05-01
Polyfunctional aziridine (PFA) is increasingly used as a water-based crosslinker in two-component paints, paint primers, lacquers, topcoats and other protective coatings. The crosslinker is made by reacting multifunctional acrylic monomer with a highly reactive aziridine compound. Respiratory allergy or hypersensitivity from PFA has not been reported previously. During 1978-1991 we came across nine cases with hypersensitivity from PFA: two had allergic contact dermatitis (ACD), four had occupational asthma and three had both of them. Five of the patients were parquet layers, two were fibreboard painters, one was a spray painter and one was a salesman of PFA products. ACD was diagnosed by positive allergic patch test reactions with PFA in a dilution series in petrolatum: 0.32%-0.5% gave a 2(+)-3+ allergic reaction in the five cases with ACD but 0.1% gave only a weak reaction in one case, whereas the methacrylate patch test series was negative. The diagnosis of seven cases of occupational asthma due to PFA hardener was based on symptoms related to exposure to PFA hardener at work, and on positive provocation tests with PFA hardener. One had an immediate type reaction, one a had a dual reaction, and the others had late reactions. The positive reactions with the PFA hardener and the negative reactions with the acrylate compounds indicate that PFA caused ACD which is different from the previous reports in which acrylates present as impurities in the PFA hardener caused the sensitization.(ABSTRACT TRUNCATED AT 250 WORDS)
General Friction Model Extended by the Effect of Strain Hardening
DEFF Research Database (Denmark)
Nielsen, Chris V.; Martins, Paulo A.F.; Bay, Niels
2016-01-01
contact area as function of the normalized contact pressure is based on slip-line analysis and hence on the assumption of rigid-ideally plastic material behavior. In the present work, a general finite element model is established to, firstly, reproduce the original model under the assumption of rigid......-ideally plastic material, and secondly, to extend the solution by the influence of material strain hardening. This corresponds to adding a new variable and, therefore, a new axis to the general friction model. The resulting model is presented in a combined function suitable for e.g. finite element modeling...... of friction in metal forming, where the material generally strain hardens. The extension of the model to cover strain hardening materials is validated by comparison to previously published experimental data....
Skeleton graph expansion of critical exponents in "cultural revolution" years
Hao, Bailin
Kenneth Wilson's Nobel Prize winning breakthrough in the renormalization group theory of phase transition and critical phenomena almost overlapped with the violent "cultural revolution" years (1966-1976) in China. An unexpected chance in 1972 brought the author of these lines close to the Wilson-Fisher є-expansion of critical exponents and eventually led to a joint paper with Lu Yu published entirely in Chinese without any English title and abstract. Even the original acknowledgment was deleted because of mentioning foreign names like Kenneth Wilson and Kerson Huang. In this article I will tell the 40-year old story as a much belated tribute to Kenneth Wilson and to reproduce the essence of our work in English. At the end, I give an elementary derivation of the Callan-Symanzik equation without referring to field theory.
Scintillation-Hardened GPS Receiver
Stephens, Donald R.
2015-01-01
CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.
Decorative application of strain-hardening cementitious composites
Ibrovic, V.; Lukovic, M.; Schlangen, E.
2014-01-01
Strain hardening cementitious composites (SHCC) have been used in variety of structural applications. Apart from this, they are also suitable for non-structural applications. In this work, the application of SHCC for producing cover plates for light switches and power sockets is presented. For
Radiation hardening of diagnostics
Siemon, R. E.
The world fusion program has advanced to the stage where it is appropriate to construct a number of devices for the purpose of burning DT fuel. In these next-generation experiments, the expected flux and fluence of 14 MeV neutrons and associated gamma rays will pose a significant challenge to the operation and diagnostics of the fusion device. Radiation effects include structural damage to materials such as vacuum windows and seals, modifications to electrical properties such as electrical conductivity and dielectric strength and impaired optical properties such as reduced transparency and luminescence of windows and fiber optics during irradiation. In preparation for construction and operation of these new facilities, the fusion diagnostics community needs to work with materials scientists to develop a better understanding of radiation effects, and to undertake a testing program aimed at developing workable solutions for this multi-faceted problem. A unique facility to help in this regard is the Los Alamos Spallation Radiation Effects Facility, a neutron source located at the beam stop of the world's most powerful accelerator, the Los Alamos Meson Physics Facility (LAMPF). The LAMPF proton beam generates 10(exp 16) neutrons per second because of spallation'reactions when the protons collide with the copper nuclei in the beam stop.
Rescattering effects and intermittent exponents in nucleus-nucleus interactions
Energy Technology Data Exchange (ETDEWEB)
Pajares, C. (Universidad de Santiago de Compostela (Spain). Dept. de Particulas Elementales)
1991-04-11
It is shown that the rescattering in nucleus-nucleus collisions provides a natural branching mechanism which explains the dependence of the intermittent exponents on the energy, projectile and target. The possibility of finding some new coherent phenomena by studying the dependence of the intermittent exponents on the number of collisions is discussed. (orig.).
Effects of length fluctuations on the viscosity exponent in the necklace model
Energy Technology Data Exchange (ETDEWEB)
Aldao, C M [Institute of Materials Science and Technology (INTEMA), Universidad Nacional de Mar del Plata-CONICET, Juan B Justo 4302, B7608FDQ Mar del Plata (Argentina); Terranova, G R; Martin, H O [Physics Department, School of Exact and Natural Sciences, Universidad Nacional de Mar del Plata, Dean Funes 3350, B7602AYL Mar del Plata (Argentina)
2009-04-24
It is commonly accepted that contour length fluctuations increase the viscosity exponent for chains that diffuse by reptation. We found that length fluctuations in the necklace model can play an unexpected role as they can also decrease this exponent. A detailed analysis of the interplay between the discrete character of the model and how the fluctuations take place is presented in this work. Basically, we found that when fluctuations are symmetric their influence is the expected one; when fluctuations are not symmetric new effects can appear.
An Isomorphism between Lyapunov Exponents and Shannon's Channel Capacity
Energy Technology Data Exchange (ETDEWEB)
Friedland, Gerald [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Metere, Alfredo [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2017-06-07
We demonstrate that discrete Lyapunov exponents are isomorphic to numeric overflows of the capacity of an arbitrary noiseless and memoryless channel in a Shannon communication model with feedback. The isomorphism allows the understanding of Lyapunov exponents in terms of Information Theory, rather than the traditional definitions in chaos theory. The result also implies alternative approaches to the calculation of related quantities, such as the Kolmogorov Sinai entropy which has been linked to thermodynamic entropy. This work provides a bridge between fundamental physics and information theory. It suggests, among other things, that machine learning and other information theory methods can be employed at the core of physics simulations.
Lyapunov Exponents for the Intermittent Transition to Chaos
Hanssen, J; Hanssen, James; Wilcox, Walter
1998-01-01
The dependence of the Lyapunov exponent on the closeness parameter, illustrate two averaging procedures for defining Lyapunov exponents in such systems. First, we develop theoretical expressions for an isolated tangency channel in which the Lyapunov exponent is defined on single channel passes. Numerical simulations were done to compare theory to measurement across a range of $\\epsilon$ values. Next, as an illustration of defining the Lyapunov exponent on many channel passes, a simulation of the intermittent transition in the logistic map is described. The modified theory for the channels is explained and a simple model for the gate entrance rates is constructed. An important correction due to the discrete nature of the iterative flow is identified and incorporated in an improved model. Realistic fits to the data were made for the Lyapunov exponents from the logistic gate and from the full simulation. A number of additional corrections which could improve the treatment of the gates are identified and briefly ...
Compactness results for quasilinear problems with variable exponent on the whole space
Directory of Open Access Journals (Sweden)
Olfa Allegue
2011-07-01
Full Text Available In this work we give a compactness result which allows us to prove the point-wise convergence of the gradients of a sequence of solutions to a quasilinear inequality and for an arbitrary open set. This result suggests solutions to many problems, notably nonlinear elliptic problems with critical exponent.
Radiation Hardened Electronics for Extreme Environments
Keys, Andrew S.; Watson, Michael D.
2007-01-01
The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.
Allometric exponents do not support a universal metabolic allometry.
White, Craig R; Cassey, Phillip; Blackburn, Tim M
2007-02-01
The debate about the value of the allometric scaling exponent (b) relating metabolic rate to body mass (metabolic rate = a x mass(b)) is ongoing, with published evidence both for and against a 3/4-power scaling law continuing to accumulate. However, this debate often revolves around a dichotomous distinction between the 3/4-power exponent predicted by recent models of nutrient distribution networks and a 2/3 exponent predicted by Euclidean surface-area-to-volume considerations. Such an approach does not allow for the possibility that there is no single "true" exponent. In the present study, we conduct a meta-analysis of 127 interspecific allometric exponents to determine whether there is a universal metabolic allometry or if there are systematic differences between taxa or between metabolic states. This analysis shows that the effect size of mass on metabolic rate is significantly heterogeneous and that, on average, the effect of mass on metabolic rate is stronger for endotherms than for ectotherms. Significant differences between scaling exponents were also identified between ectotherms and endotherms, as well as between metabolic states (e.g., rest, field, and exercise), a result that applies to b values estimated by ordinary least squares, reduced major axis, and phylogenetically correct regression models. The lack of support for a single exponent model suggests that there is no universal metabolic allometry and represents a significant challenge to any model that predicts only a single value of b.
Geometric critical exponents in classical and quantum phase transitions.
Kumar, Prashant; Sarkar, Tapobrata
2014-10-01
We define geometric critical exponents for systems that undergo continuous second-order classical and quantum phase transitions. These relate scalar quantities on the information theoretic parameter manifolds of such systems, near criticality. We calculate these exponents by approximating the metric and thereby solving geodesic equations analytically, near curvature singularities of two-dimensional parameter manifolds. The critical exponents are seen to be the same for both classical and quantum systems that we consider, and we provide evidence about the possible universality of our results.
Development of a Press-Hardened Steel Suitable for Thin Slab Direct Rolling Processing
Lee, Jewoong; De Cooman, Bruno C.
2015-01-01
The thin slab casting and direct rolling process is a hot-rolled strip production method which has maintained commercial quality steel grades as a major material in many industrial applications due to its low processing cost. Few innovative products have however been developed specifically for production by thin slab direct rolling. Press hardening or hot press forming steel grades which are now widely used to produce structural automotive steel parts requiring ultra-high strength and formability may however offer an opportunity for thin slab direct rolling-specific ultra-high strength products. In this work, a newly designed press hardening steel grade developed specifically for thin slab direct rolling processing is presented. The press hardening steel has a high nitrogen content compared with press hardening steel grades produced by conventional steelmaking routes. Boron and titanium which are key alloying additions in conventional press hardening steel such as the 22MnB5 press hardening steel grade are not utilized. Cr is added in the press hardening steel to obtain the required hardenability. The properties of the new thin slab direct rolling-specific 22MnCrN5 press hardening steel grade are reviewed. The evolution of the microstructure and mechanical properties with increasing amounts of Cr additions from 0.6 to 1.4 wt pct and the effect of the cooling rate during die-quenching were studied by means of laboratory simulations. The selection of the optimum chemical composition range for the thin slab direct rolling-specific 22MnCrN5 steel in press hardening heat treatment conditions is discussed.
Investigation of a Hardened Cement Paste Grout
DEFF Research Database (Denmark)
Esteves, Luis Pedro; Sørensen, Eigil Verner
This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....
On some properties of the discrete Lyapunov exponent
Energy Technology Data Exchange (ETDEWEB)
Amigo, Jose M. [Centro de Investigacion Operativa, Universidad Miguel Hernandez Avda. de la Universidad s/n. 03202 Elche (Spain)], E-mail: jm.amigo@umh.es; Kocarev, Ljupco [Macedonian Academy of Sciences and Arts, Skopje (Macedonia, The Former Yugoslav Republic of); Institute for Nonlinear Science, University of California San Diego, 9500 Gilman Drive. La Jolla, CA 92093-0402 (United States)], E-mail: lkocarev@ucsd.edu; Szczepanski, Janusz [Institute of Fundamental Technological Research, Polish Academy of Sciences, Swietokrzyska 21, 00-049 Warsaw, and Kazimierz Wielki University in Bydgoszcz (Poland)], E-mail: jszczepa@ippt.gov.pl
2008-10-06
One of the possible by-products of discrete chaos is the application of its tools, in particular of the discrete Lyapunov exponent, to cryptography. In this Letter we explore this question in a very general setting.
A MONTE-CARLO METHOD FOR ESTIMATING THE CORRELATION EXPONENT
MIKOSCH, T; WANG, QA
We propose a Monte Carlo method for estimating the correlation exponent of a stationary ergodic sequence. The estimator can be considered as a bootstrap version of the classical Hill estimator. A simulation study shows that the method yields reasonable estimates.
Design Features of Hardening Turners with Outstripping Plastic Deformation
Directory of Open Access Journals (Sweden)
V. M. Yaroslavtsev
2014-01-01
Full Text Available An efficiency of the cutting method with outstripping plastic deformation (OPD in lathe works is defined in many respects by design features of the add-on devices for mechanical hardening of a cut-off layer material in the course of cutting. Applied on lathes, deforming OPD devices can have differing dimensions, placement on the lathe, drive type (manual, electric, hydraulic, pneumatic, pneumohydraulic, electromagnetic, and autonomy degree towards the metalcutting equipment and industrial equipment.At the same time there are a number of inherent design features of work-hardening devices the modernized lathes with OPD use for machining. Now the OPD standard devices implement two principle construction options: loading device is placed on the machine or on the OPD slide support separate of the tool, or it is structurally aligned with the cutting tool. In the latter case the OPD device for turning is called a tool mandrel, which is mounted in a tool post of the machine or, at large dimensions, such a mandrel is mounted on the machine instead of the tool mandrel.When designing the OPD devices, is important to take into consideration production requirements and recommendations for the technological equipment, developed in the course of creation, working off and introduction of such installations for mechanical hardening of material. In compliance with it, OPD devices, their placement on the machine, and working displacements shouldn't limit technological capabilities of the applied metal-cutting equipment. OPD stresses have to be smoothly regulated, with maximum loads being limited to admissible values for the machine model to be modernized. It is necessary to ensure synchronized longitudinal and cross displacements of the cutting tool and OPD hardener with respect to the axis of billet rotation to enable regulation and readjustment of the hardener and tool placement. It ought to foresee the increased mobile components rigidity and manufacturing
Elasto-plastic hardening models adjustment to ferritic, austenitic and austenoferritic Rebar
Directory of Open Access Journals (Sweden)
Beatriz Hortigón
2017-05-01
Full Text Available The elastoplastic behaviour of steel used for structural member fabrication has received attention to facilitate a mechanical-resistant design. New Zealand and South African standards have adopted various theoretical approaches to describe such behaviour in stainless steels. With respect to the building industry, describing the tensile behaviour of steel rebar used to produce reinforced concrete structures is of interest. Differences compared with the homogenous material described in the above mentioned standards and related literatures are discussed in this paper. Specifically, the presence of ribs and the TEMPCORE® technology used to produce carbon steel rebar may alter the elastoplastic model. Carbon steel rebar is shown to fit a Hollomon model giving hardening exponent values on the order of 0.17. Austenitic stainless steel rebar behaviour is better described using a modified Rasmussen model with a free fitted exponent of 6. Duplex stainless steel shows a poor fit to any previous model.
Equifinality and the Scaling Exponent of the Structure Function
Fitton, G. F.; Mezematy, Y.; Schertzer, D. J. M.; Tchiguirinskaia, I.
2014-12-01
In turbulence the structure function is by far the most widely used tool for the empirical analysis of the velocity field. This is due mainly to the work of Kolmogorov (1941) who hypothesised a homogeneous flux of energy and derived the famous 2/3 power law for the second-order structure function; — which corresponds to a 5/3 law for the energy spectrum (Obukhov, 1942). In 1962 Kolmogorov refined his hypothesis to take into account the intermittency of the flux, with the consequence that the exponent ξ(q) of the structure function is not longer proportional to its statistical order q. In this communication, we first show that the refined hypothesis can lead to different models that can have opposite intermittency corrections. Secondly, we demonstrate that the inverse problem, i.e., starting from a given expression of ξ(q) to recover the involved flux leads to an interesting problem of equifinality for the definition of this flux. This is done in particular in the framework of the Fractionally Integrated Flux model that gives a precise meaning to the refined hypothesis. The theoretical and practical consequences are illustrated with the help data analysis and simulations of turbulence in wind farms and urban lakes.
Regularized semiclassical limits: Linear flows with infinite Lyapunov exponents
Athanassoulis, Agissilaos
2016-08-30
Semiclassical asymptotics for Schrödinger equations with non-smooth potentials give rise to ill-posed formal semiclassical limits. These problems have attracted a lot of attention in the last few years, as a proxy for the treatment of eigenvalue crossings, i.e. general systems. It has recently been shown that the semiclassical limit for conical singularities is in fact well-posed, as long as the Wigner measure (WM) stays away from singular saddle points. In this work we develop a family of refined semiclassical estimates, and use them to derive regularized transport equations for saddle points with infinite Lyapunov exponents, extending the aforementioned recent results. In the process we answer a related question posed by P.L. Lions and T. Paul in 1993. If we consider more singular potentials, our rigorous estimates break down. To investigate whether conical saddle points, such as -|x|, admit a regularized transport asymptotic approximation, we employ a numerical solver based on posteriori error control. Thus rigorous upper bounds for the asymptotic error in concrete problems are generated. In particular, specific phenomena which render invalid any regularized transport for -|x| are identified and quantified. In that sense our rigorous results are sharp. Finally, we use our findings to formulate a precise conjecture for the condition under which conical saddle points admit a regularized transport solution for the WM. © 2016 International Press.
Coherent light absorbing by concrete during its hardening
Gorsky, Mykhaylo P.; Maksimyak, Peter P.
2018-01-01
In this work changes of concrete reflection coefficient during its hydration were investigated theoretically and experimentally. Diffuse approximation method for concrete light-scattering description during hydration was used and its results were compared with received experimental data. Calculation of scattered and absorption sections for set of particles is described in details. Introduced optical diagnostics method allows performing earlier hydration stages diagnostics of concrete hardening process in comparison with other methods and predicting mechanical properties of produced concrete.
Investigation on microstructural evolution and hardening mechanism in dilute Zr–Nb binary alloys
Energy Technology Data Exchange (ETDEWEB)
Yang, H.L., E-mail: yanghuilong@tokai.t.u-tokyo.ac.jp [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Matsukawa, Y. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Kano, S. [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Duan, Z.G. [Graduate School of Engineering, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Murakami, K. [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Abe, H. [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)
2016-12-01
In this study, the microstructural changes induced by doping of Nb in Zr were investigated by the combined utilization of electron backscatter diffraction and electron transmission microscopy techniques, followed by the correlated hardening mechanism being elucidated based on the obtained microstructural parameters. Microstructural characterization results revealed that microstructural changes caused by doping of Nb in Zr were mainly embodied via two aspects: reducing the matrix α-Zr grain size and increasing the amount of β-Nb particles. β-phase stabilizing effect, dragging effect and pinning effect introduced and enhanced by Nb addition, worked together to significantly reduce the grain size in Zr–Nb alloys. β-Nb particles were firstly observed in Zr0.5Nb specimen with the fairly low number density of ∼2.0 × 10{sup 18}/m{sup 3}, then this value explosively increased to ∼3.3 × 10{sup 20}/m{sup 3} for Zr2Nb specimen. In addition, hardness was increased with an increase in the Nb content. The hardening contributions from solid solution hardening, grain boundary hardening and precipitation hardening were quantitatively estimated as per the obtained microstructural parameters. Results inferred that solid solution hardening contributed the majority when the Nb atoms were solid dissolved (≤0.5 wt%), whereas the precipitation hardening surpassed any other factors when the β-Nb particles were steadily precipitated (≥1 wt%).
Directory of Open Access Journals (Sweden)
K. Major-Gabryś
2012-01-01
Full Text Available The article takes into consideration the researches concerning inserting the Glassex additive to the microwaved-hardened and self- hardened moulding sands with water glass. In the research different types of ester hardeners to self-hardened moulding sands with water glass were used. The influence of Glassex additive on retained strength of moulding sands with different hardeners and prepared by different technologies of hardening were tested. The influence of different hardeners and the technology of hardening on retained strength of moulding sand with water glass and the Glassex additive were also estimated.
Laser Surface Hardening of Groove Edges
Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.
2013-06-01
Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.
Lyapunov exponent for pure and random Fibonacci chains
Velhinho, M. T.; Pimentel, I. R.
2000-01-01
We study the Lyapunov exponent for electron and phonon excitations, in pure and random Fibonacci quasicrystal chains, using an exact real-space renormalization-group method, which allows the calculation of the Lyapunov exponent as a function of the energy. It is shown that the Lyapunov exponent on a pure Fibonacci chain has a self-similar structure, characterized by a scaling index that is independent of the energy for the electron excitations, ``diagonal'' or ``off-diagonal'' quasiperiodic, but is a function of the energy for the phonon excitations. This scaling behavior implies the vanishing of the Lyapunov exponent for the states on the spectrum, and hence the absence of localization on the Fibonacci chain, for the various excitations considered. It is also shown that disordered Fibonacci chains, with random tiling that introduces phason flips at certain sites on the chain, exhibit the same Lyapunov exponent as the pure Fibonacci chain, and hence this type of disorder is irrelevant, either in the case of electron or phonon excitations.
Critical exponents from AdS/CFT with flavor
Karch, Andreas; O'Bannon, Andy; Yaffe, Laurence G.
2009-09-01
We use the AdS/CFT correspondence to study the thermodynamics of massive Script N = 2 supersymmetric hypermultiplet flavor fields coupled to Script N = 4 supersymmetric SU(Nc) Yang-Mills theory, formulated on curved four-manifolds, in the limits of large Nc and large 't Hooft coupling. The gravitational duals are probe D-branes in global thermal AdS. These D-branes may undergo a topology-changing transition in the bulk. The D-brane embeddings near the point of the topology change exhibit a scaling symmetry. The associated scaling exponents can be either real- or complex-valued. Which regime applies depends on the dimensionality of a collapsing submanifold in the critical embedding. When the scaling exponents are complex-valued, a first-order transition associated with the flavor fields appears in the dual field theory. Real scaling exponents are expected to be associated with a continuous transition in the dual field theory. For one example with real exponents, the D7-brane, we study the transition in detail. We find two field theory observables that diverge at the critical point, and we compute the associated critical exponents. We also present analytic and numerical evidence that the transition expresses itself in the meson spectrum as a non-analyticity at the critical point. We argue that the transition we study is a true phase transition only when the 't Hooft coupling is strictly infinite.
A Novel Heat Treatment Process for Surface Hardening of Steel: Metal Melt Surface Hardening
Fu, Yong-sheng; Zhang, Wei; Xu, Xiaowei; Li, Jiehua; Li, Jun; Xia, Mingxu; Li, Jianguo
2017-09-01
A novel heat treatment process for surface hardening of steel has been demonstrated and named as "metal melt surface hardening (MMSH)." A surface layer with a thickness of about 400 μm and a hardness of about 700 HV has been achieved by ejecting AISI 304 stainless steel melt at a temperature of about 1783 K (1510 °C) onto the 40Cr steel surface. This proposed MMSH provides a very promising application for surface hardening of steel.
Anisotropies in magnetic field evolution and local Lyapunov exponents
Energy Technology Data Exchange (ETDEWEB)
Tang, X.Z.; Boozer, A.H.
2000-01-13
The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates.
OBSERVING LYAPUNOV EXPONENTS OF INFINITE-DIMENSIONAL DYNAMICAL SYSTEMS.
Ott, William; Rivas, Mauricio A; West, James
2015-12-01
Can Lyapunov exponents of infinite-dimensional dynamical systems be observed by projecting the dynamics into ℝ (N) using a 'typical' nonlinear projection map? We answer this question affirmatively by developing embedding theorems for compact invariant sets associated with C(1) maps on Hilbert spaces. Examples of such discrete-time dynamical systems include time-T maps and Poincaré return maps generated by the solution semigroups of evolution partial differential equations. We make every effort to place hypotheses on the projected dynamics rather than on the underlying infinite-dimensional dynamical system. In so doing, we adopt an empirical approach and formulate checkable conditions under which a Lyapunov exponent computed from experimental data will be a Lyapunov exponent of the infinite-dimensional dynamical system under study (provided the nonlinear projection map producing the data is typical in the sense of prevalence).
Alloy solution hardening with solute pairs
Mitchell, John W.
1976-08-24
Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.
De Angelis, Fabio; Cancellara, Donato; Grassia, Luigi; D'Amore, Alberto
2018-01-01
In this paper the influence of increasing loading rates on hardening effects is analyzed for rate-dependent elastoplastic materials. The effects of different loading rates on hardening rules are discussed with regard to the constitutive behavior of strain-hardening materials in elasto/viscoplasticity. A suitable procedure for the numerical simulation of rate-sensitive material behavior is illustrated. A comparative analysis is presented on constitutive relations in strain-hardening plasticity without rate effects and with rate effects in order to show the different role played by hardening rules in the rate-sensitivity analysis of elasto/viscoplastic strain-hardening materials. By reporting suitable numerical simulations for the adopted constitutive relations it is shown that when the rate of application of the loading is increased the influence of hardening has a different effect in the mechanical behavior of structures. Computational results and applications are finally illustrated in order to show numerically the different role played by hardening on the plastic strains when the loading rates are incremented for elasto/viscoplastic strain-hardening materials and structures.
Decline in Radiation Hardened Microcircuit Infrastructure
LaBel, Kenneth A.
2015-01-01
Two areas of radiation hardened microcircuit infrastructure will be discussed: 1) The availability and performance of radiation hardened microcircuits, and, and 2) The access to radiation test facilities primarily for proton single event effects (SEE) testing. Other areas not discussed, but are a concern include: The challenge for maintaining radiation effects tool access for assurance purposes, and, the access to radiation test facilities primarily for heavy ion single event effects (SEE) testing. Status and implications will be discussed for each area.
Estimation of radiation hardening in ferritic steels using the cluster dynamics models
Energy Technology Data Exchange (ETDEWEB)
Kwon, Jun Hyun; Kim, Whung Whoe; Hong, Jun Hwa [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
2005-07-01
Evolution of microstructure under irradiation brings about the mechanical property changes of materials, of which the major concern is radiation hardening in this work. Radiation hardening is generally expressed in terms of an increase in yield strength as a function of radiation dose and temperature. Cluster dynamics model for radiation hardening has been developed to describe the evolution of point defects clusters (PDCs) and copperrich precipitates (CRPs). While the mathematical models developed by Stoller focus on the evolution of PDCs in ferritic steels under neutron irradiation, we slightly modify the model by including the CRP growth and estimate the magnitude of hardening induced by PDC and CRP. The model is then used to calculate the changes in yield strength of RPV steels. The calculation results are compared to measured yield strength values, obtained from surveillance testing of PWR vessel steels in France.
Press hardening of alternative high strength aluminium and ultra-high strength steels
Mendiguren, Joseba; Ortubay, Rafael; Agirretxe, Xabier; Galdos, Lander; de Argandoña, Eneko Sáenz
2016-10-01
The boron steel press hardening process takes more and more importance on the body in white structure in the last decade. In this work, the advantages of using alternative alloys on the press hardening process is analysed. In particular, the press hardening of AA7075 high strength aluminium and CP800 complex phase ultra-high strength steel is analysed. The objective is to analyse the potential decrease on springback while taking into account the strength change associated with the microstructural modification carried out during the press hardening process. The results show a clear improvement of the final springback in both cases. Regarding the final mechanical properties, an important decrease has been measured in the AA7075 due to the process while an important increase has been found in the CP800 material.
Simulating the influence of scatter and beam hardening in dimensional computed tomography
Lifton, J. J.; Carmignato, S.
2017-10-01
Cone-beam x-ray computed tomography (XCT) is a radiographic scanning technique that allows the non-destructive dimensional measurement of an object’s internal and external features. XCT measurements are influenced by a number of different factors that are poorly understood. This work investigates how non-linear x-ray attenuation caused by beam hardening and scatter influences XCT-based dimensional measurements through the use of simulated data. For the measurement task considered, both scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, only beam hardening is found to influence dimensional measurements when evaluated using an advanced surface determination method. Based on the results presented, recommendations on the use of beam hardening and scatter correction for dimensional XCT are given.
Universal exponent for transport in mixed Hamiltonian dynamics
Alus, Or; Fishman, Shmuel; Meiss, James D.
2017-09-01
We compute universal distributions for the transition probabilities of a Markov model for transport in the mixed phase space of area-preserving maps and verify that the survival probability distribution for trajectories near an infinite island-around-island hierarchy exhibits, on average, a power-law decay with exponent γ =1.57 . This exponent agrees with that found from simulations of the Hénon and Chirikov-Taylor maps. This provides evidence that the Meiss-Ott Markov tree model describes the transport for mixed systems.
Lyapunov exponents and particle dispersion in drift wave turbulence
DEFF Research Database (Denmark)
Pedersen, T.S.; Michelsen, Poul; Juul Rasmussen, J.
1996-01-01
The Hasegawa-Wakatani model equations for resistive drift waves are solved numerically for a range of values of the coupling due to the parallel electron motion. The largest Lyapunov exponent, lambda(1), is calculated to quantify the unpredictability of the turbulent flow and compared to other...... characteristic inverse time scales of the turbulence such as the linear growth rate and Lagrangian inverse time scales obtained by tracking virtual fluid particles. The results show a correlation between lambda(1) and the relative dispersion exponent, lambda(p), as well as to the inverse Lagrangian integral time...... contribute most to the relative dispersion of particles. (C) 1996 American Institute of Physics....
Implementation of Inquiry Strategy on Exponent, Roots and Logarithm
Sulistyowaty, R. K.; Prafianti, R. A.
2017-09-01
The aim of this research is to enhancing students’ learning outcomes on exponent, roots, and logarithm through the implementation of Inquiry strategy. This research is a descriptive qualitative research with classroom action research approach which was done in three cycles. Each cycle consists of 4 steps, those are: planning, acting, observing and reflecting. This research had been conducted with 30 students (17 female and 13 male) studying in the 10th grade. Data was collected from students through documentation, observation, and test. The data was analyzed using descriptive qualitative and quantitative methods. The findings revealed that Inquiry strategy affected students’ learning outcomes on exponent, roots, and logarithm.
Infrared Camera Analysis of Laser Hardening
Directory of Open Access Journals (Sweden)
J. Tesar
2012-01-01
Full Text Available The improvement of surface properties such as laser hardening becomes very important in present manufacturing. Resulting laser hardening depth and surface hardness can be affected by changes in optical properties of material surface, that is, by absorptivity that gives the ratio between absorbed energy and incident laser energy. The surface changes on tested sample of steel block were made by engraving laser with different scanning velocity and repetition frequency. During the laser hardening the process was observed by infrared (IR camera system that measures infrared radiation from the heated sample and depicts it in a form of temperature field. The images from the IR camera of the sample are shown, and maximal temperatures of all engraved areas are evaluated and compared. The surface hardness was measured, and the hardening depth was estimated from the measured hardness profile in the sample cross-section. The correlation between reached temperature, surface hardness, and hardening depth is shown. The highest and the lowest temperatures correspond to the lowest/highest hardness and the highest/lowest hardening depth.
Inverted rank distributions: Macroscopic statistics, universality classes, and critical exponents
Eliazar, Iddo; Cohen, Morrel H.
2014-01-01
An inverted rank distribution is an infinite sequence of positive sizes ordered in a monotone increasing fashion. Interlacing together Lorenzian and oligarchic asymptotic analyses, we establish a macroscopic classification of inverted rank distributions into five “socioeconomic” universality classes: communism, socialism, criticality, feudalism, and absolute monarchy. We further establish that: (i) communism and socialism are analogous to a “disordered phase”, feudalism and absolute monarchy are analogous to an “ordered phase”, and criticality is the “phase transition” between order and disorder; (ii) the universality classes are characterized by two critical exponents, one governing the ordered phase, and the other governing the disordered phase; (iii) communism, criticality, and absolute monarchy are characterized by sharp exponent values, and are inherently deterministic; (iv) socialism is characterized by a continuous exponent range, is inherently stochastic, and is universally governed by continuous power-law statistics; (v) feudalism is characterized by a continuous exponent range, is inherently stochastic, and is universally governed by discrete exponential statistics. The results presented in this paper yield a universal macroscopic socioeconophysical perspective of inverted rank distributions.
Error Exponents for Target-Class Detection with Nuisance Parameters
National Research Council Canada - National Science Library
Misra, Saswat; Tong, Lang
2007-01-01
...) has at least one unknown component, we use the theory of adaptive tests to prove that there exists a test that achieves the same error exponent as if (gamma, theta) were known in some scenarios, but that there exists no such test in others.
Density-scaling exponents and virial potential-energy correlation ...
Indian Academy of Sciences (India)
This paper investigates the relation between the density-scaling exponent γ and the virial potential energy correlation coefficient R at several thermodynamic state points in three dimensions for the generalized (2n, n) Lennard-Jones (LJ) system for n = 4, 9, 12, 18, as well as for the standard n = 6 LJ system in two,three, and ...
Bayesian Estimation of the Logistic Positive Exponent IRT Model
Bolfarine, Heleno; Bazan, Jorge Luis
2010-01-01
A Bayesian inference approach using Markov Chain Monte Carlo (MCMC) is developed for the logistic positive exponent (LPE) model proposed by Samejima and for a new skewed Logistic Item Response Theory (IRT) model, named Reflection LPE model. Both models lead to asymmetric item characteristic curves (ICC) and can be appropriate because a symmetric…
Analysis of Human Standing Balance by Largest Lyapunov Exponent
Directory of Open Access Journals (Sweden)
Kun Liu
2015-01-01
Full Text Available The purpose of this research is to analyse the relationship between nonlinear dynamic character and individuals’ standing balance by the largest Lyapunov exponent, which is regarded as a metric for assessing standing balance. According to previous study, the largest Lyapunov exponent from centre of pressure time series could not well quantify the human balance ability. In this research, two improvements were made. Firstly, an external stimulus was applied to feet in the form of continuous horizontal sinusoidal motion by a moving platform. Secondly, a multiaccelerometer subsystem was adopted. Twenty healthy volunteers participated in this experiment. A new metric, coordinated largest Lyapunov exponent was proposed, which reflected the relationship of body segments by integrating multidimensional largest Lyapunov exponent values. By using this metric in actual standing performance under sinusoidal stimulus, an obvious relationship between the new metric and the actual balance ability was found in the majority of the subjects. These results show that the sinusoidal stimulus can make human balance characteristics more obvious, which is beneficial to assess balance, and balance is determined by the ability of coordinating all body segments.
determination of the power law exponent for southern highlands of ...
African Journals Online (AJOL)
Mgina
ABSTRACT. The 1/7th power law is among the methods that have been used to extrapolate wind speed to the hub heights of wind turbines from the measuring levels. However, it tends to underestimate the actual long-term average wind speeds. In this paper, the power law exponent for Makambako, a site located in the ...
Precipitation hardening of biodegradable Fe-Mn-Pd alloys
Energy Technology Data Exchange (ETDEWEB)
Moszner, F. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Sologubenko, A.S. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Schinhammer, M. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Lerchbacher, C. [Christian Doppler Laboratory for Early Stages of Precipitation, University of Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Haenzi, A.C. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Leitner, H. [Christian Doppler Laboratory for Early Stages of Precipitation, University of Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Uggowitzer, P.J. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Loeffler, J.F., E-mail: joerg.loeffler@mat.ethz.ch [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)
2011-02-15
This work presents a phenomenological description of the precipitation controlled hardening of a new biodegradable Fe-based alloy developed to fulfill the requirements of temporary implant applications. Pronounced strengthening of the solution-treated martensitic Fe-10Mn-1Pd (in wt.%) alloy upon isothermal aging at temperatures within the ferrite-austenite phase field is observed and attributed to the thermally activated formation of coherent plate-like Pd-rich precipitates on {l_brace}1 0 0{r_brace} planes of the matrix. The onset and the early stages of alloy decomposition were studied using two complementary techniques: transmission electron microscopy and three-dimensional atom probe analysis. Three distinct regions of the hardening kinetics are recognized and closely correlated to the evolution of the alloy microstructure. Upon aging, clustering of Pd atoms within the Fe-Mn solid solution occurs. The very small clusters grow, coarsen and adopt a plate-like shape, rearranging mutually to reduce the overall elastic strain energy. The elastic interaction of the dislocation substructure with Pd-rich precipitates of evolving morphology affects the dislocation mobility and is responsible for the hardness evolution of the alloy. A study of the hardening kinetics shows that the process exhibits all the features characteristic of maraging steels.
Influences of Steelmaking Slags on Hydration and Hardening of Concretes
Kirsanova, A. A.; Dildin, A. N.; Maksimov, S. P.
2017-11-01
It is shown that the slag of metallurgical production can be used in the construction industry as an active mineral additive for concrete. This approach allows us to solve environmental problems and reduce costs for the production of binder and concrete simultaneously. Most often slag is used in the form of a filler, an active mineral additive or as a part of a binder for artificial conglomerates. The introduction of slag allows one to notice a part of the cement, to obtain concretes that are more resistant to the impact of aggressive sulfate media. The paper shows the possibility of using recycled steel-smelting slags in the construction industry for the production of cement. An assessment was made of their effect on the hydration of the cement stone and hardening of the concrete together with the plasticizer under normal conditions. In the process of work, we used the slag of the Zlatoust Electrometallurgical Factory. Possible limitations of the content of steel-slag slag in concrete because of the possible presence of harmful impurities are shown. It is necessary to enter slag in conjunction with superplasticizers to reduce the flow of water mixing. Slags can be used as a hardening accelerator for cement concrete as they allow one to increase the degree of cement hydration and concrete strength. It is shown that slags can be used to produce fast-hardening concretes and their comparative characteristics with other active mineral additives are given.
Effects of residual stress on irradiation hardening in stainless steels
Energy Technology Data Exchange (ETDEWEB)
Okubo, N.; Kondo, K.; Kaji, Y. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Miwa, Y. [Nuclear Energy and Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken (Japan)
2007-07-01
Full text of publication follows: Structural materials in fusion reactor with water cooling system will undergo corrosion in aqueous environment and heavier irradiation than that in LWR. Irradiation assisted stress corrosion (IASCC) may be induced in stainless steels exposed in these environment for a long term of reactor operation. The IASCC is considered to be caused in a welding zone. It is difficult to predict and estimate the IASCC, because several irradiation effects (irradiation hardening, swelling, irradiation induced stress relaxation, etc) work intricately. Firstly, effects of residual stress on irradiation hardening were investigated in stainless steels. Specimens used in this study were SUS316 and SUS316L. By bending deformation, the specimens with several % plastic strain, which corresponds to weld residual stress, were prepared. Ion irradiations of 12 MeV Ni{sup 3+} were performed at 330, 400 and 550 deg. C to 45 dpa in TIARA facility at JAEA. No bent specimen was simultaneously irradiated with the bent specimen. The residual stress was estimated by X-ray residual stress measurements before and after the irradiation. The micro-hardness was measured by using nano-indenter. The irradiation hardening and the stress relaxation were changed by irradiation under bending deformation. The residual stress did not relax even for the case of the higher temperature aging at 500 deg. C for the same time of irradiation. The residual stress after ion irradiation, however, relaxed at these experimental temperatures in SUS316L. The hardness was obviously suppressed in bent SUS316L irradiated at 300 deg. C to 6 or 12 dpa. It was evident that irradiation induced stress relaxation occasionally suppressed the irradiation hardening in SUS316L. (authors)
Simultaneous surface engineering and bulk hardening of precipitation hardening stainless steel
DEFF Research Database (Denmark)
Frandsen, Rasmus Berg; Christiansen, Thomas; Somers, Marcel A. J.
2006-01-01
This article addresses simultaneous bulk precipitation hardening and low temperature surface engineering of two commercial precipitation hardening stainless steels: Sandvik Nanoflex® and Uddeholm Corrax®. Surface engineering comprised gaseous nitriding or gaseous carburising. Microstructural....... The duration and temperature of the nitriding/carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening stainless steel....... characterisation of the cases developed included X-ray diffraction analysis, reflected light microscopy and micro-hardness testing. It was found that the incorporation of nitrogen or carbon resulted in a hardened case consisting of a combination of (tetragonal) martensite and expanded (cubic) austenite...
Analysis of the regimes in the scanner-based laser hardening process
Martínez, S.; Lamikiz, A.; Ukar, E.; Calleja, A.; Arrizubieta, J. A.; Lopez de Lacalle, L. N.
2017-03-01
Laser hardening is becoming a consolidated process in different industrial sectors such as the automotive industry or in the die and mold industry. The key to ensure the success in this process is to control the surface temperature and the hardened layer thickness. Furthermore, the development of reliable scanners, based on moving optics for guiding high power lasers at extremely fast speeds allows the rapid motion of laser spots, resulting on tailored shapes of swept areas by the laser. If a scanner is used to sweep a determined area, the laser energy density distribution can be adapted by varying parameters such us the scanning speed or laser power inside this area. Despite its advantages in terms of versatility, the use of scanners for the laser hardening process has not yet been introduced in the thermal hardening industry because of the difficulty of the temperature control and possible non-homogeneous hardness thickness layers. In the present work the laser hardening process with scanning optics applied to AISI 1045 steel has been studied, with special emphasis on the influence of the scanning speed and the results derived from its variation, the evolution of the hardened layer thickness and different strategies for the control of the process temperature. For this purpose, the hardened material has been studied by measuring microhardness at different points and the shape of the hardened layer has also been evaluated. All tests have been performed using an experimental setup designed to keep a nominal temperature value using a closed-loop control. The tests results show two different regimes depending on the scanning speed and feed rate values. The experimental results conclusions have been validated by means of thermal simulations at different conditions.
Segmentation-free empirical beam hardening correction for CT
Energy Technology Data Exchange (ETDEWEB)
Schüller, Sören; Sawall, Stefan [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich [Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim (Germany); Kachelrieß, Marc, E-mail: marc.kachelriess@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)
2015-02-15
Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the
a Comparison of Three Hurst Exponent Approaches to Predict Nascent Bubbles in S&P500 Stocks
Fernández-Martínez, M.; Sánchez-Granero, M. A.; Muñoz Torrecillas, M. J.; McKelvey, Bill
Since the pioneer contributions due to Vandewalle and Ausloos, the Hurst exponent has been applied by econophysicists as a useful indicator to deal with investment strategies when such a value is above or below 0.5, the Hurst exponent of a Brownian motion. In this paper, we hypothesize that the self-similarity exponent of financial time series provides a reliable indicator for herding behavior (HB) in the following sense: if there is HB, then the higher the price, the more the people will buy. This will generate persistence in the stocks which we shall measure by their self-similarity exponents. Along this work, we shall explore whether there is some connections between the self-similarity exponent of a stock (as a HB indicator) and the stock’s future performance under the assumption that the HB will last for some time. With this aim, three approaches to calculate the self-similarity exponent of a time series are compared in order to determine which performs best to identify the transition from random efficient market behavior to HB and hence, to detect the beginning of a bubble. Generalized Hurst Exponent, Detrended Fluctuation Analysis, and GM2 algorithms have been tested. Traditionally, researchers have focused on identifying the beginning of a crash. We study the beginning of the transition from efficient market behavior to a market bubble, instead. Our empirical results support that the higher (respectively the lower) the self-similarity index, the higher (respectively the lower) the mean of the price change, and hence, the better (respectively the worse) the performance of the corresponding stock. This would imply, as a consequence, that the transition process from random efficient market to HB has started. For experimentation purposes, S&P500 stock Index constituted our main data source.
