WorldWideScience

Sample records for microstructural heterogeneities analyse

  1. Swimming fluctuations of micro-organisms due to heterogeneous microstructure

    Science.gov (United States)

    Jabbarzadeh, Mehdi; Hyon, YunKyong; Fu, Henry C.

    2014-10-01

    Swimming microorganisms in biological complex fluids may be greatly influenced by heterogeneous media and microstructure with length scales comparable to the organisms. A fundamental effect of swimming in a heterogeneous rather than homogeneous medium is that variations in local environments lead to swimming velocity fluctuations. Here we examine long-range hydrodynamic contributions to these fluctuations using a Najafi-Golestanian swimmer near spherical and filamentous obstacles. We find that forces on microstructures determine changes in swimming speed. For macroscopically isotropic networks, we also show how the variance of the fluctuations in swimming speeds are related to density and orientational correlations in the medium.

  2. Stochastic Analysis and Design of Heterogeneous Microstructural Materials System

    Science.gov (United States)

    Xu, Hongyi

    Advanced materials system refers to new materials that are comprised of multiple traditional constituents but complex microstructure morphologies, which lead to superior properties over the conventional materials. To accelerate the development of new advanced materials system, the objective of this dissertation is to develop a computational design framework and the associated techniques for design automation of microstructure materials systems, with an emphasis on addressing the uncertainties associated with the heterogeneity of microstructural materials. Five key research tasks are identified: design representation, design evaluation, design synthesis, material informatics and uncertainty quantification. Design representation of microstructure includes statistical characterization and stochastic reconstruction. This dissertation develops a new descriptor-based methodology, which characterizes 2D microstructures using descriptors of composition, dispersion and geometry. Statistics of 3D descriptors are predicted based on 2D information to enable 2D-to-3D reconstruction. An efficient sequential reconstruction algorithm is developed to reconstruct statistically equivalent random 3D digital microstructures. In design evaluation, a stochastic decomposition and reassembly strategy is developed to deal with the high computational costs and uncertainties induced by material heterogeneity. The properties of Representative Volume Elements (RVE) are predicted by stochastically reassembling SVE elements with stochastic properties into a coarse representation of the RVE. In design synthesis, a new descriptor-based design framework is developed, which integrates computational methods of microstructure characterization and reconstruction, sensitivity analysis, Design of Experiments (DOE), metamodeling and optimization the enable parametric optimization of the microstructure for achieving the desired material properties. Material informatics is studied to efficiently reduce the

  3. Rationalization of Microstructure Heterogeneity in INCONEL 718 Builds Made by the Direct Laser Additive Manufacturing Process

    Science.gov (United States)

    Tian, Yuan; McAllister, Donald; Colijn, Hendrik; Mills, Michael; Farson, Dave; Nordin, Mark; Babu, Sudarsanam

    2014-09-01

    Simulative builds, typical of the tip-repair procedure, with matching compositions were deposited on an INCONEL 718 substrate using the laser additive manufacturing process. In the as-processed condition, these builds exhibit spatial heterogeneity in microstructure. Electron backscattering diffraction analyses showed highly misoriented grains in the top region of the builds compared to those of the lower region. Hardness maps indicated a 30 pct hardness increase in build regions close to the substrate over those of the top regions. Detailed multiscale characterizations, through scanning electron microscopy, electron backscattered diffraction imaging, high-resolution transmission electron microscopy, and ChemiSTEM, also showed microstructure heterogeneities within the builds in different length scales including interdendritic and interprecipitate regions. These multiscale heterogeneities were correlated to primary solidification, remelting, and solid-state precipitation kinetics of γ″ induced by solute segregation, as well as multiple heating and cooling cycles induced by the laser additive manufacturing process.

  4. Microstructure Analyses of NA-Nanodiamond Particles

    Science.gov (United States)

    2016-08-01

    Microscopy Results and Discussion 1 Scanning Electron Microscope (SEM) Analysis 5 Objective 5 Experimental Procedure 5 Discussion of Results 5...420 electron microscope at 120 KV voltage was used for TEM analyses. Transmission Electronic Microscopy Results and Discussion An electron ...SCANNING ELECTRON MICROSCOPE (SEM) ANALYSIS Objective Examine the morphology and elemental chemistry of detonated nanodiamonds (DND

  5. Dynamic reconstruction of heterogeneous materials and microstructure evolution.

    Science.gov (United States)

    Chen, Shaohua; Li, Hechao; Jiao, Yang

    2015-08-01

    Reconstructing heterogeneous materials from limited structural information has been a topic that attracts extensive research efforts and still poses many challenges. The Yeong-Torquato procedure is one of the most popular reconstruction techniques, in which the material reconstruction problem based on a set of spatial correlation functions is formulated as a constrained energy minimization (optimization) problem and solved using simulated annealing [Yeong and Torquato, Phys. Rev. E 57, 495 (1998)]. The standard two-point correlation function S2 has been widely used in reconstructions, but can also lead to large structural degeneracy for certain nearly percolating systems. To improve reconstruction accuracy and reduce structural degeneracy, one can successively incorporate additional morphological information (e.g., nonconventional or higher-order correlation functions), which amounts to reshaping the energy landscape to create a deep (local) energy minimum. In this paper, we present a dynamic reconstruction procedure that allows one to use a series of auxiliary S2 to achieve the same level of accuracy as those incorporating additional nonconventional correlation functions. In particular, instead of randomly sampling the microstructure space as in the simulated annealing scheme, our procedure utilizes a series of auxiliary microstructures that mimic a physical structural evolution process (e.g., grain growth). This amounts to constructing a series auxiliary energy landscapes that bias the convergence of the reconstruction to a favored (local) energy minimum. Moreover, our dynamic procedure can be naturally applied to reconstruct an actual microstructure evolution process. In contrast to commonly used evolution reconstruction approaches that separately generate individual static configurations, our procedure continuously evolves a single microstructure according to a time-dependent correlation function. The utility of our procedure is illustrated by successfully

  6. A microstructure-guided constitutive modeling approach for random heterogeneous materials: Application to structural binders

    Energy Technology Data Exchange (ETDEWEB)

    Das, Sumanta; Maroli, Amit; Singh, Sudhanshu S.; Stannard, Tyler; Xiao, Xianghui; Chawla, Nikhilesh; Neithalath, Narayanan

    2016-06-01

    This paper presents a microstructure-guided modeling approach to predict the effective elastic response of heterogeneous materials, and demonstrates its application toward two highly heterogeneous, uncon- ventional structural binders, i.e., iron carbonate and fly ash geopolymer. Microstructural information from synchrotron X-ray tomography (XRT) and intrinsic elastic properties of component solid phases from statistical nanoindentation are used as the primary inputs. The virtual periodic 3D microstructure reconstructed using XRT, along with periodic boundary conditions is used as a basis for strain- controlled numerical simulation scheme in the linear elastic range to predict the elastic modulus as well as the stresses in the microstructural phases. The elastic modulus of the composite material predicted from the microstructure-based constitutive modeling approach correlates very well with experimental measurements for both the materials considered. This technique efficiently links the microstructure to mechanical properties of interest and helps develop material design guidelines for novel heterogeneous composites

  7. Heterogeneous micro-structure of percolation in sparse networks

    Science.gov (United States)

    Kühn, Reimer; Rogers, Tim

    2017-06-01

    We examine the heterogeneous responses of individual nodes in sparse networks to the random removal of a fraction of edges. Using the message-passing formulation of percolation, we discover considerable variation across the network in the probability of a particular node to remain part of the giant component, and in the expected size of small clusters containing that node. In the vicinity of the percolation threshold, weakly non-linear analysis reveals that node-to-node heterogeneity is captured by the recently introduced notion of non-backtracking centrality. We supplement these results for fixed finite networks by a population dynamics approach to analyse random graph models in the infinite system size limit, also providing closed-form approximations for the large mean degree limit of Erdős-Rényi random graphs. Interpreted in terms of the application of percolation to real-world processes, our results shed light on the heterogeneous exposure of different nodes to cascading failures, epidemic spread, and information flow.

  8. Development of numerical framework to study microstructural effects on shock initiation in heterogeneous energetic materials

    Science.gov (United States)

    Schmidt, Martin; Rai, Nirmal; Udaykumar, H. S.

    2015-06-01

    Heterogeneous energetic materials like plastic bonded explosives (PBX) have very detailed and non-uniform microstructure. The heterogeneity is mainly because of presence of HMX crystals embedded in a polymer binder matrix. Also, manufacturing defects often creates pores and cracks in the material. Shock interaction with these heterogeneities leads to local heated regions known as hot spots. It is widely accepted that these hot spots are predominantly the cause of triggering reaction and eventually ignition in these energetic materials. There are various physical phenomenon through which hot spot can be created such as pore collapse, inter-granular friction in HMX crystals, shock heating of HMX crystals and binder etc. Hence, microstructural heterogeneity can play a vital role for shock initiation in PBX. In the current work, a general framework has been established for performing mesoscale simulations on heterogeneous energetic material. In order to get an accurate representation of the microstructure, image processing algorithms have been employed on XCMT images of PBX microstructure. The image processing framework has been built up with massively parallel Eulerian code, SCIMITAR3D. Shock simulation on PBX microstructures has been performed and the effect of microstructure geometry has been studied for different shock strengths case. The simulation results have been shown to resolve hot spots created due to various heterogeneities present in the microstructure.

  9. A weighted U statistic for association analyses considering genetic heterogeneity.

    Science.gov (United States)

    Wei, Changshuai; Elston, Robert C; Lu, Qing

    2016-07-20

    Converging evidence suggests that common complex diseases with the same or similar clinical manifestations could have different underlying genetic etiologies. While current research interests have shifted toward uncovering rare variants and structural variations predisposing to human diseases, the impact of heterogeneity in genetic studies of complex diseases has been largely overlooked. Most of the existing statistical methods assume the disease under investigation has a homogeneous genetic effect and could, therefore, have low power if the disease undergoes heterogeneous pathophysiological and etiological processes. In this paper, we propose a heterogeneity-weighted U (HWU) method for association analyses considering genetic heterogeneity. HWU can be applied to various types of phenotypes (e.g., binary and continuous) and is computationally efficient for high-dimensional genetic data. Through simulations, we showed the advantage of HWU when the underlying genetic etiology of a disease was heterogeneous, as well as the robustness of HWU against different model assumptions (e.g., phenotype distributions). Using HWU, we conducted a genome-wide analysis of nicotine dependence from the Study of Addiction: Genetics and Environments dataset. The genome-wide analysis of nearly one million genetic markers took 7h, identifying heterogeneous effects of two new genes (i.e., CYP3A5 and IKBKB) on nicotine dependence. Copyright © 2016 John Wiley & Sons, Ltd.

  10. Influence of deformation conditions on the development of heterogeneous recrystallization microstructures in experimentally deformed Carrara marble

    NARCIS (Netherlands)

    Valcke, S.L.A.; de Bresser, J.H.P.; Pennock, G.M.; Drury, M.R.

    2015-01-01

    Recrystallized grains are potentially useful as indicators of palaeostress in naturally deformed rocks, providing that well-calibrated relationships (palaeopiezometers) exist between the recrystallized grain size and stress. Rocks can exhibit microstructures that are heterogeneous, that is, containi

  11. Micro-mechanical analysis and modelling of the behavior and brittle fracture of a french 16MND5 steel: role of microstructural heterogeneities; Analyse et modelisation micromecanique du comportement et de la rupture fragile de l'acier 16MND5: prise en compte des heterogeneites microstructurales

    Energy Technology Data Exchange (ETDEWEB)

    Mathieu, J.Ph

    2006-10-15

    Reactor Pressure Vessel is the second containment barrier between nuclear fuel and the environment. Electricite de France's reactors are made with french 16MND5 low-alloyed steel (equ. ASTM A508 Cl.3). Various experimental techniques (scanning electron microscopy, X-ray diffraction...) are set up in order to characterize mechanical heterogeneities inside material microstructure during tensile testing at different low temperatures [-150 C;-60 C]. Heterogeneities can be seen as the effect of both 'polycrystalline' and 'composite' microstructural features. Interphase (until 150 MPa in average between ferritic and bainitic macroscopic stress state) and intra-phase (until 100 MPa in average between ferritic orientations) stress variations are highlighted. Modelling involves micro-mechanical description of plastic glide, mean fields models and realistic three-dimensional aggregates, all put together inside a multi-scale approach. Calibration is done on macroscopic stress-strain curves at different low temperatures, and modelling reproduces experimental stress heterogeneities. This modelling allows to apply a local micro-mechanical fracture criterion for crystallographic cleavage. Deterministic computations of time to fracture for different carbides random selection provide a way to express probability of fracture for the elementary volume. Results are in good agreement with hypothesis made by local approach to fracture. Hence, the main difference is that no dependence to loading nor microstructure features is supposed for probability of fracture on the representative volume: this dependence is naturally introduced by modelling. (author)

  12. A hierarchical framework for the multiscale modeling of microstructure evolution in heterogeneous materials.

    Energy Technology Data Exchange (ETDEWEB)

    Luscher, Darby J.

    2010-04-01

    All materials are heterogeneous at various scales of observation. The influence of material heterogeneity on nonuniform response and microstructure evolution can have profound impact on continuum thermomechanical response at macroscopic “engineering” scales. In many cases, it is necessary to treat this behavior as a multiscale process thus integrating the physical understanding of material behavior at various physical (length and time) scales in order to more accurately predict the thermomechanical response of materials as their microstructure evolves. The intent of the dissertation is to provide a formal framework for multiscale hierarchical homogenization to be used in developing constitutive models.

  13. FOREWORD: Heterogenous nucleation and microstructure formation—a scale- and system-bridging approach Heterogenous nucleation and microstructure formation—a scale- and system-bridging approach

    Science.gov (United States)

    Emmerich, H.

    2009-11-01

    Scope and aim of this volume. Nucleation and initial microstructure formation play an important role in almost all aspects of materials science [1-5]. The relevance of the prediction and control of nucleation and the subsequent microstructure formation is fully accepted across many areas of modern surface and materials science and technology. One reason is that a large range of material properties, from mechanical ones such as ductility and hardness to electrical and magnetic ones such as electric conductivity and magnetic hardness, depend largely on the specific crystalline structure that forms in nucleation and the subsequent initial microstructure growth. A very demonstrative example for the latter is the so called bamboo structure of an integrated circuit, for which resistance against electromigration [6] , a parallel alignment of grain boundaries vertical to the direction of electricity, is most favorable. Despite the large relevance of predicting and controlling nucleation and the subsequent microstructure formation, and despite significant progress in the experimental analysis of the later stages of crystal growth in line with new theoretical computer simulation concepts [7], details about the initial stages of solidification are still far from being satisfactorily understood. This is in particular true when the nucleation event occurs as heterogenous nucleation. The Priority Program SPP 1296 'Heterogenous Nucleation and Microstructure Formation—a Scale- and System-Bridging Approach' [8] sponsored by the German Research Foundation, DFG, intends to contribute to this open issue via a six year research program that enables approximately twenty research groups in Germany to work interdisciplinarily together following this goal. Moreover, it enables the participants to embed themselves in the international community which focuses on this issue via internationally open joint workshops, conferences and summer schools. An outline of such activities can be found

  14. Analysis of through-thickness heterogeneities of microstructure and texture in nickel after accumulative roll bonding

    DEFF Research Database (Denmark)

    Zhang, Yubin; Mishin, Oleg; Godfrey, A.

    2014-01-01

    The through-thickness heterogeneities of the microstructure and texture have been investigated in pure nickel processed by six cycles of accumulative roll bonding (ARB) with lubrication applied during each rolling pass. Strong rolling textures are found in the intermediate and center layers...... with the summed fraction of the rolling texture components. The observed microstructural and textural variations are discussed and compared with literature data, taking into account the influence of large-draught rolling and lubrication on the distribution of strain imposed during the ARB process....

  15. Accurate stochastic reconstruction of heterogeneous microstructures by limited x-ray tomographic projections.

    Science.gov (United States)

    Li, Hechao; Kaira, Shashank; Mertens, James; Chawla, Nikhilesh; Jiao, Yang

    2016-12-01

    An accurate knowledge of the complex microstructure of a heterogeneous material is crucial for its performance prediction, prognosis and optimization. X-ray tomography has provided a nondestructive means for microstructure characterization in 3D and 4D (i.e. structural evolution over time), in which a material is typically reconstructed from a large number of tomographic projections using filtered-back-projection (FBP) method or algebraic reconstruction techniques (ART). Here, we present in detail a stochastic optimization procedure that enables one to accurately reconstruct material microstructure from a small number of absorption contrast x-ray tomographic projections. This discrete tomography reconstruction procedure is in contrast to the commonly used FBP and ART, which usually requires thousands of projections for accurate microstructure rendition. The utility of our stochastic procedure is first demonstrated by reconstructing a wide class of two-phase heterogeneous materials including sandstone and hard-particle packing from simulated limited-angle projections in both cone-beam and parallel beam projection geometry. It is then applied to reconstruct tailored Sn-sphere-clay-matrix systems from limited-angle cone-beam data obtained via a lab-scale tomography facility at Arizona State University and parallel-beam synchrotron data obtained at Advanced Photon Source, Argonne National Laboratory. In addition, we examine the information content of tomography data by successively incorporating larger number of projections and quantifying the accuracy of the reconstructions. We show that only a small number of projections (e.g. 20-40, depending on the complexity of the microstructure of interest and desired resolution) are necessary for accurate material reconstructions via our stochastic procedure, which indicates its high efficiency in using limited structural information. The ramifications of the stochastic reconstruction procedure in 4D materials science are also

  16. Microstructural heterogeneity directs micromechanics and mechanobiology in native and engineered fibrocartilage

    Science.gov (United States)

    Han, Woojin M.; Heo, Su-Jin; Driscoll, Tristan P.; Delucca, John F.; McLeod, Claire M.; Smith, Lachlan J.; Duncan, Randall L.; Mauck, Robert L.; Elliott, Dawn M.

    2016-04-01

    Treatment strategies to address pathologies of fibrocartilaginous tissue are in part limited by an incomplete understanding of structure-function relationships in these load-bearing tissues. There is therefore a pressing need to develop micro-engineered tissue platforms that can recreate the highly inhomogeneous tissue microstructures that are known to influence mechanotransductive processes in normal and diseased tissue. Here, we report the quantification of proteoglycan-rich microdomains in developing, ageing and diseased fibrocartilaginous tissues, and the impact of these microdomains on endogenous cell responses to physiologic deformation within a native-tissue context. We also developed a method to generate heterogeneous tissue-engineered constructs (hetTECs) with non-fibrous proteoglycan-rich microdomains engineered into the fibrous structure, and show that these hetTECs match the microstructural, micromechanical and mechanobiological benchmarks of native tissue. Our tissue-engineered platform should facilitate the study of the mechanobiology of developing, homeostatic, degenerating and regenerating fibrous tissues.

  17. Analyses of microstructural properties of VA/VeoVA copolymer modified cement pastes

    OpenAIRE

    Carlos Eduardo M. Gomes; Ferreira,Osny P.

    2005-01-01

    Recently, modern techniques have been applied for analysis of the influence of polymers on microstructural properties of Portland cement, such as Thermogravimetric Analyses (TG), Scanning Electronic Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Mercury Intrusion Porosimetry (MIP). In this study, thermogravimetric analyses were used to study the influence of vinyl acetate-versatic vinylester copolymer (VA/VeoVA) in seven pastes of 28-day old Portland cement, in which di...

  18. Analyses of microstructural properties of VA/VeoVA copolymer modified cement pastes

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo M. Gomes

    2005-07-01

    Full Text Available Recently, modern techniques have been applied for analysis of the influence of polymers on microstructural properties of Portland cement, such as Thermogravimetric Analyses (TG, Scanning Electronic Microscopy (SEM, Fourier Transform Infrared Spectroscopy (FT-IR and Mercury Intrusion Porosimetry (MIP. In this study, thermogravimetric analyses were used to study the influence of vinyl acetate-versatic vinylester copolymer (VA/VeoVA in seven pastes of 28-day old Portland cement, in which distinct polymer contents and water/cement ratios were employed. In addition, analyses of FT-IR and MIP on Portland cement pastes modified by the copolymer were employed. The results showed that the addition of polymer interferes significantly in the reduction of Portlandite formation and increases the porosity of the matrices. A possible chemical interaction between the copolymer and hydrated products of Portland cement was also observed.

  19. On stochastic FEM based computational homogenization of magneto-active heterogeneous materials with random microstructure

    Science.gov (United States)

    Pivovarov, Dmytro; Steinmann, Paul

    2016-12-01

    In the current work we apply the stochastic version of the FEM to the homogenization of magneto-elastic heterogeneous materials with random microstructure. The main aim of this study is to capture accurately the discontinuities appearing at matrix-inclusion interfaces. We demonstrate and compare three different techniques proposed in the literature for the purely mechanical problem, i.e. global, local and enriched stochastic basis functions. Moreover, we demonstrate the implementation of the isoparametric concept in the enlarged physical-stochastic product space. The Gauss integration rule in this multidimensional space is discussed. In order to design a realistic stochastic Representative Volume Element we analyze actual scans obtained by electron microscopy and provide numerical studies of the micro particle distribution. The SFEM framework described in our previous work (Pivovarov and Steinmann in Comput Mech 57(1): 123-147, 2016) is extended to the case of the magneto-elastic materials. To this end, the magneto-elastic energy function is used, and the corresponding hyper-tensors of the magneto-elastic problem are introduced. In order to estimate the methods' accuracy we performed a set of simulations for elastic and magneto-elastic problems using three different SFEM modifications. All results are compared with "brute-force" Monte-Carlo simulations used as reference solution.

  20. A stochastic XFEM model for the tensile strength prediction of heterogeneous graphite based on microstructural observations

    Science.gov (United States)

    Bansal, Manik; Singh, I. V.; Mishra, B. K.; Sharma, Kamal; Khan, I. A.

    2017-04-01

    A stochastic XFEM model based on microstructural observations has been developed to evaluate the tensile strength of NBG-18 nuclear graphite. The nuclear graphite consists of pitch matrix, filler particles, pores and micro-cracks. The numerical simulations are performed at two length scales due to large difference in average size of filler particles and pores. Both deterministic and stochastic approaches have been implemented. The study intends to illustrate the variation in tensile strength due to heterogeneities modeled stochastically. The properties of pitch matrix and filler particles are assumed to be known at the constituent level. The material models for both pitch and fillers are assumed to be linear elastic. The stochastic size and spatial distribution of the pores and filler particles has been modeled during the micro and macro analysis respectively. The strength of equivalent porous pitch matrix evaluated at micro level has been distributed stochastically in the elemental domain along with filler particles for macro analysis. The effect of micro-cracks has been incorporated indirectly by considering fracture plane in each filler particle. Tensile strength of nuclear graphite is obtained by performing the simulations at macro-level. Statistical parameters evaluated using numerical tensile strength data agree well with experimentally obtained statistical parameters available in the literature.

  1. Resilin-PEG Hybrid Hydrogels Yield Degradable Elastomeric Scaffolds with Heterogeneous Microstructure.

    Science.gov (United States)

    McGann, Christopher L; Akins, Robert E; Kiick, Kristi L

    2016-01-11

    Hydrogels derived from resilin-like polypeptides (RLPs) have shown outstanding mechanical resilience and cytocompatibility; expanding the versatility of RLP-based materials via conjugation with other polypeptides and polymers would offer great promise in the design of a range of materials. Here, we present an investigation of the biochemical and mechanical properties of hybrid hydrogels composed of a recombinant RLP and a multiarm PEG macromer. These hybrid hydrogels can be rapidly cross-linked through a Michael-type addition reaction between the thiols of cysteine residues on the RLP and vinyl sulfone groups on the multiarm PEG. Oscillatory rheology and tensile testing confirmed the formation of elastomeric hydrogels with mechanical resilience comparable to aortic elastin; hydrogel stiffness was easily modulated through the cross-linking ratio. Macromolecular phase separation of the RLP-PEG hydrogels offers the unique advantage of imparting a heterogeneous microstructure, which can be used to localize cells, through simple mixing and cross-linking. Assessment of degradation of the RLP by matrix metalloproteinases (MMPs) illustrated the specific proteolysis of the polypeptide in both its soluble form and when cross-linked into hydrogels. Finally, the successful encapsulation and viable three-dimensional culture of human mesenchymal stem cells (hMSCs) demonstrated the cytocompatibility of the RLP-PEG gels. Overall, the cytocompatibility, elastomeric mechanical properties, microheterogeneity, and degradability of the RLP-PEG hybrid hydrogels offer a suite of promising properties for the development of cell-instructive, structured tissue engineering scaffolds.

  2. On stochastic FEM based computational homogenization of magneto-active heterogeneous materials with random microstructure

    Science.gov (United States)

    Pivovarov, Dmytro; Steinmann, Paul

    2016-09-01

    In the current work we apply the stochastic version of the FEM to the homogenization of magneto-elastic heterogeneous materials with random microstructure. The main aim of this study is to capture accurately the discontinuities appearing at matrix-inclusion interfaces. We demonstrate and compare three different techniques proposed in the literature for the purely mechanical problem, i.e. global, local and enriched stochastic basis functions. Moreover, we demonstrate the implementation of the isoparametric concept in the enlarged physical-stochastic product space. The Gauss integration rule in this multidimensional space is discussed. In order to design a realistic stochastic Representative Volume Element we analyze actual scans obtained by electron microscopy and provide numerical studies of the micro particle distribution. The SFEM framework described in our previous work (Pivovarov and Steinmann in Comput Mech 57(1): 123-147, 2016) is extended to the case of the magneto-elastic materials. To this end, the magneto-elastic energy function is used, and the corresponding hyper-tensors of the magneto-elastic problem are introduced. In order to estimate the methods' accuracy we performed a set of simulations for elastic and magneto-elastic problems using three different SFEM modifications. All results are compared with "brute-force" Monte-Carlo simulations used as reference solution.

  3. Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process

    Science.gov (United States)

    Asala, G.; Khan, A. K.; Andersson, J.; Ojo, O. A.

    2017-06-01

    A detailed microstructural study of ATI 718Plus superalloy produced by the wire-arc additive manufacturing (WAAM) process was performed through the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), and electron backscatter diffraction (EBSD). Extensive formation of eutectic solidification microconstituents including Laves and MC-type carbide phases, induced by micro-segregation, are observed in the build of the alloy in the as-deposited condition. Notwithstanding the significant segregation of niobium (Nb), which has been reported to promote the formation of the δ-phase in ATI 718Plus, only η-phase particles are observed in the deposit. Excessive precipitation of η-phase particles is found to be linked to Laves phase particles that are partially dissolved in the deposit after post-deposition heat treatment (PDHT). The EBSD analysis shows a high textured build in the directions with only a few misoriented grains at the substrate-deposit boundary and the top of the deposit. Investigation on the hardness of the build of the alloy, in the as-deposited condition, showed a softened zone about 2 mm wide at the deposited metal heat affected zone (DMHAZ), which has not been previously reported and potentially damaging to the mechanical properties. An extensive analysis with the use of both microstructural characterization tools and theoretical calculations shows that the DMHAZ has the lowest volume fraction of strengthening precipitates (γ' and γ″) in terms of their number density, which therefore induces the observed softness. Delayed re-precipitation kinetics and the extent of the precipitation of γ' and γ″ in the DMHAZ which is related to the diffusion of segregated solute elements from the interdendritic regions are attributed to this phenomenon. The microstructural analyses discussed in this work are vital to adequate understanding of properties of ATI 718Plus produced by the additive

  4. Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process

    Science.gov (United States)

    Asala, G.; Khan, A. K.; Andersson, J.; Ojo, O. A.

    2017-09-01

    A detailed microstructural study of ATI 718Plus superalloy produced by the wire-arc additive manufacturing (WAAM) process was performed through the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), and electron backscatter diffraction (EBSD). Extensive formation of eutectic solidification microconstituents including Laves and MC-type carbide phases, induced by micro-segregation, are observed in the build of the alloy in the as-deposited condition. Notwithstanding the significant segregation of niobium (Nb), which has been reported to promote the formation of the δ-phase in ATI 718Plus, only η-phase particles are observed in the deposit. Excessive precipitation of η-phase particles is found to be linked to Laves phase particles that are partially dissolved in the deposit after post-deposition heat treatment (PDHT). The EBSD analysis shows a high textured build in the 〈100〉 directions with only a few misoriented grains at the substrate-deposit boundary and the top of the deposit. Investigation on the hardness of the build of the alloy, in the as-deposited condition, showed a softened zone about 2 mm wide at the deposited metal heat affected zone (DMHAZ), which has not been previously reported and potentially damaging to the mechanical properties. An extensive analysis with the use of both microstructural characterization tools and theoretical calculations shows that the DMHAZ has the lowest volume fraction of strengthening precipitates ( γ' and γ″) in terms of their number density, which therefore induces the observed softness. Delayed re-precipitation kinetics and the extent of the precipitation of γ' and γ″ in the DMHAZ which is related to the diffusion of segregated solute elements from the interdendritic regions are attributed to this phenomenon. The microstructural analyses discussed in this work are vital to adequate understanding of properties of ATI 718Plus produced by the

  5. Thermal Effects on Microstructural Heterogeneity of Inconel 718 Materials Fabricated by Electron Beam Melting

    Energy Technology Data Exchange (ETDEWEB)

    Sames, William J. [Texas A & M Univ., College Station, TX (United States); Unocic, Kinga A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Dehoff, Ryan R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lolla, Tapasvi [The Ohio State Univ., Columbus, OH (United States); Babu, Sudarsanam Suresh [Univ. of Tennessee, Knoxville, TN (United States)

    2014-07-28

    Additive manufacturing (AM) technologies, also known as 3D printing, have demonstrated the potential to fabricate complex geometrical components, but the resulting microstructures and mechanical properties of these materials are not well understood due to unique and complex thermal cycles observed during processing. The electron beam melting (EBM) process is unique because the powder bed temperature can be elevated and maintained at temperatures over 1000 °C for the duration of the process. This results in three specific stages of microstructural phase evolution: (a) rapid cool down from the melting temperature to the process temperature, (b) extended hold at the process temperature, and (c) slow cool down to the room temperature. In this work, the mechanisms for reported microstructural differences in EBM are rationalized for Inconel 718 based on measured thermal cycles, preliminary thermal modeling, and computational thermodynamics models. The relationship between processing parameters, solidification microstructure, interdendritic segregation, and phase precipitation (δ, γ´, and γ´´) are discussed.

  6. Who Let the CAT Out of the Bag? Accurately Dealing with Substitutional Heterogeneity in Phylogenomic Analyses.

    Science.gov (United States)

    Whelan, Nathan V; Halanych, Kenneth M

    2016-09-14

    As phylogenetic datasets have increased in size, site-heterogeneous substitution models such as CAT-F81 and CAT-GTR have been advocated in favor of other models because they purportedly suppress long-branch attraction (LBA). These models are two of the most commonly used models in phylogenomics, and they have been applied to a variety of taxa, ranging from Drosophila to land plants. However, many arguments in favor of CAT models have been based on tenuous assumptions about the true phylogeny, rather than rigorous testing with known trees via simulation. Moreover, CAT models have not been compared to other approaches for handling substitutional heterogeneity such as data partitioning with site-homogeneous substitution models. We simulated amino acid sequence datasets with substitutional heterogeneity on a variety of tree shapes including those susceptible to LBA. Data were analyzed with both CAT models and partitioning to explore model performance; in total over 670,000 CPU hours were used, of which over 97% was spent running analyses with CAT models. In many cases, all models recovered branching patterns that were identical to the known tree. However, CAT-F81 consistently performed worse than other models in inferring the correct branching patterns, and both CAT models often overestimated substitutional heterogeneity. Additionally, reanalysis of two empirical metazoan datasets supports the notion that CAT-F81 tends to recover less accurate trees than data partitioning and CAT-GTR. Given these results, we conclude that partitioning and CAT-GTR perform similarly in recovering accurate branching patterns. However, computation time can be orders of magnitude less for data partitioning, with commonly used implementations of CAT-GTR often failing to reach completion in a reasonable time frame (i.e., for Bayesian analyses to converge). Practices such as removing constant sites and parsimony uninformative characters, or using CAT-F81 when CAT-GTR is deemed too

  7. Quantification of rock heterogeneities by structural geological field studies combined with laboratory analyses

    Science.gov (United States)

    Reyer, Dorothea; Afsar, Filiz; Philipp, Sonja

    2013-04-01

    Heterogeneous rock properties in terms of layering and complex infrastructure of fault zones are typical in sedimentary successions. The knowledge of in-situ mechanical rock properties is crucial for a better understanding of processes such as fracturing and fluid transport in fractured reservoirs. To estimate in situ rock properties at different depths it is important to understand how rocks from outcrops differ from rocks at depth, for example due to alteration and removal of the overburden load. We aim at quantifying these properties by performing structural geological field studies in outcrop analogues combined with laboratory analyses of outcrop samples and drill-cores. The field studies focus on 1) fault zone infrastructure and 2) host rock fracture systems in two different study areas with different lithologies, the North German and the Bristol Channel Basin. We analyse quantitatively the dimension, geometry, persistence and connectivity of fracture systems. The field studies are complemented by systematic sampling to obtain the parameters Young's modulus, compressive and tensile strengths and elastic strain energy (also referred to as destruction work) from which we estimate rock and fracture toughnesses. The results show that in rocks with distinctive layering fractures are often restricted to individual layers, that is, stratabound. The probability of arrest seems to depend on the stiffness contrast between two single layers as well as on the thickness of the softer layer. The results also show that there are clear differences between fault zones in the different lithologies in terms of damage zone thicknesses and fracture system parameters. The results of laboratory analyses show that the mechanical properties vary considerably and for many samples there are clear directional differences. That is, samples taken perpendicular to layering commonly have higher stiffnesses and strengths than those taken parallel to layering. We combine the results of

  8. Wave Propagation and Dynamic Load Transfer due to Explosive Loading in Heterogenous Granular Media with Microstructure

    Science.gov (United States)

    1992-09-30

    in Granular Assemblies with Microstructural Defects", J. of Engineering Mechanics, Vol. 118, No. 1, Jan . 1992, pp. 190-201. 8. Shukla A. and Sadd, M. H...equivalent micropolar continuum has been investigated by Banks and Sokolowski (1968), Bazant and Christensen (1972) and Sun and Yang (1975). The...pp. 17 -2 3 . Bazant , Z. P. and Chr ;tensen, M. (1972) "Analogy Between Micropolar Continuum and Grid Frameworks Under Initial Stress’, Int. J. Solids

  9. Microstructural analyses of amorphic diamond, i-C, and amorphous carbon

    DEFF Research Database (Denmark)

    Collins, C. B.; Davanloo, F.; Jander, D.R.;

    1992-01-01

    Recent experiments have identified the microstructure of amorphic diamond with a model of packed nodules of amorphous diamond expected theoretically. However, this success has left in doubt the relationship of amorphic diamond to other noncrystalline forms of carbon. This work reports...... the comparative examinations of the microstructures of samples of amorphic diamond, i-C, and amorphous carbon. Four distinct morphologies were found that correlated closely with the energy densities used in preparing the different materials. Journal of Applied Physics is copyrighted by The American Institute...

  10. Heterogeneity of the Nugget Microstructure in a Thick 2050 Al Friction-Stirred Weld

    Science.gov (United States)

    Avettand-Fenoel, Marie-Noëlle; Taillard, Roland

    2015-01-01

    The current article deals with 19-mm-thick welds of AA 2050. These joints obtained by friction stir butt welding on half penetration were subsequently strained and artificially aged. The nugget's hardness weakens along the plate thickness from the top surface. This evolution is explained by the modification of the precipitation state, which overcomes the effects of the changes of size and preferred orientation of grains along the nugget's depth. This modification of microstructure arises from the various strains, strain rates, and temperatures encountered in the different areas in the nugget. The postwelding treatment did not manage to suppress either the undermatching of the original nugget compared to the base material or the differences of thermal stabilities at the different depths in the nugget.

  11. Micropolar interface model of thin-layered interconnection components with heterogeneous internal microstructures

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Yan; FAN; Jing-yu

    2009-01-01

    Being a wide variety of thin-layered interconnection components in electronics packaging with relatively small scale and heterogeneous materials, conventional numerical methods may be time consuming and even inefficacious to obtain an accurate prediction for the interface behavior under mechanical and/or thermal loading. Rather than resort to a fully spatial discretization in the vicinity of this interface zone, an interface model was proposed within the framework of micropolar theory by introducing discontinuous approximation. A fracture description was used to represent the microscopic failure progress inside the interface. The micropolar interface model was then numerically implemented with the finite element method. As an application, the interface behavior of a packaging system with anisotropic conductive adhesive(ACA)joint was analyzed, demonstrating its applicability and great efficiency.

  12. Statistics for quantifying heterogeneity in univariate and bivariate meta-analyses of binary data: the case of meta-analyses of diagnostic accuracy.

    Science.gov (United States)

    Zhou, Yan; Dendukuri, Nandini

    2014-07-20

    Heterogeneity in diagnostic meta-analyses is common because of the observational nature of diagnostic studies and the lack of standardization in the positivity criterion (cut-off value) for some tests. So far the unexplained heterogeneity across studies has been quantified by either using the I(2) statistic for a single parameter (i.e. either the sensitivity or the specificity) or visually examining the data in a receiver-operating characteristic space. In this paper, we derive improved I(2) statistics measuring heterogeneity for dichotomous outcomes, with a focus on diagnostic tests. We show that the currently used estimate of the 'typical' within-study variance proposed by Higgins and Thompson is not able to properly account for the variability of the within-study variance across studies for dichotomous variables. Therefore, when the between-study variance is large, the 'typical' within-study variance underestimates the expected within-study variance, and the corresponding I(2) is overestimated. We propose to use the expected value of the within-study variation in the construction of I(2) in cases of univariate and bivariate diagnostic meta-analyses. For bivariate diagnostic meta-analyses, we derive a bivariate version of I(2) that is able to account for the correlation between sensitivity and specificity. We illustrate the performance of these new estimators using simulated data as well as two real data sets.

  13. A combined microstructural and petrophysical study to analyse the mechanical behaviour of shales in the Flysch units, Glarus Alps, Switzerland

    Science.gov (United States)

    Akker, Vénice; Kaufmann, Josef; Berger, Alfons; Herwegh, Marco

    2017-04-01

    Crustal scale deformation is strongly controlled by the rheological behaviour of sheet-silicate-rich rock types. As these rocks have low rock strength, facilitated by the strong crystallographically controlled mechanical anisotropy and interstitial pore fluid in the aggregate, they are able to accommodate considerable amounts of strain. A close relationship is expected between microstructure, porosity and permeability as function of metamorphic conditions and strain gradients. Thereby, fluids set free by compaction, mineral reactions or deformation play an important role. Rising industries in underground storage such as nuclear waste disposal, shale gas exploration or geological carbon sequestration make use of the advantageous properties of such rock types. Therefore, there is a great demand for research on the interaction of these processes. This study uses samples from Flysch-units of the Glarus Alps (Switzerland) collected along a metamorphic gradient (150-400°C) to unravel the link between the mechanical behaviour of these sheet-silicate-rich rocks at geological conditions and their present-day physical parameters. Investigations include two topics: (1) characterization of such rock types in terms of mineralogy, microstructure and petrophysical properties; and (2) possible reconstruction of deformation processes from microstructures. Quantitative information on the porosity, i.e. the pore sizes, distribution and their interconnectivity is crucial for both topics. Porosity is therefore estimated by: (1) image analysis of high resolution SEM images, (2) He-pycnometry, and (3) Hg-porosimetry. In a first step, differences in their present day physical parameters between low and high temperature sampling sites are shown. The variations inside and between the investigated samples is partly due to initial sedimentological heterogeneity and partly to the changes along the metamorphic gradient. This study will demonstrate how the characterized present day porosity

  14. Quantifying the impact of between-study heterogeneity in multivariate meta-analyses

    OpenAIRE

    Jackson, Dan; White, Ian R; Riley, Richard D.

    2012-01-01

    Measures that quantify the impact of heterogeneity in univariate meta-analysis, including the very popular I 2 statistic, are now well established. Multivariate meta-analysis, where studies provide multiple outcomes that are pooled in a single analysis, is also becoming more commonly used. The question of how to quantify heterogeneity in the multivariate setting is therefore raised. It is the univariate R 2 statistic, the ratio of the variance of the estimated treatment effect under the rando...

  15. Essays on Social Network Formation in Heterogeneous Populations: Models, Methods, and Empirical Analyses

    OpenAIRE

    Bojanowski, M.J.

    2012-01-01

    The overarching focus of the essays presented in this book pertains to the characteristics of individual actors (such as the industry or nationality associated with a firm), the extent to which the population of actors is heterogeneous with respect to those characteristics, and the ways in which actor characteristics and population heterogeneity influence the process of social network formation and the choices that actors make in these networks. We investigate theoretical, empirical, and meth...

  16. Association of microstructure and electric heterogeneity in BiFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Makhdoom, A.R. [DMME, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad (Pakistan); Akhtar, M.J., E-mail: javedakhtar6@gmail.com [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Khan, R.T.A. [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Rafiq, M.A.; Hasan, M.M. [DMME, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad (Pakistan); Sher, F. [Department of Chemistry, School of Science and Engineering, LUMS, Lahore (Pakistan); Fitch, A.N. [European Synchrotron Radiation Facility, BP220, 38043 Grenoble Cedex (France)

    2013-12-16

    BiFeO{sub 3} ceramics was synthesized by solid state reaction technique. Synchrotron X-ray diffraction analysis was employed to investigate the phase formation and structure determination. Rietveld refinement of the diffracted data confirmed the rhombohedrally distorted perovskite structure with space group R3c. Localized atomic structure determined from fitted X-ray data showed off centered displacement of Fe{sup 3+} cations with a magnitude of 0.397 Å along c-axis. The FeO{sub 6} octahedron comprised of two types of Fe–O bonds with bond lengths of ∼1.935 Å and ∼2.131 Å. Impedance spectroscopic data collected in wide temperature (300–400 K) and frequency (200 Hz–2 MHz) ranges, demonstrated two relaxation phenomena corresponding to two heterogeneous phases. The best fits to the collected impedance data were achieved by employing an equivalent circuit model R{sub g}(R{sub gb}C{sub gb})(R{sub e}Q{sub e}). Grain boundaries showed only p-type small polaronic hopping conduction process assisted with the oxidation of Fe{sup 3+} to Fe{sup 4+} in measured temperature range of 300–400 K. Grains exhibited p-type small polaronic hopping conduction mechanism up to 375 K; however, above 375 K electronic conduction becomes prominent. Conduction is dominated by short range hopping of the polarons among Fe{sup 3+} and Fe{sup 4+} or through the first ionized oxygen vacancy bridge between Fe{sup 3+} and Fe{sup 2+} cations. - Highlights: • Single phase BiFeO{sub 3} ceramics have been synthesized by solid state reaction method. • Synchrotron XRD revealed a rhombohedrally distorted structure with space group R3c. • Two relaxation phenomena in impedance data demonstrated two heterogeneous phases. • Conduction is dominated by short range hopping of the polarons among Fe{sup 3+} and Fe{sup 4+}.

  17. Essays on Social Network Formation in Heterogeneous Populations: Models, Methods, and Empirical Analyses

    NARCIS (Netherlands)

    Bojanowski, M.J.

    2012-01-01

    The overarching focus of the essays presented in this book pertains to the characteristics of individual actors (such as the industry or nationality associated with a firm), the extent to which the population of actors is heterogeneous with respect to those characteristics, and the ways in which act

  18. Using otolith microstructure to analyse growth of juvenile Baltic cod Gadus morhua

    DEFF Research Database (Denmark)

    Hüssy, Karin; Mosegaard, Henrik; Hinrichsen, H.H.

    2003-01-01

    Pelagic and demersal juvenile Baltic cod Gadus morhua L. were collected on the slope and the top of Rønne bank in the Baltic Sea during 2 cruises in November and December 1998. The growth, age at settling and vertical migration pattern were studied by otolith microstructure analysis....... The relationship between fish and otolith size were found to change at settling, with an increase of fish size in relation to otolith size after settling. This change was more pronounced on the slope compared to the top of the bank. The timing of first settling at the 2 localities did not differ with respect...... to fish age. At both localities, fish that hatched early in the season spent a shorter time in the pelagic stage than late-hatched fish. However, significant differences in growth rate during the pelagic stage were observed, where fish captured on the slope grew faster. On the bank, individuals with fast...

  19. Deciphering heterogeneity in pig genome assembly Sscrofa9 by isochore and isochore-like region analyses.

    Directory of Open Access Journals (Sweden)

    Wenqian Zhang

    Full Text Available BACKGROUND: The isochore, a large DNA sequence with relatively small GC variance, is one of the most important structures in eukaryotic genomes. Although the isochore has been widely studied in humans and other species, little is known about its distribution in pigs. PRINCIPAL FINDINGS: In this paper, we construct a map of long homogeneous genome regions (LHGRs, i.e., isochores and isochore-like regions, in pigs to provide an intuitive version of GC heterogeneity in each chromosome. The LHGR pattern study not only quantifies heterogeneities, but also reveals some primary characteristics of the chromatin organization, including the followings: (1 the majority of LHGRs belong to GC-poor families and are in long length; (2 a high gene density tends to occur with the appearance of GC-rich LHGRs; and (3 the density of LINE repeats decreases with an increase in the GC content of LHGRs. Furthermore, a portion of LHGRs with particular GC ranges (50%-51% and 54%-55% tend to have abnormally high gene densities, suggesting that biased gene conversion (BGC, as well as time- and energy-saving principles, could be of importance to the formation of genome organization. CONCLUSION: This study significantly improves our knowledge of chromatin organization in the pig genome. Correlations between the different biological features (e.g., gene density and repeat density and GC content of LHGRs provide a unique glimpse of in silico gene and repeats prediction.

  20. Analyses of heterogeneous deformation and subsurface fatigue crack generation in alpha titanium alloy at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Umezawa, Osamu [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501 (Japan); Morita, Motoaki [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan and Now Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Yuasa, Takayuki [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan and Now Nippon Steel and Sumitomo Metal, Kashima, 314-0014 (Japan); Morooka, Satoshi [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan and Now Tokyo Metropolitan University, Hino, Tokyo 191-0065 (Japan); Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047 (Japan)

    2014-01-27

    Subsurface crack initiation in high-cycle fatigue has been detected as (0001) transgranular facet in titanium alloys at low temperature. The discussion on the subsurface crack generation was reviewed. Analyses by neutron diffraction and full constraints model under tension mode as well as crystallographic identification of the facet were focused. The accumulated tensile stress along <0001> may be responsible to initial microcracking on (0001) and the crack opening.

  1. Microstructural analyses of Cr(VI) speciation in chromite ore processing Residue (COPR)

    Energy Technology Data Exchange (ETDEWEB)

    CHRYSOCHOOU, MARIA; FAKRA, SIRINE C .; Marcus, Matthew A.; Moon, Deok Hyun; Dermatas, Dimitris

    2010-03-01

    The speciation and distribution of Cr(VI) in the solid phase was investigated for two types of chromite ore processing residue (COPR) found at two deposition sites in the United States: gray-black (GB) granular and hard brown (HB) cemented COPR. COPR chemistry and mineralogy were investigated using micro-X-ray absorption spectroscopy and micro-X-ray diffraction, complemented by laboratory analyses. GB COPR contained 30percent of its total Cr(VI) (6000 mg/kg) as large crystals(>20 ?m diameter) of a previously unreported Na-rich analog of calcium aluminum chromate hydrates. These Cr(VI)-rich phases are thought to be vulnerable to reductive and pH treatments. More than 50percent of the Cr(VI) was located within nodules, not easily accessible to dissolved reductants, and bound to Fe-rich hydrogarnet, hydrotalcite, and possibly brucite. These phases are stable over a large pH range, thus harder to dissolve. Brownmilleritewasalso likely associated with physical entrapment of Cr(VI) in the interior of nodules. HB COPR contained no Cr(VI)-rich phases; all Cr(VI) was diffuse within the nodules and absent from the cementing matrix, with hydrogarnet and hydrotalcite being the main Cr(VI) binding phases. Treatment ofHBCOPRis challenging in terms of dissolving the acidity-resistant, inaccessible Cr(VI) compounds; the same applies to ~;;50percent of Cr(VI) in GB COPR.

  2. Structural, microstructural and vibrational analyses of the monoclinic tungstate BiLuWO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Ait Ahsaine, H. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106 Cité Dakhla, Agadir (Morocco); Taoufyq, A. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106 Cité Dakhla, Agadir (Morocco); Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France); Patout, L. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France); Ezahri, M.; Benlhachemi, A.; Bakiz, B. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106 Cité Dakhla, Agadir (Morocco); Villain, S.; Guinneton, F. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France); Gavarri, J.-R., E-mail: gavarri.jr@univ-tln.fr [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France)

    2014-10-15

    The bismuth lutetium tungstate phase BiLuWO{sub 6} has been prepared using a solid state route with stoichiometric mixtures of oxide precursors. The obtained polycrystalline phase has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. In the first step, the crystal structure has been refined using Rietveld method: the crystal cell was resolved using monoclinic system (parameters a, b, c, β) with space group A2/m. SEM images showed the presence of large crystallites with a constant local nominal composition (BiLuW). TEM analyses showed that the actual local structure could be better represented by a superlattice (a, 2b, c, β) associated with space groups P2 or P2/m. The Raman spectroscopy showed the presence of vibrational bands similar to those observed in the compounds BiREWO{sub 6} with RE=Y, Gd, Nd. However, these vibrational bands were characterized by large full width at half maximum, probably resulting from the long range Bi/Lu disorder and local WO{sub 6} octahedron distortions in the structure. - Graphical abstract: The average structure of BiLuWO{sub 6} determined from X-ray diffraction data can be represented by A2/m space group. Experimental Electron Diffraction patterns along the [0vw] zone axes of the monoclinic structure and associated simulated patterns show the existence of a monoclinic superstructure with space group P2 or P2/m. - Highlights: • A new monoclinic BiLuWO{sub 6} phase has been elaborated from solid-state reaction. • The space group of the monoclinic disordered average structure should be A2/m. • Transmission electron microscopy leads to a superlattice with P2/m space group. • Raman spectroscopy suggests existence of local disorder.

  3. Visualising, segmenting and analysing heterogenous glacigenic sediments using 3D x-ray CT.

    Science.gov (United States)

    Carr, Simon; Diggens, Lucy; Groves, John; O'Sullivan, Catherine; Marsland, Rhona

    2015-04-01

    , especially with regard to using such data to improve understanding of mechanisms of particle motion and fabric development during subglacial strain. In this study, we present detailed investigation of subglacial tills from the UK, Iceland and Poland, to explore the challenges in segmenting these highly variable sediment bodies for 3D microfabric analysis. A calibration study is reported to compare various approaches to CT data segmentation to manually segmented datasets, from which an optimal workflow is developed, using a combination of the WEKA Trainable Segmentation tool within ImageJ to segment the data, followed by object-based analysis using Blob3D. We then demonstrate the value of this analysis through the analysis of true 3D microfabric data from a Last Glacial Maximum till deposit located at Morston, North Norfolk. Seven undisturbed sediment samples were scanned and analysed using high-resolution 3D X-ray computed tomography. Large (~5,000 to ~16,000) populations of individual particles are objectively and systematically segmented and identified. These large datasets are then subject to detailed interrogation using bespoke code for analysing particle fabric within Matlab, including the application of fabric-tensor analysis, by which fabrics can be weighted and scaled by key variables such as size and shape. We will present initial findings from these datasets, focusing particularly on overcoming the methodological challenges of obtaining robust datasets of sediments with highly complex, mixed compositional sediments.

  4. Sensitivity analyses of a colloid-facilitated contaminant transport model for unsaturated heterogeneous soil conditions.

    Science.gov (United States)

    Périard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean

    2013-04-01

    Certain contaminants may travel faster through soils when they are sorbed to subsurface colloidal particles. Indeed, subsurface colloids may act as carriers of some contaminants accelerating their translocation through the soil into the water table. This phenomenon is known as colloid-facilitated contaminant transport. It plays a significant role in contaminant transport in soils and has been recognized as a source of groundwater contamination. From a mechanistic point of view, the attachment/detachment of the colloidal particles from the soil matrix or from the air-water interface and the straining process may modify the hydraulic properties of the porous media. Šimůnek et al. (2006) developed a model that can simulate the colloid-facilitated contaminant transport in variably saturated porous media. The model is based on the solution of a modified advection-dispersion equation that accounts for several processes, namely: straining, exclusion and attachement/detachement kinetics of colloids through the soil matrix. The solutions of these governing, partial differential equations are obtained using a standard Galerkin-type, linear finite element scheme, implemented in the HYDRUS-2D/3D software (Šimůnek et al., 2012). Modeling colloid transport through the soil and the interaction of colloids with the soil matrix and other contaminants is complex and requires the characterization of many model parameters. In practice, it is very difficult to assess actual transport parameter values, so they are often calibrated. However, before calibration, one needs to know which parameters have the greatest impact on output variables. This kind of information can be obtained through a sensitivity analysis of the model. The main objective of this work is to perform local and global sensitivity analyses of the colloid-facilitated contaminant transport module of HYDRUS. Sensitivity analysis was performed in two steps: (i) we applied a screening method based on Morris' elementary

  5. The temperature-dependent microstructure of PEDOT/PSS films: insights from morphological, mechanical and electrical analyses

    KAUST Repository

    Zhou, Jian

    2014-09-24

    Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) is a widely used conductive polymer in the field of flexible electronics. The ways its microstructure changes over a broad range of temperatures remain unclear. This paper describes microstructure changes at different temperatures and correlates the microstructure with its physical properties (mechanical and electrical). We used High-Angle Annular Dark-Field Scanning Electron Microscopy (HAADF-STEM) combined with electron energy loss spectroscopy (EELS) to determine the morphology and elemental atomic ratio of the film at different temperatures. These results together with the Atomic Force Microscopy (AFM) analysis provide the foundation for a model of how the temperature affects the microstructure of PEDOT/PSS. Moreover, dynamic mechanical analysis (DMA) and electrical characterization were performed to analyze the microstructure and physical property correlations.

  6. Characterization and analyses on micro-hardness, residual stress and microstructure in laser cladding coating of 316L stainless steel subjected to massive LSP treatment

    Energy Technology Data Exchange (ETDEWEB)

    Luo, K.Y.; Jing, X.; Sheng, J. [School of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China); Sun, G.F. [School of Mechanical Engineering, Southeast University, Nanjing, 211189 (China); Yan, Z. [School of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China); Lu, J.Z., E-mail: jzlu@ujs.edu.cn [School of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China)

    2016-07-15

    The effects of massive laser shock peening (LSP) treatment on micro-hardness, residual stress and microstructure in four different zones of laser cladding coating was investigated. Furthermore, micro-hardness curves and residual stress distributions with and without massive LSP treatment were presented and compared, and typical microstructure in different zones of both coatings were characterized by transmission electron microscope (TEM) and cross-sectional optical microscope (OM) observations. Results and analyses showed that massive LSP treatment had an important influence on micro-hardness and residual stress of the cladding coating. Special attempt was made to the effects of massive LSP treatment on microstructure in three zones of the cladding coating. In addition, the underlying mechanism of massive LSP treatment on microstructure and mechanical properties of the cladding coating was revealed clearly. - Highlights: • Micro-hardness and residual stress curves of both coatings were presented and compared. • Typical microstructure in different zones of both coatings were characterized and analyzed. • LSP causes increased micro-activities, and induces plastic deformation layer in three zones. • Underlying mechanism of LSP on mechanical properties of cladding coating was revealed.

  7. Complex strain paths in polycrystalline copper: microstructural aspects

    Directory of Open Access Journals (Sweden)

    M.F. Vieira

    1999-07-01

    Full Text Available Microstructural aspects of polycrystalline copper sheets subjected to complex strain paths were analysed in this work. Dislocation structures developed during the strain paths (rolling and tension and the evolution of this microstructure during reloading have been studied. The active slip systems developed in each strain path were used to explain the microstructural evolution. The heterogeneous surface deformation observed on polished tensile specimens prestrained in rolling was also analysed. The structural aspects are related with the mechanical behaviour of the material, namely with the increase in yield stress in reloading, the work hardening evolution and the premature occurrence of plastic instability for some prestrain values.

  8. The effects of clinical and statistical heterogeneity on the predictive values of results from meta-analyses

    NARCIS (Netherlands)

    Melsen, W G; Rovers, M M; Bonten, M J M; Bootsma, M C J

    2014-01-01

    Variance between studies in a meta-analysis will exist. This heterogeneity may be of clinical, methodological or statistical origin. The last of these is quantified by the I(2) -statistic. We investigated, using simulated studies, the accuracy of I(2) in the assessment of heterogeneity and the effec

  9. Effects of can parameters on canned-forging process of TiAl base alloy(Ⅰ)--Microstructural analyses

    Institute of Scientific and Technical Information of China (English)

    刘咏; 韦伟峰; 黄伯云; 何双珍; 周科朝; 贺跃辉

    2002-01-01

    By using thermal simulation technique, the conventional canned-forging process of TiAl based alloy was studied. The effect of can parameters on the microstruct ures of TiAl alloy was analyzed in this process. The results show that, the defo rmation microstructure of TiAl based alloy without canning is inhomogeneous. In lateral area, crack and shearing lines can be found; while in central area, fine -grained shearing zone can be found. The effect of can is to reduce the seconda ry tensile stress. However, only when the deformation of the steel can is coinci dental with that of TiAl alloy ingot, can this effect be effective. Moreover, a thick can would enhance the microstructural homogeneity in TiAl based alloy. With the H/D ratio of the ingot increasing, the deformation of TiAl alloy would be more unsteady, therefore, a thicker can should be needed.