National Research Council Canada - National Science Library
J. Przondziono; E. Hadasik; W. Walke; J. Mendala
2016-01-01
The study presents results of tests of impact of work hardening in cold drawing process, surface treatment and sterilisation on resistance to electrochemical corrosion of wires made of stainless steel...
He, W.
2016-12-01
The climate system is a classical spatiotemporal evolutionary dynamic system with spatiotemporal correlation characteristics. Based on this, two-dimensional detrended fluctuation analysis (TD-DFA) is used to estimate the Hurst exponent of two-dimensional images. Then, we monitored the change of the Hurst exponent of the images to identify an abrupt dynamic change. We tested the performance of this method with a coupled spatiotemporal dynamic model and found that it works well. The changes in the Hurst exponents of the spatial images are stable when there is no dynamic change in the system, but there will be a clear non-stationary change of the Hurst exponents; for example, the abrupt mean values change if the dynamics of the system change. Thus, the TD-DFA method is suitable for detecting an abrupt dynamic change from natural and artificial images. The spatial images of the NCEP reanalysis of the daily average temperature exhibited fractality. Based on this, we found three non-stationary changes in the Hurst exponents for the NCEP reanalysis of the daily average temperature or for the annual average temperature in the region (60°S-60°N). It can be concluded that the climate system may have incurred three dynamic changes since 1961 on decadal timescales, i.e., in approximately the mid-1970s, the mid-1980s, and between the late 1990s and the early 2000s.
Lyapunov exponents a tool to explore complex dynamics
Pikovsky, Arkady
2016-01-01
Lyapunov exponents lie at the heart of chaos theory, and are widely used in studies of complex dynamics. Utilising a pragmatic, physical approach, this self-contained book provides a comprehensive description of the concept. Beginning with the basic properties and numerical methods, it then guides readers through to the most recent advances in applications to complex systems. Practical algorithms are thoroughly reviewed and their performance is discussed, while a broad set of examples illustrate the wide range of potential applications. The description of various numerical and analytical techniques for the computation of Lyapunov exponents offers an extensive array of tools for the characterization of phenomena such as synchronization, weak and global chaos in low and high-dimensional set-ups, and localization. This text equips readers with all the investigative expertise needed to fully explore the dynamical properties of complex systems, making it ideal for both graduate students and experienced researchers...
Accurate Monte Carlo critical exponents for Ising lattices
García, Jorge; Gonzalo, Julio A.
2003-08-01
A careful Monte Carlo investigation of the phase transition very close to the critical point ( T→ Tc, H→0) in relatively large d=3, s= {1}/{2} Ising lattices did produce critical exponents β3 D=0.3126(4)≅5/16, δ3 D-1=0.1997(4)≅1/5 and γ3 D=1.253(4)≅5/4. Our results indicate that, within experimental error, they are given by simple fractions corresponding to the linear interpolations between the respective two dimensional (Onsager) and four dimensional (mean field) critical exponents. An analysis of our inverse susceptibility data χ-1( T) vs. | T- Tc| shows that these data lead to a value of γ3 D compatible with γ‧= γ and Tc=4.51152(12), while γ values obtained recently by high and low temperature series expansions and renormalization group methods are not.
Determination of critical exponents of inhomogeneous Gd films
Energy Technology Data Exchange (ETDEWEB)
Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Salazar, N.A. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Hovorka, O.; Idigoras, O.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain)
2012-08-15
The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T{sub AN}=200, 400, and 500 Degree-Sign C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T{sub C} was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.
Scaling exponents for fracture surfaces in opal glass
Energy Technology Data Exchange (ETDEWEB)
Chavez-Guerrero, L., E-mail: guerreroleo@hotmail.com [Facultad de Ingenieria Mecanica y Electrica. Cd. Universitaria s/n, C.P. 66450, Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico); Center of Innovation, Research and Development on Engineering and Technology, Universidad Autonoma de Nuevo Leon Monterrey, C.P. 66600, Apodaca, Nuevo Leon (Mexico); Garza, F.J., E-mail: fjgarza@gama.fime.uanl.mx [Facultad de Ciencias Quimicas, Cd. Universitaria s/n, C.P. 66450, Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico); Hinojosa, M., E-mail: hinojosa@gama.fime.uanl.mx [Facultad de Ingenieria Mecanica y Electrica. Cd. Universitaria s/n, C.P. 66450, Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico); Center of Innovation, Research and Development on Engineering and Technology, Universidad Autonoma de Nuevo Leon Monterrey, C.P. 66600, Apodaca, Nuevo Leon (Mexico)
2010-09-25
We have investigated the scaling properties of fracture surfaces in opal glass. Specimens with two different opacifying particle sizes (1 {mu}m and 0.4 {mu}m) were broken by three-point bending test and the resulting fracture surfaces were analyzed using Atomic Force Microscopy. The analysis of the self-affine behavior was performed using the Variable Bandwidth and Height-Height Correlation Methods, and both the roughness exponent, {zeta}, and the correlation length, {xi}, were determined. It was found that the roughness exponent obtained in both samples is {zeta} {approx} 0.8; whereas the correlation length in both fractures is of the order of the particle size, demonstrating the dependence of this self-affine parameter on the microstructure of opal glass.
Investigation of Hardened Filling Grout Samples
DEFF Research Database (Denmark)
Sørensen, Eigil V.
Suzlon Wind Energy A/S requested on August 28, 2007 an investigation of 2 samples of a hardened filling grout to be carried out, comprising drilling and strength determination of 4 test cylinders, and description of the surface characteristics of the samples....... Suzlon Wind Energy A/S requested on August 28, 2007 an investigation of 2 samples of a hardened filling grout to be carried out, comprising drilling and strength determination of 4 test cylinders, and description of the surface characteristics of the samples....
Radiation hardening revisited: Role of intracascade clustering
DEFF Research Database (Denmark)
Singh, B.N.; Foreman, A.J.E.; Trinkaus, H.
1997-01-01
be explained in terms of conventional dispersed-barrier hardening because (a) the grown-in dislocations are not free, and (b) irradiation-induced defect clusters are not rigid indestructible Orowan obstacles. A new model called 'cascade-induced source hardening' is presented where glissile loops produced...... directly in cascades are envisaged to decorate the grown-in dislocations so that they cannot act as dislocation sources. The upper yield stress is related to the breakaway stress which is necessary to pull the dislocation away from the clusters/loops decorating it. The magnitude of the breakaway stress has...
Lyapunov exponents for complex systems with delayed feedback
Dailyudenko, V F
2003-01-01
Analytical and numerical analysis is implemented for two methods of Lyapunov exponents calculation. The first is based on successive multiplication of functional matrixes corresponding to discrete transformations and calculation of eigenvalues for the obtained matrix. The second approach is based on successive orthogonalization of multiplied matrixes using QR-decomposition. The analytical model for describing functional maps of discrete iterations derived from delay differential equation is proposed, which implements representation of the product matrix through matrixes of canonical form that reduces calculation complexity.
Clustering of Casablanca stock market based on hurst exponent estimates
Lahmiri, Salim
2016-08-01
This paper deals with the problem of Casablanca Stock Exchange (CSE) topology modeling as a complex network during three different market regimes: general trend characterized by ups and downs, increasing trend, and decreasing trend. In particular, a set of seven different Hurst exponent estimates are used to characterize long-range dependence in each industrial sector generating process. They are employed in conjunction with hierarchical clustering approach to examine the co-movements of the Casablanca Stock Exchange industrial sectors. The purpose is to investigate whether cluster structures are similar across variable, increasing and decreasing regimes. It is observed that the general structure of the CSE topology has been considerably changed over 2009 (variable regime), 2010 (increasing regime), and 2011 (decreasing regime) time periods. The most important findings follow. First, in general a high value of Hurst exponent is associated to a variable regime and a small one to a decreasing regime. In addition, Hurst estimates during increasing regime are higher than those of a decreasing regime. Second, correlations between estimated Hurst exponent vectors of industrial sectors increase when Casablanca stock exchange follows an upward regime, whilst they decrease when the overall market follows a downward regime.
Quantum Lyapunov Exponent of an Atomic Kicked Rotor
Galitski, Victor
2017-04-01
One of the most intriguing phenomena in the studies of classical chaos is the butterfly effect, which manifests itself in that small changes in initial conditions lead to drastically different trajectories. It is characterized by a Lyapunov exponent that measures divergence of the classical trajectories. The question how/if this prototypical effect of classical chaos theory generalizes to quantum systems (where the notion of a trajectory is undefined) has been of interest for decades, but became more popular recently, when it was realized that there exist intriguing connections to string theory and general relativity in some quantum chaotic models. At the center of this activity is the so-called out-of-time-ordered correlator (OTOC) - a quantity that in the classical limit seems to approximate the classical Lyapunov correlator. However, there are very few solvable models where one can actually calculate Lyapunov exponent and/or OTOC. In this talk, I will discuss the standard model of quantum and classical chaos - kicked rotor - calculate the correlator and Lypunov exponents, and show how classical chaos and Lyapunov divergence develop and cross-over to the quantum regime. We will see that the quantum out-of-time-ordered correlator exhibits a clear singularity at the Ehrenfest time, when quantum interference effects sharply kick in: transitioning from a time-independent value to its monotonous decrease with time. In conclusion, I will discuss possible experimental realizations of the model and predicted phenomena in ultracold quantum kicked rotors. NSF-DMR 1613029 and US-ARO.
Meteoroid stream flux densities and the zenith exponent
Molau, Sirko; Barentsen, Geert
2013-01-01
The MetRec software was recently extended to measure the limiting magnitude in real-time, and to determine meteoroid stream flux densities. This paper gives a short overview of the applied algorithms. We introduce the MetRec Flux Viewer, a web tool to visualize activity profiles on- line. Starting from the Lyrids 2011, high-quality flux density profiles were derived from IMO Video Network observations for every major meteor shower. They are often in good agreement with visual data. Analyzing the 2011 Perseids, we found systematic daily variations in the flux density profile, which can be attributed to a zenith exponent gamma > 1.0. We analyzed a number of meteor showers in detail and found zenith exponent variations from shower to shower in the range between 1.55 and 2.0. The average value over all analyzed showers is gamma = 1.75. In order to determine the zenith exponent precisely, the observations must cover a large altitude range (at least 45 degrees).
The development of radiation hardened robot for nuclear facility
Energy Technology Data Exchange (ETDEWEB)
Kim, Seung Ho; Jung, Seung Ho; Kim, Byung Soo and others
2000-04-01
The work conducted in this stage covers development of core technology of tele-robot system including monitoring technique in high-level radioactive area, tele-sensing technology and radiation-hardened technology for the non-destructive tele-inspection system which monitors the primary coolant system during the normal operations of PHWR(Pressurized Heavy Water Reactor) NPPs and measures the decrease of bending part of feeder pipe during overall. Based on the developed core technology, the monitoring mobile robot system of the primary coolant system and the feeder pipe inspecting robot system are developed.
HTPro: Low-temperature Surface Hardening of Stainless Steel
DEFF Research Database (Denmark)
Christiansen, Thomas Lundin; Somers, Marcel A. J.
2013-01-01
Low-temperature surface hardening of stainless steel provides the required performance properties without affecting corrosion resistance.......Low-temperature surface hardening of stainless steel provides the required performance properties without affecting corrosion resistance....
Mesoscopic model for ferromagnets with isotropic hardening
Czech Academy of Sciences Publication Activity Database
Roubíček, Tomáš; Kružík, Martin
2005-01-01
Roč. 56, č. 1 (2005), s. 107-135 ISSN 0044-2275 R&D Projects: GA AV ČR IAA1075005 Institutional research plan: CEZ:AV0Z10750506 Keywords : variational inequalities * ferromagnetism * hysteresis, hardening Subject RIV: BA - General Mathematics Impact factor: 0.455, year: 2005
CASE-HARDENING OF STAINLESS STEEL
DEFF Research Database (Denmark)
2004-01-01
The invention relates to case-hardening of a stainless steel article by means of gas including carbon and/or nitrogen, whereby carbon and/or nitrogen atoms diffuse through the surface into the article. The method includes activating the surface of the article, applying a top layer on the activated...
Instabilities in power law gradient hardening materials
DEFF Research Database (Denmark)
Niordson, Christian Frithiof; Tvergaard, Viggo
2005-01-01
Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...
A case hardened component of titanium
DEFF Research Database (Denmark)
2017-01-01
The present invention relates to a case hardened component of a titanium alloy, the component having a diffusion zone of a thickness of at least 50 μιτι, as calculated from the surface of the component, the diffusion zone comprising oxygen and carbon in solid solution and having a distinct phase...
[Microstructural changes in hardened beans (Phaseolus vulgaris)].
Mujica, Maria Virginia; Granito, Marisela; Soto, Naudy
2015-06-01
(Phaseolus vulgaris). The hardening of Phaseolus vulgaris beans stored at high temperature and high relative humidity is one of the main constraints for consumption. The objective of this research was to evaluate by scanning electron microscopy, structural changes in cotyledons and testa of the hardened beans. The freshly harvested grains were stored for twelve months under two conditions: 5 ° C-34% RH and 37 ° C-75% RH, in order to promote hardening. The stored raw and cooked grains were lyophilized and fractured. The sections of testa and cotyledons were observed in an electron microscope JSM-6390. After twelve months, grains stored at 37 ° C-75% RH increased their hardness by 503%, whereas there were no significant changes in grains stored at 5 ° C-34% RH. At the microstructural level, the cotyledons of the raw grains show clear differences in appearance of the cell wall, into the intercellular space size and texture matrix protein. There were also differences in compaction of palisade and sub-epidermal layer in the testa of raw grains. After cooking, cotyledon cells of the soft grains were well separated while these ofhard grains were seldom separated. In conclusion, the found differences in hard and soft grains showed a significant participation of both structures, cotyledons and testa, in the grains hardening.
Multi-MGy Radiation Hardened Camera for Nuclear Facilities
Energy Technology Data Exchange (ETDEWEB)
Girard, Sylvain; Boukenter, Aziz; Ouerdane, Youcef [Universite de Saint-Etienne, Lab. Hubert Curien, UMR-CNRS 5516, F-42000 Saint-Etienne (France); Goiffon, Vincent; Corbiere, Franck; Rolando, Sebastien; Molina, Romain; Estribeau, Magali; Avon, Barbara; Magnan, Pierre [ISAE, Universite de Toulouse, F-31055 Toulouse (France); Paillet, Philippe; Duhamel, Olivier; Gaillardin, Marc; Raine, Melanie [CEA, DAM, DIF, F-91297 Arpajon (France)
2015-07-01
There is an increasing interest in developing cameras for surveillance systems to monitor nuclear facilities or nuclear waste storages. Particularly, for today's and the next generation of nuclear facilities increasing safety requirements consecutive to Fukushima Daiichi's disaster have to be considered. For some applications, radiation tolerance needs to overcome doses in the MGy(SiO{sub 2}) range whereas the most tolerant commercial or prototypes products based on solid state image sensors withstand doses up to few kGy. The objective of this work is to present the radiation hardening strategy developed by our research groups to enhance the tolerance to ionizing radiations of the various subparts of these imaging systems by working simultaneously at the component and system design levels. Developing radiation-hardened camera implies to combine several radiation-hardening strategies. In our case, we decided not to use the simplest one, the shielding approach. This approach is efficient but limits the camera miniaturization and is not compatible with its future integration in remote-handling or robotic systems. Then, the hardening-by-component strategy appears mandatory to avoid the failure of one of the camera subparts at doses lower than the MGy. Concerning the image sensor itself, the used technology is a CMOS Image Sensor (CIS) designed by ISAE team with custom pixel designs used to mitigate the total ionizing dose (TID) effects that occur well below the MGy range in classical image sensors (e.g. Charge Coupled Devices (CCD), Charge Injection Devices (CID) and classical Active Pixel Sensors (APS)), such as the complete loss of functionality, the dark current increase and the gain drop. We'll present at the conference a comparative study between these radiation-hardened pixel radiation responses with respect to conventional ones, demonstrating the efficiency of the choices made. The targeted strategy to develop the complete radiation hard camera
Ay, Mohammad Reza; Mehranian, Abolfazi; Maleki, Asghar; Ghadiri, Hossien; Ghafarian, Pardis; Zaidi, Habib
Beam hardening filters have long been employed in X-ray Computed Tomography (CT) to preferentially absorb soft and low-energy X-rays having no or little contribution to image formation, thus allowing the reduction of patient dose and beam hardening artefacts. In this work, we studied the influence
Universal scaling in disordered systems and nonuniversal exponents
Bardhan, K. K.; Talukdar, D.; Nandi, U. N.; Mukherjee, C. D.
2014-05-01
The effect of an electric field on conduction in a disordered system is an old but largely unsolved problem. Experiments cover a wide variety of systems—amorphous/doped semiconductors, conducting polymers, organic crystals, manganites, composites, metallic alloys, double perovskites—ranging from strongly to weakly localized systems and from strongly to weakly correlated ones. Theories have singularly failed to predict any universal trend resulting in separate theories for separate systems. Here, we discuss a one-parameter scaling that has recently been found to give a systematic account of the field-dependent conductance in two diverse, strongly localized systems of conducting polymers and manganites. Except for a limited number of systems which are described by the hot electron models, the vast majority of different systems in various disorder regimes in two (2D)- and three (2D)-dimensions obey the scaling. The nonlinearity exponent x associated with the scaling was found to be nonuniversal and exhibiting a structure. For 2D weakly localized systems, the nonlinearity exponent x is ≥7 and is roughly inversely proportional to the sheet resistance. The existing theories of weak localization prove to be adequate and a complete scaling function is derived. In a 2D strongly localized system, a temperature-induced scaling-nonscaling transition (SNST) is revealed. For 3D strongly localized systems, the exponent lies between -1 and 1, and surprisingly is quantized (x ≈0.08n). This poses a serious theoretical challenge. Various results are compared with predictions of the existing theories.
Fatigue crack shape prediction based on the stress singularity exponent
Czech Academy of Sciences Publication Activity Database
Hutař, Pavel; Ševčík, Martin; Náhlík, Luboš; Knésl, Zdeněk
488-489, č. 1 (2012), s. 178-181 ISSN 1013-9826. [International Conference on Fracture and Damage Mechanics - FDM 2011 /10./. Dubrovník, 19.09.2011-21.09.2011] R&D Projects: GA ČR GA101/09/0867 Grant - others:GA AV ČR(CZ) M100420901 Institutional research plan: CEZ:AV0Z2041904 Keywords : stress singularity exponent * crack front curvature * vertex singularity * free surface effect Subject RIV: JL - Materials Fatigue, Friction Mechanics
Pixel classification based color image segmentation using quaternion exponent moments.
Wang, Xiang-Yang; Wu, Zhi-Fang; Chen, Liang; Zheng, Hong-Liang; Yang, Hong-Ying
2016-02-01
Image segmentation remains an important, but hard-to-solve, problem since it appears to be application dependent with usually no a priori information available regarding the image structure. In recent years, many image segmentation algorithms have been developed, but they are often very complex and some undesired results occur frequently. In this paper, we propose a pixel classification based color image segmentation using quaternion exponent moments. Firstly, the pixel-level image feature is extracted based on quaternion exponent moments (QEMs), which can capture effectively the image pixel content by considering the correlation between different color channels. Then, the pixel-level image feature is used as input of twin support vector machines (TSVM) classifier, and the TSVM model is trained by selecting the training samples with Arimoto entropy thresholding. Finally, the color image is segmented with the trained TSVM model. The proposed scheme has the following advantages: (1) the effective QEMs is introduced to describe color image pixel content, which considers the correlation between different color channels, (2) the excellent TSVM classifier is utilized, which has lower computation time and higher classification accuracy. Experimental results show that our proposed method has very promising segmentation performance compared with the state-of-the-art segmentation approaches recently proposed in the literature. Copyright © 2015 Elsevier Ltd. All rights reserved.
Truncatable bootstrap equations in algebraic form and critical surface exponents
Energy Technology Data Exchange (ETDEWEB)
Gliozzi, Ferdinando [Dipartimento di Fisica, Università di Torino andIstituto Nazionale di Fisica Nucleare - sezione di Torino,Via P. Giuria 1, Torino, I-10125 (Italy)
2016-10-10
We describe examples of drastic truncations of conformal bootstrap equations encoding much more information than that obtained by a direct numerical approach. A three-term truncation of the four point function of a free scalar in any space dimensions provides algebraic identities among conformal block derivatives which generate the exact spectrum of the infinitely many primary operators contributing to it. In boundary conformal field theories, we point out that the appearance of free parameters in the solutions of bootstrap equations is not an artifact of truncations, rather it reflects a physical property of permeable conformal interfaces which are described by the same equations. Surface transitions correspond to isolated points in the parameter space. We are able to locate them in the case of 3d Ising model, thanks to a useful algebraic form of 3d boundary bootstrap equations. It turns out that the low-lying spectra of the surface operators in the ordinary and the special transitions of 3d Ising model form two different solutions of the same polynomial equation. Their interplay yields an estimate of the surface renormalization group exponents, y{sub h}=0.72558(18) for the ordinary universality class and y{sub h}=1.646(2) for the special universality class, which compare well with the most recent Monte Carlo calculations. Estimates of other surface exponents as well as OPE coefficients are also obtained.
Entropies and Scaling Exponents of Street and Fracture Networks
Directory of Open Access Journals (Sweden)
Agust Gudmundsson
2012-04-01
Full Text Available Many natural and man-made lineaments form networks that can be analysed through entropy and energy considerations. Here we report the results of a detailed study of the variations in trends and lengths of 1554 named streets and 6004 street segments, forming a part of the evolving street network of the city of Dundee in East Scotland. Based on changes in the scaling exponents (ranging from 0.24 to 3.89, the streets can be divided into 21 populations. For comparison, we analysed 221 active crustal fractures in Iceland that (a are of similar lengths as the streets of Dundee; (b are composed of segments; and (c form evolving networks. The streets and fractures follow power-law size distributions (validated through various statistical tests that can be partly explained in terms of the energies needed for their formation. The entropies of the 21 street populations and 9 fracture populations show strong linear correlations with (1 the scaling exponents (R^{2} = 0.845–0.947 for streets, R^{2} = 0.859 for fractures and with (2 the length ranges, that is, the differences between the longest and shortest streets/fractures, (R^{2} = 0.845–0.906 for streets, R^{2} = 0.927 for fractures.
Improved technique to remove hardened sludge on top of Steam generator tube sheet
Energy Technology Data Exchange (ETDEWEB)
Baumgartl, R.
2015-07-01
Since many years the top of Steam Generator tube sheet is cleaned by high pressure water jets. In the standard process a multi-nozzle head is manipulated remote controlled inside the No tube lane. The high pressure water jets are directed between the inter-tube aisles. Inner bundle lancing enhanced the efficiency to remove hardened sludge at low flow areas above the tube sheet to a certain extent. For that the nozzle head is fed between the inner tube aisles thus reducing the work distance to a minimum. AREVA GmbH realized a hydraulic driven toothed blade to considerably raise the removal rate of the hardened sludge. (Author)
Anisotropic Hardening Behaviour and Springback of Advanced High-Strength Steels
Directory of Open Access Journals (Sweden)
Jaebong Jung
2017-11-01
Full Text Available Advanced high-strength steels (AHSSs exhibit large, and sometimes anisotropic, springback recovery after forming. Accurate description of the anisotropic elasto-plastic behaviour of sheet metals is critical for predicting their anisotropic springback behaviour. For some materials, the initial anisotropy is maintained while hardening progresses. However, for other materials, anisotropy changes with hardening. In this work, to account for the evolution of anisotropy of a dual-phase steel, an elastoplastic material constitutive model is developed. In particular, the combined isotropic–kinematic hardening model was modified. Tensile loading–unloading, uniaxial and biaxial tension, and tension–compression tests were conducted along the rolling, diagonal, and transverse directions to measure the anisotropic properties, and the parameters of the proposed constitutive model were determined. For validation, the proposed model was applied to a U-bending process, and the measured springback angles were compared to the predicted ones.
Densification and strain hardening of a metallic glass under tension at room temperature.
Wang, Z T; Pan, J; Li, Y; Schuh, C A
2013-09-27
The deformation of metallic glasses involves two competing processes: a disordering process involving dilatation, free volume accumulation, and softening, and a relaxation process involving diffusional ordering and densification. For metallic glasses at room temperature and under uniaxial loading, disordering usually dominates, and the glass can fail catastrophically as the softening process runs away in a localized mode. Here we demonstrate conditions where the opposite, unexpected, situation occurs: the densifying process dominates, resulting in stable plastic deformation and work hardening at room temperature. We report densification and hardening during deformation in a Zr-based glass under multiaxial loading, in a notched tensile geometry. The effect is driven by stress-enhanced diffusional relaxation, and is attended by a reduction in exothermic heat and hardening signatures similar to those observed in the classical thermal relaxation of glasses. The result is significant, stable, plastic, extensional flow in metallic glasses, which suggest a possibility of designing tough glasses based on their flow properties.
Induction surface hardening of hard coated steels
DEFF Research Database (Denmark)
Pantleon, Karen; Kessler, Olaf; Hoffmann, Franz
1999-01-01
-process is the high deposition temperature, consequently the properties of steel substrates are negatively influenced. Therefore, a subsequent heat treatment of the coated steels is necessary to restore the properties of steels ready for operation. Induction surface hardening is used as a method of heat treatment......, the scratch test is used to estimate critical loads for cohesive and adhesive failure of the coatings. Additionally, distortion measurements are carried out. The results emphasize the advantage of induction surface hardening as a method of subsequent heat treatment of CVD-coated steels....... after the deposition of TiN hard coatings on steel substrates. Influences of both the coating properties and the substrate properties are discussed in dependence on the parameters of induction heating. Thereby the heating time, heating atmosphere and the power input into the specimen are changed...
Prediction of Chloride Penetration into Hardening Concrete
Directory of Open Access Journals (Sweden)
Wei-Jie Fan
2015-01-01
Full Text Available In marine and coastal environments, penetration of chloride ions is one of the main mechanisms causing concrete reinforcement corrosion. Currently, most of experimental investigations about submerged penetration of chloride ions are started after the four-week standard curing of concrete. The further hydration of cement and reduction of chloride diffusivity during submerged penetration period are ignored. To overcome this weak point, this paper presents a numerical procedure to analyze simultaneously cement hydration reaction and chloride ion penetration process. First, using a cement hydration model, degree of hydration and phase volume fractions of hardening concrete are determined. Second, the dependences of chloride diffusivity and chloride binding capacity on age of concrete are clarified. Third, chloride profiles in hardening concrete are calculated. The proposed numerical procedure is verified by using chloride submerged penetration test results of concrete with different mixing proportions.
Radiation-hardened transistor and integrated circuit
Ma, Kwok K.
2007-11-20
A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.
Hardening of particle/oil/water suspensions due to capillary bridges
Danov, Krassimir D.; Georgiev, Mihail T.; Kralchevsky, Peter A.; Radulova, Gergana M.; Gurkov, Theodor D.; Stoyanov, Simeon D.; Pelan, Eddie G.
2018-01-01
Suspensions of colloid particles possess the remarkable property to solidify upon the addition of minimal amount of a second liquid that preferentially wets the particles. The hardening is due to the formation of capillary bridges (pendular rings), which connect the particles. Here, we review works
Constitutive modeling of quench-hardenable boron steel with tailored properties
Eller, Tom; Greve, L; Anders, M.T.; Medricky, M; Hatscher, A; Meinders, Vincent T.; van den Boogaard, Antonius H.; Volk, W.
2013-01-01
In this work, a material model is presented that predicts the crash-relevant constitutive behavior of quench-hardenable boron steel 22MnB5 as function of material hardness. Three sets of sheets of 22MnB5 are heat treated such that their as-treated microstructures are close to fully martensitic,
Relation Between Hertz Stress-Life Exponent, Ball-Race Conformity, and Ball Bearing Life
Zaretsky, Erwin V.; Poplawski, Joseph V.; Root, Lawrence E.
2008-01-01
ANSI/ABMA and ISO standards based on Lundberg-Palmgren bearing life theory are normalized for ball bearings having inner- and outerrace conformities of 52 percent (0.52) and made from pre-1940 bearing steel. The Lundberg-Palmgren theory incorporates an inverse 9th power relation between Hertz stress and fatigue life for ball bearings. The effect of race conformity on ball set life independent of race life is not incorporated into the Lundberg-Palmgren theory. In addition, post-1960 vacuum-processed bearing steel exhibits a 12th power relation between Hertz stress and life. The work reported extends the previous work of Zaretsky, Poplawski, and Root to calculate changes in bearing life--that includes the life of the ball set--caused by race conformity, Hertz stress-life exponent, ball bearing type and bearing series. The bearing fatigue life in actual application will usually be equal to or greater than that calculated using the ANSI/ABMA and ISO standards that incorporate the Lundberg-Palmgren theory. The relative fatigue life of an individual race is more sensitive to changes in race conformity for Hertz stress-life exponent n of 12 than where n = 9. However, when the effects are combined to predict actual bearing life for a specified set of conditions and bearing geometry, the predicted life of the bearing will be greater for a value of n = 12 than n = 9.
Helium irradiation induced hardening in MNHS steels
Cui, Minghuan; Wang, Ji; Wang, Zhiguang; Shen, Tielong; Wei, Kongfang; Yao, Cunfeng; Sun, Jianrong; Gao, Ning; Zhu, Yabin; Pang, Lilong; Wang, Dong; Zhu, Huiping; Han, Yi; Fang, Xuesong
2017-09-01
A recently developed reduced activation martensitic MNHS steel was irradiated with 200 keV helium (He) ions to a fluence of 1.0 × 1020 ions/m2 at 300 °C and 1.0 × 1021 ions/m2 at 300 °C and 450 °C. After irradiation, transmission electron microscopy (TEM) and nano-indentation measurements were used to investigate the hardness change and defects induced by He irradiation. Two kinds of defects including He bubbles and dislocation loops are observed by TEM. Irradiation induces hardening of MNHS steels and peak hardness values occur in all irradiated samples. Hardness increments induced by He bubbles and dislocation loops are predicted and fitted with the experimental peak hardness increment, based on the dispersed barrier-hardening (DBH) model and the size and number density of the two defects. A good agreement is got between the predicted and experimental hardness increment and the obstacle strength factor of He bubbles is a little stronger than the obstacle strength of dislocation loops. Other possible contributions to irradiation induced hardening are also discussed.
GRAVITY PIPELINE TRANSPORT FOR HARDENING FILLING MIXTURES
Directory of Open Access Journals (Sweden)
Leonid KROUPNIK
2015-12-01
Full Text Available In underground mining of solid minerals becoming increasingly common development system with stowing hardening mixtures. In this case the natural ore array after it is replaced by an artificial excavation of solidified filling mixture consisting of binder, aggregates and water. Such a mixture is prepared on the surface on special stowing complexes and transported underground at special stowing pipelines. However, it is transported to the horizons of a few kilometers, which requires a sustainable mode of motion of such a mixture in the pipeline. Hardening stowing mixture changes its rheological characteristics over time, which complicates the calculation of the parameters of pipeline transportation. The article suggests a method of determining the initial parameters of such mixtures: the status coefficient, indicator of transportability, coefficient of hydrodynamic resistance to motion of the mixture. These indicators characterize the mixture in terms of the possibility to transport it through pipes. On the basis of these indicators is proposed methodology for calculating the parameters of pipeline transport hardening filling mixtures in drift mode when traffic on the horizontal part of the mixture under pressure column of the mixture in the vertical part of the backfill of the pipeline. This technique allows stable operation is guaranteed to provide pipeline transportation.
Dong, Juan; Epp, Jeremy; Rocha, Alexandre da Silva; Nunes, Rafael Menezes; Zoch, Hans Werner
2016-02-01
In this study, the distortion of steel shafts was investigated before and after induction hardening. Several essential influencing factors in the manufacturing process chain regarding cold drawing, cutting method, notches on the shafts, and induction hardening were analyzed by design of experiment (DoE). Further necessary examinations of microstructures, hardness profile, segregation of chemical composition, and residual stress state were conducted for understanding the distortion behavior. The results of the statistical analysis of the DoE showed that the drawing process is the most important factor influencing distortion. The surface hardening depth of induction hardening is the second main factor. The relationship between inhomogeneities in the work pieces and the distortion was finally discussed.
Nonuniversality of roughness exponent of quasistatic fracture surfaces.
Ansari-Rad, Mehdi; Allaei, S Mehdi Vaez; Sahimi, Muhammad
2012-02-01
Numerous experiments have indicated that the fracture front (in three dimensions) and crack lines (in two dimensions) in disordered solids and rocklike materials is rough. It has been argued that the roughness exponent ζ is universal. Using extensive simulations of a two-dimensional model, we provide strong evidence that if extended correlations and anisotropy-two features that are prevalent in many materials-are incorporated in the models that are used in the numerical simulation of crack propagation, then ζ will vary considerably with the extent of the correlations and anisotropy. The results are consistent with recent experiments that also indicate deviations of ζ from its supposedly universal value, as well as with the data from rock samples. © 2012 American Physical Society
Computation of entropy and Lyapunov exponent by a shift transform
Energy Technology Data Exchange (ETDEWEB)
Matsuoka, Chihiro, E-mail: matsuoka.chihiro.mm@ehime-u.ac.jp [Department of Physics, Graduate School of Science and Technology, Ehime University, Matsuyama, Ehime 790-8577 (Japan); Hiraide, Koichi [Department of Mathematics, Graduate School of Science and Technology, Ehime University, Matsuyama, Ehime 790-8577 (Japan)
2015-10-15
We present a novel computational method to estimate the topological entropy and Lyapunov exponent of nonlinear maps using a shift transform. Unlike the computation of periodic orbits or the symbolic dynamical approach by the Markov partition, the method presented here does not require any special techniques in computational and mathematical fields to calculate these quantities. In spite of its simplicity, our method can accurately capture not only the chaotic region but also the non-chaotic region (window region) such that it is important physically but the (Lebesgue) measure zero and usually hard to calculate or observe. Furthermore, it is shown that the Kolmogorov-Sinai entropy of the Sinai-Ruelle-Bowen measure (the physical measure) coincides with the topological entropy.
Empirical beam hardening correction (EBHC) for CT
Energy Technology Data Exchange (ETDEWEB)
Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc [Institute of Medical Physics, University of Erlangen-Nuernberg, 91052 Erlangen (Germany)
2010-10-15
Purpose: Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. Methods: The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern
Empirical beam hardening correction (EBHC) for CT.
Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc
2010-10-01
Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (Tomo-Scope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern C-arm CT scanner
Implications of Grain Size Evolution for the Effective Stress Exponent in Ice
Behn, M. D.; Goldsby, D. L.; Hirth, G.
2016-12-01
Viscous flow in ice has typically been described by the Glen law—a non-Newtonian, power-law relationship between stress and strain-rate with a stress exponent n 3. The Glen law is attributed to grain-size-insensitive dislocation creep; however, laboratory and field studies demonstrate that deformation in ice is strongly dependent on grain size. This has led to the hypothesis that at sufficiently low stresses, ice flow is controlled by grain boundary sliding [1], which explicitly incorporates the grain-size dependence of ice rheology. Yet, neither dislocation creep (n 4), nor grain boundary sliding (n 1.8), have stress exponents that match the value of n 3 for the Glen law. Thus, although the Glen law provides an approximate description of ice flow in glaciers and ice sheets, its functional form cannot be explained by a single deformation mechanism. Here we seek to understand the origin of the n 3 dependence of the Glen law through a new model for grain-size evolution in ice. In our model, grain size evolves in response to the balance between dynamic recrystallization and grain growth. To simulate these processes we adapt the "wattmeter" [2], originally developed within the solid-Earth community to quantify grain size in crustal and mantle rocks. The wattmeter posits that grain size is controlled by a balance between the mechanical work required for grain growth and dynamic grain size reduction. The evolution of grain size in turn controls the relative contributions of dislocation creep and grain boundary sliding, and thus the effective stress exponent for ice flow. Using this approach, we first benchmark our grain size evolution model on experimental data and then calculate grain size in two end-member scenarios: (1) as a function of depth within an ice-sheet, and (2) across an ice-stream margin. We show that the calculated grain sizes match ice core observations for the interior of ice sheets. Furthermore, owing to the influence of grain size on strain rate, the
Uncertainty exponents for chaotic particle scattering in the magnetotail
Presley, M.; Holland, D. L.; Martin, R. F.; Matsuoka, H.
2009-12-01
In chaotic scattering systems such as the magnetotial, small uncertainties in the initial conditions make it difficult to predict whether a given particle will be forward-scattered or back-scattered in its interaction with the field reversal. A particle with initial conditions x0, is said to be ɛ certain if all of the particles with initial conditions x such that |x - x0|proportional to ɛ. For fractal basin boundaries, f(ɛ) is proportional to ɛ^α where α=N-D0 is the uncertainty exponent, N is the dimension of the phase space and D0 is the box counting dimension of the basin boundary. For αmandates a reduction in ɛ by a factor of 10^(1/α) and thus there is a high level of sensitivity to the initial conditions, (a hallmark of chaos.) In this paper we have examine the uncertainty exponent for chaotic particles in the modified Harris model of the magnetotail as a function of both the energy and the normal component of the magnetic field. For each parameter set, we launching 1000 chaotic orbits from the asymptotic region and then follow four additional orbits whose initial conditions vary by ɛ. If all 5 initial conditions scatter in the same direction, the particle is ɛ certain. We then vary ɛ over 7 order of magnitude and determine f(ɛ) as a function of ɛ. We find that the value of α takes on minimum values near discrete resonant energies and that as the normal component of the magnetic field goes to zero, α also goes to zero.
Scaling exponents of the velocity structure functions in the interplanetary medium
Directory of Open Access Journals (Sweden)
V. Carbone
Full Text Available We analyze the scaling exponents of the velocity structure functions, obtained from the velocity fluctuations measured in the interplanetary space plasma. Using the expression for the energy transfer rate which seems the most relevant in describing the evolution of the pseudo-energy densities in the interplanetary medium, we introduce an energy cascade model derived from a simple fragmentation process, which takes into account the intermittency effect. In the absence and in the presence of the large-scale magnetic field decorrelation effect the model reduces to the fluid and the hydromagnetic p-model, respectively. We show that the scaling exponents of the q-th power of the velocity structure functions, as obtained by the model in the absence of the decorrelation effect, furnishes the best-fit to the data analyzed from the Voyager 2 velocity field measurements at 8.5 AU. Our results allow us to hypothesize a new kind of scale-similarity for magnetohydrodynamic turbulence when the decorrelation effect is at work, related to the fourth-order velocity structure function.
Mechanical Behavior of 316L Stainless Steel after Strain Hardening
Directory of Open Access Journals (Sweden)
Li Kaishang
2017-01-01
Full Text Available The effects of strain hardening on the mechanical behavior of 316L stainless steel were studied in the paper. The original and different strain hardening materials were compared to investigate the mechanical behavior. The results demonstrate that the yield strengths increase with the magnitude of strain hardening significantly, but the ultimate strengths of the original and different strain hardening materials are closed. In addition, the plastic parameters of 316L stainless steel including fracture elongation and fracture surface shrinkage decrease with the magnitude of strain hardening. Finally, the Ramberg-Osgood equation is used to predict the stress-strain curves after strain hardening, and the results indicate that the predicted values agree with the experimental values.
Electrolyte-plasma hardening of circular saws
Tyulyapin, A. N.; Tyurin, Yu. N.; Traino, A. I.; Yusupov, V. S.
1998-01-01
Cold circular saws with an external diameter of 600-900 mm and a disk thickness of 5-8 mm are used for cutting measured pieces of bent shapes and pipes in lines of shaping mills. Strict requirements are imposed on the quality of the circular saws, namely, they should possess high wear resistance of the teeth and withstand the loads exerted by the cut bent shapes in the direction perpendicular to the plane of the disk. A method of electrolyte-plasma hardening of circular saws with the use of pulse heating has been developed in order to meet these requirements.
Configurable Radiation Hardened High Speed Isolated Interface ASIC Project
National Aeronautics and Space Administration — NVE Corporation will design and build an innovative, low cost, flexible, configurable, radiation hardened, galvanically isolated, interface ASIC chip set that will...
Technology Developments in Radiation-Hardened Electronics for Space Environments
Keys, Andrew S.; Howell, Joe T.
2008-01-01
The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS, Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches. System level applications for the RHESE technology products are discussed.
Hardening in Two-Phase Materials. II. Plastic Strain and Mean Stress Hardening Rate
DEFF Research Database (Denmark)
Lilholt, Hans
1977-01-01
The strain parameters which are relevant in a tensile experiment, are analysed and related to the geometry of deformation and to the mean stress of two-phase materials. The hardening rate of the mean stress with respect to plastic strain is found to be useful in comparison between experiments...
Heat Treatment Optimization and Properties Correlation for H11-Type Hot-Work Tool Steel
Podgornik, B.; Puš, G.; Žužek, B.; Leskovšek, V.; Godec, M.
2017-12-01
The aim of this research was to determine the effect of vacuum-heat-treatment process parameters on the material properties and their correlations for low-Si-content AISI H11-type hot-work tool steel using a single Circumferentially Notched and fatigue Pre-cracked Tensile Bar (CNPTB) test specimen. The work was also focused on the potential of the proposed approach for designing advanced tempering diagrams and optimizing the vacuum heat treatment and design of forming tools. The results show that the CNPTB specimen allows a simultaneous determination and correlation of multiple properties for hot-work tool steels, with the compression and bending strength both increasing with hardness, and the strain-hardening exponent and bending strain increasing with the fracture toughness. On the other hand, the best machinability and surface quality of the hardened hot-work tool steel are obtained for hardness values between 46 and 50 HRC and a fracture toughness below 60 MPa√m.
Analysis of fracture toughness of explosion-hardened martensitic steel
Moskvitina, L. V.
2015-10-01
In this work we study a shift of the following nonlinear states: tempering + abatement + 10 GPa shock loading + welding thermocycle. As a result the self-organized HAZ metal structure with elements of self-similarity on different scales is found. The fractal analysis shows how formed defects affect the HAZ metal hardness of 14H2GMR steel with the martensitic structure of static fracture. The statistical analysis of stereometric parameters of fracture shows a higher energy intensity of static fracture in specimens treated by explosion. The multifractal analysis reveals hardness of the grid dislocation structure induced by explosion in the air-hardening zone. The homogeneity of the dislocation structure related to carbides increases the resistance of HAZ metal of static fracture.
Role of work hardening characteristics of matrix alloys in the ...
Indian Academy of Sciences (India)
Unknown
verted into true stress–true strain curves. Figure 1 shows the true stress–true strain curves for different aluminium alloys viz. AA6061, AA2024, AA7010, AA2014, AA7075 and commercial purity aluminium. It is observed that commercial purity aluminium has the lowest yield strength and AA7010 has the highest yield strength.
Critical exponent for a damped wave system with fractional integral
Directory of Open Access Journals (Sweden)
Mijing Wu
2015-08-01
Full Text Available We shall present the critical exponent $$ F(p, q,\\alpha:=\\max\\big\\{\\alpha+\\frac{(\\alpha+1(p+1}{pq-1}, \\alpha+\\frac{(\\alpha+1(q+1}{pq-1}\\big\\}-\\frac{1}{2} $$ for the Cauchy problem $$\\displaylines{ u_{tt}-u_{xx}+u_t=J_{0|t}^{\\alpha}(|v|^{p}, \\quad (t,x\\in\\mathbb{R}^{+}\\times\\mathbb{R},\\cr v_{tt}-v_{xx}+v_t=J_{0|t}^{\\alpha}(|u|^{q}, \\quad (t, x\\in\\mathbb{R}^{+}\\times\\mathbb{R},\\cr (u(0,x, u_t(0,x=(u_0(x,u_1(x, \\quad x\\in \\mathbb{R},\\cr (v(0,x, v_t(0,x=(v_0(x,v_1(x, \\quad x\\in \\mathbb{R},\\cr }$$ where $p,q\\geq 1$, $pq>1$ and $0<\\alpha<1/2$; that is, the small data global existence of solutions can be derived to the problem above if $F(p, q, \\alpha<0$. Furthermore, in the case of $F(p, q, \\alpha\\geq 0$ the non-existence of global solution can be obtained with the initial data having positive average value.
A generalization of the power law distribution with nonlinear exponent
Prieto, Faustino; Sarabia, José María
2017-01-01
The power law distribution is usually used to fit data in the upper tail of the distribution. However, commonly it is not valid to model data in all the range. In this paper, we present a new family of distributions, the so-called Generalized Power Law (GPL), which can be useful for modeling data in all the range and possess power law tails. To do that, we model the exponent of the power law using a non-linear function which depends on data and two parameters. Then, we provide some basic properties and some specific models of that new family of distributions. After that, we study a relevant model of the family, with special emphasis on the quantile and hazard functions, and the corresponding estimation and testing methods. Finally, as an empirical evidence, we study how the debt is distributed across municipalities in Spain. We check that power law model is only valid in the upper tail; we show analytically and graphically the competence of the new model with municipal debt data in the whole range; and we compare the new distribution with other well-known distributions including the Lognormal, the Generalized Pareto, the Fisk, the Burr type XII and the Dagum models.
Scaling exponents in space plasmas: a fractional Levy model
Watkins, N. W.; Credgington, D.; Hnat, B.; Chapman, S. C.; Freeman, M. P.; Greenhough, J.
Mandelbrot introduced the concept of fractals to describe the non-Euclidean shape of many aspects of the natural world In the time series context he proposed the use of fractional Brownian motion fBm to model non-negligible temporal persistence the Joseph Effect and Levy flights to quantify large discontinuities the Noah Effect In space physics the effects are manifested as intermittency and long-range correlation well-established features of geomagnetic indices and their solar wind drivers In order to capture and quantify the Noah and Joseph effects in one compact model we propose the application of a bridge -fractional Levy motion fLm -to space physics We perform an initial evaluation of some previous scaling results in this paradigm and show how fLm can model the previously observed exponents physics 0509058 in press Space Science Reviews We discuss the similarities and differences between fLm and ambivalent processes based on fractional kinetic equations e g Brockmann et al Nature 2006 and suggest some new directions for the future
Hardness variability in commercial and hardened technologies
Energy Technology Data Exchange (ETDEWEB)
Shaneyfelt, M.R.; Winokur, P.S.; Meisenheimer, T.L.; Sexton, F.W.; Roeske, S.B.; Knoll, M.G.
1994-03-01
Over the past 10 years, there have been a number of advances in methods to assess and assure the radiation hardness of microelectronics in military and space applications. At the forefront of these is the Qualified Manufacturers List (QML) methodology, in which the hardness of product is ``built-in`` through statistical process control (SPC) of technology parameters relevant to the radiation response, test structure to integrated circuit (IC) correlations, and techniques for extrapolating laboratory test results to varying radiation scenarios. At the same time, there has been renewed interest in the use of commercial technology -- with its enhanced performance, reduced cost, and higher reliability -- in military and space systems. In this paper, we initially demonstrate the application of QML techniques to assure and control the radiation response of hardened technologies. Through several examples, we demonstrate intra-die, wafer-to-wafer, and lot-to-lot variations in a hardened technology. We observe 10 to 30% variations in key technology parameters that result from variability in geometry, process, and design layout. Radiation-induced degradation is seen to mirror preirradiation characteristics. We then evaluate commercial technologies and report considerably higher variability in radiation hardness, i.e., variations by a factor of two to five. This variability is shown to arise from a lack of control of technology parameters relevant to the radiation response, which a commercial manufacturer has no interest in controlling in a normal process flow.
The unitary cover of a finite group and the exponent of the Schur multiplier
Sambonet, Nicola
2013-01-01
For a finite group we introduce a particular central extension, the unitary cover, having minimal exponent among those satisfying the projective lifting property. We obtain new bounds for the exponent of the Schur multiplier relating to subnormal series, and we discover new families for which the bound is the exponent of the group. Finally, we show that unitary covers are controlled by the Zel'manov solution of the restricted Burnside problem for 2-generator groups.
Partial differential equations with variable exponents variational methods and qualitative analysis
Radulescu, Vicentiu D
2015-01-01
Partial Differential Equations with Variable Exponents: Variational Methods and Qualitative Analysis provides researchers and graduate students with a thorough introduction to the theory of nonlinear partial differential equations (PDEs) with a variable exponent, particularly those of elliptic type. The book presents the most important variational methods for elliptic PDEs described by nonhomogeneous differential operators and containing one or more power-type nonlinearities with a variable exponent. The authors give a systematic treatment of the basic mathematical theory and constructive meth
Uncertainty in vertical extrapolation of wind statistics: shear-exponent and WAsP/EWA methods
DEFF Research Database (Denmark)
Kelly, Mark C.
for uncertainties inherent in determination of (wind) shear exponents, and subsequent vertical extrapolation of wind speeds. The report further outlines application of the theory and results of Kelly & Troen (2014-6) for gauging the uncertainty inherent in use of the European Wind Atlas (EWA) / WAsP method......This report provides formulations for estimation of uncertainties involved in vertical extrapolation of winds, as well as the total uncertainty incurred when winds observed at one height are extrapolated to turbine hub height for wind resource assessment. This includes new derivations....../푧obs); for larger extrapolations, WAsP-based extrapolation leads to smaller estimated uncertainties than the shear-extrapolation method.A primary motivation for—and part of—this work is the creation of a standard for uncertainty estimation and reporting, which is known as the IEC61400-15. The author is actively...
Experimental study of self-compacted concrete in hardened state
Parra Costa, Carlos Jose
The main aim of this work is to investigate the hardened behaviour of Self-Compacting Concrete (SCC). Self compacting Concrete is a special concrete that can flow in its gravity and fill in the formwork alone to its self-weight, passing through the bars and congested sections without the need of any internal or external vibration, while maintaining adequate homogeneity. SCC avoids most of the materials defects due to bleeding or segregation. With regard to its composition, SCC consists of the same components as traditional vibrated concrete (TC), but in different proportions. Thus, the high amount of superplasticizer and high powder content have to taken into account. The high workability of SCC does not allow to use traditional methods for measuring the fresh state properties, so new tests has developed (slump-flow, V-funnel, L-box, and others). The properties of the hardened SCC, which depend on the mix design, should be different from traditional concrete. In order to study the possible modifications of SCC hardened state properties, a review of the bibliography was done. The state of art was focused on the mechanical behaviour (compressive strength, tension strength and elastic modulus), on bond strength of reinforcement steel, and on material durability. The experimental program consisted in the production of two types of concretes: Self-Compacting Concrete and Traditional Concrete. Four different dosages was made with three different water/cement ratio and two strength types of Portland cement, in order to cover the ordinary strength used in construction. Based on this study it can be concluded that compressive strength of SCC and TC are similar (the differences are lesser than 10%), whereas the tensile strength of TC are up to 18% higher. The values of elastic modulus of both concrete are similar. On the other hand, in the ultimate state the bond strength of SCC and TC is similar, although SCC shows higher bond stiffness in the serviceability state (initial
Microstructural and Mechanical Study of Press Hardening of Thick Boron Steel Sheet
Pujante, J.; Garcia-Llamas, E.; Golling, S.; Casellas, D.
2017-09-01
Press hardening has become a staple in the production of automotive safety components, due to the combination of high mechanical properties and form complexity it offers. However, the use of press hardened components has not spread to the truck industry despite the advantages it confers, namely affordable weight reduction without the use of exotic materials, would be extremely attractive for this sector. The main reason for this is that application of press hardened components in trucks implies adapting the process to the manufacture of thick sheet metal. This introduces an additional layer of complexity, mainly due to the thermal gradients inside the material resulting in though-thickness differences in austenitization and cooling, potentially resulting in complex microstructure and gradient of mechanical properties. This work presents a preliminary study on the press hardening of thick boron steel sheet. First of all, the evolution of the sheet metal during austenitization is studied by means of dilatometry tests and by analysing the effect of furnace dwell time on grain size. Afterwards, material cooled using different cooling strategies, and therefore different effective cooling rates, is studied in terms of microstructure and mechanical properties. Initial results from finite element simulation are compared to experimental results, focusing on the phase composition in through thickness direction. Results show that industrial-equivalent cooling conditions do not lead to gradient microstructures, even in extreme scenarios involving asymmetrical cooling.
Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners
Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood
2014-01-01
Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (Â±)-trans-1,2- diaminocyclohexane (DACH), were...
Hardening fertilization and nutrient loading of conifer seedlings
R. Kasten Dumroese
2003-01-01
Continuing to fertilize bareroot and container seedlings during the hardening process (from cessation of height growth until lifting) can improve seedling viability. The process of fertilizing during hardening has many names, but in the last decade a new term, nutrient loading, has come into use. The process of nutrient loading seedlings leads to luxury consumption...
Optimization of Laser Beam Transformation Hardening by One Single Parameter
Meijer, J.; van Sprang, I.
1991-01-01
The process of laser beam transformation hardening is principally controlled by two independent parameters, the absorbed laser power on a given area and the interaction time. These parameters can be transformed into two functional parameters: the maximum surface temperature and the hardening depth.
Novel SEU hardened PD SOI SRAM cell
Chengmin, Xie; Zhongfang, Wang; Xihu, Wang; Longsheng, Wu; Youbao, Liu
2011-11-01
A novel SEU hardened 10T PD SOI SRAM cell is proposed. By dividing each pull-up and pull-down transistor in the cross-coupled inverters into two cascaded transistors, this cell suppresses the parasitic BJT and source-drain penetration charge collection effect in PD SOI transistor which causes the SEU in PD SOI SRAM. Mixed-mode simulation shows that this novel cell completely solves the SEU, where the ion affects the single transistor. Through analysis of the upset mechanism of this novel cell, SEU performance is roughly equal to the multiple-cell upset performance of a normal 6T SOI SRAM and it is thought that the SEU performance is 17 times greater than traditional 6T SRAM in 45nm PD SOI technology node based on the tested data of the references. To achieve this, the new cell adds four transistors and has a 43.4% area overhead and performance penalty.
Bermudo, Carolina; Sevilla, Lorenzo; Martín, Francisco; Trujillo, Francisco Javier
2017-01-01
The application of incremental processes in the manufacturing industry is having a great development in recent years. The first stage of an Incremental Forming Process can be defined as an indentation. Because of this, the indentation process is starting to be widely studied, not only as a hardening test but also as a forming process. Thus, in this work, an analysis of the indentation process under the new Modular Upper Bound perspective has been performed. The modular implementation has several advantages, including the possibility of the introduction of different parameters to extend the study, such as the friction effect, the temperature or the hardening effect studied in this paper. The main objective of the present work is to analyze the three hardening models developed depending on the material characteristics. In order to support the validation of the hardening models, finite element analyses of diverse materials under an indentation are carried out. Results obtained from the Modular Upper Bound are in concordance with the results obtained from the numerical analyses. In addition, the numerical and analytical methods are in concordance with the results previously obtained in the experimental indentation of annealed aluminum A92030. Due to the introduction of the hardening factor, the new modular distribution is a suitable option for the analysis of indentation process. PMID:28772914
Hardening of ODS ferritic steels under irradiation with high-energy heavy ions
Ding, Z. N.; Zhang, C. H.; Yang, Y. T.; Song, Y.; Kimura, A.; Jang, J.
2017-09-01
Influence of the nanoscale oxide particles on mechanical properties and irradiation resistance of oxide-dispersion-strengthened (ODS) ferritic steels is of critical importance for the use of the material in fuel cladding or blanket components in advanced nuclear reactors. In the present work, impact of structures of oxide dispersoids on the irradiation hardening of ODS ferritic steels was studied. Specimens of three high-Cr ODS ferritic steels containing oxide dispersoids with different number density and average size were irradiated with high-energy Ni ions at about -50 °C. The energy of the incident Ni ions was varied from 12.73 MeV to 357.86 MeV by using an energy degrader at the terminal so that a plateau of atomic displacement damage (∼0.8 dpa) was produced from the near surface to a depth of 24 μm in the specimens. A nanoindentor (in constant stiffness mode with a diamond Berkovich indenter) and a Vickers micro-hardness tester were used to measure the hardeness of the specimens. The Nix-Gao model taking account of the indentation size effect (ISE) was used to fit the hardness data. It is observed that the soft substrate effect (SSE) can be diminished substantially in the irradiated specimens due to the thick damaged regions produced by the Ni ions. A linear correlation between the nano-hardeness and the micro-hardness was found. It is observed that a higher number density of oxide dispersoids with a smaller average diameter corresponds to an increased resistance to irradiation hardening, which can be ascribed to the increased sink strength of oxides/matrix interfaces to point defects. The rate equation approach and the conventional hardening model were used to analyze the influence of defect clusters on irradiation hardening in ODS ferritic steels. The numerical estimates show that the hardening caused by the interstitial type dislocation loops follows a similar trend with the experiment data.
Error Exponents of Low-Density Parity-Check Codes on the Binary Erasure Channel
Mora, Thierry; Rivoire, Olivier
2006-01-01
We introduce a thermodynamic (large deviation) formalism for computing error exponents in error-correcting codes. Within this framework, we apply the heuristic cavity method from statistical mechanics to derive the average and typical error exponents of low-density parity-check (LDPC) codes on the binary erasure channel (BEC) under maximum-likelihood decoding.
The spatial meaning of Pareto's scaling exponent of city-size distribution
Chen, Yanguang
2013-01-01
The scaling exponent of a hierarchy of cities used to be regarded as a fractal parameter. The Pareto exponent was treated as the fractal dimension of size distribution of cities, while the Zipf exponent was treated as the reciprocal of the fractal dimension. However, this viewpoint is not exact. In this paper, I will present a new interpretation of the scaling exponent of rank-size distributions. The ideas from fractal measure relation and the principle of dimension consistency are employed to explore the essence of Pareto's and Zipf's scaling exponents. The Pareto exponent proved to be a ratio of the fractal dimension of a network of cities to the average dimension of city population. Accordingly, the Zipf exponent is the reciprocal of this dimension ratio. On a digital map, the Pareto exponent can be defined by the scaling relation between a map scale and the corresponding number of cities based on this scale. The cities of the United States of America in 1900, 1940, 1960, and 1980 and Indian cities in 1981...
Variation of Zipf's exponent in one hundred live languages: A study of the Holy Bible translations
Mehri, Ali; Jamaati, Maryam
2017-08-01
Zipf's law, as a power-law regularity, confirms long-range correlations between the elements in natural and artificial systems. In this article, this law is evaluated for one hundred live languages. We calculate Zipf's exponent for translations of the holy Bible to several languages, for this purpose. The results show that, the average of Zipf's exponent in studied texts is slightly above unity. All studied languages in some families have Zipf's exponent lower/higher than unity. It seems that geographical distribution impresses the communication between speakers of different languages in a language family, and affect similarity between their Zipf's exponent. The Bible has unique concept regardless of its language, but the discrepancy in grammatical rules and syntactic regularities in applying stop words to make sentences and imply a certain concept, lead to difference in Zipf's exponent for various languages.
Hurst exponent and prediction based on weak-form efficient market hypothesis of stock markets
Eom, Cheoljun; Choi, Sunghoon; Oh, Gabjin; Jung, Woo-Sung
2008-07-01
We empirically investigated the relationships between the degree of efficiency and the predictability in financial time-series data. The Hurst exponent was used as the measurement of the degree of efficiency, and the hit rate calculated from the nearest-neighbor prediction method was used for the prediction of the directions of future price changes. We used 60 market indexes of various countries. We empirically discovered that the relationship between the degree of efficiency (the Hurst exponent) and the predictability (the hit rate) is strongly positive. That is, a market index with a higher Hurst exponent tends to have a higher hit rate. These results suggested that the Hurst exponent is useful for predicting future price changes. Furthermore, we also discovered that the Hurst exponent and the hit rate are useful as standards that can distinguish emerging capital markets from mature capital markets.
Directory of Open Access Journals (Sweden)
Gaetano eValenza
2012-02-01
Full Text Available In this work we characterized the nonlinear complexity of Heart Rate Variability (HRV in short time series. The complexity of HRV signal was evaluated during emotional visual elicitation by using Dominant Lyapunov Exponents (DLE and Approximate Entropy (ApEn. We adopted a simplified model of emotion derived from the Circumplex Model of Affects (CMA, in which emotional mechanisms are conceptualized in two dimensions by the terms of valence and arousal. Following CMA model, a set of standardized visual stimuli in terms of arousal and valence gathered from the International Affective Picture System (IAPS was administered to a group of 35 healthy volunteers. Experimental session consisted of eight sessions alternating neutral images with high arousal content images. Several works can be found in the literature showing a chaotic dynamics of HRV during rest or relax conditions. The outcomes of this work showed a clear switching mechanism between regular and chaotic dynamics when switching from neutral to arousal elicitation. Accordingly, the mean ApEn decreased with statistical significance during arousal elicitation and the DLE became negative. Results are very promising and could be profitably exploited to improve the accuracy of emotion recognition systems based on HRV time series analysis.
Energy Technology Data Exchange (ETDEWEB)
Anthony J. DeArdo; C. Isaac Garcia
2003-12-15
Conservation Research and Development/New Ultra-Low Carbon High Strength Steels with Improved Bake Hardenability for Enhanced Stretch Formability and Dent Resistance. The experimental work can be divided into four phases. In each phase, the materials were received or designed, processed and tested, to evaluate the BH increment or response, as a function of compositions and processing conditions. Microstructural characterization by various techniques was performed in order to gain insights into the mechanisms of flow stress increment by bake hardening.
KINETICS OF HARDNESS CHANGES DURING AGE-HARDENING OF SILUMIN
Directory of Open Access Journals (Sweden)
Jan Kohout
2011-10-01
Full Text Available Simple phenomenological description of age-hardening kinetics of supersaturated solid solution is presented using the sum of exponential functions with negative arguments containing rate constants, for whose temperature dependence the Arrhenius equation is used. The number of exponentials in the sum is discussed considering sufficiently accurate description as well as the number of distinguishable processes occurred during hardening. Also the limits of this approach are presented. Hardness changes of silumin during age-hardening are used for demonstration of this procedure.
Directory of Open Access Journals (Sweden)
Kanders Uldis
2017-04-01
Full Text Available We have extracted stress-strain field (SSF gradient and divergence representations from nanoindentation data sets of bulk solids often used as thin film substrates: bearing and tooling steels, silicon, glasses, and fused silica. Oscillations of the stress-strain field gradient and divergence induced in the subsurface layer by the nanoindentation have been revealed. The oscillations are especially prominent in single indentation tests at shallow penetration depths, h<100 nm, whereas they are concealed in the averaged datasets of 10 and more single tests. The amplitude of the SSF divergence oscillations decays as a sublinear power-law when the indenter approaches deeper atomic layers, with an exponent −0.9 for the steel and −0.8 for the fused silica. The oscillations are interpreted as alternating strain hardening-softening plastic deformation cycles induced in the subsurface layer under the indenter load.
Directory of Open Access Journals (Sweden)
Váňová P.
2017-06-01
Full Text Available Structures of carburized layers after the surface saturation process in gaseous, liquid or solid medium and after subsequent heat treatment (hardening and low-temperature tempering consist mainly of high carbon plate martensite with a certain portion of retained austenite. The presence of retained austenite (RA in carburized layers is mostly considered as undesirable because it decreases hardness of the hardened layer and furthermore, a spontaneous conversion to a ferritic-carbide mixture of a bainitic type, accompanied by a change of properties, dimensional instability and the local increase in internal stress with the possible formation of cracks, can occur. The proportion of retained austenite is, therefore, a significant characteristics of the quality of hardened layers. This work deals with the evaluation of the volume fraction of retained austenite in carburized layers using image analysis on metallographic images.
Energy Technology Data Exchange (ETDEWEB)
Nagashima, N.; Hayakawa, M. [National Inst. for Materials Science (NIMS), Ibaraki (Japan); Tsukada, T; Kaji, Y.; Miwa, Y. [Japan Atomic Energy Agency (JAEA), Ibaraki (Japan); Ando, M.; Nakata, K. [Japan Nuclear Energy Safety Organization (JNES), Tokyo (Japan)
2007-07-01
Stress corrosion cracking (SCC) was found in shroud and PLR piping made of low-carbon austenitic stainless steels in Japanese BWR plants. The intergranular type (IG) SCC propagated in hardened heat affected zones (HAZ) around welds. Strength behavior and local plastic deformation for a low-carbon austenitic stainless steel 316L, rolled at the reductions in area of 10, 30% at room temperature to simulate the hardened HAZ, were measured by a micro-hardness test machine and observed by atomic force microscopy (AFM), respectively. The tensile deformation at yield point (0.2% plastic strain) had given to the work-hardened 316L to simulate the plastic zone at the crack tip. It is suggested that one of the IGSCC propagation mechanism for 316L was related with the intergranular strength behavior and local plastic deformation around grain boundaries. (author)
Directory of Open Access Journals (Sweden)
Jr-Chuan Huang
Full Text Available The exponent decay in landslide frequency-area distribution is widely used for assessing the consequences of landslides and with some studies arguing that the slope of the exponent decay is universal and independent of mechanisms and environmental settings. However, the documented exponent slopes are diverse and hence data processing is hypothesized for this inconsistency. An elaborated statistical experiment and two actual landslide inventories were used here to demonstrate the influences of the data processing on the determination of the exponent. Seven categories with different landslide numbers were generated from the predefined inverse-gamma distribution and then analyzed by three data processing procedures (logarithmic binning, LB, normalized logarithmic binning, NLB and cumulative distribution function, CDF. Five different bin widths were also considered while applying LB and NLB. Following that, the maximum likelihood estimation was used to estimate the exponent slopes. The results showed that the exponents estimated by CDF were unbiased while LB and NLB performed poorly. Two binning-based methods led to considerable biases that increased with the increase of landslide number and bin width. The standard deviations of the estimated exponents were dependent not just on the landslide number but also on binning method and bin width. Both extremely few and plentiful landslide numbers reduced the confidence of the estimated exponents, which could be attributed to limited landslide numbers and considerable operational bias, respectively. The diverse documented exponents in literature should therefore be adjusted accordingly. Our study strongly suggests that the considerable bias due to data processing and the data quality should be constrained in order to advance the understanding of landslide processes.
Setty, V.; Sharma, A.
2013-12-01
Characterization of extreme conditions of space weather is essential for potential mitigation strategies. The non-equilibrium nature of magnetosphere makes such efforts complicated and new techniques to understand its extreme event distribution are required. The heavy tail distribution in such systems can be a modeled using Stable distribution whose stability parameter is a measure of scaling in the cumulative distribution and is related to the Hurst exponent. This exponent can be readily measured in stationary time series using several techniques and detrended fluctuation analysis (DFA) is widely used in the presence of non-stationarities. However DFA has severe limitations in cases with non-linear and atypical trends. We propose a new technique that utilizes nonlinear dynamical predictions as a measure of trends and estimates the Hurst exponents. Furthermore, such a measure provides us with a new way to characterize predictability, as perfectly detrended data have no long term memory akin to Gaussian noise Ab initio calculation of weekly Hurst exponents using the auroral electrojet index AL over a span of few decades shows that these exponents are time varying and so is its fractal structure. Such time series data with time varying Hurst exponents are modeled well using multifractional Brownian motion and it is shown that DFA estimates a single time averaged value for Hurst exponent in such data. Our results show that using time varying Hurst exponent structure, we can (a) Estimate stability parameter, -a measure of scaling in heavy tails, (b) Define and identify epochs when the magnetosphere switches between regimes with and without extreme events, and, (c) Study the dependence of the Hurst exponents on the solar activity.
Numerical model of phase transformation of steel C80U during hardening
Directory of Open Access Journals (Sweden)
T. Domański
2007-12-01
Full Text Available The article concerns numerical modelling of the phase transformations in solid state hardening of tool steel C80U. The transformations were assumed: initial structure – austenite, austenite – perlite, bainite and austenite – martensite. Model for evaluation of fractions of phases and their kinetics based on continuous heating diagram (CHT and continuous cooling diagram (CCT. The dilatometric tests on the simulator of thermal cycles were performed. The results of dilatometric tests were compared with the results of the test numerical simulations. In this way the derived models for evaluating phase content and kinetics of transformations in heating and cooling processes were verified. The results of numerical simulations confirm correctness of the algorithm that were worked out. In the numerical example the simulated estimation of the phase fraction in the hardened axisimmetrical element was performed.
Energy Technology Data Exchange (ETDEWEB)
Bastawros, A.F. [Harvard Univ., Cambridge, MA (United States). Div. of Engineering and Applied Sciences; Kim, K.S. [Brown Univ., Providence, RI (United States). Div. of Engineering
1999-08-01
The incremental in-plane Green-Lagrange strain tensor was measured near a stationary crack tip in a cyclically work-hardened copper single crystal. Measurements were made on the surface of a four-point bend specimen, using a finite-deformation laser moire interferometer. The measurement showed the existence of a narrow asymptotic field beyond a distance of 300 {micro}m from the crack tip. The inner boundary of the asymptotic zone was almost fixed at a characteristic distance ahead of the crack tip. This length scale is thought to arise from a microstructural evolution near the crack tip. The inhomogeneous hardening due to glide-band clustering and patchy slip in a small volume near the crack tip triggered such an evolution. The outer boundary of the asymptotic zone radially grew with the increasing load. The deformation field was found to be very sensitive to additional mode II loading.
A procedure for hardening steel 45 by plastic deformation using a simple roller
Directory of Open Access Journals (Sweden)
Tomás Fernández Columbíe
2010-04-01
Full Text Available This work presents the techniques used in an experimental design leading to evaluating the behaviour of an indepen-dent variable force (P, ranging from 500 up to 2500 N, 27 minimum revolution number (n, average 54 and maxi-mum 110 rev/min and 0.075, 0, 125 and 0.25 mm/rev advance for determining the dependent hardness (H pa-ttern when AISI 1045 steel test tubes were subjected to surface rolling for creating a compressive state deforming and increasing its resistance to abrasive wear and fatigue. The variables involved in the process were statistically a-nalysed, revealing increased hardness ranging from 220 up to 262 HV. Optical microscopy was used for analysing the effect of hardening caused by deformation, establishing a mechanism for hardening steel by the elements in the crystalline network sliding due to burnishing.
DEFF Research Database (Denmark)
Wu, Min; Johannesson, Björn; Geiker, Mette Rica
2014-01-01
Water vapor sorption can be used to study important properties of porous materials including specific surface area and pore size distribution (PSD). However, the data analysis is somewhat inconsistent in literature. In this work, the important factors influencing the analyzed results using sorption...... data were reviewed. Water vapor sorption measurements were then applied to two hardened cement pastes and one model porous material MCM-41. The specific surface area was calculated based on different equations accounting for multilayer adsorption and the PSD was analyzed from both the absorption...... and the desorption isotherms for comparison: The calculated specific surface area was quite dependent on which equation is considered for multilayer adsorption. For the studied hardened cement pastes, three characteristic peaks were found in the calculated PSD curves from the desorption isotherms with corresponding...
Medios de enfriamiento para el temple // Means for Cooling During the Hardening Process
Directory of Open Access Journals (Sweden)
N. Caballero Stevens
1999-07-01
Full Text Available Los factores que rigen el proceso de temple son la temperatura, el tiempo de calentamiento y la velocidad de enfriamiento.Tradicionalmente, la variación de la velocidad de enfriamiento se ha logrado mediante la utilización de diferentes medios como elagua, aceites minerales, aceites orgánicos, metales fundidos y otros.En este trabajo, se presentan las características fundamentales de los medios convencionales y actuales empleados para elenfriamiento durante el temple.Palabras claves: Endurecimiento superficial, temple superficial, medios de enfriamiento._____________________________________________________________________AbstractFactors governing of the hardening process are temperature, heating time and cooling speed. Traditionally, the variation of thecooling time has been achieved by using different means such as water, mineral oils, molten metals, etc.In this work, the fundamental characteristics of the conventional and modern means developed for cooling during the hardeningprocess are presented.Key words: Hardening process, cooling means.
Open Source Radiation Hardened by Design Technology
Shuler, Robert
2016-01-01
The proposed technology allows use of the latest microcircuit technology with lowest power and fastest speed, with minimal delay and engineering costs, through new Radiation Hardened by Design (RHBD) techniques that do not require extensive process characterization, technique evaluation and re-design at each Moore's Law generation. The separation of critical node groups is explicitly parameterized so it can be increased as microcircuit technologies shrink. The technology will be open access to radiation tolerant circuit vendors. INNOVATION: This technology would enhance computation intensive applications such as autonomy, robotics, advanced sensor and tracking processes, as well as low power applications such as wireless sensor networks. OUTCOME / RESULTS: 1) Simulation analysis indicates feasibility. 2)Compact voting latch 65 nanometer test chip designed and submitted for fabrication -7/2016. INFUSION FOR SPACE / EARTH: This technology may be used in any digital integrated circuit in which a high level of resistance to Single Event Upsets is desired, and has the greatest benefit outside low earth orbit where cosmic rays are numerous.
Role of Strain-Hardening Law on the Bursting Speed of a Rotating Thin-Walled Shaft
Güven, U.
2009-02-01
In the present work, the bursting speed of a rotating thin-walled shaft is considered. Under usual assumptions, the roles of modified Ludwik and Ramberg-Osgood stress-strain laws on the bursting speed are discussed. It can be seen from the present analysis that the strain hardening law plays a significant role.
Chaos and stiffness exponents for short-range Gaussian Ising spin glasses
Almeida, Sebastião T. O.; Curado, Evaldo M. F.; Nobre, Fernando D.
2013-06-01
Two important exponents in spin-glass theory, namely, the chaos (ζ) and stiffness (y) exponents, are studied for Ising spin glasses with nearest-neighbor Gaussian interactions on different approaches to Bravais lattices. We consider hierarchical lattices of the Migdal-Kadanoff type (both diamond and tress families), with varying fractal dimensions, as well as two lattices of the Wheatstone-bridge family, more specifically, those with fractal dimensions D ≈ 2.32 and D ≈ 3.58. Whenever it is possible to compare, our estimates agree with those obtained from extensive numerical simulations on Bravais lattices, suggesting the present results represent good approximations for these exponents.
Radiation Hardened Ethernet PHY and Switch Fabric Project
National Aeronautics and Space Administration — Innoflight will develop a new family of radiation hardened (up to 3 Mrad(Si)), fault-tolerant, high data-rate (up to 8 Gbps), low power Gigabit Ethernet PHY and...
Technologies Enabling Custom Radiation-Hardened Component Development Project
National Aeronautics and Space Administration — Two primary paths are available for the creation of a Rad-Hard ASIC. The first approach is to use a radiation hardened process such as existing Rad-Hard foundries....
Microscopic Origin of Strain Hardening in Methane Hydrate.
Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi
2016-03-24
It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon.
Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory Project
National Aeronautics and Space Administration — Space Micro proposes to build a radiation hardened by design (RHBD) flash memory, using a modified version of our RH-eDRAM Memory Controller to solve all the single...
Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory Project
National Aeronautics and Space Administration — Radiation hardened nonvolatile memories for space is still primarily confined to EEPROM. There is high density effective or cost effective NVM solution available to...
Strain Hardening of Polymer Glasses: Entanglements, Energetics, and Plasticity
Hoy, Robert S.; Robbins, Mark O.
2007-01-01
Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are ...
Microscopic Origin of Strain Hardening in Methane Hydrate
Jihui Jia; Yunfeng Liang; Takeshi Tsuji; Sumihiko Murata; Toshifumi Matsuoka
2016-01-01
It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to ...
Energy Technology Data Exchange (ETDEWEB)
Gonzales, Gilberto S. [Acos Ipanema Villares, Sorocaba, SP (Brazil); Cupini, Nivaldo L. [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica
1992-12-31
Some experiments were carried out to analyse the influence of work hardening over machinability of SAE 12L14 steel bars. The results showed that the work hardening always produces smaller machinability index than the hot roller condition. Also, the work analyses some metallurgical parameters such as hardness, ductibility, micro inclusions and their influence over the machinability. (author). 11 refs., 6 figs., 4 tabs.
Press-Hardening Simulation - the next Level of Maturity
Schönbach, T.; Messner, M.; Gmainer, C.
2017-09-01
Press hardening has been fully established in the automotive industry during the last years. Forming simulation is an important tool to make the whole potential of press hardening available in both, the mass production and further developments. One of the usual simulation packages is AutoForm. It has been known as a reliable software tool for the sheet metal forming application area as well as for the press hardening for years. AutoForm-Thermo Solverplus supports direct and indirect hot forming, which are followed by quenching and cooling processes. It takes into account phase transformation during quenching and thermal distortion after cooling. The recent version AutoFormplus R7 brings further advances in process modeling for hot forming as this release allows users to take into account cooling channels. Based on this, the heat conduction in tools can be calculated. Cooling channel modelling affects press hardening simulation in two ways: it can be used to optimize the cooling channel design in the press hardening tools and it increases the accuracy level of the simulation in general. The resulting benefits coming from these new features will be presented in this paper; based on a B-pillar which was produced with direct press-hardening process.
The Ångström Exponent and Turbidity of Soot Component in the ...
African Journals Online (AJOL)
AOD) show a relatively higher value indicating a polluted ... Keywords: Soot, Ångström exponent, Turbidity, Radiative forcing, Aerosols ..... scattering For UV wavelength g typically falls between 0.6 .... total ozone content from the spectral variation.
NINJA: a noninvasive framework for internal computer security hardening
Allen, Thomas G.; Thomson, Steve
2004-07-01
Vulnerabilities are a growing problem in both the commercial and government sector. The latest vulnerability information compiled by CERT/CC, for the year ending Dec. 31, 2002 reported 4129 vulnerabilities representing a 100% increase over the 2001 [1] (the 2003 report has not been published at the time of this writing). It doesn"t take long to realize that the growth rate of vulnerabilities greatly exceeds the rate at which the vulnerabilities can be fixed. It also doesn"t take long to realize that our nation"s networks are growing less secure at an accelerating rate. As organizations become aware of vulnerabilities they may initiate efforts to resolve them, but quickly realize that the size of the remediation project is greater than their current resources can handle. In addition, many IT tools that suggest solutions to the problems in reality only address "some" of the vulnerabilities leaving the organization unsecured and back to square one in searching for solutions. This paper proposes an auditing framework called NINJA (acronym for Network Investigation Notification Joint Architecture) for noninvasive daily scanning/auditing based on common security vulnerabilities that repeatedly occur in a network environment. This framework is used for performing regular audits in order to harden an organizations security infrastructure. The framework is based on the results obtained by the Network Security Assessment Team (NSAT) which emulates adversarial computer network operations for US Air Force organizations. Auditing is the most time consuming factor involved in securing an organization's network infrastructure. The framework discussed in this paper uses existing scripting technologies to maintain a security hardened system at a defined level of performance as specified by the computer security audit team. Mobile agents which were under development at the time of this writing are used at a minimum to improve the noninvasiveness of our scans. In general, noninvasive
Zinc coated sheet steel for press hardening
Ghanbari, Zahra N.
Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time
Mohan, Nisha
Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of
Electromagnetic scattering on fractional Brownian surfaces and estimation of the Hurst exponent
Guérin, Charles-Antoine; Saillard, Marc
2001-01-01
International audience; Fractional Brownian motion is known to be a realistic model for many natural rough surfaces. It is defined by means of a single parameter, the Hurst exponent, which determines the fractal characteristics of the surface. We propose a method to estimate the Hurst exponent of a fractional Brownian profile from the electromagnetic scattering data. The method is developed in the framework of three usual approximations, with different domains of validity: the Kirchhoff appro...
The recipients of Polish, Greek and Cypriot legal norms. Linguistic exponents
Gortych-Michalak, Karolina
2014-01-01
The paper is dedicated to highlighting and indicating linguistic exponents used for needs to express the recipients of legal rules, which are present in Polish, Greek and Cypriot normative acts. The thesis of the investigation is the suspicion of designation or denotation or different relations existing between linguistic exponents referring to the recipients of legal rules and the real recipients of legal rules. Before the empirical investigations are conducted, some characteristics of legal...
Zeta function for the Lyapunov exponent of a product of random matrices
Energy Technology Data Exchange (ETDEWEB)
Mainieri, R. (Neils Bohr Institute, Blegdamsvej 17, Copenhagen O, 2100 (Denmark) Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))
1992-03-30
A cycle expansion for the Lyapunov exponent of a product of random matrices is derived. The formula is nonperturbative and numerically effective, which allows the Lyapunov exponent to be computed to high accuracy. In particular, the free energy and heat capacity are computed for the one-dimensional Ising model with quenched disorder. The formula is derived by using a Bernoulli dynamical system to mimic the randomness.
Error exponents for quantum channels with constrained inputs
Holevo, A. S.; Sohma, M.; Hirota, O.
2000-12-01
The purpose of this work is the study of the error probability for quantum channels with infinite (continuous) alphabets and additive constraints onto the input signal. We derive the lower bounds for the reliability function of such channels in terms of quantum Gallager's functions and compute them for quantum Gaussian channels.
High-Performance, Radiation-Hardened Electronics for Space Environments
Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.
2007-01-01
The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog
Application of largest Lyapunov exponent analysis on the studies of dynamics under external forces
Odavić, Jovan; Mali, Petar; Tekić, Jasmina; Pantić, Milan; Pavkov-Hrvojević, Milica
2017-06-01
Dynamics of driven dissipative Frenkel-Kontorova model is examined by using largest Lyapunov exponent computational technique. Obtained results show that besides the usual way where behavior of the system in the presence of external forces is studied by analyzing its dynamical response function, the largest Lyapunov exponent analysis can represent a very convenient tool to examine system dynamics. In the dc driven systems, the critical depinning force for particular structure could be estimated by computing the largest Lyapunov exponent. In the dc+ac driven systems, if the substrate potential is the standard sinusoidal one, calculation of the largest Lyapunov exponent offers a more sensitive way to detect the presence of Shapiro steps. When the amplitude of the ac force is varied the behavior of the largest Lyapunov exponent in the pinned regime completely reflects the behavior of Shapiro steps and the critical depinning force, in particular, it represents the mirror image of the amplitude dependence of critical depinning force. This points out an advantage of this technique since by calculating the largest Lyapunov exponent in the pinned regime we can get an insight into the dynamics of the system when driving forces are applied. Additionally, the system is shown to be not chaotic even in the case of incommensurate structures and large amplitudes of external force, which is a consequence of overdampness of the model and the Middleton's no passing rule.
Effect of crystallographic texture and dislocation hardening on limit strain in sheet metal forming
Wen, Xiyu
2000-10-01
In the metal industry, sheet metals are widely used to produce packaging materials for consumer goods, for structures such as automobilse, and for building construction and transportation. The desired shape of the products is imparted by plastic deformation in either the cold or hot state. Traditionally, the prediction of the forming limit of sheet metals is based on tensile tests, simulation tests and continuum mathematical models. Continuum models used in the prediction of the plastic behavior of sheet metals are based on average values of mechanical properties such as elongation, yield strength, work hardening and work-hardening rate, which are usually derived from tensile tests. Although attempts have been made to abandon the phenomenological description of the yield function by applying the theory of crystal plasticity to calculate the yield surface of texture polycrystals and hence the limit strains, only the average properties of the microstructure (e.g., the crystallographic texture of the bulk sheet) have been taken into account. So far, there has been no model for the prediction of the strain path and the limit strain of sheet metals that takes into account the effect of individual grain orientation and the dislocation property. In this thesis, different approaches in the study of plastic deformation are reviewed from the view-point of both macroplasticity and microplasticity. Instead of relying on a unique flow rule to describe the stress and strain relationship, the role of work hardening in the instability process of sheet metal and hence the flow localization phenomenon is explored from a study of the changes in the orientation of the constituent crystallites and from the changes in the dislocation density associated with different grain orientations during the course of large biaxial deformation. The changes in the crystallographic textures of an aluminium sheet sample deformed under various stress states from plane-strain tension to equi
Mancilla Canales, M. A.; Leguto, A. J.; Riquelme, B. D.; León, P. Ponce de; Bortolato, S. A.; Korol, A. M.
2017-12-01
Ektacytometry techniques quantifies red blood cells (RBCs) deformability by measuring the elongation of suspended RBCs subjected to shear stress. Raw shear stress elongation plots are difficult to understand, thus most research papers apply data reduction methods characterizing the relationship between curve fitting. Our approach works with the naturally generated photometrically recorded time series of the diffraction pattern of several million of RBCs subjected to shear stress, and applies nonlinear quantifiers to study the fluctuations of these elongations. The development of new quantitative methods is crucial for restricting the subjectivity in the study of the cells behavior, mainly if they are capable of analyze at the same time biological and mechanical aspects of the cells in flowing conditions and compare their dynamics. A patented optical system called Erythrocyte Rheometer was used to evaluate viscoelastic properties of erythrocytes by Ektacytometry. To analyze cell dynamics we used the technique of Time Delay Coordinates, False Nearest Neighbors, the forecasting procedure proposed by Sugihara and May, and Hurst exponent. The results have expressive meaning on comparing healthy samples with parasite treated samples, suggesting that apparent noise associated with deterministic chaos can be used not only to distinguish but also to characterize biological and mechanical aspects of cells at the same time in flowing conditions.