  10. High-throughput Exploration of Glass Formation via Laser Deposition and the Study of Heterogeneous Microstructure in a Bulk Metallic Glass Alloy

    Science.gov (United States)

    Tsai, Peter T.

    . Recent studies indicate that the macroscopic deformation behavior of the material may be controlled by structural heterogeneities, although the exact nature and origin of the heterogeneities remain ambiguous. To further the present knowledge, the heterogeneous microstructure of a zirconium-based bulk metallic glass was investigated with instrumented nanoindentation and dynamic modulus mapping. Significant spatial variations in the mechanical properties measured by both techniques suggests a hierarchical arrangement of structural/mechanical heterogeneities in bulk metallic glasses. Moreover, a previously unobserved elastic microstructure, comprising an interconnected network of elastic features, was revealed by dynamic modulus mapping. Despite the absence of visible contrast when imaged with electron microscopy, the aligned morphology of the elastic features and their sensitivity to thermal processing conditions imply the occurrence of spinodal decomposition in the supercooled liquid prior to glass formation. Finally, based on analysis of load-displacement data from nanoindentation experiments performed throughout the thesis work, a new parameter, the plastic work ratio, was proposed as a figure of merit for quantifying the intrinsic plasticity of monolithic metallic glass alloys.

  11. Microstructure and micro-hardness analyses of titanium alloy Ti-6Al-4V parts manufactured by selective laser melting

    Directory of Open Access Journals (Sweden)

    Lancea Camil

    2017-01-01

    Full Text Available Selective Laser Melting (SLM is one of the powder based additive manufacturing technologies and it is, as well, the most rapidly growing technique in Rapid Prototyping. In this paper is presented a microstructure analysis using Scanning Electron Microscope (LEO 1525 SEM, of Ti6Al4V parts exposed into a corrosion environment. The corrosion environment was generated using a salt chamber with 5% and 10% NaCl concentration and an ACS-Sunrise climatic chamber. The parts were also subjected to tests in order to determine their micro-hardness, followed by a statistical processing of the obtained data. The parts, having a lattice structure, were built on a Selective Laser Melting machine.

  12. Linking properties to microstructure through multiresolution mechanics

    Science.gov (United States)

    McVeigh, Cahal James

    The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient than modeling the detailed microstructure, the relationship between microstructure and macroscale properties becomes unclear. In order to perform computational materials design, material models must clearly relate the key underlying microstructural parameters (cause) to macroscale properties (effect). In this thesis, microstructure evolution and instability events are related to macroscale mechanical properties through a new multiresolution continuum analysis approach. The multiresolution nature of this theory allows prediction of the evolving magnitude and scale of deformation as a direct function of the changing microstructure. This is achieved via a two-pronged approach: (a) Constitutive models which track evolving microstructure are developed and calibrated to direct numerical simulations (DNS) of the microstructure. (b) The conventional homogenized continuum equations of motion are extended via a virtual power approach to include extra coupled microscale stresses and stress couples which are active at each characteristic length scale within the microstructure. The multiresolution approach is applied to model the fracture toughness of a cemented carbide, failure of a steel alloy under quasi-static loading conditions and the initiation and velocity of adiabatic shear bands under high speed dynamic loading. In each case the multiresolution analysis predicts the important scale effects which control the macroscale material response. The strain fields predicted in the multiresolution continuum analyses compare well to those observed in direct numerical simulations of the

  13. Performance Analyses and Improvements for the IEEE 802.15.4 CSMA/CA Scheme with Heterogeneous Buffered Conditions

    Directory of Open Access Journals (Sweden)

    Chunfeng Lv

    2012-04-01

    Full Text Available Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results.

  14. Performance Analyses and Improvements for the IEEE 802.15.4 CSMA/CA Scheme with Heterogeneous Buffered Conditions

    Science.gov (United States)

    Zhu, Jianping; Tao, Zhengsu; Lv, Chunfeng

    2012-01-01

    Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results. PMID:22666076

  15. Performance analyses and improvements for the IEEE 802.15.4 CSMA/CA scheme with heterogeneous buffered conditions.

    Science.gov (United States)

    Zhu, Jianping; Tao, Zhengsu; Lv, Chunfeng

    2012-01-01

    Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes-OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)-are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results.

  16. Analyses of point mutation repair and allelic heterogeneity generated by CRISPR/Cas9 and single-stranded DNA oligonucleotides.

    Science.gov (United States)

    Bialk, Pawel; Sansbury, Brett; Rivera-Torres, Natalia; Bloh, Kevin; Man, Dula; Kmiec, Eric B

    2016-09-09

    The repair of a point mutation can be facilitated by combined activity of a single-stranded oligonucleotide and a CRISPR/Cas9 system. While the mechanism of action of combinatorial gene editing remains to be elucidated, the regulatory circuitry of nucleotide exchange executed by oligonucleotides alone has been largely defined. The presence of the appropriate CRISPR/Cas9 system leads to an enhancement in the frequency of gene editing directed by single-stranded DNA oligonucleotides. While CRISPR/Cas9 executes double-stranded DNA cleavage efficiently, closure of the broken chromosomes is dynamic, as varying degrees of heterogeneity of the cleavage products appear to accompany the emergence of the corrected base pair. We provide a detailed analysis of allelic variance at and surrounding the target site. In one particular case, we report sequence alteration directed by a distinct member of the same gene family. Our data suggests that single-stranded DNA molecules may influence DNA junction heterogeneity created by CRISPR/Cas9.

  17. Quality control of cultured tissues requires tools for quantitative analyses of heterogeneous features developed in manufacturing process.

    Science.gov (United States)

    Kino-Oka, Masahiro; Takezawa, Yasunori; Taya, Masahito

    2009-02-01

    Tissue engineering and related technology have attracted a great deal of medical attention as promising fields for curing defective tissues in vivo. Nowadays, many companies have been established for supplying the reconstructed grafts of cultured tissues for transplantation. The manufacturing processes generally deals with the handlings of starter cells offered by patients (or donors) as raw materials to cultured tissues as products, requiring the construction of novel ex vivo methodologies based on principles different from conventional processes for chemical and pharmaceutical productions. In addition, the raw materials have heterogeneity depending on the state of patients and location of cell harvests, and the products possess spatial cell distribution in the three dimensional structure. These features request a unique strategy in manufacturing process accompanied with the quality control for raw materials and products. This review article describes the contribution of tissue bankers and biochemical engineers to the quality control of cultured tissues during manufacturing, introducing the advances in methodologies to evaluate spatial heterogeneity of cells (or aggregates) and matrices in cultured tissues.

  18. Genome-wide analyses of non-syndromic cleft lip with palate identify 14 novel loci and genetic heterogeneity

    Science.gov (United States)

    Yu, Yanqin; Zuo, Xianbo; He, Miao; Gao, Jinping; Fu, Yuchuan; Qin, Chuanqi; Meng, Liuyan; Wang, Wenjun; Song, Yaling; Cheng, Yong; Zhou, Fusheng; Chen, Gang; Zheng, Xiaodong; Wang, Xinhuan; Liang, Bo; Zhu, Zhengwei; Fu, Xiazhou; Sheng, Yujun; Hao, Jiebing; Liu, Zhongyin; Yan, Hansong; Mangold, Elisabeth; Ruczinski, Ingo; Liu, Jianjun; Marazita, Mary L.; Ludwig, Kerstin U.; Beaty, Terri H.; Zhang, Xuejun; Sun, Liangdan; Bian, Zhuan

    2017-01-01

    Non-syndromic cleft lip with palate (NSCLP) is the most serious sub-phenotype of non-syndromic orofacial clefts (NSOFC), which are the most common craniofacial birth defects in humans. Here we conduct a GWAS of NSCLP with multiple independent replications, totalling 7,404 NSOFC cases and 16,059 controls from several ethnicities, to identify new NSCLP risk loci, and explore the genetic heterogeneity between sub-phenotypes of NSOFC. We identify 41 SNPs within 26 loci that achieve genome-wide significance, 14 of which are novel (RAD54B, TMEM19, KRT18, WNT9B, GSC/DICER1, PTCH1, RPS26, OFCC1/TFAP2A, TAF1B, FGF10, MSX1, LINC00640, FGFR1 and SPRY1). These 26 loci collectively account for 10.94% of the heritability for NSCLP in Chinese population. We find evidence of genetic heterogeneity between the sub-phenotypes of NSOFC and among different populations. This study substantially increases the number of genetic susceptibility loci for NSCLP and provides important insights into the genetic aetiology of this common craniofacial malformation. PMID:28232668

  19. Heterogeneity and Microeconometrics Modelling

    DEFF Research Database (Denmark)

    Browning, Martin; Carro, Jesus

    Presented at the 2005 Econometric Society World Congress Plenary Session on "Modelling Heterogeneity". We survey the treatment of heterogeneity in applied microeconometrics analyses. There are three themes. First, there is usually much more heterogeneity than empirical researchers allow for. Seco...

  20. Discontinuous Galerkin methods and a posteriori error analysis for heterogenous diffusion problems; Methodes de Galerkine discontinues et analyse d'erreur a posteriori pour les problemes de diffusion heterogene

    Energy Technology Data Exchange (ETDEWEB)

    Stephansen, A.F

    2007-12-15

    In this thesis we analyse a discontinuous Galerkin (DG) method and two computable a posteriori error estimators for the linear and stationary advection-diffusion-reaction equation with heterogeneous diffusion. The DG method considered, the SWIP method, is a variation of the Symmetric Interior Penalty Galerkin method. The difference is that the SWIP method uses weighted averages with weights that depend on the diffusion. The a priori analysis shows optimal convergence with respect to mesh-size and robustness with respect to heterogeneous diffusion, which is confirmed by numerical tests. Both a posteriori error estimators are of the residual type and control the energy (semi-)norm of the error. Local lower bounds are obtained showing that almost all indicators are independent of heterogeneities. The exception is for the non-conforming part of the error, which has been evaluated using the Oswald interpolator. The second error estimator is sharper in its estimate with respect to the first one, but it is slightly more costly. This estimator is based on the construction of an H(div)-conforming Raviart-Thomas-Nedelec flux using the conservativeness of DG methods. Numerical results show that both estimators can be used for mesh-adaptation. (author)

  1. Heterogeneity of groundwater storage properties in the critical zone of Irish metamorphic basement from geophysical surveys and petrographic analyses

    Science.gov (United States)

    Comte, Jean-Christophe; Cassidy, Rachel; Caulfield, John; Nitsche, Janka; Ofterdinger, Ulrich; Wilson, Christopher

    2016-04-01

    Weathered/fractured bedrock aquifers contain groundwater resources that are crucial in hard rock basement regions for rural water supply and maintaining river flow and ecosystem resilience. Groundwater storage in metamorphic rocks is subject to high spatial variations due to the large degree of heterogeneity in fracture occurrence and weathering patterns. Point measurements such as borehole testing are, in most cases, insufficient to characterise and quantify those storage variations because borehole sampling density is usually much lower than the scale of heterogeneities. A suite of geophysical and petrographic investigations was implemented in the weathered/fractured micaschist basement of Donegal, NW Ireland. Electrical Resistivity Tomography provided a high resolution 2D distribution of subsurface resistivities. Resistivity variations were transferred into storage properties (i.e. porosities) in the saturated critical zone of the aquifer through application of a petrophysical model derived from Archie's Law. The petrophysical model was calibrated using complementary borehole gamma logging and clay petrographic analysis at multi-depth well clusters distributed along a hillslope transect at the site. The resulting distribution of porosities shows large spatial variations along the studied transect. With depth, porosities rapidly decrease from about a few % in the uppermost, highly weathered basement to less than 0.5% in the deep unweathered basement, which is encountered at depths of between 10 and 50m below the ground surface. Along the hillslope, porosities decrease with distance from the river in the valley floor, ranging between 5% at the river to less than 1% at the top of the hill. Local traces of regional fault zones that intersect the transect are responsible for local increases in porosity in relation to deeper fracturing and weathering. Such degrees of spatial variation in porosity are expected to have a major impact on the modality of the response of

  2. Analysing capture--recapture data when some variables of heterogeneous catchability are not collected or asked in all registrations.

    Science.gov (United States)

    Zwane, Eugene N; van der Heijden, Peter G M

    2007-02-28

    Registrations in epidemiological studies suffer from incompleteness, thus a general consensus is to use capture-recapture models. Lately, there has been a thrust to incorporate covariates which relate to the capture probabilities in order to improve the estimate of population size. Current approaches utilize covariates observed in all the pertinent registrations. In epidemiological applications, one often encounters capture-recapture data where some covariates are measured by some but not by all of the registrations under scrutiny. In this article, the usefulness of these types of covariates is evaluated and furthermore a methodology for analysing such capture-recapture data is presented. The methodology is illustrated by applying it to data on neural tube defects in the Netherlands.

  3. Application of cluster and discriminant analyses to diagnose lithological heterogeneity of the parent material according to its particle-size distribution

    Science.gov (United States)

    Giniyatullin, K. G.; Valeeva, A. A.; Smirnova, E. V.

    2017-08-01

    Particle-size distribution in soddy-podzolic and light gray forest soils of the Botanical Garden of Kazan Federal University has been studied. The cluster analysis of data on the samples from genetic soil horizons attests to the lithological heterogeneity of the profiles of all the studied soils. It is probable that they are developed from the two-layered sediments with the upper colluvial layer underlain by the alluvial layer. According to the discriminant analysis, the major contribution to the discrimination of colluvial and alluvial layers is that of the fraction >0.25 mm. The results of canonical analysis show that there is only one significant discriminant function that separates alluvial and colluvial sediments on the investigated territory. The discriminant function correlates with the contents of fractions 0.05-0.01, 0.25-0.05, and >0.25 mm. Classification functions making it possible to distinguish between alluvial and colluvial sediments have been calculated. Statistical assessment of particle-size distribution data obtained for the plow horizons on ten plowed fields within the garden indicates that this horizon is formed from colluvial sediments. We conclude that the contents of separate fractions and their ratios cannot be used as a universal criterion of the lithological heterogeneity. However, adequate combination of the cluster and discriminant analyses makes it possible to give a comprehensive assessment of the lithology of soil samples from data on the contents of sand and silt fractions, which considerably increases the information value and reliability of the results.

  4. Linear and nonlinear analyses of multi-channel mechanomyographic recordings reveal heterogeneous activation of wrist extensors in presence of delayed onset muscle soreness.

    Science.gov (United States)

    Madeleine, Pascal; Hansen, Ernst A; Samani, Afshin

    2014-12-01

    In this study, we applied multi-channel mechanomyographic (MMG) recordings in combination with linear and nonlinear analyses to investigate muscular and musculotendinous effects of high intensity eccentric exercise. Twelve accelerometers arranged in a 3 × 4 matrix over the dominant elbow muscles were used to detect MMG activity in 12 healthy participants. Delayed onset muscle soreness was induced by repetitive high intensity eccentric contractions of the wrist extensor muscles. Average rectified values (ARV) as well as percentage of recurrence (%REC) and percentage of determinism (%DET) extracted from recurrence quantification analysis were computed from data obtained during static-dynamic contractions performed before exercise, immediately after exercise, and in presence of muscle soreness. A linear mixed model was used for the statistical analysis. The ARV, %REC, and %DET maps revealed heterogeneous MMG activity over the wrist extensor muscles before, immediately after, and in presence of muscle soreness (P<0.01). The ARVs were higher while the %REC and %DET were lower in presence of muscle soreness compared with before exercise (P<0.05). The study provides new key information on linear and nonlinear analyses of multi-channel MMG recordings of the wrist extensor muscles following eccentric exercise that results in muscle soreness. Recurrence quantification analysis can be suggested as a tool for detection of MMG changes in presence of muscle soreness.

  5. MRI analyses show that kinesio taping affects much more than just the targeted superficial tissues and causes heterogeneous deformations within the whole limb.

    Science.gov (United States)

    Pamuk, Uluç; Yucesoy, Can A

    2015-12-16

    Kinesio taping (KT) is widely used in the treatment of sports injuries and various neuro-musculoskeletal disorders. However, it is considered as selectively effective on targeted tissues and its mechanical effects have not been quantified objectively. Ascribed to continuity of muscular and connective tissues, mechanical loading imposed can have widespread heterogeneous effects. The aim was to characterize the mechanical effects of KT objectively and to test the hypotheses that KT causes acutely, local deformations not necessarily (I) in agreement with tape adhering direction and (II) limited to the directly targeted tissues. High-resolution 3D magnetic resonance image sets were acquired in healthy human subjects (n=5) prior to and acutely after KT application over the skin along m. tibialis anterior (TA). Hip, knee and ankle angles were kept constant. Demons image registration algorithm was used to calculate local tissue deformations within the lower leg, in vivo. Mean peak tissue strains were significantly higher than strain artifacts. Only KT-to-TA region in part shows local deformations in agreement with tape adhering direction whereas, superficial skin, the rest of KT-to-TA and TA regions show deformations (up to 51.5% length change) in other directions. Non-targeted tissues also show sizable heterogeneous deformations, but in smaller amplitudes. Inter-subject variability is notable. Magnetic resonance imaging analyses allow for a detailed assessment of local tissue deformation occurring acutely after KT application. The findings confirm our hypotheses and characterize how KT affects the underlying tissues, both immediately targeted and distant. This allows revealing mechanisms that can affect clinical outcomes of KT objectively.

  6. Inhomogeneous microstructural growth by irradiation

    DEFF Research Database (Denmark)

    Krishan, K.; Singh, Bachu Narain; Leffers, Torben

    1985-01-01

    In the present paper we discuss the development of heterogeneous microstructure for uniform irradiation conditions. It is shown that microstructural inhomogeneities on a scale of 0.1 μm can develop purely from kinematic considerations because of the basic structure of the rate equations used to d...

  7. Research on Heterogeneity of Microstructure of 600MPa Class Medium Plate%600MPa级中厚板组织的非均匀性研究

    Institute of Scientific and Technical Information of China (English)

    孙莹; 于庆波

    2012-01-01

    通过对600 MPa级中厚板显微组织观察后发现,沿板厚度方向形成的不均匀显微组织及魏氏组织使钢冲击韧性和塑性降低.另外,冷却过程中由于不平衡结晶而出现宏观偏析,导致600 MPa级钢的综合力学性能下降.%By observing the microstructure of 600 MPa class medium plate, there are inhomogeneous microstructure and widmanstatten structure along the thickness direction, which can lead to the decrease of impact toughness and ductility of the plate. In addition, the macro-segregation occurs due to the imbalance of crystallization during cooling, which can result in the decrease of comprehensive mechanical properties of 600 MPa class medium plate.

  8. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris

    Energy Technology Data Exchange (ETDEWEB)

    Brinza, Loredana [Diamond Light Source, Harwell Campus, Didcot, Oxon OX11 0DE (United Kingdom); Schofield, Paul F. [Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom); Hodson, Mark E. [University of York, York YO10 5DD (United Kingdom); Weller, Sophie [University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D.; Mosselmans, J. Frederick W., E-mail: fred.mosselmans@diamond.ac.uk [Diamond Light Source, Harwell Campus, Didcot, Oxon OX11 0DE (United Kingdom)

    2014-01-01

    A new experimental set-up enabling microfocus fluorescence XANES mapping and microfocus XRD mapping on the same sample at beamline I18 at Diamond Light Source is described. To demonstrate this set-up the heterogeneous mineralogy in calcium carbonate granules excreted by the earthworm Lumbricus terrestris has been analysed. Data analysis methods have been developed which enable µXRD and µXANES two-dimensional maps to be compared. The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.

  9. HETEROGENEOUS MICROSTRUCTURE AND TEXTURE EVOLUTION DURING FABRICATION OF Zr-Sn-Nb ZIRCONIUM ALLOY SHEETS%Zr-Sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

    Institute of Scientific and Technical Information of China (English)

    陈建伟; 栾佰峰; 柴林江; 余泓冰; 刘庆; 周军; 李中奎

    2012-01-01

    parallel to rolling direction {(1210)//RD}. The microstructure evolves from a weave Widmansatten structure of β quenching stage to heterogeneous deformation structures associated with hot and cold rolling and then to a fully recrystallized structure after final annealing. The cold rolling sheets present more heterogeneous structures in which the C axes of less deformed grains mostly concentrate in the normal direction The larger grains in annealed structures mostly belong to the (1210)}//RD basal texture while the smaller grains are in the (1010)//RD orientation. The reason for the heterogeneous deformation structures and texture evolution during annealing are discussed according to the deformation and recrystallization mechanisms.

  10. Yucatan Subsurface Stratigraphy from Geophysical Data, Well Logs and Core Analyses in the Chicxulub Impact Crater and Implications for Target Heterogeneities

    Science.gov (United States)

    Canales, I.; Fucugauchi, J. U.; Perez-Cruz, L. L.; Camargo, A. Z.; Perez-Cruz, G.

    2011-12-01

    Asymmetries in the geophysical signature of Chicxulub crater are being evaluated to investigate on effects of impact angle and trajectory and pre-existing target structural controls for final crater form. Early studies interpreted asymmetries in the gravity anomaly in the offshore sector to propose oblique either northwest- and northeast-directed trajectories. An oblique impact was correlated to the global ejecta distribution and enhanced environmental disturbance. In contrast, recent studies using marine seismic data and computer modeling have shown that crater asymmetries correlate with pre-existing undulations of the Cretaceous continental shelf, suggesting a structural control of target heterogeneities. Documentation of Yucatan subsurface stratigraphy has been limited by lack of outcrops of pre-Paleogene rocks. The extensive cover of platform carbonate rocks has not been affected by faulting or deformation and with no rivers cutting the carbonates, information comes mainly from the drilling programs and geophysical surveys. Here we revisit the subsurface stratigraphy in the crater area from the well log data and cores retrieved in the drilling projects and marine seismic reflection profiles. Other source of information being exploited comes from the impact breccias, which contain a sampling of disrupted target sequences, including crystalline basement and Mesozoic sediments. We analyze gravity and seismic data from the various exploration surveys, including multiple Pemex profiles in the platform and the Chicxulub experiments. Analyses of well log data and seismic profiles identify contacts for Lower Cretaceous, Cretaceous/Jurassic and K/Pg boundaries. Results show that the Cretaceous continental shelf was shallower on the south and southwest than on the east, with emerged areas in Quintana Roo and Belize. Mesozoic and upper Paleozoic sediments show variable thickness, possibly reflecting the crystalline basement regional structure. Paleozoic and Precambrian

  11. Microstructure of neat alcohols

    CERN Document Server

    Perera, A; Zoranic, L; Perera, Aurelien; Sokolic, Franjo; Zoranic, Larisa

    2007-01-01

    Formation of microstructure in homogeneous associated liquids is analysed through the density-density pair correlation functions, both in direct and reciprocal space, as well as an effective local one-body density function. This is illustrated through a molecular dynamics study of two neat alcohols, namely methanol and \\emph{tert}-butanol, which have a rich microstructure: chain-like molecular association for the former and micelle-like for the latter. The relation to hydrogen bonding interaction is demonstrated. The apparent failure to find microstructure in water -a stronger hydrogen bonding liquid- with the same tools, is discussed.

  12. Power and Sample Size Calculations for Testing Linear Combinations of Group Means under Variance Heterogeneity with Applications to Meta and Moderation Analyses

    Science.gov (United States)

    Shieh, Gwowen; Jan, Show-Li

    2015-01-01

    The general formulation of a linear combination of population means permits a wide range of research questions to be tested within the context of ANOVA. However, it has been stressed in many research areas that the homogeneous variances assumption is frequently violated. To accommodate the heterogeneity of variance structure, the…

  13. Advances in methods of commercial FBR core characteristics analyses. Investigations of a treatment of the double-heterogeneity and a method to calculate homogenized control rod cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Sugino, Kazuteru [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center; Iwai, Takehiko

    1998-07-01

    A standard data base for FBR core nuclear design is under development in order to improve the accuracy of FBR design calculation. As a part of the development, we investigated an improved treatment of double-heterogeneity and a method to calculate homogenized control rod cross sections in a commercial reactor geometry, for the betterment of the analytical accuracy of commercial FBR core characteristics. As an improvement in the treatment of double-heterogeneity, we derived a new method (the direct method) and compared both this and conventional methods with continuous energy Monte-Carlo calculations. In addition, we investigated the applicability of the reaction rate ratio preservation method as a advanced method to calculate homogenized control rod cross sections. The present studies gave the following information: (1) An improved treatment of double-heterogeneity: for criticality the conventional method showed good agreement with Monte-Carlo result within one sigma standard deviation; the direct method was consistent with conventional one. Preliminary evaluation of effects in core characteristics other than criticality showed that the effect of sodium void reactivity (coolant reactivity) due to the double-heterogeneity was large. (2) An advanced method to calculate homogenize control rod cross sections: for control rod worths the reaction rate ratio preservation method agreed with those produced by the calculations with the control rod heterogeneity included in the core geometry; in Monju control rod worth analysis, the present method overestimated control rod worths by 1 to 2% compared with the conventional method, but these differences were caused by more accurate model in the present method and it is considered that this method is more reliable than the conventional one. These two methods investigated in this study can be directly applied to core characteristics other than criticality or control rod worth. Thus it is concluded that these methods will

  14. Microstructural analyses of B{sub 4}C-CeO{sub 2} and B{sub 4}C-La{sub 2}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Tatsuaki, E-mail: sakamoto.tatsuaki@eng.ehime-u.ac.jp [Department of Materials Science and Biotechnology, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Sun, Shu-Chen [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Furuno, Tomoya; Kajioka, Michio [Graduate Student of Ehime Univerisity, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Nakai, Kiyomichi [Department of Materials Science and Biotechnology, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Kurishita, Hiroaki [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Kobayashi, Sengo [Department of Materials Science and Biotechnology, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Wu, Wen-Yuan; Tu, Gan-Feng [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Matsuda, Seiji [Department of Anatomy and Embryology, Ehime University, Shizugawa, Toon 791-0295 (Japan)

    2011-10-01

    Effects of additions of CeO{sub 2} and La{sub 2}O{sub 3} on microstructure and mechanical properties of B{sub 4}C fabricated under and without hot press have been investigated. Vickers hardness and fracture strength are increased by hot press due to the reduction of porosity because the sintering rate is enhanced. Hardness is increased by the reduction of porosity because crack probably occurs when the hardness is measured due to pore as an initiation point of crack. Hardness increases with increasing additions of CeO{sub 2} and La{sub 2}O{sub 3} because porosity decreases due to the formation of CeB{sub 6} and LaB{sub 6} on the grain boundary of B{sub 4}C, respectively. The borides are formed through reaction between solid phases, which might induce coherent boundary between boride and B{sub 4}C. Such coherency also contributes to strengthening the grain boundary of B{sub 4}C. The addition of CeO{sub 2} enhances the sintering rate more than that of La{sub 2}O{sub 3}, resulting in higher hardness of B{sub 4}C-CeO{sub 2} than that of B{sub 4}C-La{sub 2}O{sub 3}.

  15. Micromechanics of heterogeneous materials

    CERN Document Server

    Buryachenko, Valeriy

    2007-01-01

    Here is an accurate and timely account of micromechanics, which spans materials science, mechanical engineering, applied mathematics, technical physics, geophysics, and biology. The book features rigorous and unified theoretical methods of applied mathematics and statistical physics in the material science of microheterogeneous media. Uniquely, it offers a useful demonstration of the systematic and fundamental research of the microstructure of the wide class of heterogeneous materials of natural and synthetic nature.

  16. Uncertainties in vertical groundwater fluxes from 1-D steady state heat transport analyses caused by heterogeneity, multidimensional flow, and climate change

    Science.gov (United States)

    Irvine, Dylan J.; Cartwright, Ian; Post, Vincent E. A.; Simmons, Craig T.; Banks, Eddie W.

    2016-02-01

    Steady state 1-D analytical solutions to estimate groundwater fluxes from temperature profiles are an attractive option because they are simple to apply, with no complex boundary or initial conditions. Steady state solutions have been applied to estimate both aquifer scale fluxes as well as to estimate groundwater discharge to streams. This study explores the sources of uncertainty in flux estimates from regional scale aquifers caused by sensor precision, aquifer heterogeneity, multidimensional flow and variations in surface temperature due to climate change. Synthetic temperature profiles were generated using 2-D groundwater flow and heat transport models with homogeneous and heterogeneous hydraulic and thermal properties. Temperature profiles were analyzed assuming temperature can be determined with a precision between 0.1°C and 0.001°C. Analysis of synthetic temperature profiles show that the Bredehoeft and Papadopulos (1965) method can provide good estimates of the mean vertical Darcy flux over the length of the temperature profile. Reliable flux estimates were obtained when the ratio of vertical to horizontal flux was as low as 0.1, and in heterogeneous media, providing that temperature at the upper boundary was constant in time. However, temporal increases in surface temperature led to over-estimation of fluxes. Overestimates increased with time since the onset of, and with the rate of surface warming. Overall, the Bredehoeft and Papadopulos (1965) method may be more robust for the conditions with constant temperature distributions than previously thought, but that transient methods that account for surface warming should be used to determine fluxes in shallow aquifers.

  17. Reevaluation of JACS code system benchmark analyses of the heterogeneous system. Fuel rods in U+Pu nitric acid solution system

    Energy Technology Data Exchange (ETDEWEB)

    Takada, Tomoyuki; Miyoshi, Yoshinori; Katakura, Jun-ichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    In order to perform accuracy evaluation of the critical calculation by the combination of multi-group constant library MGCL and 3-dimensional Monte Carlo code KENO-IV among critical safety evaluation code system JACS, benchmark calculation was carried out from 1980 in 1982. Some cases where the neutron multiplication factor calculated in the heterogeneous system in it was less than 0.95 were seen. In this report, it re-calculated by considering the cause about the heterogeneous system of the U+Pu nitric acid solution systems containing the neutron poison shown in JAERI-M 9859. The present study has shown that the k{sub eff} value less than 0.95 given in JAERI-M 9859 is caused by the fact that the water reflector below a cylindrical container was not taken into consideration in the KENO-IV calculation model. By taking into the water reflector, the KENO-IV calculation gives a k{sub eff} value greater than 0.95 and a good agreement with the experiment. (author)

  18. Cu/Al真空扩散焊接头显微组织分析%Microstructure analyses in vacuum diffusion welded joint of copper and aluminum

    Institute of Scientific and Technical Information of China (English)

    李亚江; 吴会强; 陈茂爱; 杨敏; 冯涛

    2001-01-01

    采用真空扩散焊工艺方法,对Cu与Al扩散焊接头的组织性能进行了试验研究,利用扫描电镜(SEM)、电子探针(EPMA)、显微硬度等测试方法对焊接过渡区及基体组织和性能进行了分析。试验结果表明:采用真空扩散焊工艺,在加热温度520~540 ℃,保温时间60 min,压力11.5 MPa时,在Cu/Al界面处形成明显的扩散过渡区,扩散区域宽约40 μm。在铜侧过渡区中产生金属间化合物,会出现显微硬度高峰区,控制Al的扩散浓度可避免或减少界面处金属间化合物的产生。%By using vacuum diffusion welding process, the microstructures and performance of diffusion transition zone for the Cu/Al diffusion welding joint were researched by means of SEM, EPMA and micro-hardness test. The results indicate that under the condition of 520~540?℃ in holding time 60?min and pressure 11.5?MPa, the diffusion joined interface is obviously produced between copper and aluminum. The width of the diffusion interface zone is about 40?μm. The micro-hardness peak zone is formed in the copper side of the joined interface because of metal compounds such as γ and β phase. By controlling the Al diffusion amount, the brittle intermetallic compounds can be avoided or decreased.

  19. Meta回归与亚组分析在异质性处理中的应用%Application of Meta-regression and subgroup analyses of heterogeneity disposal in Meta-analysis

    Institute of Scientific and Technical Information of China (English)

    石修权; 王增珍

    2008-01-01

    探讨Meta回归与亚组分析在异质性的识别与处理中的应用及意义.利用文献提供的二次数据建立Meta回归模型,筛选出异质性的影响因素,根据该因素做亚组分析,并比较亚组分析前后异质性的变化.Meta分析资料经异质性检验,Q=44.71,df=27,P=0.017,认为存在异质性.经Meta回归分析,从可能导致异质性的因素(研究时间、地区、样本量、病例对照比值等)中筛选出样本含量为异质性因素(P=0.012)、地区为可能的异质性因素(P=0.091).然后进行亚组分析,异质性明显减小(∑Q 由44.71减小至32.11).结论 :Meta回归法对筛选异质性影响因素比较简便可靠,据此进行的亚组分析能明显降低亚组内的异质性.故存在统计学异质性又要计算合并效应时推荐二者结合使用,可正确识别并降低异质性,从而使Meta分析结果更为稳健与合理.%To explore the role and application of Meta-regression and subgroup analyses to recognize and control the heterogeneity in Meta-analysis, Meta-regression models were established by secondary data to screen the factors resulting heterogeneity,and subgroup analyses were used to compare the change of heterogeneity before and after.The heterogeneity was found in the Meta-analysis(Q=44.71,df=27,P=0.017).Sample size and region were selected(P=0.012 and P=0.091,respectively)by Meta-regression from many possible factors such as sample size,year,region and case/contml ratio.The Q values were lowered from 44.71 to 32.11 after subgroup analyses.Thus,Metaregression method was convenient and reliable to screen the affected factors of heterogeneity,and subgroup analyses based on the hypothesis that could significantly lower the heterogeneity.It was recommended to a combined use when an obvious heterogeneity existed but was in need to get an overall result in Metaanalysis.We could correctly judge and lower the heterogeneity to increase the robustness and rationality of results from Meta-analysis.

  20. Applications of Micro-CT scanning in medicine and dentistry: Microstructural analyses of a Wistar Rat mandible and a urinary tract stone

    Science.gov (United States)

    Latief, F. D. E.; Sari, D. S.; Fitri, L. A.

    2017-08-01

    High-resolution tomographic imaging by means of x-ray micro-computed tomography (μCT) has been widely utilized for morphological evaluations in dentistry and medicine. The use of μCT follows a standard procedure: image acquisition, reconstruction, processing, evaluation using image analysis, and reporting of results. This paper discusses methods of μCT using a specific scanning device, the Bruker SkyScan 1173 High Energy Micro-CT. We present a description of the general workflow, information on terminology for the measured parameters and corresponding units, and further analyses that can potentially be conducted with this technology. Brief qualitative and quantitative analyses, including basic image processing (VOI selection and thresholding) and measurement of several morphometrical variables (total VOI volume, object volume, percentage of total volume, total VOI surface, object surface, object surface/volume ratio, object surface density, structure thickness, structure separation, total porosity) were conducted on two samples, the mandible of a wistar rat and a urinary tract stone, to illustrate the abilities of this device and its accompanying software package. The results of these analyses for both samples are reported, along with a discussion of the types of analyses that are possible using digital images obtained with a μCT scanning device, paying particular attention to non-diagnostic ex vivo research applications.

  1. Microstructural characterization of nickel subjected to dynamic plastic deformation

    DEFF Research Database (Denmark)

    Luo, Z.P.; Mishin, Oleg; Zhang, Yubin;

    2012-01-01

    Average microstructural parameters and the extent of microstructural heterogeneity in nickel deformed at a high strain rate have been characterized quantitatively and compared to those after compression at a quasi-static strain rate. The microstructure in the high strain rate sample was found...

  2. Microstructural characterization of nickel subjected to dynamic plastic deformation

    DEFF Research Database (Denmark)

    Luo, Z.P.; Mishin, Oleg; Zhang, Yubin

    2012-01-01

    Average microstructural parameters and the extent of microstructural heterogeneity in nickel deformed at a high strain rate have been characterized quantitatively and compared to those after compression at a quasi-static strain rate. The microstructure in the high strain rate sample was found to ...

  3. Contribution of stimulations for the optimization of quantitative electron probe micro analysis of heterogeneous catalysts; Apport de la simulation dans l'optimisation de l'analyse quantitative par microsonde electronique de catalyseurs heterogenes

    Energy Technology Data Exchange (ETDEWEB)

    Sorbier, L.

    2001-11-01

    Electron Probe Micro Analysis (EPMA) is frequently used to measure the local concentration of active elements in heterogeneous catalysts. However, when classical procedures are used, a significant deficit is observed both in local total concentration and mean total concentrations. A Monte Carlo program simulating measured intensities (characteristic lines and continuous background) has been written using PENELOPE routines. We have included in this program models taking into account the different physical phenomena likely to lead to the observed signal loss (insulating properties, roughness, porosity, energy loss at interfaces). Simulation results have shown that an important roughness (Ra>200 nm) was the only parameter apt to lead to a significant total signal loss. This led us to inquire into another origin to explain the signal loss observed on meso-porous samples. Measurements conducted on a meso-porous alumina confirmed that measuring aluminum, oxygen and carbon leads to a correct total of concentrations. Signal loss is thus explained by the contamination of the sample during its preparation, the components of the embedding resin diffusing into the porosity and reacting with the reactive surface of the catalyst support. In the case of macroporous catalysts, local roughness effect is very important. The simulations have shown the efficiency of the Peak to Background method to correct these local roughness effects. Measurements conducted on reforming and hydro-treating catalysts have led to a correct total concentration and confirmed the contribution of the Peak to Background method to achieve local quantitative measurement. (author)

  4. The heterogeneous Gleason 7 carcinoma of the prostate: analyses of low and high grade (risk) carcinomas with criteria of the International Society of Urological Pathology (ISUP).

    Science.gov (United States)

    Helpap, Burkhard; Ringli, Daniel; Shaikhibrahim, Zaki; Wernert, Nicolas; Kristiansen, Glen

    2013-03-01

    Prostate carcinoma (PCa) with Gleason score (GS) 7 has to be examined differentially regarding its prognosis. Using the criteria of ISUP and supplementations, we attempted to analyze the heterogeneity of PCa with GS 7 of biopsy and corresponding specimens of radical prostatectomies (RP). PCa of 530 patients were graded according to Gleason under additional consideration of the state of the nucleoli. Investigating the biopsy specimens, we determined the pattern of Gleason 4 of GS 7, the extension of the tumors in percent, and the number of biopsies containing tumor. In the corresponding specimens of RP, the grading and the state of TNM with margins were assessed. Carcinomas with GS 7 (4+3) in biopsy and RP specimens were unequivocally assigned to the group of high-grade tumors. Carcinomas with GS 7 (3+4) were significantly different from carcinomas with GS 6 when only few and small nucleoli in GS 6 were present (low grade type, p≤0.0001), but were similar to the GS 6 group when nucleoli were prominent (intermediary type, p=0.71). The intermediary group showed an upgrading rate of 36% from GS 6 to GS 7. Furthermore the correlation between organ-confined and non-organ-confined growth showed differences of 63% and 37% in the intermediary group (p=0.0001). The values of grading, staging, margins and metastases indicate that carcinomas of the prostate with the Gleason 3+4 pattern correspond to an intermediary group of carcinomas in contrast to high-grade (high risk) carcinomas with GS 7 and pattern 4+3. Copyright © 2013 Elsevier GmbH. All rights reserved.

  5. Rates of water exsolution and magma ascent inferred from microstructures and chemical analyses of the Tokachi-Ishizawa obsidian lava, Shirataki, northern Hokkaido, Japan

    Science.gov (United States)

    Sano, Kyohei; Wada, Keiji; Sato, Eiichi

    2015-02-01

    Very few quantitative textural data exist for viscous obsidian lava eruptions, and it is still unclear from the mechanical behavior of ascending magmas if outgassing is controlled dominantly by brittle or ductile deformation. In order to obtain insights into how degassing and ascent proceed in such highly viscous magmas, we conducted textural and chemical analyses of the Tokachi-Ishizawa (TI) obsidian lava, in the Shirataki rhyolite volcanic area, northern Hokkaido, Japan, and estimated the water exsolution rate and ascent rate. The storage conditions of the TI lava are estimated from the Rhyolite-MELTS program as T = 840-860 °C and P = 50 MPa using the mineral assemblages and the chemical compositions of plagioclase phenocrysts and glass. To estimate the magma ascent rate, we measured the length, width, and number of oxide microlites using three-dimensional techniques. Textural analysis indicates that the microlite number densities (Nv [number/m3]) of oxide microlites in TI lava samples are 2.1 × 1013 to 1.4 × 1014, which correspond to water exsolution rates of 3.5 × 10- 9 to 1.7 × 10- 8 wt.%/s and ascent rates of 1.7 × 10- 6 to 1.1 × 10- 5 m/s. Together with an estimate of viscosity, the inferred ascent velocities allow us to examine the mechanical behavior of the magma in the conduit. We conclude that the development of permeability leading to outgassing is controlled by ductile deformation rather than brittle fracturing.

  6. Deformation microstructures

    DEFF Research Database (Denmark)

    Hansen, N.; Huang, X.; Hughes, D.A.

    2004-01-01

    Microstructural characterization and modeling has shown that a variety of metals deformed by different thermomechanical processes follows a general path of grain subdivision, by dislocation boundaries and high angle boundaries. This subdivision has been observed to very small structural scales...... of the order of 10 nm, produced by deformation under large sliding loads. Limits to the evolution of microstructural parameters during monotonic loading have been investigated based on a characterization by transmission electron microscopy. Such limits have been observed at an equivalent strain of about 10...

  7. Quantitative approach on SEM images of microstructure of clay soils

    Institute of Scientific and Technical Information of China (English)

    施斌; 李生林; M.Tolkachev

    1995-01-01

    The working principles of Videolab Image Processing System (VIPS), the examining methods of orientation of microstructural units of clay soils and analysing results on SEM images of some typical microstructures of clay soils using the VIPS are introduced.

  8. Dynamic fracture of heterogeneous materials

    Energy Technology Data Exchange (ETDEWEB)

    Stout, M.G.; Liu, C.; Addessio, F.L.; Williams, T.O.; Bennett, J.G.; Haberman, K.S.; Asay, B.W.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to investigate the fundamental aspects of the process of dynamic fracture propagation in heterogeneous materials. The work focused on three important, but poorly understood, aspects of dynamic fracture for materials with a heterogeneous microstructure. These were: the appropriateness of using a single-parameter asymptotic analysis to describe dynamic crack-tip deformation fields, the temperature rises at the tip and on the flanks of a running crack, and the constitutive modeling of damage initiation and accumulation.

  9. Cohesive fracture of elastically heterogeneous materials: An integrative modeling and experimental study

    Science.gov (United States)

    Wang, Neng; Xia, Shuman

    2017-01-01

    A combined modeling and experimental effort is made in this work to examine the cohesive fracture mechanisms of heterogeneous elastic solids. A two-phase laminated composite, which mimics the key microstructural features of many tough engineering and biological materials, is selected as a model material system. Theoretical and finite element analyses with cohesive zone modeling are performed to study the effective fracture resistance of the heterogeneous material associated with unstable crack propagation and arrest. A crack-tip-position controlled algorithm is implemented in the finite element analysis to overcome the inherent instability issues resulting from crack pinning and depinning at local heterogeneities. Systematic parametric studies are carried out to investigate the effects of various material and geometrical parameters, including the modulus mismatch ratio, phase volume fraction, cohesive zone size, and cohesive law shape. Concurrently, a novel stereolithography-based three-dimensional (3D) printing system is developed and used for fabricating heterogeneous test specimens with well-controlled structural and material properties. Fracture testing of the specimens is performed using the tapered double-cantilever beam (TDCB) test method. With optimal material and geometrical parameters, heterogeneous TDCB specimens are shown to exhibit enhanced effective fracture energy and effective fracture toughness than their homogeneous counterparts, which is in good agreement with the modeling predictions. The integrative computational and experimental study presented here provides a fundamental mechanistic understanding of the fracture mechanisms in brittle heterogeneous materials and sheds light on the rational design of tough materials through patterned heterogeneities.

  10. Heterogeneity in recombinant protein production

    DEFF Research Database (Denmark)

    Schalén, Martin; Johanson, Ted; Lundin, Luisa;

    2012-01-01

    contribute to make a population in a fermenter heterogeneous, resulting in cell-to-cell variation in physiological parameters of the microbial culture. Our study aims at investigating how population heterogeneity and recombinant protein production is affected by environmental gradients in bioreactors...... are simulated in small bioreactors and the population heterogeneity can be visualised by analysing single cells with flow cytometry. This can give new insights to cell physiology and recombinant protein production at the industrial scale....

  11. Recrystallization microstructure modelling from superimposed deformed microstructure on microstructure model

    Indian Academy of Sciences (India)

    Prantik Mukhopadhyay

    2009-08-01

    The recovered cold rolled microstructure obtained from orientation image microstructure of Al–4%Mg–0.5%Mn alloy (AA5182 alloy) was superimposed on the grid of cellular automata based microstructure model. The Taylor factors of deformed/cold rolled orientations were considered as the driving force for recrystallization. The local development of recrystallized microstructure and texture were simulated with orientation dependent grain boundary mobility and compared with the experimental results.

  12. Inelastic analysis of the deformation behaviour of internally cooled IN 738 LC turbine blades using the microstructural dependent constitutive equations; Inelastische Analyse des Verformungsverhaltens einer innengekuehlten Gasturbinenschaufel aus dem Werkstoff IN 738 LC unter Verwendung des strukturabhaengigen Werkstoffmodells

    Energy Technology Data Exchange (ETDEWEB)

    Beckmoeller, S.; Schubert, F.; Penkalla, H.J.; Nickel, H.; Breitbach, G.

    1994-06-01

    To enhance the high temperature potential of Superalloys for applications in stationary gas turbines a new concept is required for the prediction of the service life of the blades with an improved method for inelastic analysis. The applicability of the microstructural dependent constitutive equations, which has been developed at the IWE of the KFA, are discussed for a structural analysis of an internally cooled IN 738 LC turbine blade. For the multiaxial confirmation of the model tension-torsion experiments and experiments with precision casted internally cooled model turbine blades were carried out. The blades were exposed to temperature transients and tension stresses to simulate the centrifugal forces. For the mathematical analysis the constitutive equations were implemented into the Finite Elemente Code ABAQUS. A two dimensional mesh was used. At first, the temperature distribution in the blade was calculated based on the temperatures measured at certain points during the experiments. After the temperature distribution was known, it was possible to calculate the stresses and inelastic strains at every point of the model structure. The comparison of the experiments with the calculations, using the constitutive equations of Penkalla, showed a good conformity. For the life time prediction by experiments with short holding times, an elastic analysis could be used. But for experiments with long holding times creep is more dominant and has to be considered. (orig.) [Deutsch] Fuer die optimale Nutzung der Eigenschaften neuer hochwarmfester Superlegierungen reicht die herkoemmliche Auslegung dann nicht mehr aus, wenn ein Bauteil komplizierten Temperatur- und Belastungszyklen ausgesetzt ist. Die Beurteilung des Betriebsverhaltens und der Lebensdauer solcher Bauteile bedarf neuer Konzepte. Ein solches Bauteil ist die innengekuehlte Turbinenschaufel einer modernen stationaeren Gasturbine. Im Rahmen dieser Arbeit wurde die Anwendbarkeit des strukturabhaengigen

  13. Heterogeneous Catalysts

    NARCIS (Netherlands)

    Dakka, J.; Sheldon, R.A.; Sanderson, W.A.

    1997-01-01

    Abstract of GB 2309655 (A) Heterogeneous catalysts comprising one or more metal compounds selected from the group consisting of tin, molybdenum, tungsten, zirconium and selenium compounds deposited on the surface of a silicalite are provided. Preferably Sn(IV) and/or Mo(VI) are employed. The cat

  14. Noninvasive quantification of myocardial perfusion heterogeneity by Markovian analysis in SPECT nuclear imaging; Quantification non invasive de l'heterogeneite de la perfusion du myocarde par analyse markovienne en imageries nucleaire SPECT

    Energy Technology Data Exchange (ETDEWEB)

    Pons, G.

    2011-04-28

    Cardiovascular diseases are the leading cause of mortality worldwide, and third of these deaths are caused by coronary artery disease and rupture of vulnerable atherosclerotic plaques. The heterogeneous alteration of the coronary microcirculation is an early phenomenon associated with many cardiovascular risk factors that can strongly predict the subsequent development of coronary artery disease, and lead to the appearance of myocardial perfusion heterogeneity. Nuclear medicine allows the study of myocardial perfusion in clinical routine through scintigraphic scans performed after injection of a radioactive tracer of coronary blood flow. Analysis of scintigraphic perfusion images currently allows the detection of myocardial ischemia, but the ability of the technique to measure the perfusion heterogeneity in apparently normally perfused areas is unknown. The first part of this thesis focuses on a retrospective clinical study to determine the feasibility of myocardial perfusion heterogeneity quantification measured by Thallium-201 single photon emission computed tomography (SPECT) in diabetic patients compared with healthy subjects. The clinical study has demonstrated the ability of routine thallium-201 SPECT imaging to quantify greater myocardial perfusion heterogeneity in diabetic patients compared with normal subjects. The second part of this thesis tests the hypothesis that the myocardial perfusion heterogeneity could be quantified in small animal SPECT imaging by Thallium-201 and/or Technetium-99m-MIBI in an experimental study using two animal models of diabetes, and is correlated with histological changes. The lack of difference in myocardial perfusion heterogeneity between control and diabetic animals suggests that animal models are poorly suited, or that the technology currently available does not seem satisfactory to obtain similar results as the clinical study. (author)

  15. Analyses on Microstructure of Hypoeutectic Alloy with Different Cooling Rate%亚共晶钎缝组织分析与冷却速率对其形态的影响

    Institute of Scientific and Technical Information of China (English)

    张培磊; 姚舜; 于治水; 丁敏; 徐培全

    2011-01-01

    对熔化后的BCuP-5钎料进行XRD分析,并用BCuP-5钎料真空钎焊紫铜,用扫描电镜对钎缝组织进行分析研究,利用EDX能谱分析钎缝中各相元素含量,探讨钎缝的形成机理.结果表明:钎缝主要是形成了亚共晶组织,领先相为含Ag和P的a(Cu)固溶体,共晶体的组分为!α(Cu)+α(Ag)+Cu3P.BCuP-5钎焊紫铜后形成的钎缝组织形貌与冷却速率有关,冷却速率小时,钎缝为均匀的层片状亚共晶组织;加快冷却速率,钎缝中形成不均匀的亚共晶组织.%The XRD analysis was carried out with the melted filler metal. The copper was brazed with the BCuP-5 filler metal. The microstructure and phase constitution of brazing seam were studied by scanning electron microscope (SEM) and energy dispersive X-ray detector (EDX). The forming mechanism of brazing seam was discussed. The results showed that the structure in the brazing seam was consisted of hypoeutectic alloy. The primary phase is copper solid solution containing a small amount of silver and phosphorus. The eutectic phase was copper solid solution, silver solid solution and Cu3P. The morphology of brazing seam was concerned with cooling rate. In the lower cooling rate, the microstructure morphology of brazing seam was hypoeutectic with uniform layered, dispersedly distributed. In the higher cooling rate, the microstructure morphology of brazing seam was nonuniform hypoeutetic.

  16. Microstructured optical fibers - Fundamentals and applications

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Bjarklev, Anders Overgaard

    2006-01-01

    In recent years optical fibers having a complex microstructure in the transverse plane have attracted much attention from both researchers and industry. Such fibers can either guide light through total internal reflection or the photonic bandgap effect. Among the many unique applications offered...... by these fibers are mode guidance in air, highly flexible dispersion engineering, and the use of very heterogeneous material combinations. In this paper, we review the different types and applications of microstructured optical fibers, with particular emphasis on recent advances in the field....

  17. Quantitative Analysis of Bone Microstructure Using Tomosynthesis

    Science.gov (United States)

    2013-10-01

    Parkinson, I. H. (1996). “ Fractal dimension and architecture of trabecular bone.” J Pathol 178(1): 100-105. Flynn, M. J., McGee, R. and Blechinger, J...microstructure ( fractal dimension, lacunarity, mean intercept length and line fraction deviation) to those derived from microCT (distribution properties...cadavers. Methods of fractal , lacunarity, mean intercept length and line fraction deviation analyses are used to quantify cancellous microstructure

  18. Observation of asphalt binder microstructure with ESEM.

    Science.gov (United States)

    Mikhailenko, P; Kadhim, H; Baaj, H; Tighe, S

    2017-09-01

    The observation of asphalt binder with the environmental scanning electron microscope (ESEM) has shown the potential to observe asphalt binder microstructure and its evolution with binder aging. A procedure for the induction and identification of the microstructure in asphalt binder was established in this study and included sample preparation and observation parameters. A suitable heat-sampling asphalt binder sample preparation method was determined for the test and several stainless steel and Teflon sample moulds developed, finding that stainless steel was the preferable material. The magnification and ESEM settings conducive to observing the 3D microstructure were determined through a number of observations to be 1000×, although other magnifications could be considered. Both straight run binder (PG 58-28) and an air blown oxidised binder were analysed; their structures being compared for their relative size, abundance and other characteristics, showing a clear evolution in the fibril microstructure. The microstructure took longer to appear for the oxidised binder. It was confirmed that the fibril microstructure corresponded to actual characteristics in the asphalt binder. Additionally, a 'bee' micelle structure was found as a transitional structure in ESEM observation. The test methods in this study will be used for more comprehensive analysis of asphalt binder microstructure. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

  19. Disordered hyperuniform heterogeneous materials

    Science.gov (United States)

    Torquato, Salvatore

    2016-10-01

    Disordered hyperuniform many-body systems are distinguishable states of matter that lie between a crystal and liquid: they are like perfect crystals in the way they suppress large-scale density fluctuations and yet are like liquids or glasses in that they are statistically isotropic with no Bragg peaks. These systems play a vital role in a number of fundamental and applied problems: glass formation, jamming, rigidity, photonic and electronic band structure, localization of waves and excitations, self-organization, fluid dynamics, quantum systems, and pure mathematics. Much of what we know theoretically about disordered hyperuniform states of matter involves many-particle systems. In this paper, we derive new rigorous criteria that disordered hyperuniform two-phase heterogeneous materials must obey and explore their consequences. Two-phase heterogeneous media are ubiquitous; examples include composites and porous media, biological media, foams, polymer blends, granular media, cellular solids, and colloids. We begin by obtaining some results that apply to hyperuniform two-phase media in which one phase is a sphere packing in d-dimensional Euclidean space {{{R}}d} . Among other results, we rigorously establish the requirements for packings of spheres of different sizes to be ‘multihyperuniform’. We then consider hyperuniformity for general two-phase media in {{{R}}d} . Here we apply realizability conditions for an autocovariance function and its associated spectral density of a two-phase medium, and then incorporate hyperuniformity as a constraint in order to derive new conditions. We show that some functional forms can immediately be eliminated from consideration and identify other forms that are allowable. Specific examples and counterexamples are described. Contact is made with well-known microstructural models (e.g. overlapping spheres and checkerboards) as well as irregular phase-separation and Turing-type patterns. We also ascertain a family of

  20. Modeling mechanical response of heterogeneous materials

    Science.gov (United States)

    Pal, Siladitya

    Heterogeneous materials are ubiquitous in nature and as synthetic materials. These materials provide unique combination of desirable mechanical properties emerging from its heterogeneities at different length scales. Future structural and technological applications will require the development of advanced light weight materials with superior strength and toughness. Cost effective design of the advanced high performance synthetic materials by tailoring their microstructure is the challenge facing the materials design community. Prior knowledge of structure-property relationships for these materials is imperative for optimal design. Thus, understanding such relationships for heterogeneous materials is of primary interest. Furthermore, computational burden is becoming critical concern in several areas of heterogeneous materials design. Therefore, computationally efficient and accurate predictive tools are highly essential. In the present study, we mainly focus on mechanical behavior of soft cellular materials and tough biological material such as mussel byssus thread. Cellular materials exhibit microstructural heterogeneity by interconnected network of same material phase. However, mussel byssus thread comprises of two distinct material phases. A robust numerical framework is developed to investigate the micromechanisms behind the macroscopic response of both of these materials. Using this framework, effect of microstuctural parameters has been addressed on the stress state of cellular specimens during split Hopkinson pressure bar test. A voronoi tessellation based algorithm has been developed to simulate the cellular microstructure. Micromechanisms (microinertia, microbuckling and microbending) governing macroscopic behavior of cellular solids are investigated thoroughly with respect to various microstructural and loading parameters. To understand the origin of high toughness of mussel byssus thread, a Genetic Algorithm (GA) based optimization framework has been

  1. Microstructures and their lifetimes in acetamide/electrolyte deep eutectics: anion dependence

    Indian Academy of Sciences (India)

    SUMAN DAS; BISWAROOP MUKHERJEE; RANJIT BISWAS

    2017-07-01

    Extensive computer simulations with deep eutectics made of acetamide (CH₃CONH₂) and lithium salts (LiX) have been performed at 303 K and 350 K to identify the solution-phase microstructures in these media and investigate the anion dependence of the size and lifetime distributions of these microstructures. In addition, we explore how the added electrolyte interferes with the natural hydrogen bonded (H-bonded) network structure of liquid acetamide. For this purpose several radial distribution functions have been analysedand visualised. The results reveal that amide–amide H-bond interaction decreases significantly upon the addition of electrolyte, and the interactions of Li⁺ and X⁻ (X⁻ being NO⁻3 , Br⁻ and ClO⁻4 ) with CH₃CONH₂ lead to heterogeneous solution structures. Furthermore, we have obtained the cluster size and lifetime distributions in order to estimate the size of local microstructures and their stability. Both these distributions are analysed by separating the contributions arising from (a)CH₃CONH₂−CH₃CONH₂, (b)Li⁺−CH₃CONH₂ and (c) Li⁺−X⁻ interactions. The size distribution of Li⁺−X⁻ clusters is found to be different from those for the other two. Also, the lifetime distributions show a pronounced anion dependence and suggest cluster stability time up to a fewnanoseconds.