Characteristic distribution of finite-time Lyapunov exponents for chimera states
Botha, André E.
2016-01-01
Our fascination with chimera states stems partially from the somewhat paradoxical, yet fundamental trait of identical, and identically coupled, oscillators to split into spatially separated, coherently and incoherently oscillating groups. While the list of systems for which various types of chimeras have already been detected continues to grow, there is a corresponding increase in the number of mathematical analyses aimed at elucidating the fundamental reasons for this surprising behaviour. Based on the model systems, there are strong indications that chimera states may generally be ubiquitous in naturally occurring systems containing large numbers of coupled oscillators – certain biological systems and high-Tc superconducting materials, for example. In this work we suggest a new way of detecting and characterising chimera states. Specifically, it is shown that the probability densities of finite-time Lyapunov exponents, corresponding to chimera states, have a definite characteristic shape. Such distributions could be used as signatures of chimera states, particularly in systems for which the phases of all the oscillators cannot be measured directly. For such cases, we suggest that chimera states could perhaps be detected by reconstructing the characteristic distribution via standard embedding techniques, thus making it possible to detect chimera states in systems where they could otherwise exist unnoticed. PMID:27374473
A brief review of cavity swelling and hardening in irradiated copper and copper alloys
Energy Technology Data Exchange (ETDEWEB)
Zinkle, S.J.
1990-01-01
The literature on radiation-induced swelling and hardening in copper and its alloy is reviewed. Void formation does not occur during irradiation of copper unless suitable impurity atoms such as oxygen or helium are present. Void formation occurs for neutron irradiation temperatures of 180 to 550{degree}C, with peak swelling occurring at {approximately}320{degree}C for irradiation at a damage rate of 2 {times} 10{sup {minus}7} dpa/s. The post-transient swelling rate has been measured to be {approximately}0.5%/dpa at temperatures near 400{degree}C. Dispersion-strengthened copper has been found to be very resistant to void swelling due to the high sink density associated with the dispersion-stabilized dislocation structure. Irradiation of copper at temperatures below 400{degree}C generally causes an increase in strength due to the formation of defect clusters which inhibit dislocation motion. The radiation hardening can be adequately described by Seeger's dispersed barrier model, with a barrier strength for small defect clusters of {alpha} {approx} 0.2. The radiation hardening apparently saturates for fluences greater than {approximately}10{sup 24} n/m{sup 2} during irradiation at room temperature due to a saturation of the defect cluster density. Grain boundaries can modify the hardening behavior by blocking the transmission of dislocation slip bands, leading to a radiation- modified Hall-Petch relation between yield strength and grain size. Radiation-enhanced recrystallization can lead to softening of cold-worked copper alloys at temperatures above 300{degree}C.
DEFF Research Database (Denmark)
Bottoli, Federico; Winther, Grethe; Christiansen, Thomas L.
2015-01-01
Precipitation hardening martensitic stainless steel Nanoflex was low-temperature nitrided or nitrocarburized. In these treatments, simultaneous hardening of the bulk, by precipitation hardening, and the surface by dissolving nitrogen/carbon can be obtained because the treatment temperatures and t...
Energy Technology Data Exchange (ETDEWEB)
Shikhaliev, Polad M [Department of Radiological Sciences, University of California, Irvine, CA 92697 (United States)
2005-12-21
Photon counting x-ray imaging provides efficient rejection of the electronics noise, no pulse height (Swank) noise, less noise due to optimal photon energy weighting and the possibility of energy resolved image acquisition. These advantages apply also to CT when projection data are acquired using a photon counting detector. However, photon counting detectors assign a weighting factor of 1 to all detected photons whereas the weighting factor of a charge integrating detector is proportional to the energy of the detected photon. Therefore, data collected by photon counting and charge integrating detectors represent the 'hardening' of the photon beam passed through the object differently. This affects the beam hardening artefacts in the reconstructed CT images. This work represents the first comparative evaluation of the effect of photon counting, charge integrating and energy weighting photon detectors on beam hardening artefacts in CT. Beam hardening artefacts in CT images were evaluated for 20 cm and 14 cm diameter water cylinders with bone and low contrast inserts, at 120 kVp and 90 kVp x-ray tube voltages, respectively. It was shown that charge integrating results in 1.8% less beam hardening artefacts from bone inserts (i.e., CT numbers in the 'shadow' of the bone are less by 1.8% as compared to CT numbers over the periphery of the image), as compared to photon counting. However, optimal photon energy weighting, which provides highest SNR, results in 7.7% higher beam hardening artefacts from bone inserts as compared to photon counting. The magnitude of the 'cupping' artefacts was lower by 1% for charge integrating and higher by 6.1% for energy weighting acquisitions as compared to photon counting. Only the photon counting systems provide an accurate representation of the beam hardening effect due to its flat energy weighting. Because of their energy dependent weighting factors, the charge integrating and energy weighting systems do
Influence of Hardening Model on Weld Residual Stress Distribution
Energy Technology Data Exchange (ETDEWEB)
Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))
2009-06-15
This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a
Higgs critical exponents and conformal bootstrap in four dimensions
Energy Technology Data Exchange (ETDEWEB)
Antipin, Oleg [INFN, Sezione di Firenze,Via G. Sansone 1, I-50019 Sesto Fiorentino (Italy); Mølgaard, Esben; Sannino, Francesco [CP-Origins & the Danish Institute for Advanced Study Danish IAS,University of Southern Denmark,Campusvej 55, DK-5230 Odense M (Denmark)
2015-06-04
We investigate relevant properties of composite operators emerging in nonsupersymmetric, four-dimensional gauge-Yukawa theories with interacting conformal fixed points within a precise framework. The theories investigated in this work are structurally similar to the standard model of particle interactions, but differ by developing perturbative interacting fixed points. We investigate the physical properties of the singlet and the adjoint composite operators quadratic in the Higgs field, and discover, via a direct computation, that the singlet anomalous dimension is substantially larger than the adjoint one. The numerical bootstrap results are, when possible, compared to our precise findings associated to the four dimensional conformal field theoretical results. To accomplish this, it was necessary to calculate explicitly the crossing symmetry relations for the global symmetry group SU(N)×SU(N).
DISTRIBUTED EXTERNAL SURFACE HARDENING OF CAR DESIGN BY WINDING
Directory of Open Access Journals (Sweden)
O. V. Fomin
2017-04-01
Full Text Available Purpose. The paper involves coverage of features and results of the research conducted by the authors to determine the feasibility and establishment of pre-stressed-strained state of freight cars by winding in order to improve their strength characteristics. It is also necessary to present the theoretical justification for the effectiveness of the application of this method for car designs and an appropriate example for the tank-car. Methodology. The conducted study is based on an analysis of known works on the subject, mathematical justification and computer modeling. At the calculations of rolling stock components contemporary conventional techniques were used. Findings. Authors found that the winding method for pre-stressed-strained state is effective and appropriate for use in the construction of railway rolling stock and, in particular freight cars. Freight car designs with the pre-stressed-strained state are characterized by a number of strength advantages, among which there is an improvement of the work on the perception of operational loads and resource conservation. Originality. For the first time it is proposed the improvement of bearing capacity of freight car constructions through the creation of its component in the directed stress-strained state. It is also for the first time proposed the use of distributed external surface hardening by the method of winding to create a pre-stress-strained state of structural components of freight cars. The methods for winding designs of freight cars and their implementation were considered. Practical value. The studies developed a number of technical solutions for improving the design of freight cars and tank-container, which has been patented. Corresponding solutions for the tank-car are partially presented. Practical implementation of such solutions will significantly improve the technical, economic and operational performances of car designs.
A bodyweight-dependent allometric exponent for scaling clearance across the human life-span.
Wang, Chenguang; Peeters, Mariska Y M; Allegaert, Karel; Blussé van Oud-Alblas, Heleen J; Krekels, Elke H J; Tibboel, Dick; Danhof, Meindert; Knibbe, Catherijne A J
2012-06-01
To explore different allometric equations for scaling clearance across the human life-span using propofol as a model drug. Data from seven previously published propofol studies ((pre)term neonates, infants, toddlers, children, adolescents and adults) were analysed using NONMEM VI. To scale clearance, a bodyweight-based exponential equation with four different structures for the exponent was used: (I) 3/4 allometric scaling model; (II) mixture model; (III) bodyweight-cut-point separated model; (IV) bodyweight-dependent exponent model. Model I adequately described clearance in adults and older children, but overestimated clearance of neonates and underestimated clearance of infants. Use of two different exponents in Model II and Model III showed significantly improved performance, but yielded ambiguities on the boundaries of the two subpopulations. This discontinuity was overcome in Model IV, in which the exponent changed sigmoidally from 1.35 at a hypothetical bodyweight of 0 kg to a value of 0.56 from 10 kg onwards, thereby describing clearance of all individuals best. A model was developed for scaling clearance over the entire human life-span with a single continuous equation, in which the exponent of the bodyweight-based exponential equation varied with bodyweight.
Investigation of magnesium oxychloride cement at the initial hardening stage
Directory of Open Access Journals (Sweden)
Averina Galina
2018-01-01
Full Text Available The paper investigates the process of variation of magnesium oxychloride cement deformations at the initial hardening stage depending on the activity of magnesium oxide powder which is determined by the parameters of the source material burning. Investigation is focused on magnesium cements obtained from pure magnesium hydroxide. Source materials were burnt at various temperatures with the purpose to obtain magnesium oxide powder with different activity. Regular content of hydrated phases was determined in hardened magnesium cement prepared on the basis of binders with different activity. The study reveals the influence of magnesium oxide powder activity on the process of deformation occurrence in hardened magnesium cement and its tendency to crack formation.
THE MACHINING OF HARDENED CARBON STEELS BY COATED CUTTING TOOLS
Directory of Open Access Journals (Sweden)
Yusuf ŞAHİN
2001-02-01
Full Text Available The investigation of machining AISI 1050 carbon steels hardened to the 60 HRC hardness was carried out to determine the tool life and wear behaviour of the various cutting tools under different conditions. These experiments were conducted at using coated ceramic cutting tools and carbide cutting tools. The experimental results showed that the coated ceramic tools exhibited better performance than those of the coated carbide tools when machining the hardened steels. Moreover, wear behaviour of cutting tools were investigated in a scanning electron microscope. Electron microscopic examination also indicated that flank wear, thermal cracks on the tool nose combined with the nose deformation on the tools were responsible for the wear behaviour of the ceramic tools. For the carbide tools, however, removal of coated material from the substrate tool and combined with the crater wear were effective for the machining the hardened steel.
Strain hardening in polymer glasses: limitations of network models.
Hoy, Robert S; Robbins, Mark O
2007-09-14
Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.
Temperature influence on water transport in hardened cement pastes
Energy Technology Data Exchange (ETDEWEB)
Drouet, Emeline [CEA, DEN, DPC, SECR, Laboratoire d' Etude du Comportement des Bétons et des Argiles, F-91191 Gif sur Yvette Cedex (France); Poyet, Stéphane, E-mail: stephane.poyet@cea.fr [CEA, DEN, DPC, SECR, Laboratoire d' Etude du Comportement des Bétons et des Argiles, F-91191 Gif sur Yvette Cedex (France); Torrenti, Jean-Michel [Université Paris-Est, IFSTTAR, Département Matériaux & Structures, 14-52 boulevard Newton, F-77447 Marne la Vallée cedex 2 (France)
2015-10-15
Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.
Microstructure and properties of cast iron after laser surface hardening
Directory of Open Access Journals (Sweden)
Stanislav
2013-12-01
Full Text Available Laser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance.
Temperature Development during Hardening of Large Concrete Cubes
DEFF Research Database (Denmark)
Sørensen, Eigil V.; Burcharth, Hans Falk
The purpose ofthe project is to verify ifthermal cracking will occur in large unreinforced concrete cubes due to large temperature differences during hardening o f the concrete. The first part o f the project is to numerically simulate the temperature development during hardening, evaluate the risk...... of thermally induced cracking under varying execution conditions, and verify the temperature calculations by carrying out measurements in situ. The cubes are cast and cured under marine environmental conditions in the north western part of Spain and are to serve as coastal proteetion in a harbour under...
Aspect-oriented security hardening of UML design models
Mouheb, Djedjiga; Pourzandi, Makan; Wang, Lingyu; Nouh, Mariam; Ziarati, Raha; Alhadidi, Dima; Talhi, Chamseddine; Lima, Vitor
2015-01-01
This book comprehensively presents a novel approach to the systematic security hardening of software design models expressed in the standard UML language. It combines model-driven engineering and the aspect-oriented paradigm to integrate security practices into the early phases of the software development process. To this end, a UML profile has been developed for the specification of security hardening aspects on UML diagrams. In addition, a weaving framework, with the underlying theoretical foundations, has been designed for the systematic injection of security aspects into UML models. The
New Stainless Steel Alloys for Low Temperature Surface Hardening?
DEFF Research Database (Denmark)
Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Somers, Marcel A. J.
2015-01-01
The present contribution showcases the possibility for developing new surface hardenable stainless steels containing strong nitride/carbide forming elements (SNCFE). Nitriding of the commercial alloys, austenitic A286, and ferritic AISI 409 illustrates the beneficial effect of having SNCFE present...... in the stainless steel alloys. The presented computational approach for alloy design enables “screening” of hundreds of thousands hypothetical alloy systems by use of Thermo-Calc. Promising compositions for new stainless steel alloys can be selected based on imposed criteria, i.e. facilitating easy selection...... of candidate alloys designed for low temperature surface hardening....
Impact of Scaled Technology on Radiation Testing and Hardening
LaBel, Kenneth A.; Cohn, Lewis M.
2005-01-01
This presentation gives a brief overview of some of the radiation challenges facing emerging scaled digital technologies with implications on using consumer grade electronics and next generation hardening schemes. Commercial semiconductor manufacturers are recognizing some of these issues as issues for terrestrial performance. Looking at means of dealing with soft errors. The thinned oxide has indicated improved TID tolerance of commercial products hardened by "serendipity" which does not guarantee hardness or say if the trend will continue. This presentation also focuses one reliability implications of thinned oxides.
INFLUENCE OF MICROALLOYING BY BORON ON HARDENABILITY OF STEEL
Directory of Open Access Journals (Sweden)
E. P. Baradyntseva
2016-01-01
Full Text Available The research conducted in laboratory of metallurgical science by which the factors exerting impact on hardenability of steel microalloyed by boron were analysed. The research was made because the implementation of this process in mass production is connected with the certain difficulties. The conducted researches have allowed to draw a conclusion that changing content of various chemical elements, such as nitrogen, boron, the titan and aluminum in steel containing boron, produced by JSC «BSW – Management Company of Holding «BMC» at the stage of preparation of chart flowsheet make it possible to predict terms of hardenability of the final product.
Radiation Hardened 10BASE-T Ethernet Physical Layer (PHY)
Lin, Michael R. (Inventor); Petrick, David J. (Inventor); Ballou, Kevin M. (Inventor); Espinosa, Daniel C. (Inventor); James, Edward F. (Inventor); Kliesner, Matthew A. (Inventor)
2017-01-01
Embodiments may provide a radiation hardened 10BASE-T Ethernet interface circuit suitable for space flight and in compliance with the IEEE 802.3 standard for Ethernet. The various embodiments may provide a 10BASE-T Ethernet interface circuit, comprising a field programmable gate array (FPGA), a transmitter circuit connected to the FPGA, a receiver circuit connected to the FPGA, and a transformer connected to the transmitter circuit and the receiver circuit. In the various embodiments, the FPGA, transmitter circuit, receiver circuit, and transformer may be radiation hardened.
Stochastic model of Zipf's law and the universality of the power-law exponent.
Yamamoto, Ken
2014-04-01
We propose a stochastic model of Zipf's law, namely a power-law relation between rank and size, and clarify as to why a specific value of its power-law exponent is quite universal. We focus on the successive total of a multiplicative stochastic process. By employing properties of a well-known stochastic process, we concisely show that the successive total follows a stationary power-law distribution, which is directly related to Zipf's law. The formula of the power-law exponent is also derived. Finally, we conclude that the universality of the rank-size exponent is brought about by symmetry between an increase and a decrease in the random growth rate.
Non-mean-field critical exponent in a mean-field model: dynamics versus statistical mechanics.
Ogawa, Shun; Patelli, Aurelio; Yamaguchi, Yoshiyuki Y
2014-03-01
Mean-field theory tells us that the classical critical exponent of susceptibility is twice that of magnetization. However, linear response theory based on the Vlasov equation, which is naturally introduced by the mean-field nature, makes the former exponent half of the latter for families of quasistationary states having second order phase transitions in the Hamiltonian mean-field model and its variances, in the low-energy phase. We clarify that this strange exponent is due to the existence of Casimir invariants which trap the system in a quasistationary state for a time scale diverging with the system size. The theoretical prediction is numerically confirmed by N-body simulations for the equilibrium states and a family of quasistationary states.
Statistical properties of a dissipative kicked system: Critical exponents and scaling invariance
Energy Technology Data Exchange (ETDEWEB)
Oliveira, Diego F.M., E-mail: diegofregolente@gmail.com [CAMTP – Center for Applied Mathematics and Theoretical Physics, University of Maribor, Krekova 2, SI-2000 Maribor (Slovenia); Robnik, Marko, E-mail: robnik@uni-mb.si [CAMTP – Center for Applied Mathematics and Theoretical Physics, University of Maribor, Krekova 2, SI-2000 Maribor (Slovenia); Leonel, Edson D., E-mail: edleonel@rc.unesp.br [Departamento de Estatística, Matemática Aplicada e Computação, UNESP – Universidade Estadual Paulista, Av. 24A, 1515, Bela Vista, 13506-900 Rio Claro, SP (Brazil)
2012-01-16
A new universal empirical function that depends on a single critical exponent (acceleration exponent) is proposed to describe the scaling behavior in a dissipative kicked rotator. The scaling formalism is used to describe two regimes of dissipation: (i) strong dissipation and (ii) weak dissipation. For case (i) the model exhibits a route to chaos known as period doubling and the Feigenbaum constant along the bifurcations is obtained. When weak dissipation is considered the average action as well as its standard deviation are described using scaling arguments with critical exponents. The universal empirical function describes remarkably well a phase transition from limited to unlimited growth of the average action. -- Highlights: ► A new universal empirical function is proposed. ► The scaling formalism is used to describe two regimes of dissipation. ► The model exhibits a route to chaos known as period doubling. ► The average action as well as its standard deviation are described using scaling.
Critical Exponents, Scaling Law, Universality and Renormalization Group Flow in Strong Coupling QED
Kondo, Kei-Ichi
The critical behavior of strongly coupled QED with a chiral-invariant four-fermion interaction (gauged Nambu-Jona-Lasinio model) is investigated through the unquenched Schwinger-Dyson equation including the fermion loop effect at the one-loop level. It is shown that the critical exponents satisfy the (hyper)scaling relations as in the quenched case. However, the respective critical exponent takes the classical mean-field value, and consequently unquenched QED belongs to the same universality class as the zero-charge model. On the other hand, it is pointed out that quenched QED violates not only universality but also weak universality, due to continuously varying critical exponents. Furthermore, the renormalization group flow of constant renormalized charge is given. All the results are consistent with triviality of QED and the gauged Nambu-Jona-Lasinio model in the unquenched case.
Identification of exponent from load-deformation relation for soft materials from impact tests
Ciornei, F. C.; Alaci, S.; Romanu, I. C.; Ciornei, M. C.; Sopon, G.
2018-01-01
When two bodies are brought into contact, the magnitude of occurring reaction forces increase together with the amplitude of deformations. The load-deformation dependency of two contacting bodies is described by a function having the form F = Cxα . An accurate illustration of this relationship assumes finding the precise coefficient C and exponent α. This representation proved to be very useful in hardness tests, in dynamic systems modelling or in considerations upon the elastic-plastic ratio concerning a Hertzian contact. The classical method for identification of the exponent consists in finding it from quasi-static tests. The drawback of the method is the fact that the accurate estimation of the exponent supposes precise identification of the instant of contact initiation. To overcome this aspect, the following observation is exploited: during an impact process, the dissipated energy is converted into heat released by internal friction in the materials and energy for plastic deformations. The paper is based on the remark that for soft materials the hysteresis curves obtained for a static case are similar to the ones obtained for medium velocities. Furthermore, utilizing the fact that for the restitution phase the load-deformation dependency is elastic, a method for finding the α exponent for compression phase is proposed. The maximum depth of the plastic deformations obtained for a series of collisions, by launching, from different heights, a steel ball in free falling on an immobile prism made of soft material, is evaluated by laser profilometry method. The condition that the area of the hysteresis loop equals the variation of kinetical energy of the ball is imposed and two tests are required for finding the exponent. Five collisions from different launching heights of the ball were taken into account. For all the possible impact-pair cases, the values of the exponent were found and close values were obtained.
Surface Roughness Optimization Using Taguchi Method of High Speed End Milling For Hardened Steel D2
Hazza Faizi Al-Hazza, Muataz; Ibrahim, Nur Asmawiyah bt; Adesta, Erry T. Y.; Khan, Ahsan Ali; Abdullah Sidek, Atiah Bt.
2017-03-01
The main challenge for any manufacturer is to achieve higher quality of their final products with maintains minimum machining time. In this research final surface roughness analysed and optimized with maximum 0.3 mm flank wear length. The experiment was investigated the effect of cutting speed, feed rate and depth of cut on the final surface roughness using D2 as a work piece hardened to 52-56 HRC, and coated carbide as cutting tool with higher cutting speed 120-240 mm/min. The experiment has been conducted using L9 design of Taguchi collection. The results have been analysed using JMP software.
Fresh and hardened properties of binary blend high strength self compacting concrete
Directory of Open Access Journals (Sweden)
S.S. Vivek
2017-06-01
Full Text Available Self compacting concrete (SCC made a remarkable impact on the concrete construction industry because of its innovative nature. Assessment of optimal ratio between chemical and mineral admixtures plays a vital role in developing SCC. In the present work three different mineral admixtures were used as partial substitute in different proportions to cement to produce SCC with a characteristic compressive strength of 60 MPa. All the three types of SCC were investigated for its fresh and hardened properties. From the results, 50% GGBFS, 10% SF and 20% MK were found to the optimum values as partial substitute to cement.
Bayesian estimation of the self-similarity exponent of the Nile River fluctuation
Directory of Open Access Journals (Sweden)
S. Benmehdi
2011-06-01
Full Text Available The aim of this paper is to estimate the Hurst parameter of Fractional Gaussian Noise (FGN using Bayesian inference. We propose an estimation technique that takes into account the full correlation structure of this process. Instead of using the integrated time series and then applying an estimator for its Hurst exponent, we propose to use the noise signal directly. As an application we analyze the time series of the Nile River, where we find a posterior distribution which is compatible with previous findings. In addition, our technique provides natural error bars for the Hurst exponent.
Hunt, Allen G.
2016-04-01
Percolation theory can be used to find water flow paths of least resistance. Application of percolation theory to drainage networks allows identification of the range of exponent values that describe the tortuosity of rivers in real river networks, which is then used to generate the observed scaling between drainage basin area and channel length, a relationship known as Hack's law. Such a theoretical basis for Hack's law may allow interpretation of the range of exponent values based on an assessment of the heterogeneity of the substrate.
The susceptibility critical exponent for a nonaqueous ionic binary mixture near a consolute point
Zhang, Kai C.; Briggs, Matthew E.; Gammon, Robert W.; Levelt Sengers, J. M. H.
1992-01-01
We report turbidity measurements of a nonaqueous ionic solution of triethyl n-hexylammonium triethyl n-hexylboride in diphenyl ether. A classical susceptibility critical exponent gamma = 1.01 +/- 0.01 is obtained over the reduced temperature range t between values of 0.1 and 0.0001. The best fits of the sample transmission had a standard deviation of 0.39 percent over this range. Ising and spherical model critical exponents are firmly excluded. The correlation length amplitude xi sub 0 from fitting is 1.0 +/- 0.2 nm which is much larger than values found in neutral fluids and some aqueous binary mixtures.
Pushpalatha, K.; Sangaranarayanan, M. V.
1998-05-01
The surface pressure exerted by a monolayer of organic compounds condensing at electrochemical interfaces is evaluated using a two-dimensional nearest-neighbor Ising model formalism. The experimental critical temperature data of organic adsorbates are employed to obtain the composite short-range interaction energy using Onsager's exact solution. The methodology of obtaining the critical exponents ` δ' and ` γ' pertaining to surface pressure and isothermal compressibility is discussed. These values are consistent with the exponents postulated in other contexts, thereby demonstrating the universality hypothesis.
Extracting critical exponents for sequences of numerical data via series extrapolation techniques.
Cöster, Kris; Schmidt, Kai Phillip
2016-08-01
We describe a generic scheme to extract critical exponents of quantum lattice models from sequences of numerical data, which is, for example, relevant for nonperturbative linked-cluster expansions or nonperturbative variants of continuous unitary transformations. The fundamental idea behind our approach is a reformulation of the numerical data sequences as a series expansion in a pseudoparameter. This allows us to utilize standard series expansion extrapolation techniques to extract critical properties such as critical points and critical exponents. The approach is illustrated for the deconfinement transition of the antiferromagnetic spin-1/2 Heisenberg chain.
Explanation of the values of Hack's drainage basin, river length scaling exponent
Hunt, A. G.
2015-08-01
Percolation theory can be used to find water flow paths of least resistance. The application of percolation theory to drainage networks allows identification of the range of exponent values that describe the tortuosity of rivers in real river networks, which is then used to generate the observed scaling between drainage basin area and channel length, a relationship known as Hack's law. Such a theoretical basis for Hack's law allows interpretation of the range of exponent values based on an assessment of the heterogeneity of the substrate.
Tonachini, Glauco; Schlegel, H. Bernhard
1987-07-01
The Rys polynomial method has been used to evaluate the first derivatives of the two electron integrals and the nuclear electron attraction integrals with respect to the Gaussian exponents. Gradients for the sulfur 6-31 G(d) basis set in HS-, H2S, H3S+, H2S2, H3CSH, H2CS, CS, H2SO, SO2 and SO3 have been evaluated to illustrate the effect of charge, multiple bonding and hypervalency on the basis set exponents.
Quantifying the intermittency independent scaling exponents in the anisotropic solar wind.
Chapman, S. C.; Hnat, B.
2006-12-01
Solar wind turbulence is dominated by Alfvenic fluctuations with power spectral exponents that somewhat surprisingly evolve toward the Kolmogorov value of -5/3, that of hydrodynamic turbulence. We analyse a 3 year interval of ACE data that is dominated by slow solar wind and show that at 1AU the turbulence decomposes linearly into two coexistent components perpendicular and parallel to the local average magnetic field and determine the distinct intermittency independent scaling exponents. The first of these is consistent with recent predictions for anisotropic MHD and the second shows Kolmogorov-like scaling which we also find in the number and magnetic energy density, and Poynting flux.
Holmlund, K; Holmlund, Kenneth; Minnhagen, Petter
1995-01-01
The dynamics of two dimensional (2D) vortex fluctuations are investigated through simulations of the 2D Coulomb gas model in which vortices are represented by soft disks with logarithmic interactions. The simulations trongly support a recent suggestion that 2D vortex fluctuations obey an intrinsic anomalous dynamics manifested in a long range 1/t-tail in the vortex correlations. A new non-linear IV-exponent a, which is different from the commonly used AHNS exponent, a_AHNS and is given by a = 2a_AHNS - 3, is confirmed by the simulations. The results are discussed in the context of earlier simulations, experiments and a phenomenological description.
Finite-time Lyapunov exponent-based analysis for compressible flows
González, D. R.; Speth, R. L.; Gaitonde, D. V.; Lewis, M. J.
2016-08-01
The finite-time Lyapunov exponent (FTLE) technique has shown substantial success in analyzing incompressible flows by capturing the dynamics of coherent structures. Recent applications include river and ocean flow patterns, respiratory tract dynamics, and bio-inspired propulsors. In the present work, we extend FTLE to the compressible flow regime so that coherent structures, which travel at convective speeds, can be associated with waves traveling at acoustic speeds. This is particularly helpful in the study of jet acoustics. We first show that with a suitable choice of integration time interval, FTLE can extract wave dynamics from the velocity field. The integration time thus acts as a pseudo-filter separating coherent structures from waves. Results are confirmed by examining forward and backward FTLE coefficients for several simple, well-known acoustic fields. Next, we use this analysis to identify events associated with intermittency in jet noise pressure probe data. Although intermittent events are known to be dominant causes of jet noise, their direct source in the turbulent jet flow has remained unexplained. To this end, a Large-Eddy Simulation of a Mach 0.9 jet is subjected to FTLE to simultaneously examine, and thus expose, the causal relationship between coherent structures and the corresponding acoustic waves. Results show that intermittent events are associated with entrainment in the initial roll up region and emissive events downstream of the potential-core collapse. Instantaneous acoustic disturbances are observed to be primarily induced near the collapse of the potential core and continue propagating towards the far-field at the experimentally observed, approximately 30° angle relative to the jet axis.
Rapid hardening induced by electric pulse annealing in nanostructured pure aluminum
DEFF Research Database (Denmark)
Zeng, Wei; Shen, Yao; Zhang, Ning
2012-01-01
source-limited hardening” mechanism. However, the hardening kinetics was substantially faster for the electric pulse annealed material. Detailed microstructural characterization suggested that the rapid hardening during electric pulse annealing is related to an enhanced rate of recovery of dislocation...
Effect of hardening methods of moulding sands with water glass on structure of bonding bridges
Directory of Open Access Journals (Sweden)
M. Stachowicz
2010-07-01
Full Text Available Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented.Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardenedwith microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4 min is very close to that measured after traditional drying at 110 °C for 120 min. So, application of microwave hardening ensures significant shortening of the process time to the value comparable with CO2 hardening but guaranteeing over 10-fold increase of mechanical properties. Analysis of SEM images of hardened moulding sands permitted explaining differences in quality parameters of moulding sands by connecting them with structure of the created bonding bridges.
Energy Technology Data Exchange (ETDEWEB)
Piris, N. M.; Badia, J. M.; Antoranz, J. M.; Tarin, P.
2004-07-01
The importance of aluminium sheet forming in aero spatial industry makes it necessary to study those parameters that control the behaviour of material during the process. Tensile properties, strain hardening exponent n and strain rate sensitivity m in 7075 aluminium alloys have been studied to relate forming behaviour with control parameters. Tests on O, W, and T6 tempers have been performed, to determine the influence of heat treating. Finally, both longitudinal and long transverse directions tensile specimens have been obtained to analyze the anisotropy. (Author) 9 refs.
Strain hardening of polymer glasses: entanglements, energetics, and plasticity.
Hoy, Robert S; Robbins, Mark O
2008-03-01
Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.
Computed tomographic beam-hardening artefacts: mathematical characterization and analysis.
Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun
2015-06-13
This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
The effects of alloying elements on strength, hardenability, and ...
African Journals Online (AJOL)
They were then air cooled before being cold rolled to ~0.9mm and annealed. Dual phase heat treatment was carried out at 755oC followed by quenching in water. Tensile and hardenability tests were carried out. Results showed that alloying elements in steel increased strength in the dual phase steels by amounts ranging ...
Mechanical Properties Of Quench-Hardened, Martempered And ...
African Journals Online (AJOL)
This investigation is conducted to assess the influence of some heat treatment procedures on the structure and mechanical properties of cast ASTM A grade B-4 steel to which formation of grain boundary carbides have been a major problem. Some cast ASTM A grade B-4 steel samples were quench-hardened, ...
Self hardening property of Botswana fly ash | Sahu | Botswana ...
African Journals Online (AJOL)
In the present investigation, an effort has been made to study the self hardening property of Botswana fly ash by testing penetration resistance of fly ash flowable fills and unconfined compressive strength of 3 soils mixed with fly ash and compacted to their optimum unit weight. It has been found that the strength of both ...
Manufacturing Methods for Radiation-Hardened Multiple IC Chip Package
1975-10-01
anodization. Although the resistor material to be used on this program is MoSi^, the effects of anodization on CrSi resistors was also studied because CrSi ...is a thin-film resistor material which is also used in low-power radiacion-hardened integrated circuits. However, since the results for CrSi were
Copper-based dispersion hardened materials obtained by extrusion
Energy Technology Data Exchange (ETDEWEB)
Agbalyan, S.A.; Martirosyan, N.S.; Arutyunyan, A.S. [and others
1994-07-01
Using the results of differential thermal analysis, the sintering parameters and extrusion temperatures for the fabrication of Cu-Cr-Zn-TiC powder alloys were determined. The optimal compositions, and techniques for their production were identified. Industrial tests of electrodes prepared by extrusion of the dispersion hardened materials showed that their durability is 3-5 times greater than that of standard electrodes.
System Hardening Architecture for Safer Access to Critical Business ...
African Journals Online (AJOL)
System hardening is a defence strategy, where several different security measures are applied at various layers, all of which must be defeated before a module can be compromised. The protective mechanisms in this architecture are applied to the host, application, operating system, user, and the physical layers.
Preparation of Dispersion-Hardened Copper by Internal Oxidation
DEFF Research Database (Denmark)
Brøndsted, Povl; Sørensen, Ole Toft
1978-01-01
Internal oxidation experiments in CO2/CO atmospheres on Cu-Al alloys for preparation of dispersion-hardened Cu are described. The oxygen pressures of the atmospheres used in the experiments were controlled with a solid electrolyte oxygen cell based on ZrO2 (CaO). The particle size distributions...
system hardening architecture for safer access to critical business
African Journals Online (AJOL)
eobe
Corresponding author, Tel: +234-815-421-3807. SYSTEM HARDENING ARCHITECTURE FOR SAFER ACCESS TO CRITICAL. BUSINESS DATA. BUSINESS DATA. A. E. Ibor1, * and J. N. Obidinnu2. 1, 2DEPT OF COMPUTER SCIENCE, CROSS RIVER UNIVERSITY OF TECHNOLOGY, CALABAR, CROSS RIVER STATE ...
Surface modification on PMMA: PVDF polyblend: hardening under ...
Indian Academy of Sciences (India)
The influence of chemical environment on polymers include the surface alteration as well as other deep modifications in surface layers. The surface hardening, as an effect of organic liquids on poly(methyl methacrylate): poly(vinylidene fluoride) (PMMA: PVDF), which is one of the few known miscible blends, has been ...
Quantitative phase analysis of modified hardened cement paste
Demyanenko, O. V.; Kopanitsa, N. O.; Sarkisov, Yu S.; Abzaev, Yu A.; Ikonnikova, K. V.; Ikonnikova, L. F.
2017-10-01
The relevance of this research is stipulated by the opportunity to control the properties of construction materials through introducing nanomodifying additives. The study of structure parameters of the crystalline phase of hardened cement paste modified by microsilica and Ts38 additives is of great scientific and applied importance.
Evaluation of Local Vegetable Oils as Quenchants for Hardening ...
African Journals Online (AJOL)
However, the wear resistance of the quenched grey cast iron developed in this group of local vegetable oils was superior to that of SAE40 engine oil. The potentials of these oils as quenching media for grey cast iron hardening process ranked in descending order as soya bean, shea butter, groundnut, and palm kernel, with ...
Optimized radiation-hardened erbium doped fiber amplifiers for long space missions
Ladaci, A.; Girard, S.; Mescia, L.; Robin, T.; Laurent, A.; Cadier, B.; Boutillier, M.; Ouerdane, Y.; Boukenter, A.
2017-04-01
In this work, we developed and exploited simulation tools to optimize the performances of rare earth doped fiber amplifiers (REDFAs) for space missions. To describe these systems, a state-of-the-art model based on the rate equations and the particle swarm optimization technique is developed in which we also consider the main radiation effect on REDFA: the radiation induced attenuation (RIA). After the validation of this tool set by confrontation between theoretical and experimental results, we investigate how the deleterious radiation effects on the amplifier performance can be mitigated following adequate strategies to conceive the REDFA architecture. The tool set was validated by comparing the calculated Erbium-doped fiber amplifier (EDFA) gain degradation under X-rays at ˜300 krad(SiO2) with the corresponding experimental results. Two versions of the same fibers were used in this work, a standard optical fiber and a radiation hardened fiber, obtained by loading the previous fiber with hydrogen gas. Based on these fibers, standard and radiation hardened EDFAs were manufactured and tested in different operating configurations, and the obtained data were compared with simulation data done considering the same EDFA structure and fiber properties. This comparison reveals a good agreement between simulated gain and experimental data (architecture evolutions in the amplifier performance during the space mission. Optimization of both the fiber length and the EDFA pumping scheme allows us to strongly reduce its radiation vulnerability in terms of gain. The presented approach is a complementary and effective tool for hardening by device techniques and opens new perspectives for the applications of REDFAs and lasers in harsh environments.
2013-05-10
need to characterize and validate the specific performance characteristics of the hardened materials . In particular, the process parameters for which...metallography and microhardness profiling. The corrosion performance of the hardened surface is assessed using electrochemical potentiodynamic testing to...attempts to identify mechanisms of material failure and characterize how corrosion-assisted cracks initiate and grow in surface-hardened materials
Energy Technology Data Exchange (ETDEWEB)
Silva, Edmara Marques Rodrigues da
2001-07-01
The laser superficial hardening process of a ferrous alloy (gray cast iron) and of an aluminum-silicon alloy was investigated in this work. These metallic alloys are used in the automobile industry for manufacturing cylinders and pistons, respectively. By application of individual pulses and single tracks, the involved mechanisms during the processing were studied. Variables such as energy density, power density, temporal width, beam diameter on the sample surface, atmosphere of the processing region, overlapping and scanning velocity. The hardened surface was characterized by optical and scanning electronic microscopy, dispersive energy microanalysis, X-ray mapping, X-ray diffraction, and measurements of roughness and Vickers microhardness. Depending on the processing parameters, it is possible to obtain different microstructures. The affected area of gray cast iron, can be hardened by remelting or transformation hardening (total or partial) if the reached temperature is higher or not that of melting temperature. Laser treatment originated new structures such as retained austenite, martensite and, occasionally, eutectic of cellular dendritic structure. Aluminum-silicon alloy does not have phase transformation in solid state, it can be hardened only by remelting. The increase of hardness is a function of the precipitation hardening process, which makes the silicon particles smaller and more disperse in the matrix. Maximal values of microhardness (700-1000 HV) were reached with the laser treatment in gray cast iron samples. The initial microhardness is of 242 HV. For aluminum-silicon alloy, the laser remelting increases the initial microhardness of 128 HV to the range of 160-320 HV. The found results give a new perspective for using the CLA/IPEN's laser in the heat treatment area. Besides providing a higher absorptivity to the materials, compared with the CO{sub 2} laser, and optical fiber access, the superficial hardening with Nd:YAG laser, depending on the
Effect of interband interaction on isotope effect exponent of MgB2 ...
Indian Academy of Sciences (India)
com. MS received 22 September 2004; revised 5 January 2006; accepted 24 January 2005. Abstract. The exact formula of Tc's equation and the isotope effect exponent of two- band s-wave superconductors in the weak-coupling limit are ...
High-resolution satellite image segmentation using Hölder exponents
Indian Academy of Sciences (India)
Hölder exponent values (noise or not associated with the other cluster) are clubbed to a nearest possible cluster using the local maximum likelihood analysis. 1. Introduction. The spectral or pixel-based segmentation technique consists of K-Means (Hartigan et al 1979), Fuzzy. C Means (Bezdek et al 1984) and methods of.
External neutron source anomalies analysis using Hurst's exponent for the Myrrha reactor
Energy Technology Data Exchange (ETDEWEB)
Henrice Junior, Edson; Goncalves, Alessandro C., E-mail: ejunior@con.ufrj.br [Coordenacao dos Cursos de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Palma, Daniel A.P., E-mail: dapalma@cnen.gov.br [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeir, RJ (Brazil)
2015-07-01
Anomalous diffusion is usually marked by the non-linear growth of the variance in time, that is, the diffusion will be considered as anomalous if there is a deviation in the behaviour described before. This paper aims to identify anomalies in the neutron flux during the operation of an ADS (Accelerator Driven System) nuclear reactor as a result of a trip that originates in the proton accelerator as per project bases, from two different calculation methods for Hurst exponents. These methods are the R/S Method and the Detrended Fluctuation Analysis (DFA) Method. For that the Myrrha Reactor will be simulated using the SERPENT code and the neutron source will be subjected to a production peak at a given instant. The Hurst exponent has a direct application on determining the order of derivatives in fractional point-kinetics equations and the estimate for the fractional derivative can be related as being twice that of Hurst's exponent, according to the co-variance function in the Gauss' processes. After getting the Hurst's exponent a numerically solution is proposed. This subject being a theme very much in focus nowadays. (author)
Phase space reconstruction and estimation of the largest Lyapunov exponent for gait kinematic data
Energy Technology Data Exchange (ETDEWEB)
Josiński, Henryk [Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Świtoński, Adam [Polish-Japanese Institute of Information Technology, Aleja Legionów 2, 41-902 Bytom (Poland); Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Michalczuk, Agnieszka; Wojciechowski, Konrad [Polish-Japanese Institute of Information Technology, Aleja Legionów 2, 41-902 Bytom (Poland)
2015-03-10
The authors describe an example of application of nonlinear time series analysis directed at identifying the presence of deterministic chaos in human motion data by means of the largest Lyapunov exponent. The method was previously verified on the basis of a time series constructed from the numerical solutions of both the Lorenz and the Rössler nonlinear dynamical systems.
Predicting Traffic Flow in Local Area Networks by the Largest Lyapunov Exponent
Directory of Open Access Journals (Sweden)
Yan Liu
2016-01-01
Full Text Available The dynamics of network traffic are complex and nonlinear, and chaotic behaviors and their prediction, which play an important role in local area networks (LANs, are studied in detail, using the largest Lyapunov exponent. With the introduction of phase space reconstruction based on the time sequence, the high-dimensional traffic is projected onto the low dimension reconstructed phase space, and a reduced dynamic system is obtained from the dynamic system viewpoint. Then, a numerical method for computing the largest Lyapunov exponent of the low-dimensional dynamic system is presented. Further, the longest predictable time, which is related to chaotic behaviors in the system, is studied using the largest Lyapunov exponent, and the Wolf method is used to predict the evolution of the traffic in a local area network by both Dot and Interval predictions, and a reliable result is obtained by the presented method. As the conclusion, the results show that the largest Lyapunov exponent can be used to describe the sensitivity of the trajectory in the reconstructed phase space to the initial values. Moreover, Dot Prediction can effectively predict the flow burst. The numerical simulation also shows that the presented method is feasible and efficient for predicting the complex dynamic behaviors in LAN traffic, especially for congestion and attack in networks, which are the main two complex phenomena behaving as chaos in networks.