  2. Kvalitative analyser ..

    DEFF Research Database (Denmark)

    Boolsen, Merete Watt

    bogen forklarer de fundamentale trin i forskningsprocessen og applikerer dem på udvalgte kvalitative analyser: indholdsanalyse, Grounded Theory, argumentationsanalyse og diskursanalyse......bogen forklarer de fundamentale trin i forskningsprocessen og applikerer dem på udvalgte kvalitative analyser: indholdsanalyse, Grounded Theory, argumentationsanalyse og diskursanalyse...

  3. Heterogeneity in Preferences and Productivity

    DEFF Research Database (Denmark)

    Gørtz, Mette

    choices of expenditure, household production and leisure for people in and around retirement. The unobserved individual heterogeneity factor is isolated by comparing cross-sectional evidence and panel data estimates of the effects of retirement on consumption and time allocation. Based on cross......-section data, we can identify a difference in consumption due to retirement status, but when the panel nature of the data is exploited, the effect of retirement on consumption is small and insignificant. Moreover, the analyses point at a large positive effect of retirement on household production. Our results......This paper discusses the determinants of the retirement decision and the implications of retirement on economic well-being. The main contribution of the paper is to formulate the role of individual heterogeneity explicitly. We argue that individual heterogeneity in 1) productivity of market work...

  4. Effect of a titanium nitride interlayer on the densification, properties and microstructure of cermets based on alumina and nickel. Part 2: Microstructures

    NARCIS (Netherlands)

    Li, Shujie; Khosrovabadi, Paul Babayan; Kolster, Ben H.

    1992-01-01

    SEM microstructural analyses in conjunction with EDX and TEM microstructural analyses have been conducted with cermets based on nickel and alumina, the latter as such and with a chemical-vapour-deposited titanium nitride layer. It has been proved that there is excellent bonding at both the Al2O3/TiN

  5. Characterization and influence of deformation microstructure heterogeneity on recrystallization

    DEFF Research Database (Denmark)

    Godfrey, A.; Mishin, Oleg V.; Yu, Tianbo

    2015-01-01

    to investigate the early stages of recrystallization in samples deformed to large strains, by direct comparison of electron backscatter diffraction (EBSD) maps of the same area before and after annealing. Methods for estimation of the stored energy of deformation from EBSD data are also surveyed and the problems...... of each for quantification of the local variation in stored energy are discussed, where it is concluded that a method based on the summation of the contributions from individual boundary segments is considered to be the best suited at present for characterization of the local variation in stored energy...

  6. Multi-Scale Material and Technology for Heterogeneous Integration

    NARCIS (Netherlands)

    Poelma, R.H.

    2016-01-01

    This thesis describes a series of experiments and fabrication methods on high-aspect-ratio 3D microstructures for wafer level packaging and 3D heterogeneous system integration (3D-HSI) using novel materials such as carbon nanotubes and thick-film photo-resists. Furthermore, theoretical and experimen

  7. Non-linear waves in heterogeneous elastic rods via homogenization

    KAUST Repository

    Quezada de Luna, Manuel

    2012-03-01

    We consider the propagation of a planar loop on a heterogeneous elastic rod with a periodic microstructure consisting of two alternating homogeneous regions with different material properties. The analysis is carried out using a second-order homogenization theory based on a multiple scale asymptotic expansion. © 2011 Elsevier Ltd. All rights reserved.

  8. Membrane heterogeneity : from lipid domains to curvature effects

    NARCIS (Netherlands)

    Semrau, Stefan

    2009-01-01

    Membrane heterogeneity on the micro- and nanometer scale plays an important role for a large number of biological processes. In parallel to the conception of refined membrane models, new experimental techniques to determine membrane microstructure were developed in recent years. Single molecule fluo

  9. Quantitative Microstructure Characterization of a NMC Electrode

    Energy Technology Data Exchange (ETDEWEB)

    Usseglio Viretta, Francois L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Smith, Kandler A [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-28

    Performance of lithium-ion batteries (LIBs) is strongly influenced by the porous microstructure of their electrodes. In this work, 3D microstructures of calendared and un-calendared positive electrode LiNi1/3Mn1/3Co1/3O2 (NMC) have been investigated in order to extract relevant properties useful for battery modeling. Transport (volume fraction, connectivity, particle size and tortuosity) and electrochemical (specific surface area) properties have been calculated for the pore and the active material. Special attention has been paid to determine the size of the so-called representative volume element (RVE) required to be statistically representative of the heterogeneous medium. Several parameters have been calculated using a panel of different numerical methods in order to compare their results. Besides, the image level of detail has been evaluated (using original criteria based upon edge detection) to assess the overall data quality available for the study.

  10. Microstructured polymer optical fibres

    CERN Document Server

    Large, Maryanne; Barton, Geoff; van Eijkelenborg, Martijn A

    2008-01-01

    Microstructured Polymer Optical Fibres describes the optical properties of microstructured fibres, how they are made and modelled, and outlines some potential applications. These applications include areas where polymer fibres are already used, such as high-data rate transmission for Fibre-to-the Home or within cars, as well as completely new areas such as the photonic bandgap transmission of ""difficult"" wavelengths. Emphasising a conceptual understanding of the underlying physics, Microstructured Polymer Optical Fibres is clearly written, and includes numerous illustrations. It provides an

  11. Biophysical modeling of high field diffusion MRI demonstrates micro-structural aberration in chronic mild stress rat brain.

    Science.gov (United States)

    Khan, Ahmad Raza; Chuhutin, Andrey; Wiborg, Ove; Kroenke, Christopher D; Nyengaard, Jens R; Hansen, Brian; Jespersen, Sune Nørhøj

    2016-11-15

    Depression is one of the leading causes of disability worldwide. Immense heterogeneity in symptoms of depression causes difficulty in diagnosis, and to date, there are no established biomarkers or imaging methods to examine depression. Unpredictable chronic mild stress (CMS) induced anhedonia is considered to be a realistic model of depression in studies of animal subjects. Stereological and neuronal tracing techniques have demonstrated persistent remodeling of microstructure in hippocampus, prefrontal cortex and amygdala of CMS brains. Recent developments in diffusion MRI (d-MRI) analyses, such as neurite density and diffusion kurtosis imaging (DKI), are able to capture microstructural changes and are considered to be robust tools in preclinical and clinical imaging. The present study utilized d-MRI analyzed with a neurite density model and the DKI framework to investigate microstructure in the hippocampus, prefrontal cortex, caudate putamen and amygdala regions of CMS rat brains by comparison to brains from normal controls. To validate findings of CMS induced microstructural alteration, histology was performed to determine neurite, nuclear and astrocyte density. d-MRI based neurite density and tensor-based mean kurtosis (MKT) were significantly higher, while mean diffusivity (MD), extracellular diffusivity (Deff) and intra-neurite diffusivity(DL) were significantly lower in the amygdala of CMS rat brains. Deff was also significantly lower in the hippocampus and caudate putamen in stressed groups. Histological neurite density corroborated the d-MRI findings in the amygdala and reductions in nuclear and astrocyte density further buttressed the d-MRI results. The present study demonstrated that the d-MRI based neurite density and MKT can reveal specific microstructural changes in CMS rat brains and these parameters might have value in clinical diagnosis of depression and for evaluation of treatment efficacy.

  12. P-T path development derived from shearband boudin microstructure

    Science.gov (United States)

    Rodrigues, Benedito C.; Peternell, Mark; Moura, António; Schwindinger, Martin; Pamplona, Jorge

    2016-09-01

    This work focuses on the development of a regional P-T-path from the Malpica-Lamego Ductile Shear Zone, NW Portugal, based on the microstructures of shearband boudins evolved during progressive simple shear. The combination of microstructural analysis, fluid inclusion studies, crystallographic preffered orientation and fractal geometry analyses, allows to link several stages in the internal evolution of the boudin to regional P-T conditions. The boudinage process is initiated under differential stress after the original layer achieved sufficient viscosity contrast relative to the surrounding matrix. Two main transformations occur simultaneously: i) change in the external shape with continuous evolution from tabular rigid body to sigmoidal asymmetric morphology (shearband boudin) and ii) localized dynamic recrystallization in the sharp-tips of the structure (acute edge of shearband boudin), and along the boudin's margin and grain boundaries. Smaller recrystallized grains, particularly in the sharp-tip domains, accommodate most of the external strain, and larger relict grains are preserved in the centre. Dynamic recrystallization under constant strain rates and strain partitioning inside the boudins is indicated by fractal geometry based on grain boundary and grain area analysis. Progressive deformation leads to the generation of structural and textural heterogeneous domains inside the boudins, and is recorded by quartz c-axis orientation analysis and fluid inclusion studies. The last deformation episode shows the final formation of the blunt-tip domain and internal secondary shear planes. The regional P-T path begins with the crystallization of andalusite after an internal shearband boudin dilation event and ends with quartz dynamic recrystallization on boudin tips. The main deformation stage (310/315 Ma) led to reactivation of internal secondary shear zones with sillimanite crystallization.

  13. Continuous media with microstructure

    CERN Document Server

    2010-01-01

    This book discusses the extension of classical continuum models. To the first class addressed belong various thermodynamic models of multicomponent systems, and to the second class belong primarily microstructures created by phase transformations.

  14. Solidification microstructure development

    Indian Academy of Sciences (India)

    G Phanikumar; K Chattopadhyay

    2001-02-01

    In the present article, evolution of microstructure during solidification, as a function of various parameters, is discussed. Macrosegregation is described as being due to insufficient diffusivity of solute in the solid. Pattern formation is discussed in the light of instabilities at the solidification growth front. An overview of the scaling relations for various microstructures is given. Metastable extensions to equilibrium phase diagrams and corrections to equilibrium quantities are described.

  15. Fibonacci Series on Microstructures

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ It is a big challenge for materials scientists to produce highly ordered micro- and nanostructures in a designed pattern with uniform size and shape.By controlling the geometry and the stress upon cooling, CAS researchers coaxed a microstructure to selfassemble into the triangular tessellation and Fibonacci number patterns on its surface. Their work ‘Triangular and Fibonacci number patterns driven by stress on core/shell microstructures' was published on the August 5 issue of Science.

  16. Simulation and visualization of recrystallization microstructure after solution treatment

    Institute of Scientific and Technical Information of China (English)

    LI Ping; XUE Ke-min

    2005-01-01

    Simulation models for heterogeneous and simultaneous nucleation and random growth of nuclei were developed in terms of the mechanism of recrystallization and Monte Carlo stochastic simulation method.Combining deterministic simulation with stochastic simulation,the simulation and visualization of the recrystallization microstructure of Ti-15-3 alloy after hot compression deformation and solution treatment were realized.Comparison of the simulated results with the experimental ones suggests that the size and distribution of the simulated recrystallized grains agree well with the actual ones.This proves that the obtained statistic equivalent microstructure models are effective.This study is helpful for determining reasonable hot forming process and improving the forming quality.

  17. Microstructural design of fiber composites

    Science.gov (United States)

    Chou, Tsu-Wei

    The optimum performance design of composite microstructures is discussed. The forces driving progress in fiber composites are examined, and recent developments in the mechanics of laminated composites are surveyed, emphasizing thick laminates, hygrothermal effects, and thermal transient effects. The strength of continuous-fiber composites is discussed, presenting analyses of local load redistribution due to fiber breakages and treatments of statistical tensile strength theories. Modes of failure of laminated composites are examined. Elastic, physical, and viscoelastic properties as well as the strength and fracture behavior of short-fiber composites are studied, and it is shown how the performance of composites can be controlled by selecting material systems and their geometric distributions. 2D textile structural composites based on woven, knitted, and braided preforms are considered, and techniques for analyzing and modeling the thermomechanical behavior of 2D textile composites are presented. Recent developments in the processing of 3D textile preforms are introduced and the processing-microstructure relationship is demonstrated. Finite elastic deformation of flexible composites is addressed.

  18. Microstructure and creep characteristics of dissimilar T91/TP316H martensitic/austenitic welded joint with Ni-based weld metal

    Energy Technology Data Exchange (ETDEWEB)

    Falat, Ladislav, E-mail: lfalat@imr.saske.sk [Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 040 01 Kosice (Slovakia); Svoboda, Milan [Institute of Physics of Materials, Academy of Sciences of Czech Republic, Zizkova 22, 616 62 Brno (Czech Republic); Vyrostkova, Anna; Petryshynets, Ivan; Sopko, Martin [Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 040 01 Kosice (Slovakia)

    2012-10-15

    This paper deals with characterization of microstructure and creep behavior of dissimilar weldment between the tempered martensitic steel T91 and the non-stabilized austenitic steel TP316H with Ni-based weld metal (Ni WM). Microstructure analyses were performed using light microscopy, scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy. The martensitic part of the welded joint exhibited a wide heat-affected zone (HAZ) with typical microstructural gradient from its coarse-grained to the fine-grained/intercritical region. In contrast, the HAZ of austenitic steel was limited to only a narrow region with coarsened polygonal grains. The microstructure of Ni WM was found to be very heterogeneous with respect to the size, morphology and distribution of grain boundaries and MC-type precipitates as a result of strong weld metal dilution effects and fast non-equilibrium solidification. Cross-weld creep tests were carried out in a temperature range from 600 to 650 Degree-Sign C at applied stresses from 60 to 140 MPa. The obtained values of apparent stress exponents and creep activation energies indicate thermally activated dislocation glide to be the governing creep deformation mechanism within the range of used testing conditions. The creep samples ruptured in the T91 intercritical HAZ region by the 'type IV cracking' failure mode and the creep fracture mechanism was identified to be the intergranular dimple tearing by microvoid coalescence at grain boundaries. The TEM observations revealed pronounced microstructural differences between the critical HAZ region and the T91 base material before as well as after the creep exposure. - Highlights: Black-Right-Pointing-Pointer Phase transformations affect the microstructures of T91 and TP316H HAZ regions. Black-Right-Pointing-Pointer High weld metal dilution results in heterogeneous microstructure with MC carbides. Black-Right-Pointing-Pointer Creep behavior of the studied weldment is

  19. Quantitative Analysis of Three-dimensional Microstructure of Li-ion Battery Electrodes

    Science.gov (United States)

    Liu, Zhao

    carbonaceous phases in the electrodes, which strongly correlate with LIB transport properties, a three-phase FIB-SEM method was developed where silicone resin was infiltrated into electrode pores, providing good image contrast with the carbon particles. Structural parameters including phase connectivity and tortuosity are quantified for commercial LiCoO 2 and laboratory-made LiFePO4 electrodes to help understand the transport process in these electrodes. For LiCoO2 electrodes, a heterogeneous tortuosity distribution observed in the electrolyte phase may result in inhomogeneous charge/discharge states, and consequently cause battery degradation. For LiFePO4 electrodes, highly percolated and less tortuous carbon found in a templated electrode explain its better high-C-rate performance. Finally, laboratory-made LiMn2O4 electrodes were electrochemically cycled with different operation parameters, including cycle number, temperature, and operating voltage. Quantitative analyses on 3D TXM data sets indicate particle fracture, mainly due to tetragonal to cubic phase transformations induced by the Jahn-Teller effect, resulting in electrode degradation. Moreover, high temperature operation is found to enhance active material dissolution and can also accelerate cell degradation. This ex-situ method, which combines electrochemical cycling and statistical analysis, proved to be an effective approach to provide insight for the interpretation of complex mechanical and electrochemical interactions within the electrodes.

  20. Microstructuring of glasses

    CERN Document Server

    Hülsenberg, Dagmar; Bismarck, Alexander

    2008-01-01

    As microstructured glass becomes increasingly important for microsystems technology, the main application fields include micro-fluidic systems, micro-analysis systems, sensors, micro-actuators and implants. And, because glass has quite distinct properties from silicon, PMMA and metals, applications exist where only glass devices meet the requirements. The main advantages of glass derive from its amorphous nature, the precondition for its - theoretically - direction-independent geometric structurability. Microstructuring of Glasses deals with the amorphous state, various glass compositions and their properties, the interactions between glasses and the electromagnetic waves used to modify it. Also treated in detail are methods for influencing the geometrical microstructure of glasses by mechanical, chemical, thermal, optical, and electrical treatment, and the methods and equipment required to produce actual microdevices.

  1. Optics of dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2002-01-01

    microstructures, will be presented in the part I of this thesis consisting of the chapters 2-5. An introductions is given in chapter 2. In part I three methods are presented for calculating spontaneous and classical emission from sources in dielectric microstructures. The first method presented in chapter 3...... near fields and far fields generated by a dipole emitter in finite-sized dielectric disks. A collection of results obtained within the second topic, planar photonic crystal waveguides, are presented in part II of this thesis consisting of the chapters 6-10. Chapter 6 contains a further introduction...

  2. Emissivity of microstructured silicon.

    Science.gov (United States)

    Maloney, Patrick G; Smith, Peter; King, Vernon; Billman, Curtis; Winkler, Mark; Mazur, Eric

    2010-03-01

    Infrared transmittance and hemispherical-directional reflectance data from 2.5 to 25 microm on microstructured silicon surfaces have been measured, and spectral emissivity has been calculated for this wavelength range. Hemispherical-total emissivity is calculated for the samples and found to be 0.84 before a measurement-induced annealing and 0.65 after the measurement for the sulfur-doped sample. Secondary samples lack a measurement-induced anneal, and reasons for this discrepancy are presented. Emissivity numbers are plotted and compared with a silicon substrate, and Aeroglaze Z306 black paint. Use of microstructured silicon as a blackbody or microbolometer surface is modeled and presented, respectively.

  3. Phase-field simulations of nuclei and early stage solidification microstructures

    Science.gov (United States)

    Nestler, B.; Selzer, M.; Danilov, D.

    2009-11-01

    To investigate the local properties of heterogeneous nuclei on substrates, a phase-field model is extended to incorporate volume constraints and a third order line tension in the gradient free energy density formulation. The new model is applied to sessile drop simulations of Cu nuclei on Ni substrates to precisely analyse 3D equilibrium shapes and diffusion processes across the phase boundaries. In particular, the formalism with higher order potentials is used to investigate the length-scale dependent effect of the line tension on Young's force balance at triple lines in 3D. The employment of parallel and adaptive simulation techniques is essential for three-dimensional numerical computations. Early stage solidification microstructures of cubic Ni crystals are simulated by scale-bridging molecular dynamics (MD) and phase-field (PF) simulations. The domain of the PF computations is initialized by transferring MD data of the atomic positions and of the shape of the nuclei. The combined approach can be used to study the responses of microstructures upon nucleation.

  4. Phase-field simulations of nuclei and early stage solidification microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Nestler, B; Selzer, M; Danilov, D [Institute of Materials and Processes (IMP), Karlsruhe University of Applied Sciences, Moltkestrasse 30, 76133 Karlsruhe (Germany)

    2009-11-18

    To investigate the local properties of heterogeneous nuclei on substrates, a phase-field model is extended to incorporate volume constraints and a third order line tension in the gradient free energy density formulation. The new model is applied to sessile drop simulations of Cu nuclei on Ni substrates to precisely analyse 3D equilibrium shapes and diffusion processes across the phase boundaries. In particular, the formalism with higher order potentials is used to investigate the length-scale dependent effect of the line tension on Young's force balance at triple lines in 3D. The employment of parallel and adaptive simulation techniques is essential for three-dimensional numerical computations. Early stage solidification microstructures of cubic Ni crystals are simulated by scale-bridging molecular dynamics (MD) and phase-field (PF) simulations. The domain of the PF computations is initialized by transferring MD data of the atomic positions and of the shape of the nuclei. The combined approach can be used to study the responses of microstructures upon nucleation.

  5. Computing effective properties of random heterogeneous materials on heterogeneous parallel processors

    Science.gov (United States)

    Leidi, Tiziano; Scocchi, Giulio; Grossi, Loris; Pusterla, Simone; D'Angelo, Claudio; Thiran, Jean-Philippe; Ortona, Alberto

    2012-11-01

    In recent decades, finite element (FE) techniques have been extensively used for predicting effective properties of random heterogeneous materials. In the case of very complex microstructures, the choice of numerical methods for the solution of this problem can offer some advantages over classical analytical approaches, and it allows the use of digital images obtained from real material samples (e.g., using computed tomography). On the other hand, having a large number of elements is often necessary for properly describing complex microstructures, ultimately leading to extremely time-consuming computations and high memory requirements. With the final objective of reducing these limitations, we improved an existing freely available FE code for the computation of effective conductivity (electrical and thermal) of microstructure digital models. To allow execution on hardware combining multi-core CPUs and a GPU, we first translated the original algorithm from Fortran to C, and we subdivided it into software components. Then, we enhanced the C version of the algorithm for parallel processing with heterogeneous processors. With the goal of maximizing the obtained performances and limiting resource consumption, we utilized a software architecture based on stream processing, event-driven scheduling, and dynamic load balancing. The parallel processing version of the algorithm has been validated using a simple microstructure consisting of a single sphere located at the centre of a cubic box, yielding consistent results. Finally, the code was used for the calculation of the effective thermal conductivity of a digital model of a real sample (a ceramic foam obtained using X-ray computed tomography). On a computer equipped with dual hexa-core Intel Xeon X5670 processors and an NVIDIA Tesla C2050, the parallel application version features near to linear speed-up progression when using only the CPU cores. It executes more than 20 times faster when additionally using the GPU.

  6. Microstructure characterization of Cu processed by compression with oscillatory torsion

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, K., E-mail: kinga.rodak@polsl.pl [Institute of Materials Science, Silesian University of Technology, Krasińskiego 8, 40-019 Katowice (Poland); Pawlicki, J., E-mail: jacek.pawlicki@polsl.pl [Department of Automotive Vehicle Construction, Silesian University of Technology, Krasińskiego 8, 40–019 Katowice (Poland)

    2014-08-15

    High purity Cu (99.9%) was subjected to severe plastic deformation up to a total effective strain ε{sub ft} = 130 through compression with the oscillatory torsion method at room temperature. This method produces an ultrafine grain microstructure. The microstructure evolution was investigated with respect to the value of the total effective strain using a scanning electron microscope with an electron-backscattered diffraction technique and a scanning transmission electron microscope. The results of the structural analyses show that increasing ε{sub ft} from 2 to 50 causes progress in the grain refinement. A quantitative study of the microstructure parameters, such as fraction of high angle boundaries, grain and subgrain diameter, and the area fraction of grains up to 1 μm, shows that deformation at ε{sub ft} = 45 guaranteed the best conditions for refining the microstructure of Cu. Using high values of ε{sub ft} in the range 60 to 130 restricts grain refinement because intensive recovery begins to dominate in the microstructure. - Highlights: • Cu was processed by SPD metodto an effective strain 130. • The microstructure evolution has been investigated. • The method allows to produce an ultrafine grain microstructure.

  7. Heterogeneous network architectures

    DEFF Research Database (Denmark)

    Christiansen, Henrik Lehrmann

    2006-01-01

    Future networks will be heterogeneous! Due to the sheer size of networks (e.g., the Internet) upgrades cannot be instantaneous and thus heterogeneity appears. This means that instead of trying to find the olution, networks hould be designed as being heterogeneous. One of the key equirements here...... is flexibility. This thesis investigates such heterogeneous network architectures and how to make them flexible. A survey of algorithms for network design is presented, and it is described how using heuristics can increase the speed. A hierarchical, MPLS based network architecture is described...... and it is discussed that it is advantageous to heterogeneous networks and illustrated by a number of examples. Modeling and simulation is a well-known way of doing performance evaluation. An approach to event-driven simulation of communication networks is presented and mixed complexity modeling, which can simplify...

  8. The role of deformation microstructure in recovery and recrystallization of heavily strained metals

    DEFF Research Database (Denmark)

    Hansen, Niels

    2012-01-01

    Metals deformed to high and ultrahigh strains are characterized by a nanoscale microstructure, a large fraction of high angle boundaries and a high dislocation density. Another characteristic of such a microstructure is a large stored energy that combines elastic energy due to dislocations...... and boundary energy. Parameters of the deformed microstructure significantly affect annealing processes such as recovery and recrystallization. For example, the recovery rate can be significantly increased after high strain deformation and restoration may occur as either discontinuous recrystallization...... of recovery on subsequent restoration processes is discussed along with the effect of heterogeneities both on the local scale and on the sample scale. © (2012) Trans Tech Publications, Switzerland....

  9. Microstructural characterization of the -TiAl alloy samples fabricated by direct laser fabrication rapid prototype technique

    Indian Academy of Sciences (India)

    D Srivastava

    2002-12-01

    A direct laser fabrication technique (DLF) has been used to fabricate near net shape samples of a -TiAl alloy using gas atomized Ti48A148Mn2Nb2 alloy powder as a feed stock material. The microstructures of these Ti48Al48Mn2Nb2 laser treated samples have been characterized using optical, scanning (SEM) and transmission electron microscopy (TEM), both immediately after laser fabrication and after heat treatments. The microstructural studies have shown that the microstructure is heterogeneous in nature and extremely fine in comparison with the conventionally processed material. The process parameters such as laser power and laser scanning speed greatly influence the morphology and the microstructure of the laser treated samples. Heat treatments for a number of process conditions have been carried out to examine the stability of the microstructure which remains stable up to 973 K and rapid grain coarsening occurs at 1273 K. A fully recrystallized and uniform microstructure is obtained after annealing at 1073 K for 24 h and compositional heterogeneity present in the laser-fabricated samples is eliminated. Annealing in the phase field followed by air cooling and annealing in (2 + ) phase region gives rise to a homogeneous and uniform microstructure. However, the microstructure is much coarser than the microstructure of the DLF samples.

  10. Desalination shocks in microstructures

    CERN Document Server

    Mani, Ali

    2011-01-01

    Salt transport in bulk electrolytes is limited by diffusion and convection, but in microstructures with charged surfaces (e.g. microfluidic devices, porous media, soils, or biological tissues) surface conduction and electro-osmotic flow also contribute to ionic fluxes. For small applied voltages, these effects lead to well known linear electrokinetic phenomena. In this paper, we predict some surprising nonlinear dynamics that can result from the competition between bulk and interfacial transport at higher voltages. When counter-ions are selectively removed by a membrane or electrode, a "desalination shock" can propagate through the microstructure, leaving in its wake an ultrapure solution, nearly devoid of co-ions and colloidal impurities. We elucidate the basic physics of desalination shocks and develop a mathematical theory of their existence, structure, and stability, allowing for slow variations in surface charge or channel geometry. Via asymptotic approximations and similarity solutions, we show that des...

  11. Superhydrophobicity from microstructured surface

    Institute of Scientific and Technical Information of China (English)

    ZHENG Lijun; WU Xuedong; LOU Zeng; WU Dan

    2004-01-01

    Superhydrophobicity is referred to the wettability of a solid surface which has a water apparent contact angle greater than 150°. It has attracted great interest in both fundamental researches and practical applications. This paper discusses two models: Wenzel model and Cassie model, to describe the superhydrophobic states of surface. The effectsof surface morphology and microstructure on superhydrophobicity are discussed, and the internal relationship between Wenzel and Cassie states is presented. These two su perhydrophobic states can coexist and they present different properties on contact angle hysteresis. It is reported that the irreversible transition can be realized from Cassie state to Wenzel state under some certain conditions. This paper also gives a review of recent progresses in the strategies of fabricating superhydrophobic surfaces by designing microstructured or microtextured surfaces. Finally, the fundamental research and applications of superhydrophobic surfaces are prospected.

  12. The leak microstructure

    Indian Academy of Sciences (India)

    M Lombardi; C Baiocchi; A Battistella; G Balbinot; H Huo-Ja Guoxiang; F S Lombardi

    2001-07-01

    The capabilities of a new microstructure, anode point based, for the detection of gas ionizing radiations are presented. For every single detected ionizing radiation it gives a pair of ‘induced’ charges (anodic and cathodic) of the same amount (pulses of the same amplitudes), of opposite sign, with the same collection time and essentially in time coincidence, that are proportional to the primary ionization collected. Each pulse of a pair gives the same energy and timing information, thus one can be used for these information and the other for the position. The complete lack of insulating materials in the active volume of this microstructure avoids problems of charging-up and makes stable and repeatable its behavior. It is possible to observe primary avalanches with a size of more than 2.5 × 107 electrons (4 pC), which give current pulses with a peak of more than 0.26 mA on 100 Ohm and about 30 ns duration, with 5.9 KeV X-rays of 55Fe working in proportional region in 760 Torr of isobutane gas. Single electrons emitted by a heated filament ( < 1~ eV) can also be detected in 760 Torr of isobutane; with an estimated gas gain of 1.2 × 106 and a counting rate up to 800 Kpulses/sec per single microstructure. Some new features and three different types of sensitive-position two-dimensional read-out detectors based on these microstructures, which are in developmental stage, are presented.

  13. Morphing Carbon Nanotube Microstructures

    Science.gov (United States)

    2015-02-20

    d) vertical twisting actuator. 2 independently from the microstructure geometry, representing a versatile principle for design and manufacturing...CNT yarn, causing the 2 composite to contract its length due to the mechanical anisotropy introduced by the twist of the CNTs about the yarn axis... Oliver , and Tom Serbowicz for contributions to the design and fabrication of the force control and imaging systems. Microfabrication was performed

  14. Microstructure and Properties of Activated Slag Cement

    Institute of Scientific and Technical Information of China (English)

    GUO Jun-cai; XIANG Xin; XU Yan-wu

    2004-01-01

    Activation of theslag cement was performed using a composite activator. Experimental resultsshow that the performance of the cement is remarkably improved. The fineness and specific surface area of the ce-ment are increased by 23.7% and 1.4% , and 3d flexural strength and compressive strength are enhanced by20.9% and 22.9% , respectively. Microstructure and phase composition of the hydrates were analysed by X- raydiffraction(XRD) and scanning electron microscopy(SEM). The results indicate that Ca( OH)2 in the hydratesdecrease obviously. The morphology of the other hydrates appears to be flocculent, with a dense structure. The im-provements of the properties is related to the microstructural changes.

  15. Heterogeneous cellular networks

    CERN Document Server

    Hu, Rose Qingyang

    2013-01-01

    A timely publication providing coverage of radio resource management, mobility management and standardization in heterogeneous cellular networks The topic of heterogeneous cellular networks has gained momentum in industry and the research community, attracting the attention of standardization bodies such as 3GPP LTE and IEEE 802.16j, whose objectives are looking into increasing the capacity and coverage of the cellular networks. This book focuses on recent progresses,  covering the related topics including scenarios of heterogeneous network deployment, interference management i

  16. Problems and Solutions in Heterogeneous Cooperative Learning

    Institute of Scientific and Technical Information of China (English)

    易彦池

    2007-01-01

    Heterogeneous cooperative learning,as the best kind of cooperative learning,is quite often adopted to make utmost use of the human power in second language learning. On the other hand ,some problems existing in it make it far from satisfactory. In this thesis ,the writer will analyse the problems and put forward some solutions to perfect HCL.

  17. Heterogeneity of link weight and the evolution of cooperation

    CERN Document Server

    Iwata, M

    2015-01-01

    We consider the situation where individuals in a weighted one- or two-dimensional lattice play the prisoner's dilemma game. We investigate the effect of the "heterogeneity of link weight" on the evolution of cooperation. Our analyses show that heterogeneity of link weight can facilitate cooperation. Furthermore, we identify the two key mechanisms by which link-weight heterogeneity promotes the evolution of cooperation and find the conditions under which the mechanisms can work through evolutionary dynamics.

  18. Teaching Heterogeneous Classes.

    Science.gov (United States)

    Millrood, Radislav

    2002-01-01

    Discusses an approach to teaching heterogeneous English-as-a-Second/Foreign-Language classes. Draws on classroom research data to describe the features of a success-building lesson context. (Author/VWL)

  19. Effects of the hydraulic conductivity microstructure on macrodispersivity

    Science.gov (United States)

    Di Dato, Mariaines; de Barros, Felipe P. J.; Fiori, Aldo; Bellin, Alberto

    2016-09-01

    Heterogeneity of the hydraulic properties is one of the main causes of the seemingly random distribution of solute concentration observed in contaminated aquifers, with macrodispersivity providing a global measure of spreading. Earlier studies on transport of solutes in heterogeneous formations, either theoretical or numerical, expressed dispersivity as a function of the geostatistical properties of the hydraulic conductivity K. In most cases, K follows a second-order statistical characterization, which may not be adequate when heterogeneity is high. In this work, we adopt the Multi-Indicator Model-Self Consistent Approach (MIMSCA) to compute the longitudinal and transverse macrodispersivity. This methodology enables to model the K field by using geological inclusions of different shapes and orientation (defined here as the microstructure), while replicating the heterogeneous macrostructure obtained by the second-order statistics. The above scheme attempts to reproduce the effect on macrodispersion of different distribution and orientation of local facies, and for instance it may represent the orientation and spatial features of the layers that are often observed in aquifers. The relevant impact of the microstructure on effective conductivity, longitudinal and transverse macrodispersivities is analyzed and discussed, for both binary and lognormally distributed K fields.

  20. Computational Mechanics for Heterogeneous Materials

    Energy Technology Data Exchange (ETDEWEB)

    Lechman, Jeremy B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Baczewski, Andrew David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bond, Stephen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Erikson, William W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lehoucq, Richard B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mondy, Lisa Ann [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Noble, David R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pierce, Flint [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Roberts, Christine [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); van Swol, Frank B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Yarrington, Cole [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2013-11-01

    The subject of this work is the development of models for the numerical simulation of matter, momentum, and energy balance in heterogeneous materials. These are materials that consist of multiple phases or species or that are structured on some (perhaps many) scale(s). By computational mechanics we mean to refer generally to the standard type of modeling that is done at the level of macroscopic balance laws (mass, momentum, energy). We will refer to the flow or flux of these quantities in a generalized sense as transport. At issue here are the forms of the governing equations in these complex materials which are potentially strongly inhomogeneous below some correlation length scale and are yet homogeneous on larger length scales. The question then becomes one of how to model this behavior and what are the proper multi-scale equations to capture the transport mechanisms across scales. To address this we look to the area of generalized stochastic process that underlie the transport processes in homogeneous materials. The archetypal example being the relationship between a random walk or Brownian motion stochastic processes and the associated Fokker-Planck or diffusion equation. Here we are interested in how this classical setting changes when inhomogeneities or correlations in structure are introduced into the problem. Aspects of non-classical behavior need to be addressed, such as non-Fickian behavior of the mean-squared-displacement (MSD) and non-Gaussian behavior of the underlying probability distribution of jumps. We present an experimental technique and apparatus built to investigate some of these issues. We also discuss diffusive processes in inhomogeneous systems, and the role of the chemical potential in diffusion of hard spheres is considered. Also, the relevance to liquid metal solutions is considered. Finally we present an example of how inhomogeneities in material microstructure introduce fluctuations at the meso-scale for a thermal conduction problem

  1. Subgroup effects despite homogeneous heterogeneity test results

    Directory of Open Access Journals (Sweden)

    Lubsen Jacobus

    2010-05-01

    Full Text Available Abstract Background Statistical tests of heterogeneity are very popular in meta-analyses, as heterogeneity might indicate subgroup effects. Lack of demonstrable statistical heterogeneity, however, might obscure clinical heterogeneity, meaning clinically relevant subgroup effects. Methods A qualitative, visual method to explore the potential for subgroup effects was provided by a modification of the forest plot, i.e., adding a vertical axis indicating the proportion of a subgroup variable in the individual trials. Such a plot was used to assess the potential for clinically relevant subgroup effects and was illustrated by a clinical example on the effects of antibiotics in children with acute otitis media. Results Statistical tests did not indicate heterogeneity in the meta-analysis on the effects of amoxicillin on acute otitis media (Q = 3.29, p = 0.51; I2 = 0%; T2 = 0. Nevertheless, in a modified forest plot, in which the individual trials were ordered by the proportion of children with bilateral otitis, a clear relation between bilaterality and treatment effects was observed (which was also found in an individual patient data meta-analysis of the included trials: p-value for interaction 0.021. Conclusions A modification of the forest plot, by including an additional (vertical axis indicating the proportion of a certain subgroup variable, is a qualitative, visual, and easy-to-interpret method to explore potential subgroup effects in studies included in meta-analyses.

  2. Microstructure analysis of laboratory and in-situ compacted silts

    Directory of Open Access Journals (Sweden)

    Russo Giacomo

    2016-01-01

    Full Text Available The paper presents and discusses some results of an experimental research aimed at analysing the influence of compaction variables (w and energy and method on the resulting microstructure of a compacted silty soil. In particular, the experimental data here discussed allow to compare the microstructure induced by different dynamic compaction techniques, comparing that characterising specimens obtained by two laboratory methods (Proctor standard and Harvard and that of samples compacted in-situ during the construction of an embankment built for river regimentation purposes. Both undisturbed and disturbed samples have been retrieved from the embankment, the latter one with the purpose of collecting the soil subsequently used for laboratory compaction. Microstructural analyses (SEM, MIP performed on laboratory and in-situ compacted samples evidenced a substantial similarity of the texture induced by the various compaction techniques, highlighting that laboratory compaction is suitable to provide soil samples representative of earth in-situ compacted soil.

  3. VLSI electronics microstructure science

    CERN Document Server

    1981-01-01

    VLSI Electronics: Microstructure Science, Volume 3 evaluates trends for the future of very large scale integration (VLSI) electronics and the scientific base that supports its development.This book discusses the impact of VLSI on computer architectures; VLSI design and design aid requirements; and design, fabrication, and performance of CCD imagers. The approaches, potential, and progress of ultra-high-speed GaAs VLSI; computer modeling of MOSFETs; and numerical physics of micron-length and submicron-length semiconductor devices are also elaborated. This text likewise covers the optical linewi

  4. VLSI electronics microstructure science

    CERN Document Server

    1982-01-01

    VLSI Electronics: Microstructure Science, Volume 4 reviews trends for the future of very large scale integration (VLSI) electronics and the scientific base that supports its development.This book discusses the silicon-on-insulator for VLSI and VHSIC, X-ray lithography, and transient response of electron transport in GaAs using the Monte Carlo method. The technology and manufacturing of high-density magnetic-bubble memories, metallic superlattices, challenge of education for VLSI, and impact of VLSI on medical signal processing are also elaborated. This text likewise covers the impact of VLSI t

  5. Microstructure and anisotropic swelling behaviour of compacted bentonite/sand mixture

    Directory of Open Access Journals (Sweden)

    Simona Saba

    2014-04-01

    Full Text Available Pre-compacted elements (disks, torus of bentonite/sand mixture are candidate materials for sealing plugs of radioactive waste disposal. Choice of this material is mainly based on its swelling capacity allowing all gaps in the system to be sealed, and on its low permeability. When emplaced in the gallery, these elements will start to absorb water from the host rock and swell. Thereby, a swelling pressure will develop in the radial direction against the host rock and in the axial direction against the support structure. In this work, the swelling pressure of a small scale compacted disk of bentonite and sand was experimentally studied in both radial and axial directions. Different swelling kinetics were identified for different dry densities and along different directions. As a rule, the swelling pressure starts increasing quickly, reaches a peak value, decreases a little and finally stabilises. For some dry densities, higher peaks were observed in the radial direction than in the axial direction. The presence of peaks is related to the microstructure change and to the collapse of macro-pores. In parallel to the mechanical tests, microstructure investigation at the sample scale was conducted using microfocus X-ray computed tomography (μCT. Image observation showed a denser structure in the centre and a looser one in the border, which was also confirmed by image analysis. This structure heterogeneity in the radial direction and the occurrence of macro-pores close to the radial boundary of the sample can explain the large peaks observed in the radial swelling pressure evolution. Another interesting result is the higher anisotropy found at lower bentonite dry densities, which was also analysed by means of μCT observation of a sample at low bentonite dry density after the end of test. It was found that the macro-pores, especially those between sand grains, were not filled by swelled bentonite, which preserved the anisotropic microstructure caused by

  6. Relationships among the Microstructure, Mechanical Properties, and Fatigue Behavior in Thin Ti6Al4V

    Directory of Open Access Journals (Sweden)

    Y. Fan

    2016-01-01

    Full Text Available The microstructures of Ti6Al4V are complex and strongly affect its mechanical properties and fatigue behavior. This paper investigates the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets, with the aim of reviewing the effects of microstructure on fatigue properties where suboptimal microstructures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding. Samples of Ti6Al4V sheet were subjected to a range of heat treatments, including annealing and water quenching from temperatures ranging from 650°C to 1050°C. Micrographs of these samples were inspected for microstructure, and hardness, 0.2% proof stress, elongation, and fracture strength were measured and attributed back to microstructure. Fractography was used to support the findings from microstructure and mechanical analyses. The strength ranking from high to low for the microstructures of thin Ti6Al4V sheets observed in this study is as follows: acicular α′ martensite, Widmanstätten, bimodal, and equiaxed microstructure. The fatigue strength ranking from high to low is as follows: equiaxed, bimodal, Widmanstätten, and acicular α′ martensite microstructure.

  7. Exsolution microstructures in ultrahigh-pressure rocks:Progress, controversies and challenges

    Institute of Scientific and Technical Information of China (English)

    LIU Liang; YANG JiaXi; ZHANG JunFeng; CHEN DanLing; WANG Chao; YANG WenQiang

    2009-01-01

    Exsolution microstructures in minerals of rocks from orogenic belts played an important role in recognition of ultrahigh-pressure (UHP) metamorphism in their host rocks by defining the subduction depth and improving our understanding of the dynamics during the subduction and exhumation of UHP rocks. However, it is a challenging scientific topic to distinguish the 'exsolution microstructures' from the 'non-exsolution microstructures' and decipher their geological implications. This paper describes the subtle differences between the 'exsolution microstructures' and the 'non-exsolution microstructures' and summarizes the progress in studies of exolution microstructures from UHP rocks and mantle rocks of ultra-deep origin. We emphasize distinguishing the 'exsolution microstructures' from the'non-exsolution microstructures' based on their geometric topotaxy and chemistry. In order to decipher correctly the exsolution microstructures, it is crucial to understand the changes of chemistry and habits of host minerals with pressure and temperature. Therefore, it is important to combine observations of exsolution microstructure in natural rocks with experimental results at high pressure and temperature and results of micro-scale analyses. Such studies will improve our understanding of the UHP metamorphism and cast new lights on solid geoscience issues such as deep subduction of continental crusts and crust-mantle interactions.

  8. Cell behaviour on chemically microstructured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Magnani, Agnese; Priamo, Alfredo; Pasqui, Daniela; Barbucci, Rolando

    2003-03-03

    Micropatterned surfaces with different chemical topographies were synthesised in order to investigate the influence of surface chemistry and topography on cell behaviour. The microstructured materials were synthesised by photoimmobilising natural Hyaluronan (Hyal) and its sulphated derivative (HyalS), both adequately functionalised with a photorective moiety, on glass substrates. Four different grating patterns (10, 25, 50 and 100 {mu}m) were used to pattern the hyaluronan. The micropatterned samples were analysed by Secondary Ions Mass Spectrometry, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy to investigate the chemistry and the topography of the surfaces. The spectroscopic and microscopic analysis of the microstructured surfaces revealed that the photoimmobilisation process was successful, demonstrating that the photomask patterns were well reproduced on the sample surface. The influence of chemical topographies on the cell behaviour was then analysed. Human and 3T3 fibroblasts, bovine aortic and human (HGTFN line) endothelial cells were used and their behaviour on the micropatterned surfaces was analysed in terms of adhesion, proliferation, locomotion and orientation. Both chemical and topographical controls were found to be important for cell guidance. By decreasing the stripe dimensions, a more fusiform shape of cell was observed. At the same time, the cell locomotion and orientation parallel to the structure increased. However, differences in cell behaviour were detected according to both cell type and micropattern dimensions.

  9. The Microstructure of Isichazamazwi SesiNdebele

    Directory of Open Access Journals (Sweden)

    Mandlenkosi Maphosa

    2011-10-01

    Full Text Available Abstract: This article analyses the microstructure of Isichazamazwi SesiNdebele. The analysis takes place on two levels: the level of availability of information and the level of accessibility of the available information to dictionary users. Data derived from two outreach exercises carried out to ascertain users' perspectives on the dictionary and their competence in using the dictionary is also scrutinised while the notion of user-friendliness and the general principles of dictionary-making form the framework within which the analysis is done.

  10. Calcium Deposits in the Crayfish, Cherax quadricarinatus: Microstructure Versus Elemental Distribution.

    Science.gov (United States)

    Luquet, Gilles; Dauphin, Yannicke; Percot, Aline; Salomé, Murielle; Ziegler, Andreas; Fernández, Maria S; Arias, José L

    2016-02-01

    The crayfish Cherax quadricarinatus stores calcium ions, easily mobilizable after molting, for calcifying parts of the new exoskeleton. They are chiefly stored as amorphous calcium carbonate (ACC) during each premolt in a pair of gastroliths synthesized in the stomach wall. How calcium carbonate is stabilized in the amorphous state in such a biocomposite remains speculative. The knowledge of the microstructure at the nanometer level obtained by field emission scanning electron microscopy and atomic force microscopy combined with scanning electron microscopy energy-dispersive X-ray spectroscopy, micro-Raman and X-ray absorption near edge structure spectroscopy gave relevant information on the elaboration of such an ACC-stabilized biomineral. We observed nanogranules distributed along chitin-protein fibers and the aggregation of granules in thin layers. AFM confirmed the nanolevel structure, showing granules probably surrounded by an organic layer and also revealing a second level of aggregation as described for other crystalline biominerals. Raman analyses showed the presence of ACC, amorphous calcium phosphate, and calcite. Elemental analyses confirmed the presence of elements like Fe, Na, Mg, P, and S. P and S are heterogeneously distributed. P is present in both the mineral and organic phases of gastroliths. S seems present as sulfate (probably as sulfated sugars), sulfonate, sulfite, and sulfoxide groups and, in a lesser extent, as sulfur-containing amino acids.

  11. Modeling Strain Rate Effect for Heterogeneous Brittle Materials

    Institute of Scientific and Technical Information of China (English)

    MA Guowei; DONG Aiai; LI Jianchun

    2006-01-01

    Rocks are heterogeneous from the point of microstructure which is of significance to their dynamic failure behavior.Both the compressive and tensile strength of rock-like materials is regarded different from the static strength.The present study adopts smoothed particle hydrodynamics (SPH) which is a virtual particle based meshfree method to investigate strain rate effect for heterogeneous brittle materials.The SPH method is capable of simulating rock fracture,free of the mesh constraint of the traditional FEM and FDM models.A pressure dependent J-H constitutive model involving heterogeneity is employed in the numerical modeling.The results show the compressive strength increases with the increase of strain rate as well as the tensile strength,which is important to the engineering design.

  12. EBSD Analysis of Deformed and Partially Recrystallized Microstructures in ECAE-Processed Copper

    DEFF Research Database (Denmark)

    Mishin, Oleg; Bowen, Jacob R.; Godfrey, A.

    2012-01-01

    -uniform distribution of strain imposed by processing. The through-thickness heterogeneity of the deformed microstructure resulted in a different extent of recrystallization in different layers during annealing. Recrystallized grains were also observed in samples that were not annealed, but stored at room temperature...

  13. Heterogeneity in breast cancer.

    Science.gov (United States)

    Polyak, Kornelia

    2011-10-01

    Breast cancer is a heterogeneous disease. There is a high degree of diversity between and within tumors as well as among cancer-bearing individuals, and all of these factors together determine the risk of disease progression and therapeutic resistance. Advances in technologies such as whole-genome sequencing and functional viability screens now allow us to analyze tumors at unprecedented depths. However, translating this increasing knowledge into clinical practice remains a challenge in part due to tumor evolution driven by the diversity of cancer cell populations and their microenvironment. The articles in this Review series discuss recent advances in our understanding of breast tumor heterogeneity, therapies tailored based on this knowledge, and future ways of assessing and treating heterogeneous tumors.

  14. Green heterogeneous wireless networks

    CERN Document Server

    Ismail, Muhammad; Nee, Hans-Peter; Qaraqe, Khalid A; Serpedin, Erchin

    2016-01-01

    This book focuses on the emerging research topic "green (energy efficient) wireless networks" which has drawn huge attention recently from both academia and industry. This topic is highly motivated due to important environmental, financial, and quality-of-experience (QoE) considerations. Specifically, the high energy consumption of the wireless networks manifests in approximately 2% of all CO2 emissions worldwide. This book presents the authors’ visions and solutions for deployment of energy efficient (green) heterogeneous wireless communication networks. The book consists of three major parts. The first part provides an introduction to the "green networks" concept, the second part targets the green multi-homing resource allocation problem, and the third chapter presents a novel deployment of device-to-device (D2D) communications and its successful integration in Heterogeneous Networks (HetNets). The book is novel in that it specifically targets green networking in a heterogeneous wireless medium, which re...

  15. Heterogeneous self-assembled media for biopolymerization

    DEFF Research Database (Denmark)

    Monnard, Pierre-Alain

    2011-01-01

    compartments and lipid-bilayer lattices. Another kind of media is represented by self-assembled phases in the reaction medium, e.g., in water-ice matrices that are formed by two co-existing aqueous phases (a solid phase and a concentrated liquid phase) when an aqueous solution is cooled below its freezing......Heterogeneous media, such as micro-structured aqueous environments, could offer an alternative approach to the synthesis of biopolymers with novel functions. Structured media are here defined as specialized, self-assembled structures that are formed, e.g, by amphiphiles, such as liposomes, emulsion...... point, but above the eutectic point. These media have the capacity to assemble chemical molecules or complex catalytic assemblies into unique configurations that are unstable or unavailable in bulk aqueous phases. Reactions can then proceed which do not readily occur in homogeneous solutions. To gauge...

  16. Microstructure Development during Roughing and Intermediate Cooling of Thick HTP Linepipe Steels

    Science.gov (United States)

    Banks, Kevin; Maubane, Rorisang

    The microstructural development during roughing and early finishing of thick, high Nb-Ti steels containing high and low Mn contents has been investigated for conventional cold charging (CCR) and quasi compact strip production (CSP) conditions. Multi-pass rolling simulations were performed, followed by interrupted accelerated cooling, to study the "as-coiled" ferrite/pearlite microstructure. Local heterogeneous regions, LHR, were often found after CSP simulations, but not after CCR where the microstructure was generally uniform. Coarse, local heterogeneous regions can be prevented in HTP steels though complete recrystallization of the as-cast austenite during and after roughing by i) applying sufficient strain at roughing temperatures above the TiNb(C,N) precipitation region, ii) slow intermediate cooling and iii) using high Mn contents to suppress precipitation. For thick HTP skelp, the initiation of dynamic recrystallization is of little use in avoiding LHR due to limited strain available for completing the necklacing process.

  17. Topological dependence of mechanical responses of solidification microstructures in aluminum brazed joints

    Institute of Scientific and Technical Information of China (English)

    GAO Feng(高峰); QIAN Yi-yu(钱乙余); D.P.Sekulic; MA Xin(马鑫); F.Yoshida

    2003-01-01

    The main objective is to provide an evidence of spatial dependence of mechanical responses of a heterogeneous aluminum brazed joint re-solidified clad,and to confirm a sufficient sensitivity of a nano-indentation--load curve method for identifying the dependence.Topological features of a network of solidification microstructures(αphase and eutectic),formed during quench in a brazing process of aluminum alloy,influence significantly dynamic mechanical responses of resulting heterogeneous material.Nano/micro indentation depth vs load characteristics of differing phases suggest a spatially sensitive mechanical response of a re-solidified fillet in the joint zone.Hence,a spatial distribution,pattern formations and other morphological characteristics of microstructures have a direct impact on an ultimate joint integrity.Topology-induced variations of indentation-load curves was presented.A hypothesis involving microstructures'spatial distribution vs mechanical response was formulated.

  18. Isotopes in heterogeneous catalysis

    CERN Document Server

    Hargreaves, Justin SJ

    2006-01-01

    The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

  19. Effect of microstructure on the fracture response of advanced high strength steels

    Science.gov (United States)

    Taylor, Mark David

    The effect of constituent hardness on formability performance for higher-strength dual phase (DP) steels was evaluated. A commercially-produced DP steel with 1080 MPa ultimate tensile strength (UTS) was processed to create eight additional constituent hardness conditions by tempering and cold-rolling, processes that primarily affected constituent hardness properties. Using nanoindentation, ferrite and martensite hardness values for the nine conditions of the DP steel (as-received, four as-tempered, four temper cold-rolled) provided a range of hardness values to evaluate formability performance. Formability performance for the nine steel conditions was evaluated using tensile and hole expansion testing. A decrease in martensite/ferrite hardness ratio corresponded to an increase in hole expansion ratio (HER), and an increase in yield strength (YS). A lower hardness ratio (increased similarity of ferrite and martensite hardness) was interpreted to increase strain-sharing between ferrite and martensite, which suppressed plastic strain localization to higher stresses for the case of YS, and to higher formability limits for the case of HER. A lower hardness ratio corresponded to a decrease in work-hardening, and was interpreted to be caused by the suppression of strain localization in ferrite. Multiple studies from literature correlated HER to tensile properties, and the nine steel conditions produced consistent trends with the data reported in each study, confirming the experimental HER and tensile properties obtained in the current study are consistent with literature. The microstructural response to plastic deformation was evaluated using two DP steels with equivalent UTS and different hardness ratios. Nanoindentation analyses on tensile specimens deformed to the UTS revealed a greater increase in ferrite hardness for the higher hardness ratio steel, interpreted to be caused by the greater amount of work hardening. EBSD crystallographic orientation maps for the two DP

  20. An estimating function approach to linkage heterogeneity

    Indian Academy of Sciences (India)

    He Gao; Ying Zhou; Weijun Ma; Haidong Liu; Linan Zhao

    2013-12-01

    Testing linkage heterogeneity between two loci is an important issue in genetics. Currently, there are four methods (K-test, A-test, B-test and D-test) for testing linkage heterogeneity in linkage analysis, which are based on the likelihood-ratio test. Among them, the commonly used methods are the K-test and A-test. In this paper, we present a novel test method which is different from the above four tests, called G-test. The new test statistic is based on estimating function, possessing a theoretic asymptotic distribution, and therefore demonstrates its own advantages. The proposed test is applied to analyse a real pedigree dataset. Our simulation results also indicate that the G-test performs well in terms of power of testing linkage heterogeneity and outperforms the current methods to some degree.

  1. Heterogeneity in Preferences and Productivity

    DEFF Research Database (Denmark)

    Gørtz, Mette

    versus housework, 2) preferences for leisure compared to consumption, and 3) marginal utility of wealth, is correlated with the retirement decision. Based on US consumption and time use data for 2001 and 2003 from the Consumptions and Activities Mail Survey (CAMS), we study the patterns of individual...... choices of expenditure, household production and leisure for people in and around retirement. The unobserved individual heterogeneity factor is isolated by comparing cross-sectional evidence and panel data estimates of the effects of retirement on consumption and time allocation. Based on cross......-section data, we can identify a difference in consumption due to retirement status, but when the panel nature of the data is exploited, the effect of retirement on consumption is small and insignificant. Moreover, the analyses point at a large positive effect of retirement on household production. Our results...

  2. A novel three-phase model of brain tissue microstructure.

    Science.gov (United States)

    Gevertz, Jana L; Torquato, Salvatore

    2008-08-15

    We propose a novel biologically constrained three-phase model of the brain microstructure. Designing a realistic model is tantamount to a packing problem, and for this reason, a number of techniques from the theory of random heterogeneous materials can be brought to bear on this problem. Our analysis strongly suggests that previously developed two-phase models in which cells are packed in the extracellular space are insufficient representations of the brain microstructure. These models either do not preserve realistic geometric and topological features of brain tissue or preserve these properties while overestimating the brain's effective diffusivity, an average measure of the underlying microstructure. In light of the highly connected nature of three-dimensional space, which limits the minimum diffusivity of biologically constrained two-phase models, we explore the previously proposed hypothesis that the extracellular matrix is an important factor that contributes to the diffusivity of brain tissue. Using accurate first-passage-time techniques, we support this hypothesis by showing that the incorporation of the extracellular matrix as the third phase of a biologically constrained model gives the reduction in the diffusion coefficient necessary for the three-phase model to be a valid representation of the brain microstructure.

  3. A novel three-phase model of brain tissue microstructure.

    Directory of Open Access Journals (Sweden)

    Jana L Gevertz

    Full Text Available We propose a novel biologically constrained three-phase model of the brain microstructure. Designing a realistic model is tantamount to a packing problem, and for this reason, a number of techniques from the theory of random heterogeneous materials can be brought to bear on this problem. Our analysis strongly suggests that previously developed two-phase models in which cells are packed in the extracellular space are insufficient representations of the brain microstructure. These models either do not preserve realistic geometric and topological features of brain tissue or preserve these properties while overestimating the brain's effective diffusivity, an average measure of the underlying microstructure. In light of the highly connected nature of three-dimensional space, which limits the minimum diffusivity of biologically constrained two-phase models, we explore the previously proposed hypothesis that the extracellular matrix is an important factor that contributes to the diffusivity of brain tissue. Using accurate first-passage-time techniques, we support this hypothesis by showing that the incorporation of the extracellular matrix as the third phase of a biologically constrained model gives the reduction in the diffusion coefficient necessary for the three-phase model to be a valid representation of the brain microstructure.

  4. Heterogeneous Uncertainty Management

    Science.gov (United States)

    2008-03-08

    probabilistic ( HTP ) agents, the concept of probabilistic version of XML and RDF, and probabilistic methods to reason about collections of moving objects. S...heterogeneous temporal probabilistic ( HTP ) agents, the concept of probabilistic version of XML and RDF, and probabilistic methods to reason about...temporal probabilistic ( HTP ) agent. HTP agents can build temporal probabilistic reasoning capabilities on top of multiple databases and software

  5. Heterogeneous Computing in Economics

    DEFF Research Database (Denmark)

    Dziubinski, M.P.; Grassi, S.

    2014-01-01

    This paper shows the potential of heterogeneous computing in solving dynamic equilibrium models in economics. We illustrate the power and simplicity of C++ Accelerated Massive Parallelism (C++ AMP) recently introduced by Microsoft. Starting from the same exercise as Aldrich et al. (J Econ Dyn...

  6. Heterogeneity of Intellectual Assets

    DEFF Research Database (Denmark)

    Dahlgren, Johan Henrich; Lund Jensen, Rasmus; Valentin, Finn

    2004-01-01

    This paper deals with methodological issues of assessing the composition and level ofheterogeneity of firms' intellectual assets. It develops an original metric - referred to asthe H-index - for measuring heterogeneity using data extracted from patent documents.The main purpose is to improve...

  7. Heterogeneous chromium catalysts

    NARCIS (Netherlands)

    2005-01-01

    The present invention relates to a heterogeneous chromium catalyst system for the polymerisation of ethylene and/or alpha olefins prepared by the steps of: (a) providing a silica-containing support, (b) treating the silica-containing support with a chromium compound to form a chromium-based silica-c

  8. Information and Heterogeneous Beliefs

    DEFF Research Database (Denmark)

    Christensen, Peter Ove; Qin, Zhenjiang

    2014-01-01

    In an incomplete market with heterogeneous prior beliefs, we show public information can have a substantial impact on the ex ante cost of capital, trading volume, and investor welfare. The Pareto effcient public information system is the system enjoying the maximum ex ante cost of capital and the...

  9. Heterogeneity of Dutch rainfall

    NARCIS (Netherlands)

    Witter, J.V.

    1984-01-01

    Rainfall data for the Netherlands have been used in this study to investigate aspects of heterogeneity of rainfall, in particular local differences in rainfall levels, time trends in rainfall, and local differences in rainfall trend. The possible effect of urbanization and industrialization on the

  10. Receiver Heterogeneity Helps

    DEFF Research Database (Denmark)

    Kovács, Erika R.; Pedersen, Morten Videbæk; Roetter, Daniel Enrique Lucani;

    2014-01-01

    Heterogeneity amongst devices and desired service are commonly seen as a source of additional challenges for setting up an efficient multi-layer multicast service. In particular, devices requiring only the base layer can become a key bottleneck to the performance for other devices. This paper...

  11. Thermal microstructure measurement system

    Science.gov (United States)

    Carver, Michael J. (Inventor)

    1985-01-01

    A thermal microstructure measurement system (TMMS) operates autonomously h its own internal power supply and telemeters data to a platform. A thermal array is mounted on a cross-braced frame designed to orient itself normal to existing currents with fixed sensor positioning bars protruding from the cross bars. A plurality of matched thermistors, conductivity probes and inclinometers are mounted on the frame. A compass and pressure transducer are contained in an electronics package suspended below the array. The array is deployed on a taut mooring below a subsurface float. Data are digitized, transmitted via cable to a surface buoy and then telemetered to the platform where the data is processed via a computer, recorded and/or displayed. The platform computer also sends commands to the array via telemetry.

  12. Modeling the Permittivity of Two-Phase Media Containing Monodisperse Spheres: Effects of Microstructure and Multiple Scattering

    OpenAIRE

    Doyle, Timothy E; Robinson, David A.; Scott B. Jones; Warnick, Keith H.; Carruth, Brent L.

    2007-01-01

    A numerical modeling approach was developed to predict the dielectric properties of heterogeneous particulate materials with arbitrary microstructures. To test the method, simulation and experimental data were acquired for the effective permittivities of various glass sphere suspensions. Both ordered lattices and random microstructures of up to 3600 spheres were modeled for volume fractions of 0.025–0.60. The electric fields in the suspensions were computed using an iterative multipole method...

  13. Microstructure informed tractography: pitfalls and open challenges

    Directory of Open Access Journals (Sweden)

    Alessandro eDaducci

    2016-06-01

    Full Text Available One of the major limitations of diffusion MRI tractography is that the fiber tracts recovered by existing algorithms are not truly quantitative. Local techniques for estimating more quantitative features of the tissue microstructure exist, but their combination with tractography has always been considered intractable. Recent advances in local and global modeling made it possible to fill this gap and a number of promising techniques for microstructure informed tractography have been suggested, opening new and exciting perspectives for the quantification of brain connectivity. The ease-of-use of the proposed solutions made it very attractive for researchers to include such advanced methods in their analyses; however, this apparent simplicity should not hide some critical open questions raised by the complexity of these very high-dimensional problems, otherwise some fundamental issues may be pushed into the background. The aim of this article is to raise awareness in the diffusion MRI community, notably researchers working on brain connectivity, about some potential pitfalls and modeling choices that make the interpretation of the outcomes from these novel techniques rather cumbersome. Through a series of experiments on synthetic and real data, we illustrate practical situations where erroneous and severely biased conclusions may be drawn about the connectivity if these pitfalls are overlooked, like the presence of partial/missing/duplicate fibers or the critical importance of the diffusion model adopted. Microstructure informed tractography is a young but very promising technology, and by acknowledging its current limitations as done in this paper, we hope our observations will trigger further research in this direction and new ideas for truly quantitative and biologically-meaningful analyses of the connectivity.

  14. Microstructure and Properties of High-Temperature Superconductors

    CERN Document Server

    Parinov, Ivan A

    2007-01-01

    The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

  15. Microstructure and Properties of High-Temperature Superconductors

    CERN Document Server

    Parinov, I A

    2012-01-01

    The main features of high-temperature superconductors (HTSC) that define their properties are intrinsic brittleness of oxide cuprates, the layered anisotropic structure and the supershort coherence length. Taking into account these features, this treatise presents research into HTSC microstructure and properties, and also explores the possibilities of optimization of the preparation techniques and superconducting compositions. The "composition-technique-experiment-theory-model," employed here, assumes considerable HTSC defectiveness and structure heterogeneity and helps to draw a comprehensive picture of modern representations of the microstructure, strength and the related structure-sensitive properties of the materials considered. Special attention is devoted to the Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O families, which currently offer the most promising applications. Including a great number of illustrations and references, this monograph addresses students, post-graduate students and specialists, taking part in the ...

  16. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  17. Topological Optimization of Artificial Microstructure Strategies

    Science.gov (United States)

    2015-04-02

    Topographic Optimization Through Artificial Microstructure Strategies During this project as part of DARPA MCMA we aimed to develop and demonstrate...Topographic Optimization Through Artificial Microstructure Strategies Report Title During this project as part of DARPA MCMA we aimed to develop and...Artificial Microstructure Strategies (Yale and Johns Hopkins) During DARPA MCMA we aimed to develop and demonstrate a 3D microstructural

  18. Effects of heterogeneity on recrystallization kinetics of nanocrystalline copper prepared by dynamic plastic deformation

    DEFF Research Database (Denmark)

    Lin, Fengxiang; Zhang, Yubin; Tao, Nairong;

    2014-01-01

    Recrystallization and mechanical behavior of nanocrystalline copper prepared by dynamic plastic deformation (DPD) and DPD with additional cold-rolling (DPD+CR) were investigated, with an emphasis on the effects of heterogeneity within the deformation microstructure. The DPD sample was found...... than 1, which is explained using a two-stage kinetics model incorporating the heterogeneity. The heterogeneity of the DPD sample is largely reduced by applying additional rolling. This change in deformation path leads to a more random distribution of the recrystallized grains and more conventional...

  19. PDF-based heterogeneous multiscale filtration model.

    Science.gov (United States)

    Gong, Jian; Rutland, Christopher J

    2015-04-21

    Motivated by modeling of gasoline particulate filters (GPFs), a probability density function (PDF) based heterogeneous multiscale filtration (HMF) model is developed to calculate filtration efficiency of clean particulate filters. A new methodology based on statistical theory and classic filtration theory is developed in the HMF model. Based on the analysis of experimental porosimetry data, a pore size probability density function is introduced to represent heterogeneity and multiscale characteristics of the porous wall. The filtration efficiency of a filter can be calculated as the sum of the contributions of individual collectors. The resulting HMF model overcomes the limitations of classic mean filtration models which rely on tuning of the mean collector size. Sensitivity analysis shows that the HMF model recovers the classical mean model when the pore size variance is very small. The HMF model is validated by fundamental filtration experimental data from different scales of filter samples. The model shows a good agreement with experimental data at various operating conditions. The effects of the microstructure of filters on filtration efficiency as well as the most penetrating particle size are correctly predicted by the model.

  20. Experimental analysis on the coupled effect between thermo-optical properties and microstructure of semi-crystalline thermoplastics

    Science.gov (United States)

    Boztepe, Sinan; Thiam, Abdoulahad; de Almeida, Olivier; Le Maoult, Yannick; Schmidt, Fabrice

    2016-10-01

    Radiation heat transfer is the most common method used in thermoforming processes of thermoplastic polymers due to their poor thermal conductivity. Considering the fact that the thermo-optical characteristics of polymers play a major role in the efficiency of radiative heat transfer in bulk polymers, microstructure of semi-crystalline thermoplastics is one of the key factors to understand this heat transfer phenomenon in depth. In this study, a relation between the microcrystalline structure of polyolefin (PO) and its effect on the thermo-optical properties was experimentally analyzed. Information on the microcrystalline structure of the samples was obtained by determining the degree of crystallinity (Xc) thanks to Differential Scanning Calorimetry (DSC). Using Fourier Transform Infrared (FT-IR) spectroscopy and integrating sphere, optical characteristics of the PO samples were analyzed considering two spectrums that are in near-infrared (NIR) and middle-infrared (MIR) spectral regions respectively. The analyses showed that the degree of crystallinity has a great effect on the thermo-optical characteristics of the PO - particularly considering transmission - in NIR range. Such a coupled effect can be functionalized and adopted to develop an advanced radiative heat transfer model that may be used for addressing various problems on infrared (IR) heating of heterogeneous materials, particularly semi-crystalline thermoplastics. In the last part of the paper, a theoretical approach for consideration of the heterogeneity of semi-crystalline thermoplastics in a radiative heat transfer model was highlighted.

  1. Solidification and microstructural aspects of laser-deposited Ni–Mo–Cr–Si alloy on stainless steel

    Indian Academy of Sciences (India)

    Reena Awasthi; Santosh Kumar; D Srivastava; G K Dey

    2010-12-01

    Laser cladding of stainless steel substrate was carried out using Ni–32Mo–15Cr–3Si (wt%) alloy powder. Laser cladding parameters were optimized to obtain defect-free and metallurgically bonded clad. Variation in solidification rate, cooling rate and compositional variation resulted in heterogeneous microstructure. Microstructure was found to be distinctly different in regions of clad cross-section. Majority of the region was found to consist of eutectic of Mo-rich hcp intermetallic Laves phase and NiFe fcc gamma solid solution phases. Extensive microstructural examinations of different clad regions have been carried out using microscopy and microanalysis techniques.

  2. Three-dimensional Reconstruction and Homogenization of Heterogeneous Materials Using Statistical Correlation Functions and FEM

    Energy Technology Data Exchange (ETDEWEB)

    Baniassadi, Majid; Mortazavi, Behzad; Hamedani, Amani; Garmestani, Hamid; Ahzi, Said; Fathi-Torbaghan, Madjid; Ruch, David; Khaleel, Mohammad A.

    2012-01-31

    In this study, a previously developed reconstruction methodology is extended to three-dimensional reconstruction of a three-phase microstructure, based on two-point correlation functions and two-point cluster functions. The reconstruction process has been implemented based on hybrid stochastic methodology for simulating the virtual microstructure. While different phases of the heterogeneous medium are represented by different cells, growth of these cells is controlled by optimizing parameters such as rotation, shrinkage, translation, distribution and growth rates of the cells. Based on the reconstructed microstructure, finite element method (FEM) was used to compute the effective elastic modulus and effective thermal conductivity. A statistical approach, based on two-point correlation functions, was also used to directly estimate the effective properties of the developed microstructures. Good agreement between the predicted results from FEM analysis and statistical methods was found confirming the efficiency of the statistical methods for prediction of thermo-mechanical properties of three-phase composites.

  3. 基于微结构光纤的新型功能器件、异质兼容结构与光电子集成2013年度进展报告%Functional Devices, Heterogeneous Compatible Structure and Optoelectronic Integration Based on Microstructural Optical Fiber/2013 Annual Report

    Institute of Scientific and Technical Information of China (English)

    刘艳格; 张霞; 王志; 张昊; 周文远

    2016-01-01

    According to the main research topics and expectations of the mission statement for this year, we carried out a lot of theoretical and experimental studies, the main findings of the report include the following:(1)The conduction mechanism and mode characteristics of a simplified hollow-core microstructure optical fiber have been investigated and revealed. A high efficiency fluorescence measurement technology based on the simplified hollow-core microstructure optical fiber and lateral side detection approach has been demonstrated. A highlighted sensitivity with dye concentrations down to 1 pM is achieved, which is the best value in the reported to our best knowledge.(2)The mode coupling and modal birefringence characteristics of various types of the high-index-filled MOFs with different selective filling configurations and different materials have been theoretically investigated. Sensors with ultrahigh sensitivity based on the Sagnac interferometer using this type of birefringence fiber has been proposed and demonstrated.(3)A twin-resonance-coupling phenomenon in a selectively single-hole fluid-filled microstructure optical fiber have been proposed, demonstrated and investigated. Sensitivities of 290 nm/°C (739,796 nm/RIU) and 591.84 nm/N (701.2 pm/με) are achieved, which are the highest for a fiber-based device to date to our best knowledge.(4)A fluid-filled two-mode photonic crystal fiber (PCF)-based intermodal interferometer have been demonstrated and investigated.(5)We have reported on the fabrication and resonance mechanism of a fiber Bragg grating (FBG) with multiple resonances in a two-dimensional waveguide array microstructured optical fiber. Simultaneous measurement results of curvature and axial strain have also demonstrated.(6)The acousto-optic mode coupling in grapefruit microstructured optical fibers (GMOFs) has been investigated and unequal acoustic modulation is generated, and orthogonal acoustic gratings come into being in the GMOF.(7)We have

  4. Computer vision in microstructural analysis

    Science.gov (United States)

    Srinivasan, Malur N.; Massarweh, W.; Hough, C. L.

    1992-01-01

    The following is a laboratory experiment designed to be performed by advanced-high school and beginning-college students. It is hoped that this experiment will create an interest in and further understanding of materials science. The objective of this experiment is to demonstrate that the microstructure of engineered materials is affected by the processing conditions in manufacture, and that it is possible to characterize the microstructure using image analysis with a computer. The principle of computer vision will first be introduced followed by the description of the system developed at Texas A&M University. This in turn will be followed by the description of the experiment to obtain differences in microstructure and the characterization of the microstructure using computer vision.

  5. Heterogeneous Voter Models

    CERN Document Server

    Masuda, Naoki; Redner, S

    2010-01-01

    We introduce the heterogeneous voter model (HVM), in which each agent has its own intrinsic rate to change state, reflective of the heterogeneity of real people, and the partisan voter model (PVM), in which each agent has an innate and fixed preference for one of two possible opinion states. For the HVM, the time until consensus is reached is much longer than in the classic voter model. For the PVM in the mean-field limit, a population evolves to a "selfish" state, where each agent tends to be aligned with its internal preference. For finite populations, discrete fluctuations ultimately lead to consensus being reached in a time that scales exponentially with population size.

  6. Information and Heterogeneous Beliefs

    DEFF Research Database (Denmark)

    Christensen, Peter Ove; Qin, Zhenjiang

    2014-01-01

    In an incomplete market with heterogeneous prior beliefs, we show public information can have a substantial impact on the ex ante cost of capital, trading volume, and investor welfare. The Pareto effcient public information system is the system enjoying the maximum ex ante cost of capital...... ante risk premium is unaffected by the informativeness of the public information system. Similar results are obtained in a production economy, but the impact on the ex ante cost of capital is dampened compared to the exchange economy due to welfare improving reductions in real investments to smooth...... and the maximum expected abnormal trading volume. Imperfect public information increases the gains-to-trade based on heterogeneously updated posterior beliefs. In an exchange economy, this leads to higher growth in the investors' certainty equivalents and, thus, a higher equilibrium interest rate, whereas the ex...

  7. Heterogeneity of monoclonal antibodies.

    Science.gov (United States)

    Liu, Hongcheng; Gaza-Bulseco, Georgeen; Faldu, Dinesh; Chumsae, Chris; Sun, Joanne

    2008-07-01

    Heterogeneity of monoclonal antibodies is common due to the various modifications introduced over the lifespan of the molecules from the point of synthesis to the point of complete clearance from the subjects. The vast number of modifications presents great challenge to the thorough characterization of the molecules. This article reviews the current knowledge of enzymatic and nonenzymatic modifications of monoclonal antibodies including the common ones such as incomplete disulfide bond formation, glycosylation, N-terminal pyroglutamine cyclization, C-terminal lysine processing, deamidation, isomerization, and oxidation, and less common ones such as modification of the N-terminal amino acids by maleuric acid and amidation of the C-terminal amino acid. In addition, noncovalent associations with other molecules, conformational diversity and aggregation of monoclonal antibodies are also discussed. Through a complete understanding of the heterogeneity of monoclonal antibodies, strategies can be employed to better identify the potential modifications and thoroughly characterize the molecules.

  8. Microstructural Evaluation and Thermal Creep Behavior of Zr-Excel

    Science.gov (United States)

    Ahmmed, Kazi Foyez

    Dual phase (alpha-beta) Zr-Excel Pressure Tube (PT) material has been heat treated in the (alpha+beta) or beta-phase regime to generate variable microstructures. These heat-treated microstructures revealed significant modification in the inital microstructure. The microstructural changes by heat-treatment will have a profound influence on their deformation behavior; characterizing those properties is the main goal of this study. In this dissertation, the experimental results are presented in a manuscript format, which is divided in three technical chapters. Chapter 3 discusses the effect of heat treatment on texture modification; where, as received (ASR) PT materials were heated to a range of temperatures and cooled either in water or in air. It has been observed that due to the orientation relationship between alpha and beta-phase, the ASR microstructure has been significantly altered during heating and cooling. The extent of this alteration strongly depends on the solution temperature and cooling rate. Although, variant selection is observed during texture modification, significant randomization is noticed in the room temperature texture. In Chapter 4, line profile analysis technique has been used to quantitatively analyze the microstructural details of the heat-treated materials. Diffraction pattern analyses demonstrated significant peak broadening in the heat-treated material; which is attributed due to the increase of volume fraction of martensitic alpha and alteration in the dislocation structures. Line profile analyses also revealed that primary alpha consists with large sub-grains and correlated dislocations but the martensitic alpha are highly dislocated. Finally in Chapter 5, thermal creep behavior of the heat treated materials has been studied. Microstructural analyses were also conducted in the pre- and post-creep materials to understand the creep mechanism. Creep anisotropy of the heat treated materials has been investigated by correlating the

  9. Electrokinetics of heterogeneous interfaces.

    Science.gov (United States)

    Zembala, Maria

    2004-12-31

    The influence of surface heterogeneity of various types on electrokinetic parameters is reviewed. The scope of the paper covers classical electrokinetic phenomena characterized by linear dependence of electrokinetic parameters vs. related driving forces. Neither non-linear effects nor the effects of non-equilibrium electric double layer are considered. A historical description of hydrodynamic aspect of electrokinetic phenomena exploiting the slip plane idea is briefly outlined. Attempts to estimate the slip plane location by comparing the diffuse layer and zeta potential values for some model systems are presented. The surface heterogeneity was divided into three categories. Heterogeneity of the first type was related to geometrical morphology of an interfacial region characterized by a considerable surface development producing a three-dimensional interfacial region. The effects of solid roughness, hairy surface, dense polymer layers and gel-like layers are discussed here. The very high surface conductivity detected for such interfaces seems to be a good indicator of the presence of structured layers of this type. Heterogeneous interfaces of the second class cover systems exhibiting non-uniform distribution of surface charge. The non-uniform surface charge distribution can be either of a molecular (discrete charges) or of a microscale (two-dimensional micropatches or three-dimensional structures formed by polyelectrolyte multilayers). The last class of systems examined includes interfaces composed of charged substrate covered by charged bulky objects (particles). In comparison to the homogeneous surfaces, adsorbed charged particles modify both hydrodynamic flow and the electrostatic field significantly altering the electrokinetic parameters. The new description of electrokinetics of composed interfaces presented here takes into account both hydrodynamic and electric field modification and is free of the previously assumed slip plane shift caused by adsorbed

  10. Zirconia implant abutments: microstructural analysis.

    Science.gov (United States)

    Vaquero-Aguilar, Cristina; Jiménez-Melendo, Manuel; Torres-Lagares, Daniel; Llena-Blasco, Oriol; Bruguera, August; Llena-Blasco, Jaime; García-Calderón, Manuel; Velázquez-Cayón, Rocío; Gutiérrez-Pérez, José-Luis

    2012-01-01

    Yttria-stabilized zirconia (ZrO₂-Y₂O₃) ceramics have received increasing attention in recent years because of their stress-induced tetragonal-to-monoclinic (martensitic) transformation. This unique process acts as a toughening mechanism, imparting strength and toughness to the ceramic alloy. This property, along with well-documented biocompatibility, is now being exploited in an increasing number of medical applications, including implant dentistry. To prevent clinical problems and predict their behavior and physical limitations, a characterization of the ceramic elements used in dental restorations is essential. The aim of the present study is to characterize the crystal structure, elemental composition, and micr ostructure of asreceived ZiReal Post (Biomet 3i) zirconium oxide abutments, as well as specimens coated with a first layer of a low-fusing fluoroapatite ceramic. Zirconium oxide abutments, both as-received and porcelain-coated, were studied using the following techniques: x-ray diffraction, x-ray fluorescence, energy dispersive x-ray spectroscopy, optical microscopy, and scanning and transmission electron microscopy. X-ray analyses detected only the presence of Zr, O, Y, and hafnium (Hf), in an amount of 3% to 4% molecular weight Y₂O₃-ZrO₂. X-ray diffraction measurements showed that the ceramic abutment crystallizes mainly in the tetragonal phase, with some residual monoclinic phase. The microstructure is characterized by a rather homogenous grain distribution, formed by equiaxed and fine grains with a mean size of 0.30 Μm. Compositional and diffraction results are consistent with polycrystalline yttria-stabilized tetragonal zirconia. The material is susceptible to undergoing the stress-induced transformation toughening mechanism because of the very fine grain size. Except for machining ring marks, the surfaces exhibit an excellent finishing quality. No structural modifications were observed in the fluoroapatite ceramic-coated abutments

  11. Microstructural analysis of bile: relevance to cholesterol gallstone pathogenesis.

    Science.gov (United States)

    Rubin, M; Pakula, R; Konikoff, F M

    2000-07-01

    The study of physical-chemical factors and pathways leading to cholesterol crystallization in bile has important clinical relevance. The major processes in cholesterol gallstone formation can be subdivided into nucleation, formation and precipitation of solid crystals (crystallization), crystal growth, crystal agglomeration and stone growth. A clear understanding of the microstructural events occurring during the earliest stages of these processes in bile is crucial for the identification of factors possibly delaying or preventing precipitation of cholesterol crystals and, therefore, gallstone formation in bile. Detection and characterization of microstructures in native and model biles can be achieved by both direct and indirect techniques. Direct imaging techniques provide more readily interpretable information, but sample preparation problems, particularly for electron microscopy, are a source of artifacts. Moreover, microscopic techniques provide only qualitative data without the possibility to quantitate or to analyse the composition of microstructures. Several indirect techniques have been used to obtain additional microstructural information about nucleating bile. These techniques have the disadvantage of often being model dependent in addition to constraints specific for each method. The systematic, judicious use of a combination of complementary direct and indirect techniques have led to a comprehensive understanding of the various microstructural processes and interactions occurring during bile secretion, flow in the biliary tract and storage in the gallbladder. This forms the basis for our current understanding of cholesterol nucleation, crystallization and gallstone formation.

  12. Two-Dimensional Nonlinear Finite Element Analysis of CMC Microstructures

    Science.gov (United States)

    Mital, Subodh K.; Goldberg, Robert K.; Bonacuse, Peter J.

    2012-01-01

    A research program has been developed to quantify the effects of the microstructure of a woven ceramic matrix composite and its variability on the effective properties and response of the material. In order to characterize and quantify the variations in the microstructure of a five harness satin weave, chemical vapor infiltrated (CVI) SiC/SiC composite material, specimens were serially sectioned and polished to capture images that detailed the fiber tows, matrix, and porosity. Open source quantitative image analysis tools were then used to isolate the constituents, from which two dimensional finite element models were generated which approximated the actual specimen section geometry. A simplified elastic-plastic model, wherein all stress above yield is redistributed to lower stress regions, is used to approximate the progressive damage behavior for each of the composite constituents. Finite element analyses under in-plane tensile loading were performed to examine how the variability in the local microstructure affected the macroscopic stress-strain response of the material as well as the local initiation and progression of damage. The macroscopic stress-strain response appeared to be minimally affected by the variation in local microstructure, but the locations where damage initiated and propagated appeared to be linked to specific aspects of the local microstructure.

  13. Short range ordering and microstructure property relationship in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shariq, A.

    2006-07-01

    A novel algorithm, ''Next Neighbourhood Evaluation (NNE)'', is enunciated during the course of this work, to elucidate the next neighbourhood atomic vicinity from the data, analysed using tomographic atom probe (TAP) that allows specifying atom positions and chemical identities of the next neighbouring atoms for multicomponent amorphous materials in real space. The NNE of the Pd{sub 55}Cu{sub 23}P{sub 22} bulk amorphous alloy reveals that the Pd atoms have the highest probability to be the next neighbours to each other. Moreover, P-P correlation corroborates earlier investigations with scattering techniques that P is not a direct next neighbour to another P atom. Analogous investigations on the Fe{sub 40}Ni{sub 40}B{sub 20} metallic glass ribbons, in the as quenched state and for a state heat treated at 350 C for 1 hour insinuate a pronounced elemental inhomogeneity for the annealed state, though, it also depicts glimpse of a slight inhomogeneity for B distribution even for the as quenched sample. Moreover, a comprehensive microstructural investigation has been carried out on the Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy system. TEM and TAP investigations evince that the as cast bulk samples constitutes a composite structure of an amorphous phase and crystalline phase(s). The crystallization is essentially triggered at the mould walls due to heterogeneous nucleation. The three dimensional atomic reconstruction maps of the volume analysed by TAP reveal a complex stereological interconnected network of two phases. The phase that is rich in Zr and Al concentration is depleted in Co concentration while the phase that is rich in Co concentration is depleted both in Zr and Al. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy splat samples exhibit a single exothermic crystallization peak contrary to the as cast bulk sample with a different T{sub g} temperature. A single homogeneous amorphous phase revealed by TEM investigations depicts that the faster cooling

  14. Dynamic heterogeneity in life histories

    DEFF Research Database (Denmark)

    Tuljapurkar, Shripad; Steiner, Uli; Orzack, Steven Hecht

    2009-01-01

    generate dynamic heterogeneity: life-history differences produced by stochastic stratum dynamics. We characterize dynamic heterogeneity in a range of species across taxa by properties of the Markov chain: the entropy, which describes the extent of heterogeneity, and the subdominant eigenvalue, which...... distributions of lifetime reproductive success. Dynamic heterogeneity contrasts with fixed heterogeneity: unobserved differences that generate variation between life histories. We show by an example that observed distributions of lifetime reproductive success are often consistent with the claim that little...... or no fixed heterogeneity influences this trait. We propose that dynamic heterogeneity provides a 'neutral' model for assessing the possible role of unobserved 'quality' differences between individuals. We discuss fitness for dynamic life histories, and the implications of dynamic heterogeneity...

  15. 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.

  16. Continua with microstructure

    CERN Document Server

    Capriz, Gianfranco

    1989-01-01

    This book proposes a new general setting for theories of bodies with microstructure when they are described within the scheme of the con­ tinuum: besides the usual fields of classical thermomechanics (dis­ placement, stress, temperature, etc.) some new fields enter the picture (order parameters, microstress, etc.). The book can be used in a semester course for students who have already followed lectures on the classical theory of continua and is intended as an introduction to special topics: materials with voids, liquid crystals, meromorphic con­ tinua. In fact, the content is essentially that of a series of lectures given in 1986 at the Scuola Estiva di Fisica Matematica in Ravello (Italy). I would like to thank the Scientific Committee of the Gruppo di Fisica Matematica of the Italian National Council of Research (CNR) for the invitation to teach in the School. I also thank the Committee for Mathematics of CNR and the National Science Foundation: they have supported my research over many years and given ...

  17. Dewetting on microstructured substrates

    Science.gov (United States)

    Kim, Taehong; Kim, Wonjung

    2016-11-01

    A thin liquid film has an equilibrium thickness in such a way as to minimize the free energy. When a liquid film thickness is out of its equilibrium, the film seeks its equilibrium state, resulting in dynamics of liquid film, which are referred to as wetting and dewetting, depending on the flow direction. We here present a combined experimental and theoretical investigation of dewetting on a substrate with parallel microstructures. Our experiments show that residue may remain on the substrate after dewetting, and residue morphologies can be classified into three modes. Based on our experimental observations, we elucidate how the modes depend on the pattern morphology and contact angle, and develop a model for the contact line motion. Our results provide a basis for controlling the thickness film, which is important for many practical applications such as oil recovery, detergency, lithography, and cleaning. This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (No.2015R1A2A2A04006181).

  18. Collagen Microstructure in the Vocal Ligament: Initial Results on the Potential Effects of Smoking

    Science.gov (United States)

    Kelleher, Jordan E.; Siegmund, Thomas; Chan, Roger W.

    2014-01-01

    Objective This investigation quantitatively characterizes the collagenous microstructure of human vocal ligament specimens excised postmortem from non-smokers and smokers. Study Design Retrospective Cohort Study Methods Second harmonic generation (SHG) imaging was performed at three anatomical locations of vocal ligament specimens: anterior, mid-membranous, and posterior regions. Two microstructural parameters were extracted from the SHG images: (1) normalized fiber density, and (2) fiber dispersion coefficient, quantifying the degree of collagen fiber dispersion about a preferred direction. Results For both the non-smoker and smoker subjects, the fiber dispersion coefficient was heterogeneous. Differences in the collagenous structure of non-smokers and smoker subjects were pronounced at the mid-membranous location. However, the directionality of the heterogeneity in the smoker subjects was opposite to that in the non-smoker subjects. Specifically, the fiber dispersion coefficient in the non-smoker subjects was lower in the midmembranous region (indicating more fiber alignment) than at the anterior/posterior regions, but for the smoker subjects the fiber dispersion coefficient was higher at the mid-membranous region. The normalized fiber density was near constant in the non-smoker subjects, but the smoker subjects had fewer fibers in the mid-membranous region than at the anterior/posterior regions. Conclusion Spatial microstructural variations may exist in the vocal fold ligament both in non-smokers and smokers. Smoking appears to influence the degree and direction of microstructure heterogeneity in the vocal fold ligament. PMID:24473992

  19. Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

    CERN Document Server

    Yang, Hui; Gross, Thilo

    2015-01-01

    One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that heterogeneity can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. Here, we point out that for real world applications, this result should not be regarded independently of the intra-individual heterogeneity between people. Our results show that, if heterogeneity among people is taken into account, networks that are more heterogeneous in connectivity can be more resistant to epidemic spreading. We study a susceptible-infected-susceptible model with adaptive disease avoidance. Results from this model suggest that this reversal of the effect of network heterogeneity is likely to occur in populations in which the individuals are aware of t...

  20. Microstructure Modeling in Integrated Computational Materials Engineering (ICME) Settings: Can HDF5 Provide the Basis for an Emerging Standard for Describing Microstructures?

    Science.gov (United States)

    Schmitz, G. J.

    2016-01-01

    The importance of microstructure simulation in integrated computational materials engineering settings in relation to the added value provided for macroscopic process simulation, as well as the contribution this kind of simulation can make in predicting material properties, are discussed. The roles of microstructure simulation in integrating scales ranging from component/process scales down to atomistic scales, and also in integrating experimental and virtual worlds, are highlighted. The hierarchical data format (HDF5) as a basis for enhancing the interoperability of the heterogeneous range of simulation tools and experimental datasets in the area of computational materials engineering is discussed. Several ongoing developments indicate that HDF5 might evolve into a de facto standard for digital microstructure representation of all length scales.

  1. Elastic wave scattering to characterize heterogeneities in the borehole environment

    Science.gov (United States)

    Tang, Xiao-Ming; Li, Zhen; Hei, Chuang; Su, Yuan-Da

    2016-04-01

    Scattering due to small-scale heterogeneities in the rock formation surrounding a wellbore can significantly change the acoustic waveform from a logging measurement which in turn can be used to characterize the formation heterogeneities. This study simulates the elastic heterogeneity scattering in monopole and dipole acoustic logging and analyse the resulting effects on the waveforms. The results show that significant coda waves are generated in both monopole and dipole waveforms and the dipole coda is dominated by S-to-S scattering, which can be effectively utilized to diagnose the heterogeneity in the rock formation. The coda wave modelling and analysis were used to characterize dipole acoustic data logged before and after fracturing a reservoir interval, with significant coda wave in the after-fracturing data indicating fracturing-induced heterogeneous property change in the rock volume surrounding the borehole.

  2. Heterogeneity of Intellectual Assets

    DEFF Research Database (Denmark)

    Dahlgren, Johan Henrich; Lund Jensen, Rasmus; Valentin, Finn

    2004-01-01

    This paper deals with methodological issues of assessing the composition and level ofheterogeneity of firms' intellectual assets. It develops an original metric - referred to asthe H-index - for measuring heterogeneity using data extracted from patent documents.The main purpose is to improve...... the characterisation of research activities within firmsin the biotechnology sector. Although the H-index grew out of research on biotechfirms, the metric carries broader relevance for all patent-intensive industries. Themeasurement and calculation of the H-index is illustrated using some empiricalexamples from our...

  3. Heterogeneous photonic integrated circuits

    Science.gov (United States)

    Fang, Alexander W.; Fish, Gregory; Hall, Eric

    2012-01-01

    Photonic Integrated Circuits (PICs) have been dichotomized into circuits with high passive content (silica and silicon PLCs) and high active content (InP tunable lasers and transceivers) due to the trade-off in material characteristics used within these two classes. This has led to restrictions in the adoption of PICs to systems in which only one of the two classes of circuits are required to be made on a singular chip. Much work has been done to create convergence in these two classes by either engineering the materials to achieve the functionality of both device types on a single platform, or in epitaxial growth techniques to transfer one material to the next, but have yet to demonstrate performance equal to that of components fabricated in their native substrates. Advances in waferbonding techniques have led to a new class of heterogeneously integrated photonic circuits that allow for the concurrent use of active and passive materials within a photonic circuit, realizing components on a transferred substrate that have equivalent performance as their native substrate. In this talk, we review and compare advances made in heterogeneous integration along with demonstrations of components and circuits enabled by this technology.

  4. Heterogeneous Epidemic Model for Assessing Data Dissemination in Opportunistic Networks

    DEFF Research Database (Denmark)

    Rozanova, Liudmila; Alekseev, Vadim; Temerev, Alexander

    2014-01-01

    In this paper we apply a susceptible-infected-susceptible (SIS) epidemic model to analyse data dissemination in opportunistic networks with heterogeneous setting of transmission parameters, as established in author's previous paper? . We obtained the estimation of the final epidemic size assuming...... that amount of data transferred between network nodes possesses a Pareto distribution, implying scale-free properties. In this context, more heterogeneity in susceptibility means the less severe epidemic progression, and, on the contrary, more heterogeneity in infectivity leads to more severe epidemics...

  5. High-resolution structural and elemental analyses of calcium storage structures synthesized by the noble crayfish Astacus astacus.

    Science.gov (United States)

    Luquet, Gilles; Salomé, Murielle; Ziegler, Andreas; Paris, Céline; Percot, Aline; Dauphin, Yannicke

    2016-11-01

    During premolt, crayfish develop deposits of calcium ions, called gastroliths, in their stomach wall. The stored calcium is used for the calcification of parts of the skeleton regularly renewed for allowing growth. Structural and molecular analyses of gastroliths have been primarily performed on three crayfish species, Orconectes virilis, Procambarus clarkii, and more recently, Cherax quadricarinatus. We have performed high-resolution analyses of gastroliths from the native noble crayfish, Astacus astacus, focusing on the microstructure, the mineralogical and elemental composition and distribution in a comparative perspective. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) observations showed a classical layered microstructure composed of 200-nm diameter granules aligned along fibers. These granules are themselves composed of agglomerated nanogranules of 50nm-mean diameters. Denser regions of bigger fused granules are also present. Micro-Raman spectroscopy show that if A. astacus gastroliths, similarly to the other analyzed gastroliths, are mainly composed of amorphous calcium carbonate (ACC), they are also rich in amorphous calcium phosphate (ACP). The presence of a carotenoid pigment is also observed in A. astacus gastrolith contrary to C. quadricarinatus. Energy-dispersive X-ray spectroscopy (EDX) analyses demonstrate the presence of minor elements such as Mg, Sr, Si and P. The distribution of this last element is particularly heterogeneous. X-ray absorption near edge structure spectroscopy (XANES) reveals an alternation of layers more or less rich in phosphorus evidenced in the mineral phase as well as in the organic matrix in different molecular forms. Putative functions of the different P-comprising molecules are discussed.

  6. Multiscale Analysis of Heterogeneous Media in the Peridynamic Formulation

    CERN Document Server

    Alali, Bacim

    2010-01-01

    A methodology is presented for investigating the dynamics of heterogeneous media using the nonlocal continuum model given by the peridynamic formulation. The approach presented here provides the ability to model the macroscopic dynamics while at the same time resolving the dynamics at the length scales of the microstructure. Central to the methodology is a novel two-scale evolution equation. The rescaled solution of this equation is shown to provide a strong approximation to the actual deformation inside the peridynamic material. The two scale evolution can be split into a microscopic component tracking the dynamics at the length scale of the heterogeneities and a macroscopic component tracking the volume averaged (homogenized) dynamics. The interplay between the microscopic and macroscopic dynamics is given by a coupled system of evolution equations. The equations show that the forces generated by the homogenized deformation inside the medium are related to the homogenized deformation through a history depen...

  7. Geometry of polycrystals and microstructure

    Directory of Open Access Journals (Sweden)

    Ball John M.

    2015-01-01

    Full Text Available We investigate the geometry of polycrystals, showing that for polycrystals formed of convex grains the interior grains are polyhedral, while for polycrystals with general grain geometry the set of triple points is small. Then we investigate possible martensitic morphologies resulting from intergrain contact. For cubic-totetragonal transformations we show that homogeneous zero-energy microstructures matching a pure dilatation on a grain boundary necessarily involve more than four deformation gradients. We discuss the relevance of this result for observations of microstructures involving second and third-order laminates in various materials. Finally we consider the more specialized situation of bicrystals formed from materials having two martensitic energy wells (such as for orthorhombic to monoclinic transformations, but without any restrictions on the possible microstructure, showing how a generalization of the Hadamard jump condition can be applied at the intergrain boundary to show that a pure phase in either grain is impossible at minimum energy.

  8. Stacking faults and microstructural parameters in non-mulberry silk fibres

    Indian Academy of Sciences (India)

    S Divakara; S Madhu; R Somashekar

    2009-11-01

    We have analysed the broadening of X-ray reflections observed in non-mulberry silk fibres in terms of stacking faults and microstructural parameters using a single-order method and have, with these parameters, developed, for the first time, a procedure to compute the whole pattern of these silk fibres. The essential deviations in the values of microstructural parameters obtained from line profile and whole pattern fitting procedures are discussed in this paper.

  9. Evolution of Local Microstructures (ELMS): Spatial Instabilities of Coarsening

    Science.gov (United States)

    Glicksman, Martin E.; Frazier, Donald O.; Rogers, Jan R.; Witherow, William K.; Downey, J. Patton; Facemire, Barbara R.

    1999-01-01

    This work examines the diffusional growth of discrete phase particles dispersed within a matrix. Engineering materials are microstructurally heterogeneous, and the details of the microstructure determine how well that material performs in a given application. Critical to the development of designing multiphase microstructures with long-term stability is the process of Ostwald ripening. Ripening, or phase coarsening, is a diffusion-limited process which arises in polydisperse multiphase materials. Growth and dissolution occur because fluxes of solute, driven by chemical potential gradients at the interfaces of the dispersed phase material, depend on particle size. The kinetics of these processes are "competitive," dictating that larger particles grow at the expense of smaller ones, overall leading to an increase of the average particle size. The classical treatment of phase coarsening was done by Todes, Lifshitz, and Slyozov, (TLS) in the limit of zero volume fraction, V(sub v), of the dispersed phase. Since the publication of TLS theory there have been numerous investigations, many of which sought to describe the kinetic scaling behavior over a range of volume fractions. Some studies in the literature report that the relative increase in coarsening rate at low (but not zero) volume fractions compared to that / 2 1/ 3 predicted by TLS is proportional to V(sub v)(exp 1/2), whereas others suggest V(sub v)(exp 1/3). This issue has been resolved recently by simulation studies at low volume fractions in three dimensions by members of the Rensselaer/MSFC team.

  10. Heterogenous networks and services

    DEFF Research Database (Denmark)

    Tan, Su-En

    the existing generation of technology and presents new technological performance breakthroughs. It is difficult to predict which radical technologies or innovations will result in a market disruption early on in their life cycles. Based on Clayton Christensen’s (Christensen 1997) definition of a disruptive...... of the market. If mainstream technology firms do not address the disruption, it is likely they will fail and the new disruptive firm will grow in size and importance in the industry. As we move to 3G (3rd Generation Mobile Services) and beyond 3G, one of the biggest challenges is to bridge network heterogeneity...... products and services. Schumpeter described the motor of development as the innovation itself. However, business and financial aspects must also be considered as they provide the bottom line for firms in the industry. Standardisation is increasingly required due to the number of different technologies...

  11. Heterogeneous logics of competition

    DEFF Research Database (Denmark)

    Mossin, Christiane

    2015-01-01

    The purpose of the article is to demonstrate that in order to understand competition as a socially organizing phenomenon, we should not examine competition in isolation, but as constellations of heterogeneous logics. More precisely, the article is based on two main theoretical points: (1) Logics...... of competition are only realized as particular forms of social organization by virtue of interplaying with other kinds of logics, like legal logics. (2) Competition logics enjoy a peculiar status in-between constructedness and givenness; although competition depends on laws and mechanisms of socialization, we...... still experience competition as an expression of spontaneous human activities. On the basis of these perspectives, a study of fundamental rights of EU law, springing from the principle of ‘free movement of people’, is conducted. The first part of the empirical analysis seeks to detect the presence...

  12. Heterogeneous logics of competition

    DEFF Research Database (Denmark)

    Mossin, Christiane

    2015-01-01

    The purpose of the article is to demonstrate that in order to understand competition as a socially organizing phenomenon, we should not examine competition in isolation, but as constellations of heterogeneous logics. More precisely, the article is based on two main theoretical points: (1) Logics...... still experience competition as an expression of spontaneous human activities. On the basis of these perspectives, a study of fundamental rights of EU law, springing from the principle of ‘free movement of people’, is conducted. The first part of the empirical analysis seeks to detect the presence...... of a presumed logic of competition within EU law, whereas the second part focuses on particular legal logics. In this respect, the so-called ‘real link criterion’ (determining the access to transnational social rights for certain groups of unemployed people) is given special attention. What is particularly...

  13. Noise and Neuronal Heterogeneity

    CERN Document Server

    Barber, Michael J

    2010-01-01

    We consider signal transaction in a simple neuronal model featuring intrinsic noise. The presence of noise limits the precision of neural responses and impacts the quality of neural signal transduction. We assess the signal transduction quality in relation to the level of noise, and show it to be maximized by a non-zero level of noise, analogous to the stochastic resonance effect. The quality enhancement occurs for a finite range of stimuli to a single neuron; we show how to construct networks of neurons that extend the range. The range increases more rapidly with network size when we make use of heterogeneous populations of neurons with a variety of thresholds, rather than homogeneous populations of neurons all with the same threshold. The limited precision of neural responses thus can have a direct effect on the optimal network structure, with diverse functional properties of the constituent neurons supporting an economical information processing strategy that reduces the metabolic costs of handling a broad...

  14. Space Qualified Heterogeneous Processing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Space Micro proposes to develop a radiation hardened, monolithic, heterogeneous processor for space imaging and radar systems. High performance processors are needed...

  15. Microstructural processes in irradiated materials

    Science.gov (United States)

    Byun, Thak Sang; Morgan, Dane; Jiao, Zhijie; Almer, Jonathan; Brown, Donald

    2016-04-01

    These proceedings contain the papers presented at two symposia, the Microstructural Processes in Irradiated Materials (MPIM) and Characterization of Nuclear Reactor Materials and Components with Neutron and Synchrotron Radiation, held in the TMS 2015, 144th Annual Meeting & Exhibition at Walt Disney World, Orlando, Florida, USA on March 15-19, 2015.

  16. Microstructure modeling in weld metal

    Energy Technology Data Exchange (ETDEWEB)

    David, S.A.; Babu, S.S.

    1995-12-31

    Since microstructure development in the weld metal region is controlled by various physical processes, there is a need for integrated predictive models based on fundamental principles to describe and predict the effect of these physical processes. These integrated models should be based on various tools available for modeling microstructure development in a wide variety of alloy systems and welding processes. In this paper, the principles, methodology, and future directions of modeling thermochemical reactions in liquid, solidification, and solid state transformations are discussed with some examples for low-alloy steel, stainless steel, and Ni-base superalloy. Thermochemical deoxidation reactions in liquid low-alloy steel lead to oxide inclusion formation. This inclusion formation has been modeled by combining principles of ladle metallurgy and overall transformation kinetics. The model`s comparison with the experimental data and the ongoing work on coupling this inclusion model with the numerical models of heat transfer and fluid flow are discussed. Also, recent advances in theoretical and physical modeling of the solidification process are reviewed with regard to predicting the solidification modes, grain structure development, segregation effects, and nonequilibrium solidification in welds. The effects of solid state phase transformations on microstructure development and various methods of modeling these transformations are reviewed. Successful models, based on diffusion-controlled growth and plate growth theories, on microstructure development in low-alloy steel and stainless steel weld metals are outlined. This paper also addresses the importance of advanced analytical techniques to understand the solid state transformation mechanisms in welds.

  17. Nonlinear microstructured polymer optical fibres

    DEFF Research Database (Denmark)

    Frosz, Michael Henoch

    is potentially the case for microstructured polymer optical fibres (mPOFs). Another advantage is that polymer materials have a higher biocompatibility than silica, meaning that it is easier to bond certain types of biosensor materials to a polymer surface than to silica. As with silica PCFs, it is difficult...

  18. Microstructured Surfaces for Enhanced Transmission

    DEFF Research Database (Denmark)

    Ivinskaya, Aliaksandra; Bergmann, René; Kafka, Jan Robert;

    2014-01-01

    Binary microstructures are used to increase transmission of silicon (Si) surfaces in the infrared (IR) range. We consider hexagonal and square lattices with square and round pillars with the finitedifference frequency-domain (FDFD) method. In agreement with theory and previous publications, the h...

  19. Automated microstructural analysis of titanium alloys using digital image processing

    Science.gov (United States)

    Campbell, A.; Murray, P.; Yakushina, E.; Marshall, S.; Ion, W.

    2017-02-01

    Titanium is a material that exhibits many desirable properties including a very high strength to weight ratio and corrosive resistance. However, the specific properties of any components depend upon the microstructure of the material, which varies by the manufacturing process. This means it is often necessary to analyse the microstructure when designing new processes or performing quality assurance on manufactured parts. For Ti6Al4V, grain size analysis is typically performed manually by expert material scientists as the complicated microstructure of the material means that, to the authors knowledge, no existing software reliably identifies the grain boundaries. This manual process is time consuming and offers low repeatability due to human error and subjectivity. In this paper, we propose a new, automated method to segment microstructural images of a Ti6Al4V alloy into its constituent grains and produce measurements. The results of applying this technique are evaluated by comparing the measurements obtained by different analysis methods. By using measurements from a complete manual segmentation as a benchmark we explore the reliability of the current manual estimations of grain size and contrast this with improvements offered by our approach.

  20. Atypical white matter microstructure in left-handed individuals.

    Science.gov (United States)

    McKay, Nicole S; Iwabuchi, Sarina J; Häberling, Isabelle S; Corballis, Michael C; Kirk, Ian J

    2016-04-27

    Information regarding anatomical connectivity in the human brain can be gathered using diffusion tensor imaging (DTI). Fractional anisotropy (FA) is the most commonly derived value, and reflects how strongly directional are the underlying tracts. Differences in FA are thus associated with differences in the underlying microstructure of the brain. The relationships between these differences in microstructure and functional differences in corresponding regions have also been examined. Previous studies have found an effect of handedness on functional lateralization in the brain and corresponding microstructural differences. Here, using tract-based spatial statistics to analyse DTI-derived FA values, we further investigated the structural white matter architecture in the brains of right- and left-handed males. We found significantly higher FA values for left-handed, relatively to right-handed, individuals, in all major lobes, and in the corpus callosum. In support of previous suggestions, we find that there is a difference in the microstructure of white matter in left- and right-handed males that could underpin reduced lateralization of function in left-handed individuals.

  1. Synthesis, Microstructure, and Property of Cr2AlC

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Cr2AlC is an unusual layered ternary ceramic that combines the merits of both metals and ceramics. The salient properties of Cr2AlC are strongly related to its bonding characteristics and microstructures. Synthesis,microstructure, and property of Cr2AlC are reviewed in this paper. First, theoretical calculations and physical properties are introduced. Then, the processing of Cr2AlC ceramic in both bulk form and thin films and their basic mechanical properties are summarized. Atomic-scale characterizations of Cr2AlC, as well as the microstructural relationships among Cr2AlC, Al8Cr5, and AlCr2 were achieved using a series of transmission electron microscopy (TEM) techniques. Moreover, high-temperature oxidation and hot corrosion behaviors of Cr2AlC were investigated by means of thermogravimetric analysis, X-ray diffraction, Raman spectroscopy,scanning electron microscopy, and TEM. Mechanism of the excellent high-temperature corrosion resistance of Cr2AlC is discussed based on systematic microstructural analyses. Finally, concise conclusions are drawn.

  2. Quantitative Microstructural Characterization of Thick Aluminum Plates Heavily Deformed Using Equal Channel Angular Extrusion

    DEFF Research Database (Denmark)

    Mishin, Oleg; Segal, V.M.; Ferrasse, S.

    2012-01-01

    deg rotations about the longitudinal axis. Statistically robust data were obtained in this work using gallium enhanced microscopy and EBSD mapping of large sample areas. For the plate processed using route A, the fraction of high-angle boundaries was found to strongly depend on the inspection plane......A detailed quantitative analysis of the microstructure has been performed in three orthogonal planes of 15-mm-thick aluminum plates heavily deformed via two equal channel angular extrusion (ECAE) routes. One route was a conventional route A with no rotation between passes. Another route involved...... sequential 90 deg rotations about the normal direction (ND) between passes. The microstructure in the center of these plates, and especially the extent of microstructural heterogeneity, has been characterized quantitatively and compared with that in bar samples extruded via either route A or route Bc with 90...

  3. Effects of changes in rock microstructures on permeability: 3-D printing investigation

    Science.gov (United States)

    Head, D.; Vanorio, T.

    2016-07-01

    Rocks are naturally heterogeneous; two rock samples with identical bulk properties can vary widely in microstructure. Understanding how the microstructure and bulk properties of rocks then evolve during experiments and computations simulating diagenesis is inherently a multiscale problem. The advent of modern 3-D printing has provided an unprecedented opportunity to link those scales by combining the strengths of digital and experimental rock physics. In this study, we take a computerized tomography-scanned model of a natural carbonate pore space then iteratively digitally manipulate, 3-D print, and measure the flow properties in the laboratory. This approach allows us to access multiple scales digitally and experimentally and test hypotheses about how changes in rock microstructure due to compaction and dissolution affect bulk transport properties in a repeatable manner.

  4. Microstructural evolution during hot rolling of an AZ31 Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Valle, J.A. del; Perez-Prado, M.T.; Ruano, O.A. [Dept. of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, Madrid (Spain)

    2003-07-01

    The microstructural evolution of a AZ31 Mg alloy during hot rolling has been investigated using optical microscopy and texture (macro and micro) analysis as the main characterization tools. In particular, the differences between the microstructure obtained by unidirectional rolling (UR) and cross rolling (CR) are studied. Significant twinning activity is observed in both cases. Additionally, after cross rolling, a rather heterogeneous microstructure develops, with scattered regions populated by very fine grains. The strong basal fiber texture of the as-received material remains present after both hot rolling schemes. The impossibility to obtain accurate EBSD measurements within the twinned regions suggests that significant localized deformation takes place in those areas. Thus, these regions become preferential sites for the onset of recrystallization due to the increase in the local strain energy. (orig.)

  5. Analysis of heterogeneity of gene products(interferon)expressed in yeast

    Institute of Scientific and Technical Information of China (English)

    王洪海; 高卜渝; 陈佩丽; 董灵; 李育阳

    1995-01-01

    FPLC,SDS-PAGE and Western blot techniques are used to analyse the heterogeneity ofinterferon αA(IFN-αA) expressed in yeast.The heterogeneity consists of (i) the presence of IFN polymer,(ii)partial processing of signal leader peptide and (iii) internal degradation.The reasons for heterogeneity ofgene products in expression system of yeast are analysed.The methods of avoiding heterogeneity,such asdepolymerization,adding inhibitors of protease to the culture supernatant,the oligonucleotide-directed deletionmutagenesis and improvements of fermentation,are discussed.

  6. Comparison of the microstructure and thermal stability of an AZ31 alloy processed by ECAP and large strain hot rolling

    Energy Technology Data Exchange (ETDEWEB)

    Eddahbi, M. [Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, Avda. Gregorio del Amo, 8, 28040 Madrid (Spain); Valle, J.A. del [Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, Avda. Gregorio del Amo, 8, 28040 Madrid (Spain); Perez-Prado, M.T. [Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, Avda. Gregorio del Amo, 8, 28040 Madrid (Spain)]. E-mail: tpprado@cenim.csic.es; Ruano, O.A. [Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, Avda. Gregorio del Amo, 8, 28040 Madrid (Spain)

    2005-11-25

    The aim of this work is to compare the microstructure, the texture, as well as the thermal stability of an AZ31 Mg alloy processed via two different severe plastic deformation processing techniques, namely large strain hot rolling (LSHR) and equal channel angular pressing (ECAP). The microstructure was characterized by optical microscopy and the texture was measured both by X-ray diffraction and electron backscatter diffraction (EBSD). The microstructure obtained via LSHR has average grain sizes around 3 {mu}m, but it is quite heterogeneous. Additionally, a well-defined basal texture develops. ECAP gives rise to a more homogeneous and slightly coarser microstructure, with an average grain size of 7 {mu}m and a shear type texture. The higher resistance of the extruded sample to secondary recrystallization after severe post-deformation annealing is attributed to a texture effect.

  7. PARAMETRIC VARIATIONAL PRINCIPLE BASED ELASTIC-PLASTIC ANALYSIS OF HETEROGENEOUS MATERIALS WITH VORONOI FINITE ELEMENT METHOD

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-wu; WANG Hui

    2006-01-01

    The Voronoi cell finite element method (VCFEM) is adopted to overcome the limitations of the classic displacement based finite element method in the numerical simulation of heterogeneous materials. The parametric variational principle and quadratic programming method are developed for elastic-plastic Voronoi finite element analysis of two-dimensional problems. Finite element formulations are derived and a standard quadratic programming model is deduced from the elastic-plastic equations. Influence of microscopic heterogeneities on the overall mechanical response of heterogeneous materials is studied in detail. The overall properties of heterogeneous materials depend mostly on the size, shape and distribution of the material phases of the microstructure. Numerical examples are presented to demonstrate the validity and effectiveness of the method developed.

  8. [Neuromyelitis optica: problems of heterogeneity and systematization].

    Science.gov (United States)

    Totolian, N A; Prakhova, L N; Sofienko, L Iu; Kataeva, G V; Il'ves, A G; Stoliarov, I D; Skoromets, A A

    2009-01-01

    Prospective-retrospective data on 10 cases of neuromyelitis optica (NO) have been analyzed. Demographic and clinical features of patients with primary NO as well as NO comorbid with other organospecific disorders are discussed. Magnetic-resonance imaging data of the brain and spinal cord are summarized and discussed in the context of its heterogeneity. Positron emission tomography with the functional imaging of the brain performed in 3 patients revealed changes in glucose metabolism in the brain regions corresponding to deficits in motor and sensory functional systems. The issues of additional laboratory analyses, including those of cerebrospinal fluid, are reviewed.