Directional maximum likelihood self-estimation of the path-loss exponent
Hu, Y.; Leus, G.J.T.; Dong, Min; Zheng, Thomas Fang
2016-01-01
The path-loss exponent (PLE) is a key parameter in wireless propagation channels. Therefore, obtaining the knowledge of the PLE is rather significant for assisting wireless communications and networking to achieve a better performance. Most existing methods for estimating the PLE not only require
Using machine learning to replicate chaotic attractors and calculate Lyapunov exponents from data
Pathak, Jaideep; Lu, Zhixin; Hunt, Brian R.; Girvan, Michelle; Ott, Edward
2017-12-01
We use recent advances in the machine learning area known as "reservoir computing" to formulate a method for model-free estimation from data of the Lyapunov exponents of a chaotic process. The technique uses a limited time series of measurements as input to a high-dimensional dynamical system called a "reservoir." After the reservoir's response to the data is recorded, linear regression is used to learn a large set of parameters, called the "output weights." The learned output weights are then used to form a modified autonomous reservoir designed to be capable of producing an arbitrarily long time series whose ergodic properties approximate those of the input signal. When successful, we say that the autonomous reservoir reproduces the attractor's "climate." Since the reservoir equations and output weights are known, we can compute the derivatives needed to determine the Lyapunov exponents of the autonomous reservoir, which we then use as estimates of the Lyapunov exponents for the original input generating system. We illustrate the effectiveness of our technique with two examples, the Lorenz system and the Kuramoto-Sivashinsky (KS) equation. In the case of the KS equation, we note that the high dimensional nature of the system and the large number of Lyapunov exponents yield a challenging test of our method, which we find the method successfully passes.
Upper and lower critical decay exponents of Ising ferromagnets with long-range interaction.
Horita, Toshiki; Suwa, Hidemaro; Todo, Synge
2017-01-01
We investigate the universality class of the finite-temperature phase transition of the two-dimensional Ising model with the algebraically decaying ferromagnetic long-range interaction, J_{ij}=|r[over ⃗]_{i}-r[over ⃗]_{j}|^{-(d+σ)}, where d (=2) is the dimension of the system and σ is the decay exponent, by means of the order-N cluster-algorithm Monte Carlo method. In particular, we focus on the upper and lower critical decay exponents, the boundaries between the mean-field-universality, intermediate, and short-range-universality regimes. At the critical decay exponents, it is found that the standard Binder ratio of magnetization at the critical temperature exhibits extremely slow convergence as a function of the system size. We propose more effective physical quantities, namely the combined Binder ratio and the self-combined Binder ratio, both of which cancel the leading finite-size corrections of the conventional Binder ratio. Utilizing these techniques, we clearly demonstrate that in two dimensions, the lower and upper critical decay exponents are σ=1 and 7/4, respectively, contrary to the recent Monte Carlo and renormalization-group studies [M. Picco, arXiv:1207.1018; T. Blanchard et al., Europhys. Lett. 101, 56003 (2013)EULEEJ0295-507510.1209/0295-5075/101/56003].
Critical exponents in the transition to chaos in one-dimensional ...
Indian Academy of Sciences (India)
We report the numerically evaluated critical exponents associated with the scaling of generalized fractal dimensions during the transition from order to chaos. The analysis is carried out in detail in the context of unimodal and bimodal maps representing typical one-dimensional discrete dynamical systems. The behavior of ...
DEFF Research Database (Denmark)
Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin
2015-01-01
This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...
Maouche Hichem; Hadji Ali; Bouhamla Khedidja
2014-01-01
This study relates to the manufacture of austenitic manganese steel for the heart switching crossings of railways in all industrial countries where heavy loads are moved by rail. This steel is characterized by a high surface hardness service yard caused by the phenomenon of hardening. According to the microstructure formed after quenching, the transformation of austenite into martensite during working, determine the operating life. The rate of transformation of austenite into martensite can f...
Vila Pastor, Carlos; Siller, H.R.; Rodríguez, C.A.; BRUSCAS BELLIDO, GRACIA-MARIA; Serrano, J.
2012-01-01
This work deals with the technological and economic considerations required to select face milling vs. surface grinding operations in the manufacture of hardened steel flat surfaces for dies and moulds. In terms of technological considerations, factors such as component geometry, material and surface quality (dimensional tolerance and surface finish) are taken into account. The economic considerations include the cost of machine depreciation, labour and consumables (cutting tools in face mill...
Inter-relationship between scaling exponents for describing self-similar river networks
Yang, Soohyun; Paik, Kyungrock
2015-04-01
Natural river networks show well-known self-similar characteristics. Such characteristics are represented by various power-law relationships, e.g., between upstream length and drainage area (exponent h) (Hack, 1957), and in the exceedance probability distribution of upstream area (exponent É) (Rodriguez-Iturbe et al., 1992). It is empirically revealed that these power-law exponents are within narrow ranges. Power-law is also found in the relationship between drainage density (the total stream length divided by the total basin area) and specified source area (the minimum drainage area to form a stream head) (exponent η) (Moussa and Bocquillon, 1996). Considering that above three scaling relationships all refer to fundamental measures of 'length' and 'area' of a given drainage basin, it is natural to hypothesize plausible inter-relationship between these three scaling exponents. Indeed, Rigon et al. (1996) demonstrated the relationship between É and h. In this study, we expand this to a more general É-η-h relationship. We approach É-η relationship in an analytical manner while η-h relationship is demonstrated for six study basins in Korea. Detailed analysis and implications will be presented. References Hack, J. T. (1957). Studies of longitudinal river profiles in Virginia and Maryland. US, Geological Survey Professional Paper, 294. Moussa, R., & Bocquillon, C. (1996). Fractal analyses of tree-like channel networks from digital elevation model data. Journal of Hydrology, 187(1), 157-172. Rigon, R., Rodriguez-Iturbe, I., Maritan, A., Giacometti. A., Tarboton, D. G., & Rinaldo, A. (1996). On Hack's Law. Water Resources Research, 32(11), 3367-3374. Rodríguez-Iturbe, I., Ijjasz-Vasquez, E. J., Bras, R. L., & Tarboton, D. G. (1992). Power law distributions of discharge mass and energy in river basins. Water Resources Research, 28(4), 1089-1093.
Radiation Hardened Electronics Destined For Severe Nuclear Reactor Environments
Energy Technology Data Exchange (ETDEWEB)
Holbert, Keith E. [Arizona State Univ., Tempe, AZ (United States); Clark, Lawrence T. [Arizona State Univ., Tempe, AZ (United States)
2016-02-19
Post nuclear accident conditions represent a harsh environment for electronics. The full station blackout experience at Fukushima shows the necessity for emergency sensing capabilities in a radiation-enhanced environment. This NEET (Nuclear Energy Enabling Technologies) research project developed radiation hardened by design (RHBD) electronics using commercially available technology that employs commercial off-the-shelf (COTS) devices and present generation circuit fabrication techniques to improve the total ionizing dose (TID) hardness of electronics. Such technology not only has applicability to severe accident conditions but also to facilities throughout the nuclear fuel cycle in which radiation tolerance is required. For example, with TID tolerance to megarads of dose, electronics could be deployed for long-term monitoring, inspection and decontamination missions. The present work has taken a two-pronged approach, specifically, development of both board and application-specific integrated circuit (ASIC) level RHBD techniques. The former path has focused on TID testing of representative microcontroller ICs with embedded flash (eFlash) memory, as well as standalone flash devices that utilize the same fabrication technologies. The standalone flash devices are less complicated, allowing better understanding of the TID response of the crucial circuits. Our TID experiments utilize biased components that are in-situ tested, and in full operation during irradiation. A potential pitfall in the qualification of memory circuits is the lack of rigorous testing of the possible memory states. For this reason, we employ test patterns that include all ones, all zeros, a checkerboard of zeros and ones, an inverse checkerboard, and random data. With experimental evidence of improved radiation response for unbiased versus biased conditions, a demonstration-level board using the COTS devices was constructed. Through a combination of redundancy and power gating, the demonstration
Franken, S M; Genders, R E; de Gruijl, F R; Rustemeyer, T; Pavel, S
2013-01-01
An effective prophylactic treatment of patients with polymorphic light eruption (PLE) consists of repeated low, gradually increasing exposures to UVB radiation. This so-called UV(B) hardening induces better tolerance of the skin to sunlight. SunshowerMedical company (Amsterdam) has developed an UV (B) source that can be used during taking shower. The low UV fluence of this apparatus makes it an interesting device for UV hardening. In a group of PLE patients, we compared the effectiveness of the irradiation with SunshowerMedical at home with that of the UVB treatment in the hospital. The PLE patients were randomized for one of the treatments. The hospital treatment consisted of irradiations with broad-band UVB (Waldmann 85/UV21 lamps) twice a week during 6 weeks. The home UV-device was used each day with the maximal irradiation time of 6 min. The outcome assessment was based on the information obtained from patients' dermatological quality of life (DLQI) questionnaires, the ability of both phototherapies to reduce the provocation reaction and from the patients' evaluation of the long-term benefits of their phototherapies. Sixteen patients completed treatment with SunshowerMedical and thirteen completed treatment in hospital. Both types of phototherapy were effective. There was a highly significant improvement in DLQI with either treatment. In most cases, the hardening reduced or even completely suppressed clinical UV provocation of PLE. The patients using SunshowerMedical at home were, however, much more content with the treatment procedure than the patients visiting the dermatological units. Both treatments were equally effective in the induction of skin tolerance to sunlight in PLE patients. However, the home treatment was much better accepted than the treatment in the hospital. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.
Surface hardening of titanium alloys with melting depth controlled by heat sink
Oden, Laurance L.; Turner, Paul C.
1995-01-01
A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.
Directory of Open Access Journals (Sweden)
Emlyn Flint
2017-03-01
Full Text Available Background: Contingent claims on underlying assets are typically priced under a framework that assumes, inter alia, that the log returns of the underlying asset are normally distributed. However, many researchers have shown that this assumption is violated in practice. Such violations include the statistical properties of heavy tails, volatility clustering, leptokurtosis and long memory. This paper considers the pricing of contingent claims when the underlying is assumed to display long memory, an issue that has heretofore not received much attention. Aim: We address several theoretical and practical issues in option pricing and implied volatility calibration in a fractional Black–Scholes market. We introduce a novel eight-parameter fractional Black–Scholes-inspired (FBSI model for the implied volatility surface, and consider in depth the issue of calibration. One of the main benefits of such a model is that it allows one to decompose implied volatility into an independent long-memory component – captured by an implied Hurst exponent – and a conditional implied volatility component. Such a decomposition has useful applications in the areas of derivatives trading, risk management, delta hedging and dynamic asset allocation. Setting: The proposed FBSI volatility model is calibrated to South African equity index options data as well as South African Rand/American Dollar currency options data. However, given the focus on the theoretical development of the model, the results in this paper are applicable across all financial markets. Methods: The FBSI model essentially combines a deterministic function form of the 1-year implied volatility skew with a separate deterministic function for the implied Hurst exponent, thus allowing one to model both observed implied volatility surfaces as well as decompose them into independent volatility and long-memory components respectively. Calibration of the model makes use of a quasi-explicit weighted
Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites
Dey, Vikram
The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and
Prediction Of Mechanical Properties Of Quench Hardening Steel*
Directory of Open Access Journals (Sweden)
Chotěborský R.
2015-03-01
Full Text Available The present study investigated the application of finite element method for prediction of mechanical properties of quench hardening steel. Based on the experimental results obtained, a numerical model for simulation of continuous cooling of quench hardening steel was developed. For the simulation of the kinetics of diffusion phase transformations, the Avrami equation and additive rule were applied. A new model was also developed for martensitic transformation which was validated using metallographic analysis and hardness tests. Experimental and simulation results indicated a good agreement. The developed model information provided here could be used for simulation of continuous cooling and kinetics phase transformation as well as for prediction of final distribution of microstructures and hardness of alloy steels.
Investigation on Formation and Hardening Process of Microcapsules Under Excitation
Lin, Tien-Chu
This research investigates the micro-encapsulation process with a pressure-type micro-atomizer. Alginate and CaCl2 aqueous solution are used as the membrane material and hardening agent, respectively. The high speed images were taken to investigate the formation processes of the microcapsules. Results show that the geometric shape of the microcapsules was sensitive to the droplet flying distant and the concentration of alginate aqueous, however, insensitive to the concentration of CaCl2 aqueous. Results also show that the membrane thickness of the microcapsules was controlled by the diffusion processes of calcium chloride. An empirical formula was derived to describe the rate change of the membrane thickness in the hardening processes.
An energy-based beam hardening model in tomography
Energy Technology Data Exchange (ETDEWEB)
Casteele, E van de; Dyck, D van; Sijbers, J; Raman, E [Vision Lab, Physics Departement, University of Antwerp (RUCA) (Belgium)
2002-12-07
As a consequence of the polychromatic x-ray source, used in micro-computer tomography ({mu}CT) and in medical CT, the attenuation is no longer a linear function of absorber thickness. If this nonlinear beam hardening effect is not compensated, the reconstructed images will be corrupted by cupping artefacts. In this paper, a bimodal energy model for the detected energy spectrum is presented, which can be used for reduction of artefacts caused by beam hardening in well-specified conditions. Based on the combination of the spectrum of the source and the detector efficiency, the assumption is made that there are two dominant energies which can describe the system. The validity of the proposed model is examined by fitting the model to the experimental datapoints obtained on a microtomograph for different materials and source voltages.
Hardening electronic devices against very high total dose radiation environments
Buchanan, B.; Shedd, W.; Roosild, S.; Dolan, R.
1972-01-01
The possibilities and limitations of hardening silicon semiconductor devices to the high neutron and gamma radiation levels and greater than 10 to the eighth power rads required for the NERVA nuclear engine development are discussed. A comparison is made of the high dose neutron and gamma hardening potential of bipolar, metal insulator semiconductors and junction field effect transistors. Experimental data is presented on device degradation for the high neutron and gamma doses. Previous data and comparisons indicate that the JFET is much more immune to the combined neutron displacement and gamma ionizing effects than other transistor types. Experimental evidence is also presented which indicates that p channel MOS devices may be able to meet the requirements.
Hardening by annealing and softening by deformation in nanostructured metals
DEFF Research Database (Denmark)
Huang, X.; Hansen, N.; Tsuji, N.
2006-01-01
We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation-dislocation and ......We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation....... As a consequence, the strength decreases and the ductility increases. These observations suggest that for materials such as the nanostructured aluminum studied here, deformation should be used as an optimizing procedure instead of annealing....
Maniks, J.; Manika, Ilze; Schwartz, K.; Toulemonde, M.; Trautmann, C.
2003-08-01
The irradiation of LiF crystals with Au, Pb, Bi, and S ions in the range of 400 - 2200 MeV leads to a remarkable increase of the hardness. The effect appears for Bi and Pb ions at fluences above 109 ions/cm2 and for S ions above 1010 ions/cm2. The increase of hardness follows the energy loss and is related to the formation of defects along the ion path. Defect complexes, clusters and aggregates with nanoscale dimensions serve as strong obstacles for dislocations and cause dispersion strengthening. Structural investigations reveal the generation of long-range stress in the adjacent non-irradiated part of the crystal. Close to the implantation zone, the stress exceeds the yield strength, causing microplastic deformation and work hardening. Compared to light S ions, heavy ions (Au, Pb, Bi) cause more severe structural damage, larger hardening effects, and higher internal and long-range stress.
Liu, W.; Guines, D.; Léotoing, L.; Ragneau, E.
2016-10-01
In this work, an in-plane biaxial tensile test of cruciform specimen is performed to identify the visco-plastic hardening behaviour of metallic sheets for both large strains and intermediate strain rates at room temperature. Firstly, an optimal shape of the specimen is suggested. Then, dynamic biaxial tensile tests are carried out for a dual phase DP600 steel sheet. Experimental forces on the two axes of the specimen are measured during the test and strains in the central area of the specimen are post-treated by means of Digital Image Correlation (DIC) technique. Finally, considering a Hill48 anisotropic yield criterion, two strain rate dependent hardening laws are identified thanks to an inverse procedure based on a Finite Element (FE) modelling of the biaxial tensile test and on the experimental data mentioned above. The identified biaxial flow curves are then compared with the ones from a classical uniaxial tensile test.
Degtyarev, S. I.; Skoblo, T. S.; Sapozhnikov, V. E.
1998-12-01
A technology of heat treatment of railroad rails using induction heating has been developed and installed in the Azovstal' metallurgical works. It provides the requisite combination of properties in the metal of rail heads. However, the metal of the web and the bottom of the rails remains in the initial (unhardened) state. Under severe operational conditions (small-radius curves, high axial loads, and composite configuration of the road) the wear resistance of the head and the structural strength of the web and the bottom not hardened in the plant have to be increased. The properties of the rail steel can be improved by alloying it using the most effective and available elements. Currently, in Ukraine this is manganese. The present paper is devoted to the effect of manganese additives on the phase transformations in induction hardening and the specific features of the formed structure and properties of the rail steel. Optimum parameters for heat treatment of rails are recommended.
Strain Hardening in Polymer Glasses: Limitations of Network Models
Hoy, Robert S.; Robbins, Mark O.
2007-01-01
Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of l...
Control technology for surface treatment of materials using induction hardening
Energy Technology Data Exchange (ETDEWEB)
Kelley, J.B.; Skocypec, R.D. [Sandia National Labs., NM (United States)
1997-04-01
In the industrial and automotive industries, induction case hardening is widely used to provide enhanced strength, wear resistance, and toughness in components made from medium and high carbon steels. The process uses significantly less energy than competing batch process, is environmentally benign, and is a very flexible in-line manufacturing process. As such, it can directly contribute to improved component reliability, and the manufacture of high-performance lightweight parts. However, induction hardening is not as widely used as it could be. Input material and unexplained process variations produce significant variation in product case depth and quality. This necessitates frequent inspection of product quality by destructive examination, creates higher than desired scrap rates, and causes de-rating of load stress sensitive components. In addition, process and tooling development are experience-based activities, accomplished by trial and error. This inhibits the use of induction hardening for new applications, and the resultant increase in energy efficiency in the industrial sectors. In FY96, a Cooperative Research and Development Agreement under the auspices of the Technology Transfer Initiative and the Partnership for a New Generation of Vehicles was completed. A multidisciplinary team from Sandia National Labs and Delphi Saginaw Steering Systems investigated the induction hardening by conducting research in the areas of process characterization, computational modeling, materials characterization, and high speed data acquisition and controller development. The goal was to demonstrate the feasibility of closed-loop control for a specific material, geometry, and process. Delphi Steering estimated annual savings of $2-3 million per year due to reduced scrap losses, inspection costs, and machine down time if reliable closed-loop control could be achieved. A factor of five improvement in process precision was demonstrated and is now operational on the factory floor.
The effects of alloying elements on strength, hardenability, and ...
African Journals Online (AJOL)
The effects of alloying elements (Nb, V, Mo) on dual phase steels have been studied in relation to ultimate tensile strength (U.T.S.) ductility and hardenability. C-Mn, Nb-Mo, Nb and Nb-V steels were hot rolled from 25mm to 4.5mm finishing at temperatures in the range 780oC – 950oC. They were then air cooled before ...
Hardening of commercial CMOS PROMs with polysilicon fusible links
Newman, W. H.; Rauchfuss, J. E.
1985-01-01
The method by which a commercial 4K CMOS PROM with polysilicon fuses was hardened and the feasibility of applying this method to a 16K PROM are presented. A description of the process and the necessary minor modifications to the original layout are given. The PROM circuit and discrete device characteristics over radiation to 1000K rad-Si are summarized. The dose rate sensitivity of the 4K PROMs is also presented.
Common and uncommon reactions to formaldehyde-containing nail hardeners.
Norton, L A
1991-03-01
A spectrum of reactions to free formaldehyde containing nail hardeners is presented. These include inflammatory and noninflammatory onycholysis, paronychia, chromonychia, nail plate shedding, and pterygium inversum unguis as well as satellite reactions on the skin and mucous membranes. Primary irritants are more common than allergic reactions. Nail cosmetic products containing free formaldehyde are available to the consumer, but federal guidelines dictate their labeling, acceptable concentration, and usage.
[X-ray hardening correction for ICT in testing workpiece].
Peng, Guang-han; Cai, Xin-hua; Han, Zhong; Yang, Xue-heng
2008-06-01
Since energy spectrum of X-ray is polychromatic source in X-ray industrial computerized tomography, the variation of attenuation coefficient with energy leads to the lower energy of X-ray radiation being absorbed preferentially when X-ray is transmitting the materials. And the higher the energy of X-ray, the lower the attenuation coefficient of X-ray. With the increase in the X-ray transmission thickness, it becomes easier for the X-ray to transmit the matter. Thus, the phenomenon of energy spectrum hardening of X-ray takes place, resulting from the interaction between X-ray and the materials. This results in false images in the reconstruction of X-ray industrial computerized tomography. Therefore, hardening correction of energy spectrum of X-ray has to be done. In the present paper, not only is the hardening phenomenon of X-ray transmitting the materials analyzed, but also the relation between the X-ray beam sum and the transmission thickness of X-ray is discussed. And according to the Beer law and the characteristics of interaction when X-ray is transmitting material, and by getting the data of X-ray beam sum, the relation equation is fitted between the X-ray beam sum and X-ray transmission thickness. Then, the relation and the method of equivalence are carried out for X-ray beam sum being corrected. Finally, the equivalent and monochromatic attenuation coefficient fitted value for X-ray transmitting the material is reasoned out. The attenuation coefficient fitted value is used for product back-projection image reconstruction in X-ray industrial computerized tomography. Thus, the effect caused by X-ray beam hardening is wiped off effectively in X-ray industrial computerized tomography.
Extracting Lyapunov exponents from the echo dynamics of Bose-Einstein condensates on a lattice
Tarkhov, Andrei E.; Wimberger, Sandro; Fine, Boris V.
2017-08-01
We propose theoretically an experimentally realizable method to demonstrate the Lyapunov instability and to extract the value of the largest Lyapunov exponent for a chaotic many-particle interacting system. The proposal focuses specifically on a lattice of coupled Bose-Einstein condensates in the classical regime describable by the discrete Gross-Pitaevskii equation. We suggest to use imperfect time reversal of the system's dynamics known as the Loschmidt echo, which can be realized experimentally by reversing the sign of the Hamiltonian of the system. The routine involves tracking and then subtracting the noise of virtually any observable quantity before and after the time reversal. We support the theoretical analysis by direct numerical simulations demonstrating that the largest Lyapunov exponent can indeed be extracted from the Loschmidt echo routine. We also discuss possible values of experimental parameters required for implementing this proposal.
Using largest Lyapunov exponent to confirm the intrinsic stability of boiling water reactors
Energy Technology Data Exchange (ETDEWEB)
Gavilian-Moreno, Carlos [Iberdrola Generacion, S.A., Cofrentes Nuclear Power Plant, Project Engineering Department, Paraje le Plano S/N, Valencia (Spain); Espinosa-Paredes, Gilberto [Area de ingeniera en Recursos Energeticos, Universidad Autonoma Metropolitana-Iztapalapa, Mexico city (Mexico)
2016-04-15
The aim of this paper is the study of instability state of boiling water reactors with a method based in largest Lyapunov exponents (LLEs). Detecting the presence of chaos in a dynamical system is an important problem that is solved by measuring the LLE. Lyapunov exponents quantify the exponential divergence of initially close state-space trajectories and estimate the amount of chaos in a system. This method was applied to a set of signals from several nuclear power plant (NPP) reactors under commercial operating conditions that experienced instabilities events, apparently each of a different nature. Laguna Verde and Forsmark NPPs with in-phase instabilities, and Cofrentes NPP with out-of-phases instability. This study presents the results of intrinsic instability in the boiling water reactors of three NPPs. In the analyzed cases the limit cycle was not reached, which implies that the point of equilibrium exerts influence and attraction on system evolution.
Nonuniversality of the Archie exponent due to multifractality of resistivity well logs
Dashtian, Hassan; Yang, Yafan; Sahimi, Muhammad
2015-12-01
Archie's law expresses a relation between the formation factor F of porous media and their porosity ϕ, F∝ϕ-m, where m is the Archie or the cementation exponent. Despite widespread use of Archie's law, the value of m and whether it is universal and independent of the type of reservoir have remained controversial. We analyze various porosity and resistivity logs along 36 wells in six Iranian oil and gas reservoirs using wavelet transform coherence and multifractal detrended fluctuation analysis. m is estimated for two sets of data: one set contains the resistivity data that include those segments of the well that contain significant clay content and one without. The analysis indicates that the well logs are multifractal and that due to the multifractality the exponent m is nonuniversal. Thus, analysis of the resistivity of laboratory or outcrop samples that are not multifractal yields estimates of m that are not applicable to well logs in oil or gas reservoirs.
Using Largest Lyapunov Exponent to Confirm the Intrinsic Stability of Boiling Water Reactors
Directory of Open Access Journals (Sweden)
Carlos J. Gavilán-Moreno
2016-04-01
Full Text Available The aim of this paper is the study of instability state of boiling water reactors with a method based in largest Lyapunov exponents (LLEs. Detecting the presence of chaos in a dynamical system is an important problem that is solved by measuring the LLE. Lyapunov exponents quantify the exponential divergence of initially close state-space trajectories and estimate the amount of chaos in a system. This method was applied to a set of signals from several nuclear power plant (NPP reactors under commercial operating conditions that experienced instabilities events, apparently each of a different nature. Laguna Verde and Forsmark NPPs with in-phase instabilities, and Cofrentes NPP with out-of-phases instability. This study presents the results of intrinsic instability in the boiling water reactors of three NPPs. In the analyzed cases the limit cycle was not reached, which implies that the point of equilibrium exerts influence and attraction on system evolution.
Predicted and verified evolution of power-law exponent in product market
Hisano, Ryohei; Mizuno, Takayuki
2011-01-01
Power-law distributions constitute a generic empirical statistical regularity found in many complex systems. A recently developed theory finds that the interplay between one of the most universal ingredient, i.e., stochastic proportional growth, and stochastic birth and death processes, leads to generic power law distributions together with a non-universal exponent which depends explicitly on the characteristics of growth, birth and death. In particular, the theory rationalizes Zipf's law and explains deviations from it, for instance for the distribution of firm and of city sizes. Here, we report the first complete test of the theory, based on the empirical analysis from a real world complex phenomenon, namely the dynamics of market shares in the consumer electronics market. We estimate directly from the data the average growth rate of market shares, their standard deviation, the birth rates as well as the "death" hazard rate of products. When plugged in the theory, this predicts the power law exponent of the...
Existence of solutions for p-Kirchhoff type problems with critical exponent
Directory of Open Access Journals (Sweden)
Ahmed Hamydy
2011-08-01
Full Text Available We study the existence of solutions for the p-Kirchhoff type problem involving the critical Sobolev exponent, $$displaylines{ -Big[gBig(int_Omega|abla u|^pdxBigBig]Delta_pu =lambda f(x,u+|u|^{p^star-2}uquadext{in }Omega,cr u=0quadext{on }partialOmega, }$$ where $Omega$ is a bounded smooth domain of $mathbb{R}^N$, $1
exponent, $lambda$ is a positive parameter, f and g are continuous functions. The main results of this paper establish, via the variational method. The concentration-compactness principle allows to prove that the Palais-Smale condition is satisfied below a certain level.
Electronic structure, lattice energies and Born exponents for alkali halides from first principles
Directory of Open Access Journals (Sweden)
C. R. Gopikrishnan
2012-03-01
Full Text Available First principles calculations based on DFT have been performed on crystals of halides (X = F, Cl, Br and I of alkali metals (M = Li, Na, K, Rb and Cs. The calculated lattice energies (U0 are in good agreement with the experimental lattice enthalpies. A new exact formalism is proposed to determine the Born exponent (n for ionic solids. The values of the Born exponent calculated through this ab-initio technique is in good agreement with previous empirically derived results. Band Structure calculations reveal that these compounds are wide-gap insulators that explains their optical transparency. Projected density of states (PDOS calculations reveal that alkali halides with small cations and large anions, have small band gaps due to charge transfer from X → M. This explains the onset of covalency in ionic solids, which is popularly known as the Fajans Rule.
Stability Analysis of Bipedal Robots Using the Concept of Lyapunov Exponents
Directory of Open Access Journals (Sweden)
Liu Yunping
2013-01-01
Full Text Available The dynamics and stability of passive bipedal robot have an important impact on the mass distribution, leg length, and the angle of inclination. Lyapunov’s second method is difficult to be used in highly nonlinear multibody systems, due to the lack of constructive methods for deriving Lyapunov fuction. The dynamics equation is established by Kane method, the relationship between the mass, length of leg, angle of inclination, and stability of passive bipedal robot by the largest Lyapunov exponent. And the Lyapunov exponents of continuous dynamical systems are estimated by numerical methods, which are simple and easy to be applied to the system stability simulation analysis, provide the design basis for passive bipedal robot prototype, and improve design efficiency.
Lyapunov exponents from kinetic theory for a dilute, field-driven Lorentz gas
Van Beijeren, H; Cohen, E G D; Posch, H A; Dellago, C
1996-01-01
Positive and negative Lyapunov exponents for a dilute, random, two-dimensional Lorentz gas in an applied field, \\vec{E}, in a steady state at constant energy are computed to order E^{2}. The results are: \\lambda_{\\pm}=\\lambda_{\\pm}^{0}-a_{\\pm}(qE/mv)^{2}t_{0} where \\lambda_{\\pm}^{0} are the exponents for the field-free Lorentz gas, a_{+}=11/48, a_{-}=7/48, t_{0} is the mean free time between collisions, q is the charge, m the mass and v is the speed of the particle. The calculation is based on an extended Boltzmann equation in which a radius of curvature, characterizing the separation of two nearby trajectories, is one of the variables in the distribution function. The analytical results are in excellent agreement with computer simulations. These simulations provide additional evidence for logarithmic terms in the density expansion of the diffusion coefficient.
Directory of Open Access Journals (Sweden)
Jie-Xiong Mo
2014-01-01
Full Text Available We investigate the phase transitions of black holes with conformal anomaly in canonical ensemble. Some interesting and novel phase transition phenomena have been discovered. It is shown that there are striking differences in both Hawking temperature and phase structure between black holes with conformal anomaly and those without it. Moreover, we probe in detail the dependence of phase transitions on the choice of parameters. The results show that black holes with conformal anomaly have much richer phase structure than those without it. There would be two, only one, or no phase transition points depending on the parameters. The corresponding parameter regions are derived both numerically and graphically. Geometrothermodynamics are built up to examine the phase structure we have discovered. It is shown that Legendre invariant thermodynamic scalar curvature diverges exactly where the specific heat diverges. Furthermore, critical behaviors are investigated by calculating the relevant critical exponents. And we prove that these critical exponents satisfy the thermodynamic scaling laws.
Dependence of exponents on text length versus finite-size scaling for word-frequency distributions
Corral, Álvaro; Font-Clos, Francesc
2017-08-01
Some authors have recently argued that a finite-size scaling law for the text-length dependence of word-frequency distributions cannot be conceptually valid. Here we give solid quantitative evidence for the validity of this scaling law, using both careful statistical tests and analytical arguments based on the generalized central-limit theorem applied to the moments of the distribution (and obtaining a novel derivation of Heaps' law as a by-product). We also find that the picture of word-frequency distributions with power-law exponents that decrease with text length [X. Yan and P. Minnhagen, Physica A 444, 828 (2016), 10.1016/j.physa.2015.10.082] does not stand with rigorous statistical analysis. Instead, we show that the distributions are perfectly described by power-law tails with stable exponents, whose values are close to 2, in agreement with the classical Zipf's law. Some misconceptions about scaling are also clarified.
Importance of calcium and magnesium in water - water hardening
Barloková, D.; Ilavský, J.; Kapusta, O.; Šimko, V.
2017-10-01
Basic information about importance of calcium and magnesium in water, about their properties, effect to human health, problems what can cause under the lower ( 5 mmol/L) concentrations in water supply distribution systems, the most commonly used methods of water hardening are presented. The article contains the water hardening results carried out during the pilot plant experiments in WTP Hriňová and WTP Turček. For water hardening, treated water at the end of the process line, i.e., after coagulation, sedimentation and filtration, saturated with CO2 and filtrated through half-burnt dolomite material (PVD) was used. The results show that the filtration rate is 17.1 m/h in the case of WTP Hriňová and 15.2 m/h in the case of WTP Turček to achieve the recommended concentration of Ca and Mg in the treated water after the addition of CO2 and filtration through PVD. The longer the water contact time with PVD (depending on the CO2 content), the more water is enriched with magnesium, but the calcium concentration has not so much increased.
Multi-material linearization beam hardening correction for computed tomography.
Lifton, J J
2017-03-03
Since beam hardening causes cupping and streaking artifacts in computed tomographic images, the presence of such artifacts can impair both qualitative and quantitative analysis of the reconstructed data. When the scanned object is composed of a single material, it is possible to correct beam hardening artifacts using the linearization method. However, for multi-material objects, an iterative segmentation-based correction algorithm is needed, which is not only computationally expensive, but may also fail if the initial segmentation result is poor. In this study, a new multi-material linearization beam hardening correction method was proposed and evaluated. The new method is fast and implemented in the same manner as a mono-material linearization. The correction takes approximately 0.02 seconds per projection. Although facing a potential disadvantage of requiring attenuation measurements of one of the object's constituent materials, applying the new method has demonstrated its capability for a multi-material workpiece with substantial reduction in both cupping and streaking artifacts. For example, the study showed that the absolute cupping artefacts in steel, titanium and aluminum spheres were reduced from 22%, 20% and 20% to 5%, 1% and 0%, respectively.
Residual stress analysis of drive shafts after induction hardening
Energy Technology Data Exchange (ETDEWEB)
Lemos, Guilherme Vieira Braga; Rocha, Alexandre da Silva; Nunes, Rafael Menezes, E-mail: lemos_gl@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Algre, RS (Brazil); Hirsch, Thomas Karl [Stiftung Institut für Werkstofftechnik (IWT), Bremen (Germany)
2014-08-15
Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were carried out by using a portable diffractometer, in order to avoid cutting the shafts and evaluate the original state of the stresses, and afterwards a more detailed analysis was realized by a conventional stationary diffractometer. The obtained results presented an overview of the surface residual stress profiles after induction hardening and displayed the influence of the straightening process on the redistribution of residual stresses. They also indicated that the effects of the straightening in the residual stresses cannot be neglected. (author)
Description of full-range strain hardening behavior of steels.
Li, Tao; Zheng, Jinyang; Chen, Zhiwei
2016-01-01
Mathematical expression describing plastic behavior of steels allows the execution of parametric studies for many purposes. Various formulas have been developed to characterize stress strain curves of steels. However, most of those formulas failed to describe accurately the strain hardening behavior of steels in the full range which shows various distinct stages. For this purpose, a new formula is developed based on the well-known Ramberg-Osgood formula to describe the full range strain hardening behavior of steels. Test results of all the six types of steels show a three-stage strain hardening behavior. The proposed formula can describe such behavior accurately in the full range using a single expression. The parameters of the formula can be obtained directly and easily through linear regression analysis. Excellent agreements with the test data are observed for all the steels tested. Furthermore, other formulas such as Ludwigson formula, Gardner formula, UGent formula are also applied for comparison. Finally, the proposed formula is considered to have wide suitability and high accuracy for all the steels tested.
Press Hardening Steel (PHS): a new coating and process technology
Energy Technology Data Exchange (ETDEWEB)
Faderl, J. [voestalpine Stahl Linz GmbH (Austria); Vehof, R. [Polynorm N.V., Bundschoten (Netherlands)
2005-07-01
Press hardening technology has been known for many years. Increased requirements with respect to safety and light weight construction of the steel body for cars and trucks force the automotive industry to use high strength steels more and more. Strength levels up to 1000 MPa can be provided with AHSS grades. Above 1000 MPa, these steel grades are coming to their limit with respect to strength vs. formability balance. PHS is a very attractive alternative concept. Hardenable 22MnB5 has been supplied - uncoated - for a long time. To avoid decarburization during heat treatment and to improve corrosion behaviour hot dip aluminized 22MnB5 was introduced to the market. Both materials, uncoated and hot dip aluminized, do not provide cathodic corrosion protection without postcoating (sheradizing..). In the last two years an improved press hardening technology and a zinc based coating providing cathodic protection was developed by voestalpine. Some results about strength homogeneity, formability, corrosion behaviour of this voestalpine-PHS technology will be presented in the paper. (orig.)
DEFF Research Database (Denmark)
Christensen, Martin Gram; Adler-Nissen, Jens
2015-01-01
This paper presents a normalization of the Biot number, which enables the Fourier exponents to be fitted with a simple 3rd order polynomial (R2 > 0.9999). The method is validated for Biot numbers ranging from 0.02 to 8, and presented graphically for both the Fourier exponents and the lag factors ...... needed in the series expansion. The lag factors and Fourier exponents are validated with an average variation coefficient (CVRMSD) less than 0.006. The resulting prediction error of the thermal response is ...This paper presents a normalization of the Biot number, which enables the Fourier exponents to be fitted with a simple 3rd order polynomial (R2 > 0.9999). The method is validated for Biot numbers ranging from 0.02 to 8, and presented graphically for both the Fourier exponents and the lag factors...
Garcin, Matthieu
2017-10-01
Hurst exponents depict the long memory of a time series. For human-dependent phenomena, as in finance, this feature may vary in the time. It justifies modelling dynamics by multifractional Brownian motions, which are consistent with time-dependent Hurst exponents. We improve the existing literature on estimating time-dependent Hurst exponents by proposing a smooth estimate obtained by variational calculus. This method is very general and not restricted to the sole Hurst framework. It is globally more accurate and easier than other existing non-parametric estimation techniques. Besides, in the field of Hurst exponents, it makes it possible to make forecasts based on the estimated multifractional Brownian motion. The application to high-frequency foreign exchange markets (GBP, CHF, SEK, USD, CAD, AUD, JPY, CNY and SGD, all against EUR) shows significantly good forecasts. When the Hurst exponent is higher than 0.5, what depicts a long-memory feature, the accuracy is higher.
Effective Power-Law Dependence of Lyapunov Exponents on the Central Mass in Galaxies
Delis, N.; Efthymiopoulos, C.; Kalapotharakos, C.
2015-01-01
Using both numerical and analytical approaches, we demonstrate the existence of an effective power-law relation L alpha m(sup p) between themean Lyapunov exponent L of stellar orbits chaotically scattered by a supermassive black hole (BH) in the centre of a galaxy and the mass parameter m, i.e. ratio of the mass of the BH over the mass of the galaxy. The exponent p is found numerically to obtain values in the range p approximately equals 0.3-0.5. We propose a theoretical interpretation of these exponents, based on estimates of local 'stretching numbers', i.e. local Lyapunov exponents at successive transits of the orbits through the BH's sphere of influence. We thus predict p = 2/3 - q with q approximately equaling 0.1-0.2. Our basic model refers to elliptical galaxy models with a central core. However, we find numerically that an effective power-law scaling of L with m holds also in models with central cusp, beyond a mass scale up to which chaos is dominated by the influence of the cusp itself. We finally show numerically that an analogous law exists also in disc galaxies with rotating bars. In the latter case, chaotic scattering by the BH affects mainly populations of thick tube-like orbits surrounding some low-order branches of the x(sub 1) family of periodic orbits, as well as its bifurcations at low-order resonances, mainly the inner Lindblad resonance and the 4/1 resonance. Implications of the correlations between L and m to determining the rate of secular evolution of galaxies are discussed.
Perturbation theory for Lyapunov exponents of an Anderson model on a strip
Schulz-Baldes, H
2003-01-01
It is proven that the localization length of an Anderson model on a strip of width $L$ is bounded above by $L/\\lambda^2$ for small values of the coupling constant $\\lambda$ of the disordered potential. For this purpose, a new formalism is developed in order to calculate the bottom Lyapunov exponent associated with random products of large symplectic matrices perturbatively in the coupling constant of the randomness.
Critical exponents in the transition to chaos in one-dimensional ...
Indian Academy of Sciences (India)
obey the relation λ. µ µ∞ ν. (1) where µ∞ is the value of the control parameter µ at the Feigenbaum point or accumulation point of period doubling transitions andν is the associated critical exponent. In the context of unimodal maps like the logistic map,ν is given by the Huberman–Rudnick (HR) relation ν(z) = ln 2 ln δ(z). (2).
The exponent λ (x,Q ) of the proton structure function F (x, Q ) at low ...
Indian Academy of Sciences (India)
Abstract. The exponent λ of the structure function F2 x λ is calculated using the solution of the DGLAP equation for gluon at low x reported recently by the present authors. The quantity λ is calculated both as a function of x at fixed Q2 and as a function of Q2 at fixed x and compared with the most recent data from H1.
Short Zero-Sum Sequences Over Abelian $p$-Groups of Large Exponent
Luo, Sammy
2016-01-01
Let $G$ be a finite abelian group with exponent $n$. Let $\\eta(G)$ denote the smallest integer $\\ell$ such that every sequence over $G$ of length at least $\\ell$ has a zero-sum subsequence of length at most $n$. We determine the precise value of $\\eta(G)$ when $G$ is a $p$-group whose Davenport constant is at most $2n-1$. This confirms one of the equalities in a conjecture by Schmid and Zhuang from 2010.
A Lower Bound on the Lyapunov Exponent for the Generalized Harper's Model
Jitomirskaya, Svetlana; Liu, Wencai
2017-02-01
We obtain a lower bound for the Lyapunov exponent of a family of discrete Schrödinger operators (Hu)_n=u_{n+1}+u_{n-1}+2a_1 cos 2π (θ +nα )u_n+2a_2 cos 4π (θ +nα )u_n, that incorporates both a_1 and a_2, thus going beyond the Herman's bound.
Energy Technology Data Exchange (ETDEWEB)
Pawlewicz, W.T.; Mann, I.B.; Martin, P.M.; Hays, D.D.; Graybeal, A.G.
1982-07-01
This report summarizes key results and accomplishements during the first year of a Manufacturing Methods and Technology project to adapt an existing Pacific Northwest Laboratory (PNL) optical coating capability developed for high-power fusion-laser applications to the case of rf and laser hardening of plastic missile domes used by the US Army (MICOM). The primary objective of the first year's work was to demonstrate rf hardening of Hellfire and Copperhead 1.06-micron missile domes by use of transparent conductive Indium Tin Oxide (ITO) coatings. The project thus involved adaptation of a coating material and process developed for flat glass components used in fusion lasers to the case of hemispherical or conical heat-sensitive plastic domes used on laser-guided missiles. Specific ITO coating property goals were an electrical sheet resistance of 10 Ohms/square, a coated-dome transmission of 80% or more at 1.06 micron wavelength (compared to 90% for a bare dome), and good adhesion. The sheet resistance goal of 10 Ohms/square was expected to result in an rf attenuation of 30 dB at the frequencies of importance.