  9. Query Expansion Using Heterogeneous Thesauri.

    Science.gov (United States)

    Mandala, Rila; Tokunaga, Takenobu; Tanaka, Hozumi

    2000-01-01

    Proposes a method to improve the performance of information retrieval systems by expanding queries using heterogeneous thesauri. Experiments show that using heterogeneous thesauri with an appropriate weighting method results in better retrieval performance than using only one type of thesaurus. (Author/LRW)

  10. Fiscal Consolidations and Heterogeneous Expectations

    NARCIS (Netherlands)

    C. Hommes; J. Lustenhouwer; K. Mavromatis

    2015-01-01

    We analyze fiscal consolidations using a New Keynesian model where agents have heterogeneous expectations and are uncertain about the composition of consoidations. Heterogeneity in expectations may amplify expansions, stabilizing thus the debt-to-GDP ratio faster under tax based consolidations, in t

  11. Coordination Frictions and Job Heterogeneity

    DEFF Research Database (Denmark)

    Kennes, John; le Maire, Christian Daniel

    This paper develops and extends a dynamic, discrete time, job to worker matching model in which jobs are heterogeneous in equilibrium. The key assumptions of this economic environment are (i) matching is directed and (ii) coordination frictions lead to heterogeneous local labor markets. We de- rive...

  12. Query Expansion Using Heterogeneous Thesauri.

    Science.gov (United States)

    Mandala, Rila; Tokunaga, Takenobu; Tanaka, Hozumi

    2000-01-01

    Proposes a method to improve the performance of information retrieval systems by expanding queries using heterogeneous thesauri. Experiments show that using heterogeneous thesauri with an appropriate weighting method results in better retrieval performance than using only one type of thesaurus. (Author/LRW)

  13. Through-Thickness Variations of Deformed and Annealed Microstructures in ECAE-Processed Copper

    DEFF Research Database (Denmark)

    Mishin, Oleg; Bowen, Jacob R.

    2009-01-01

    Through-thickness variations of the microstructure in copper processed using equal channel angular extrusion (ECAE) to a strain of ~10 without rotations between passes have been investigated in deformed and partially recrystallized conditions. It is found that the through-thickness heterogeneity...... strain. Compared to other inspected layers the bottom part of the billet was less refined after ECAE and remained less recrystallized after annealing....

  14. Heterogeneity: multilingualism and democracy

    Directory of Open Access Journals (Sweden)

    Hans-Jürgen Krumm

    2004-01-01

    Full Text Available Linguistic diversity and multilingualism on the part of individuals are aprerequisite and a constitutive condition of enabling people to live togetherin a world of growing heterogeneity. Foreign language teaching plays animportant part in democratic education because it can be seen as a trainingin respecting otherness and developing an intercultural, non-ethnocentricperception and attitude. This is all the more important because of the neces-sity of integrating children from migrant families into school life.My article argues that language education policy has to take this per-spective into account, i.e., of establishing a planned diversification so thatpupils (and their parents will not feel satisfied with learning English only,but also become motivated to learn languages of their own neighbourhood,such as migrant and minority languages. However, in order to make use ofthe linguistic resources in the classroom, relating it to the democratic impetusof foreign language education, it is necessary to revise existing languagepolicies and to develop a multilingual perspective for all educational institutions.

  15. Heterogeneous recording media

    Science.gov (United States)

    Sukhanov, Vitaly I.

    1991-02-01

    The paper summarizes the results of investigations performed to obtain deep 3-D holograms with 102 i0 mkm physical thickness allowing the postexposure amplification and the a posteriori changing of the grating parameters. This aim has been achieved by developing heterogeneous systems on the basis of porous glass with light-sensitive compositions introduced into it. 1. INTRODUCTION. LIGHT-SENSITIVE MEDIA FOR 3-D HOLOGRAMS RECORDING. The 3-D holograms have many useful properties: very high diffraction efficiency angular and spectral selectivity but low level of noise. It shoud be noted that in this case deep 3-D holograms are dealt with whose physical thickness is as high as 102 -i mkm. Such hologram recording is usually done using homogeneous light-sensitive media for example dyed acid-halide and electrooptical crystals photochrome glass photostructurized polimer compositions and so on. The nature of photophisical and photochemical processes responsible for the light sensitivity of these materials exclude the possibility of post-exposure treatment. This does not allow to enhance the recorded holograms and considerably hampers their fixing or makes it practically impossible. The object of our work is to create the media which are quite suitable for two-stage processes of the deep hologram formation with post-exposure processing. Such material must satisfy the following requirements: a)they must have high permeability for the developing substances in order to make the development duration suitable for practical applications b)they must be shrinkproof to prevent deformation of the

  16. Parsing Heterogeneous Striatal Activity

    Directory of Open Access Journals (Sweden)

    Kae Nakamura

    2017-05-01

    Full Text Available The striatum is an input channel of the basal ganglia and is well known to be involved in reward-based decision making and learning. At the macroscopic level, the striatum has been postulated to contain parallel functional modules, each of which includes neurons that perform similar computations to support selection of appropriate actions for different task contexts. At the single-neuron level, however, recent studies in monkeys and rodents have revealed heterogeneity in neuronal activity even within restricted modules of the striatum. Looking for generality in the complex striatal activity patterns, here we briefly survey several types of striatal activity, focusing on their usefulness for mediating behaviors. In particular, we focus on two types of behavioral tasks: reward-based tasks that use salient sensory cues and manipulate outcomes associated with the cues; and perceptual decision tasks that manipulate the quality of noisy sensory cues and associate all correct decisions with the same outcome. Guided by previous insights on the modular organization and general selection-related functions of the basal ganglia, we relate striatal activity patterns on these tasks to two types of computations: implementation of selection and evaluation. We suggest that a parsing with the selection/evaluation categories encourages a focus on the functional commonalities revealed by studies with different animal models and behavioral tasks, instead of a focus on aspects of striatal activity that may be specific to a particular task setting. We then highlight several questions in the selection-evaluation framework for future explorations.

  17. Dynamic spreading behavior of homogeneous and heterogeneous networks

    Institute of Scientific and Technical Information of China (English)

    XIA Chengyi; LIU Zhongxin; CHEN Zengqiang; YUAN Zhuzhi

    2007-01-01

    The detailed investigation of the dynamic epidemic spreading on homogeneous and heterogeneous networks was carried out. After the analysis of the basic epidemic models, the susceptible-infected-susceptible (SIS) model on homogenous and heterogeneous networks is established, and the dynamical evolution of the density of the infected individuals in these two different kinds of networks is analyzed theoretically. It indicates that heterogeneous networks are easier to propagate for the epidemics and the leading spreading behavior is dictated by the exponential increasing in the initial outbreaks. Large-scale simulations display that the infection is much faster on heterogeneous networks than that on homogeneous ones. It means that the network topology can have a significant effect on the epidemics taking place on complex networks. Some containment strategies of epidemic outbreaks are presented according to the theoretical analyses and numerical simulations.

  18. Synthesis of Microstructures and the Relationship between Microstructure and Properties.

    Science.gov (United States)

    1980-03-01

    Cincinnati by Prof. Stephen D. Antolovich . iY II-7.Y -4J TABLE OF CONTENTS PAGE I INTRODUCTION 1 II MICROSTRUCTURE MECHANICAL PROPERTY CORRELATIONS IN...for other steels. The LCF results were used to make a theoretical prediction of FCP behavior using a model developed by S. Antolovich and some of his...be published in the Proceedings of the Fourth International Titanium Conference, Kyoto, Japan, 1980. 79. S.D. Antolovich , "Fatigue Crack Propagation

  19. LDRD final report : mesoscale modeling of dynamic loading of heterogeneous materials.

    Energy Technology Data Exchange (ETDEWEB)

    Robbins, Joshua; Dingreville, Remi Philippe Michel; Voth, Thomas Eugene; Furnish, Michael David

    2013-12-01

    Material response to dynamic loading is often dominated by microstructure (grain structure, porosity, inclusions, defects). An example critically important to Sandia's mission is dynamic strength of polycrystalline metals where heterogeneities lead to localization of deformation and loss of shear strength. Microstructural effects are of broad importance to the scientific community and several institutions within DoD and DOE; however, current models rely on inaccurate assumptions about mechanisms at the sub-continuum or mesoscale. Consequently, there is a critical need for accurate and robust methods for modeling heterogeneous material response at this lower length scale. This report summarizes work performed as part of an LDRD effort (FY11 to FY13; project number 151364) to meet these needs.

  20. Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

    Science.gov (United States)

    Clifford, Jallisa Janet

    Heterogeneous materials are increasingly used in a wide range of applications such as aerospace, civil infrastructure, fuel cells and many others. The ability to take properties from two or more materials to create a material with properties engineered to needs is always very attractive. Hence heterogeneous materials are evolving into more complex formulations in multiple disciplines. Design of microstructure at multiple scales control the global functional properties of these materials and their structures. However, local microstructural changes do not directly cause a proportional change to the global properties (such as strength and stiffness). Instead, local changes follow an evolution process including significant interactions. Therefore, in order to understand property evolution of engineered materials, microstructural changes need to be effectively captured. Characterizing these changes and representing them by material variables will enable us to further improve our material level understanding. In this work, we will demonstrate how microstructural features of heterogeneous materials can be described quantitatively using broadband dielectric spectroscopy (BbDS). The frequency dependent dielectric properties can capture the change in material microstructure and represent these changes in terms of material variables, such as complex permittivity. These changes in terms of material properties can then be linked to a number of different conditions, such as increasing damage due to impact or fatigue. Two different broadband dielectric spectroscopy scanning modes are presented: bulk measurements and continuous scanning to measure dielectric property change as a function of position across the specimen. In this study, we will focus on ceramic materials and fiber reinforced polymer matrix composites as test bed material systems. In the first part of the thesis, we will present how different micro-structural design of porous ceramic materials can be captured

  1. Formation of a two-phase microstructure in Fe-Cr-Ni alloy during directional solidification

    Science.gov (United States)

    Fu, J. W.; Yang, Y. S.; Guo, J. J.; Ma, J. C.; Tong, W. H.

    2008-12-01

    The formation and evolution of a two-phase coupled growth microstructure in AISI 304 stainless steel are investigated using a quenching method during directional solidification. It is found that the two-phase microstructure, which is composed of coupled growth of thin lathy delta ferrite (δ) and austenite (γ), forms from the melt first during solidification. As solidification proceeds, the retained liquid transforms into austenite directly. On cooling, the subsequent incomplete solid-state transformation from ferrite to austenite results in the disappearance of the thinner lathy delta ferrite, and the final two-phase coupled growth microstructure is formed. The formation mechanism of the two-phase coupled growth microstructure is analyzed theoretically based on the nucleation and constitutional undercooling (NCU) criterion. Transmission electron microscope (TEM) and EDS analyses were carried out to identify the phases and determine the phase composition, respectively.

  2. In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

    Directory of Open Access Journals (Sweden)

    S. Hesamodin Talebi

    2017-09-01

    Full Text Available Phase transformations during non-isothermal tempering of bainitic or martensitic microstructures obtained after quenching of a medium-carbon low-alloy steel was studied. The microstructures correspond to different locations of an as-quenched large-sized forged ingot used as a die material in the automotive industry. High-resolution dilatometry experiments were conducted to simulate the heat treatment process, as well as to investigate different phenomena occurring during non-isothermal tempering. The microstructures were characterized using optical and scanning electron microscopy. Dilatometry analyses demonstrated that tempering behavior varied significantly from bainitic to martensitic microstructures. Retained austenite, which exists between bainitic ferrite sheaves, decomposes to lower bainite causing a remarkable volume increase. It was found that this decomposition finishes below 386 °C. By contrast, martensite tempering was accompanied with a volume decrease due to the decomposition of medium-carbon martensite to low carbon martensite and carbides.

  3. Individual Grain Orientation and Heterogeneous Deformation in Cold-deformed Interstitial-Free Sheet Steel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The cold rolling deformation textural evolution of an interstitial-free (IF) steel sheet is investigated by experiment and simulation. The microstructure of the IF steel is observed by transmission electron microscopy (TEM). The relationship between the deformation behavior of individual grain and the grain orientation are connected by Taylor factor M. The results show that the grains with higher Taylor factor are deformed slighter than those with lower ones. By considering the heterogeneous deformation, the texture simulation result can be greatly improved.

  4. Food microstructure and starch digestion.

    Science.gov (United States)

    Singh, Jaspreet; Kaur, Lovedeep; Singh, Harjinder

    2013-01-01

    Microstructural characteristics of starch-based natural foods such as parenchyma or cotyledon cell shape, cell size and composition, and cell wall composition play a key role in influencing the starch digestibility during gastrointestinal digestion. The stability of cell wall components and the arrangement of starch granules in the cells may affect the free access of amylolytic enzymes during digestion. Commonly used food processing techniques such as thermal processing, extrusion cooking, and post-cooking refrigerated storage alter the physical state of starch (gelatinization, retrogradation, etc.) and its digestibility. Rheological characteristics (viscosity) of food affect the water availability during starch hydrolysis and, consequently, the absorption of digested carbohydrates in the gastrointestinal tract. The nonstarch ingredients and other constituents present in food matrix, such as proteins and lipids interact with starch during processing, which leads to an alteration in the overall starch digestibility and physicochemical characteristics of digesta. Starch digestibility can be controlled by critically manipulating the food microstructure, processing techniques, and food composition.

  5. Microstructural degradation in compound tubes

    Energy Technology Data Exchange (ETDEWEB)

    Salonen, J.; Auerkari, P. [VTT Manufacturing Technology, Espoo (Finland)

    1996-12-31

    In order to quantify microstructural degradation at high temperatures, samples of SA 210 / AISI 304 L compound tube material were annealed in the temperature range 540-720 deg C for 1 to 1 000 hours. The hardness of the annealed material was measured and the micro structure of the samples was investigated with optical and scanning electron microscopy. Microstructural degradation was characterised by the carbide structure in the ferritic-pearlitic base material and by the depth of decarburised and carburised zones of the compound tube interface. The observed changes were quantified in terms of their time and temperature dependence and diffusion coefficients of the process. The results can be used in estimating the extent of thermal exposure of high-temperature components after long-term service or after incidences of overheating. (orig.) (4 refs.)

  6. Microstructural processes in irradiated materials

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang; Morgan, Dane; Jiao, Zhijie; Almer, Jonathan; Brown, Donald

    2016-04-01

    This is an editorial article (preface) for the publication of symposium papers in the Journal of Nuclear materials: These proceedings contain the papers presented at two symposia, the Microstructural Processes in Irradiated Materials (MPIM) and Characterization of Nuclear Reactor Materials and Components with Neutron and Synchrotron Radiation, held in the TMS 2015, 144th Annual Meeting & Exhibition at Walt Disney World, Orlando, Florida, USA on March 15–19, 2015.

  7. Microstructure of a magnetotail fireball

    Science.gov (United States)

    Coroniti, F. V.; Scarf, F. L.; Frank, L. A.; Lepping, R. P.

    1977-01-01

    We use high time resolution data from the magnetometer, LEPEDEA and plasma wave analyzer on IMP-7 to examine the microstructure of a long-duration magnetotail fireball event observed during an extended quiet period on November 9, 1972. We demonstrate that the magnetic field is turbulent with fluctuation time scales down to several seconds. These findings suggest that the magnetic merging process may be a highly turbulent one, possibly associated with a form of the tearing mode instability.

  8. Effect of grain boundary microstructure on superplastic deformation of Al-Li-Cu-Mg-Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, S.; Yoshimura, T.; Tsurekawa, S.; Watanabe, T. [Tohoku Univ., Sendai (Japan). Dept. of Machine Intelligence and Syst. Eng.

    1999-07-01

    It is common knowledge that grain boundary sliding (GBS) is the most important deformation mechanism for superplastic deformation. In this investigation, Al-Li-Cu-Mg-Zr alloys having two distinct microstructures were produced to examine the effect of grain boundary (GB) microstructure on superplastic deformation. The effective GB microstructure to develop the superplastic deformation is discussed. Specimens with homogeneous and {l_brace}011{r_brace} textured grains, including high frequency of low-angle GBs showed superplastic behavior. The texture was weakened and most of low-angle GBs were changed into random GBs during deformation. Mean grain size increased slightly with deformation. On the other hand, specimens with heterogeneous and randomly oriented grains, with a high frequency of random GBs resulted in nonsuperplastic behavior. This microstructure was essentially unchanged by deformation. Extensive cavitation at GB triple junctions was also observed after superplastic deformation. In particular, cavities were most likely to form at the triple junctions composed of two or more random GBs. We will discuss the development of superplasticity through the optimization of GB microstructures in polycrystalline materials. (orig.)

  9. Computational study of filler microstructure and effective property relations in dielectric composites

    Science.gov (United States)

    Wang, Yu U.; Tan, Daniel Q.

    2011-05-01

    Phase field modeling and computer simulation is employed to study the relations between filler microstructures and effective properties of dielectric composites. The model solves electrostatic equations in terms of polarization vector field in reciprocal space using a fast Fourier transform technique and parallel computing algorithm. Composites composed of linear constituent phases of different dielectric constants are considered. Interphase boundary conditions are automatically taken into account without explicitly tracking interphase interfaces in the composites. Various factors associated with filler microstructures are systematically investigated, including dielectric constant mismatch between fillers and matrix, particle size, shape, orientation, volume fraction, and spatial arrangement as well as directional alignment. Heterogeneous distributions of polarization, charge density, and local electric field are calculated for each composite microstructure, based on which effective dielectric constant and dielectric anisotropy of the composites are determined. It is found that electrostatic interactions among high-dielectric-constant fillers embedded in low-dielectric-constant matrix play critical roles in determining the composite properties, which sensitively depend on filler arrangement and, especially, directional alignment into fibrous microstructures (chains). Such microstructurally engineered composites, whose fillers are not randomly dispersed, exhibit strong dielectric anisotropy despite all constituent components being isotropic.

  10. Characterization of phase transformation behaviour and microstructural development of electroless Ni-B coating

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Soupitak, E-mail: soupitak.pal@gmail.com [Department of Materials Engineering, Indian Institute of Science, C.V. Raman Avenue, Bangalore 560012 (India); Verma, Nisha; Jayaram, Vikram [Department of Materials Engineering, Indian Institute of Science, C.V. Raman Avenue, Bangalore 560012 (India); Biswas, Sanjay Kumar [Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012 (India); Riddle, Yancy [UCT Coatings Inc, FL (United States)

    2011-10-25

    Highlights: {yields} Phase transformation behaviour of electroless Ni-B coating in conjunction with microstructural development was studied. {yields} As deposited coating exhibits a novel phase separated microstructure of various length scales. {yields} Crystallization behaviour of the coating is strongly composition dependent. {yields} Deposition process itself induces compositional heterogeneity in the coating. - Abstract: Phase transformation behaviour of amorphous electroless Ni-B coating with a targeted composition of Ni-6 wt% B is characterized in conjunction with microstructural development and hardness. Microscopic observations of the as-deposited coating display a novel microstructure which is already phase separated at multiple length scales. Spherical colonies of {approx}5 {mu}m consist of 2-3 {mu}m nodular regions which are surrounded by {approx}2-3 {mu}m region that contains fine bands ranging from 10 to 70 nm in width. The appearance of three crystalline phases in this binary system at different stages of heat treatment and the concomitant variation in hardness are shown to arise from nanoscale fluctuations in the as-deposited boron content from 4 to 8 wt%. High temperature annealing reveals continuous crystallization up to 430 deg. C, overlapping with the domain of B loss due to diffusion into the substrate. The implications of such a microstructure for optimal heat treatment procedures are discussed.

  11. Understanding heterogeneity of social preferences for fire prevention management

    DEFF Research Database (Denmark)

    Varela, Elsa; Jacobsen, Jette Bredahl; Soliño, Mario

    2014-01-01

    studies look at public preferences for fire suppression, this study analyses the heterogeneity of social preferences for fire prevention. The visual characteristics of fire prevention structures are very familiar to respondents, but their management is unfamiliar, which raises specific attention in terms...

  12. Homogeneous, Heterogeneous, and Enzymatic Catalysis.

    Science.gov (United States)

    Oyama, S. Ted; Somorjai, Gabor A.

    1988-01-01

    Discusses three areas of catalysis: homegeneous, heterogeneous, and enzymatic. Explains fundamentals and economic impact of catalysis. Lists and discusses common industrial catalysts. Provides a list of 107 references. (MVL)

  13. Heterogeneity, correlations and financial contagion

    OpenAIRE

    FABIO CACCIOLI; Thomas A. Catanach; J Doyne Farmer

    2011-01-01

    We consider a model of contagion in financial networks recently introduced in Gai, P. and Kapadia, S. [Contagion in financial networks, Proc. R. Soc. A 466(2120) (2010) 2401–2423], and we characterize the effect of a few features empirically observed in real networks on the stability of the system. Notably, we consider the effect of heterogeneous degree distributions, heterogeneous balance sheet size and degree correlations between banks. We study the probability of contagion conditional on t...

  14. Engineering of Metal Microstructures; Process-Microstructure-Property Relationships for Electrodeposits

    DEFF Research Database (Denmark)

    Jensen, Jens Dahl

    2002-01-01

    and concentration of additives, current density, and mass transport. The grown films were analysed by a variety of characterisation techniques - including optical light microscopy, electron microscopy, atomic force microscopy, X-ray diffraction, thin film tensile testing, and nano-indentation. Studies of anomalous......-Fe compositionally modulated alloys (CMA) possible. Ni membranes were deposited from a Watts type electrolyte with or without the sulphur-containing additive sodium-saccharin. This additive caused a strong levelling as well as a grain refining effect on Ni-deposits. However, additional microstructural defects were...... introduced in the deposits with the use of sodium-saccharin, which led to embrittlement of the deposits. By using ultrasonic streaming near the cathode during electrodeposition in the Watts type electrolyte, improved material distribution in machined 3-dimensional groove geometries was observed...

  15. Force spectroscopy of complex biopolymers with heterogeneous elasticity

    Science.gov (United States)

    Valdman, David; Lopez, Benjamin J.

    2013-01-01

    Cellular biopolymers can exhibit significant compositional heterogeneities as a result of the non-uniform binding of associated proteins, the formation of microstructural defects during filament assembly, or the imperfect bundling of filaments into composite structures of variable diameter. These can lead to significant variations in the local mechanical properties of biopolymers along their length. Existing spectral analysis methods assume filament homogeneity and therefore report only a single average stiffness for the entire filament. However, understanding how local effects modulate biopolymer mechanics in a spatially resolved manner is essential to understanding how binding and bundling proteins regulate biopolymer stiffness and function in cellular contexts. Here, we present a new method to determine the spatially varying material properties of individual complex biopolymers from the observation of passive thermal fluctuations of the filament conformation. We develop new statistical mechanics-based approaches for heterogeneous filaments that estimate local bending elasticities as a function of the filament arc-length. We validate this methodology using simulated polymers with known stiffness distributions, and find excellent agreement between derived and expected values. We then determine the bending elasticity of microtubule filaments of variable composition generated by repeated rounds of tubulin polymerization using either GTP or GMPCPP, a nonhydrolyzable GTP analog. Again, we find excellent agreement between mechanical and compositional heterogeneities. PMID:24049545

  16. Bridging Social Capital in Online Communities: Heterogeneity and Social Tolerance of Online Game Players in Japan

    Science.gov (United States)

    Kobayashi, Tetsuro

    2010-01-01

    This article examines the democratic potential of online communities by investigating the influence of network heterogeneity on social tolerance in an online gaming environment. Online game communities are potential sources of bridging social capital because they tend to be relatively heterogeneous. Causal analyses are conducted using structural…

  17. Sproglig Metode og Analyse

    DEFF Research Database (Denmark)

    le Fevre Jakobsen, Bjarne

    Publikationen indeholder øvematerialer, tekster, powerpointpræsentationer og handouts til undervisningsfaget Sproglig Metode og Analyse på BA og tilvalg i Dansk/Nordisk 2010-2011......Publikationen indeholder øvematerialer, tekster, powerpointpræsentationer og handouts til undervisningsfaget Sproglig Metode og Analyse på BA og tilvalg i Dansk/Nordisk 2010-2011...

  18. The microstructure and micromechanics of the tendon-bone insertion

    Science.gov (United States)

    Rossetti, L.; Kuntz, L. A.; Kunold, E.; Schock, J.; Müller, K. W.; Grabmayr, H.; Stolberg-Stolberg, J.; Pfeiffer, F.; Sieber, S. A.; Burgkart, R.; Bausch, A. R.

    2017-06-01

    The exceptional mechanical properties of the load-bearing connection of tendon to bone rely on an intricate interplay of its biomolecular composition, microstructure and micromechanics. Here we identify that the Achilles tendon-bone insertion is characterized by an interface region of ~500 μm with a distinct fibre organization and biomolecular composition. Within this region, we identify a heterogeneous mechanical response by micromechanical testing coupled with multiscale confocal microscopy. This leads to localized strains that can be larger than the remotely applied strain. The subset of fibres that sustain the majority of loading in the interface area changes with the angle of force application. Proteomic analysis detects enrichment of 22 proteins in the interfacial region that are predominantly involved in cartilage and skeletal development as well as proteoglycan metabolism. The presented mechanisms mark a guideline for further biomimetic strategies to rationally design hard-soft interfaces.

  19. The study of microstructure and mechanical properties of twin-roll cast AZ31 magnesium alloy after constrained groove pressing

    Science.gov (United States)

    Zimina, M.; Bohlen, J.; Letzig, D.; Kurz, G.; Cieslar, M.; Zník, J.

    2014-08-01

    Microstructure investigation and microhardness mapping were done on the material with ultra-fine grained structure prepared by constrained groove pressing of twin-roll cast AZ31 magnesium strips. The microstructure observations showed significant drop of the grain size from 200 gm to 20 gm after constrained groove pressing. Moreover, the heterogeneities in the microhardness along the cross-section observed in the as-cast strip were replaced by the bands of different microhardness in the constrained groove pressed material. It is shown that the constrained groove pressing technique is a good tool for the grain refinement of magnesium alloys.

  20. Fluctuation Analyses for Pattern Classification in Nondestructive Materials Inspection

    Directory of Open Access Journals (Sweden)

    A. P. Vieira

    2010-01-01

    Full Text Available We review recent work on the application of fluctuation analyses of time series for pattern classification in nondestructive materials inspection. These analyses are based on the evaluation of time-series fluctuations across time intervals of increasing size, and were originally introduced in the study of fractals. A number of examples indicate that this approach yields relevant features allowing the successful classification of patterns such as (i microstructure signatures in cast irons, as probed by backscattered ultrasonic signals; (ii welding defects in metals, as probed by TOFD ultrasonic signals; (iii gear faults, based on vibration signals; (iv weld-transfer modes, as probed by voltage and current time series; (v microstructural composition in stainless steel, as probed by magnetic Barkhausen noise and magnetic flux signals.

  1. Dealing with spatial heterogeneity

    Science.gov (United States)

    Marsily, Gh.; Delay, F.; Gonçalvès, J.; Renard, Ph.; Teles, V.; Violette, S.

    2005-03-01

    Heterogeneity can be dealt with by defining homogeneous equivalent properties, known as averaging, or by trying to describe the spatial variability of the rock properties from geologic observations and local measurements. The techniques available for these descriptions are mostly continuous Geostatistical models, or discontinuous facies models such as the Boolean, Indicator or Gaussian-Threshold models and the Markov chain model. These facies models are better suited to treating issues of rock strata connectivity, e.g. buried high permeability channels or low permeability barriers, which greatly affect flow and, above all, transport in aquifers. Genetic models provide new ways to incorporate more geology into the facies description, an approach that has been well developed in the oil industry, but not enough in hydrogeology. The conclusion is that future work should be focused on improving the facies models, comparing them, and designing new in situ testing procedures (including geophysics) that would help identify the facies geometry and properties. A world-wide catalog of aquifer facies geometry and properties, which could combine site genesis and description with methods used to assess the system, would be of great value for practical applications. On peut aborder le problème de l'hétérogénéité en s'efforçant de définir une perméabilité équivalente homogène, par prise de moyenne, ou au contraire en décrivant la variation dans l'espace des propriétés des roches à partir des observations géologiques et des mesures locales. Les techniques disponibles pour une telle description sont soit continues, comme l'approche Géostatistique, soit discontinues, comme les modèles de faciès, Booléens, ou bien par Indicatrices ou Gaussiennes Seuillées, ou enfin Markoviens. Ces modèles de faciès sont mieux capables de prendre en compte la connectivité des strates géologiques, telles que les chenaux enfouis à forte perméabilité, ou au contraire les faci

  2. Catalytic Activity Control via Crossover between Two Different Microstructures

    KAUST Repository

    Zhou, Yuheng

    2017-09-08

    Metal nanocatalysts hold great promise for a wide range of heterogeneous catalytic reactions, while the optimization strategy of catalytic activity is largely restricted by particle size or shape control. Here, we demonstrate that a reversible microstructural control through the crossover between multiply-twinned nanoparticle (MTP) and single crystal (SC) can be readily achieved by solvent post-treatment on gold nanoparticles (AuNPs). Polar solvents (e.g. water, methanol) direct the transformation from MTP to SC accompanied by the disappearance of twinning and stacking faults. A reverse transformation from SC to MTP is achieved in non-polar solvent (e.g. toluene) mixed with thiol ligands. The transformation between two different microstructures is directly observed by in-situ TEM and leads to a drastic modulation of catalytic activity towards the gas-phase selective oxidation of alcohols. There is a quasi-linear relationship between TOFs and MTP concentrations. Based on the combined experimental and theoretical investigations of alcohol chemisorption on these nanocatalysts, we propose that the exposure of {211}-like microfacets associated with twin boundaries and stack faults accounts for the strong chemisorption of alcohol molecules on MTP AuNPs and thus the exceptionally high catalytic activity.

  3. Thermal conductivity of heterogeneous LWR MOX fuels

    Science.gov (United States)

    Staicu, D.; Barker, M.

    2013-11-01

    It is generally observed that the thermal conductivity of LWR MOX fuel is lower than that of pure UO2. For MOX, the degradation is usually only interpreted as an effect of the substitution of U atoms by Pu. This hypothesis is however in contradiction with the observations of Duriez and Philiponneau showing that the thermal conductivity of MOX is independent of the Pu content in the ranges 3-15 and 15-30 wt.% PuO2 respectively. Attributing this degradation to Pu only implies that stoichiometric heterogeneous MOX can be obtained, while we show that any heterogeneity in the plutonium distribution in the sample introduces a variation in the local stoichiometry which in turn has a strong impact on the thermal conductivity. A model quantifying this effect is obtained and a new set of experimental results for homogeneous and heterogeneous MOX fuels is presented and used to validate the proposed model. In irradiated fuels, this effect is predicted to disappear early during irradiation. The 3, 6 and 10 wt.% Pu samples have a similar thermal conductivity. Comparison of the results for this homogeneous microstructure with MIMAS (heterogeneous) fuel of the same composition showed no difference for the Pu contents of 3, 5.9, 6, 7.87 and 10 wt.%. A small increase of the thermal conductivity was obtained for 15 wt.% Pu. This increase is of about 6% when compared to the average of the values obtained for 3, 6 and 10 wt.% Pu. For comparison purposes, Duriez also measured the thermal conductivity of FBR MOX with 21.4 wt.% Pu with O/M = 1.982 and a density close to 95% TD and found a value in good agreement with the estimation obtained using the formula of Philipponneau [8] for FBR MOX, and significantly lower than his results corresponding to the range 3-15 wt.% Pu. This difference in thermal conductivity is of about 20%, i.e. higher than the measurement uncertainties.Thus, a significant difference was observed between FBR and PWR MOX fuels, but was not explained. This difference

  4. Control of Cast Iron Microstructure

    Science.gov (United States)

    Graham, J.; Lillybeck, N.; Franco, N.; Stefanescu, D. M.

    1985-01-01

    The use of microgravity for industrial research in the processing of cast iron was investigated. Solidification experiments were conducted using the KC-135 and F-104 aircraft, and an experiment plan was developed for follow-on experiments using the Shuttle. Three areas of interest are identified: (1) measurement of thermophysical properties in the melt; (2) understanding of the relative roles of homogeneous nucleation, grain multiplication, and innocultants in forming the microstructure; and (3) exploring the possibility of obtaining an aligned graphite structure in hypereutectic Fe, Ni, and Co.

  5. Brain Microstructural Abnormalities Are Related to Physiological Alterations in End-Stage Renal Disease.

    Directory of Open Access Journals (Sweden)

    Zhigang Bai

    Full Text Available To study whole-brain microstructural alterations in patients with end-stage renal disease (ESRD and examine the relationship between brain microstructure and physiological indictors in the disease.Diffusion tensor imaging data were collected from 35 patients with ESRD (28 men, 18-61 years and 40 age- and gender-matched healthy controls (HCs, 32 men, 22-58 years. A voxel-wise analysis was then used to identify microstructural alterations over the whole brain in the ESRD patients compared with the HCs. Multiple biochemical measures of renal metabolin, vascular risk factors, general cognitive ability and dialysis duration were correlated with microstructural integrity for the patients.Compared to the HCs, the ESRD patients exhibited disrupted microstructural integrity in not only white matter (WM but also gray matter (GM regions, as characterized by decreased fractional anisotropy (FA and increased mean diffusivity (MD, axial diffusivity (AD and radial diffusivity (RD. Further correlation analyses revealed that the in MD, AD and RD values showed significantly positive correlations with the blood urea nitrogen in the left superior temporal gyrus and significantly negative correlations with the calcium levels in the left superior frontal gyrus (orbital part in the patients.Our findings suggest that ESRD is associated with widespread diffusion abnormalities in both WM and GM regions in the brain, and microstructural integrity of several GM regions are related to biochemical alterations in the disease.

  6. Influence of Manufacturing Processes and Microstructures on the Performance and Manufacturability of Advanced High Strength Steels

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kyoo Sil; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2009-10-01

    Advanced high strength steels (AHSS) are performance-based steel grades and their global material properties can be achieved with various steel chemistries and manufacturing processes, leading to various microstructures. In this paper, we investigate the influence of supplier variation and resulting microstructure difference on the overall mechanical properties as well as local formability behaviors of advanced high strength steels (AHSS). For this purpose, we first examined the basic material properties and the transformation kinetics of TRansformation Induced Plasticity (TRIP) 800 steels from three different suppliers under different testing temperatures. The experimental results show that there is a significant supplier (i.e., manufacturing process) dependency of the TRIP 800 steel mechanical and microstructure properties. Next, we examined the local formability of two commercial Dual Phase (DP) 980 steels during stamping process. The two commercial DP 980 steels also exhibit noticeably different formability during stamping process in the sense that one of them shows severe tendency for shear fracture. Microstructure-based finite element analyses are carried out next to simulate the localized deformation process with the two DP 980 microstructures, and the results suggest that the possible reason for the difference in formability lies in the morphology of the hard martensite phase in the DP microstructure.

  7. Organizational heterogeneity of vertebrate genomes.

    Directory of Open Access Journals (Sweden)

    Svetlana Frenkel

    Full Text Available Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as "texts" using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter--GDM allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences.

  8. Organizational heterogeneity of vertebrate genomes.

    Science.gov (United States)

    Frenkel, Svetlana; Kirzhner, Valery; Korol, Abraham

    2012-01-01

    Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as "texts" using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS) analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers) in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter--GDM) allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences.

  9. Reaction Selectivity in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  10. White matter microstructure correlates of mathematical giftedness and intelligence quotient.

    Science.gov (United States)

    Navas-Sánchez, Francisco J; Alemán-Gómez, Yasser; Sánchez-Gonzalez, Javier; Guzmán-De-Villoria, Juan A; Franco, Carolina; Robles, Olalla; Arango, Celso; Desco, Manuel

    2014-06-01

    Recent functional neuroimaging studies have shown differences in brain activation between mathematically gifted adolescents and controls. The aim of this study was to investigate the relationship between mathematical giftedness, intelligent quotient (IQ), and the microstructure of white matter tracts in a sample composed of math-gifted adolescents and aged-matched controls. Math-gifted subjects were selected through a national program based on detecting enhanced visuospatial abilities and creative thinking. We used diffusion tensor imaging to assess white matter microstructure in neuroanatomical connectivity. The processing included voxel-wise and region of interest-based analyses of the fractional anisotropy (FA), a parameter which is purportedly related to white matter microstructure. In a whole-sample analysis, IQ showed a significant positive correlation with FA, mainly in the corpus callosum, supporting the idea that efficient information transfer between hemispheres is crucial for higher intellectual capabilities. In addition, math-gifted adolescents showed increased FA (adjusted for IQ) in white matter tracts connecting frontal lobes with basal ganglia and parietal regions. The enhanced anatomical connectivity observed in the forceps minor and splenium may underlie the greater fluid reasoning, visuospatial working memory, and creative capabilities of these children. © 2013 Wiley Periodicals, Inc.

  11. Profiles of aberrant white matter microstructure in fragile X syndrome.

    Science.gov (United States)

    Hall, Scott S; Dougherty, Robert F; Reiss, Allan L

    2016-01-01

    Previous studies attempting to quantify white matter (WM) microstructure in individuals with fragile X syndrome (FXS) have produced inconsistent findings, most likely due to the various control groups employed, differing analysis methods, and failure to examine for potential motion artifact. In addition, analyses have heretofore lacked sufficient specificity to provide regional information. In this study, we used Automated Fiber-tract Quantification (AFQ) to identify specific regions of aberrant WM microstructure along WM tracts in patients with FXS that differed from controls who were matched on age, IQ and degree of autistic symptoms. Participants were 20 patients with FXS, aged 10 to 23 years, and 20 matched controls. Using Automated Fiber-tract Quantification (AFQ), we created Tract Profiles of fractional anisotropy and mean diffusivity along 18 major WM fascicles. We found that fractional anisotropy was significantly increased in the left and right inferior longitudinal fasciculus (ILF), right uncinate fasciculus, and left cingulum hippocampus in individuals with FXS compared to controls. Conversely, mean diffusivity was significantly decreased in the right ILF in patients with FXS compared to controls. Age was significantly negatively associated with MD values across both groups in 11 tracts. Taken together, these findings indicate that FXS results in abnormal WM microstructure in specific regions of the ILF and uncinate fasciculus, most likely caused by inefficient synaptic pruning as a result of decreased or absent Fragile X Mental Retardation Protein (FMRP). Longitudinal studies are needed to confirm these findings.

  12. Profiles of aberrant white matter microstructure in fragile X syndrome

    Directory of Open Access Journals (Sweden)

    Scott S. Hall

    2016-01-01

    Full Text Available Previous studies attempting to quantify white matter (WM microstructure in individuals with fragile X syndrome (FXS have produced inconsistent findings, most likely due to the various control groups employed, differing analysis methods, and failure to examine for potential motion artifact. In addition, analyses have heretofore lacked sufficient specificity to provide regional information. In this study, we used Automated Fiber-tract Quantification (AFQ to identify specific regions of aberrant WM microstructure along WM tracts in patients with FXS that differed from controls who were matched on age, IQ and degree of autistic symptoms. Participants were 20 patients with FXS, aged 10 to 23 years, and 20 matched controls. Using Automated Fiber-tract Quantification (AFQ, we created Tract Profiles of fractional anisotropy and mean diffusivity along 18 major WM fascicles. We found that fractional anisotropy was significantly increased in the left and right inferior longitudinal fasciculus (ILF, right uncinate fasciculus, and left cingulum hippocampus in individuals with FXS compared to controls. Conversely, mean diffusivity was significantly decreased in the right ILF in patients with FXS compared to controls. Age was significantly negatively associated with MD values across both groups in 11 tracts. Taken together, these findings indicate that FXS results in abnormal WM microstructure in specific regions of the ILF and uncinate fasciculus, most likely caused by inefficient synaptic pruning as a result of decreased or absent Fragile X Mental Retardation Protein (FMRP. Longitudinal studies are needed to confirm these findings.

  13. Microstructural analysis of conditioned and unconditioned responses to maltodextrin.

    Science.gov (United States)

    Dwyer, Dominic M

    2008-05-01

    The microstructure of licking responses was analyzed to investigate the interaction between unconditioned responses to maltodextrin and the responses to flavor cues previously associated with maltodextrin. Experiment 1 demonstrated that although the consumption of maltodextrin peaked at intermediate concentrations, the mean lick cluster size showed a positive, monotonic increase with concentration. In Experiment 2, a (conditioned stimulus) CS+ flavor was paired with 16% maltodextrin, whereas a CS- flavor was paired with 2% maltodextrin. During test, consumption of the CS+ was higher than that of the CS- when the flavors were combined with 2% maltodextrin, but not when combined with 16% maltodextrin. In contrast, cluster size was larger with the CS+ than with the CS-, regardless of the concentration of maltodextrin present on test. Previous analyses of licking microstructure indicate that cluster size reflects the palatability of the ingested solution. Thus, the present results indicate that flavor conditioning can change the palatability of the cue flavors. Adding the CS+ flavor to maltodextrin produced results analogous to increasing the concentration of maltodextrin (in terms of both consumption and licking microstructure measures), which is consistent with the idea that after conditioning, responses to the CS+ flavor and to the unconditioned stimulus are mediated via the same representation.

  14. Chemical and microstructural diversity of steel grades

    Directory of Open Access Journals (Sweden)

    Zorc, B.

    2002-12-01

    Full Text Available The aim of the paper is to show, using theoretical and practical analyses, chemical and microstructural differences among individual types of steel grades 355 found in the market. The mechanical properties required for these steels are achieved by alloying or thermomechanical treatment. It was found that the individual types of this steel are poorly weldable, particularly those of large thickness.

    El objetivo del artículo es presentar, en base a un análisis teórico y práctico, las diferencias químicas y microestructurales entre los diferentes tipos de aceros calidad 355 que pueden encontrarse en el mercado. Las características mecánicas requeridas en estos aceros se consiguen con aleaciones, o bien a través de tratamientos termo-mecánicos.Se ha llegado a la conclusión de que determinados tipos de acero son más difíciles de soldar, en especial cuando se trata de espesores grandes.

  15. Anorthite porcelain: synthesis, phase and microstructural evolution

    Indian Academy of Sciences (India)

    Mousumi Pal; Sukhen Das; Swapan Kumar Das

    2015-04-01

    In the present study, anorthite (CaAl2Si2O8) porcelain was fabricated using Ca(OH)2, Al(OH)3, quartz, aluminous cement and feldspar as raw materials. Two compositions were formulated (coded as CAQ and CFQ)and their physico-mechanical properties (%AP, BD, flexural strength) were studied and compared. CAQ (21.2 wt% Ca(OH)2, 44.5 wt% Al(OH)3 and 34.3 wt% quartz) shows very poor densification and strength even after heating at 1450° C, although anorthite formation is observed on heating it at various temperatures. On the other hand, CFQ (48.6 wt% aluminous cement, 29.37 wt% feldspar and 22.06 wt% quartz) achieved full densification and superior strength at 1450° C with more anorthite formation compared to CAQ. X-ray diffraction and scanning electron microscope studies were also carried out to analyse the phase and microstructure evolution. The coefficient of thermal expansion of the anorthite-based sample was found to be lower than quartz and mullite porcelain which suggests its application as cooking ware.

  16. Deformation-induced microstructural evolution at grain scale

    DEFF Research Database (Denmark)

    Winther, Grethe

    aswell as dislocation patterning by formation of dislocation boundaries occur. Experimental data andassociated data analysis at the grain scale and below will be presented to illustrate our current level ofunderstanding. The basis for the analysis is the crystallographic orientation of the grain as well......During plastic deformation metals develop microstructures which may be analysed on several scales,spanning from crystallographic textures averaged over the entire sample to the scale of individualgrains. Even within individual grains, intragranular phenomena in the form of orientation gradients...

  17. Analysis and computation of microstructure in finite plasticity

    CERN Document Server

    Hackl, Klaus

    2015-01-01

    This book addresses the need for a fundamental understanding of the physical origin, the mathematical behavior, and the numerical treatment of models which include microstructure. Leading scientists present their efforts involving mathematical analysis, numerical analysis, computational mechanics, material modelling and experiment. The mathematical analyses are based on methods from the calculus of variations, while in the numerical implementation global optimization algorithms play a central role. The modeling covers all length scales, from the atomic structure up to macroscopic samples. The development of the models ware guided by experiments on single and polycrystals, and results will be checked against experimental data.

  18. An Exploratory Study of the Microstructure of Mullite Fibers

    Science.gov (United States)

    Santoro, G.; Probst, H. B.; Buzek, B.

    1973-01-01

    The microstructures of mullite composition fibers were examined by transmission electron microscopic techniques and by X-ray diffraction analyses. Both spun and monofilament fiber structures contained little porosity, nor did the degree of porosity change after heating the monofilament to 1205 C for one half hour. Thermal exposure produced crystallite growth and nucleation from the amorphous phase in all three of the spun fibers. After 116 hours at 1426 C, the crystallites of the standard spun fibers became contiguous. In addition, the surface crystallites of these fibers were found to be more than twice as large as the interior crystallites.

  19. Molecular Dynamics Simulation of Microstructure of Nanocrystalline Copper

    Institute of Scientific and Technical Information of China (English)

    WEN Yu-Hua; ZHOU Fu-Xin; LIU Yue-Wu

    2001-01-01

    The microstructure of computer generated nanocrystalline coppers is simulated by using molecular dynamics with the Finnis-Sinclair potential, analysed by means of radial distribution functions, coordination number, atomic energy and local crystalline order. The influence of the grain size on the nanocrystalline structure is studied.The results reveal that as the grain size is reduced, the grain boundary shows no significant structural difference,but the grain interior becomes more disordered, and their structural difference diminishes gradually; however,the density and the atomic average energy of the grain boundary present different tendencies from those of the grain interior.

  20. Laser engineered surfaces from glass forming alloy powder precursors : Microstructure and wear

    NARCIS (Netherlands)

    Matthews, D. T. A.; Ocelik, V.; Branagan, D.; de Hosson, J. Th. M.

    2009-01-01

    Fe-based metallic glass forming powders have been deposited on mild steel substrates using high power laser cladding. Coatings microstructures have been analysed by scanning- and transmission-electron microscopy and at varying substrate dilutions, have been found to comprise a 100 to 500 nm interden

  1. Thermal desorption of deuterium from modified carbon nanotubes and its correlation to the microstructure

    NARCIS (Netherlands)

    Lisowski, W.; Keim, E.G.; Berg, van den A.H.J.; Smithers, M.A.

    2006-01-01

    The process of deuterium desorption from single-wall carbon nanotubes (SWNTs) modified by atomic (D) and molecular (D2) deuterium treatment was investigated in an ultrahigh vacuum environment using thermal desorption mass spectroscopy (TDMS). Microstructural and chemical analyses of SWNT material, m

  2. Performances of the leak microstructures

    CERN Document Server

    Lombardi, M; Lombardi, F S

    2002-01-01

    The capabilities of a new microstructure, anode point based, for the detection of gas ionizing radiations are stressed. For every single detected ionizing radiation it gives a pair of 'induced' charges (anodic and cathodic) of the same amount (pulses of the same amplitudes), of opposite sign, with the same collection time and essentially in time coincidence, that are proportional to the primary ionization collected. The complete lack of insulating materials in the active volume of this microstructure avoids problems of charging-up and makes stable and repeatable its behaviour. Primary avalanches with a size of more than 2.5x10 sup 7 electrons (4 pC) giving current pulses with a peak of more than 0.26 mA on 100 OMEGA and about 30 ns duration are possible with 5.9 keV X-rays of sup 5 sup 5 Fe working in proportional region and in isobutane gas. Single electrons emitted by a heated filament (E sub c <1 eV) were detected in 760 Torr of isobutane; with an estimated gas gain of 1.2x10 sup 6 a counting rate up to...

  3. Microstructure Analysis of Heated Portland Cement Paste

    NARCIS (Netherlands)

    Zhang, Q.; Ye, G.

    2011-01-01

    When a concrete structure is exposed to high temperature, the mechanical damage and chemical transformation take place simultaneously, which will change the microstructure of material. On the other hand, the mechanical properties and transport properties depend on the development of microstructure o

  4. Emulsification with microstructured systems : process principles

    NARCIS (Netherlands)

    Zwan, van der E.A.

    2008-01-01

    The aim of this thesis is to elucidate the underlying processes and mechanisms that determine the droplet size of emulsions produced with microstructured systems, such as premix microstructure homogenization and microchannel emulsification. The ultimate goal is to describe these methods based on det

  5. Microstructure Development during Solidification of Aluminium Alloys

    NARCIS (Netherlands)

    Ruvalcaba Jimenez, D.G.

    2009-01-01

    This Thesis demonstrates studies on microstructure development during the solidification of aluminium alloys. New insights of structure development are presented here. Experimental techniques such as quenching and in-situ High-brilliance X-ray microscopy were utilized to study the microstructure evo

  6. Heterogeneous electrocatalysis in porous cathodes of solid oxide fuel cells

    CERN Document Server

    Fu, Y; Bertei, A; Qi, C; Mohanram, A; Pietras, J D; Bazant, M Z

    2014-01-01

    A general physics-based model is developed for heterogeneous electrocatalysis in porous electrodes and used to predict and interpret the impedance of solid oxide fuel cells. This model describes the coupled processes of oxygen gas dissociative adsorption and surface diffusion of the oxygen intermediate to the triple phase boundary, where charge transfer occurs. The model accurately captures the Gerischer-like frequency dependence and the oxygen partial pressure dependence of the impedance of symmetric cathode cells. Digital image analysis of the microstructure of the cathode functional layer in four different cells directly confirms the predicted connection between geometrical properties and the impedance response. As in classical catalysis, the electrocatalytic activity is controlled by an effective Thiele modulus, which is the ratio of the surface diffusion length (mean distance from an adsorption site to the triple phase boundary) to the surface boundary layer length (square root of surface diffusivity div...

  7. Job Heterogeneity and Coordination Frictions

    DEFF Research Database (Denmark)

    Kennes, John; le Maire, Daniel

    the job ladder, how the identification of assortative matching is fundamentally different in directed and undirected search models, how our theory accounts for business cycle facts related to inter-temporal changes in job offer distributions, and how our model could also be used to identify......We develop a new directed search model of a frictional labor market with a continuum of heterogenous workers and firms. We estimate two versions of the model - auction and price posting - using Danish data on wages and productivities. Assuming heterogenous workers with no comparative advantage, we...

  8. Development of a methodology for microstructural description

    Directory of Open Access Journals (Sweden)

    Vanderley de Vasconcelos

    1999-07-01

    Full Text Available A systematic methodology for microstructural description can help the task of obtaining the processing x microstructure x properties x performance relationships. There are, however, some difficulties in performing this task, which are related mainly to the following three factors: the complexity of the interactions between microstructural features; difficulties in evaluating geometric parameters of microstructural features; and difficulties in relating these geometric parameters to process variables. To solve some of these problems, it is proposed a methodology that embodies the following features: takes into account the different possible types of approaches for the microstructural description problem; includes concepts and tools of Total Quality Management; is supported on techniques of system analysis; and makes use of computer modeling and simulation and statistical design of experiments tools. The methodology was applied on evaluating some topological parameters during sintering process and its results were compared with available experimental data.

  9. Effects of the heterogeneity in the electron beam welded joint on fatigue crack growth in Ti-6Al-4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li Xingzhi [State Key Laboratory of Material Processing and Die Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Hu Shubing, E-mail: hushubing@163.com [State Key Laboratory of Material Processing and Die Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Xiao Jianzhong; Ji Longbo [State Key Laboratory of Material Processing and Die Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2011-11-25

    Highlights: {yields} The heterogeneity in electron beam welded joint was defined and described. {yields} The fatigue crack growth rates (FCGR) in different zones. {yields} The fatigue crack growth rate in different thicknesses of the welded joint. {yields} The effect of heterogeneity on the FCGR was discussed from the microstructure by SEM and TEM. {yields} The fatigue crack growth rate was closely related to the heterogeneity. - Abstract: The heterogeneity of electron beam (EB)-welded joints in thick Ti-6Al-4V alloy plates is defined and described. The microstructure, hardness, and fatigue crack growth rate (FCGR) in the fuse zone (FZ) and the heat-affected zone (HAZ) of thick Ti-6Al-4V alloy EB-welded joint are studied using a new testing and interception method. The fatigue fractographs, crack growth paths and the microscopic deformation are observed through scanning and transmission electron microscopy. The effect mechanism of heterogeneity in the electron beam weld joint to FCGRs is discussed. The results reveal that FCGR is higher in the HAZ than in the FZ, mainly because of the effect of heterogeneity I of the welded joint. Heterogeneity II increases from the top to the root of the welding seam while the size of the {alpha}' phase decreases. Consequently, FCGR is higher at the root of the welding seam. Heterogeneity in the joint is found to greatly influence the FCGR.

  10. Microstructure and Property Modifications of Cold Rolled IF Steel by Local Laser Annealing

    Science.gov (United States)

    Hallberg, Håkan; Adamski, Frédéric; Baïz, Sarah; Castelnau, Olivier

    2017-07-01

    Laser annealing experiments are performed on cold rolled IF steel whereby highly localized microstructure and property modification are achieved. The microstructure is seen to develop by strongly heterogeneous recrystallization to provide steep gradients, across the submillimeter scale, of grain size and crystallographic texture. Hardness mapping by microindentation is used to reveal the corresponding gradients in macroscopic properties. A 2D level set model of the microstructure development is established as a tool to further optimize the method and to investigate, for example, the development of grain size variations due to the strong and transient thermal gradient. Particular focus is given to the evolution of the beneficial γ-fiber texture during laser annealing. The simulations indicate that the influence of selective growth based on anisotropic grain boundary properties only has a minor effect on texture evolution compared to heterogeneous stored energy, temperature variations, and nucleation conditions. It is also shown that although the α-fiber has an initial frequency advantage, the higher probability of γ-nucleation, in combination with a higher stored energy driving force in this fiber, promotes a stronger presence of the γ-fiber as also observed in experiments.

  11. Microstructure and Property Modifications of Cold Rolled IF Steel by Local Laser Annealing

    Science.gov (United States)

    Hallberg, Håkan; Adamski, Frédéric; Baïz, Sarah; Castelnau, Olivier

    2017-10-01

    Laser annealing experiments are performed on cold rolled IF steel whereby highly localized microstructure and property modification are achieved. The microstructure is seen to develop by strongly heterogeneous recrystallization to provide steep gradients, across the submillimeter scale, of grain size and crystallographic texture. Hardness mapping by microindentation is used to reveal the corresponding gradients in macroscopic properties. A 2D level set model of the microstructure development is established as a tool to further optimize the method and to investigate, for example, the development of grain size variations due to the strong and transient thermal gradient. Particular focus is given to the evolution of the beneficial γ-fiber texture during laser annealing. The simulations indicate that the influence of selective growth based on anisotropic grain boundary properties only has a minor effect on texture evolution compared to heterogeneous stored energy, temperature variations, and nucleation conditions. It is also shown that although the α-fiber has an initial frequency advantage, the higher probability of γ-nucleation, in combination with a higher stored energy driving force in this fiber, promotes a stronger presence of the γ-fiber as also observed in experiments.

  12. Knowledge-based adaptive polarimetric detection in heterogeneous clutter

    Institute of Scientific and Technical Information of China (English)

    Yinan Zhao,Fengcong Li,; Xiaolin Qiao

    2014-01-01

    The detection performance and the constant false alarm rate behavior of the conventional adaptive detectors are severely degraded in heterogeneous clutter. This paper designs and analy-ses a knowledge-based (KB) adaptive polarimetric detector in het-erogeneous clutter. The proposed detection scheme is composed of a data selector using polarization knowledge and an adaptive polarization detector using training data. A polarization data se-lector based on the maximum likelihood estimation is proposed to remove outliers from the heterogeneous training data. This selector can remove outliers effectively, thus the training data is purified for estimating the clutter covariance matrix. Consequently, the performance of the adaptive detector is improved. We assess the performance of the KB adaptive polarimetric detector and the adaptive polarimetric detector without a data selector using sim-ulated data and IPIX radar data. The results show that the KB adaptive polarization detector outperforms its non-KB counter-parts.

  13. Carbon Emissions and Economic Growth: Causality Testing in Heterogenous Panels

    Energy Technology Data Exchange (ETDEWEB)

    David Maddison; Katrin Rehdanz [Department of Economics, University of Birmingham, Birmingham (United Kingdom)

    2008-09-30

    Numerous papers have examined data on energy and GDP for evidence of Granger causality. Using time series techniques these analyses not infrequently reach differing conclusions concerning the existence and direction of Granger causality. This paper presents a heterogenous panel approach to Granger causality testing. This technique is used to examine a panel of data for evidence of a causal relationship between GDP and carbon emissions per capita allowing for heterogeneity in short run dynamics and even the long run cointegrating vector. This technique is compared to the standard fixed dynamic effects approach to pooling individual error correction models. In one important case the heterogenous panel test for Granger causality reaches conclusions quite different to those from conventional tests of Granger causality. Except for Asia there is strong evidence for the existence of a bidirectional causal relationship between GDP per capita and CO{sub 2} emissions per capita.

  14. Imaging plants dynamics in heterogenic environments.

    Science.gov (United States)

    Fiorani, Fabio; Rascher, Uwe; Jahnke, Siegfried; Schurr, Ulrich

    2012-04-01

    Noninvasive imaging sensors and computer vision approaches are key technologies to quantify plant structure, physiological status, and performance. Today, imaging sensors exploit a wide range of the electromagnetic spectrum, and they can be deployed to measure a growing number of traits, also in heterogenic environments. Recent advances include the possibility to acquire high-resolution spectra by imaging spectroscopy and classify signatures that might be informative of plant development, nutrition, health, and disease. Three-dimensional (3D) reconstruction of surfaces and volume is of particular interest, enabling functional and mechanistic analyses. While taking pictures is relatively easy, quantitative interpretation often remains challenging and requires integrating knowledge of sensor physics, image analysis, and complex traits characterizing plant phenotypes.

  15. Evolution of Local Microstructures: Spatial Instabilities of Coarsening Clusters

    Science.gov (United States)

    Frazier, Donald O.