Characterization of Tool Wear in High-Speed Milling of Hardened Powder Metallurgical Steels
Directory of Open Access Journals (Sweden)
Fritz Klocke
2011-01-01
Full Text Available In this experimental study, the cutting performance of ball-end mills in high-speed dry-hard milling of powder metallurgical steels was investigated. The cutting performance of the milling tools was mainly evaluated in terms of cutting length, tool wear, and cutting forces. Two different types of hardened steels were machined, the cold working steel HS 4-2-4 PM (K490 Microclean/66 HRC and the high speed steel HS 6-5-3 PM (S790 Microclean/64 HRC. The milling tests were performed at effective cutting speeds of 225, 300, and 400 m/min with a four fluted solid carbide ball-end mill (0 = 6, TiAlN coating. It was observed that by means of analytically optimised chipping parameters and increased cutting speed, the tool life can be drastically enhanced. Further, in machining the harder material HS 4-2-4 PM, the tool life is up to three times in regard to the less harder material HS 6-5-3 PM. Thus, it can be assumed that not only the hardness of the material to be machined plays a vital role for the high-speed dry-hard cutting performance, but also the microstructure and thermal characteristics of the investigated powder metallurgical steels in their hardened state.
Hardening and termination of long-duration γ rays detected prior to lightning.
Tsuchiya, H; Enoto, T; Iwata, K; Yamada, S; Yuasa, T; Kitaguchi, T; Kawaharada, M; Nakazawa, K; Kokubun, M; Kato, H; Okano, M; Tamagawa, T; Makishima, K
2013-07-05
We report the first observation of 3-30 MeV prolonged gamma-ray emission that was abruptly terminated by lightning. The gamma-ray detection was made during winter thunderstorms on December 30, 2010, by the Gamma-Ray Observation of Winter Thunderclouds experiment carried out in a coastal area along the Sea of Japan. The gamma-ray flux lasted for less than 3 min, continuously hardening closer to the lightning occurrence. The hardening at energies of 3-10 MeV energies was most prominent. The gamma-ray flux abruptly ceased less than 800 ms before the lightning flash that occurred over 5 km away from the experimental site. In addition, we observed a clear difference in the duration of the 3-10 MeV gamma rays and those >10 MeV, suggesting that the area of >10 MeV gamma-ray emission is considerably smaller than that of the lower-energy gamma rays. This work may give a manifestation that a local region emitting prolonged gamma rays connects with a distant region to initiate lightning.
A strain-hardening bi-power law for the nonlinear behaviour of biological soft tissues.
Nicolle, S; Vezin, P; Palierne, J-F
2010-03-22
Biological soft tissues exhibit a strongly nonlinear viscoelastic behaviour. Among parenchymous tissues, kidney and liver remain less studied than brain, and a first goal of this study is to report additional material properties of kidney and liver tissues in oscillatory shear and constant shear rate tests. Results show that the liver tissue is more compliant but more strain hardening than kidney. A wealth of multi-parameter mathematical models has been proposed for describing the mechanical behaviour of soft tissues. A second purpose of this work is to develop a new constitutive law capable of predicting our experimental data in the both linear and nonlinear viscoelastic regime with as few parameters as possible. We propose a nonlinear strain-hardening fractional derivative model in which six parameters allow fitting the viscoelastic behaviour of kidney and liver tissues for strains ranging from 0.01 to 1 and strain rates from 0.0151 s(-1) to 0.7s(-1). Copyright (c) 2009 Elsevier Ltd. All rights reserved.
Effect of raw materials and hardening process on hardness of manually forged knife
Balkhaya, Suwarno
2017-06-01
Knives are normally made by forging process either using a machine or traditional method by means of hammering process. This present work was conducted to study the effects of steel raw materials and hardening process on the hardness of manually forged knives. The knife samples were made by traditional hammering (forging) process done by local blacksmith. Afterward, the samples were heat treated with two different hardening procedures, the first was based on the blacksmith procedure and the second was systematically done at the laboratory. The forging was done in the temperature ranged between 900-950°C, while the final temperature ranged between 650-675°C. The results showed that knives made of spring steel and heat treated in simulated condition at the laboratory obtained higher level of hardness, i.e. 62 HRC. In general, knives heat treated by local blacksmith had lower level of hardness that those obtained from simulated condition. Therefore, we concluded that the traditional knife quality in term of hardness can be improved by optimizing the heat treatment schedule.
Scaling exponent and dispersity of polymers in solution by diffusion NMR.
Williamson, Nathan H; Röding, Magnus; Miklavcic, Stanley J; Nydén, Magnus
2017-05-01
Molecular mass distribution measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) spectroscopy currently require prior knowledge of scaling parameters to convert from polymer self-diffusion coefficient to molecular mass. Reversing the problem, we utilize the scaling relation as prior knowledge to uncover the scaling exponent from within the PGSE data. Thus, the scaling exponent-a measure of polymer conformation and solvent quality-and the dispersity (Mw/Mn) are obtainable from one simple PGSE experiment. The method utilizes constraints and parametric distribution models in a two-step fitting routine involving first the mass-weighted signal and second the number-weighted signal. The method is developed using lognormal and gamma distribution models and tested on experimental PGSE attenuation of the terminal methylene signal and on the sum of all methylene signals of polyethylene glycol in D2O. Scaling exponent and dispersity estimates agree with known values in the majority of instances, leading to the potential application of the method to polymers for which characterization is not possible with alternative techniques. Copyright © 2017 Elsevier Inc. All rights reserved.
Eller, Tom; Greve, L; Andres, M.T.; Medricky, M; Meinders, Vincent T.; van den Boogaard, Antonius H.
2016-01-01
In this article, an inverse FEM optimization strategy is proposed for identification of the strain hardening parameters of boron alloyed steel 22MnB5 in five different hardness grades. In the proposed elasto-plastic constitutive model, the strain hardening is represented by a nonlinear combination
Jones, Jennifer L.; Koul, Michelle G.; Schubbe, Joel J.
2014-06-01
A surface hardening technique called "interstitial hardening" is commercially available, whereby interstitial carbon atoms are introduced into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or fasteners would improve performance regarding cavitation and galling resistance, and has intensified interest in this process. However, there remains a need to characterize and validate the specific performance characteristics of the hardened materials. This paper describes experimental testing conducted on 316L stainless steel that has been surface hardened using available commercial techniques, using carbon as the interstitial atom. The corrosion performance of the hardened surface is assessed using electrochemical potentiodynamic testing to determine the breakdown potential in 3.5 wt.% NaCl solution to identify the most promising method. The hardness and thickness of the surface-hardened layer is characterized and compared using metallography and microhardness profiling. Corrosion fatigue and slow strain rate testing of untreated, hardened, and damaged, hardened surfaces exposed to ASTM seawater is conducted. Finally, critical galling stresses are determined and compared. Post-test examination of damage attempts to identify mechanisms of material failure and characterize how corrosion-assisted cracks initiate and grow in surface-hardened materials.
Coleman, E. A.; Bula, R. J.; Davis, R. L.
1966-01-01
Electrophoretic and immunological properties of the soluble root protein complement of 6 Medicago sativa L. genotypes in the cold hardened and non-hardened physiological condition were compared. These 6 genotypes were chosen to represent a range of abilities to survive exposure to subfreezing temperatures when in the cold hardened condition. A zone of highly charged and/or low molecular weight protein components were found to be more prevalent in the protein complements of the cold-hardened material than the non-hardened material. Immunodiffusion plate tests were not so definitive as the electrophoretic patterns for identifying the genotypes or physiological conditions, but did corroborate the electrophoretic interpretations. Images Fig. 2 PMID:16656458
Radiation Hardening by Software Techniques on FPGAs: Flight Experiment Evaluation and Results
Schmidt, Andrew G.; Flatley, Thomas
2017-01-01
We present our work on implementing Radiation Hardening by Software (RHBSW) techniques on the Xilinx Virtex5 FPGAs PowerPC 440 processors on the SpaceCube 2.0 platform. The techniques have been matured and tested through simulation modeling, fault emulation, laser fault injection and now in a flight experiment, as part of the Space Test Program- Houston 4-ISS SpaceCube Experiment 2.0 (STP-H4-ISE 2.0). This work leverages concepts such as heartbeat monitoring, control flow assertions, and checkpointing, commonly used in the High Performance Computing industry, and adapts them for use in remote sensing embedded systems. These techniques are extremely low overhead (typically radiation hardened processor. The recently concluded STP-H4 flight experiment was an opportunity to upgrade the RHBSW techniques for the Virtex5 FPGA and demonstrate them on-board the ISS to achieve TRL 7. This work details the implementation of the RHBSW techniques, that were previously developed for the Virtex4-based SpaceCube 1.0 platform, on the Virtex5-based SpaceCube 2.0 flight platform. The evaluation spans the development and integration with flight software, remotely uploading the new experiment to the ISS SpaceCube 2.0 platform, and conducting the experiment continuously for 16 days before the platform was decommissioned. The experiment was conducted on two PowerPCs embedded within the Virtex5 FPGA devices and the experiment collected 19,400 checkpoints, processed 253,482 status messages, and incurred 0 faults. These results are highly encouraging and future work is looking into longer duration testing as part of the STP-H5 flight experiment.
Directory of Open Access Journals (Sweden)
O. González Quintero
2008-05-01
Mechanic-thermal Treatments applied in this work: the combined hardening, combination of the hardening for plasticdeformation and the artificial age hardening.The objective of this study is to determine the gear forces and time of Mechanic-thermal Treatment influence in themechanical properties: micro hardness and depth of work hardening, of the outer layers of spur gears, obtaining amathematical statistical model that relates the variables before mentioned with the hardness of the superficial layers in steelof medium content of carbon spur gears whose chemical composition belongs together presently with the established oneswork.Key words: Gears, combined hardening, micro hardness, plastic deformation, aging.
Power spectral density and scaling exponent of high frequency global solar radiation sequences
Calif, Rudy; Schmitt, François G.; Huang, Yongxiang
2013-04-01
invariance: Iq(f) ~ f-?(q) , ?(q) is the scaling exponent. This allows to characterize the scaling behavior of a process: fractal or multifractal with intermittent properties. For q = 2, the Hilbert spectrum is defined. In this work, The data are collected at the University site of Guadeloupe, an island in the West Indies, located at 16°15 N latitude 60°30 W longitude. Our measurements sampled at 1 Hz were performed during one year period. The analyzed data present a power spectral density E(f) displaying a power law of the form E(f) ~ f-β with 1.6 ˜ β ˜ 2.2 for frequencies f ˜ 0.1 Hz, corresponding to time scales T × 10 s. Furthermore, global solar radiation data possesses multifractal properties. For comparison, other multifractal analysis techniques such as structure functions, MDFA, wavelet leaders are also used. This preliminary work set the basis for further investigation dedicated to simulate and forecast a sequence of solar energy fluctuation under different meteorological conditions, in the multifractal framework.
Directory of Open Access Journals (Sweden)
Li Weijuan
2016-09-01
Full Text Available In the present work, specimens prepared from coarse grained low carbon steel with different prestrains were baked and then, their bake hardening (BH property and internal friction were determined. TEM was used to characterize the dislocation structure in BH treated samples. The measurements of internal friction in prestrained samples and baked samples were carried out using a multifunctional internal friction apparatus. The results indicate that, in coarse grained low carbon steel, the bake hardening properties (BH values were negative, which were increased by increasing the prestrain from 2 to 5%, and then were decreased by increasing the prestrain from 5 to 10%. In the specimen with prestrain 5%, the BH value reached the maximum value and the height of Snoek-Köster peak was observed to be the maximum alike. With increasing the prestrain, both of the BH value and Snoek-Köster peak heights are similarly varied. It is concluded that Snoek-Köster and dislocation-enhanced Snoek peaks, caused by the interactions between interstitial solute carbon atoms and dislocations, can be used in further development of the bake hardening steels.
Safiuddin, Md; Raman, Sudharshan N; Zain, Muhammad Fauzi Mohd
2015-12-10
The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.
The effects of x-ray beam hardening on detective quantum efficiency and radiation dose
Wong, Molly Donovan; Wu, Xizeng; Liu, Hong
2011-01-01
The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15%...
Hardening of electromechanical properties in piezoceramics using a composite approach
K. V., Lalitha; Riemer, Lukas M.; Koruza, Jurij; Rödel, Jürgen
2017-07-01
Piezoelectric applications such as ultrasonic motors, transformers and therapeutic ultrasonics demand high power generation with low losses, which is facilitated by "hard" ferroelectrics. Hardening of piezoelectric properties, characterized by high mechanical quality factor (Qm), is usually achieved by doping with lower valence elements, thereby tailoring the domain wall dynamics. In the present study, we demonstrate a hardening mechanism by developing composites of 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3 (NBT-6BT) with ZnO inclusions, as an alternative to chemical modifications. A decrease in the saturation polarization and total strain, higher internal bias fields, lower hysteretic losses and a two-fold increase in Qm are observed in comparison to NBT-6BT. The composite with 0.1 mole ratio of ZnO exhibits the highest Qm of 320 with d33 = 125 pC/N and Kp = 0.29. A one-to-one correspondence between the increase in Qm and the decrease in the domain wall mobility is established from the ac field dependence of permittivity, in the framework of the Rayleigh law. A further increase in ZnO content beyond a mole ratio of 0.1 reduces Qm, but retains it at a higher level, as compared to NBT-6BT. The results are explained based on the poling-induced strain incompatibility between the matrix and the hard ZnO phase. This composite approach is therefore considered a generic hardening concept and can be extended to other ferroelectric systems.
The maraging steel corrosion properties with hardening of different kinds after double aging
Directory of Open Access Journals (Sweden)
L. V. Tarasenko
2014-01-01
Full Text Available The paper proposes to use high-strength corrosion-resistant maraging steels, which were developed for aircraft industry instead of carbon steel with coating to improve operation properties of the forcemeasuring resilient member in electronic strain-gauge balance.It examines the possibility to apply the martensitic-aging steels of Fe-Cr-Ni-Mo-Ti (ЭП678 and Fe-Cr-Ni-Mo-Cu-Nb (ЭП817 alloying systems. It was shown, that a traditional heat strain-hardening treatment including hardening and overageing of this steels provides combination of durability viscosity and corrosion- resistance, but at the same time it increases nonelastic effects and lowers the limit of elasticity because of reversing austenite formation. In this connection, it was proposed to use hardening with double aging i.e. main and low-temperature aging with no austenite formation as heat strainhardening treatment of steels for force-measuring resilient member. The goal of this work was to study the influence of double aging on the structure and properties of ЭП678 (06Х14Н6Д2МБТ and ЭП817 (03Х111Н10М2Т steels.The modes of double aging for ЭП817 steel were conformed to 4500С + 400 0С and 475 0С+ 400 0С, for ЭП678 steel – 530 0С + 500 0С. The structure and properties of hardened steels after main and double aging were compared.Metallographic analysis of samples after electrolytic etching was conducted with Leitz Metallovert microscope while the CamScan 4DV raster electronic microscope was used for Microroentgen-spectral analysis. The quantity of austenite was controlled with computerized setting DRON-4, the hardness was measured with ТК-2М instrument, corrosion-resistance was estimated with polarized curves, which were taken using a П-5848 potentiostat.The conducted research has shown, that double aging causes the additional hardening of steels due to disintegration of martensite and formation of dispersed Cu – corpuscles in ЭП817 steel and of Ni3Ti
Fatigue Hardening and Nucleation of Persistent Slip Bands in Copper
DEFF Research Database (Denmark)
Pedersen, Ole Bøcker; Winter, A. T.
1982-01-01
that there is a large volume fraction of obstacles to plastic flow which are essentially non-deformable and give rise to inclusion stresses of considerable magnitude. The much lower hardening rates in cycles after saturation when persistent slip bands have formed suggest a lower volume fraction of obstacles......, as is observed by transmission electron microscopy. A simple composite model involving an inclusion stress, a bowing stress and a passing, stress accounts for the workhardening rates semi-quantitatively in terms of observed dislocation microstructures. Possible implications for polycrystals are considered....
Rationale simplified hardening training and recreational complexes future teachers
Directory of Open Access Journals (Sweden)
Verbludov I.B.
2010-02-01
Full Text Available Distribution in the modern world epidemiological diseases are influenza and acute respiratory viral infections requires a search for simplified, effective preventive means. The main direction of prevention of these diseases is to strengthen and enhance the activities of the immune system. Strengthening the protective systems of the body is directly related to the constant holding of different types of hardening. This study illustrates the possibility of using quenching air and water in the independent exercise training and recreational facilities in all conditions of students.
Zhang, Chao; Li, Yue; Lin, Hongbo; Yang, Baojun
2015-11-01
Attenuating random noise is of great significance in seismic data processing. In recent years, time-frequency peak filtering (TFPF) has been successfully applied to seismic random noise attenuation field. However, a fixed window length (WL) is used in the conventional TFPF. Since a short WL in the TFPF is used to preserve signals while a long WL can eliminate random noise effectively, signal preserving and noise attenuation cannot be balanced by a fixed WL especially when the signal-to-noise ratio of the noisy seismic record is low. Thus, we need to divide a noisy signal into signal and noise segments before the filtering. Then a short WL is used to the signal segments to preserve signals and a long WL is chosen for noise segments to eliminate random noise. In this paper, we test the smoothness of signals and random noise in time using the Hurst exponent which is a statistic for representing smoothness characteristics of signals. The time-series of signals with higher smoothness which lead to larger Hurst exponent values, however random noise is a random series in time without fixed waveforms and thus its smoothness is low, so the signal and noise segments can be divided by the Hurst exponent values. After the segmentation, we can adopt different filtering WLs in the TFPF for different segments to make a trade-off between signal preserving and random noise attenuation. Synthetic and real data experiments demonstrate that the proposed method can remove random noise from seismic record and preserve reflection events effectively.
Microvoid formation and strain hardening in highly cross-linked polymer networks.
Mukherji, Debashish; Abrams, Cameron F
2008-11-01
Using molecular dynamics simulations of a generic model, we observe strain hardening in highly cross-linked polymer glasses under tensile deformation. We show that formation of microvoids, without bond breaking, constitutes the microscopic origins of strain hardening. A well-defined functional form is observed for the void size distribution that is consistent with voids in dense equilibrium Lennard-Jones particle packings, independent of strain. Microvoid-based strain hardening is not observed in a separate model with tetrahedral bond angle constraints, indicating that flexible cross-linkers are the key factor in the development of strain hardening behavior.
[Causes of re-emergence of Oncomelania snails in hardened ditches].
Ding, Zhao-Jun; Wui, Jia-Ping; Wang, Dao-Fen; Wei, Zhang-Yong; He, Bin; He, Ya-Lan; Yu, Yun-Song; Wan, Jun
2013-04-01
To understand the impact factors of the re-emergence of Oncomelania snails in hardened ditches so as to find out the measures to improve the effect of snail eradication. Thirteen infected townships from Jingmen City were randomly selected and investigated with the retrospective method and the field survey. All the data were analyzed for evaluating the effect of the hardened ditches on snail eradication and finding out the causes of the re-emergence of snails in hardened ditches After on-site investigation of 151 hardened ditches, the eradication rate of snail areas was 78.79%, and 71 ditches were founded with snails and the re-emergence rate was 47.02%. The major factors of the snail re-emergence were the spread of the snails from the upstream, the dilapidation of the hardened ditches, no using molluscicides before the hardened ditches, and the snails being brought by the engineering construction. The only hardened ditches can not eradicate the snails. We should manage an overall plan when processing the ditches hardening project, implementation with molluscicides before the project and strengthen the maintenance of the hardened ditches.
Physical and Thermodynamical Properties of Water Phases in Hardening Portland Cement Systems
DEFF Research Database (Denmark)
Hansen, T. Bæk
The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process.......The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process....
Radiation-Hardened Memristor-based Memory for Extreme Environments Project
National Aeronautics and Space Administration — NASA space exploration missions require radiation-hardened memory technologies that can survive and operate over a wide temperature range. Memristors...
Microstructural Influence on Dynamic Properties of Age Hardenable FeMnAl Alloys
2011-04-01
Hardening The aging temperature of 550°C is the most common aging temperature reported in this system.10,11,12,16,21,28 Kayak reported strength...AIME, Vol. 215, pp. 112-114 (1959). 10. Kayak , G. L., “Fe-Mn-Al Precipitation-Hardening Austenitic Alloys,” Met. Sc. And Heat Tr., Vol. 11, pp. 95...Hardenable Fe-Mn-Al-C Alloys,” Met. Trans A, vol. 21A, pp 5-11 (1990). 10. Kayak , G. L., “Fe-Mn-Al Precipitation-Hardening Austenitic Alloys,” Met. Sc. And
Lagrangian coherent structures and the smallest finite-time Lyapunov exponent
Haller, George; Sapsis, Themistoklis
2011-06-01
We point out that local minimizing curves, or troughs, of the smallest finite-time Lyapunov exponent (FTLE) field computed over a time interval [t0, t] and graphed over trajectory positions at time t mark attracting Lagrangian coherent structures (LCSs) at t. For two-dimensional area-preserving flows, we conclude that computing the largest forward-time FTLE field by itself is sufficient for locating both repelling LCSs at t0 and attracting LCSs at t. We illustrate our results on analytic examples, as well as on a two-dimensional experimental velocity field measured near a swimming jellyfish.
Determination of the interfacial roughness exponent in rare-earth superlattices
DEFF Research Database (Denmark)
Swaddling, P.P.; McMorrow, D.F.; Cowley, R.A.
1994-01-01
The interfacial roughness in Ho/Y and Ho/Lu superlattices has been studied using high-resolution x-ray diffraction. The transverse width of the superlattice Bragg peaks broadens almost linearly as a function of the component of the reduced wave vector parallel to the growth direction, while...... the line shape is invariant, and is described by a Lorentzian raised to the power of approximate to 5/2. These results are interpreted as a signature of conformally rough interfaces, and the roughness exponent is determined to be alpha = 0.85 +/- 0.05. It is also shown how alpha may be altered by adjusting...
Estimation of Spectral Exponent Parameter of 1/f Process in Additive White Background Noise
Directory of Open Access Journals (Sweden)
Semih Ergintav
2007-01-01
Full Text Available An extension to the wavelet-based method for the estimation of the spectral exponent, γ, in a 1/fγ process and in the presence of additive white noise is proposed. The approach is based on eliminating the effect of white noise by a simple difference operation constructed on the wavelet spectrum. The γ parameter is estimated as the slope of a linear function. It is shown by simulations that the proposed method gives reliable results. Global positioning system (GPS time-series noise is analyzed and the results provide experimental verification of the proposed method.
Estimating the density-scaling exponent of a monatomic liquid from its pair potential
DEFF Research Database (Denmark)
Bøhling, Lasse; Bailey, Nicholas; Schrøder, Thomas
2014-01-01
This paper investigates two conjectures for calculating the density dependence of the density-scaling exponent γ of a single-component, pair-potential liquid with strong virial potential-energy correlations. The first conjecture gives an analytical expression for γ directly in terms of the pair...... potential. The second conjecture is a refined version of this involving the most likely nearest-neighbor distance determined from the pair-correlation function. The conjectures are tested by simulations of three systems, one of which is the standard Lennard-Jones liquid. While both expressions give...
Fractal dimensions of graph of Weierstrass-type function and local Hölder exponent spectra
Otani, Atsuya
2018-01-01
We study several fractal properties of the Weierstrass-type function where τ :[0, 1)\\to[0, 1) is a cookie cutter map with possibly fractal repeller, and λ and g are functions with proper regularity. In the first part, we determine the box dimension of the graph of W and Hausdorff dimension of its randomised version. In the second part, the Hausdorff spectrum of the local Hölder exponent is characterised in terms of thermodynamic formalism. Furthermore, in the randomised case, a novel formula for the lifted Hausdorff spectrum on the graph is provided.
Control of chaos in permanent magnet synchronous motor by using optimal Lyapunov exponents placement
Energy Technology Data Exchange (ETDEWEB)
Ataei, Mohammad, E-mail: ataei@eng.ui.ac.i [Department of Electrical Engineering, Faculty of Engineering, University of Isfahan, Hezar-Jerib St., Postal Code 8174673441, Isfahan (Iran, Islamic Republic of); Kiyoumarsi, Arash, E-mail: kiyoumarsi@eng.ui.ac.i [Department of Electrical Engineering, Faculty of Engineering, University of Isfahan, Hezar-Jerib St., Postal Code 8174673441, Isfahan (Iran, Islamic Republic of); Ghorbani, Behzad, E-mail: behzad.ghorbani63@gmail.co [Department of Control Engineering, Najafabad Azad University, Najafabad, Isfahan (Iran, Islamic Republic of)
2010-09-13
Permanent Magnet Synchronous Motor (PMSM) experiences chaotic behavior for a certain range of its parameters. In this case, since the performance of the PMSM degrades, the chaos should be eliminated. In this Letter, the control of the undesirable chaos in PMSM using Lyapunov exponents (LEs) placement is proposed that is also improved by choosing optimal locations of the LEs in the sense of predefined cost function. Moreover, in order to provide the physical realization of the method, nonlinear parameter estimator for the system is suggested. Finally, to show the effectiveness of the proposed methodology, the simulation results for applying this control strategy are provided.
The Use of the Lexical Exponents of Hypothetical Modality in Polish and Lithuanian
Directory of Open Access Journals (Sweden)
Danuta Roszko
2016-12-01
Full Text Available The Use of the Lexical Exponents of Hypothetical Modality in Polish and Lithuanian In this article the author focuses on the issue of hypothetical modality[1] in Polish and Lithuanian. A list of the basic exponents of hypothetical modality in both languages is presented. However, the focus is mainly placed on the lexical exponents. On the basis of one of the six groups, which describes a high degree of probability (H5, the differences between the use of the lexical exponents in both languages are examined. In the study, multilingual corpora resources, including The Polish-Lithuanian parallel corpus Clarin-PL., are utilized. [1] [In the academic literature, for the notion described herein, the term of epistemic modality is also used. Nevertheless, in this paper I will continue to use the term of hypotheticality, which I borrowed from the studies on modality, conducted in Polish-Bulgarian cooperation (Slavic Institute of Polish Academy of Sciences and Institute for Bulgarian Language of the Bulgarian Academy of Sciences.] O użyciu wykładników leksykalnych modalności hipotetycznej w językach polskim i litewskim W artykule autorka porusza zagadnienie modalności hipotetycznej[1] w językach polskim i litewskim. Przedstawia wykaz podstawowych wykładników modalności hipotetycznej w obu językach. Główną uwagę skupia jednak na wykładnikach leksykalnych. Na przykładzie jednej z sześciu grup, opisującej wysoki stopień prawdopodobieństwa (H5, omawia różnice użycia wykładników leksykalnych w obu językach. W badaniach wykorzystuje wielojęzyczne zasoby korpusowe, w tym Polsko-litewski korpus równoległy Clarin-PL. [1] [W literaturze przedmiotu na oznaczenie opisywanych tu treści stosowany jest również termin epistemiczności. Niemniej jednak w tej pracy autorka pozostaje przy terminie hipotetyczności, który zapożycza z badań nad modalnością, prowadzonych we współpracy polsko-bułgarskiej (Instytut Slawistyki PAN i
Probability density and scaling exponents of longitudinal structure functions in strong turbulence
Yakhot, V
1997-01-01
The advective terms in the Navier-Stokes and Burgers equations are similar. It is proposed that the longitudinal structure functions $S_{n}(r)$ in homogeneous and isotropic three- dimensional turbulence are goverened by a one-dimensional equation of motion, resembling the 1D-Burgers equation, with the strongly non-local pressure contributions accounted for by galilean-invariance-breaking terms. The resulting equations give both scaling exponents and amplitudes of the structure functions in an excellent agreement with experimental data. The derived probability density function $P(\\Delta u,r)\
Some comments on Hurst exponent and the long memory processes on capital markets
Sánchez Granero, M. A.; Trinidad Segovia, J. E.; García Pérez, J.
2008-09-01
The analysis of long memory processes in capital markets has been one of the topics in finance, since the existence of the market memory could implicate the rejection of an efficient market hypothesis. The study of these processes in finance is realized through Hurst exponent and the most classical method applied is R/S analysis. In this paper we will discuss the efficiency of this methodology as well as some of its more important modifications to detect the long memory. We also propose the application of a classical geometrical method with short modifications and we compare both approaches.
DEFF Research Database (Denmark)
Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A. O.
The characterization of the tensile behavior of strain hardening cementitious composites (SHCC) is of significant importance to the material design. In a previous work the tensile stress-crack opening response of different types of SHCC was characterized using notched specimens tested in direct...... tension, where a single crack was obtained and mechanically characterized by performing Single Crack Tension Test (SCTT). In this study the tensile behavior of SHCC materials is characterized under eccentric tensile load using the Compact Tension Test (CTT). The long edge notch placed in the rectangular...... plate specimens and the eccentrically applied tensile load create the local conditions necessary to the initiation of a single crack at the tip of the notch. Further propagation and opening of the crack in Mode I allow the assessment of the tensile load-displacement relationship. The experimental...
DEFF Research Database (Denmark)
Wu, Min; Johannesson, Björn
2014-01-01
The present work studied the impact of sample saturation on the analysis of pore volume and pore size distribution by low temperature (micro-)calorimetry. The theoretical background was examined, which emphasizes that the freezing/melting temperature of water/ice confined in non-fully saturated...... samples and a higher proportion of pores with small radii were found in the capillary saturated samples. In addition, the observed hysteresis between the freezing and melting curves of ice content of the capillary saturated samples was more pronounced than that of the vacuum saturated samples. The major...... pores is further depressed compared with that when the pores are fully saturated. The study of the experimental data on hardened concrete samples showed that for a same concrete mix, the total pore volume detected from the capillary saturated samples was always lower than that of the vacuum saturated...
Kiyani, K.; Chapman, S. C.; Hnat, B.
2006-11-01
We address the generic problem of extracting the scaling exponents of a stationary, self-affine process realized by a time series of finite length, where information about the process is not known a priori. Estimating the scaling exponents relies upon estimating the moments, or more typically structure functions, of the probability density of the differenced time series. If the probability density is heavy tailed, outliers strongly influence the scaling behavior of the moments. From an operational point of view, we wish to recover the scaling exponents of the underlying process by excluding a minimal population of these outliers. We test these ideas on a synthetically generated symmetric α -stable Lévy process and show that the Lévy exponent is recovered in up to the 6th order moment after only ˜0.1-0.5% of the data are excluded. The scaling properties of the excluded outliers can then be tested to provide additional information about the system.
3-D Temperature and Stress Simulations of Hardening Concrete
DEFF Research Database (Denmark)
Jensen, Poul; Buhr, Birit; Thorborg, Jesper
2003-01-01
When concrete is cast, heat develops. When the concrete cools down there is a risk that thermal gradients induce cracks in the structure. In the Middle East this is especially important as extensive heat builds up due to the high ambient temperatures. Possible formed cracks will have a detrimenta...... different structures where 3-D calculations are found to be required. Finally, the experience gained with the proposed hardening precautions is presented.......When concrete is cast, heat develops. When the concrete cools down there is a risk that thermal gradients induce cracks in the structure. In the Middle East this is especially important as extensive heat builds up due to the high ambient temperatures. Possible formed cracks will have a detrimental...... for the thermo-mechanical conditions during hydration of early age concrete. Material properties as a function of maturity and environmental conditions form the basis of the model. This paper presents temperature and stress calculation results using MAGMAconcrete, and proposed hardening precautions for two...
Dislocation Starvation and Exhaustion Hardening in Mo-alloy Nanofibers
Energy Technology Data Exchange (ETDEWEB)
Chisholm, Claire [University of California, Berkeley & LBNL; Bei, Hongbin [ORNL; Lowry, M. B. [University of California, Berkeley; Oh, Jason [Hysitron, Inc., MN; Asif, S.A. Syed [Hysitron, Inc., MN; Warren, O. [Hysitron, Inc., MN; Shan, Zhiwei [Xi' an Jiaotong University, China & Hysitron, Inc., MN; George, Easo P [ORNL; Minor, Andrew [University of California, Berkeley & LBNL
2012-01-01
The evolution of defects in Mo alloy nanofibers with initial dislocation densities ranging from 0 to 1.6 1014 m2 were studied using an in situ push-to-pull device in conjunction with a nanoindenter in a transmission electron microscope. Digital image correlation was used to determine stress and strain in local areas of deformation. When they had no initial dislocations the Mo alloy nanofibers suffered sudden catastrophic elongation following elastic deformation to ultrahigh stresses. At the other extreme fibers with a high dislocation density underwent sustained homogeneous deformation after yielding at much lower stresses. Between these two extremes nanofibers with intermediate dislocation densities demonstrated a clear exhaustion hardening behavior, where the progressive exhaustion of dislocations and dislocation sources increases the stress required to drive plasticity. This is consistent with the idea that mechanical size effects ( smaller is stronger ) are due to the fact that nanostructures usually have fewer defects that can operate at lower stresses. By monitoring the evolution of stress locally we find that exhaustion hardening causes the stress in the nanofibers to surpass the critical stress predicted for self-multiplication, supporting a plasticity mechanism that has been hypothesized to account for the rapid strain softening observed in nanoscale bcc materials at high stresses.
Origin of honeycombs: Testing the hydraulic and case hardening hypotheses
Bruthans, Jiří; Filippi, Michal; Slavík, Martin; Svobodová, Eliška
2018-02-01
Cavernous weathering (cavernous rock decay) is a global phenomenon, which occurs in porous rocks around the world. Although honeycombs and tafoni are considered to be the most common products of this complex process, their origin and evolution are as yet not fully understood. The two commonly assumed formation hypotheses - hydraulic and case hardening - were tested to elucidate the origin of honeycombs on sandstone outcrops in a humid climate. Mechanical and hydraulic properties of the lips (walls between adjacent pits) and backwalls (bottoms of pits) of the honeycombs were determined via a set of established and novel approaches. While the case hardening hypothesis was not supported by the determinations of either tensile strength, drilling resistance or porosity, the hydraulic hypothesis was clearly supported by field measurements and laboratory tests. Fluorescein dye visualization of capillary zone, vapor zone, and evaporation front upon their contact, demonstrated that the evaporation front reaches the honeycomb backwalls under low water flow rate, while the honeycomb lips remain dry. During occasional excessive water flow events, however, the evaporation front may shift to the lips, while the backwalls become moist as a part of the capillary zone. As the zone of evaporation corresponds to the zone of potential salt weathering, it is the spatial distribution of the capillary and vapor zones which dictates whether honeycombs are created or the rock surface is smoothed. A hierarchical model of factors related to the hydraulic field was introduced to obtain better insights into the process of cavernous weathering.
Effectiveness of SEL Hardening Strategies and the Latchup Domino Effect
Dodds, N. A.; Hooten, N. C.; Reed, R. A.; Schrimpf, R. D.; Warner, J. H.; Roche, N. J.-H.; McMorrow, D.; Wen, S.-J.; Wong, R.; Salzman, J. F.; Jordan, S.; Pellish, J. A.; Marshall, C. J.; Gaspard, N. J.; Bennett, W. G.; Zhang, E. X.; Bhuva, B. L.
2012-12-01
Heavy ion, neutron, and laser experimental data are used to evaluate the effectiveness of various single event latchup (SEL) hardening strategies, including silicon-on-insulator (SOI), triple well, and guard rings. Although SOI technology is widely reported to be immune to SEL, conventional pnpn latchup can occur and has been observed in non-dielectrically isolated SOI processes. Triple well technologies are shown to be more robust against SEL than dual well technologies under all conditions used in this study, suggesting that the introduction of a deep N-well is an excellent zero-area-penalty hardening strategy. A single guard ring is shown to be sufficient for SEL immunity in the 180 nm CMOS technology investigated, and is likely sufficient for more modern CMOS technologies. After triggering latchup in a certain pnpn region, latchup was observed to spread to neighboring pnpn regions, which then infected other more distant regions until it had spread over a total distance of 700 micrometers. We discuss the physical mechanism of this latchup domino effect and its implications for device characterization and hardness assurance.
The emergence of different tail exponents in the distributions of firm size variables
Ishikawa, Atushi; Fujimoto, Shouji; Watanabe, Tsutomu; Mizuno, Takayuki
2013-05-01
We discuss a mechanism through which inversion symmetry (i.e., invariance of a joint probability density function under the exchange of variables) and Gibrat’s law generate power-law distributions with different tail exponents. Using a dataset of firm size variables, that is, tangible fixed assets K, the number of workers L, and sales Y, we confirm that these variables have power-law tails with different exponents, and that inversion symmetry and Gibrat’s law hold. Based on these findings, we argue that there exists a plane in the three dimensional space (logK,logL,logY), with respect to which the joint probability density function for the three variables is invariant under the exchange of variables. We provide empirical evidence suggesting that this plane fits the data well, and argue that the plane can be interpreted as the Cobb-Douglas production function, which has been extensively used in various areas of economics since it was first introduced almost a century ago.
Lyapunov exponents and phase diagrams reveal multi-factorial control over TRAIL-induced apoptosis.
Aldridge, Bree B; Gaudet, Suzanne; Lauffenburger, Douglas A; Sorger, Peter K
2011-11-22
Receptor-mediated apoptosis proceeds via two pathways: one requiring only a cascade of initiator and effector caspases (type I behavior) and the second requiring an initiator-effector caspase cascade and mitochondrial outer membrane permeabilization (type II behavior). Here, we investigate factors controlling type I versus II phenotypes by performing Lyapunov exponent analysis of an ODE-based model of cell death. The resulting phase diagrams predict that the ratio of XIAP to pro-caspase-3 concentrations plays a key regulatory role: type I behavior predominates when the ratio is low and type II behavior when the ratio is high. Cell-to-cell variability in phenotype is observed when the ratio is close to the type I versus II boundary. By positioning multiple tumor cell lines on the phase diagram we confirm these predictions. We also extend phase space analysis to mutations affecting the rate of caspase-3 ubiquitylation by XIAP, predicting and showing that such mutations abolish all-or-none control over activation of effector caspases. Thus, phase diagrams derived from Lyapunov exponent analysis represent a means to study multi-factorial control over a complex biochemical pathway.
Directory of Open Access Journals (Sweden)
LaVar King Isaacson
2014-05-01
Full Text Available A computational procedure is developed to determine initial instabilities within a three-dimensional laminar boundary layer and to follow these instabilities in the streamwise direction through to the resulting intermittency exponents within a fully developed turbulent flow. The fluctuating velocity wave vector component equations are arranged into a Lorenz-type system of equations. The nonlinear time series solution of these equations at the fifth station downstream of the initial instabilities indicates a sequential outward burst process, while the results for the eleventh station predict a strong sequential inward sweep process. The results for the thirteenth station indicate a return to the original instability autogeneration process. The nonlinear time series solutions indicate regions of order and disorder within the solutions. Empirical entropies are defined from decomposition modes obtained from singular value decomposition techniques applied to the nonlinear time series solutions. Empirical entropic indices are obtained from the empirical entropies for two streamwise stations. The intermittency exponents are then obtained from the entropic indices for these streamwise stations that indicate the burst and autogeneration processes.
Adhi, H. A.; Wijaya, S. K.; Prawito; Badri, C.; Rezal, M.
2017-03-01
Stroke is one of cerebrovascular diseases caused by the obstruction of blood flow to the brain. Stroke becomes the leading cause of death in Indonesia and the second in the world. Stroke also causes of the disability. Ischemic stroke accounts for most of all stroke cases. Obstruction of blood flow can cause tissue damage which results the electrical changes in the brain that can be observed through the electroencephalogram (EEG). In this study, we presented the results of automatic detection of ischemic stroke and normal subjects based on the scaling exponent EEG obtained through detrended fluctuation analysis (DFA) using extreme learning machine (ELM) as the classifier. The signal processing was performed with 18 channels of EEG in the range of 0-30 Hz. Scaling exponents of the subjects were used as the input for ELM to classify the ischemic stroke. The performance of detection was observed by the value of accuracy, sensitivity and specificity. The result showed, performance of the proposed method to classify the ischemic stroke was 84 % for accuracy, 82 % for sensitivity and 87 % for specificity with 120 hidden neurons and sine as the activation function of ELM.
Cycle-expansion method for the Lyapunov exponent, susceptibility, and higher moments
Charbonneau, Patrick; Li, Yue Cathy; Pfister, Henry D.; Yaida, Sho
2017-09-01
Lyapunov exponents characterize the chaotic nature of dynamical systems by quantifying the growth rate of uncertainty associated with the imperfect measurement of initial conditions. Finite-time estimates of the exponent, however, experience fluctuations due to both the initial condition and the stochastic nature of the dynamical path. The scale of these fluctuations is governed by the Lyapunov susceptibility, the finiteness of which typically provides a sufficient condition for the law of large numbers to apply. Here, we obtain a formally exact expression for this susceptibility in terms of the Ruelle dynamical ζ function for one-dimensional systems. We further show that, for systems governed by sequences of random matrices, the cycle expansion of the ζ function enables systematic computations of the Lyapunov susceptibility and of its higher-moment generalizations. The method is here applied to a class of dynamical models that maps to static disordered spin chains with interactions stretching over a varying distance and is tested against Monte Carlo simulations.
Predicting the long tail of book sales: Unearthing the power-law exponent
Fenner, Trevor; Levene, Mark; Loizou, George
2010-06-01
The concept of the long tail has recently been used to explain the phenomenon in e-commerce where the total volume of sales of the items in the tail is comparable to that of the most popular items. In the case of online book sales, the proportion of tail sales has been estimated using regression techniques on the assumption that the data obeys a power-law distribution. Here we propose a different technique for estimation based on a generative model of book sales that results in an asymptotic power-law distribution of sales, but which does not suffer from the problems related to power-law regression techniques. We show that the proportion of tail sales predicted is very sensitive to the estimated power-law exponent. In particular, if we assume that the power-law exponent of the cumulative distribution is closer to 1.1 rather than to 1.2 (estimates published in 2003, calculated using regression by two groups of researchers), then our computations suggest that the tail sales of Amazon.com, rather than being 40% as estimated by Brynjolfsson, Hu and Smith in 2003, are actually closer to 20%, the proportion estimated by its CEO.
Evaluation of nonlinear properties of epileptic activity using largest Lyapunov exponent
Medvedeva, Tatiana M.; Lüttjohann, Annika; van Luijtelaar, Gilles; Sysoev, Ilya V.
2016-04-01
Absence seizures are known to be highly non-linear large amplitude oscillations with a well pronounced main time scale. Whilst the appearance of the main frequency is usually considered as a transition from noisy complex dynamics of baseline EEG to more regular absence activity, the dynamical properties of this type of epileptiformic activity in genetic absence models was not studied precisely. Here, the estimation of the largest Lyapunov exponent from intracranial EEGs of 10 WAG/Rij rats (genetic model of absence epilepsy) was performed. Fragments of 10 seizures and 10 episodes of on-going EEG each of 4 s length were used for each animal, 3 cortical and 2 thalamic channels were analysed. The method adapted for short noisy data was implemented. The positive values of the largest Lyapunov exponent were found as for baseline as for spike wave discharges (SWDs), with values for SWDs being significantly less than for on-going activity. Current findings may indicate that SWD is a chaotic process with a well pronounced main timescale rather than a periodic regime. Also, the absence activity was shown to be less chaotic than the baseline one.
Asymptotic scaling properties and estimation of the generalized Hurst exponents in financial data
Buonocore, R. J.; Aste, T.; Di Matteo, T.
2017-04-01
We propose a method to measure the Hurst exponents of financial time series. The scaling of the absolute moments against the aggregation horizon of real financial processes and of both uniscaling and multiscaling synthetic processes converges asymptotically towards linearity in log-log scale. In light of this we found appropriate a modification of the usual scaling equation via the introduction of a filter function. We devised a measurement procedure which takes into account the presence of the filter function without the need of directly estimating it. We verified that the method is unbiased within the errors by applying it to synthetic time series with known scaling properties. Finally we show an application to empirical financial time series where we fit the measured scaling exponents via a second or a fourth degree polynomial, which, because of theoretical constraints, have respectively only one and two degrees of freedom. We found that on our data set there is not clear preference between the second or fourth degree polynomial. Moreover the study of the filter functions of each time series shows common patterns of convergence depending on the momentum degree.
Fuwape, Ibiyinka A.; Ogunjo, Samuel T.
2016-12-01
Radio refractivity index is used to quantify the effect of atmospheric parameters in communication systems. Scaling and dynamical complexities of radio refractivity across different climatic zones of Nigeria have been studied. Scaling property of the radio refractivity across Nigeria was estimated from the Hurst Exponent obtained using two different scaling methods namely: The Rescaled Range (R/S) and the detrended fluctuation analysis(DFA). The delay vector variance (DVV), Largest Lyapunov Exponent (λ1) and Correlation Dimension (D2) methods were used to investigate nonlinearity and the results confirm the presence of deterministic nonlinear profile in the radio refractivity time series. The recurrence quantification analysis (RQA) was used to quantify the degree of chaoticity in the radio refractivity across the different climatic zones. RQA was found to be a good measure for identifying unique fingerprint and signature of chaotic time series data. Microwave radio refractivity was found to be persistent and chaotic in all the study locations. The dynamics of radio refractivity increases in complexity and chaoticity from the Coastal region towards the Sahelian climate. The design, development and deployment of robust and reliable microwave communication link in the region will be greatly affected by the chaotic nature of radio refractivity in the region.
An outbreak of contact dermatitis from toluenesulfonamide formaldehyde resin in a nail hardener
de Wit, F. S.; de Groot, A. C.; Weyland, J. W.; Bos, J. D.
1988-01-01
8 cases of contact dermatitis from toluenesulfonamide formaldehyde resin in a nail hardener are presented. Most patients had used nail lacquers containing this resin for many years without trouble, but became sensitized to the resin shortly after the introduction of this particular nail hardener. A
Geijselaers, Hubertus J.M.
2003-01-01
The properties of many engineeringmaterialsmay be favourablymodified by application of a suitable heat treatment. Examples are precipitation hardening, tempering and annealing. One of the most important treatments is the transformation hardening of steel. Steel is an alloy of iron and carbon. At
DEFF Research Database (Denmark)
Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.
2012-01-01
The process of designing Strain Hardening Cementitious Composites (SHCC) is driven by the need to achieve certain performance parameters in tension. These are typically the pseudo-strain hardening behavior and the ability to develop multiple cracks. The assessment of the tensile load-deformation ...
DEFF Research Database (Denmark)
Hansen, Kurt Kielsgaard; Baroghel, V.B.; Künzel, H.M.
1996-01-01
Cumulated pore size distributions for hardened cement pastes measured by mercury intrusion porosimetry from two laboratories and low temperature microcalorimetry from one laboratory are presented.......Cumulated pore size distributions for hardened cement pastes measured by mercury intrusion porosimetry from two laboratories and low temperature microcalorimetry from one laboratory are presented....
The effects of x-ray beam hardening on detective quantum efficiency and radiation dose.
Wong, Molly Donovan; Wu, Xizeng; Liu, Hong
2011-01-01
The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The ability to decrease the risk of harmful radiation to the patient without compromising the detection capability would more effectively balance the tradeoff between image quality and radiation dose, and therefore benefit the fields of diagnostic x-ray imaging, especially mammography. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality.
Bahadur, H.; Parshad, R.
1983-01-01
The paper reports some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening. The present results show how the frequency shift in quartz crystals can be influenced by heat processing prior to irradiation and how this procedure can lead to radiation hardening for obtaining precise frequencies and time intervals from quartz oscillators in space.
MOULDING MIXTURES HARDENING PROCESS BASED ON LIGNIN-BASE SULPHONATE BINDER
Directory of Open Access Journals (Sweden)
V. N. Ektova
2004-01-01
Full Text Available Hardening of agglutinant sands on lignosulphonate binding agent is the result of two processes: oxidation-reduction in the system lignosulphonate acids — persulfuric natrium in the early stages of hardening and hydration of cement in the latter stages.
A 130 nm radiation hardened flip—flop with an annular gate and a C-element
Lei, Wang; Jianhua, Jiang; Yiming, Xiang; Yumei, Zhou
2014-01-01
This paper presents a radiation hardened flip—flop with an annular gate and a Muller C-element. The proposed cell has multiple working modes which can be used in different situations. Each part of the cell can be verified easily and completely by using different modes. This cell has been designed under an SMIC 0.13 μm process and 3-D simulated by using Synopsys TCAD. Heavy-ion testing has been done on the cell and its counterparts. The test results demonstrate that the presented cell reduces the cell's saturation cross section by approximately two orders of magnitude with little penalty on performance.
Directory of Open Access Journals (Sweden)
Cheung Noé
2004-01-01
Full Text Available The aim of this work is to develop a mathematical model to predict the depth of laser treated zone in the LTH process. The Fourier equation of heat conduction is solved by using the Finite Difference Method in cylindrical coordinates in order to study the temperature distribution produced in a workpiece and hence to obtain the depth to which hardening occurs. The theoretical simulations are compared with results produced experimentally by a CO2 laser operating in continuous wave, showing good agreement.
Directory of Open Access Journals (Sweden)
Michelle Leali Costa
2005-03-01
Full Text Available Composite structures for aerospace applications are mainly made by the well-known prepreg technology. In order to achieve adequate prepreg processing schedules, and consequently maximum fiber strength utilization, one has to know in deep the cure kinetics of matrix, which held the fibers together. This work describes a procedure to study the cure kinetic and has as example how aromatic amine hardeners influence the cure kinetics of an epoxy resin used in advanced composites. The investigation was carried out by using the DSC technique and it was found that depending on the system used the cure kinetics of the formulation obeys order n or autocatalytic order.
Evaluation of Springback for DP980 S Rail Using Anisotropic Hardening Models
Choi, Jisik; Lee, Jinwoo; Bae, Gihyun; Barlat, Frederic; Lee, Myoung-Gyu
2016-07-01
The effect of anisotropic hardening models on springback of an S-rail part was investigated. Two advanced constitutive models based on distortional and kinematic hardening, which captured the Bauschinger effect, transient hardening, and permanent softening during strain path change, were implemented in a finite element (FE) code. In-plane compression-tension tests were performed to identify the model parameters. The springback of the S-rail after forming a 980 MPa dual-phase steel sheet sample was measured and analyzed using different hardening models. The comparison between experimental and FE results demonstrated that the advanced anisotropic hardening models, which are particularly suitable for non-proportional loading, significantly improved the springback prediction capability of an advanced high strength steel.
Energy Technology Data Exchange (ETDEWEB)
Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo [Sogang Univ., Seoul (Korea, Republic of)
2013-10-15
In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.
Luo, Shouhua; Wu, Huazhen; Sun, Yi; Li, Jing; Li, Guang; Gu, Ning
2017-03-01
The beam hardening effect can induce strong artifacts in CT images, which result in severely deteriorated image quality with incorrect intensities (CT numbers). This paper develops an effective and efficient beam hardening correction algorithm incorporated in a filtered back-projection based maximum a posteriori (BHC-FMAP). In the proposed algorithm, the beam hardening effect is modeled and incorporated into the forward-projection of the MAP to suppress beam hardening induced artifacts, and the image update process is performed by Feldkamp-Davis-Kress method based back-projection to speed up the convergence. The proposed BHC-FMAP approach does not require information about the beam spectrum or the material properties, or any additional segmentation operation. The proposed method was qualitatively and quantitatively evaluated using both phantom and animal projection data. The experimental results demonstrate that the BHC-FMAP method can efficiently provide a good correction of beam hardening induced artefacts.
Research on SEU hardening of heterogeneous Dual-Core SoC
Huang, Kun; Hu, Keliu; Deng, Jun; Zhang, Tao
2017-08-01
The implementation of Single-Event Upsets (SEU) hardening has various schemes. However, some of them require a lot of human, material and financial resources. This paper proposes an easy scheme on SEU hardening for Heterogeneous Dual-core SoC (HD SoC) which contains three techniques. First, the automatic Triple Modular Redundancy (TMR) technique is adopted to harden the register heaps of the processor and the instruction-fetching module. Second, Hamming codes are used to harden the random access memory (RAM). Last, a software signature technique is applied to check the programs which are running on CPU. The scheme need not to consume additional resources, and has little influence on the performance of CPU. These technologies are very mature, easy to implement and needs low cost. According to the simulation result, the scheme can satisfy the basic demand of SEU-hardening.
Exact Critical Exponents for the Antiferromagnetic Quantum Critical Metal in Two Dimensions
Schlief, Andres; Lunts, Peter; Lee, Sung-Sik
2017-04-01
Unconventional metallic states which do not support well-defined single-particle excitations can arise near quantum phase transitions as strong quantum fluctuations of incipient order parameters prevent electrons from forming coherent quasiparticles. Although antiferromagnetic phase transitions occur commonly in correlated metals, understanding the nature of the strange metal realized at the critical point in layered systems has been hampered by a lack of reliable theoretical methods that take into account strong quantum fluctuations. We present a nonperturbative solution to the low-energy theory for the antiferromagnetic quantum critical metal in two spatial dimensions. Being a strongly coupled theory, it can still be solved reliably in the low-energy limit as quantum fluctuations are organized by a new control parameter that emerges dynamically. We predict the exact critical exponents that govern the universal scaling of physical observables at low temperatures.
Universal Scaling and Critical Exponents of the Anisotropic Quantum Rabi Model
Liu, Maoxin; Chesi, Stefano; Ying, Zu-Jian; Chen, Xiaosong; Luo, Hong-Gang; Lin, Hai-Qing
2017-12-01
We investigate the quantum phase transition of the anisotropic quantum Rabi model, in which the rotating and counterrotating terms are allowed to have different coupling strengths. The model interpolates between two known limits with distinct universal properties. Through a combination of analytic and numerical approaches, we extract the phase diagram, scaling functions, and critical exponents, which determine the universality class at finite anisotropy (identical to the isotropic limit). We also reveal other interesting features, including a superradiance-induced freezing of the effective mass and discontinuous scaling functions in the Jaynes-Cummings limit. Our findings are extended to the few-body quantum phase transitions with N >1 spins, where we expose the same effective parameters, scaling properties, and phase diagram. Thus, a stronger form of universality is established, valid from N =1 up to the thermodynamic limit.
Importance sampling with imperfect cloning for the computation of generalized Lyapunov exponents
Anteneodo, Celia; Camargo, Sabrina; Vallejos, Raúl O.
2017-12-01
We revisit the numerical calculation of generalized Lyapunov exponents, L (q ) , in deterministic dynamical systems. The standard method consists of adding noise to the dynamics in order to use importance sampling algorithms. Then L (q ) is obtained by taking the limit noise-amplitude → 0 after the calculation. We focus on a particular method that involves periodic cloning and pruning of a set of trajectories. However, instead of considering a noisy dynamics, we implement an imperfect (noisy) cloning. This alternative method is compared with the standard one and, when possible, with analytical results. As a workbench we use the asymmetric tent map, the standard map, and a system of coupled symplectic maps. The general conclusion of this study is that the imperfect-cloning method performs as well as the standard one, with the advantage of preserving the deterministic dynamics.
Parametric Stability of Non-Linearly Elastic Composite Plates by Lyapunov Exponents
GILAT, R.; ABOUDI, J.
2000-08-01
The dynamic stability of non-linearly elastic composite plates subjected to periodic in-plane loading is investigated. Infinitely wide plates made of resin matrix composite are considered. The non-linearly elastic behavior of the resin matrix is modelled by the generalized Ramberg-Osgood representation. The effect of the matrix non-linearity on the overall response of the composite is predicted by the micromechanical method of cells. The dynamic stability analysis is performed by evaluating the largest Lyapunov exponent, the sign of which indicates whether the system is stable or not. It is shown that this approach forms a convenient tool for predicting parametric stability of non-linear composite structures.
Fractality Evidence and Long-Range Dependence on Capital Markets: a Hurst Exponent Evaluation
Oprean, Camelia; Tănăsescu, Cristina
2014-07-01
Since the existence of market memory could implicate the rejection of the efficient market hypothesis, the aim of this paper is to find any evidence that selected emergent capital markets (eight European and BRIC markets, namely Hungary, Romania, Estonia, Czech Republic, Brazil, Russia, India and China) evince long-range dependence or the random walk hypothesis. In this paper, the Hurst exponent as calculated by R/S fractal analysis and Detrended Fluctuation Analysis is our measure of long-range dependence in the series. The results reinforce our previous findings and suggest that if stock returns present long-range dependence, the random walk hypothesis is not valid anymore and neither is the market efficiency hypothesis.
Energy Technology Data Exchange (ETDEWEB)
Look, Nicole [Department of Applied Mathematics, University of Colorado Boulder, Boulder, Colorado 80309 (United States); Arellano, Christopher J.; Grabowski, Alena M.; Kram, Rodger [Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado 80309 (United States); McDermott, William J. [The Orthopedic Specialty Hospital, Murray, Utah 84107 (United States); Bradley, Elizabeth [Department of Computer Science, University of Colorado Boulder, Boulder, Colorado 80309, USA and Santa Fe Institute, Santa Fe, New Mexico 87501 (United States)
2013-12-15
In this paper, we study dynamic stability during running, focusing on the effects of speed, and the use of a leg prosthesis. We compute and compare the maximal Lyapunov exponents of kinematic time-series data from subjects with and without unilateral transtibial amputations running at a wide range of speeds. We find that the dynamics of the affected leg with the running-specific prosthesis are less stable than the dynamics of the unaffected leg and also less stable than the biological legs of the non-amputee runners. Surprisingly, we find that the center-of-mass dynamics of runners with two intact biological legs are slightly less stable than those of runners with amputations. Our results suggest that while leg asymmetries may be associated with instability, runners may compensate for this effect by increased control of their center-of-mass dynamics.
Analysis of the Emergence in Swarm Model Based on Largest Lyapunov Exponent
Directory of Open Access Journals (Sweden)
Yu Wu
2011-01-01
Full Text Available Emergent behaviors of collective intelligence systems, exemplified by swarm model, have attracted broad interests in recent years. However, current research mostly stops at observational interpretations and qualitative descriptions of emergent phenomena and is essentially short of quantitative analysis and evaluation. In this paper, we conduct a quantitative study on the emergence of swarm model by using chaos analysis of complex dynamic systems. This helps to achieve a more exact understanding of emergent phenomena. In particular, we evaluate the emergent behaviors of swarm model quantitatively by using the chaos and stability analysis of swarm model based on largest Lyapunov exponent. It is concluded that swarm model is at the edge of chaos when emergence occurs, and whether chaotic or stable at the beginning, swarm model will converge to stability with the elapse of time along with interactions among agents.
Look, Nicole; Arellano, Christopher J.; Grabowski, Alena M.; McDermott, William J.; Kram, Rodger; Bradley, Elizabeth
2013-12-01
In this paper, we study dynamic stability during running, focusing on the effects of speed, and the use of a leg prosthesis. We compute and compare the maximal Lyapunov exponents of kinematic time-series data from subjects with and without unilateral transtibial amputations running at a wide range of speeds. We find that the dynamics of the affected leg with the running-specific prosthesis are less stable than the dynamics of the unaffected leg and also less stable than the biological legs of the non-amputee runners. Surprisingly, we find that the center-of-mass dynamics of runners with two intact biological legs are slightly less stable than those of runners with amputations. Our results suggest that while leg asymmetries may be associated with instability, runners may compensate for this effect by increased control of their center-of-mass dynamics.
Toward Synthesis of Solar Wind and Geomagnetic Scaling Exponents: a Fractional Levy Motion Model
Watkins, N. W.; Credgington, D.; Hnat, B.; Freeman, M. P.; Chapman, S. C.; Greenhough, J.
2005-12-01
Mandelbrot introduced the concept of fractals to describe the non-Euclidean shape of many aspects of the natural world. In the time series context he proposed the use of fractional Brownian motion (fBm) to model non-negligible temporal persistence, the ``Joseph Effect"; and Lévy flights to quantify large discontinuities, the ``Noah Effect". In space physics, both effects are manifested in the intermittency and long-range correlation which are by now well-established features of geomagnetic indices and their solar wind drivers. In order to capture and quantify the Noah and Joseph effects in one compact model we propose the application of the ``bridging" fractional Lévy motion (fLm) to space physics. We perform an initial evaluation of some previous scaling results in this paradigm, and show how fLm can model the previously observed exponents. We suggest some new directions for the future.
On the improvement of Wiener attack on RSA with small private exponent.
Wu, Mu-En; Chen, Chien-Ming; Lin, Yue-Hsun; Sun, Hung-Min
2014-01-01
RSA system is based on the hardness of the integer factorization problem (IFP). Given an RSA modulus N = pq, it is difficult to determine the prime factors p and q efficiently. One of the most famous short exponent attacks on RSA is the Wiener attack. In 1997, Verheul and van Tilborg use an exhaustive search to extend the boundary of the Wiener attack. Their result shows that the cost of exhaustive search is 2r + 8 bits when extending the Weiner's boundary r bits. In this paper, we first reduce the cost of exhaustive search from 2r + 8 bits to 2r + 2 bits. Then, we propose a method named EPF. With EPF, the cost of exhaustive search is further reduced to 2r - 6 bits when we extend Weiner's boundary r bits. It means that our result is 2(14) times faster than Verheul and van Tilborg's result. Besides, the security boundary is extended 7 bits.
Karki, Pragalv; Loh, Yen Lee
2016-11-02
We simulate three types of random inductor-capacitor (LC) networks on [Formula: see text] square lattices. We calculate the dynamical conductivity using an equation-of-motion method in which timestep error is eliminated and windowing error is minimized. We extract the critical exponent a such that [Formula: see text] at low frequencies. The results suggest that there are three different universality classes. The [Formula: see text] model, with capacitances from each site to ground, has a = 0.314(4). The [Formula: see text] model, with capacitances along bonds, has a = 0. The [Formula: see text] model, with both types of capacitances, has a = 0.304(1). This implies that classical percolative 2D superconductor-insulator transitions (SITs) generically have [Formula: see text] as [Formula: see text]. Therefore, any experiments that give a constant conductivity as [Formula: see text] must be explained in terms of quantum effects.
Identifying Vulnerabilities and Hardening Attack Graphs for Networked Systems
Energy Technology Data Exchange (ETDEWEB)
Saha, Sudip; Vullinati, Anil K.; Halappanavar, Mahantesh; Chatterjee, Samrat
2016-09-15
We investigate efficient security control methods for protecting against vulnerabilities in networked systems. A large number of interdependent vulnerabilities typically exist in the computing nodes of a cyber-system; as vulnerabilities get exploited, starting from low level ones, they open up the doors to more critical vulnerabilities. These cannot be understood just by a topological analysis of the network, and we use the attack graph abstraction of Dewri et al. to study these problems. In contrast to earlier approaches based on heuristics and evolutionary algorithms, we study rigorous methods for quantifying the inherent vulnerability and hardening cost for the system. We develop algorithms with provable approximation guarantees, and evaluate them for real and synthetic attack graphs.
Micromilling of hardened tool steel for mould making applications
DEFF Research Database (Denmark)
Bissacco, Giuliano; Hansen, Hans Nørgaard; De Chiffre, Leonardo
2005-01-01
geometries as those characterizing injection moulding moulds. The realization of the micromilling process in connection with hardened tool steel as workpiece material is particularly challenging. The low strength of the miniaturized end mills implies reduction and accurate control of the chip load which......The implementation of replication techniques for mass production of micro components relies on the availability of tooling technologies for manufacturing of tools and moulds. Micromilling is a suitable technique for manufacturing of microstructures characterized by high aspect ratios and complex...... requires high positioning accuracy. Size effects, mainly related to the microstructure of the workpiece material and to the limited scalability of tool geometry and surface topography, critically influence the performance of the process in terms of part accuracy, surface roughness, cutting forces and tool...
Radiation Hardened NULL Convention Logic Asynchronous Circuit Design
Directory of Open Access Journals (Sweden)
Liang Zhou
2015-10-01
Full Text Available This paper proposes a radiation hardened NULL Convention Logic (NCL architecture that can recover from a single event latchup (SEL or single event upset (SEU fault without deadlock or any data loss. The proposed architecture is analytically proved to be SEL resistant, and by extension, proved to be SEU resistant. The SEL/SEU resistant version of a 3-stage full-word pipelined NCL 4 × 4 unsigned multiplier was implemented using the IBM cmrf8sf 130 nm 1.2 V process at the transistor level and simulated exhaustively with SEL fault injection to validate the proposed architectures. Compared with the original version, the SEL/SEU resilient version has 1.31× speed overhead, 2.74× area overhead, and 2.79× energy per operation overhead.
Absorption Angstrom Exponent in AERONET and related data as an indicator of aerosol composition
Directory of Open Access Journals (Sweden)
P. B. Russell
2010-02-01
Full Text Available Recent results from diverse air, ground, and laboratory studies using both radiometric and in situ techniques show that the fractions of black carbon, organic matter, and mineral dust in atmospheric aerosols determine the wavelength dependence of absorption (often expressed as Absorption Angstrom Exponent, or AAE. Taken together, these results hold promise of improving information on aerosol composition from remote measurements. The main purpose of this paper is to show that AAE values for an Aerosol Robotic Network (AERONET set of retrievals from Sun-sky measurements describing full aerosol vertical columns are also strongly correlated with aerosol composition or type. In particular, we find AAE values near 1 (the theoretical value for black carbon for AERONET-measured aerosol columns dominated by urban-industrial aerosol, larger AAE values for biomass burning aerosols, and the largest AAE values for Sahara dust aerosols. These AERONET results are consistent with results from other, very different, techniques, including solar flux-aerosol optical depth (AOD analyses and airborne in situ analyses examined in this paper, as well as many other previous results. Ambiguities in aerosol composition or mixtures thereof, resulting from intermediate AAE values, can be reduced via cluster analyses that supplement AAE with other variables, for example Extinction Angstrom Exponent (EAE, which is an indicator of particle size. Together with previous results, these results strengthen prospects for determining aerosol composition from space, for example using the Glory Aerosol Polarimetry Sensor (APS, which seeks to provide retrievals of multiwavelength single-scattering albedo (SSA and aerosol optical depth (and therefore aerosol absorption optical depth (AAOD and AAE, as well as shape and other aerosol properties. Multidimensional cluster analyses promise additional information content, for example by using the Ozone Monitoring Instrument (OMI to add AAOD
An early prediction of 25th solar cycle using Hurst exponent
Singh, A. K.; Bhargawa, Asheesh
2017-11-01
The analysis of long memory processes in solar activity, space weather and other geophysical phenomena has been a major issue even after the availability of enough data. We have examined the data of various solar parameters like sunspot numbers, 10.7 cm radio flux, solar magnetic field, proton flux and Alfven Mach number observed for the year 1976-2016. We have done the statistical test for persistence of solar activity based on the value of Hurst exponent (H) which is one of the most classical applied methods known as rescaled range analysis. We have discussed the efficiency of this methodology as well as prediction content for next solar cycle based on long term memory. In the present study, Hurst exponent analysis has been used to investigate the persistence of above mentioned (five) solar activity parameters and a simplex projection analysis has been used to predict the ascension time and the maximum number of counts for 25th solar cycle. For available dataset of the year 1976-2016, we have calculated H = 0.86 and 0.82 for sunspot number and 10.7 cm radio flux respectively. Further we have calculated maximum number of counts for sunspot numbers and F10.7 cm index as 102.8± 24.6 and 137.25± 8.9 respectively. Using the simplex projection analysis, we have forecasted that the solar cycle 25th would start in the year 2021 (January) and would last up to the year 2031 (September) with its maxima in June 2024.
Characterization and hardening of concrete with ultrasonic testing.
del Río, L M; Jiménez, A; López, F; Rosa, F J; Rufo, M M; Paniagua, J M
2004-04-01
In this study, we describe a technique which can be used to characterize some relevant properties of 26 cylindrical samples (15 x 30 cm2) of concrete. The characterization has been performed, according to Spanish regulations in force, by some destructive and ultrasound-based techniques using frequencies of 40 kHz. Samples were manufactured using different water/cement ratios (w/c), ranging from 0.48 to 0.80, in order to simulate different values of compressive strength at each sample. We have correlated the propagation velocity v of ultrasonic waves through the samples to compressive strength R values. As some other authors remark, there exists an exponential relationship between the two above parameters. We have found that a highly linear relationship is present between R and w/c concentration at the samples. Nevertheless, when the same linear model is adopted to describe the relationship between v and w/c, the value of r decreases significantly. Thus, we have performed a multiple regression analysis which takes into account the impact of different concrete constituents (water, cement, sand, etc.) on ultrasound propagation speed. One of the most relevant practical issues addressed in our study is the estimation of the hardening curve of concrete, which can be used to quantify the viability of applying the proposed method in a real scenario. Subsequently, we also show a detailed analysis of the temporal evolution of v and R through 61 days, beginning at the date where the samples were manufactured. After analyzing both parameters separately, a double reciprocal relationship is deduced. Using the above parameters, we develop an NDE-based model which can be used to estimate hardening time of concrete samples.
Energy Technology Data Exchange (ETDEWEB)
Haddad, N.; Brown, R.; Cronauer, T.; Phan, H. [Lockheed Martin Space Electronics and Communications, Manassas, VA (United States)
1999-07-01
A high performance radiation hardened 32-bit RISC microprocessor based upon a commercial single chip CPU has been developed. This paper presents the features of radiation hardened microprocessor, the methods used to radiation harden this device, the results of radiation testing, and shows that the RAD6000 is well-suited for the vast majority of space applications. (authors)
Directory of Open Access Journals (Sweden)
A. I. Mihluk
2010-01-01
Full Text Available The new approach for technology of volumetric – superficial hardening of gear details of the back axle made of steel lowered harden ability is offered. This approach consisting in formation of intense – hardened condition on all surface of a detail.
Directory of Open Access Journals (Sweden)
E. Dologlou
2012-08-01
Full Text Available The application of new data in the power law relation between the stress drop of the earthquake and the lead time of the precursory seismic electric signal led to an exponent which falls in the range of the values of critical exponents for fracture and it is in excellent agreement with a previous one found by (Dologlou, 2012. In addition, this exponent is very close to the one reported by Varotsos and Alexopoulos (1984a, which interconnects the amplitude of the precursory seismic electric signals (SES and the magnitude of the impending earthquake. Hence, the hypothesis that underlying dynamic processes evolving to criticality prevail in the pre-focal area when the SES is emitted is significantly supported.
Energy Technology Data Exchange (ETDEWEB)
Chen, Han; Li, Fuguo, E-mail: fuguolx@nwpu.edu.cn; Li, Jinghui; Ma, Xinkai; Li, Jiang; Wan, Qiong
2016-08-01
The hardening and softening phenomena during torsion deformation are studied based on the Taylor dislocation model for pure titanium. The hardening and softening phenomena are observed through the hardness analysis during micro-indentation test and micro-hardness test. Besides, the variations of indentation size also verify the existence of hardening and softening phenomena during torsion. The variations of geometric necessary dislocations (GNDs) and statistic store dislocations (SSDs) state that the positions of high dislocation density and low dislocation density correspond to the positions of hardening and softening. The results from the microstructure, grain boundaries evolution and twins analysis indicate the twins play an important role in appearance of hardening and softening phenomena. The appearance of hardening and softening phenomena are attributed to the combination of different slip systems and twinning systems combining with the Schmid Factor (SF) analysis and the transmission electron microscope (TEM). The appearance of hardening and softening phenomena can be explained by the Taylor dislocation theory based on TEM analysis. - Highlights: • The phenomena can be characterized by Taylor dislocation model. • The variation of GNDs leads to the phenomena. • The phenomena are proved by micro-hardness, indentation hardness. • The {10-12} twin and {11-24} twin play an important role in the phenomena.
HARDENING OF CRANE RAILS BY PLASMA DISCRETE-TIME SURFACE TREATMENT
Directory of Open Access Journals (Sweden)
S. S. Samotugin
2017-01-01
Full Text Available Crane wheels and rails are subjected to intensive wear in the process of operation. Therefore, improvement of these components’ performance can be considered a task of high importance. A promising direction in this regard is surface treatment by highly concentrated energy flows such as laser beams or plasma jets. This thesis suggests that the use of gradient plasma surface treatment can improve the performance of crane rails. A research was conducted, according to which hardened zones were deposited on crane rails under different treatment modes. Microhardness was measured both at the surface and in depth using custom-made microsections. The article includes the results of study of plasma surface hardening effects on wear resistance of crane rails. Change of plasma surface treatment parameters (current, plasma torch movement speed, argon gas flow rate allows for desired steel hardness and structure, while the choice of optimal location for hardened zones makes it possible to significantly improve wear resistance and crack resistance. As a result of plasma surface hardening, the fine-grained martensite structure is obtained with mainly lamellar morphology and higher hardness rate compared toinduction hardening or overlaying. Wear test of carbon steels revealed that plasma surfacing reduces abrasive wear rate compared to the irinitial state by 2 to 3 times. Enough sharp boundary between hardened and non-hardened portions has a positive effect on the performance of parts under dynamic loads, contributing to the inhibition of cracks during the transition from solid to a soft metal. For carbon and low alloy rail steels, the properties achieved by plasma surface hardening can effectively replace induction hardening or overlaying.The mode range for plasma surface treatment that allow sobtaining a surface layer with certain operating properties has been determined.
Analysis of single event transient pulse-width in 65 nm commercial radiation-hardened logic cell
Li, Haisong; Wu, Longsheng; Yang, Bo; Jiang, Yihu
2017-08-01
With the critical charge reduced to generate a single event effect (SEE) and high working frequency for a nanometer integrated circuit, the single event effect (SET) becomes increasingly serious for high performance SOC and DSP chips. To analyze the radiation-hardened method of SET for the nanometer integrated circuit, the n+ guard ring and p+ guard ring have been adopted in the layout for a 65 nm commercial radiation-hardened standard cell library. The weakest driving capacity inverter cell was used to evaluate the single event transient (SET) pulse-width distribution. We employed a dual-lane measurement circuit to get more accurate SET’s pulse-width. Six kinds of ions, which provide LETs of 12.5, 22.5, 32.5, 42, 63, and 79.5 {MeV}\\cdot {{cm}}2/{mg}, respectively, have been utilized to irradiate the SET test circuit in the Beijing Tandem Accelerator Nuclear Physics National Laboratory. The testing results reveal that the pulse-width of most SETs is shorter than 400 ps in the range of LETeff from 12.5 {MeV}\\cdot {{cm}}2/{mg} to 79.5 {MeV}\\cdot {{cm}}2/{mg} and the pulse-width presents saturation tendency when the effective linear energy transfer (LETeff) value is larger than 40 {MeV}\\cdot {{cm}}2/{mg}. The test results also show that the hardened commercial standard cell’s pulse-width concentrates on 33 to 264 ps, which decreases by 40% compared to the pulse-width of the 65 nm commercial unhardened standard cell.
Structural characterisation of oxygen diffusion hardened alpha-tantalum PVD-coatings on titanium.
Hertl, C; Koll, L; Schmitz, T; Werner, E; Gbureck, U
2014-08-01
Titanium substrates were coated with tantalum layers of 5 μm thickness using physical vapour deposition (PVD). The tantalum layers showed a (110)-preferred orientation. The coated samples were hardened by oxygen diffusion. Using X-ray diffraction the crystallographic structure of the tantalum coatings was characterised, comparing untreated and diffusion hardened specimen conditions. Oxygen depth profiles were determined by glow discharge spectrometry. The hardening effect of the heat treatment was examined by Vickers microhardness testing. The increase of surface hardness caused by oxygen diffusion was at least 50%. Copyright © 2014 Elsevier B.V. All rights reserved.
Evolution of radiation defect and radiation hardening in heat treated SA508 Gr3 steel
Energy Technology Data Exchange (ETDEWEB)
Jin, Hyung-Ha; Kwon, Junhyun [Nuclear Materials Division, Korea Atomic Energy Research Institute, 989-111 Daeduck-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Shin, Chansun, E-mail: c.shin@mju.ac.kr [Department of Materials Science and Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Youngin-shi, Gyeonggi-do 449-728 (Korea, Republic of)
2014-01-15
The formation of radiation defects and corresponding radiation hardening in heat-treated SA508 Gr3 steel after Fe ion irradiation were investigated by means of transmission electron microscopy and a nano-indentation technique. As the residual dislocation density is increased in the matrix, the formation of radiation defects is considerably weakened. Comparison between the characteristics of the radiation defect and an evaluation of radiation hardening indicates that a large dislocation loop contributes little to the radiation hardening in the heat-treated SA508 Gr3 steel.
Evolution of radiation defect and radiation hardening in heat treated SA508 Gr3 steel
Jin, Hyung-Ha; Kwon, Junhyun; Shin, Chansun
2014-01-01
The formation of radiation defects and corresponding radiation hardening in heat-treated SA508 Gr3 steel after Fe ion irradiation were investigated by means of transmission electron microscopy and a nano-indentation technique. As the residual dislocation density is increased in the matrix, the formation of radiation defects is considerably weakened. Comparison between the characteristics of the radiation defect and an evaluation of radiation hardening indicates that a large dislocation loop contributes little to the radiation hardening in the heat-treated SA508 Gr3 steel.
Rajendran, K; de Ruiter, N J A; Chernoglazov, A I; Panta, R K; Butler, A P H; Butler, P H; Bell, S T; Anderson, N G; Woodfield, T B F; Tredinnick, S J; Healy, J L; Bateman, C J; Aamir, R; Doesburg, R M N; Renaud, P F; Gieseg, S P; Smithies, D J; Mohr, J L; Mandalika, V B H; Opie, A M T; Cook, N J; Ronaldson, J P; Nik, S J; Atharifard, A; Clyne, M; Bones, P J; Bartneck, C; Grasset, R; Schleich, N; Billinghurst, M
2014-01-01
This paper discusses methods for reducing beam hardening effects using spectral data for biomaterial applications. A small-animal spectral scanner operating in the diagnostic energy range was used. We investigate the use of photon-processing features of the Medipix3RX ASIC in reducing beam hardening and associated artefacts. A fully operational charge summing mode was used during the imaging routine. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D reconstruction software and volume visualisation using a custom volume rendering software. Narrow high energy acquisition using the photon-processing detector revealed substantial reduction in beam hardening effects and metal artefacts.
Model and numerical analysis of mechanical phenomena of tools steel hardening
Directory of Open Access Journals (Sweden)
A. Bokota
2010-01-01
Full Text Available This paper the model hardening of tool steel takes into considerations of mechanical phenomena is presented. Fields stresses and strains are obtained from solutions by FEM equilibrium equations in rate form. The stresses generated during hardening were assumed to result from thermal load, structural deformation, and plastic deformation and transformation plasticity. Thermophysical values in the constitutive relations are depended upon both the temperature and the phase composition. Condition Huber-Misses with the isotropic strengthening for the creation of plastic strains is used. However model Leblond to determined transformations plasticity applied. The analysis of stresses associated of the elements hardening made of tool steel was done.
DEVELOPMENT AND RESEARCH OF ULTRASONIC OSCILLATORY SYSTEM FOR HARDENING OF SPRING PLATE BILLETS
Directory of Open Access Journals (Sweden)
V. A. Tomilo
2015-01-01
Full Text Available Various schemes of ultrasonic oscillatory system are developed: with a «force nonsensitive» support, with a «force sensitive» support, with the deforming steel balls in bulk. Results of the ultrasonic treatment showed that hardening of a surface of the samples took place when the vibration amplitude of a radiator exceeds a certain level. The level of hardening increases with increase in amplitude of fluctuations of a radiator. Higher level of hardening is registered when the surface is treated by steel balls.
Developments in Radiation-Hardened Electronics Applicable to the Vision for Space Exploration
Keys, Andrew S.; Frazier, Donald O.; Patrick , Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.
2007-01-01
The Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the anticipated requirements of NASA's Constellation program. Methods of protecting and hardening electronics against the encountered space environment are discussed. Critical stages of a spaceflight mission that are vulnerable to radiation-induced interruptions or failures are identified. Solutions to mitigating the risk of radiation events are proposed through the infusion of RHESE technology products and deliverables into the Constellation program's spacecraft designs.
Non Radiation Hardened Microprocessors in Spaced Based Remote Sensing Systems
Decoursey, Robert J.; Estes, Robert F.; Melton, Ryan
2006-01-01
The CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) mission is a comprehensive suite of active and passive sensors including a 20Hz 230mj Nd:YAG lidar, a visible wavelength Earth-looking camera and an imaging infrared radiometer. CALIPSO flies in formation with the Earth Observing System Post-Meridian (EOS PM) train, provides continuous, near-simultaneous measurements and is a planned 3 year mission. CALIPSO was launched into a 98 degree sun synchronous Earth orbit in April of 2006 to study clouds and aerosols and acquires over 5 gigabytes of data every 24 hours. The ground track of one CALIPSO orbit as well as high and low intensity South Atlantic Anomaly outlines is shown. CALIPSO passes through the SAA several times each day. Spaced based remote sensing systems that include multiple instruments and/or instruments such as lidar generate large volumes of data and require robust real-time hardware and software mechanisms and high throughput processors. Due to onboard storage restrictions and telemetry downlink limitations these systems must pre-process and reduce the data before sending it to the ground. This onboard processing and realtime requirement load may mean that newer more powerful processors are needed even though acceptable radiation-hardened versions have not yet been released. CALIPSO's single board computer payload controller processor is actually a set of four (4) voting non-radiation hardened COTS Power PC 603r's built on a single width VME card by General Dynamics Advanced Information Systems (GDAIS). Significant radiation concerns for CALIPSO and other Low Earth Orbit (LEO) satellites include the South Atlantic Anomaly (SAA), the north and south poles and strong solar events. Over much of South America and extending into the South Atlantic Ocean the Van Allen radiation belts dip to just 200-800km and spacecraft entering this area are subjected to high energy protons and experience higher than normal Single Event Upset
HARDENING OF THE ELECTRODESIEGED IRON CHEMICAL HEAT TREATMENT
Directory of Open Access Journals (Sweden)
V. I. Serebrovskii
2015-01-01
Full Text Available Summary. Currently in the repair and manufacture at the stage of recovery of steel parts, widely used special coatings formed by electrolytic effects on ferrous ions. This technique offers high performance, ease of implementation, low cost of technological equipment and materials used, as well as easy automation of the process. However, this method has several disadvantages: low fatigue strength of reconditioned parts, insufficiently strong grip of the iron coating to the substrate, particularly in alloy steels, insufficient wear resistance. For the purpose of increasing durability and wear resistance of parts, restored through electrochemical action, it is proposed to use chemical-heat treatment, consisting in the application of carbonitriding. Investigated the efficacy of different modes of carbonitriding in the highly carburizing paste-and their influence on the structure and properties of iron plating. It is established that the nitrocarburizing both low and high temperatures repeatedly (6-7.5 times increases the microhardness of the coatings. The highest hardness is obtained by low-temperature carbonitriding with direct quenching in water. Conducting the carbonitriding process at low temperatures (650 °C, significantly increases the hardness of the iron coatings, increasing the limit of its fluidity, a and also greatly increases its endurance limit. Nitrocarburized fatigue strength of samples with iron precipitation on the surface, as shown by our studies, not only higher strength of the same samples without carbonitriding (more than 2 times, but higher than the fatigue strength of the base metal without coatings. Raising the temperature of the carbonitriding did not increase the hardness of electrolytic iron. Developed a rational technology of hardening of steel parts, re-chain iron fortification. Selected optimum conditions for carbonitriding hardening restored iron fortification, with the purpose of increasing durability of machine
Influence of finite-time Lyapunov exponents on winter precipitation over the Iberian Peninsula
Garaboa-Paz, Daniel; Lorenzo, Nieves; Pérez-Muñuzuri, Vicente
2017-05-01
Seasonal forecasts have improved during the last decades, mostly due to an increase in understanding of the coupled ocean-atmosphere dynamics, and the development of models able to predict the atmosphere variability. Correlations between different teleconnection patterns and severe weather in different parts of the world are constantly evolving and changing. This paper evaluates the connection between winter precipitation over the Iberian Peninsula and the large-scale tropospheric mixing over the eastern Atlantic Ocean. Finite-time Lyapunov exponents (FTLEs) have been calculated from 1979 to 2008 to evaluate this mixing. Our study suggests that significant negative correlations exist between summer FTLE anomalies and winter precipitation over Portugal and Spain. To understand the mechanisms behind this correlation, summer anomalies of the FTLE have also been correlated with other climatic variables such as the sea surface temperature (SST), the sea level pressure (SLP) or the geopotential. The East Atlantic (EA) teleconnection index correlates with the summer FTLE anomalies, confirming their role as a seasonal predictor for winter precipitation over the Iberian Peninsula.
Spike solutions in Gierer#x2013;Meinhardt model with a time dependent anomaly exponent
Nec, Yana
2018-01-01
Experimental evidence of complex dispersion regimes in natural systems, where the growth of the mean square displacement in time cannot be characterised by a single power, has been accruing for the past two decades. In such processes the exponent γ(t) in ⟨r2⟩ ∼ tγ(t) at times might be approximated by a piecewise constant function, or it can be a continuous function. Variable order differential equations are an emerging mathematical tool with a strong potential to model these systems. However, variable order differential equations are not tractable by the classic differential equations theory. This contribution illustrates how a classic method can be adapted to gain insight into a system of this type. Herein a variable order Gierer-Meinhardt model is posed, a generic reaction- diffusion system of a chemical origin. With a fixed order this system possesses a solution in the form of a constellation of arbitrarily situated localised pulses, when the components' diffusivity ratio is asymptotically small. The pattern was shown to exist subject to multiple step-like transitions between normal diffusion and sub-diffusion, as well as between distinct sub-diffusive regimes. The analytical approximation obtained permits qualitative analysis of the impact thereof. Numerical solution for typical cross-over scenarios revealed such features as earlier equilibration and non-monotonic excursions before attainment of equilibrium. The method is general and allows for an approximate numerical solution with any reasonably behaved γ(t).