    1999-01-01

    This work examines the diffusional growth of discrete phase particles dispersed within a matrix. Engineering materials are microstructurally heterogeneous, and the details of the microstructure determine how well that material performs in a given application. Critical to the development of designing multiphase microstructures with long-term stability is the process of Ostwald ripening. Ripening, or phase coarsening, is a diffusion-limited process which arises in polydisperse multiphase materials. Growth and dissolution occur because fluxes of solute, driven by chemical potential gradients at the interfaces of the dispersed phase material, depend on particle size. The kinetics of these processes are "competitive," dictating that larger particles grow at the expense of smaller ones, overall leading to an increase of the average particle size. The classical treatment of phase coarsening was done by Todes, Lifshitz, and Slyozov, (TLS) in the limit of zero volume fraction, V(sub v), of the dispersed phase. Since the publication of TLS theory there have been numerous investigations, many of which sought to describe the kinetic scaling behavior over a 0 range of volume fractions. Some studies in the literature report that the relative increase in coarsening rate at low (but not zero) volume fractions compared to that predicted by TLS is proportional to v(sub v)(exp 1/2), whereas others suggcest V(sub v)(exp 1/3). This issue has been resolved recently by simulation studies at low volume fractions in three dimensions by members of the Rensselaer/MSFC team. Our studies of ripening behavior using large-scale numerical simulations suggest that although there are different circumstances which can lead to either scaling law, the most important length scale at low volume fractions is the diffusional analog of the Debye screening length. The numerical simulations we employed exploit the use of a recently developed "snapshot" technique, and identifies the nature of the coarsening

  16. Laser Beam Focus Analyser

    DEFF Research Database (Denmark)

    Nielsen, Peter Carøe; Hansen, Hans Nørgaard; Olsen, Flemming Ove

    2007-01-01

    The quantitative and qualitative description of laser beam characteristics is important for process implementation and optimisation. In particular, a need for quantitative characterisation of beam diameter was identified when using fibre lasers for micro manufacturing. Here the beam diameter limits...... the obtainable features in direct laser machining as well as heat affected zones in welding processes. This paper describes the development of a measuring unit capable of analysing beam shape and diameter of lasers to be used in manufacturing processes. The analyser is based on the principle of a rotating...... mechanical wire being swept through the laser beam at varying Z-heights. The reflected signal is analysed and the resulting beam profile determined. The development comprised the design of a flexible fixture capable of providing both rotation and Z-axis movement, control software including data capture...

  17. The strength of heterogeneous volcanic rocks: A 2D approximation

    Science.gov (United States)

    Heap, Michael J.; Wadsworth, Fabian B.; Xu, Tao; Chen, Chong-feng; Tang, Chun'an

    2016-06-01

    Volcanic rocks typically contain heterogeneities in the form of crystals and pores. We investigate here the influence of such heterogeneity on the strength of volcanic rocks using an elastic damage mechanics model in which we numerically deform two-dimensional samples comprising low-strength elements representing crystals and zero-strength elements representing pores. These circular elements are stochastically generated so that there is no overlap in a medium representing the groundmass. Our modelling indicates that increasing the fraction of pores and/or crystals reduces the strength of volcanic rocks, and that increasing the pore fraction results in larger strength reductions than increasing the crystal fraction. The model also highlights an important weakening role for pore diameter, but finds that crystal diameter has a less significant influence for strength. To account for heterogeneity (pores and crystals), we propose an effective medium approach where we define an effective pore fraction ϕp‧ = Vp/(Vp + Vg) where Vp and Vg are the pore and groundmass fractions, respectively. Highly heterogeneous samples (containing high pore and/or crystal fractions) will therefore have high values of ϕp‧, and vice-versa. When we express our numerical samples (more than 200 simulations spanning a wide range of crystal and pore fractions) in terms of ϕp‧, we find that their strengths can be described by a single curve for a given pore diameter. To provide a predictive tool for the strength of heterogeneous volcanic rocks, we propose a modified version of 2D solution for the Sammis and Ashby (1986) pore-emanating crack model, a micromechanical model designed to estimate strength using microstructural attributes such as porosity, pore radius, and fracture toughness. The model, reformulated to include ϕp‧ (and therefore crystal fraction), captures the strength curves for our numerical simulations over a sample heterogeneity range relevant to volcanic systems. We find

  18. Wireless Internet on Heterogeneous Networks

    NARCIS (Netherlands)

    Wu, G.

    2001-01-01

    The wide proliferation of wireless systems and the use of software radio technologies enable the employment of a heterogeneous network. In this concept services are delivered via the network that is most efficient for that service. The solution is based on a common core network that interconnects ac

  19. Communicating to heterogeneous target groups

    DEFF Research Database (Denmark)

    Pedersen, Karsten

    very often have to communicate to rather heterogeneous target groups that have little more in common than a certain geographical habitat. That goes against most schoolbook teaching in the field of communication, but is none the less the terms with which that kind of communication has to live...

  20. Dynamic heterogeneity and life histories

    DEFF Research Database (Denmark)

    Tuljapurkar, Shripad; Steiner, Uli

    2010-01-01

    of the variation among individual characteristics that is generated by dynamic heterogeneity. We conclude by discussing our ongoing and planned work on animals and humans. We also discuss the connections between our work and recent work on human mortality, disability and health, and life course theory....

  1. Social Capital and Community Heterogeneity

    Science.gov (United States)

    Coffe, Hilde

    2009-01-01

    Recent findings indicate that more pronounced community heterogeneity is associated with lower levels of social capital. These studies, however, concentrate on specific aspects in which people differ (such as income inequality or ethnic diversity). In the present paper, we introduce the number of parties in the local party system as a more…

  2. Social capital and community heterogeneity

    NARCIS (Netherlands)

    Coffé, Hilde R.

    2009-01-01

    Abstract Recent findings indicate that more pronounced community heterogeneity is associated with lower levels of social capital. These studies, however, concentrate on specific aspects in which people differ (such as income inequality or ethnic diversity). In the present paper, we introduce the

  3. Prices and heterogeneous search costs

    NARCIS (Netherlands)

    Luis Moraga-Gonzalez, Jose; Sandor, Zsolt; Wildenbeest, Matthijs R.

    2017-01-01

    We study price formation in a model of consumer search for differentiated products in which consumers have heterogeneous search costs. We provide conditions under which a pure-strategy symmetric Nash equilibrium exists and is unique. Search costs affect two margins-the intensive search margin (or se

  4. Floodplain heterogeneity and meander migration

    Science.gov (United States)

    The impact of horizontal heterogeneity of floodplain soils on rates and patterns of meander migration is analyzed with a Ikeda et al. (1981)-type model for hydrodynamics and bed morphodynamics, coupled with a physically-based bank erosion model according to the approach developed by Motta et al. (20...

  5. Formation of Rationally Heterogeneous Expectations

    NARCIS (Netherlands)

    Pfajfar, D.

    2012-01-01

    Abstract: This paper models expectation formation by taking into account that agents produce heterogeneous expectations due to model uncertainty, informational frictions and different capacities for processing information. We show that there are two general classes of steady states within this frame

  6. Heterogeneous catalysis through microcontact printing

    NARCIS (Netherlands)

    Spruell, Jason M.; Sheriff, Bonnie A.; Rozkiewicz, D.I.; Dichtel, William R.; Rohde, Rosemary D.; Reinhoudt, David; Stoddart, Fraser; Heath, James R.

    2008-01-01

    Minting a Stamp: The preparation of copper metal-coated elastomeric stamps and their use in catalyzing the Cu-catalyzed azide-alkyne cycloaddition reaction heterogeneously through microcontact printing is described. This StampCat process is compared to other conventional surface-functionalization te

  7. REPLIKASI UNIDIRECTIONAL PADA HETEROGEN DATABASE

    Directory of Open Access Journals (Sweden)

    Hendro Nindito

    2013-11-01

    where development can be done quickly and testing of working models of the interaction process is done through repeated. From this research it is obtained that the database replication technology using Oracle Golden Gate can be applied in heterogeneous environments in real time as well.

  8. Surface science of heterogeneous reactions.

    Science.gov (United States)

    White, J M

    1982-10-29

    Some of the present and future directions for surface science as a growing and naturally interdisciplinary subject are reviewed. Particular attention is given to surface reaction chemistry as it is related to heterogenous catalysis, a subject area where there are abundant opportunities for detailed measurements of structure and dynamics at the molecular level.

  9. Measuring and predicting heterogeneous recessions

    NARCIS (Netherlands)

    C. Cakmakli; R. Paap; D. van Dijk

    2011-01-01

    This paper conducts an empirical analysis of the heterogeneity of recessions in monthly U.S. coincident and leading indicator variables. Univariate Markovswitching models indicate that it is appropriate to allow for two distinct recession regimes, corresponding with ‘mild’ and ‘severe’ recessions. A

  10. Characterization of microstructure, viscoelasticity, heterogeneity and ergodicity in pectin-laponite-CTAB-calcium nanocomposite hydrogels.

    Science.gov (United States)

    Joshi, Nidhi; Rawat, Kamla; Bohidar, H B

    2016-01-20

    In order to customize the viscoelastic properties of pectin gels, it is necessary to work on a composite platform. Herein, the gelation kinetics, and viscoelastic characterization of anionic polysaccharide pectin dispersion prepared in presence of nanoclay laponite are reported using dynamic light scattering and rheology measurements. The ratio Rg/Rh (Rg and Rh are radius of gyration and hydrodynamic radius respectively) determined from light scattering data revealed the presence of random coils of pectin chains inside the gel matrix. When nanoclay laponite was added to the pectin chains solution, two-phase separation was noticed instantaneously. Therefore, the surfactant cetyltrimethylammonium bromide [CTAB] was added to exfoliate the clay platelets in the dispersion, and also in its gel phase. The exfoliating agent cetyltrimethylammonium bromide ([CTAB]≈ cmc/10) helped to enhance the homogeneity and stability of the pectin-clay sols and gels. The storage and loss moduli (G' and G") of the composite gel changed significantly as function of nanoclay laponite content for concentration up to 0.03% (w/v) causing the softening of the gels (gel strength reduced by close to 50%) compared to pectin-calcium gel. However, as the concentration of nanoclay laponite was maintained between 0.01% and 0.03% (w/v), the gel rigidity (G') recovered by 30% (35-45 Pa). The transition from ergodic to non-ergodic state occurred during sol-gel transition owing to the presence of the nanoclay laponite. The gelation time was not too different from the ergodicity breaking time. Thus, the presence of nanoclay laponite in such minute concentration is shown to cause considerable change in the thermo-physical property of the composite gels. This material property modulation will facilitate designing of soft gels having storage modulus continuously varying in the wide range of 10-70 Pa while keeping the gelation temperature mostly unaltered.

  11. Parametric optimisation and microstructural analysis on high power Yb-fibre laser welding of Ti-6Al-4V

    Science.gov (United States)

    Ahn, J.; Chen, L.; Davies, C. M.; Dear, J. P.

    2016-11-01

    In this work thin sheets of Ti-6Al-4V were full penetration welded using a 5 kW fibre laser in order to evaluate the effectiveness of high power fibre laser as a welding processing tool for welding Ti-6Al-4V with the requirements of the aircraft industry and to determine the effect of welding parameters including laser power, welding speed and beam focal position on the weld microstructure, bead profile and weld quality. It involved establishing an understanding of the influence of welding parameters on microstructural change, welding defects, and the characteristics of heat affected zone (HAZ) and weld metal (WM) of fibre laser welded joints. The optimum range of welding parameters which produced welds without cracking and porosity were identified. The influence of the welding parameters on the weld joint heterogeneity was characterised by conducting detailed microstructural analysis.

  12. Effect of grain morphology on gas bubble swelling in UMo fuels – A 3D microstructure dependent Booth model

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Shenyang; Burkes, Douglas; Lavender, Curt A.; Joshi, Vineet

    2016-11-01

    A three dimensional microstructure dependent swelling model is developed for studying the fission gas swelling kinetics in irradiated nuclear fuels. The model is extended from the Booth model [1] in order to investigate the effect of heterogeneous microstructures on gas bubble swelling kinetics. As an application of the model, the effect of grain morphology, fission gas diffusivity, and spatial dependent fission rate on swelling kinetics are simulated in UMo fuels. It is found that the decrease of grain size, the increase of grain aspect ratio for the grain having the same volume, and the increase of fission gas diffusivity (fission rate) cause the increase of swelling kinetics. Other heterogeneities such as second phases and spatial dependent thermodynamic properties including diffusivity of fission gas, sink and source strength of defects could be naturally integrated into the model to enhance the model capability.

  13. Strong, Multi-Scale Heterogeneity in Earth's Lowermost Mantle.

    Science.gov (United States)

    Tkalčić, Hrvoje; Young, Mallory; Muir, Jack B; Davies, D Rhodri; Mattesini, Maurizio

    2015-12-17

    The core mantle boundary (CMB) separates Earth's liquid iron outer core from the solid but slowly convecting mantle. The detailed structure and dynamics of the mantle within ~300 km of this interface remain enigmatic: it is a complex region, which exhibits thermal, compositional and phase-related heterogeneity, isolated pockets of partial melt and strong variations in seismic velocity and anisotropy. Nonetheless, characterising the structure of this region is crucial to a better understanding of the mantle's thermo-chemical evolution and the nature of core-mantle interactions. In this study, we examine the heterogeneity spectrum from a recent P-wave tomographic model, which is based upon trans-dimensional and hierarchical Bayesian imaging. Our tomographic technique avoids explicit model parameterization, smoothing and damping. Spectral analyses reveal a multi-scale wavelength content and a power of heterogeneity that is three times larger than previous estimates. Inter alia, the resulting heterogeneity spectrum gives a more complete picture of the lowermost mantle and provides a bridge between the long-wavelength features obtained in global S-wave models and the short-scale dimensions of seismic scatterers. The evidence that we present for strong, multi-scale lowermost mantle heterogeneity has important implications for the nature of lower mantle dynamics and prescribes complex boundary conditions for Earth's geodynamo.

  14. Identification of homogeneous and heterogeneous variables in pooled cohort studies.

    Science.gov (United States)

    Cheng, Xin; Lu, Wenbin; Liu, Mengling

    2015-06-01

    Pooled analyses integrate data from multiple studies and achieve a larger sample size for enhanced statistical power. When heterogeneity exists in variables' effects on the outcome across studies, the simple pooling strategy fails to present a fair and complete picture of the effects of heterogeneous variables. Thus, it is important to investigate the homogeneous and heterogeneous structure of variables in pooled studies. In this article, we consider the pooled cohort studies with time-to-event outcomes and propose a penalized Cox partial likelihood approach with adaptively weighted composite penalties on variables' homogeneous and heterogeneous effects. We show that our method can characterize the variables as having heterogeneous, homogeneous, or null effects, and estimate non-zero effects. The results are readily extended to high-dimensional applications where the number of parameters is larger than the sample size. The proposed selection and estimation procedure can be implemented using the iterative shooting algorithm. We conduct extensive numerical studies to evaluate the performance of our proposed method and demonstrate it using a pooled analysis of gene expression in patients with ovarian cancer. © 2015, The International Biometric Society.

  15. The effect of microstructure on the fracture toughness of titanium alloys

    Science.gov (United States)

    Vanstone, R. H.; Low, J. R., Jr.; Shannon, J. L., Jr.

    1974-01-01

    The microstructure of the alpha titanium alloy Ti-5Al-2.5Sn and the metastable beta titanium alloy Beta 3 was examined. The material was from normal and extra low interstitial grade plates which were either air-cooled or furnace-cooled from an annealing treatment. Beta 3 was studied in alpha-aged and omega-aged plates which were heat treated to similar strength levels. Tensile and plane strain fracture toughness tests were conducted at room temperature on the alpha-aged material. The microstructure and fracture mechanisms of alloys were studied using optical metallography, electron microscopy, microprobe analyses, and texture pole figures. Future experiments are described.

  16. Investigation of micro-structural phenomena at aggregate level in concretes using DEM

    Science.gov (United States)

    Nitka, Michał; Tejchman, Jacek

    2017-06-01

    This paper presents numerical analyses of concrete beams under three-point bending. The discrete element methods (DEM) was used to calculate fracture at the aggregate level. Concrete was described as a four-phase material, which was composed of aggregate, cement matrix, interfacial transitional zones (ITZs) and macro-voids. The beam micro-structure was directly taken from our experiments using x-ray micro-tomography. Simulations were carried out with real aggregate modelled as sphere clusters. Numerical results were compared with laboratory outcomes. The special attention was laid on the fracture propagation and some micro-structural phenomena at the aggregate level.

  17. Microstructural characterization of a composite Mo reinforced by 25 at.% TiC

    Energy Technology Data Exchange (ETDEWEB)

    Cedat, D. [Laboratoire de Mecanique des Sols, Structures et Materiaux, UMR 8579, Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry cedex (France); Rey, C. [Laboratoire de Mecanique des Sols, Structures et Materiaux, UMR 8579, Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry cedex (France)], E-mail: colette.rey@ecp.fr; Clavel, M.; Schmitt, J.H. [Laboratoire de Mecanique des Sols, Structures et Materiaux, UMR 8579, Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry cedex (France); Le Flem, M. [DEN/DANS/DMN/SRMA/LA2M, CEA, Centre de Saclay, 91191 Gif-sur-Yvette (France); Allemand, A. [DEN/DANS/DMN/SRMA/LTMEX, CEA, Centre de Saclay, 91191 Gif-sur-Yvette (France)

    2009-04-15

    In the scope of cermet development for structural pieces of future nuclear reactors (1000-1650 deg. C), Mo-TiC{sub 25at.%} was processed by hot isostatic pressure (HIP) and characterized in term of microstructure and chemical composition. The fabrication resulted in a three-phase material so called core/shell microstructure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, both coupled with X-ray detection (EDX), allowed to highlight the formation of TiC-Mo{sub 15at.%} phase at the TiC/Mo interface, in agreement with the phase diagram. The formation mechanisms of this phase are discussed.

  18. Microstructural changes due to laser surface melting of an AISI 304 stainless steel

    Directory of Open Access Journals (Sweden)

    d?Oliveira A.S.C.M.

    2001-01-01

    Full Text Available Several techniques can be used to improve surface properties. These can involve changes on the surface chemical composition (such as alloying and surface welding processes or on the surface microstructure, such as hardening and melting. In the present work surface melting with a 3kW CO2 cw laser was done to alter surface features of an AISI 304 stainless steel. Microstructure characterisation was done by optical and scanning electron microscopy. Vickers and Knoop microhardness tests evaluated mechanical features after surface melting. Phase transformation during rapid solidification is analysed and discussed.

  19. Microstructure Changes during Cavitation Erosion for a Steel with Metastable Austenite

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The characteristics of microstructure changes during cavitation erosion (CE) were investigatedby the use of XRD and TEM analyses for steel (ZG0Cr13Mn8N) with metastable austenite.The results show that the microstructure of the surface layer of the specimens consists of α'-martensite, metastable austenite and a few ε-martensite before CE. CE obviously increases dislocation density and straight or planar dislocations on the surface, and induces γ → ε, ε → α'and γ → α'-martensitic transformation.

  20. Hippocampus age-related microstructural changes in schizophrenia: a case-control mean diffusivity study.

    Science.gov (United States)

    Chiapponi, Chiara; Piras, Fabrizio; Fagioli, Sabrina; Girardi, Paolo; Caltagirone, Carlo; Spalletta, Gianfranco

    2014-08-01

    Macrostructural-volumetric abnormalities of the hippocampus have been described in schizophrenia. Here, we characterized age-related changes of hippocampal mean diffusivity as an index of microstructural damage by carrying out a neuroimaging study in 85 patients with a DSM-IV-TR diagnosis of schizophrenia and 85 age- and gender-matched healthy controls. We performed analyses of covariance, with diagnosis as fixed factor, mean diffusivity as dependent variable and age as covariate. Patients showed an early increase in mean diffusivity in the right and left hippocampus that increased with age. Thus, microstructural hippocampal changes associated with schizophrenia cannot be confined to a specific time window.

  1. Anisotropic microstructure near the sun

    Science.gov (United States)

    Coles, W. A.; Grall, R. R.; Spangler, S. R.; Sakurai, T.; Harmon, J. K.

    1996-07-01

    Radio scattering observations provide a means of measuring a two-dimensional projection of the three-dimensional spatial spectrum of electron density, i.e., in the plane perpendicular to the line of sight. Earlier observations have shown that the microstructure at scales of the order of 10 km becomes highly field-aligned inside of 10 Rsolar [Armstrong et al., 1990]. Earlier work has also shown that density fluctuations at scales larger than 1000 km have a Kolmogorov spectrum, whereas the smaller scale structure has a flatter spectrum and is considerably enhanced above the Kolmogorov ``background'' [Coles et al., 1991]. Here we present new observations made during 1990 and 1992. These confirm the earlier work, which was restricted to one source on a few days, but they suggest that the anisotropy changes abruptly near 6 Rsolar which was not clear in the earlier data. The axial ratio measurements are shown on Figure 1 below. The new observations were made with a more uniform sampling of the spatial plane. They show that contours of constant correlation are elliptical. This is apparently inconsistent with the spatial correlation of the ISEE-3 magnetic field which shows a ``Maltese Cross'' shape [Matthaeus et al., 1990]. However this inconsistency may be only apparent: the magnetic field and density correlations need not have the same shape; the scale of the magnetic field correlations is at least 4 orders of magnitude larger; they are much further from the sun; and they are point measurements whereas ours are path-integrated. We also made two simultaneous measurements, at 10 Rsolar, of the anisotropy on scales of 200 to 4000 km. Significant anisotropy was seen on the smaller scales, but the larger scale structure was essentially isotropic. This suggests that the process responsible for the anisotropic microstructure is independent of the larger scale isotropic turbulence. It is then tempting to speculate that the damping of this anisotropic process inside of 6 Rsolar

  2. Meta-analyses

    NARCIS (Netherlands)

    Hendriks, M.A.; Luyten, J.W.; Scheerens, J.; Sleegers, P.J.C.; Scheerens, J.

    2014-01-01

    In this chapter results of a research synthesis and quantitative meta-analyses of three facets of time effects in education are presented, namely time at school during regular lesson hours, homework, and extended learning time. The number of studies for these three facets of time that could be used

  3. Contesting Citizenship: Comparative Analyses

    DEFF Research Database (Denmark)

    Siim, Birte; Squires, Judith

    2007-01-01

    . Comparative citizenship analyses need to be considered in relation to multipleinequalities and their intersections and to multiple governance and trans-national organisinf. This, in turn, suggests that comparative citizenship analysis needs to consider new spaces in which struggles for equal citizenship occur...

  4. Wavelet Analyses and Applications

    Science.gov (United States)

    Bordeianu, Cristian C.; Landau, Rubin H.; Paez, Manuel J.

    2009-01-01

    It is shown how a modern extension of Fourier analysis known as wavelet analysis is applied to signals containing multiscale information. First, a continuous wavelet transform is used to analyse the spectrum of a nonstationary signal (one whose form changes in time). The spectral analysis of such a signal gives the strength of the signal in each…

  5. Report sensory analyses veal

    NARCIS (Netherlands)

    Veldman, M.; Schelvis-Smit, A.A.M.

    2005-01-01

    On behalf of a client of Animal Sciences Group, different varieties of veal were analyzed by both instrumental and sensory analyses. The sensory evaluation was performed with a sensory analytical panel in the period of 13th of May and 31st of May, 2005. The three varieties of veal were: young bull,

  6. Microstructure Modeling of Third Generation Disk Alloys

    Science.gov (United States)

    Jou, Herng-Jeng

    2010-01-01

    The objective of this program was to model, validate, and predict the precipitation microstructure evolution, using PrecipiCalc (QuesTek Innovations LLC) software, for 3rd generation Ni-based gas turbine disc superalloys during processing and service, with a set of logical and consistent experiments and characterizations. Furthermore, within this program, the originally research-oriented microstructure simulation tool was to be further improved and implemented to be a useful and user-friendly engineering tool. In this report, the key accomplishments achieved during the third year (2009) of the program are summarized. The activities of this year included: Further development of multistep precipitation simulation framework for gamma prime microstructure evolution during heat treatment; Calibration and validation of gamma prime microstructure modeling with supersolvus heat treated LSHR; Modeling of the microstructure evolution of the minor phases, particularly carbides, during isothermal aging, representing the long term microstructure stability during thermal exposure; and the implementation of software tools. During the research and development efforts to extend the precipitation microstructure modeling and prediction capability in this 3-year program, we identified a hurdle, related to slow gamma prime coarsening rate, with no satisfactory scientific explanation currently available. It is desirable to raise this issue to the Ni-based superalloys research community, with hope that in future there will be a mechanistic understanding and physics-based treatment to overcome the hurdle. In the mean time, an empirical correction factor was developed in this modeling effort to capture the experimental observations.

  7. Effects of rare earth oxide on hardfacing metal microstructure of medium carbon steel and its refinement mechanism

    Institute of Scientific and Technical Information of China (English)

    HAO Feifei; LIAO Bo; LI Da; LIU Ligang; DAN Ting; REN Xuejun; YANG Qingxiang

    2011-01-01

    The electrodes for hardfacing medium carbon steel with six additions of rare earth oxide were developed in this work. By means of optical microscopy and scanning electron microscopy, the microstructure, inclusion and the fractograph of the hardfacing metal were observed. Then, the effects of rare earth oxide on microstructure and inclusions in hardfacing metal were analyzed. The effectiveness of rare earth oxide as heterogeneous nuclei of δ-Fe was calculated with the misfit theory. The results showed that, the microstructure of hardfacing metal was composed of ferrite and small amount of pearlite. The microstructure was refined at first and then coarsened with the increase of rare earth oxide addition. The fractograph was changed from brittle to equiaxed dimples, then became quasi-cleavage and cleavage gradually.The calculated results showed that, the ferrite grain size could be refined because that LaA1O3 as heterogeneous nuclei ofδ-Fe was moderately effective, and the ferrite grain size was coarsened because the misfits between Ce2O3 and δ-Fe, Ce2O2S and δ-Fe were increased with futher increase of rare earth oxide addition.

  8. Modeling of Solidification Microstructures Based on Fully Coupling of Macro-transport Phenomena with Cellular Automata

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper has attempted to simulate the microstructure formation based on fully coupling of temperature field, concentration field and velocity field with micro-kinetics. The authors presented a new way, wlich is the combination of FDM and cellular automata (CAFD) to visualize the microstructure formation of the thin complex superalloy turbine blades cast by the vacuum investment process. The distribution, orientation and mechanism of the heterogeneous nucleation, the growth kinetics of dendrites and the columnar to equiaxed transition (CET) are considered. Capitalizing on these simulating schemes, the comprehensive influence of key process variables on the scale and uniformity of grains has been investigated quantitatively. The simulated grain size and morphology agree well with the experimental results.

  9. Characterization of heterogeneities from core X-ray scans and borehole wall images in a reefal carbonate reservoir: influence on the porosity structure.

    Science.gov (United States)

    Hebert, V.; Garing, C.; Pezard, P. A.; Gouze, P.; Maria-Sube, Y.; Camoin, G.; Lapointe, P.

    2009-04-01

    Petrophysical properties of rocks can be largely influenced by heterogeneities. This is particularly true in reefal carbonates, with heterogeneities due to the primary structure of the reef, the degradation of that structure into a fossil form, and fluid circulations with associated dissolutions and recrystallization. We report here a study conducted on Miocene reefal carbonates drilled in the context of salt water intrusion in coastal reservoirs. Salt water intrusion along coastlines is highly influenced by geological and petrophysical structures. In particular, heterogeneities and anisotropy in porous media (karsts, vugs…) control fluid flow and dispersion. A new experimental site has been developed in the South East of Mallorca Island (Spain) in the context of the ALIANCE EC project (2002-2005). This project aimed at developing a strategy for the quantitative analysis and description of fluid flow and salt transport in coastal carbonate aquifers. The site drilled the Miocene carbonate reef platform at Ses Sitjoles, 6 km inland, near the city of Campos. Sea water is found there at 60 to 80 m depth. The geological structure present multi-scale heterogeneities, often bound to either lateral variations of geological facies, or dissolution patterns. The Campos site provides a unique laboratory to study the heterogeneities of carbonate rocks with a saltwater intrusion and develop new borehole investigation methods in this context. The present study focuses on borehole geophysical measurements and images, and core scans. New image analysis methods have been developed to better characterize the presence of heterogeneities in terms of grain-size distribution, formation factor changes and porosity. Cores scans from RX tomography can lead to the extraction of petrophysical parameters from 3D images. For this, the AVIZO software was used here to represent the micro-porosity and vuggy porosity structure. Beyond core analyses, the optical and acoustic borehole wall images

  10. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number......A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...

  11. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    2014-01-01

    as well as the FEM calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of a sample constrained by a rigid substrate is simulated. The constrained sintering result in a larger number of pores near the substrate, as well as anisotropic sintering shrinkage......A numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress...

  12. Modeling the Microstructural Evolution During Constrained Sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    2015-01-01

    as well as the FEM calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of a sample constrained by a rigid substrate is simulated. The constrained sintering results in a larger number of pores near the substrate, as well as anisotropic sintering shrinkage......A numerical model able to simulate solid-state constrained sintering is presented. The model couples an existing kinetic Monte Carlo model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress...

  13. Effects of disordered microstructure and heat release on propagation of combustion front

    Directory of Open Access Journals (Sweden)

    Naine Tarun Bharath

    2016-05-01

    Full Text Available Numerical experiments for diagnosis of combustion of actual heterogeneous systems is performed on a one dimensional chain. The internal microstructure of actual heterogeneous systems is apriori unknown, various distributions like uniform, beta and normal have been considered for distributing neighboring reaction cells. Two cases, for the nature of distribution of heat release of reaction cells are taken into account, one with identical heat release and the other with disordered heat release. Role of different random distributions in describing heterogeneous combustion process are established in present paper. Particularly the normal distribution of arranging neighboring reaction cells has been found to be powerful methodology in explaining the combustion process of an actual heterogeneous system at higher ignition temperatures for both cases of distributing heat release. Validation of developed model with the experimental data of combustion of the CMDB propellants, gasless Ti+xSi system and different thermite mixtures is performed. Our results show that the experimental burning rates at higher ignition temperatures (ε>0.32 of the heterogeneous system are better reproduced theoretically with present model. We have also shown that different combustion limit for different thermite systems are the consequences of disordered heat release. Experimental data for thermite systems that have lower inflammability limits are analyzed in the view of disordered heat releases of cells. The model developed in the view of disordered heat releases reproduces the experimental burn rates and experimental combustion limit.

  14. Microstructural evolution at multiple scales during plastic deformation

    DEFF Research Database (Denmark)

    Winther, Grethe

    During plastic deformation metals develop microstructures which may be analysed on several scales, e.g. bulk textures, the scale of individual grains, intragranular phenomena in the form of orientation spreads as well as dislocation patterning by formation of dislocation boundaries in metals....... More specifically the origin of both inter- and intragranular orientation spread is analysed for a specific example from tensile deformed interstitial-free steel [Oddershede et al. 2015]. A universal framework for the patterns consisting of dislocation boundaries is presented for both fcc and bcc...... materials in several deformation modes, demonstrating a clear grain orientation dependence [Huang & Winther, 2007]. This dependence has its origin in a dependence on the slip systems [Winther & Huang, 2007]. This further implies that the dislocations in the boundaries come from the active slip systems...

  15. Possible future HERA analyses

    CERN Document Server

    Geiser, Achim

    2015-01-01

    A variety of possible future analyses of HERA data in the context of the HERA data preservation programme is collected, motivated, and commented. The focus is placed on possible future analyses of the existing $ep$ collider data and their physics scope. Comparisons to the original scope of the HERA programme are made, and cross references to topics also covered by other participants of the workshop are given. This includes topics on QCD, proton structure, diffraction, jets, hadronic final states, heavy flavours, electroweak physics, and the application of related theory and phenomenology topics like NNLO QCD calculations, low-x related models, nonperturbative QCD aspects, and electroweak radiative corrections. Synergies with other collider programmes are also addressed. In summary, the range of physics topics which can still be uniquely covered using the existing data is very broad and of considerable physics interest, often matching the interest of results from colliders currently in operation. Due to well-e...

  16. Analysing Access Control Specifications

    DEFF Research Database (Denmark)

    Probst, Christian W.; Hansen, René Rydhof

    2009-01-01

    . Recent events have revealed intimate knowledge of surveillance and control systems on the side of the attacker, making it often impossible to deduce the identity of an inside attacker from logged data. In this work we present an approach that analyses the access control configuration to identify the set......When prosecuting crimes, the main question to answer is often who had a motive and the possibility to commit the crime. When investigating cyber crimes, the question of possibility is often hard to answer, as in a networked system almost any location can be accessed from almost anywhere. The most...... of credentials needed to reach a certain location in a system. This knowledge allows to identify a set of (inside) actors who have the possibility to commit an insider attack at that location. This has immediate applications in analysing log files, but also nontechnical applications such as identifying possible...

  17. Biomass feedstock analyses

    Energy Technology Data Exchange (ETDEWEB)

    Wilen, C.; Moilanen, A.; Kurkela, E. [VTT Energy, Espoo (Finland). Energy Production Technologies

    1996-12-31

    The overall objectives of the project `Feasibility of electricity production from biomass by pressurized gasification systems` within the EC Research Programme JOULE II were to evaluate the potential of advanced power production systems based on biomass gasification and to study the technical and economic feasibility of these new processes with different type of biomass feed stocks. This report was prepared as part of this R and D project. The objectives of this task were to perform fuel analyses of potential woody and herbaceous biomasses with specific regard to the gasification properties of the selected feed stocks. The analyses of 15 Scandinavian and European biomass feed stock included density, proximate and ultimate analyses, trace compounds, ash composition and fusion behaviour in oxidizing and reducing atmospheres. The wood-derived fuels, such as whole-tree chips, forest residues, bark and to some extent willow, can be expected to have good gasification properties. Difficulties caused by ash fusion and sintering in straw combustion and gasification are generally known. The ash and alkali metal contents of the European biomasses harvested in Italy resembled those of the Nordic straws, and it is expected that they behave to a great extent as straw in gasification. Any direct relation between the ash fusion behavior (determined according to the standard method) and, for instance, the alkali metal content was not found in the laboratory determinations. A more profound characterisation of the fuels would require gasification experiments in a thermobalance and a PDU (Process development Unit) rig. (orig.) (10 refs.)

  18. Possible future HERA analyses

    Energy Technology Data Exchange (ETDEWEB)

    Geiser, Achim

    2015-12-15

    A variety of possible future analyses of HERA data in the context of the HERA data preservation programme is collected, motivated, and commented. The focus is placed on possible future analyses of the existing ep collider data and their physics scope. Comparisons to the original scope of the HERA pro- gramme are made, and cross references to topics also covered by other participants of the workshop are given. This includes topics on QCD, proton structure, diffraction, jets, hadronic final states, heavy flavours, electroweak physics, and the application of related theory and phenomenology topics like NNLO QCD calculations, low-x related models, nonperturbative QCD aspects, and electroweak radiative corrections. Synergies with other collider programmes are also addressed. In summary, the range of physics topics which can still be uniquely covered using the existing data is very broad and of considerable physics interest, often matching the interest of results from colliders currently in operation. Due to well-established data and MC sets, calibrations, and analysis procedures the manpower and expertise needed for a particular analysis is often very much smaller than that needed for an ongoing experiment. Since centrally funded manpower to carry out such analyses is not available any longer, this contribution not only targets experienced self-funded experimentalists, but also theorists and master-level students who might wish to carry out such an analysis.

  19. Microstructural evolution of castable during firing; Evolucao microestrural de concretos refratarios durante a queima

    Energy Technology Data Exchange (ETDEWEB)

    Santos, E.M.B.; Ribeiro, S., E-mail: esoly@ppgem.eel.usp.br [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia. Departamento de Engenharia de Materiais; Almeida, B.A.; Lopes, A.B. [Universidade de Aveiro (Portugal). Departamento de Ceramica e do Vidro (DECV)

    2011-07-01

    Castable are materials used for high temperature industrial applications, containing one or more binding agents, aggregates and additives. Calcium aluminate cement (CAC) is one of the most used binding agents, mainly due to his abundance, low cost, refractoriness and high mechanical and chemical resistance. During high temperature processes, these materials exhibit microstructural evolution that changes their properties and affect the performance. The purpose of this work was to study the microstructural changes presented by a castable, containing CAC and alumina aggregates, during heat treatment. For that, was used X-ray diffraction, thermal analyses, electron microscopy and energy dispersive spectroscopy to characterize concretes after heat treatment up to 1000 deg C. The results allowed to understand the microstructural changes at high temperature and its influence in mechanical properties of the castable. (author)

  20. Microstructure and properties degradation of P/T 91, 92 steels weldments in creep conditions

    Directory of Open Access Journals (Sweden)

    Falat L.

    2012-01-01

    Full Text Available The studies were performed on dissimilar ferritic/austenitic weldments between 9Cr tempered martensitic steels of the grades either P/T 91 or 92 and unstabilised AISI316H austenitic steel. The welded joints were fabricated using the fusion welding by tungsten inert gas (TIG method with Ni-based filler metal. Microstructural analyses were performed using light and electron microscopy. Microstructural gradient in heat-affected zone (HAZ of 9Cr steels remained preserved during creep exposure. All weldments fractured by the type IV failure within their intercritical HAZ (ICHAZ regions. The most remarkable microstructural change during creep was the precipitation of intermetallic Laves phase. Experimentally determined phases of the samples after creep exposure are in good agreement with equilibrium thermodynamic calculations.

  1. Analysis of composition and microstructural uniformity of hybrid glass/carbon fibre composites

    DEFF Research Database (Denmark)

    Beauson, Justine; Markussen, Christen Malte; Madsen, Bo

    2013-01-01

    In hybrid fibre composites, the intermixing of the two types of fibres imposes challenges to obtain materials with a well-defined and uniform microstructure. In the present paper, the composition and the microstructural uniformity of hybrid glass/carbon fibre composites mixed at the fibre bundle...... fibre volume fractions are determined using volumetric calculations. A model is presented to predict the interrelation of volume fractions in hybrid fibre composites. The microstructural uniformity of the composites is analysed by the determined variation in composite volume fractions. Two analytical...... level are investigated. The different levels of compositions in the composites are defined and experimentally determined. The composite volume fractions are determined using an image analysis based procedure. The global fibre volume fractions are determined using a gravimetrical based method. The local...

  2. Microstructure degradation of LSM-YSZ cathode in SOFCs operated at various conditions

    DEFF Research Database (Denmark)

    Liu, Yi-Lin; Thydén, Karl Tor Sune; Chen, Ming

    2012-01-01

    mechanisms have been identified. And it has been observed that different mechanisms dominate the degradation process under different test conditions. The severe cathode degradation at 750 °C operation with high current density is attributed to a loss of the cathode/electrolyte interface stability......Systematic microstructural analyses have been carried out on a series of technological SOFCs that went through long-term cell tests with various operating parameters including temperature, current load and time length under current. For the LSM-YSZ cathode, a number of microstructure degradation....... For the cells tested at 850 °C, the interface stability is maintained due to further sintering during cell operation. A cell test lasting for 2 years (17500 h) at 850 °C with a moderate current density (not greater than 1 A/cm2) has shown that the cathode microstructure is fairly robust to the degradation...

  3. Replikasi Unidirectional pada Heterogen Database

    Directory of Open Access Journals (Sweden)

    Hendro Nindito

    2013-12-01

    Full Text Available The use of diverse database technology in enterprise today can not be avoided. Thus, technology is needed to generate information in real time. The purpose of this research is to discuss a database replication technology that can be applied in heterogeneous database environments. In this study we use Windows-based MS SQL Server database to Linux-based Oracle database as the goal. The research method used is prototyping where development can be done quickly and testing of working models of the interaction process is done through repeated. From this research it is obtained that the database replication technolgy using Oracle Golden Gate can be applied in heterogeneous environments in real time as well.

  4. Seepage Anisotropy of Heterogeneous Body

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation.In an indoor experiment, a dump was constructed with three strata, where the horizontal and vertical seepage experiments were carried out.Horizontals flow are regarded as phreatic plan flows without penetration.Its seepage law satifies the Dupuit equation.With parallel lay seepage model, the equivalent seepage coefficient in the horizontal flow was obtained and was equivalent to the weighted mean of the seepage coefficient of each stratum.An unsaturated flow appeared in the vertical experiment, with a hydraulic gradient of 1.The vertical flow was equivalent to the seepage model that moved in vertical bedding; its equivalent seepage coefficient depended on the stratum with the minimum seepage coefficient.That the experiment showed clear anisotropy in a heterogeneous body was obvious with an anisotropic coefficient between 63 and 155, which is 25 to 100 times larger than that of a homogeneous body.

  5. Biodiesel production using heterogeneous catalysts.

    Science.gov (United States)

    Semwal, Surbhi; Arora, Ajay K; Badoni, Rajendra P; Tuli, Deepak K

    2011-02-01

    The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.

  6. DATABASE REPLICATION IN HETEROGENOUS PLATFORM

    Directory of Open Access Journals (Sweden)

    Hendro Nindito

    2014-01-01

    Full Text Available The application of diverse database technologies in enterprises today is increasingly a common practice. To provide high availability and survavibality of real-time information, a database replication technology that has capability to replicate databases under heterogenous platforms is required. The purpose of this research is to find the technology with such capability. In this research, the data source is stored in MSSQL database server running on Windows. The data will be replicated to MySQL running on Linux as the destination. The method applied in this research is prototyping in which the processes of development and testing can be done interactively and repeatedly. The key result of this research is that the replication technology applied, which is called Oracle GoldenGate, can successfully manage to do its task in replicating data in real-time and heterogeneous platforms.

  7. Temperature chaos and quenched heterogeneities

    Science.gov (United States)

    Barucca, Paolo; Parisi, Giorgio; Rizzo, Tommaso

    2014-03-01

    We present a treatable generalization of the Sherrington-Kirkpatrick (SK) model which introduces correlations in the elements of the coupling matrix through multiplicative disorder on the single variables and investigate the consequences on the phase diagram. We define a generalized qEA parameter and test the structural stability of the SK results in this correlated case evaluating the de Almeida-Thouless line of the model. As a main result we demonstrate the increase of temperature chaos effects due to heterogeneities.

  8. Surface fluxes in heterogeneous landscape

    Energy Technology Data Exchange (ETDEWEB)

    Bay Hasager, C.

    1997-01-01

    The surface fluxes in homogeneous landscapes are calculated by similarity scaling principles. The methodology is well establish. In heterogeneous landscapes with spatial changes in the micro scale range, i e from 100 m to 10 km, advective effects are significant. The present work focus on these effects in an agricultural countryside typical for the midlatitudes. Meteorological and satellite data from a highly heterogeneous landscape in the Rhine Valley, Germany was collected in the large-scale field experiment TRACT (Transport of pollutants over complex terrain) in 1992. Classified satellite images, Landsat TM and ERS SAR, are used as basis for roughness maps. The roughnesses were measured at meteorological masts in the various cover classes and assigned pixel by pixel to the images. The roughness maps are aggregated, i e spatially averaged, into so-called effective roughness lengths. This calculation is performed by a micro scale aggregation model. The model solves the linearized atmospheric flow equations by a numerical (Fast Fourier Transform) method. This model also calculate maps of friction velocity and momentum flux pixel wise in heterogeneous landscapes. It is indicated how the aggregation methodology can be used to calculate the heat fluxes based on the relevant satellite data i e temperature and soil moisture information. (au) 10 tabs., 49 ills., 223 refs.

  9. Analyzing and modeling heterogeneous behavior

    Science.gov (United States)

    Lin, Zhiting; Wu, Xiaoqing; He, Dongyue; Zhu, Qiang; Ni, Jixiang

    2016-05-01

    Recently, it was pointed out that the non-Poisson statistics with heavy tail existed in many scenarios of human behaviors. But most of these studies claimed that power-law characterized diverse aspects of human mobility patterns. In this paper, we suggest that human behavior may not be driven by identical mechanisms and can be modeled as a Semi-Markov Modulated Process. To verify our suggestion and model, we analyzed a total of 1,619,934 records of library visitations (including undergraduate and graduate students). It is found that the distribution of visitation intervals is well fitted with three sections of lines instead of the traditional power law distribution in log-log scale. The results confirm that some human behaviors cannot be simply expressed as power law or any other simple functions. At the same time, we divided the data into groups and extracted period bursty events. Through careful analysis in different groups, we drew a conclusion that aggregate behavior might be composed of heterogeneous behaviors, and even the behaviors of the same type tended to be different in different period. The aggregate behavior is supposed to be formed by "heterogeneous groups". We performed a series of experiments. Simulation results showed that we just needed to set up two states Semi-Markov Modulated Process to construct proper representation of heterogeneous behavior.

  10. Tunable Beam Diffraction in Infiltrated Microstructured Fibers

    DEFF Research Database (Denmark)

    Rosberg, Christian Romer; Bennet, Francis H.; Neshev, Dragomir N.;

    We experimentally study beam propagation in two dimensional photonic lattices in microstructured optical fibers infiltrated with high index liquids. We demonstrate strongly tunable beam diffraction by dynamically varying the coupling between individual lattice sites....

  11. Charnockite microstructures: From magmatic to metamorphic

    Directory of Open Access Journals (Sweden)

    Jacques L.R. Touret

    2012-11-01

    Full Text Available Charnockites sensu lato (charnockite-enderbite series are lower crustal felsic rocks typically characterised by the presence of anhydrous minerals including orthopyroxene and garnet. They either represent dry (H2O-poor felsic magmas that are emplaced in the lower crust or granitic intrusions that have been dehydrated during a subsequent granulite facies metamorphic event. In the first case, post-magmatic high-temperature recrystallisation may result in widespread metamorphic granulite microstructures, superimposed or replacing the magmatic microstructures. Despite recrystallisation, magmatic remnants may still be found, notably in the form of melt-related microstructures such as melt inclusions. For both magmatic charnockites and dehydrated granites, subsequent fluid-mineral interaction at intergrain boundaries during retrogradation are documented by microstructures including K-feldspar microveins and myrmekites. They indicate that a large quantity of low-H2O activity salt-rich brines, were present (together with CO2 under immiscible conditions in the lower crust.

  12. A microstructured Polymer Optical Fiber Biosensor

    DEFF Research Database (Denmark)

    Emiliyanov, Grigoriy Andreev; Jensen, Jesper Bo; Hoiby, Poul E.

    2006-01-01

    We demonstrate selective detection of fluorophore labeled antibodies from minute samples probed by a sensor layer of the complementary biomolecules immobilized inside the air holes of microstructured Polymer Optical Fibers....

  13. Microstructures of 2219 twin wire welded joints

    Institute of Scientific and Technical Information of China (English)

    Xu Wenli; Li Qingfen; Meng Qingguo; Gao Na; Fang Hongyuan

    2005-01-01

    With thick plates of 2219 high-strength alloy, the microstructures of welded joints with twin wire MIG welding were analyzed. Experimental results show that no hot crack was found in the weld due to discontinuous distribution of cocrystallization with low melting temperature, but porosity is serious in the first weld seam that is mainly composed of equiaxial grains with uneven sizes. As the poor position of the whole welded joint, fusion zone has big and coarse grains,uneven microstructures ; In quenching zone, there exist a lot of soaked microstructures that cocrystallization with low melting temperature solute into matrix, thus strengthening the metal in this zone; In excessive aging zone, much more phases that distribute evenly will be separated from the matrix; Outside this zone, properties and microstructures of the metal are basically similar to matrix due to the relatively low temperature or unaffected heat in the zone during welding.

  14. Fatigue modeling of materials with complex microstructures

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2011-01-01

    A new approach and method of the analysis of microstructure-lifetime relationships of materials with complex structures is presented. The micromechanical multiscale computational analysis of damage evolution in materials with complex hierarchical microstructures is combined with the phenomenologi......A new approach and method of the analysis of microstructure-lifetime relationships of materials with complex structures is presented. The micromechanical multiscale computational analysis of damage evolution in materials with complex hierarchical microstructures is combined...... with the phenomenological model of fatigue damage growth. As a result, the fatigue lifetime of materials with complex structures can be determined as a function of the parameters of their structures. As an example, the fatigue lifetimes of wood modeled as a cellular material with multilayered, fiber reinforced walls were...

  15. Heterogeneity in the multiple myeloma tumor clone

    NARCIS (Netherlands)

    Guikema, JEJ; Hovenga, S; Vellenga, E; Bos, NA

    2004-01-01

    Multiple Myeloma ( MM) is a plasma cell malignancy which is characterized by a very heterogeneous disease outcome. Heterogeneity in plasma cell characteristics, including morphology, maturation status, immunophenotype and genetic abnormalities partly account for the variable disease outcome. Althoug

  16. Heterogeneity in the multiple myeloma tumor clone

    NARCIS (Netherlands)

    Guikema, JEJ; Hovenga, S; Vellenga, E; Bos, NA

    Multiple Myeloma ( MM) is a plasma cell malignancy which is characterized by a very heterogeneous disease outcome. Heterogeneity in plasma cell characteristics, including morphology, maturation status, immunophenotype and genetic abnormalities partly account for the variable disease outcome.

  17. Dental microwear and microstructure in early oligocene primates from the Fayum, Egypt: implications for diet.

    Science.gov (United States)

    Teaford, M F; Maas, M C; Simons, E L

    1996-12-01

    Textbook descriptions usually portray the Fayum anthropoideans as frugivores, with Parapithecus grangeri including a folivorous component in its diet and Apidium a component of hard-object feeding. Recent work with modern mammals has shown that analyses of both dental microwear and dental microstructure may yield insights into diet and tooth use. The purpose of this study was to combine these two techniques to gain a better perspective on the paleobiology of the Fayum higher primates. Dental microwear analyses involved the use of high resolution epoxy casts of Aegyptopithecus, Parapithecus, and Apidium housed in the Duke University Primate Center. Scanning electron micrographs were taken at x500, and all microwear features in each micrograph were digitized. For microstructure analyses, molar teeth were sectioned in a variety of planes, lightly etched, and photographed in the SEM. Results of the dental microwear analyses indicate that the three Fayum anthropoideans all clustered with modern primate frugivores but that there were also significant differences between Aegyptopithecus and the other two Fayum genera. By contrast, dental microstructure analyses showed important differences between Apidium and the other two genera. The reason for these differences probably lies in a combination of body size and dietary differences, with Aegyptopithecus occasionally feeding on hard objects and Apidium maximizing wear resistance through a unique emphasis of radial (rather than decussating) enamel.

  18. CO{sub 2} corrosion resistance of carbon steel in relation with microstructure changes

    Energy Technology Data Exchange (ETDEWEB)

    Ochoa, Nathalie, E-mail: nochoa@usb.ve [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Vega, Carlos [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Pébère, Nadine; Lacaze, Jacques [Université de Toulouse, CIRIMAT, UPS/INPT/CNRS, ENSIACET, 4 Allée Emile Monso, CS 44362, 31030 Toulouse Cedex 4 (France); Brito, Joaquín L. [Laboratorio de Físico-química de Superficies, Centro de Química, Instituto Venezolano de Investigaciones Cientificas (IVIC), Carretera Panamericana, Km 11, Altos de Pipe, Estado Miranda (Venezuela, Bolivarian Republic of)

    2015-04-15

    The microstructural effects on the corrosion resistance of an API 5L X42 carbon steel in 0.5 M NaCl solution saturated with CO{sub 2} was investigated. Four microstructures were considered: banded (B), normalized (N), quenched and tempered (Q&T), and annealed (A). Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) were coupled with surface analyses (scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS)) to characterize the formation of the corrosion product layers. Electrochemical results revealed that corrosion resistance increased in the following order: B < N < Q&T < A. From the polarization curves it was shown that specifically, cathodic current densities were affected by microstructural changes. SEM images indicated that ferrite dissolved earlier than cementite and a thin layer of corrosion products was deposited on the steel surface. XPS analyses revealed that this layer was composed of a mixture of iron carbonate and non-dissolved cementite. It was also found that the quantity of FeCO{sub 3} content on the steel surface was greater for Q&T and A microstructures. These results, in agreement with the electrochemical data, indicate that the deposition mechanism of iron carbonate is closely related to the morphology of the non-dissolved cementite, determining the protective properties of the corrosion product layers. - Highlights: • The effect of change in microstructure on CO{sub 2} corrosion resistance was evaluated. • An API 5LX 42 carbon steel was immersed in a 0.5 M NaCl solution saturated with CO{sub 2}. • Banded, normalized, quenched-tempered and annealed microstructures were considered. • Electrochemical measurements were coupled with surface analysis. • Morphology and distribution of undissolved Fe{sub 3}C control corrosion kinetics.

  19. Helium isotopic systematics of oceanic islands and mantle heterogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Kurz, M.D.; Jenkins, W.J. (Woods Hole Oceanographic Institution, MA (USA)); Hart, S.R. (Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Earth and Planetary Sciences)

    1982-05-06

    The results of helium isotopic analyses in basaltic phenocrysts from the islands of Gough and Tristan da Cunha are reported which seem to indicate that the mantle beneath these islands are not primitive or undepleted relative to mid-ocean ridge basalt (MORB). New analyses from Loihi Seamount are also reported which do indicate a more primitive source. When these data are combined with values for MORBs previously obtained and plotted with respect to /sup 87/Sr//sup 86/Sr, the observed trends offer insight into the different source regions for oceanic island basalts and the nature of mantle heterogeneity.

  20. Personalized heterogeneous deformable model for fast volumetric registration.

    Science.gov (United States)

    Si, Weixin; Liao, Xiangyun; Wang, Qiong; Heng, Pheng Ann

    2017-02-20

    Biomechanical deformable volumetric registration can help improve safety of surgical interventions by ensuring the operations are extremely precise. However, this technique has been limited by the accuracy and the computational efficiency of patient-specific modeling. This study presents a tissue-tissue coupling strategy based on penalty method to model the heterogeneous behavior of deformable body, and estimate the personalized tissue-tissue coupling parameters in a data-driven way. Moreover, considering that the computational efficiency of biomechanical model is highly dependent on the mechanical resolution, a practical coarse-to-fine scheme is proposed to increase runtime efficiency. Particularly, a detail enrichment database is established in an offline fashion to represent the mapping relationship between the deformation results of high-resolution hexahedral mesh extracted from the raw medical data and a newly constructed low-resolution hexahedral mesh. At runtime, the mechanical behavior of human organ under interactions is simulated with this low-resolution hexahedral mesh, then the microstructures are synthesized in virtue of the detail enrichment database. The proposed method is validated by volumetric registration in an abdominal phantom compression experiments. Our personalized heterogeneous deformable model can well describe the coupling effects between different tissues of the phantom. Compared with high-resolution heterogeneous deformable model, the low-resolution deformable model with our detail enrichment database can achieve 9.4× faster, and the average target registration error is 3.42 mm, which demonstrates that the proposed method shows better volumetric registration performance than state-of-the-art. Our framework can well balance the precision and efficiency, and has great potential to be adopted in the practical augmented reality image-guided robotic systems.

  1. Frequency-dependent effective hydraulic conductivity of strongly heterogeneous media.

    Science.gov (United States)

    Caspari, E; Gurevich, B; Müller, T M

    2013-10-01

    The determination of the transport properties of heterogeneous porous rocks, such as an effective hydraulic conductivity, arises in a range of geoscience problems, from groundwater flow analysis to hydrocarbon reservoir modeling. In the presence of formation-scale heterogeneities, nonstationary flows, induced by pumping tests or propagating elastic waves, entail localized pressure diffusion processes with a characteristic frequency depending on the pressure diffusivity and size of the heterogeneity. Then, on a macroscale, a homogeneous equivalent medium exists, which has a frequency-dependent effective conductivity. The frequency dependence of the conductivity can be analyzed with Biot's equations of poroelasticity. In the quasistatic frequency regime of this framework, the slow compressional wave is a proxy for pressure diffusion processes. This slow compressional wave is associated with the out-of-phase motion of the fluid and solid phase, thereby creating a relative fluid-solid displacement vector field. Decoupling of the poroelasticity equations gives a diffusion equation for the fluid-solid displacement field valid in a poroelastic medium with spatial fluctuations in hydraulic conductivity. Then, an effective conductivity is found by a Green's function approach followed by a strong-contrast perturbation theory suggested earlier in the context of random dielectrics. This theory leads to closed-form expressions for the frequency-dependent effective conductivity as a function of the one- and two-point probability functions of the conductivity fluctuations. In one dimension, these expressions are consistent with exact solutions in both low- and high-frequency limits for arbitrary conductivity contrast. In 3D, the low-frequency limit depends on the details of the microstructure. However, the derived approximation for the effective conductivity is consistent with the Hashin-Shtrikman bounds.

  2. Controlling the appearance of specular microstructures

    OpenAIRE

    Sadeghi, Iman

    2011-01-01

    The focus of this dissertation is the appearance modeling of specular microstructures. We limit our study to microspheres, microcylinders, and a mesh of interwoven microcylinders. These microstructures are involved in the appearance of rainbows, hair, and cloth. There have been many studies on the appearance modeling of these three subjects. However, previous models either fail to reproduce specific appearances or they do so at the cost of time-consuming parameter tweaking. The main goal of t...

  3. Chalcogenide glass hollow core microstructured optical fibers

    Science.gov (United States)

    Shiryaev, Vladimir S.

    2015-03-01

    The recent developments on chalcogenide glass hollow core microstructured optical fibers (HC-MOFs) are presented. The comparative analysis of simulated optical properties for chalcogenide HC-MOFs of negative-curvature with different size and number of capillaries is given. The technique for the manufacture of microstructured chalcogenide preforms, which includes the assembly of the substrate glass tube and 8-10 capillaries, is described. Further trends to improve the optical transmission in chalcogenide NCHCFs are considered.

  4. Molecular heterogeneity in glioblastoma: potential clinical implications

    Directory of Open Access Journals (Sweden)

    Nicole Renee Parker

    2015-03-01

    Full Text Available Glioblastomas, (grade 4 astrocytomas, are aggressive primary brain tumors characterized by histopathological heterogeneity. High resolution sequencing technologies have shown that these tumors also feature significant inter-tumoral molecular heterogeneity. Molecular subtyping of these tumors has revealed several predictive and prognostic biomarkers. However, intra-tumoral heterogeneity may undermine the use of single biopsy analysis for determining tumor genotype and has implications for potential targeted therapies. The clinical relevance and theories of tumoral molecular heterogeneity in glioblastoma are discussed.

  5. Architecture and microstructure of cortical bone in reconstructed canine mandibles after bone transport distraction osteogenesis.

    Science.gov (United States)

    Zapata, Uriel; Halvachs, Emily K; Dechow, Paul C; Elsalanty, Mohammed E; Opperman, Lynne A

    2011-11-01

    Reconstruction of the canine mandible using bone transport distraction osteogenesis has been shown to be a suitable method for correcting segmental bone defects produced by cancer, gunshots, and trauma. Although the mechanical quality of the new regenerate cortical bone seems to be related to the mineralization process, several questions regarding the microstructural patterns of the new bony tissue remain unanswered. The purpose of this study was to quantify any microstructural differences that may exist between the regenerate and control cortical bone. Five adult American foxhound dogs underwent unilateral bone transport distraction of the mandible to repair bone defects of 30-35 mm. Animals were killed 12 weeks after the beginning of the consolidation period. Fourteen cylindrical cortical samples were extracted from the superior, medial, and inferior aspects of the lingual and buccal plates of the reconstructed aspect of the mandible, and 21 specimens were collected similarly from the contralateral aspect of the mandible. Specimens were evaluated using histomorphometric and micro-computed tomographic techniques to compare their microstructure. Except for differences in haversian canal area, histomorphometric analyses suggested no statistical differences in microstructure between regenerate and control cortical bone. Morphological evaluation suggested a consistent level of anisotropy, possibly related to the distraction vector. After 12 weeks' consolidation, bone created during bone transport distraction osteogenesis was comparable to native bone in microstructure, architecture, and mechanical properties. It is proposed that, after enough time, the properties of the regenerate bone will be identical to that of native bone.

  6. Thermally Induced Microstructural Transformations of Fe72Si15B8V4Cu1 Alloy

    Science.gov (United States)

    Vasić, Milica M.; Surla, Radoslav; Minić, Dušan M.; Radović, Ljubica; Mitrović, Nebojša; Maričić, Aleksa; Minić, Dragica M.

    2017-09-01

    Thermal stability, mechanism, and kinetics of thermally induced microstructural transformations and their effects on magnetic permeability of Fe72Si15B8V4Cu1 alloy with combined amorphous/nanocrystalline structure were studied. DTA curves revealed two separated thermally activated exothermic events in the temperature ranges from 740 K to 820 K (467 °C to 547 °C) and 870 K to 930 K (597 °C to 657 °C). Crystalline phases present in the as-prepared and thermally treated alloy samples were identified, and their microstructural parameters were determined using XRD, while, to gain further insight into the mechanism of microstructural transformations, AFM and SEM-EDS analyses were performed. Deconvolution of the complex DTA peak into individual steps was conducted, and, in correlation with the results of microstructural analysis, kinetic triplets corresponding to individual transformation steps were determined, allowing for the estimation of the lifetimes of the alloy at different temperatures. Magnetic permeability measurements showed that, in spite of the influence of microstructural transformations on magnetic properties of the alloy, the favorable magnetic properties are retained over relatively a wide temperature range.

  7. HLA region excluded by linkage analyses of early onset periodontitis

    Energy Technology Data Exchange (ETDEWEB)

    Sun, C.; Wang, S.; Lopez, N.

    1994-09-01

    Previous studies suggested that HLA genes may influence susceptibility to early-onset periodontitis (EOP). Segregation analyses indicate that EOP may be due to a single major gene. We conducted linkage analyses to assess possible HLA effects on EOP. Fifty families with two or more close relatives affected by EOP were ascertained in Virginia and Chile. A microsatellite polymorphism within the HLA region (at the tumor necrosis factor beta locus) was typed using PCR. Linkage analyses used a donimant model most strongly supported by previous studies. Assuming locus homogeneity, our results exclude a susceptibility gene within 10 cM on either side of our marker locus. This encompasses all of the HLA region. Analyses assuming alternative models gave qualitatively similar results. Allowing for locus heterogeneity, our data still provide no support for HLA-region involvement. However, our data do not statistically exclude (LOD <-2.0) hypotheses of disease-locus heterogeneity, including models where up to half of our families could contain an EOP disease gene located in the HLA region. This is due to the limited power of even our relatively large collection of families and the inherent difficulties of mapping genes for disorders that have complex and heterogeneous etiologies. Additional statistical analyses, recruitment of families, and typing of flanking DNA markers are planned to more conclusively address these issues with respect to the HLA region and other candidate locations in the human genome. Additional results for markers covering most of the human genome will also be presented.

  8. Microstructural study of multiaxial low cycle fatigue

    Directory of Open Access Journals (Sweden)

    Masao Sakane

    2015-07-01

    Full Text Available This paper discusses the relationship between the stress response and the microstructure under tension-torsion multiaxial proportional and nonproportional loadings. Firstly, this paper discusses the material dependency of additional hardening of FCC materials in relation with the stacking fault energy of the materials. The FCC materials studied were Type 304 stainless steel, pure copper, pure nickel, pure aluminum and 6061 aluminum alloy. The material with lower stacking fault energy showed stronger additional hardening, which was discussed in relation with slip morphology and dislocation structures. This paper, next, discusses dislocation structures of Type 304 stainless steel under proportional and nonproportional loadings at high temperature. The relationship between the microstructure and the hardening behavior whether isotropic or anisotropic was discussed. The re-arrangeability of dislocation structure was discussed in loading mode change tests. Microstructures of the steel was discussed in more extensively programmed multiaxial low cycle fatigue tests at room temperature, where three microstructures, dislocation bundle, stacking fault and cells, which were discussed in relation with the stress response. Finally, temperature dependence of the microstructure was discussed under proportional and nonproportional loadings, by comparing the microstructures observed at room and high temperatures.

  9. AMS analyses at ANSTO

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, E.M. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia). Physics Division

    1998-03-01

    The major use of ANTARES is Accelerator Mass Spectrometry (AMS) with {sup 14}C being the most commonly analysed radioisotope - presently about 35 % of the available beam time on ANTARES is used for {sup 14}C measurements. The accelerator measurements are supported by, and dependent on, a strong sample preparation section. The ANTARES AMS facility supports a wide range of investigations into fields such as global climate change, ice cores, oceanography, dendrochronology, anthropology, and classical and Australian archaeology. Described here are some examples of the ways in which AMS has been applied to support research into the archaeology, prehistory and culture of this continent`s indigenous Aboriginal peoples. (author)

  10. NMR CHARACTERIZATIONS OF PROPERTIES OF HETEROGENEOUS MEDIA

    Energy Technology Data Exchange (ETDEWEB)

    C.T. Philip Chang; Changho Choi; Jeromy T. Hollenshead; Rudi Michalak; Jack Phan; Ramon Saavedra; John C. Slattery; Jinsoo Uh; Randi Valestrand; A. Ted Watson; Song Xue

    2005-01-01

    A critical and long-standing need within the petroleum industry is the specification of suitable petrophysical properties for mathematical simulation of fluid flow in petroleum reservoirs (i.e., reservoir characterization). The development of accurate reservoir characterizations is extremely challenging. Property variations may be described on many scales, and the information available from measurements reflect different scales. In fact, experiments on laboratory core samples, well-log data, well-test data, and reservoir-production data all represent information potentially valuable to reservoir characterization, yet they all reflect information about spatial variations of properties at different scales. Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) provide enormous potential for developing new descriptions and understandings of heterogeneous media. NMR has the rare capability to probe permeable media non-invasively, with spatial resolution, and it provides unique information about molecular motions and interactions that are sensitive to morphology. NMR well-logging provides the best opportunity ever to resolve permeability distributions within petroleum reservoirs. We develop MRI methods to determine, for the first time, spatially resolved distributions of porosity and permeability within permeable media samples that approach the intrinsic scale: the finest resolution of these macroscopic properties possible. To our knowledge, this is the first time that the permeability is actually resolved at a scale smaller than the sample. In order to do this, we have developed a robust method to determine of relaxation distributions from NMR experiments and a novel implementation and analysis of MRI experiments to determine the amount of fluid corresponding to imaging regions, which are in turn used to determine porosity and saturation distributions. We have developed a novel MRI experiment to determine velocity distributions within flowing experiments, and

  11. Transfers in heterogeneous environments; Transferts en milieux heterogenes

    Energy Technology Data Exchange (ETDEWEB)

    Flesselles, J.M. [Saint-Gobain Recherche, 93 - Aubervilliers (France); Gouesbet, G.; Mees, L.; Roze, C.; Girasole, Th.; Grehan, G. [Laboratoire d' Electromagnetisme et Systemes Particulaires (LESP), UMR CNRS 6614, CORIA. Universite de Rouen et INSA de Rouen, 76 - Saint-Etienne du Rouvray (France); Goyheneche, J.M.; Vignoles, G.; Coindreau, O. [Laboratoire des Composites Thermostructuraux (LCTS), UMR 5801, 33 - Pessac (France); Moyne, Ch. [LEMTA (UMR 7563) CNRS-INPL-UHP, 54 - Vandoeuvre les Nancy (France); Coussy, O. [Institut Navier - ENPC, 77 - Marne-la-Vallee (France); Lassabatere, Th. [Electricite de France Les Renardieres, Dept. Materiaux Mecanique des Composants, 77 - Moret sur Loing (France); Tadrist, L. [IUSTI - UMR 6595, 13 - Marseille (France)

    2004-07-01

    This document gathers the articles and transparencies of the invited talks given at the 2004 French congress of thermal engineering about transfers in heterogeneous environment. Content: transfer phenomena in industrial glass furnaces; simple and multiple scattering diagnosis by femto-second pulsed laser: application to particulate diagnoses; thermal modeling of thermo-structural composites; hybrid mixtures theory, average volumic measurement, periodical or stochastic homogenization: advance in scale change processes; thermo-hydro-chemical-mechanical coupling in porous medium: application to young concrete structures and to clay barriers of disposal facilities; transfers and flows in fluidization: recent advances and future challenges. (J.S.)

  12. Property predictions using microstructural modeling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, K.G. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, CII 9219, 110 8th Street, Troy, NY 12180-3590 (United States)]. E-mail: wangk2@rpi.edu; Guo, Z. [Sente Software Ltd., Surrey Technology Centre, 40 Occam Road, Guildford GU2 7YG (United Kingdom); Sha, W. [Metals Research Group, School of Civil Engineering, Architecture and Planning, The Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom); Glicksman, M.E. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, CII 9219, 110 8th Street, Troy, NY 12180-3590 (United States); Rajan, K. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, CII 9219, 110 8th Street, Troy, NY 12180-3590 (United States)

    2005-07-15

    Precipitation hardening in an Fe-12Ni-6Mn maraging steel during overaging is quantified. First, applying our recent kinetic model of coarsening [Phys. Rev. E, 69 (2004) 061507], and incorporating the Ashby-Orowan relationship, we link quantifiable aspects of the microstructures of these steels to their mechanical properties, including especially the hardness. Specifically, hardness measurements allow calculation of the precipitate size as a function of time and temperature through the Ashby-Orowan relationship. Second, calculated precipitate sizes and thermodynamic data determined with Thermo-Calc[copyright] are used with our recent kinetic coarsening model to extract diffusion coefficients during overaging from hardness measurements. Finally, employing more accurate diffusion parameters, we determined the hardness of these alloys independently from theory, and found agreement with experimental hardness data. Diffusion coefficients determined during overaging of these steels are notably higher than those found during the aging - an observation suggesting that precipitate growth during aging and precipitate coarsening during overaging are not controlled by the same diffusion mechanism.

  13. Spatiotemporal Characterization of Extracellular Matrix Microstructures in Engineered Tissue: A Whole-Field Spectroscopic Imaging Approach.

    Science.gov (United States)

    Xu, Zhengbin; Ozcelikkale, Altug; Kim, Young L; Han, Bumsoo

    2013-02-01

    Quality and functionality of engineered tissues are closely related to the microstructures and integrity of their extracellular matrix (ECM). However, currently available methods for characterizing ECM structures are often labor-intensive, destructive, and limited to a small fraction of the total area. These methods are also inappropriate for assessing temporal variations in ECM structures. In this study, to overcome these limitations and challenges, we propose an elastic light scattering approach to spatiotemporally assess ECM microstructures in a relatively large area in a nondestructive manner. To demonstrate its feasibility, we analyze spectroscopic imaging data obtained from acellular collagen scaffolds and dermal equivalents as model ECM structures. For spatial characterization, acellular scaffolds are examined after a freeze/thaw process mimicking a cryopreservation procedure to quantify freezing-induced structural changes in the collagen matrix. We further analyze spatial and temporal changes in ECM structures during cell-driven compaction in dermal equivalents. The results show that spectral dependence of light elastically backscattered from engineered tissue is sensitively associated with alterations in ECM microstructures. In particular, a spectral decay rate over the wavelength can serve as an indicator for the pore size changes in ECM structures, which are at nanometer scale. A decrease in the spectral decay rate suggests enlarged pore sizes of ECM structures. The combination of this approach with a whole-field imaging platform further allows visualization of spatial heterogeneity of EMC microstructures in engineered tissues. This demonstrates the feasibility of the proposed method that nano- and micrometer scale alteration of the ECM structure can be detected and visualized at a whole-field level. Thus, we envision that this spectroscopic imaging approach could potentially serve as an effective characterization tool to nondestructively, accurately

  14. Sequence effects of twist extrusion and rolling on microstructure and mechanical properties of aluminum alloy 8112

    Energy Technology Data Exchange (ETDEWEB)

    Bahadori, Sh Ranjbar; Mousavi, S A A Akbari; Shahab, A R, E-mail: shrb1984@yahoo.co [School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran, Tehran, PO Box: 11155-4563 (Iran, Islamic Republic of)

    2010-07-01

    Recently severe plastic deformation processes have been the essence of metal forming researches to produce ultrafine-grained materials. Twist Extrusion (TE) is one of the most unprecedented methods developed in recent years, but remained in laboratory scales. The main reason for this matter refers to some deficiencies like microstructure heterogeneity occurring after TE. However, employing conventional forming techniques could make TE industrial and, moreover, reduce the bulk structure grain size. Using a conventional forming process such as rolling after twist extrusion has been suggested by this paper. T.E process of Al 8112 samples was carried out using a twisted die with 60{sup 0} die angle and the samples were processed through rolling subsequently. The results demonstrated that implementation of rolling not only reduced heterogeneity but also decreased the grain size and, consequently, enhanced the bulk strength.

  15. Cellular heterogeneity and molecular evolution in cancer.

    Science.gov (United States)

    Almendro, Vanessa; Marusyk, Andriy; Polyak, Kornelia

    2013-01-24

    Intratumor heterogeneity represents a major obstacle to effective cancer treatment and personalized medicine. However, investigators are now elucidating intratumor heterogeneity at the single-cell level due to improvements in technologies. Better understanding of the composition of tumors, and monitoring changes in cell populations during disease progression and treatment, will improve cancer diagnosis and therapeutic design. Measurements of intratumor heterogeneity may also be used as biomarkers to predict the risk of progression and therapeutic resistance. We summarize important considerations related to intratumor heterogeneity during tumor evolution. We also discuss experimental approaches that are commonly used to infer intratumor heterogeneity and describe how these methodologies can be translated into clinical practice.

  16. Analyse de "La banlieue"

    Directory of Open Access Journals (Sweden)

    Nelly Morais

    2006-11-01

    Full Text Available 1. Préambule - Conditions de réalisation de la présente analyse Un groupe d'étudiants de master 1 de FLE de l'université Paris 3 (donc des étudiants en didactique des langues se destinant à l'enseignement du FLE a observé le produit au cours d'un module sur les TIC (Technologies de l'Information et de la Communication et la didactique des langues. Une discussion s'est ensuite engagée sur le forum d'une plate-forme de formation à distance à partir de quelques questions posées par l'enseigna...

  17. EEG analyses with SOBI.

    Energy Technology Data Exchange (ETDEWEB)

    Glickman, Matthew R.; Tang, Akaysha (University of New Mexico, Albuquerque, NM)

    2009-02-01

    The motivating vision behind Sandia's MENTOR/PAL LDRD project has been that of systems which use real-time psychophysiological data to support and enhance human performance, both individually and of groups. Relevant and significant psychophysiological data being a necessary prerequisite to such systems, this LDRD has focused on identifying and refining such signals. The project has focused in particular on EEG (electroencephalogram) data as a promising candidate signal because it (potentially) provides a broad window on brain activity with relatively low cost and logistical constraints. We report here on two analyses performed on EEG data collected in this project using the SOBI (Second Order Blind Identification) algorithm to identify two independent sources of brain activity: one in the frontal lobe and one in the occipital. The first study looks at directional influences between the two components, while the second study looks at inferring gender based upon the frontal component.

  18. Cognitive heterogeneity in Williams syndrome.

    Science.gov (United States)

    Porter, Melanie A; Coltheart, Max

    2005-01-01

    This study used the Woodcock-Johnson Tests of Cognitive Ability-Revised to investigate a wide range of cognitive abilities in people with Williams syndrome (WS). It involved a comparatively large sample of 31 people with WS, but took a case-series approach. The study addressed the widespread claims of a characteristic "WS cognitive profile" by looking for heterogeneity rather than homogeneity. People with WS showed a variety of preserved (significantly above mental age [MA]), expected (at MA), and significantly impaired (significantly below MA) levels of functioning. Such results provide clear evidence for heterogeneity in cognitive functions within WS. We found the most homogeneity on a test of phonological processing and a test of phonological short-term memory, with half of the WS sample performing at MA levels on these tests. Interestingly, no WS individual showed a weakness on a test of nonverbal reasoning, and only one WS individual showed a weakness on a test of verbal comprehension. In addition, we found that strengths on analysis-synthesis and verbal analogies occurred only for WS individuals with an MA less than 5.5 years (our sample median MA); people with an MA greater than 5.5 years performed at MA level on these 2 tests. Results also provided preliminary evidence for distinct subgroups of WS people based on their cognitive strengths and weaknesses on a broad range of cognitive functions. On the basis of the findings, caution should be made in declaring a single cognitive profile that is characteristic of all individuals with WS. Just as there is heterogeneity in genetic and physical anomalies within WS, not all WS individuals share the same cognitive strengths and weaknesses. Also, not all WS individuals show the profile of a strength in verbal abilities and a weakness in spatial functions.

  19. Network class superposition analyses.

    Directory of Open Access Journals (Sweden)

    Carl A B Pearson

    Full Text Available Networks are often used to understand a whole system by modeling the interactions among its pieces. Examples include biomolecules in a cell interacting to provide some primary function, or species in an environment forming a stable community. However, these interactions are often unknown; instead, the pieces' dynamic states are known, and network structure must be inferred. Because observed function may be explained by many different networks (e.g., ≈ 10(30 for the yeast cell cycle process, considering dynamics beyond this primary function means picking a single network or suitable sample: measuring over all networks exhibiting the primary function is computationally infeasible. We circumvent that obstacle by calculating the network class ensemble. We represent the ensemble by a stochastic matrix T, which is a transition-by-transition superposition of the system dynamics for each member of the class. We present concrete results for T derived from boolean time series dynamics on networks obeying the Strong Inhibition rule, by applying T to several traditional questions about network dynamics. We show that the distribution of the number of point attractors can be accurately estimated with T. We show how to generate Derrida plots based on T. We show that T-based Shannon entropy outperforms other methods at selecting experiments to further narrow the network structure. We also outline an experimental test of predictions based on T. We motivate all of these results in terms of a popular molecular biology boolean network model for the yeast cell cycle, but the methods and analyses we introduce are general. We conclude with open questions for T, for example, application to other models, computational considerations when scaling up to larger systems, and other potential analyses.

  20. Microstructures, Forming Limit and Failure Analyses of Inconel 718 Sheets for Fabrication of Aerospace Components

    Science.gov (United States)

    Sajun Prasad, K.; Panda, Sushanta Kumar; Kar, Sujoy Kumar; Sen, Mainak; Murty, S. V. S. Naryana; Sharma, Sharad Chandra

    2017-02-01

    Recently, aerospace industries have shown increasing interest in forming limits of Inconel 718 sheet metals, which can be utilised in designing tools and selection of process parameters for successful fabrication of components. In the present work, stress-strain response with failure strains was evaluated by uniaxial tensile tests in different orientations, and two-stage work-hardening behavior was observed. In spite of highly preferred texture, tensile properties showed minor variations in different orientations due to the random distribution of nanoprecipitates. The forming limit strains were evaluated by deforming specimens in seven different strain paths using limiting dome height (LDH) test facility. Mostly, the specimens failed without prior indication of localized necking. Thus, fracture forming limit diagram (FFLD) was evaluated, and bending correction was imposed due to the use of sub-size hemispherical punch. The failure strains of FFLD were converted into major-minor stress space (σ-FFLD) and effective plastic strain-stress triaxiality space (ηEPS-FFLD) as failure criteria to avoid the strain path dependence. Moreover, FE model was developed, and the LDH, strain distribution and failure location were predicted successfully using above-mentioned failure criteria with two stages of work hardening. Fractographs were correlated with the fracture behavior and formability of sheet metal.

  1. Microstructures, Forming Limit and Failure Analyses of Inconel 718 Sheets for Fabrication of Aerospace Components

    Science.gov (United States)

    Sajun Prasad, K.; Panda, Sushanta Kumar; Kar, Sujoy Kumar; Sen, Mainak; Murty, S. V. S. Naryana; Sharma, Sharad Chandra

    2017-04-01

    Recently, aerospace industries have shown increasing interest in forming limits of Inconel 718 sheet metals, which can be utilised in designing tools and selection of process parameters for successful fabrication of components. In the present work, stress-strain response with failure strains was evaluated by uniaxial tensile tests in different orientations, and two-stage work-hardening behavior was observed. In spite of highly preferred texture, tensile properties showed minor variations in different orientations due to the random distribution of nanoprecipitates. The forming limit strains were evaluated by deforming specimens in seven different strain paths using limiting dome height (LDH) test facility. Mostly, the specimens failed without prior indication of localized necking. Thus, fracture forming limit diagram (FFLD) was evaluated, and bending correction was imposed due to the use of sub-size hemispherical punch. The failure strains of FFLD were converted into major-minor stress space ( σ-FFLD) and effective plastic strain-stress triaxiality space ( ηEPS-FFLD) as failure criteria to avoid the strain path dependence. Moreover, FE model was developed, and the LDH, strain distribution and failure location were predicted successfully using above-mentioned failure criteria with two stages of work hardening. Fractographs were correlated with the fracture behavior and formability of sheet metal.

  2. Fundamental concepts in heterogeneous catalysis

    CERN Document Server

    Norskov, Jens K; Abild-Pedersen, Frank; Bligaard, Thomas

    2014-01-01

    This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts.   Features include:First comprehensive description of modern theory of heterogeneous catalysisBasis for understanding and designing experiments in the field   Allows reader to understand catalyst design principlesIntroduction to important elements of energy transformation technologyTest driven at Stanford University over several semesters

  3. Heterogeneous photocatalysts in organic synthesis

    Science.gov (United States)

    Cherevatskaya, M.; König, B.

    2014-03-01

    The review deals with the application of inorganic semiconductors in organic synthesis. Although the majority of reported reactions still aim at the photocatalytic decomposition of organic compounds, the number of examples in synthetic applications is growing. The principal mechanisms of heterogeneous semiconductor photocatalysis are considered and examples illustrating the use of inorganic semiconductors in organic synthesis are given. The discussion is arranged according to the required excitation wavelength (UV or visible light) and to the new bond that is formed (carbon-carbon or carbon-heteroatom bond). The bibliography includes 47 references.

  4. Kinetics of heterogeneous catalytic reactions

    CERN Document Server

    Boudart, Michel

    2014-01-01

    This book is a critical account of the principles of the kinetics of heterogeneous catalytic reactions in the light of recent developments in surface science and catalysis science. Originally published in 1984. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase acc

  5. Computer Aided Design Modeling for Heterogeneous Objects

    CERN Document Server

    Gupta, Vikas; Tandon, Puneet

    2010-01-01

    Heterogeneous object design is an active research area in recent years. The conventional CAD modeling approaches only provide geometry and topology of the object, but do not contain any information with regard to the materials of the object and so can not be used for the fabrication of heterogeneous objects (HO) through rapid prototyping. Current research focuses on computer-aided design issues in heterogeneous object design. A new CAD modeling approach is proposed to integrate the material information into geometric regions thus model the material distributions in the heterogeneous object. The gradient references are used to represent the complex geometry heterogeneous objects which have simultaneous geometry intricacies and accurate material distributions. The gradient references helps in flexible manipulability and control to heterogeneous objects, which guarantees the local control over gradient regions of developed heterogeneous objects. A systematic approach on data flow, processing, computer visualizat...

  6. In-situ analysis of strain localization related to structural heterogeneities of carbonate rocks

    Directory of Open Access Journals (Sweden)

    Dimanov A.

    2010-06-01

    Full Text Available The technique of Digital Image Correlation (DIC has been applied to study the deformation of porous carbonate rocks subjected to uniaxial compression tests. The tests have been performed at two different scales: on cylinders of 10 cm high compressed with a standard press with digital images recorded by optical microscopy at a global and local scale and on smaller parallelepiped samples deformed inside a scanning electron microscope (SEM. The development of localization at different scales is thus recorded as well as the damage and compaction mechanisms in relation with the microstructural heterogeneities.

  7. Understanding particulate coating microstructure development

    Science.gov (United States)

    Roberts, Christine Cardinal

    How a dispersion of particulates suspended in a solvent dries into a solid coating often is more important to the final coating quality than even its composition. Essential properties like porosity, strength, gloss, particulate order, and concentration gradients are all determined by the way the particles come together as the coating dries. Cryogenic scanning electron microscopy (cryoSEM) is one of the most effective methods to directly visualize a drying coating during film formation. Using this method, the coating is frozen, arresting particulate motion and solidifying the sample so that it be imaged in an SEM. In this thesis, the microstructure development of particulate coatings was explored with several case studies. First, the effect of drying conditions was determined on the collapse of hollow latex particles, which are inexpensive whiteners for paint. Using cryoSEM, it was found that collapse occurs during the last stages of drying and is most likely to occur at high drying temperatures, humidity, and with low binder concentration. From these results, a theoretical model was proposed for the collapse of a hollow latex particle. CryoSEM was also used to verify a theoretical model for the particulate concentration gradients that may develop in a coating during drying for various evaporation, sedimentation and particulate diffusion rates. This work created a simple drying map that will allow others to predict the character of a drying coating based on easily calculable parameters. Finally, the effect of temperature on the coalescence and cracking of latex coatings was explored. A new drying regime for latex coatings was identified, where partial coalescence of particles does not prevent cracking. Silica was shown to be an environmentally friendly additive for preventing crack formation in this regime.

  8. Dislocations and deformation microstructure in a B2-ordered Al28Co20Cr11Fe15Ni26 high-entropy alloy.

    Science.gov (United States)

    Feuerbacher, Michael

    2016-07-19

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure.

  9. Dislocations and deformation microstructure in a B2-ordered Al28Co20Cr11Fe15Ni26 high-entropy alloy

    Science.gov (United States)

    Feuerbacher, Michael

    2016-07-01

    High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order, and due to their attractive properties are promising candidates for technological application. Many high-entropy alloys possess surprisingly high strength, occasionally in combination with high ductility and low density. The mechanisms effecting these attractive mechanical properties are not understood. This study addresses the deformation mechanism of a Al28Co20Cr11Fe15Ni26 high-entropy alloy, which is a two-phase material, consisting of a B2-ordered matrix and disordered body-centred inclusions. We quantitatively analyse the microstructure and dislocations in deformed samples by transmission-electron-microscopic methods including weak-beam imaging and convergent-beam electron diffraction. We find that the deformation process in the B2 phase is dominated by heterogeneous slip of screw dislocations gliding on planes. The dislocations are perfect superdislocations of the B2 lattice and show no dissociation. This indicates that the antiphase-boundary energy in the structure is very high, inhibiting spread of the dislocation core. Along with the observation of a widely extending strain field associated to the dislocations, our results provide a possible explanation for the high strength of this high-entropy alloy as a direct consequence of its dislocation structure.

  10. An assessment of upper mantle heterogeneity based on abyssal peridotite isotopic compositions

    Science.gov (United States)

    Warren, J. M.; Shimizu, N.; Sakaguchi, C.; Dick, H. J. B.; Nakamura, E.

    2009-12-01

    Abyssal peridotites, the depleted solid residues of ocean ridge melting, are the most direct samples available to assess upper oceanic mantle composition. We present detailed isotope and trace element analyses of pyroxene mineral separates from Southwest Indian Ridge abyssal peridotites and pyroxenites in order to constrain the size and length scale of mantle heterogeneity. Our results demonstrate that the mantle can be highly heterogeneous to account adequately for the complexities of ancient and recent melting processes.

  11. The influence of microstructure and operating temperature on the fatigue endurance of hot forged Inconel{sup ®} 718 components

    Energy Technology Data Exchange (ETDEWEB)

    Maderbacher, H., E-mail: hermann.maderbacher@unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Oberwinkler, B., E-mail: bernd.oberwinkler@bohler-forging.com [Böhler Schmiedetechnik GmbH and Co KG, Mariazellerstraße 25, 8605 Kapfenberg (Austria); Gänser, H.-P., E-mail: hans-peter.gaenser@mcl.at [Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben (Austria); Tan, W., E-mail: wen.tan@unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Rollett, M., E-mail: mathias.rollett@stud.unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Stoschka, M., E-mail: michael.stoschka@stud.unileoben.ac.at [Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria)

    2013-11-15

    The dependence of the fatigue behavior of hot-forged Inconel{sup ®} 718 aircraft components on the operating temperature and the material microstructure is investigated. To this purpose, possible correlations between a variety of tested microstructural parameters and the results from low-cycle fatigue (LCF) testing are analyzed using statistical methods. To identify the prevailing damage mechanisms, failure analyses are carried out on specimens tested at different temperatures. Optical and scanning electron microscopy are used for the inspection of surface crack networks and of the final fracture surface. In addition, energy dispersive X-ray (EDX) analyses are performed at the crack initiation sites to track down possible accumulations of alloying elements. The results are critically reviewed and used to propose a temperature and microstructure dependent fatigue model for predicting LCF ε⧸N-curves.

  12. Heterogeneous Transmutation Sodium Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    S. E. Bays

    2007-09-01

    The threshold-fission (fertile) nature of Am-241 is used to destroy this minor actinide by capitalizing upon neutron capture instead of fission within a sodium fast reactor. This neutron-capture and its subsequent decay chain leads to the breeding of even neutron number plutonium isotopes. A slightly moderated target design is proposed for breeding plutonium in an axial blanket located above the active “fast reactor” driver fuel region. A parametric study on the core height and fuel pin diameter-to-pitch ratio is used to explore the reactor and fuel cycle aspects of this design. This study resulted in both non-flattened and flattened core geometries. Both of these designs demonstrated a high capacity for removing americium from the fuel cycle. A reactivity coefficient analysis revealed that this heterogeneous design will have comparable safety aspects to a homogeneous reactor of comparable size. A mass balance analysis revealed that the heterogeneous design may reduce the number of fast reactors needed to close the current once-through light water reactor fuel cycle.

  13. Immunophenotype Heterogeneity in Nasal Glomangiopericytoma

    Directory of Open Access Journals (Sweden)

    Adriana Handra-Luca

    2015-01-01

    Full Text Available Nasal glomangiopericytoma is rare. The immunophenotype is heterogeneous, more frequently smooth-muscle-actin and CD34-positive. We report expression patterns for several vascular-related proteins such as CD99, CD146, Bcl2, and WT1 as well as for treatment-related proteins such as mTOR and EGFR in a nasal glomangiopericytoma. The patient (woman, 86 years presented with a left nasal tumefaction. The resected specimen (1.5-cm showed a glomangiopericytoma. Tumor cells expressed smooth-muscle-actin, CD31, CD34, and progesterone receptor. They also expressed the vascular-cell-related proteins Bcl2, CD99, CD146, and WT1, as well as mTOR and EGFR. Nasal glomangiopericytomas show immunohistochemical heterogeneity for vascular-related markers, suggesting a possible extensive pericytic differentiation. The expression of potential targets for drug treatments such as mTOR and EGFR may impact on the clinical follow-up of these tumors occurring at advanced ages, which may require complex surgery.

  14. Euhalophyte Eryngium maritimum L.: the Microstructure and Functional Characteristics

    Directory of Open Access Journals (Sweden)

    A.P. Ivanova

    2015-09-01

    Full Text Available The microstructure of the leaf surface, lipids composition, pigments spectrum, biological and photosynthetic activity, and hormones status of euhalophyte Eryngium maritimum L., one of the most salt-tolerant plants, were studied. It was shown that the existence in saline and dry soils is provided among others adaptive mechanisms by specific microstructure of leaf, adaxial and abaxial surfaces of which have well-developed cuticle and stomata slit placed below the surface of the epidermis. The presence of a large amount of saturated fatty acids provides decrease of membrane permeability and better resistance against soil salinity. The key role in photosynthetic activity is played by chlorophyll a. At the same time a high amount of carotenoids (as compared with amount of chlorophylls points out that these pigments have a light-collecting function and could transfer an additional energy to chlorophylls. The data from thermoluminescence analyses showed a possible inhibition of recombination reactions in PS II by the assumed saline concentration in plant tissue. Besides, the fluorescence measurements indicate reduced efficiency of photosynthetic reactions. The high level of active ABA is correlated with salt tolerance and ability to survive and grow in stress conditions. The high level of conjugated form of IAA demonstrated that activity of this hormone is limited.

  15. Longitudinal changes in white matter microstructure after heavy cannabis use

    Directory of Open Access Journals (Sweden)

    Mary P. Becker

    2015-12-01

    Full Text Available Diffusion tensor imaging (DTI studies of cannabis users report alterations in brain white matter microstructure, primarily based on cross-sectional research, and etiology of the alterations remains unclear. We report findings from longitudinal voxelwise analyses of DTI data collected at baseline and at a 2-year follow-up on 23 young adult (18–20 years old at baseline regular cannabis users and 23 age-, sex-, and IQ-matched non-using controls with limited substance use histories. Onset of cannabis use was prior to age 17. Cannabis users displayed reduced longitudinal growth in fractional anisotropy in the central and parietal regions of the right and left superior longitudinal fasciculus, in white matter adjacent to the left superior frontal gyrus, in the left corticospinal tract, and in the right anterior thalamic radiation lateral to the genu of the corpus callosum, along with less longitudinal reduction of radial diffusion in the right central/posterior superior longitudinal fasciculus, corticospinal tract, and posterior cingulum. Greater amounts of cannabis use were correlated with reduced longitudinal growth in FA as was relatively impaired performance on a measure of verbal learning. These findings suggest that continued heavy cannabis use during adolescence and young adulthood alters ongoing development of white matter microstructure, contributing to functional impairment.

  16. Hypoparathyroidism: clinical features, skeletal microstructure and parathyroid hormone replacement

    Science.gov (United States)

    Rubin, Mishaela R.; Bilezikian, John P.

    2013-01-01

    Objective Hypoparathyroidism is a disorder in which parathyroid hormone is deficient in the circulation due most often to immunological destruction of the parathyroids or to their surgical removal. The objective of this work was to define the abnormalities in skeletal microstructure as well as to establish the potential efficacy of PTH(1-84) replacement in this disorder. Subjects and methods Standard histomorphometric and μCT analyses were performed on iliac crest bone biopsies obtained from patients with hypoparathyroidism. Participants were treated with PTH(1-84) for two years. Results Bone density was increased and skeletal features reflected the low turnover state with greater BV/TV, Tb. Wi and Ct. Wi as well as suppressed MS and BFR/BS as compared to controls. With PTH(1-84), bone turnover and bone mineral density increased in the lumbar spine. Requirements for calcium and vitamin D fell while serum and urinary calcium concentrations did not change. Conclusion Abnormal microstructure of the skeleton in hypoparathyroidism reflects the absence of PTH. Replacement therapy with PTH has the potential to correct these abnormalities as well as to reduce the requirements for calcium and vitamin D. PMID:20485912

  17. Longitudinal changes in white matter microstructure after heavy cannabis use.

    Science.gov (United States)

    Becker, Mary P; Collins, Paul F; Lim, Kelvin O; Muetzel, R L; Luciana, M

    2015-12-01

    Diffusion tensor imaging (DTI) studies of cannabis users report alterations in brain white matter microstructure, primarily based on cross-sectional research, and etiology of the alterations remains unclear. We report findings from longitudinal voxelwise analyses of DTI data collected at baseline and at a 2-year follow-up on 23 young adult (18-20 years old at baseline) regular cannabis users and 23 age-, sex-, and IQ-matched non-using controls with limited substance use histories. Onset of cannabis use was prior to age 17. Cannabis users displayed reduced longitudinal growth in fractional anisotropy in the central and parietal regions of the right and left superior longitudinal fasciculus, in white matter adjacent to the left superior frontal gyrus, in the left corticospinal tract, and in the right anterior thalamic radiation lateral to the genu of the corpus callosum, along with less longitudinal reduction of radial diffusion in the right central/posterior superior longitudinal fasciculus, corticospinal tract, and posterior cingulum. Greater amounts of cannabis use were correlated with reduced longitudinal growth in FA as was relatively impaired performance on a measure of verbal learning. These findings suggest that continued heavy cannabis use during adolescence and young adulthood alters ongoing development of white matter microstructure, contributing to functional impairment.

  18. Pharmacogenomics Bias - Systematic distortion of study results by genetic heterogeneity

    Directory of Open Access Journals (Sweden)

    Zietemann, Vera

    2008-04-01

    Full Text Available Background: Decision analyses of drug treatments in chronic diseases require modeling the progression of disease and treatment response beyond the time horizon of clinical or epidemiological studies. In many such models, progression and drug effect have been applied uniformly to all patients; heterogeneity in progression, including pharmacogenomic effects, has been ignored. Objective: We sought to systematically evaluate the existence, direction and relative magnitude of a pharmacogenomics bias (PGX-Bias resulting from failure to adjust for genetic heterogeneity in both treatment response (HT and heterogeneity in progression of disease (HP in decision-analytic studies based on clinical study data. Methods: We performed a systematic literature search in electronic databases for studies regarding the effect of genetic heterogeneity on the validity of study results. Included studies have been summarized in evidence tables. In the case of lacking evidence from published studies we sought to perform our own simulation considering both HT and HP. We constructed two simple Markov models with three basic health states (early-stage disease, late-stage disease, dead, one adjusting and the other not adjusting for genetic heterogeneity. Adjustment was done by creating different disease states for presence (G+ and absence (G- of a dichotomous genetic factor. We compared the life expectancy gains attributable to treatment resulting from both models and defined pharmacogenomics bias as percent deviation of treatment-related life expectancy gains in the unadjusted model from those in the adjusted model. We calculated the bias as a function of underlying model parameters to create generic results. We then applied our model to lipid-lowering therapy with pravastatin in patients with coronary atherosclerosis, incorporating the influence of two TaqIB polymorphism variants (B1 and B2 on progression and drug efficacy as reported in the DNA substudy of the REGRESS

  19. Website-analyse

    DEFF Research Database (Denmark)

    Thorlacius, Lisbeth

    2009-01-01

    planlægning af de funktionelle og indholdsmæssige aspekter ved websites. Der findes en stor mængde teori- og metodebøger, som har specialiseret sig i de tekniske problemstillinger i forbindelse med interaktion og navigation, samt det sproglige indhold på websites. Den danske HCI (Human Computer Interaction...... hyperfunktionelle websites. Det primære ærinde for HCI-eksperterne er at udarbejde websites, som er brugervenlige. Ifølge deres direktiver skal websites være opbygget med hurtige og effektive navigations- og interaktionsstrukturer, hvor brugeren kan få sine informationer ubesværet af lange downloadingshastigheder...... eller blindgyder, når han/hun besøger sitet. Studier i design og analyse af de visuelle og æstetiske aspekter i planlægning og brug af websites har imidlertid kun i et begrænset omfang været under reflektorisk behandling. Det er baggrunden for dette kapitel, som indleder med en gennemgang af æstetikkens...

  20. Roundness of grains in cellular microstructures

    Science.gov (United States)

    Lutz, F. H.; Mason, J. K.; Lazar, E. A.; MacPherson, R. D.

    2017-08-01

    Many physical systems are composed of polyhedral cells of varying sizes and shapes. These structures are simple in the sense that no more than three faces meet at an edge and no more than four edges meet at a vertex. This means that individual cells can usually be considered as simple, three-dimensional polyhedra. This paper is concerned with determining the distribution of combinatorial types of such polyhedral cells. We introduce the terms fundamental and vertex-truncated types and apply these concepts to the grain growth microstructure as a testing ground. For these microstructures, we demonstrate that most grains are of particular fundamental types, whereas the frequency of vertex-truncated types decreases exponentially with the number of truncations. This can be explained by the evolutionary process through which grain growth structures are formed and in which energetically unfavorable surfaces are quickly eliminated. Furthermore, we observe that these grain types are "round" in a combinatorial sense: there are no "short" separating cycles that partition the polyhedra into two parts of similar sizes. A particular microstructure derived from the Poisson-Voronoi initial condition is identified as containing an unusually large proportion of round grains. This microstructure has an average of 14.036 faces per grain and is conjectured to be more resistant to topological change than the steady-state grain growth microstructure.

  1. The evolution of dinosaur tooth enamel microstructure.

    Science.gov (United States)

    Hwang, Sunny H

    2011-02-01

    The evolution of tooth enamel microstructure in both extinct and extant mammalian groups has been extensively documented, but is poorly known in reptiles, including dinosaurs. Previous intensive sampling of dinosaur tooth enamel microstructure revealed that: (1) the three-dimensional arrangement of enamel types and features within a tooth-the schmelzmuster-is most useful in diagnosing dinosaur clades at or around the family level; (2) enamel microstructure complexity is correlated with tooth morphology complexity and not necessarily with phylogenetic position; and (3) there is a large amount of homoplasy within Theropoda but much less within Ornithischia. In this study, the examination of the enamel microstructure of 28 additional dinosaur taxa fills in taxonomic gaps of previous studies and reinforces the aforementioned conclusions. Additionally, these new specimens reveal that within clades such as Sauropodomorpha, Neotheropoda, and Euornithopoda, the more basal taxa have simpler enamel that is a precursor to the more complex enamel of more derived taxa and that schmelzmusters evolve in a stepwise fashion. In the particularly well-sampled clade of Euornithopoda, correlations between the evolution of dental and enamel characters could be drawn. The ancestral schmelzmuster for Genasauria remains ambiguous due to the dearth of basal ornithischian teeth available for study. These new specimens provide new insights into the evolution of tooth enamel microstructure in dinosaurs, emphasizing the importance of thorough sampling within broadly inclusive clades, especially among their more basal members.

  2. A Modified SPH Method for Dynamic Failure Simulation of Heterogeneous Material

    Directory of Open Access Journals (Sweden)

    G. W. Ma

    2014-01-01

    Full Text Available A modified smoothed particle hydrodynamics (SPH method is applied to simulate the failure process of heterogeneous materials. An elastoplastic damage model based on an extension form of the unified twin shear strength (UTSS criterion is adopted. Polycrystalline modeling is introduced to generate the artificial microstructure of specimen for the dynamic simulation of Brazilian splitting test and uniaxial compression test. The strain rate effect on the predicted dynamic tensile and compressive strength is discussed. The final failure patterns and the dynamic strength increments demonstrate good agreements with experimental results. It is illustrated that the polycrystalline modeling approach combined with the SPH method is promising to simulate more complex failure process of heterogeneous materials.

  3. On the heterogeneity of stratified-shear turbulence: Observations from a near-field river plume

    Science.gov (United States)

    MacDonald, Daniel G.; Carlson, Joshua; Goodman, Louis

    2013-11-01

    The heterogeneity of turbulent structure in a near-field river plume is evaluated through the application of three distinct measurement techniques: turbulent overturn analysis, direct turbulence measurement using microstructure sensors mounted on an autonomous underwater vehicle (AUV), and a larger scale control volume approach. These techniques exploit the preturbulent potential energy available for conversion to turbulent energy, the kinetic energy associated with active turbulence, and the artifacts of turbulence demonstrated through a modified density structure, respectively. Comparisons between these methods indicate that all three techniques can provide robust estimates of mean turbulent kinetic energy dissipation rates. Results suggest a highly heterogeneous turbulent field, with significant overturns occupying a volume fraction of less than 10%, and active turbulence occupying a volume fraction only 2-3 times larger. The combined data sets are also used to estimate expected means and confidence limits for overturn-derived dissipation rates associated with varying sample sizes.

  4. Simulation of heterogeneous two-phase media using random fields and level sets

    Institute of Scientific and Technical Information of China (English)

    George STEFANOU[1,2

    2015-01-01

    The accurate and efficient simulation of random heterogeneous media is important in the framework of modeling and design of complex materials across multiple length scales. It is usually assumed that the morphology of a random microstructure can be described as a non-Gaussian random field that is completely defined by its multivariate distribution. A particular kind of non-Gaussian random fields with great practical importance is that of translation fields resulting from a simple memory-less transformation of an underlying Gaussian field with known second-order statistics. This paper provides a critical examination of existing random field models of heterogeneous two-phase media with emphasis on level-cut random fields which are a special case of translation fields. The case of random level sets, often used to represent the geometry of physical systems, is also examined. Two numerical examples are provided to illustrate the basic features of the different approaches.

  5. Evolution of heterogeneity (I2) estimates and their 95% confidence intervals in large meta-analyses

    DEFF Research Database (Denmark)

    Thorlund, Kristian; Imberger, Georgina; Johnston, Bradley C

    2012-01-01

    by sampling error. Recent studies have raised concerns about the reliability of I(2) estimates, due to their dependence on the precision of included trials and time-dependent biases. Authors have also advocated use of 95% confidence intervals (CIs) to express the uncertainty associated with I(2) estimates...

  6. Characterization from borehole wall and X-ray scan images of heterogeneities in carbonate reservoirs

    Science.gov (United States)

    Hébert, V.; Pezard, P. A.; Garing, C.; Gouze, P.; Camoin, G.; Lapointe, P.

    2009-12-01

    Salt water intrusion in coastal reservoirs is highly influenced by geological and petrophysical structures. In particular, heterogeneities and anisotropy in porous media (karst, vug) control fluid transport and dispersion. To develop new strategies for the quantitative description and analysis of fluid flow and salt transport in coastal aquifers, a new experimental site was developed in SE Mallorca (Spain) in the context of the ALIANCE EC project (2002-2005). Multi-scalar quantitative and descriptive methods (from µm to m) are developed to identify and map microstructures, heterogeneities and their hydrogeological impact on the reservoir. The objective of this study is to better understand the link between geological and hydrogeological properties of heterogeneous reservoir. The Mallorcan site cuts the Miocene carbonate reef platform and is located 6 km inland, where a salt wedge transition is found from 60 to 80 m depth. The geological structure includes large multi-scale heterogeneities, often bound to lateral facies variations. This experimental site provides thus a unique laboratory to study saltwater intrusion processes and develop new downhole investigation methods. This study focuses on borehole geophysical measurements and images, and X-ray core scan images. New image analysis methods have been developed to better characterize heterogeneities in terms of size distribution, aspect ratio and porosity. Optical and acoustic borehole wall images offer a continuous insight into meso-scale porosity (such as karstic channels and megapores) from mm to 100 m scale. X-ray cores scans were obtained from a tomography scanner by TOTAL. These two methodologies from RX tomography scans and borehole wall images are compared and discussed. Petrophysical parameters were extracted from X-ray images with a dedicated 3D data analysis software. The scan images lead to the identification and quantification of the micro- and vuggy porosity. It is found that the distribution of

  7. Study of crack propagation mechanisms during Charpy impact toughness tests on both equiaxed and lamellar microstructures of Ti–6Al–4V titanium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Buirette, Christophe, E-mail: christophe.buirette@ensiacet.fr [Institut Carnot CIRIMAT, ENSIACET, 4 allée Emile Monso, 31030 Toulouse (France); Huez, Julitte, E-mail: julitte.huez@ensiacet.fr [Institut Carnot CIRIMAT, ENSIACET, 4 allée Emile Monso, 31030 Toulouse (France); Gey, Nathalie, E-mail: Nathalie.gey@univ-lorraine.fr [Laboratoire d’Etude des Microstructures et de Mécanique des Matériaux (LEM3), UMR CNRS 7239, Université de Lorraine, Île du Saulcy, 57045 METZ Cedex 1 (France); DAMAS, Laboratory of Excellence on Design of Alloy Metals for Low-Mass Structures, Université de Lorraine (France); Vassel, Alain, E-mail: alain.vassel@titane.asso.fr [Association Française du Titane, 16 quai Ernest Renaud, BP 70515, 44105 Nantes Cedex 4 (France); Andrieu, Eric, E-mail: eric.andrieu@ensiacet.fr [Institut Carnot CIRIMAT, ENSIACET, 4 allée Emile Monso, 31030 Toulouse (France)

    2014-11-17

    The impact toughness of two highly textured rolled plates of Ti–6Al–4V alloy with an α equiaxed and an α lamellar microstructures has been investigated. The results show a strong anisotropy of the fracture energy for both materials and underline that a coincidence of the prismatic planes with the shear bands at the notch tip is favorable for higher fracture energies. Moreover, it is pointed out, as it was already done by previous studies, that the α lamellar microstructure presents higher fracture energy than the α equiaxed one. Thanks to electron back scattering diffraction, and tensile tests, local microstructure heterogeneities, called macrozones, have been observed and characterized. Their size depends on microstructure element and is larger for α lamellar microstructure than for the α equiaxed. High strain is localized on the macrozones favorably oriented for prismatic slip with respect to the direction of impact and leads to a particular dimple free zone on the fracture surface. The contribution of these macrozones in the fracture behavior, and more precisely on the crack propagation rate was evaluated; thus the effects of the macroscopic texture and of the microstructure element on the impact toughness are discussed separately.

  8. Realized Variance and Market Microstructure Noise

    DEFF Research Database (Denmark)

    Hansen, Peter R.; Lunde, Asger

    2006-01-01

    We study market microstructure noise in high-frequency data and analyze its implications for the realized variance (RV) under a general specification for the noise. We show that kernel-based estimators can unearth important characteristics of market microstructure noise and that a simple kernel......-based estimator dominates the RV for the estimation of integrated variance (IV). An empirical analysis of the Dow Jones Industrial Average stocks reveals that market microstructure noise its time-dependent and correlated with increments in the efficient price. This has important implications for volatility...... estimation based on high-frequency data. Finally, we apply cointegration techniques to decompose transaction prices and bid-ask quotes into an estimate of the efficient price and noise. This framework enables us to study the dynamic effects on transaction prices and quotes caused by changes in the efficient...

  9. Discriminating Yogurt Microstructure Using Diffuse Reflectance Images

    DEFF Research Database (Denmark)

    Skytte, Jacob Lercke; Møller, Flemming; Abildgaard, Otto Højager Attermann;

    2015-01-01

    modalities is evaluated on a 24 factorial design covering four common production parameters, which significantly change the chemistry and the microstructure of the yogurt. It is found that the DRIs can be as discriminative as the CSLM images in certain cases, however the performance is highly governed...... microstructures using hyperspectral (500-900nm) diffuse reflectance images (DRIs) – a technique potentially well suited for inline process control. Comparisons are made to quantified measures of the yogurt microstructure observed through confocal scanning laser microscopy (CSLM). The output signal from both...... by the chemistry of the sample. Also, the DRIs shows better correlation to the CSLM images and are more discriminative when considering shorter wavelengths....

  10. Microstructural path analysis of martensite burst

    Directory of Open Access Journals (Sweden)

    Paulo Rangel Rios

    2010-03-01

    Full Text Available Modeling the martensite reaction requires reckoning with spatial aspects of the reaction. For that, we used formal kinetics, more specifically, the microstructural path method (MPM to analyze the microstructure observed in a burst. The microstructural path analysis revealed that the size of the spread cluster in extended space, characterized by the Vandermeer and Juul-Jensen's impingement compensated mean intercept length, λG, remained constant, independently of the parent austenite grain size. Moreover, current analysis introduced a purely formal description of the reaction progress by taking the parent austenite grain size as the progress variable. This description worked very well and resulted in a relationship between the volume fraction of partially transformed austenite, V VG, and austenite grain size, λG. The significance of these findings in the light of the advantages and disadvantages of formal kinetics is discussed.

  11. Realized Variance and Market Microstructure Noise

    DEFF Research Database (Denmark)

    Hansen, Peter R.; Lunde, Asger

    2006-01-01

    We study market microstructure noise in high-frequency data and analyze its implications for the realized variance (RV) under a general specification for the noise. We show that kernel-based estimators can unearth important characteristics of market microstructure noise and that a simple kernel......-based estimator dominates the RV for the estimation of integrated variance (IV). An empirical analysis of the Dow Jones Industrial Average stocks reveals that market microstructure noise its time-dependent and correlated with increments in the efficient price. This has important implications for volatility...... estimation based on high-frequency data. Finally, we apply cointegration techniques to decompose transaction prices and bid-ask quotes into an estimate of the efficient price and noise. This framework enables us to study the dynamic effects on transaction prices and quotes caused by changes in the efficient...

  12. Diffraction analysis of the microstructure of materials

    CERN Document Server

    Scardi, Paolo

    2004-01-01

    Diffraction Analysis of the Microstructure of Materials provides an overview of diffraction methods applied to the analysis of the microstructure of materials. Since crystallite size and the presence of lattice defects have a decisive influence on the properties of many engineering materials, information about this microstructure is of vital importance in developing and assessing materials for practical applications. The most powerful and usually non-destructive evaluation techniques available are X-ray and neutron diffraction. The book details, among other things, diffraction-line broadening methods for determining crystallite size and atomic-scale strain due, e.g. to dislocations, and methods for the analysis of residual (macroscale) stress. The book assumes only a basic knowledge of solid-state physics and supplies readers sufficient information to apply the methods themselves.

  13. Application of laser ultrasonics to monitor microstructure evolution in Inconel 718 superalloy

    Directory of Open Access Journals (Sweden)

    Garcin Thomas

    2014-01-01

    Full Text Available Laser ultrasonics for metallurgy is an innovative sensor dedicated to the measurement of microstructure evolution during thermomechanical processing. In this technique, broadband ultrasound pulses are generated and detected with lasers. The properties of the ultrasounds are then related to the characteristics of the microstructure. Ultrasound attenuation is primary originated by the scattering at grain boundaries and its frequency dependence can be related to the grain size. The present work aims to introduce this technology as an exciting tool for metallurgists. As an illustration of its capability, the evolution of the grain size during isothermal annealing from a fine grained structure is in-situ monitored in an Inconel 718 superalloy. Laser ultrasonic measurements are compared with ex-situ metallography observations. Indication of heterogeneous grain growth is observed, correlated to the dissolution of δ-phase particles present in the initial structure. This preliminary study illustrates the potential of this new technique to monitor microstructure evolution in more complex scenarios including recrystallization during simulation of hot forging processes.

  14. High purity ultrafine-grained nickel processed by dynamic plastic deformation: microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Farbaniec, Lukasz; Dirras, Guy [Universite Paris 13, Sorbonne Paris Cite LSPM-CNRS, 99, Avenue J. B. Clement, 93430 Villetaneuse (France); Abdul-Latif, Akrum [Laboratoire d' Ingenierie des Systemes Mecaniques et des Materiaux 3, Rue Fernand Hainaut, 93407 St. Ouen Cedex (France); Gubicza, Jeno [Department of Materials Physics, Eoetvoes Lorand University Budapest, P.O. Box 32, H-1518 (Hungary)

    2012-11-15

    Bulk ultrafine-grained samples are processed by dynamic plastic deformation at an average strain rate of 3.3 x 10{sup 2} s{sup -1} from bulk coarse-grained nickel with purity higher than 98.4 wt.%. The obtained microstructure is investigated by electron backscattering diffraction, transmission electron microscopy and X-ray line profile analysis. After dynamic deformation the microstructure evolves into submicron-size lamellar and subgrain structures. Evaluation of average grain size shows a heterogeneous microstructure along both the diameter and the thickness of the sample. X-ray line profile analysis reveals high dislocation density of about 13 {+-} 2 x 10{sup 14} m{sup -2} in the impacted material. The mechanical properties are investigated by means of uniaxial quasi-static compression tests conducted at room temperature. The stress-strain behavior of the impacted Ni depends on the location in the impacted disk and on the orientation of the compression axis relative to the impact direction. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Damage modeling of small-scale experiments on dental enamel with hierarchical microstructure.