A unified econophysics explanation for the power-law exponents of stock market activity
Gabaix, Xavier; Gopikrishnan, Parameswaran; Plerou, Vasiliki; Stanley, Eugene
2007-08-01
We survey a theory (first sketched in Nature in 2003, then fleshed out in the Quarterly Journal of Economics in 2006) of the economic underpinnings of the fat-tailed distributions of a number of financial variables, such as returns and trading volume. Our theory posits that they have a common origin in the strategic trading behavior of very large financial institutions in a relatively illiquid market. We show how the fat-tailed distribution of fund sizes can indeed generate extreme returns and volumes, even in the absence of fundamental news. Moreover, we are able to replicate the individually different empirical values of the power-law exponents for each distribution: 3 for returns, 3/2 for volumes, 1 for the assets under management of large investors. Large investors moderate their trades to reduce their price impact; coupled with a concave price impact function, this leads to volumes being more fat-tailed than returns but less fat-tailed than fund sizes. The trades of large institutions also offer a unified explanation for apparently disconnected empirical regularities that are otherwise a challenge for economic theory.
The Tail Exponent for Stock Returns in Bursa Malaysia for 2003-2008
Rusli, N. H.; Gopir, G.; Usang, M. D.
2010-07-01
A developed discipline of econophysics that has been introduced is exhibiting the application of mathematical tools that are usually applied to the physical models for the study of financial models. In this study, an analysis of the time series behavior of several blue chip and penny stock companies in Main Market of Bursa Malaysia has been performed. Generally, the basic quantity being used is the relative price changes or is called the stock price returns, contains daily-sampled data from the beginning of 2003 until the end of 2008, containing 1555 trading days recorded. The aim of this paper is to investigate the tail exponent in tails of the distribution for blue chip stocks and penny stocks financial returns in six years period. By using a standard regression method, it is found that the distribution performed double scaling on the log-log plot of the cumulative probability of the normalized returns. Thus we calculate α for a small scale return as well as large scale return. Based on the result obtained, it is found that the power-law behavior for the probability density functions of the stock price absolute returns P(z)˜z-α with values lying inside and outside the Lévy stable regime with values α>2. All the results were discussed in detail.
Designing Hyperchaotic Cat Maps With Any Desired Number of Positive Lyapunov Exponents.
Hua, Zhongyun; Yi, Shuang; Zhou, Yicong; Li, Chengqing; Wu, Yue
2017-01-04
Generating chaotic maps with expected dynamics of users is a challenging topic. Utilizing the inherent relation between the Lyapunov exponents (LEs) of the Cat map and its associated Cat matrix, this paper proposes a simple but efficient method to construct an n-dimensional (n-D) hyperchaotic Cat map (HCM) with any desired number of positive LEs. The method first generates two basic n-D Cat matrices iteratively and then constructs the final n-D Cat matrix by performing similarity transformation on one basic n-D Cat matrix by the other. Given any number of positive LEs, it can generate an n-D HCM with desired hyperchaotic complexity. Two illustrative examples of n-D HCMs were constructed to show the effectiveness of the proposed method, and to verify the inherent relation between the LEs and Cat matrix. Theoretical analysis proves that the parameter space of the generated HCM is very large. Performance evaluations show that, compared with existing methods, the proposed method can construct n-D HCMs with lower computation complexity and their outputs demonstrate strong randomness and complex ergodicity.
Landau-Ginzburg Limit of Black Hole's Quantum Portrait: Self Similarity and Critical Exponent
Dvali, Gia
2012-01-01
Recently we have suggested that the microscopic quantum description of a black hole is an overpacked self-sustained Bose-condensate of N weakly-interacting soft gravitons, which obeys the rules of 't Hooft's large-N physics. In this note we derive an effective Landau-Ginzburg Lagrangian for the condensate and show that it becomes an exact description in a semi-classical limit that serves as the black hole analog of 't Hooft's planar limit. The role of a weakly-coupled Landau-Ginzburg order parameter is played by N. This description consistently reproduces the known properties of black holes in semi-classical limit. Hawking radiation, as the quantum depletion of the condensate, is described by the slow-roll of the field N. In the semiclassical limit, where black holes of arbitrarily small size are allowed, the equation of depletion is self similar leading to a scaling law for the black hole size with critical exponent 1/3.
Generalized Hurst exponent estimates differentiate EEG signals of healthy and epileptic patients
Lahmiri, Salim
2018-01-01
The aim of our current study is to check whether multifractal patterns of the electroencephalographic (EEG) signals of normal and epileptic patients are statistically similar or different. In this regard, the generalized Hurst exponent (GHE) method is used for robust estimation of the multifractals in each type of EEG signals, and three powerful statistical tests are performed to check existence of differences between estimated GHEs from healthy control subjects and epileptic patients. The obtained results show that multifractals exist in both types of EEG signals. Particularly, it was found that the degree of fractal is more pronounced in short variations of normal EEG signals than in short variations of EEG signals with seizure free intervals. In contrary, it is more pronounced in long variations of EEG signals with seizure free intervals than in normal EEG signals. Importantly, both parametric and nonparametric statistical tests show strong evidence that estimated GHEs of normal EEG signals are statistically and significantly different from those with seizure free intervals. Therefore, GHEs can be efficiently used to distinguish between healthy and patients suffering from epilepsy.
Energy Technology Data Exchange (ETDEWEB)
Schlick, Conor P., E-mail: conorschlick2015@u.northwestern.edu [Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208 (United States); Umbanhowar, Paul B. [Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Ottino, Julio M. [Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208 (United States); The Northwestern Institute on Complex Systems (NICO), Northwestern University, Evanston, Illinois 60208 (United States); Lueptow, Richard M., E-mail: r-lueptow@northwestern.edu [Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208 (United States); The Northwestern Institute on Complex Systems (NICO), Northwestern University, Evanston, Illinois 60208 (United States)
2014-03-15
We investigate chaotic advection and diffusion in autocatalytic reactions for time-periodic sine flow computationally using a mapping method with operator splitting. We specifically consider three different autocatalytic reaction schemes: a single autocatalytic reaction, competitive autocatalytic reactions, which can provide insight into problems of chiral symmetry breaking and homochirality, and competitive autocatalytic reactions with recycling. In competitive autocatalytic reactions, species B and C both undergo an autocatalytic reaction with species A such that A+B→2B and A+C→2C. Small amounts of initially spatially localized B and C and a large amount of spatially homogeneous A are advected by the velocity field, diffuse, and react until A is completely consumed and only B and C remain. We find that local finite-time Lyapunov exponents (FTLEs) can accurately predict the final average concentrations of B and C after the reaction completes. The species that starts in the region with the larger FTLE has, with high probability, the larger average concentration at the end of the reaction. If B and C start in regions with similar FTLEs, their average concentrations at the end of the reaction will also be similar. When a recycling reaction is added, the system evolves towards a single species state, with the FTLE often being useful in predicting which species fills the entire domain and which is depleted. The FTLE approach is also demonstrated for competitive autocatalytic reactions in journal bearing flow, an experimentally realizable flow that generates chaotic dynamics.
Presence of nonlinearity in intracranial EEG recordings: detected by Lyapunov exponents
Liu, Chang-Chia; Shiau, Deng-Shan; Chaovalitwongse, W. Art; Pardalos, Panos M.; Sackellares, J. C.
2007-11-01
In this communication, we performed nonlinearity analysis in the EEG signals recorded from patients with temporal lobe epilepsy (TLE). The largest Lyapunov exponent (Lmax) and phase randomization surrogate data technique were employed to form the statistical test. EEG recordings were acquired invasively from three patients in six brain regions (left and right temporal depth, sub-temporal and orbitofrontal) with 28-32 depth electrodes placed in depth and subdural of the brain. All three patients in this study have unilateral epileptic focus region on the right hippocampus(RH). Nonlinearity was detected by comparing the Lmax profiles of the EEG recordings to its surrogates. The nonlinearity was seen in all different states of the patient with the highest found in post-ictal state. Further our results for all patients exhibited higher degree of differences, quantified by paired t-test, in Lmax values between original and its surrogate from EEG signals recorded from epileptic focus regions. The results of this study demonstrated the Lmax is capable to capture spatio-temporal dynamics that may not be able to detect by linear measurements in the intracranial EEG recordings.
Detection on Structural Sudden Damage Using Continuous Wavelet Transform and Lipschitz Exponent
Directory of Open Access Journals (Sweden)
Bo Chen
2015-01-01
Full Text Available The degradation of civil engineering structures may lead to a sudden stiffness reduction in a structure and such a sudden damage will cause a discontinuity in the dynamic responses. The detection on structural sudden damage has been actively carried out in this study. The signal singularity of the acceleration responses with sudden stiffness reduction is characterized by the coefficients of continuous wavelet transform with fine scales. A detection approach based on the CWT is proposed in terms of the decomposed detail coefficients of continuous wavelet transform to detect the damage time instant and location. The Lipschitz exponent is mathematically used to estimate the local properties of certain function and is applied to reflect the damage severity. Numerical simulation using a five-story shear building under different types of excitation is carried out to assess the validity of the proposed detection approach for the building at different damage levels. The sensitivity of the damage index to the intensity and frequency range of measurement noise is also investigated. The effects of both measurement noise intensity and frequency range on the damage detection are numerically investigated.
Rapid cold hardening of Thrips palmi (Thysanoptera: Thripidae).
Park, Youngjin; Kim, Kwangho; Kim, Yonggyun
2014-08-01
Cold tolerance of the palm thrips, Thrips palmi Karny, was investigated to predict its survival in field during winter. Supercooling points of T. palmi were varied among the developmental stages and ranged from -26.4 to -18.4°C. However, the cold injuries occurred above supercooling points in terms of higher mortality. The exposure to subzero temperatures (-5° to -15°C) resulted in significant mortalities to all developmental stages of T. palmi. A preexposure to a low temperature (4°C) for 7 h significantly increased the cold tolerance of all stages of T. palmi with respect to survival at -10°C and supercooling capacity. The rapid cold hardening (RCH) was dependent on the duration of the preexposure period at 4°C in adult stage. Polyol and sugar analysis using an high-performance liquid chromatography analysis showed that 4°C preexposure caused accumulation of glycerol, trehalose, mannitol, and mannose in the adults. The increase in trehalose levels was more significant than the others. This study suggests that all stages of T. palmi are able to become cold-hardy by RCH, in which several polyols and sugars may play crucial roles as cryoprotectants.
THE HEAT TREATMENT ANALYSIS OF E110 CASE HARDENING STEEL
Directory of Open Access Journals (Sweden)
MAJID TOLOUEI-RAD
2016-03-01
Full Text Available This paper investigates mechanical and microstructural behaviour of E110 case hardening steel when subjected to different heat treatment processes including quenching, normalizing and tempering. After heat treatment samples were subjected to mechanical and metallographic analysis and the properties obtained from applying different processes were analysed. The heat treatment process had certain effects on the resultant properties and microstructures obtained for E110 steel which are described in details. Quenching produced a martensitic microstructure characterized by significant increase in material’s hardness and a significant decreased in its impact energy. Annealed specimens produced a coarse pearlitic microstructure with minimal variation in hardness and impact energy. For normalized samples, fine pearlitic microstructure was identified with a moderate increase in hardness and significant reduction in impact energy. Tempering had a significant effect on quenched specimens, with a substantial rise in material ductility and reduction of hardness with increasing tempering temperature. Furthermore, Results provide additional substantiation of temper embrittlement theory for low-carbon alloys, and indicate potential occurrence of temper embrittlement for fine pearlitic microstructures.
Stress corrosion cracking evaluation of martensitic precipitation hardening stainless steels
Humphries, T. S.; Nelson, E. E.
1980-01-01
The resistance of the martensitic precipitation hardening stainless steels PH13-8Mo, 15-5PH, and 17-4PH to stress corrosion cracking was investigated. Round tensile and c-ring type specimens taken from several heats of the three alloys were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, to salt spray, and to a seacoast environment. The results indicate that 15-5PH is highly resistant to stress corrosion cracking in conditions H1000 and H1050 and is moderately resistant in condition H900. The stress corrosion cracking resistance of PH13-8Mo and 17-4PH stainless steels in conditions H1000 and H1050 was sensitive to mill heats and ranged from low to high among the several heats included in the tests. Based on a comparison with data from seacoast environmental tests, it is apparent that alternate immersion in 3.5 percent salt water is not a suitable medium for accelerated stress corrosion testing of these pH stainless steels.
Hardening of eucalyptus seedlings via salicylic acid application
Directory of Open Access Journals (Sweden)
Eduardo Henrique Lima Mazzuchelli
2014-09-01
Full Text Available The agricultural and forest productivity suffer restrictions imposed by water stress, high temperature and high solar radiation. This study aimed to evaluate the capacity of stress attenuation and growth promotion of salicylic acid (SA application in eucalyptus (E. urophylla x E. grandis hybrid seedlings under water stress. A completely randomized design, in a 3x4 factorial scheme (three water treatments: constant irrigation with daily replacement of 40% (CI40% or 100% (CI100% of evapotranspirated water, and temporary irrigation suspension with replacement of only 40% of evapotranspirated water (S40%; and four SA concentrations: 0 mg L-1, 100 mg L-1, 200 mg L-1 and 300 mg L-1, was used. Plant photosynthetic parameters and biometric features were evaluated. The stomatal limitation was higher in plants under S40% irrigation, however, the SA application reverted this result, allowing the maintenance of the photosynthetic potential. There was interaction between irrigation regimes and SA doses for number of leaves, leaf area/number of leaves ratio and shoot and root dry mass. It was concluded that the application of 200 mg L -1 of SA positively affected the growth of eucalyptus seedlings under water stress, being considered an auxiliary management technique to their hardening process.
Isothermal Age-hardening Behaviour in a Multi-purpose Dental Casting Gold Alloy
National Research Council Canada - National Science Library
KIM, Hyung-ll; AHN, Ho-Kyung; LEE, Hee-Kyung; HISATSUNE, Kunihiro; SEOL, Hyo-Joung; TAKUMA, Yasuko
1999-01-01
The isothermal age-hardening behaviour of a multi-purpose dental casting gold alloy was investigated by means of hardness testing, X-ray diffraction study, scanning electron microscopic observations...
An Innovative Method for the Dehydration Hardening of Modified Inorganic Binders
National Research Council Canada - National Science Library
I. Izdebska-Szanda; J. Kamińska; M. Angrecki; A. Palma; W. Madej
2016-01-01
The results of research on the possibility of using a gaseous medium (hot air) as a hardening agent for inorganic binders were discussed, and tests on the reclamation of waste moulding sands were carried...
Innovative Microwave Hardening of Water-Glass Containing Sandmixes in Technical-Economic Approach
National Research Council Canada - National Science Library
A. Małachowska; M. Stachowicz; K. Granat
2012-01-01
.... Therefore, numerous researches aimed at eliminating the disadvantages of water-glass binders are directed, among others, to modifying the structure of hydrated sodium silicate or to applying new hardening techniques...
Innovative microwave hardening of water-glass containing sandmixes in technical-economic approach
National Research Council Canada - National Science Library
A. Małachowska; M. Stachowicz; K. Granat
2012-01-01
.... Therefore, numerous researches aimed at eliminating disadvantages of water-glass binder are directed, among others, to modifying structure of hydrated sodium silicate or to applying new hardening techniques...
The Effects of Stress State on the Strain Hardening Behaviors of TWIP Steel
Liu, F.; Dan, W. J.; Zhang, W. G.
2017-05-01
Twinning-Induced Plasticity (TWIP) steels have received great attention due to their excellent mechanical properties as a result of austenite twinning during straining. In this paper, the effects of stress state on the strain hardening behaviors of Fe-20Mn-1.2C TWIP steel were studied. A twinning model considering stress state was presented based on the shear-band framework, and a strain hardening model was proposed by taking dislocation mixture evolution into account. The models were verified by the experimental results of uniaxial tension, simple shear and rolling processes. The strain hardening behaviors of TWIP steel under different stress states were predicted. The results show that the stress state can improve the austenite twining and benefit the strain hardening of TWIP steel.
Radiation Hardened Nanobridge based Non-volatile Memory for Space Applications Project
National Aeronautics and Space Administration — This NASA Phase I SBIR program would develop and demonstrate radiation hardened nanobridge based non-volatile memory (NVM) for space applications. Specifically, we...
Numerical predicting of the structure and stresses state in hardened element made of tool steel
Directory of Open Access Journals (Sweden)
A. Bokota
2008-03-01
Full Text Available The paper presents numerical model of thcrmal phcnomcna, phasc transformation and mcchanical phcnomcna associated with hardeningof carbon tool steel. Model for evaluation or fractions OF phases and their kinetics bascd on continuous heating diagram (CHT andcontinuous cooling diagram (CCT. The stresses generated during hardening were assumed to rcsult from ~hermal load. stntcturaI plasticdeformations and transformation plasricity. Thc hardened material was assumed to be elastic-plastic, and in ordcr to mark plastic strains the non-isothermal plastic law of flow with the isotropic hardening and condition plasticity of Huber-Misses were used. TherrnophysicaI values of mechanical phenomena dependent on bo~hth e phase composition and temperature. In the numerical example thc simulated estimation of the phasc Fraction and strcss distributions in the hardened axisimmetrical elemcnt was performed.
INSTALLATION FOR LARGE SIZE STAMP HARDENING TRANINIG BY WATER-AIR MIXTURE
Directory of Open Access Journals (Sweden)
L. A. Glazkov
2009-01-01
Full Text Available The BNTU has developed a technological process for large-size stamp hardening by means of a water-air mixture. The basic requirements imposed on an hardening installation using a water-air mixture are the following: provision of smooth cooling of a part in order to achieve the required hardness and structure; possibility of machining parts of various sizes; change of modes for machining parts of various grades of steel according to any hardness rate.The peculiar features of the given installation are: a presence of microprocessor control of water-air mixture supply, possibility of simultaneous machining of a stamp set (2 parts and position change of parts to be hardened in the process of thermal treatment.Installation for large-sized stamp hardening has been manufactured and introduced at theMinskplant of special tools and machining attachments.
Radiation-Hardened, Substrate-Removed, Metamorphic InGaAs Detector Arrays Project
National Aeronautics and Space Administration — High-performance radiation-hardened metamorphic InGaAs imaging arrays sensitive from the ultraviolet (UV) through the short-wavelength infrared (SWIR) will be...
A 45 nm Low Cost, Radiation Hardened, Platform Based Structured ASIC Project
National Aeronautics and Space Administration — The proposed 45 nm radiation hardened platform based structured ASIC architecture offers the performance and density expected of a custom ASIC with the low...
Bimis, A; Karalekas, D; Bouropoulos, N; Mouzakis, D; Zaoutsos, S
2016-07-01
This study initially deals with the investigation of the induced strains during hardening stage of a self-setting calcium phosphate bone cement using fiber-Bragg grating (FBG) optical sensors. A complementary Scanning Electron Microscopy (SEM) investigation was also conducted at different time intervals of the hardening period and its findings were related to the FBG recordings. From the obtained results, it is demonstrated that the FBG response is affected by the microstructural changes taking place when the bone cement is immersed into the hardening liquid media. Subsequently, the FBG sensor was used to monitor the absorption process and hygroscopic response of the hardened and dried biocement when exposed to a liquid/humid environment. From the FBG-based calculated hygric strains as a function of moisture concentration, the coefficient of moisture expansion (CME) of the examined bone cement was obtained, exhibiting two distinct linear regions. Copyright © 2016 Elsevier Ltd. All rights reserved.
The Use of Fuzzy Systems for Forecasting the Hardenability of Steel
Directory of Open Access Journals (Sweden)
Sitek W.
2016-06-01
Full Text Available The goal of the research carried out was to develop the fuzzy systems, allowing the determination of the Jominy hardenability curve based on the chemical composition of structural steels for quenching and tempering. Fuzzy system was created to calculate hardness of the steel, based on the alloying elements concentrations, and to forecast the hardenability curves. This was done based on information from the PN-EN 10083-3: 2008. Examples of hardenability curves calculated for exemplar steels were presented. Results of the research confirmed that fuzzy systems are a useful tool in evaluation the effect of alloying elements on the properties of materials compared to conventional methods. It has been demonstrated the practical usefulness of the developed models which allows forecasting the steels’ Jominy hardenability curve.
National Aeronautics and Space Administration — This STTR project aims to develop a process-hardened, simple and low cost multi-analyte sensor for detecting components of rocket engine plumes. The sensor will be...
Induction hardening of tool steel for heavily loaded aircraft engine components
Directory of Open Access Journals (Sweden)
Rokicki P.
2017-03-01
Full Text Available Induction hardening is an innovative process allowing modification of the materials surface with more effective, cheaper and more reproducible way to compare with conventional hardening methods used in the aerospace industry. Unfortunately, high requirements and strict regulation concerning this branch of the industry force deep research allowing to obtain results that would be used for numerical modelling of the process. Only by this way one is able to start the industrial application of the process. The main scope of presented paper are results concerning investigation of microstructure evolution of tool steel after single-frequency induction hardening process. The specimens that aim in representing final industrial products (as heavily loaded gears, were heat- -treated with induction method and subjected to metallographic preparation, after which complex microstructure investigation was performed. The results obtained within the research will be a basis for numerical modelling of the process of induction hardening with potential to be introduced for the aviation industrial components.
PERSPECTIVE TECHNOLOGIES OF THERMAL HARDENING OF LARGE-SIZE ARTICLES OF TWO-PHASE TITANIUM ALLOYS
Directory of Open Access Journals (Sweden)
V. N. Fedulov
2005-01-01
Full Text Available The article is dedicated to the development and industrial assimilation of the fundamentally new methods of thermal strengthening of large articles out of hardenable titanic alloys.
Influence of the Hardener Proportion on Mechanical Properties of Adhesive Bonds Used in Agriculture
Directory of Open Access Journals (Sweden)
Valášek P.
2015-01-01
Full Text Available Joining materials by adhesive bonding is used across all industrial branches. The occurrence of adhesive bonds in machine constructions is still more frequent because of the development of adhesives which are able to meet various requirements of designers. This trend is observable also in agriculture - in the construction of agricultural machines. There even exists a cooperation between the companies developing the adhesives and the agricultural machines producers. The production process of machines and equipment must consider a required production tact. Adhesives and the process of their hardening have to meet these requirements. In the sphere of agriculture, epoxy resins hardening based either on hardeners or heating are used. Mechanical properties of two-component epoxy resins depending on variable amount of the hardener starting crosslinking of these reactoplastics are described.
Pushpalatha, K.; Sangaranarayanan, M. V.
1997-07-01
The evaluation of critical exponent β for two-dimensional condensation of organic adsorbates at the mercury-aqueous solution interface is carried out using spin- {1}/{2} generalized Ising model formalism. The estimated value is in agreement with Onsager's value of 0.125 pertaining to two-dimensional Ising model with nearest neighbour interaction energies.
Magnasco, Valerio
2008-01-01
Orbital exponent optimization in the elementary ab-initio VB calculation of the ground states of H[subscript 2][superscript +], H[subscript 2], He[subscript 2][superscript +], He[subscript 2] gives a fair description of the exchange-overlap component of the interatomic interaction that is important in the bond region. Correct bond lengths and…
Plastino, A.; Rocca, M. C.
2017-06-01
Appealing to the 1902 Gibbs formalism for classical statistical mechanics (SM)—the first SM axiomatic theory ever that successfully explained equilibrium thermodynamics—we show that already at the classical level there is a strong correlation between Renyi's exponent α and the number of particles for very simple systems. No reference to heat baths is needed for such a purpose.
Luis, Edwin E. Mozo; de Assis, Thiago A.; Ferreira, Silvio C.
2017-04-01
We present an optimal detrended fluctuation analysis (DFA) and apply it to evaluate the local roughness exponent in nonequilibrium surface growth models with mounded morphology. Our method consists in analyzing the height fluctuations computing the shortest distance of each point of the profile to a detrending curve that fits the surface within the investigated interval. We compare the optimal DFA (ODFA) with both the standard DFA and nondetrended analysis. We validate the ODFA method considering a one-dimensional model in the Kardar-Parisi-Zhang universality class starting from a mounded initial condition. We applied the methods to the Clarke-Vvedensky (CV) model in 2 +1 dimensions with thermally activated surface diffusion and absence of step barriers. It is expected that this model belongs to the nonlinear molecular beam epitaxy (nMBE) universality class. However, an explicit observation of the roughness exponent in agreement with the nMBE class was still missing. The effective roughness exponent obtained with ODFA agrees with the value expected for the nMBE class, whereas using the other methods it does not agree. We also characterize the transient anomalous scaling of the CV model and obtained that the corresponding exponent is in agreement with the value reported for other nMBE models with weaker corrections to the scaling.
Experimental drying shrinkage of hardened cement pastes as a function of relative humidity
DEFF Research Database (Denmark)
Hansen, Kurt Kielsgaard; Baroghel, V.B.
1996-01-01
The results of an experimental study concerning drying shrinkage measured as a function of relative humidity on thin specimens of mature hardened cement pastes are presented. The results obtained at two laboratories are compared.......The results of an experimental study concerning drying shrinkage measured as a function of relative humidity on thin specimens of mature hardened cement pastes are presented. The results obtained at two laboratories are compared....
Simulation of Thermally Induced Stress during Hardening of Large Concrete Cubes
DEFF Research Database (Denmark)
Clausen, Johan; Sørensen, Eigil V.
This report summarizes findings reported in ‖”Numerisk simulering af temperatur –og spændingstilstanden i hærdnende betonkonstruktioner”‖ (Numerical simulation of temperature and stress state in hardening concrete structures) by Rikke Poulsen and Morten Christiansen, concerning simulation of ther...... of thermally induced stress during hardening of large concrete cubes produced in connection with a harbor construction project in La Coruña, Spain....
Successful and long-lasting treatment of solar urticaria with ultraviolet A rush hardening therapy.
Masuoka, E; Fukunaga, A; Kishigami, K; Jimbo, H; Nishioka, M; Uchimura, Y; Taguchi, K; Ohgou, N; Nishigori, C
2012-07-01
Solar urticaria (SU) is a photodermatosis that is thought to be caused through the effects of mast cell mediators released because of an altered chromophore, possibly a photoallergen recognized by IgE. Phototherapy for SU to induce a tolerant state appears to be most effective, but is often time consuming and provides only short-lived remission. Ultraviolet (UV) A rush hardening has been successful and less time consuming in serum factor-negative patients with SU. However, the mechanism of action and long-lasting effects of UVA rush hardening therapy remain unclear. We aimed to evaluate whether UVA rush hardening exhibits long-lasting therapeutic effects in serum factor-positive patients with SU and to examine the action mechanism of tolerance. Two serum factor-positive patients with SU were exposed to multiple UVA irradiations at 1-h intervals per day for 2 or 3 days. Intradermal injection of their in vitro-irradiated autologous serum or compound 48/80 and a prick test for histamine were performed before and after UVA rush hardening. The two serum factor-positive patients with SU benefited greatly from UVA rush hardening, as documented by a marked increase in minimal wealing dose, and remained symptom free without using sunscreen in their daily life. Intradermal injection of in vitro-irradiated autologous serum induced wealing before hardening, but not in tolerized skin after hardening. The responses to compound 48/80 and histamine were unaltered. UVA rush hardening is an effective and long-lasting treatment even in serum factor-positive patients with SU. The mechanism of tolerance may involve continued blockade of photoallergen binding to IgE on mast cells, rather than depletion of mast cell mediators or histamine tachyphylaxis. © 2012 The Authors. BJD © 2012 British Association of Dermatologists.
Energy Technology Data Exchange (ETDEWEB)
Patra, Anirban [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez Saez, Enrique [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-31
This report describes the implementation of a crystal plasticity framework (VPSC) for irradiation hardening and plastic deformation in the finite element code, MOOSE. Constitutive models for irradiation hardening and the crystal plasticity framework are described in a previous report [1]. Here we describe these models briefly and then describe an algorithm for interfacing VPSC with finite elements. Example applications of tensile deformation of a dog bone specimen and a 3D pre-irradiated bar specimen performed using MOOSE are demonstrated.
Award for Distinguished Scientific Early Career Contributions to Psychology: Kathryn Paige Harden.
2017-12-01
The APA Awards for Distinguished Scientific Early Career Contributions to Psychology recognize psychologists who have demonstrated excellence early in their careers and have held a doctoral degree for no more than 9 years. One of the 2017 award winners is Kathryn Paige Harden, for demonstrating "how to integrate genetic knowledge with the classical clinical and developmental insights into human behavior." Harden's award citation, biography, and a selected bibliography are presented here. (PsycINFO Database Record (c) 2017 APA, all rights reserved).
An Evaluation of Processes for the Blackening of Precipitation-Hardened Stainless Steels
1979-06-01
IDENTIFIERS: PRECIPITATION HARDENING, CORROSION TESTS, ZINC PHOSPHATE , SODIUM DICHROMATE, LPN-PR0N-A1-9-23016-01-M1-M1 <<P FOR NEXT PAGE>> OR...ocfc number) 1. Black Coatings Stainless Steel 3. Precipitation Hardening h. Black Chromium Plating 5. Zinc Phosphate Coating 6. Iron...black chromium plating, zinc phosphating , molten sodium dichromate, and alkaline-oxidizing treatments. Activated and passivated specimens were used
A Review of NASA's Radiation-Hardened Electronics for Space Environments Project
Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael A.; Cressler, John D.
2008-01-01
NASA's Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the requirements of NASA's Constellation program. Over the past year, multiple advancements have been made within each of the RHESE technology development tasks that will facilitate the success of the Constellation program elements. This paper provides a brief review of these advancements, discusses their application to Constellation projects, and addresses the plans for the coming year.
3MA NDT Investigation for Process Monitoring and Quality Control in Press Hardened Steel
Gabi, Yasmine; Wolter, Bernd; Kern, Rolf; Conrad, Christian; Gerbershagen, Andreas
2016-01-01
International audience; The press-hardening or hot stamping is an innovative production of car reinforcement structure. These parts served for the improvement of crash performance and passenger safety, therefore there was a hard necessity to control the crash material characteristics, such as hardness, strength and the other parameters related to microstructure (coating, diffusion layer). In this case of press hardened steel (PHS), the materials are adjusted during the forming process not in ...
Radiation Hardening and Heavy-ion to Laser Correlation in SiGe Devices and Circuits
2017-03-01
Radiation Hardening and Heavy-ion to Laser Correlation in SiGe Devices and Circuits Zachary E. Fleetwood and John D. Cressler School of...platforms intended for radiation - intense applications and spaceflight hardware considerations. A number of new radio frequency (RF) studies have...extended the knowledge base of applying radiation -hardening-by- design (RHBD) to SiGe Heterojunction Bipolar Transistor (HBT) circuits. Other research
Energy Technology Data Exchange (ETDEWEB)
Cordovilla, Francisco [Centro Láser UPM, Universidad Politécnica de Madrid, Campus Sur U.P.M. Carretera de Valencia, km. 7,300, 28031 Madrid (Spain); García-Beltrán, Ángel, E-mail: agarcia@etsii.upm.es [Centro Láser UPM, Universidad Politécnica de Madrid, Campus Sur U.P.M. Carretera de Valencia, km. 7,300, 28031 Madrid (Spain); Dominguez, Jesús; Sancho, Paula [IKERGUNE A.I.E., San Antolin, 3, 20870 Elgoibar, Guipúzcoa (Spain); Ocaña, José L. [Centro Láser UPM, Universidad Politécnica de Madrid, Campus Sur U.P.M. Carretera de Valencia, km. 7,300, 28031 Madrid (Spain)
2015-12-01
Graphical abstract: - Highlights: • A laser surface hardening model, with oxidation and fast austenization, is proposed. • The oxide layer has to be calculated considering a non-equilibrium chemical reaction. • An innovative formula is demonstrated to relate the oxide thickness with absorption. • Austenite fraction has been obtained using Avrami law from realistic thermal cycles. • Temperatures and metallurgical phases show excellent agreement with experiments. - Abstract: Laser surface hardening is a technology that enables important advantages to be obtained in comparison with conventional techniques in terms of accuracy of the heat affected zone and productivity. Nevertheless, the development of realistic and flexible models has to be fulfilled in order to control the effects of every set of process conditions. Despite many different models having been developed, very few of them deal with the increment of absorption related with the instantaneous value of the layer of oxide growth during the process in a non-protective atmosphere. This work analyzes the problem of oxide formation at the external surface using kinetic relations, whose parameters have been related with the process variables, considering non-equilibrium conditions. Then, the oxide thickness was associated with a value of absorption through an innovative formula that considers the path of the laser radiation in the interface oxide-base material. The thermal calculations obtained by this method have allowed phase changes to be predicted using Avrami law. Both thermal and metallurgical results for different process conditions have been compared with experimental data showing an excellent agreement.
Directory of Open Access Journals (Sweden)
M. Stachowicz
2010-04-01
Full Text Available In this work, we undertook an attempt at determination of the possibility of efficiency increase of application of hydrated sodium silicate hardened with selected methods. The results of the influence of dielectric drying method (in the process of innovative microwave heating as well as classical drying on tensile strength of molding sands have been presented. The effectiveness of both hardening methods has been evaluated through comparison of the obtained tensile strength values to the amount of water glass used for preparation of molding sand. Five kinds of hydrated sodium silicate have been used in these studies. It has been found that microwave heating process positively influences tensile strength of molding sands prepared with addition of all the available on the market binding agents (including those, most frequently used in foundry kinds of 145, 149 and 150. It has been demonstrated that the innovative microwave heating, while compared to convection drying process, guarantees better strength characteristics, significantly exceeding them, especially in case of very small contents of binding agent of 1.5% and 2.5%. Decrease of drying processes effectiveness, in case of convection method as well as dielectric one, has been observed with increase of binding agent content in molding sand to over 3.5%.
Irradiation-induced hardening and softening of CLAM steel under Fe ion irradiation
Li, Qingshan; Shen, Yinzhong; Huang, Xi; Xu, Zhiqiang; Zhu, Jun
2017-11-01
The irradiation-induced hardening and softening of CLAM steel irradiated with 3.5 MeV Fe13+ ions at temperatures of 300 °C and 550 °C were investigated by nanoindentation tests in combination with microstructures. Irradiation- induced hardening occurred in the steel irradiated at 300 °C to doses of 0.46 dpa, 0.94 dpa, and 2.79 dpa. The hardening occurred at 300 °C is mainly attributed to the formation of irradiation-produced dislocation loops and a network of tangled dislocations in the irradiated steel samples. Significant hardening was found in the steel irradiated at 550 °C to 0.38 dpa. On the contrary, irradiation-induced softening occurred in the steel irradiated at 550 °C to both 0.76 dpa and 2.75 dpa. Irradiation-produced dislocation loops are not dominant effect on the irradiation hardening of the steel samples irradiated at 550 °C. The hardening and softening of the irradiated steel were explained in terms of the irradiation-produced defects and recovery process occurred during the irradiation.
Veerababu, R.; Balamuralikrishnan, R.; Muraleedharan, K.; Srinivas, M.
2015-06-01
Clusters, containing between 10 and 1000 atoms, have been investigated in a martensitic secondary hardening ultra-high-strength steel austenitized at 1173 K (900 °C) for 1 hour and tempered at either 768 K or 783 K (495 °C or 510 °C) for 4 or 8 hours using 3D atom probe. The presence of clusters was unambiguously established by comparing the observed spatial distribution of the different alloying elements against the corresponding distribution expected for a random solid solution. Maximum separation envelope method has been used for delineating the clusters from the surrounding "matrix." Statistical analysis was used extensively for size and composition analyses of the clusters. The clusters were found to constitute a significant fraction accounting for between 1.14 and 2.53 vol pct of the microstructure. On the average, the clusters in the 783 K (510 °C) tempered sample were coarser by ~65 pct, with an average diameter of 2.26 nm, relative to the other samples. In all samples, about 85 to 90 pct of the clusters have size less than 2 nm. The percentage frequency histograms for carbon content of the clusters in 768 K and 783 K (495 °C and 510 °C) tempered samples revealed that the distribution shifts toward higher carbon content when the tempering temperature is higher. It is likely that the presence of these clusters exerts considerable influence on the strength and fracture toughness of the steel.
Hurst Exponent Analysis of Resting-State fMRI Signal Complexity across the Adult Lifespan
Directory of Open Access Journals (Sweden)
Jianxin Dong
2018-02-01
Full Text Available Exploring functional information among various brain regions across time enables understanding of healthy aging process and holds great promise for age-related brain disease diagnosis. This paper proposed a method to explore fractal complexity of the resting-state functional magnetic resonance imaging (rs-fMRI signal in the human brain across the adult lifespan using Hurst exponent (HE. We took advantage of the examined rs-fMRI data from 116 adults 19 to 85 years of age (44.3 ± 19.4 years, 49 females from NKI/Rockland sample. Region-wise and voxel-wise analyses were performed to investigate the effects of age, gender, and their interaction on complexity. In region-wise analysis, we found that the healthy aging is accompanied by a loss of complexity in frontal and parietal lobe and increased complexity in insula, limbic, and temporal lobe. Meanwhile, differences in HE between genders were found to be significant in parietal lobe (p = 0.04, corrected. However, there was no interaction between gender and age. In voxel-wise analysis, the significant complexity decrease with aging was found in frontal and parietal lobe, and complexity increase was found in insula, limbic lobe, occipital lobe, and temporal lobe with aging. Meanwhile, differences in HE between genders were found to be significant in frontal, parietal, and limbic lobe. Furthermore, we found age and sex interaction in right parahippocampal gyrus (p = 0.04, corrected. Our findings reveal HE variations of the rs-fMRI signal across the human adult lifespan and show that HE may serve as a new parameter to assess healthy aging process.
Paul, A.; Reuther, F.; Neumann, S.; Albert, A.; Landgrebe, D.
2017-09-01
One field in the work of the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz is industry applied research in Hot Metal Gas Forming, combined with press hardening in one process step. In this paper the results of investigations on new press hardening steels from SSAB AB (Docol®1800 Bor and Docol®2000 Bor) are presented. Hot tensile tests recorded by the project partner (University of West Bohemia, Faculty of Mechanical Engineering) were used to create a material model for thermo-mechanical forming simulations. For this purpose the provided raw data were converted into flow curve approximations of the real stress-real strain-curves for both materials and afterwards integrated in a LS-DYNA simulation model of Hot Metal Gas Forming with all relevant boundary conditions and sub-stages. Preliminary experimental tests were carried out using a tool at room temperature to permit evaluation of the forming behaviour of Docol 1800 Bor and Docol 2000 Bor tubes as well as validation of the simulation model. Using this demonstrator geometry (outer diameter 57 mm, tube length 300 mm, wall thickness 1.5 mm), the intention was to perform a series of tests with different furnace temperatures (from 870 °C to 1035 °C), maximum internal pressures (up to 67 MPa) and pressure build-up rates (up to 40 MPa/s) to evaluate the formability of Docol 1800 Bor and Docol 2000 Bor. Selected demonstrator parts produced in that way were subsequently analysed by wall thickness and hardness measurements. The tests were carried out using the completely modernized Dunkes/AP&T HS3-1500 hydroforming press at the Fraunhofer IWU. In summary, creating a consistent simulation model with all relevant sub-stages was successfully established in LS-DYNA. The computation results show a high correlation with the experimental data regarding the thinning behaviour. The Hot Metal Gas Forming of the demonstrator geometry was successfully established as well. Different hardness values
Directory of Open Access Journals (Sweden)
Lincoln Cardoso Brandão
2011-01-01
Full Text Available This work evaluates the hole quality on AISI H13 hardened steel using high-speed drilling. Specimens were machined with new and worn out drills with 8.6 mm diameter and (TiAlN coating. Two levels of cutting speed and three levels of cooling/lubrication systems (flooded, minimum lubrication quantity, and dry were used. The hole quality is evaluated on surface roughness (Ra parameter, diameter error, circularity, and cylindricity error. A statistical analysis of the results shows that the cooling/lubrication system significantly affects the hole quality for all measured variables. This analysis indicates that dry machining produces the worst results. Higher cutting speeds not only prove beneficial to diameter error and circularity errors, but also show no significant difference on surface roughness and cylindricity errors. The effects of the interaction between the cooling/lubrication systems, tool wear, and cutting speed indicate that only cylindricity error is influenced. Thus, the conclusion is that the best hole quality is produced with a higher cutting speed using flooded or minimum lubrication quantity independent of drill wear.
Role of vacancies in work hardening and fatigue of TiAl alloys
Czech Academy of Sciences Publication Activity Database
Appel, F.; Herrmann, D.; Fischer, F. D.; Svoboda, Jiří; Kozeschnik, E.
2013-01-01
Roč. 42, MAR (2013), s. 83-100 ISSN 0749-6419 R&D Projects: GA ČR GAP108/10/1781 Institutional research plan: CEZ:AV0Z20410507 Institutional support: RVO:68081723 Keywords : Dislocations * Cyclic loading * Metallic material * Electron microscopy * Analytic functions Subject RIV: BJ - Thermodynamics Impact factor: 5.971, year: 2013
Work-Hardening Induced Tensile Ductility of Bulk Metallic Glasses via High-Pressure Torsion
Soo-Hyun Joo; Dong-Hai Pi; Albertus Deny Heri Setyawan; Hidemi Kato; Milos Janecek; Yong Chan Kim; Sunghak Lee; Hyoung Seop Kim
2015-01-01
The mechanical properties of engineering materials are key for ensuring safety and reliability. However, the plastic deformation of BMGs is confined to narrow regions in shear bands, which usually result in limited ductilities and catastrophic failures at low homologous temperatures. The quasi-brittle failure and lack of tensile ductility undercut the potential applications of BMGs. In this report, we present clear tensile ductility in a Zr-based BMG via a high-pressure torsion (HPT) process....
Energy Technology Data Exchange (ETDEWEB)
Yekehtaz, M.; Benfer, S.; Fuerbeth, W. [DECHEMA-Forschungsinstitut, Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main (Germany); Klesen, C.; Bleck, W. [Institut fuer Eisenhuettenkunde der RWTH Aachen, Intzestrasse 1, D-52072 Aachen (Germany)
2012-10-15
The need for lighter constructional materials in automotive industries has increased the use of high-strength steel alloys. To enhance passenger's safety press hardening may be applied to steel parts. However, as the steel parts are heated up to 950 C during this process they have to be protected by some kind of coating against the intense oxide formation usually taking place. As the coating systems used so far all have certain disadvantages in this work the ability of nano-particulate thin coatings obtained by the sol-gel process to improve the oxidation resistance of 22MnB5 steel is investigated. The coatings obtained from three sols containing lithium aluminum silicate and potassium aluminum silicate showed the best performance against oxidation. The structural properties of the coating materials were characterized using different methods like XRD and differential thermal analysis. Comparison of the oxidation rate constants proved the ability of the coatings to protect against oxidation at temperatures up to 800 C. Press-hardening experiments in combination with investigations on the thermal shock resistance of the coated samples also showed the ability of the coatings to stay intact during press hardening with only slight spalling of the coatings in the bending areas. The absence of any secondary intermetallic phases and layer residues during laser beam welding experiments on coated samples proves the suitability of the nano-particulate coatings for further industrial processing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)