    Science.gov (United States)

    Scheider, I; Xiao, T; Yilmaz, E; Schneider, G A; Huber, N; Bargmann, S

    2015-03-01

    Dental enamel is a highly anisotropic and heterogeneous material, which exhibits an optimal reliability with respect to the various loads occurring over years. In this work, enamel's microstructure of parallel aligned rods of mineral fibers is modeled and mechanical properties are evaluated in terms of strength and toughness with the help of a multiscale modeling method. The established model is validated by comparing it with the stress-strain curves identified by microcantilever beam experiments extracted from these rods. Moreover, in order to gain further insight in the damage-tolerant behavior of enamel, the size of crystallites below which the structure becomes insensitive to flaws is studied by a microstructural finite element model. The assumption regarding the fiber strength is verified by a numerical study leading to accordance of fiber size and flaw tolerance size, and the debonding strength is estimated by optimizing the failure behavior of the microstructure on the hierarchical level above the individual fibers. Based on these well-grounded properties, the material behavior is predicted well by homogenization of a representative unit cell including damage, taking imperfections (like microcracks in the present case) into account. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  16. Microstructural effects on the springback of advanced high-strength steel

    Science.gov (United States)

    Gan, Wei; Babu, S. S.; Kapustka, Nick; Wagoner, Robert H.

    2006-11-01

    The application of advanced high-strength steels (AHSS) has been growing rapidly in the automotive industry. Because of their high-strength, thinner sheet metals can be used for body components to achieve both weight savings and increased safety. However, this will lead to greater springback deviation from design after the forming operation. Fundamental understanding and prediction of springback are required for springback compensation and tooling design. While various types of continuum mechanics based models have been proposed to simulate the mechanical behavior of advanced high-strength steels, few of them consider microstructural effects such as material heterogeneity. In this study, through sheet thickness strength variation has been observed in DP 780 and TRIP 780 steels. Finite-element simulation indicates that the through thickness effect (TTE) can have a significant impact on the springback behavior of these sheet metals. This is verified through our experimental work using draw-bend testing. The results suggest that microstructural effects should be considered to accurately simulate springback of AHSS. Based on these results, implications of different microstructural designs will be discussed.

  17. Creep behaviour and microstructural evolution in P23/P91 dissimilar welds

    Energy Technology Data Exchange (ETDEWEB)

    Vodarek, V. [Technical Univ. of Ostrava (Czech Republic); Kubon, Z.; Strilkova, L. [MATERIALS AND METALLURGICAL RESEARCH Ltd., Ostrava (Czech Republic); Hainsworth, S.V. [Leicester Univ. (United Kingdom). Dept. of Engineering

    2010-07-01

    The structural integrity of welded components operated at elevated temperatures is of key importance in power plant applications. Long-term creep exposure of dissimilar welds is accompanied by redistribution of interstitial elements which strongly affects microstructural evolution in the vicinity of the fusion zone between low and high alloy materials. This paper summarises results of studies on creep rupture properties and minor phase evolution in the P23/P71 heterogeneous welds duing creep exposure at 500, 550 and 600 C for durations exceeding 60 000 hours. The composition of filler material in Weld A corresponded to that of P91 steel, whilst for Weld B the low alloy filler material of P23 type composition was used. Results of creep rupture tests on the cross weld specimens are close to, or slightly below, the lower limit of the {+-}20% scatter band around the standardized curve for creep strength of the P23 steel. Experimental data on microstructural evolution have been compared with results of thermodynamic and kinetic simulations. The predicted minor phase evolution close to the P23/P91 interface was confirmed by microstructural investigations. Some differences between calculations and experimental studies were found for the P23 steel. It was demonstrated that undissolved fine MX particles in the partly decarburized zone of the P23 (WM23) steel significantly delayed recrystallization of the bainitic matrix. (orig.)

  18. MICROMECHANICS OF THE DAMAGE-INDUCED CELLULAR MICROSTRUCTURE IN SINGLE CRYSTAL Ni-BASED SUPERALLOYS

    Institute of Scientific and Technical Information of China (English)

    M.Sakaguchi; M.Okazaki

    2004-01-01

    An analytical method to investigate the morphological evolution of the cellular microstructure is explored and proposed. The method is essentially based on the Eshelby's micromechanics theory, and it is extended so as to be applied for a material system containing inclusions with high volume fraction, by employing the average stress field approximation by Mori and Tanaka. The proposed method enables us to discuss a stable shape of precipitate in the material system, which must be influenced by many factors: e.g., volume fraction of precipitate; Young's modulus ratio and lattice misfit between matrix and precipitate; external stress field in multiaxial state; and heterogeneity of plastic strain between matrix and precipitate. A series of numerical calculations were summarized on stable shape maps. The application of the method to predict the γ' rafting in superalloys during creep showed that the heterogeneity of plastic strain between matrix and precipitates may play a significant role in the shape stability of the precipitate. Furthermore, it was shown that the method was successfully applied to estimate the morphology of the cellular microstructure formed in CMSX-4single crystal Ni-based superalloy.

  19. Connectivity measures in EEG microstructural sleep elements

    Directory of Open Access Journals (Sweden)

    Dimitris eSakellariou

    2016-02-01

    Full Text Available During Non-Rapid Eye Movement sleep (NREM the brain is relatively disconnected from the environment, while connectedness between brain areas is also decreased. Evidence indicates that these dynamic connectivity changes are delivered by microstructural elements of sleep: short periods of environmental stimuli evaluation followed by sleep promoting procedures. The connectivity patterns of the latter, among other aspects of sleep microstructure, are still to be fully elucidated.We suggest here a methodology for the assessment and investigation of the connectivity patterns of EEG microstructural elements, such as sleep spindles. The methodology combines techniques in the preprocessing, estimation, error assessing and visualization of results levels in order to allow the detailed examination of the connectivity aspects (levels and directionality of information flow over frequency and time with notable resolution, while dealing with the volume conduction and EEG reference assessment. The high temporal and frequency resolution of the methodology will allow the association between the microelements and the dynamically forming networks that characterise them, and consequently possibly reveal aspects of the EEG microstructure. The proposed methodology is initially tested on artificially generated signals for proof of concept and subsequently applied to real EEG recordings via a custom built MATLAB-based tool developed for such studies. Preliminary results from 843 fast sleep spindles recorded in whole night sleep of 5 healthy volunteers indicate a prevailing pattern of interactions between centroparietal and frontal regions.We demonstrate hereby an opening to our knowledge attempt to estimate the scalp EEG connectivity that characterizes fast sleep spindles via an EEG-element connectivity methodology we propose. The application of the latter, via a computational tool we developed suggests it is able to investigate the connectivity patterns related to the

  20. Harvesting Information from Heterogeneous Sources

    DEFF Research Database (Denmark)

    2011-01-01

    The abundance of information regarding any topic makes the Internet a very good resource. Even though searching the Internet is very easy, what remains difficult is to automate the process of information extraction from the available online information due to the lack of structure and the diversity...... in the sharing methods. Most of the times, information is stored in different proprietary formats, complying with different standards and protocols which makes tasks like data mining and information harvesting very difficult. In this paper, an information harvesting tool (heteroHarvest) is presented...... with objectives to address these problems by filtering the useful information and then normalizing the information in a singular non hypertext format. We also discuss state of the art tools along with the shortcomings and present the results of an analysis carried out over different heterogeneous formats along...

  1. Emerging heterogeneities in Italian customs

    CERN Document Server

    Agliari, Elena; Galluzzi, Andrea; Javarone, Marco Alberto; Pizzoferrato, Andrea; Tantari, Daniele

    2015-01-01

    Since its unification, more than a century ago, Italy has experienced strong social and economical diversities between its southern and northern regions. In the last decades, Italy has undergone a severe economical and political crisis reflecting corruption at various levels of social stratification as well as a poor involvement of its population in the number of elections that occurred. This might be explained by a lack of confidence, or interest in the country as a whole, as if the primary social and political focus of its citizens could still lay at smaller regional scales, possibly evidencing the persistence of different cultural heritages. In order to shed lights on the possible existence of such heterogeneities, we perform a statistical-mechanics-driven analysis focusing on key social quantifiers, namely the evolution of autochthonous marriages (as family still plays as a fundamental brick in the edification of social aggregates) and of mixed marriages, namely those involving a foreign-born and a native...

  2. Heterogeneous Reburning By Mixed Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Anderson Hall

    2009-03-31

    Recent studies of heterogeneous reburning, i.e., reburning involving a coal-derived char, have elucidated its variables, kinetics and mechanisms that are valuable to the development of a highly efficient reburning process. Young lignite chars contain catalysts that not only reduce NO, but they also reduce HCN that is an important intermediate that recycles to NO in the burnout zone. Gaseous CO scavenges the surface oxides that are formed during NO reduction, regenerating the active sites on the char surface. Based on this mechanistic information, cost-effective mixed fuels containing these multiple features has been designed and tested in a simulated reburning apparatus. Remarkably high reduction of NO and HCN has been observed and it is anticipated that mixed fuel will remove 85% of NO in a three-stage reburning process.

  3. HETEROGENEOUS REBURNING BY MIXED FUELS

    Energy Technology Data Exchange (ETDEWEB)

    Wei-Yin Chen; Benson B. Gathitu

    2005-01-14

    Recent studies of heterogeneous reburning, i.e., reburning involving a coal-derived char, have elucidated its variables, kinetics and mechanisms that are valuable to the development of a highly efficient reburning process. Young lignite chars contain catalysts that not only reduce NO, but they also reduce HCN that is an important intermediate that recycles to NO in the burnout zone. Gaseous CO scavenges the surface oxides that are formed during NO reduction, regenerating the active sites on the char surface. Based on this mechanistic information, cost-effective mixed fuels containing these multiple features has been designed and tested in a simulated reburning apparatus. Remarkably high reduction of NO and HCN has been observed and it is anticipated that mixed fuel will remove 85% of NO in a three-stage reburning process.

  4. Heterogeneous fuel for hybrid rocket

    Science.gov (United States)

    Stickler, David B. (Inventor)

    1996-01-01

    Heterogeneous fuel compositions suitable for use in hybrid rocket engines and solid-fuel ramjet engines, The compositions include mixtures of a continuous phase, which forms a solid matrix, and a dispersed phase permanently distributed therein. The dispersed phase or the matrix vaporizes (or melts) and disperses into the gas flow much more rapidly than the other, creating depressions, voids and bumps within and on the surface of the remaining bulk material that continuously roughen its surface, This effect substantially enhances heat transfer from the combusting gas flow to the fuel surface, producing a correspondingly high burning rate, The dispersed phase may include solid particles, entrained liquid droplets, or gas-phase voids having dimensions roughly similar to the displacement scale height of the gas-flow boundary layer generated during combustion.

  5. Mesoscale poroelasticity of heterogeneous media

    Science.gov (United States)

    Monfared, Siavash; Laubie, Hadrien; Radjai, Farhang; Pellenq, Roland; Ulm, Franz-Josef

    Poroelastic behavior of heterogeneous media is revisited. Lattice Element Method (LEM) is used to model interaction between solid constituents due to a pressurized pore space. Exploring beyond mean-field based theories in continuum microporomechanics, local textural variations and its contribution to the global anisotropic poroelastic behavior of real multiphase porous media are captured. To this end, statistical distributions of mesoscale poroelastic coefficients from numerical simulations on X-ray microscopy scans of two different organic-rich shales with different microtextures are presented. The results are compared with predictions using mean-field based tools of continuum micromechanics. The textural dependency of strain localization and stress chain formation captured in this framework promises a powerful tool for modeling poroelastic response of complex porous composites and a path to incorporate local textural and elastic variations into a continuum description. Visiting Scientist, CNRS-MIT, MIT.

  6. Genetic heterogeneity of hepatocellular carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Unsal, H.; Isselbacher, K.J. (Massachusetts General Hospital Cancer Center, Charlestown, MA (United States)); Yakicier, C.; Marcais, C.; Ozturk, M. (Institut National de la Sante et de la Recherche Medicale, Lyon (France)); Kew, M. (Univ. of Witwatersrand, Johannesburg (South Africa)); Volkmann, M. (Univ. of Heidelberg (Germany)); Zentgraf, H. (Deutsches Krebsforschungszentrum, Heidelberg (Germany))

    1994-01-18

    The authors studied 80 hepatocellular carcinomas from three continents for p53 gene (TP53) mutations and hepatitis B virus (HBV) sequences. p53 mutations were frequent in tumors from Mozambique but not in tumors from South Africa, China, and Germany. Independent of geographic origin, most tumors were positive for HBV sequences. X gene coding sequences of HBV were detected in 78% of tumors, whereas viral sequences in the surface antigen- and core antigen-encoding regions were present in less than 35% of tumors. These observations indicate that hepatocellular carcinomas are genetically heterogeneous. Mozambican-types of hepatocellular carcinomas are characterized by a high incidence of p53 mutations related to aflatoxins. In other tumors, the rarity of p53 mutations combined with the frequent presence of viral X gene coding sequences suggests a possible interference of HBV with the wild-type p53 function.

  7. Operando research in heterogeneous catalysis

    CERN Document Server

    Groot, Irene

    2017-01-01

    This book is devoted to the emerging field of techniques for visualizing atomic-scale properties of active catalysts under actual working conditions, i.e. high gas pressures and high temperatures. It explains how to understand these observations in terms of the surface structures and dynamics and their detailed interplay with the gas phase. This provides an important new link between fundamental surface physics and chemistry, and applied catalysis. The book explains the motivation and the necessity of operando studies, and positions these with respect to the more traditional low-pressure investigations on the one hand and the reality of industrial catalysis on the other. The last decade has witnessed a rapid development of new experimental and theoretical tools for operando studies of heterogeneous catalysis. The book has a strong emphasis on the new techniques and illustrates how the challenges introduced by the harsh, operando conditions are faced for each of these new tools. Therefore, one can also read th...

  8. [Heterogenous expression of antimicrobial peptides].

    Science.gov (United States)

    Song, Shanshan; Hu, Guobin; Dong, Xianzhi

    2009-12-01

    Antimicrobial peptides (AMPs), a class of short proteins with a broad spectrum of antibacterial activities, are isolated from a wide variety of animals, both vertebrates and invertebrates, and plants as well as from bacteria and fungi. They are a key component of the innate immune response in most multicellular organisms. Owing to their potent, broad-spectrum antibacterial activities and uneasy developing of drug resistance, these peptides are of great clinical significance. However, preparation of AMPs at a large scale is a severe challenge to the development of the commercial products. Undoubtedly, construction of high-level biological expression systems for the production of AMPs is the key in its clinical application process. Herein, we summarize the progress in researches on heterogenous expression of AMPs in prokaryotic expression systems and eukaryotic expression systems.

  9. Comparison of multiplicative heterogeneous variance adjustment models for genetic evaluations.

    Science.gov (United States)

    Márkus, Sz; Mäntysaari, E A; Strandén, I; Eriksson, J-Å; Lidauer, M H

    2014-06-01

    Two heterogeneous variance adjustment methods and two variance models were compared in a simulation study. The method used for heterogeneous variance adjustment in the Nordic test-day model, which is a multiplicative method based on Meuwissen (J. Dairy Sci., 79, 1996, 310), was compared with a restricted multiplicative method where the fixed effects were not scaled. Both methods were tested with two different variance models, one with a herd-year and the other with a herd-year-month random effect. The simulation study was built on two field data sets from Swedish Red dairy cattle herds. For both data sets, 200 herds with test-day observations over a 12-year period were sampled. For one data set, herds were sampled randomly, while for the other, each herd was required to have at least 10 first-calving cows per year. The simulations supported the applicability of both methods and models, but the multiplicative mixed model was more sensitive in the case of small strata sizes. Estimation of variance components for the variance models resulted in different parameter estimates, depending on the applied heterogeneous variance adjustment method and variance model combination. Our analyses showed that the assumption of a first-order autoregressive correlation structure between random-effect levels is reasonable when within-herd heterogeneity is modelled by year classes, but less appropriate for within-herd heterogeneity by month classes. Of the studied alternatives, the multiplicative method and a variance model with a random herd-year effect were found most suitable for the Nordic test-day model for dairy cattle evaluation.

  10. Engineering bioceramic microstructure for customized drug delivery

    Science.gov (United States)

    Pacheco Gomez, Hernando Jose

    One of the most efficient approaches to treat cancer and infection is to use biomaterials as a drug delivery system (DDS). The goal is for the material to provide a sustained release of therapeutic drug dose locally to target the ill tissue without affecting other organs. Silica Calcium Phosphate nano composite (SCPC) is a drug delivery platform that successfully demonstrated the ability to bind and release several therapeutics including antibiotics, anticancer drugs, and growth factors. The aim of the present work is to analyze the role of SCPC microstructure on drug binding and release kinetics. The main crystalline phases of SCPC are alpha-cristobalite (SiO2, Cris) and beta-rhenanite (NaCaPO4, Rhe); therefore, these two phases were prepared and characterized separately. Structural and compositional features of Cris, Rhe and SCPC bioceramics demonstrated a significant influence on the loading capacity and release kinetics profile of Vancomycin (Vanc) and Cisplatin (Cis). Fourier Transform Infrared (FTIR) spectroscopy analyses demonstrated that the P-O functional group in Rhe and SCPC has high affinity to the (C=O and N-H) of Vanc and (N-H and O-H) of Cis. By contrast, a weak chemical interaction between the Si-O functional group in Cris and SCPC and the two drugs was observed. Vanc loading per unit surface area increased in the order 8.00 microg Vanc/m2 for Rhe > 4.49 microg Vanc /m2 for SCPC>3.01 microg Vanc /m2 for Cris (pAnimals were treated by either systemic cisplatin injection (sCis), or with SCPC-Cis hybrid placed adjacent (ADJ) to, or within (IT), the tumor. Five days after implantation 50-55% of the total cisplatin loaded was released from the SCPC-Cis hybrids resulting in an approximately 50% decrease in tumor volume compared to sCis treatment. Severe side effects were observed in animals treated with sCis including rapid weight loss and decreased liver and kidney function, effects not observed in SCPC-Cis treated animals. Analysis of cisplatin

  11. Mechanical and Microstructural Evaluation of DMAG Welding of Structural Steel

    Directory of Open Access Journals (Sweden)

    Tolga Mert

    2015-01-01

    Full Text Available Double channel torch, which allows concentric flow of two different shielding gases, was designed and manufactured in order to pursue double channel torch gas metal arc welding of unalloyed structural steel S235JR (EN 10025-2 with fourteen passes. Tensile and Charpy V-notch tests were realized and the results were compared with those of conventional gas metal arc welding. In order to evaluate mechanical testing results, microstructural analyses were conducted. It was found that the increase with double channel gas metal arc welding process in yield and tensile strengths as well as in toughness tests, especially in subzero temperatures, compared with conventional gas metal arc welding was due to longer columnar grains and finer tempered zone grain structure between passes and due to solidification and less dendritic structure formation in all-weld metal in double channel gas metal arc welding.

  12. Patterns of flower microstructural variation within the genus Bromus

    Directory of Open Access Journals (Sweden)

    Romuald Kosina

    2014-01-01

    Full Text Available Twenty five species from four sections of the genus Bromus were evaluated by means of numerical analyses of characters of flower microstructures (lodicule, lemma, palea. Special development of lodicules (lobe and hairiness and both glumellae (lemma and palea similar in grasses evolutionarily close (Bromeae, Brachypodieae, Triticeae was discovered. For most of the characters the original interspecific and intersectional relations were observed in a space of minimum spanning tree (MST. The evolutionary old section Pnigma occupies the largest space. Species of Pnigma having small chromosomes can be distinguished from those having large ones. The section Ceratochloa is scattered through the smallest space. The above points to the endemic evolution of high polyploids of the section. The sections Bromus and Genea are evolutionarily close and they distinctly overlap each other in the MST space. Bromus sterilis, B. catharticus and B. riparius are extremes in their own sections.

  13. Microstructure of MCMgAl12Zn1 magnesium alloy

    Directory of Open Access Journals (Sweden)

    Dobrzański L. A.

    2007-01-01

    Full Text Available In this paper is presented the structure of the cast magnesium alloys as cast state and after heat treatment cooled with different cooling rate, depending on the cooling medium (furnace, water, air. For investigations samples in shape of 250x150x25 mm plates were used. The structure have been study in the light microscope, scanning electron microscope equipped with an electron back scattering facility. The effects of the addition of Al on the microstructure were also studied. In the analysed alloys a structure of α solid solution and fragile phase β(Mg17Al12 occurred mainly on grain borders as well as eutectic and phase with Mn, Fe and Si. Investigation are carried out for the reason of chemical composition influence and precipitation processes influence to the structure and mechanical properties of the magnesium cast alloys with different chemical composition in as cast alloys and after heat treatment.

  14. Nature of microstructure in pulsar radio emission

    CERN Document Server

    Machabeli, G Z; Melikidze, G I; Shapakidze, D; Machabeli, George; Khechinashvili, David; Melikidze, George; Shapakidze, David

    2000-01-01

    We present a model for microstructure in pulsar radio emission. We propose that micropulses result from the alteration of the radio wave generation region by nearly transverse drift waves propagating across the pulsar magnetic field and encircling the bundle of the open magnetic field lines. It is demonstrated that such waves can modify significantly curvature of these dipolar field lines. This in turn affects strongly fulfillment of the resonance conditions necessary for the excitation of radio waves. The time-scale of micropulses is therefore determined by the wavelength of drift waves. Main features of the microstructure are naturally explained in the frame of this model.

  15. Biomimetic microstructures for photonic and fluidic synergies

    Science.gov (United States)

    Vasileiou, Maria; Mpatzaka, Theodora; Alexandropoulos, Dimitris; Vainos, Nikolaos A.

    2017-08-01

    Nature-inspired micro- and nano-structures offer a unique platform for the development of novel synergetic systems combining photonic and microfluidic functionalities. In this context, we examine the paradigm of butterfly Vanessa cardui and develop artificial diffractive microstructures inspired by its natural designs. Softlithographic and nanoimprint protocols are developed to replicate surfaces of natural specimens. Further to their optical behavior, interphases tailored by such microstructures exhibit enhanced hydrophobic properties, as compared to their planar counterparts made of the same materials. Such synergies exploited by new design approaches pave the way to prospective optofluidic, lab-on-chip and sensing applications.

  16. Biomimetic microstructures for photonic and fluidic synergies

    Directory of Open Access Journals (Sweden)

    Vasileiou Maria

    2017-08-01

    Full Text Available Nature-inspired micro- and nano-structures offer a unique platform for the development of novel synergetic systems combining photonic and microfluidic functionalities. In this context, we examine the paradigm of butterfly Vanessa cardui and develop artificial diffractive microstructures inspired by its natural designs. Softlithographic and nanoimprint protocols are developed to replicate surfaces of natural specimens. Further to their optical behavior, interphases tailored by such microstructures exhibit enhanced hydrophobic properties, as compared to their planar counterparts made of the same materials. Such synergies exploited by new design approaches pave the way to prospective optofluidic, lab-on-chip and sensing applications.

  17. Towards biochips using microstructured optical fiber sensors

    DEFF Research Database (Denmark)

    Rindorf, Lars Henning; Hoiby, Poul Erik; Jensen, Jesper Bo

    2006-01-01

    In this paper we present the first incorporation of a microstructured optical fiber (MOF) into biochip applications. A 16-mm-long piece of MOF is incorporated into an optic-fluidic coupler chip, which is fabricated in PMMA polymer using a CO2 laser. The developed chip configuration allows...... the continuous control of liquid flow through the MOF and simultaneous optical characterization. While integrated in the chip, the MOF is functionalized towards the capture of a specific single-stranded DNA string by immobilizing a sensing layer on the microstructured internal surfaces of the fiber. The sensing...

  18. Exploring the Microstructure of YBCO Nanopowders

    Institute of Scientific and Technical Information of China (English)

    MIAO Rui-Ping; QI Xiu-Zhen; ZHAO Yong

    2005-01-01

    High temperature superconductor YBa2Cu3O7-x (YBCO) nanopowders were successfully prepared by a citrate pyrolysis technique. The phase formation and microstructure of the nanopowders were studied. The microstructure analysis shows that the obtained YBCO powders have very fine grains with a size around several tens of nanometers. The superfine morphology reveals that the thermal agglomeration of the particles decreases with decreasing the annealing temperature and shortening the annealing time. In addition, the complete phase formation of YBCO depends upon the annealing temperature and the annealing time as well. So far, these nanopowders have been used to fabricate the melt-textured YBCO bulk materials.

  19. "Unmanned” optical micromanipulation using waveguide microstructures

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Villangca, Mark Jayson

    2013-01-01

    be shaped more arbitrarily, engineered light deflection could lead to more control in the resulting motion. We demonstrated this principle with the autonomous translation of bent waveguides though pre-defined light tracks. In our experiment, incoming light makes a near 90 degree turn, hence the resulting...... force has a behavior similar to that from the reflection of light from an angled mirror. A force with a component opposite to light’s propagation through the waveguide drives the waveguide microstructure. Another bend at the opposite of the microstructure could slow it down, offering a way...

  20. Microstructure, Slip Systems and Yield Stress Anisotropy in Plastic Deformation

    DEFF Research Database (Denmark)

    Winther, Grethe; You, Ze Sheng; Lu, Lei

    The highly anisotropic microstructures in nanotwinned copper produced by electrodeposition provide an excellent opportunity to evaluate models for microstructurally induced mechanical anisotropy. A crystal plasticity model originally developed for the integration of deformation induced dislocation...

  1. Fractographic observations of the microstructural characteristics of flax fibre composites

    DEFF Research Database (Denmark)

    Madsen, Bo; Asian, Mustafa; Lilholt, Hans

    2016-01-01

    Natural fibre composites possess a number of special microstructural characteristics, which need to be documented to aid in the further development of these materials. Using field emission scanning electron microscopy, fractographic observations of the microstructural characteristics of aligned...

  2. Intelligent Classification in Huge Heterogeneous Data Sets

    Science.gov (United States)

    2015-06-01

    INTELLIGENT CLASSIFICATION IN HUGE HETEROGENEOUS DATA SETS JUNE 2015 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED...To) JUL 2013 – APR 2015 4. TITLE AND SUBTITLE INTELLIGENT CLASSIFICATION IN HUGE HETEROGENEOUS DATA SETS 5a. CONTRACT NUMBER IN-HOUSE 5b. GRANT...signals and through data dimension reduction, and to develop and tailor algorithms for the extraction of intelligence from several huge heterogeneous

  3. In-situ characterization of heterogeneous catalysts

    CERN Document Server

    Rodriguez, Jose A; Chupas, Peter J

    2013-01-01

    Helps researchers develop new catalysts for sustainable fuel and chemical production Reviewing the latest developments in the field, this book explores the in-situ characterization of heterogeneous catalysts, enabling readers to take full advantage of the sophisticated techniques used to study heterogeneous catalysts and reaction mechanisms. In using these techniques, readers can learn to improve the selectivity and the performance of catalysts and how to prepare catalysts as efficiently as possible, with minimum waste. In-situ Characterization of Heterogeneous Catalysts feat

  4. Demographic heterogeneity, cohort selection, and population growth

    OpenAIRE

    Bruce E. Kendall; Fox, Gordon A.; Fujiwara, Masami; Nogeire, Theresa M.

    2011-01-01

    Demographic heterogeneity—variation among individuals in survival and reproduction—is ubiquitous in natural populations. Structured population models address heterogeneity due to age, size, or major developmental stages. However, other important sources of demographic heterogeneity, such as genetic variation, spatial heterogeneity in the environment, maternal effects, and differential exposure to stressors, are often not easily measured and hence are modeled as stochasticity. Recent research ...

  5. Microstructural Evolution of Solid-solution-treated Zn-22Al in the Semisolid State

    Institute of Scientific and Technical Information of China (English)

    M.A.M.Arif; M.Z.Omar; N.Muhamad; J.Syarif; P.Kapranos

    2013-01-01

    The effect of solid-solution-treatment on the semisolid microstructure of Zn-22Al with developed dendrites was investigated.Forming Zn-22Al products by semisolid metal processing offers significant advantages,such as reductions in macro-segregation,porosity and forming costs.Thermal and microstructural analyses of the formed Zn-22Al alloy were performed by differential scanning calorimetry,scanning electron microscopy and optical microscopy.The changes in the microstructures and phase transformation in response to various solidsolution-treatments were analysed.In this study,as-cast samples were held isothermally at 330 ℃ for 0.5-5 h and then partially remelted at a semisolid temperature of 438 ℃ for 1 h to produce a solid-globular grain structure in a liquid matrix.A non-dendritic semisolid microstructure could not be obtained when the traditionally cast Zn-22Al alloy with developed dendrites was subjected directly to partial remelting.After solid-solution-treatment at 330 ℃,the black interdendritic eutectics were dissolved,and the dendritic structures gradually transformed into uniform β structures when the treatment time was increased.The coarsened and merged dendrites were separated as a result of penetration by the liquid phase and melting of the residual eutectic at sites along the former grain boundaries.The microstructure of the solid-solutiontreated sample transformed into a small globular structure; the best shape factor of 0.9,corresponding to a particle size of 40 ± 16 μm,is achieved when the sample was treated for 3 h followed by direct partial remelting into its semisolid zone.

  6. Eff ect of homogenization on the properties and microstructure of Mozzarella cheese from buff alo milk

    Directory of Open Access Journals (Sweden)

    S. Abd El-Rafee

    2012-06-01

    Full Text Available Background. The name pasta fi lata refers to a unique plasticizing and texturing treatments of the fresh curd in hot water that imparts to the fi nished cheese its characteristic fi brous structure and melting properties. Mozzarella cheese made from standardized homogenized and non-homogenized buffalo milk with 3 and 1.5%fat. The effect of homogenization on rheological, microstructure and sensory evaluation was carried out. Material and methods. Fresh raw buffalo milk and starter cultures of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus were used. The coagulants were calf rennet powder (HA-LA. Standardized buffalo milk was homogenized at 25 kg/cm2 pressure after heating to 60°C using homogenizer. Milk and cheese were analysed. Microstructure of the cheese samples was investigated either with an application of transmission or scanning electron microscope. Statistical analyses were applied on the obtained data. Results. Soluble nitrogen total volatile free fatty acids, soluble tyrosine and tryptophan increased with using homogenized milk and also, increased with relatively decrease in case of homogenized Mozzarella cheese. Meltability of Mozzarella cheese increased with increasing the fat content and storage period and decrease with homogenization. Mozzarella cheese fi rmness increased with homogenization and also, increased with progressing of storage period. Flavour score, appearance and total score of Mozzarella cheese increased with homogenization and storage period progress, while body and texture score decreased with homogenization and increased with storage period progress. Microstructure of Mozzarella cheese showed the low fat cheese tends to be harder, more crumbly and less smooth than normal. Curd granule junctions were prominent in non-homogenized milk cheese. Conclusion. Homogenization of milk cheese caused changes in the microstructure of the Mozzarella cheese. Microstructure studies of cheese revealed that

  7. Nonlinear ionic transport through microstructured solid electrolytes: homogenization estimates

    Science.gov (United States)

    Curto Sillamoni, Ignacio J.; Idiart, Martín I.

    2016-10-01

    We consider the transport of multiple ionic species by diffusion and migration through microstructured solid electrolytes in the presence of strong electric fields. The assumed constitutive relations for the constituent phases follow from convex energy and dissipation potentials which guarantee thermodynamic consistency. The effective response is heuristically deduced from a multi-scale convergence analysis of the relevant field equations. The resulting homogenized response involves an effective dissipation potential per species. Each potential is mathematically akin to that of a standard nonlinear heterogeneous conductor. A ‘linear-comparison’ homogenization technique is then used to generate estimates for these nonlinear potentials in terms of available estimates for corresponding linear conductors. By way of example, use is made of the Maxwell-Garnett and effective-medium linear approximations to generate estimates for two-phase systems with power-law dissipation. Explicit formulas are given for some limiting cases. In the case of threshold-type behavior, the estimates exhibit non-analytical dilute limits and seem to be consistent with fields localized in low energy paths.

  8. Heterogeneous precipitation of niobium carbide in the ferrite by Monte Carlo simulations; Cinetique de precipitation heterogene du carbure de niobium dans la ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Hin, C

    2005-12-15

    The precipitation of niobium carbides in industrial steels is commonly used to control the recrystallization process or the amount of interstitial atoms in solid solution. It is then important to understand the precipitation kinetics and especially the competition between homogeneous and heterogeneous precipitation, since both of them have been observed experimentally, depending on they alloy composition, microstructure and thermal treatments. We propose Monte Carlo simulations of NbC precipitation in {open_square}-iron, based on a simple atomic description of the main parameters which control the kinetic pathway: - Realistic diffusion properties, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps; - A model of grain boundaries which reproduces the segregation properties of Nb and C; - A model of dislocation which interacts with solute atoms through local segregation energies and long range elastic field; - A point defect source which drives the vacancy concentration towards its equilibrium value. Depending on the precipitation conditions, Monte Carlo simulations predict different kinetic behaviors, including a transient precipitation of metastable carbides, an early segregation stage of C, wetting phenomena at grain boundaries and on dislocations and a competition between homogeneous and heterogeneous NbC precipitation. Concerning the last point, we highlight that long range elastic field due to dislocation favors clearly the heterogeneous precipitation on dislocations. To understand this effect, we have developed a heterogeneous nucleation model including the calculation of the local concentration of solute atoms around the dislocation, the change of the solubility limit relative to the solubility limit in bulk and the energy of precipitates in an elastic field. We have concluded that elastic field favors the heterogeneous precipitation through the fall in nucleation barrier. (author)

  9. Fixed export cost heterogeneity, trade and welfare

    DEFF Research Database (Denmark)

    Jørgensen, Jan Guldager; Schröder, Philipp J.H.

    2008-01-01

    -country intra-industry trade model where firms are of two different marginal costs types and where fixed export costs are heterogeneous across firms. This model traces many of the stylized facts of international trade. However, we find that with heterogeneous fixed export costs there exists a positive bilateral......Recent literature on the workhorse model of intra-industry trade has explored heterogeneous cost structures at the firm level. These approaches have proven to add realism and predictive power. This paper presents a new and simple heterogeneous-firms specification. We develop a symmetric two...

  10. Microstructure Evolution in Nano-reinforced Ferritic Steel Processed By Mechanical Alloying and Spark Plasma Sintering

    Science.gov (United States)

    Boulnat, Xavier; Perez, Michel; Fabregue, Damien; Douillard, Thierry; Mathon, Marie-Hélène; de Carlan, Yann

    2013-11-01

    Oxide-dispersion strengthened ferritic steel was produced by high-energy attrition, leading to a complex nanostructure with deformed ferritic grains. After mechanical alloying, the powder was then consolidated by spark plasma sintering (SPS) using various thermo-mechanical treatments. Hot isostatic pressing (HIP) was also performed on the same powder for comparison. Above 1123 K (850 °C), SPS consolidation-induced heterogeneous microstructure composed of ultra-fine-grained regions surrounded by larger grains. Spatial distribution of the stored energy was measured in the bimodal microstructure using the Kernel average misorientation. In contrary to large recrystallized grains, ultra-fine grains are still substructured with low-angle grain boundaries. The precipitation kinetics of the nano-oxides during consolidation was determined by small-angle neutron scattering. Precipitation mainly occurred during the heating stage, leading to a high density of nanoclusters that are of prime importance for the mechanical properties. Other coarser titanium-enriched oxides were also detected. The multiscale characterization allowed us to understand and model the evolution of the complex microstructure. An analytical evaluation of the contributing mechanisms explains the appearance of the complex grain structure and its thermal stability during further heat treatments. Inhomogeneous distribution of plastic deformation in the powder is the major cause of heterogeneous recrystallization and further grain growth during hot consolidation. Then, the thermal stability of coherent nano-oxides is responsible for effective grain boundary pinning in recovered regions where the driving pressure for recrystallization is lowered. This scenario is confirmed in both SPSed and HIPed materials.

  11. Effect of interaction heterogeneity on colloidal arrangements at a curved oil-water interface.

    Science.gov (United States)

    Lee, Mina; Lee, Daeyeon; Park, Bum Jun

    2015-01-14

    We report the unique arrangement behaviour of colloidal particles at a curved oil-water interface. Particles trapped at a centrosymmetrically curved oil-water interface, formed by placing an oil lens at a neat air-water interface, organize into diverse arrangement structures due to electrostatic repulsion under the gravitational field. To reveal a possible mechanism behind the observed diversity, we investigate the interactions between pairs of particles at the curved oil-water interface. The magnitude of electrostatic repulsive interactions between pairs of particles is determined by minimizing the total potential of the particle pairs. We show that the pair interactions are quite heterogeneous, following a Gamma distribution. Using the experimentally determined pair potential and the heterogeneity in the potential as input parameters for Monte Carlo simulations, we show that such interaction heterogeneity affects the particle arrangements at the curved interface and results in an observed diversity in the particle arrangement structures. We believe that this work prompts further experimental and simulation studies to extensively understand hierarchical relations from small scale measurements (e.g., pair interactions and heterogeneity) to bulk scale properties (e.g., microstructure and interfacial rheology).

  12. Multiscale Characterization of Structural Compositional and Textural Heterogeneity of Nano-porous Geomaterials.

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hongkyu

    2017-09-01

    The purpose of the project was to perform m ultiscale characterization of low permeability rocks to determine the effect of physical and chemical heterogeneity on the poromechanical and flow responses of shales and carbonate rocks with a broad range of physical and chemical heterogeneity . An integrated multiscale imaging of shale and carbonate rocks from nanometer to centimeter scales include s dual focused ion beam - scanning electron microscopy (FIB - SEM) , micro computed tomography (micro - CT) , optical and confocal microscopy, and 2D and 3D energ y dispersive spectroscopy (EDS). In addition, mineralogical mapping and backscattered imaging with nanoindentation testing advanced the quantitative evaluat ion of the relationship between material heterogeneity and mechanical behavior. T he spatial distribu tion of compositional heterogeneity, anisotropic bedding patterns, and mechanical anisotropy were employed as inputs for brittle fracture simulations using a phase field model . Comparison of experimental and numerical simulations reveal ed that proper inco rporation of additional material information, such as bedding layer thickness and other geometrical attributes of the microstructures, can yield improvements on the numerical prediction of the mesoscale fracture patterns and hence the macroscopic effective toughness. Overall, a comprehensive framework to evaluate the relationship between mechanical response and micro - lithofacial features can allow us to make more accurate prediction of reservoir performance by developing a multi - scale understanding of porom echanical response to coupled chemical and mechanical interactions for subsurface energy related activities .

  13. Design of microstructured waveguide devices for applications in optical sensing

    DEFF Research Database (Denmark)

    Town, G.E.; McCosker, R.; Yuan, Scott Wu;

    2010-01-01

    Microstructured waveguides provide a versatile platform for controlling interactions between light and their environment. We show how microstructured waveguides may be designed to improve the performance of optical sensors, and discuss their practical implementation.......Microstructured waveguides provide a versatile platform for controlling interactions between light and their environment. We show how microstructured waveguides may be designed to improve the performance of optical sensors, and discuss their practical implementation....

  14. Femtosecond Laser Microstructuring and Chalcogen Inclusion in Silicon

    Science.gov (United States)

    2011-02-12

    Conversation with Researchers and Students at the Benem¿rita Universidad Aut¿noma de Puebla in Puebla , Puebla , Mexico on 29 May 2009 Black silicon...Society Published on Web 04/19/2006 Following laser irradiation, the microstructured silicon surfaces were treated for 60 s in air plasma. Immediately...microstructure height and the distance between microstructures. After laser microstructuring, the sample surface is treated in air plasma to clean the

  15. Probing region-specific microstructure of human cortical areas using high angular and spatial resolution diffusion MRI.

    Science.gov (United States)

    Aggarwal, Manisha; Nauen, David W; Troncoso, Juan C; Mori, Susumu

    2015-01-15

    Regional heterogeneity in cortical cyto- and myeloarchitecture forms the structural basis of mapping of cortical areas in the human brain. In this study, we investigate the potential of diffusion MRI to probe the microstructure of cortical gray matter and its region-specific heterogeneity across cortical areas in the fixed human brain. High angular resolution diffusion imaging (HARDI) data at an isotropic resolution of 92-μm and 30 diffusion-encoding directions were acquired using a 3D diffusion-weighted gradient-and-spin-echo sequence, from prefrontal (Brodmann area 9), primary motor (area 4), primary somatosensory (area 3b), and primary visual (area 17) cortical specimens (n=3 each) from three human subjects. Further, the diffusion MR findings in these cortical areas were compared with histological silver impregnation of the same specimens, in order to investigate the underlying architectonic features that constitute the microstructural basis of diffusion-driven contrasts in cortical gray matter. Our data reveal distinct and region-specific diffusion MR contrasts across the studied areas, allowing delineation of intracortical bands of tangential fibers in specific layers-layer I, layer VI, and the inner and outer bands of Baillarger. The findings of this work demonstrate unique sensitivity of diffusion MRI to differentiate region-specific cortical microstructure in the human brain, and will be useful for myeloarchitectonic mapping of cortical areas as well as to achieve an understanding of the basis of diffusion NMR contrasts in cortical gray matter. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Microstructural evolution of a CoCrFeMnNi high-entropy alloy after swaging and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Laplanche, G., E-mail: guillaume.laplanche@rub.de; Horst, O.; Otto, F.; Eggeler, G.; George, E.P.

    2015-10-25

    The processing parameters which govern the evolution of microstructure and texture during rotary swaging and subsequent heat treatments were studied in an equiatomic single-phase CoCrFeMnNi high-entropy alloy. After vacuum induction melting and casting, the diameter of the 40 mm cast ingot was reduced at room temperature to a final diameter of 16.5 mm by rotary swaging (diameter reduction of 60%/area reduction of 80%) and the alloy was then annealed at different temperatures for 1 h. The resulting microstructures were analyzed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscatter diffraction and correlated with results of microhardness measurements. It was found that the microhardness first increases slightly upon annealing below the recrystallization temperature but then drops steeply at higher annealing temperatures due to the onset of recrystallization. Special emphasis was placed on how the microstructure evolves with respect to the radial and longitudinal position in the rod. Finally, a combination of swaging and heat treatment parameters were identified that can produce CoCrFeMnNi high-entropy alloys with a homogeneous composition and grain size and almost no texture. - Highlights: • Evolution of microstructure and texture in CoCrFeMnNi after swaging and annealing. • Rotary swaging results in major <111> + minor <100>-fiber textures. • Recrystallization (RX) in the deformed microstructure is heterogeneous. • Complete RX resulted in homogenous grain size distributions with no texture. • The low SFE is likely the reason for the homogeneous microstructure after.

  17. Episodic memory in detoxified alcoholics: contribution of grey matter microstructure alteration.

    Directory of Open Access Journals (Sweden)

    Sandra Chanraud

    Full Text Available Even though uncomplicated alcoholics may likely have episodic memory deficits, discrepancies exist regarding to the integrity of brain regions that underlie this function in healthy subjects. Possible relationships between episodic memory and 1 brain microstructure assessed by magnetic resonance diffusion tensor imaging (DTI, 2 brain volumes assessed by voxel-based morphometry (VBM were investigated in uncomplicated, detoxified alcoholics.Diffusion and morphometric analyses were performed in 24 alcohol dependent men without neurological or somatic complications and in 24 healthy men. The mean apparent coefficient of diffusion (ADC and grey matter volumes were measured in the whole brain. Episodic memory performance was assessed using a French version of the Free and Cued Selective Reminding Test (FCSRT. Correlation analyses between verbal episodic memory, brain microstructure, and brain volumes were carried out using SPM2 software.In those with alcohol dependence, higher ADC was detected mainly in frontal, temporal and parahippocampal regions, and in the cerebellum. In alcoholics, regions with higher ADC typically also had lower grey matter volume. Low verbal episodic memory performance in alcoholism was associated with higher mean ADC in parahippocampal areas, in frontal cortex and in the left temporal cortex; no correlation was found between regional volumes and episodic memory scores. Regression analyses for the control group were not significant.These findings support the hypothesis that regional microstructural but no macrostructural alteration of the brain might be responsible, at least in part, for episodic memory deficits in alcohol dependence.

  18. The development of corpus callosum microstructure and associations with bimanual task performance in healthy adolescents.

    Science.gov (United States)

    Muetzel, Ryan L; Collins, Paul F; Mueller, Bryon A; M Schissel, Ann; Lim, Kelvin O; Luciana, Monica

    2008-02-15

    Cross-sectional and longitudinal volumetric studies suggest that the corpus callosum (CC) continues to mature structurally from infancy to adulthood. Diffusion tensor imaging (DTI) provides in vivo information about the directional organization of white matter microstructure and shows potential for elucidating even more subtle brain changes during adolescent development. We used DTI to examine CC microstructure in healthy right-handed adolescents (n=92, ages 9-24 years) and correlated the imaging data with motor task performance. The primary DTI variable was fractional anisotropy (FA), which reflects the degree of white matter's directional organization. Participants completed an alternating finger tapping test to assess interhemispheric transfer and motor speed. Task performance was significantly correlated with age. Analyses of variance indicated that 9- to 11-year-olds generally performed worse than each of the older groups. Males outperformed females. Significant positive correlations between age and FA were observed in the splenium of the CC, which interconnects posterior cortical regions. Analyses of variance indicated that individuals older than 18 years had significantly higher FA than 9- to 11-year-olds. FA levels in the genu and splenium correlated significantly with task performance. Regression analyses indicated that bimanual coordination was significantly predicted by age, gender, and splenium FA. Decreases in alternating finger tapping time and increases in FA likely reflect increased myelination in the CC and more efficient neuronal signal transmission. These findings expand upon existing neuroimaging reports of CC development by showing associations between bimanual coordination and white matter microstructural organization in an adolescent sample.

  19. Multivariate characterization of white matter heterogeneity in autism spectrum disorder.

    Science.gov (United States)

    Dean, D C; Lange, N; Travers, B G; Prigge, M B; Matsunami, N; Kellett, K A; Freeman, A; Kane, K L; Adluru, N; Tromp, D P M; Destiche, D J; Samsin, D; Zielinski, B A; Fletcher, P T; Anderson, J S; Froehlich, A L; Leppert, M F; Bigler, E D; Lainhart, J E; Alexander, A L

    2017-01-01

    The complexity and heterogeneity of neuroimaging findings in individuals with autism spectrum disorder has suggested that many of the underlying alterations are subtle and involve many brain regions and networks. The ability to account for multivariate brain features and identify neuroimaging measures that can be used to characterize individual variation have thus become increasingly important for interpreting and understanding the neurobiological mechanisms of autism. In the present study, we utilize the Mahalanobis distance, a multidimensional counterpart of the Euclidean distance, as an informative index to characterize individual brain variation and deviation in autism. Longitudinal diffusion tensor imaging data from 149 participants (92 diagnosed with autism spectrum disorder and 57 typically developing controls) between 3.1 and 36.83 years of age were acquired over a roughly 10-year period and used to construct the Mahalanobis distance from regional measures of white matter microstructure. Mahalanobis distances were significantly greater and more variable in the autistic individuals as compared to control participants, demonstrating increased atypicalities and variation in the group of individuals diagnosed with autism spectrum disorder. Distributions of multivariate measures were also found to provide greater discrimination and more sensitive delineation between autistic and typically developing individuals than conventional univariate measures, while also being significantly associated with observed traits of the autism group. These results help substantiate autism as a truly heterogeneous neurodevelopmental disorder, while also suggesting that collectively considering neuroimaging measures from multiple brain regions provides improved insight into the diversity of brain measures in autism that is not observed when considering the same regions separately. Distinguishing multidimensional brain relationships may thus be informative for identifying

  20. Lattice Boltzmann formulation for conjugate heat transfer in heterogeneous media.

    Science.gov (United States)

    Karani, Hamid; Huber, Christian

    2015-02-01

    In this paper, we propose an approach for studying conjugate heat transfer using the lattice Boltzmann method (LBM). The approach is based on reformulating the lattice Boltzmann equation for solving the conservative form of the energy equation. This leads to the appearance of a source term, which introduces the jump conditions at the interface between two phases or components with different thermal properties. The proposed source term formulation conserves conductive and advective heat flux simultaneously, which makes it suitable for modeling conjugate heat transfer in general multiphase or multicomponent systems. The simple implementation of the source term approach avoids any correction of distribution functions neighboring the interface and provides an algorithm that is independent from the topology of the interface. Moreover, our approach is independent of the choice of lattice discretization and can be easily applied to different advection-diffusion LBM solvers. The model is tested against several benchmark problems including steady-state convection-diffusion within two fluid layers with parallel and normal interfaces with respect to the flow direction, unsteady conduction in a three-layer stratified domain, and steady conduction in a two-layer annulus. The LBM results are in excellent agreement with analytical solution. Error analysis shows that our model is first-order accurate in space, but an extension to a second-order scheme is straightforward. We apply our LBM model to heat transfer in a two-component heterogeneous medium with a random microstructure. This example highlights that the method we propose is independent of the topology of interfaces between the different phases and, as such, is ideally suited for complex natural heterogeneous media. We further validate the present LBM formulation with a study of natural convection in a porous enclosure. The results confirm the reliability of the model in simulating complex coupled fluid and thermal dynamics

  1. Deformation of the lithosphere and what microstructures can tell us about it (Stephan Mueller Medal Lecture)

    Science.gov (United States)

    Heilbronner, Renée

    2016-04-01

    The lithosphere is a roughly stratified and heterogeneous rock body that constitutes the outer layer of our planet. It is subdivided into irregularly shaped stiff plates that move with respect to one another deforming each other along their margins. At the large scale the lithosphere is usually modeled as a flat-lying multi-layer, its rheological profile being based on flow laws determined experimentally for key minerals of the crust and upper mantle. At the somewhat smaller scale of field observations, geometrical and physical complexities become apparent: rocks are folded, sheared and fractured, and - in general - quite heterogeneously deformed. And finally, at the even smaller scale of mechanical testing and microscopic investigations, rocks are seen as polycrystalline aggregates or granular composites whose bulk properties depends both on the composition and shape of the individual grains and the spatial arrangement of the crystals with respect to one another. In other words, the physical properties of the lithosphere and the inferred style or type of deformation depend very much on the scale of observation. Microstructures and textures (crystallographic preferred orientations) of deformed rocks provide a wealth of information: when used as archives of the deformation history, they allow us to unravel the tectonic evolution of the lithosphere at plate boundaries. At the same time, they enable us to assess past and/or present geophysical properties. By comparing the microstructures of experimentally and naturally deformed rocks it is possible to infer the active deformation mechanisms and thus to extrapolate flow laws to geological time scales. With the advent of digital image processing, microstructure and texture analysis have taken a great leap forward. By amalgamating methods from neighbouring disciplines such as mathematical morphometry, stereology, geostatistics, material sciences, etc., microstructure and texture analysis have come a long way since the

  2. Potentiostat for Characterizing Microstructures at Ionic Liquid/Electrode Interfaces

    Science.gov (United States)

    2015-10-10

    Characterizing Microstructures at Ionic Liquid /Electrode Interfaces Report Title This report details the procurement and integration of a multichannel...Haverhals, “Microstructure at the Ionic Liquid /Electrode Interface ”, 226th ECS Meeting, 8 October, 2014, Cancun, Mexico. (c) Presentations Received Paper...Technology Transfer FINAL REPORT “Potentiostat for Characterizing Microstructures at Ionic Liquid /Electrode Interfaces ” Proposal #: 66259CHRI

  3. Attention-deficit/hyperactivity disorder without comorbidity is associated with distinct atypical patterns of cerebral microstructural development.

    Science.gov (United States)

    Adisetiyo, Vitria; Tabesh, Ali; Di Martino, Adriana; Falangola, Maria F; Castellanos, Francisco X; Jensen, Jens H; Helpern, Joseph A

    2014-05-01

    Differential core symptoms and treatment responses are associated with the pure versus comorbid forms of attention-deficit/hyperactivity disorder (ADHD). However, comorbidity has largely been unaccounted for in neuroimaging studies of ADHD. We used diffusional kurtosis imaging to investigate gray matter (GM) and white matter (WM) microstructure of children and adolescents with ADHD (n = 22) compared to typically developing controls (TDC, n = 27) and examined whether differing developmental patterns are related to comorbidity. The ADHD group (ADHD-mixed) consisted of subgroups with and without comorbidity (ADHD-comorbid, n = 11; ADHD-pure, n = 11, respectively). Age-related changes and group differences in cerebral microstructure of the ADHD-mixed group and each ADHD subgroup were compared to TDC. Whole-brain voxel-based analyses with mean kurtosis (MK) and mean diffusivity (MD) metrics were conducted to probe GM and WM. Tract-based spatial statistics analyses of WM were performed with MK, MD, fractional anisotropy, and directional (axial, radial) kurtosis and diffusivity metrics. ADHD-pure patients lacked significant age-related changes in GM and WM microstructure that were observed globally in TDC and had significantly greater WM microstructural complexity than TDC in bilateral frontal and parietal lobes, insula, corpus callosum, and right external and internal capsules. Including ADHD patients with diverse comorbidities in analyses masked these findings. A distinct atypical age-related trajectory and aberrant regional differences in brain microstructure were detected in ADHD without comorbidity. Our results suggest that different phenotypic manifestations of ADHD, defined by the presence or absence of comorbidity, differ in cerebral microstructural markers.

  4. Fundamental research regarding the ultrasonic stirring effects on the microstructure of A356 castings

    Science.gov (United States)

    Jia, Shian

    Ultrasonic stirring treatment (UST) of molten metal has significant effects on the solidification microstructure of A356 alloy, which includes grain structure, distribution of inclusions, refinement of secondary phases, etc. The primary causes are due to ultrasonic cavitation, acoustic streaming and propagation of ultrasound waves in media. However, the mechanism of how those effects happen are not fully understood and quantified. In this research, molten A356 alloy was treated with high power ultrasound at a frequency of 18 kHz, and then at relatively high superheat, the melt was cast into a permanent metal mold which complies with ASTM B108-02. The UST processing system was custom built to perform the present UST study. The relatively high superheat condition is similar to the one used in the standard foundry practice, which will assist in the scale up of practical application of ultrasonic stirring technology. The selected parameters for the ultrasonic stirring technology (UST) were determined by using an UST modeling software tool that was recently developed and validated. The UST modeling software tool is capable of modeling and simulating the acoustic streaming and ultrasonic cavitation as well as the microstructure evolution during the solidification of cast alloys. Since the UST was preceded in the molten alloy, no dendrites are growing during the UST processing. Besides, more energy is required for homogeneous nucleation to occur. Consequently, the dominant mechanism of nucleation in this research is heterogeneous nucleation. The microstructure and mechanical properties of the A356 alloy processed with and without UST were analyzed and compared in detail in this study. It was demonstrated that the ultrasonically-stirred A356 alloy shows superior microstructure characteristics with very low micro-porosity levels and improved tensile properties when compared with the standard A356 alloy.

  5. Microstructural Quantification and Property Prediction Using Limited X-ray Tomography Data

    Science.gov (United States)

    Li, Hechao; Singh, Somya; Shashank Kaira, C.; Mertens, James C. E.; Williams, Jason J.; Chawla, Nikhilesh; Jiao, Yang

    2016-08-01

    X-ray tomography has provided a non-destructive means for microstructure characterization in three dimensional (3D) and four dimensional (4D) (i.e., structural evolution over time), in which projections of a material's structure are typically reconstructed using the filtered-back-projection (FBP) method or algebraic reconstruction techniques. The reconstructed images are typically segmented to conduct microstructural quantification. The process can be quite time consuming and computationally intensive. In this paper, we present an overview of our recent work on utilizing a limited (Nyquist under-sampled) number of unique perspective radiographs for computed tomography reconstruction of heterogeneous material (e.g., composites and alloys) structural quantification, property prediction and microstructural reconstruction in 3D and 4D. The proposed approach is significantly more efficient and computationally less intensive than FBP. We first show that an inverse superposition of properly normalized attenuated intensity along different x-ray paths leads to a probability map for the material system, which provides the probability of finding a particular phase at a point in the imaged sample volume. Spatial correlation functions, which are statistical morphological descriptors of the material, are readily computed from the associated probability map. Using effective medium theory and the computed correlation functions, accurate predictions of physical properties (e.g., elastic moduli and thermal/electrical conductivity) can then be obtained. Finally, we present a stochastic reconstruction procedure that generates an accurate rendition of the 3D microstructure from a reduced number of tomographic projections. This stochastic reconstruction method can be easily adapted to reconstruct 4D structural evolution from a small number of in situ projections.

  6. Quantifying brain microstructure with diffusion MRI

    DEFF Research Database (Denmark)

    Novikov, Dmitry S.; Jespersen, Sune N.; Kiselev, Valerij G.

    2016-01-01

    We review, systematize and discuss models of diffusion in neuronal tissue, by putting them into an overarching physical context of coarse-graining over an increasing diffusion length scale. From this perspective, we view research on quantifying brain microstructure as occurring along the three ma...

  7. Studying Microstructure in Molecular Crystals With Nanoindentation

    DEFF Research Database (Denmark)

    Mishra, Manish Kumar; Desiraju, Gautam R; Ramamurty, Upadrasta;

    2014-01-01

    Intergrowth polymorphism refers to the existence of distinct structural domains within a single crystal of a compound. The phenomenon is exhibited by form II of the active pharmaceutical ingredient felodipine, and the associated microstructure is a significant feature of the compound's structural...

  8. Microstructured optical fiber refractive index sensor

    DEFF Research Database (Denmark)

    Town, Graham E.; McCosker, Ravi; Yuan, Scott Wu

    2010-01-01

    We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show...

  9. 3D microstructuring of biodegradable polymers

    DEFF Research Database (Denmark)

    Nagstrup, Johan; Keller, Stephan Sylvest; Almdal, Kristoffer

    2011-01-01

    Biopolymer films with a thickness of 100μm are prepared using spin coating technique with solutions consisting of 25wt.% polycaprolactone or poly-l-lactide in dichloromethane. SU-8 stamps are fabricated using three photolithography steps. The stamps are used to emboss 3D microstructures...

  10. Capturing the Complexity of Additively Manufactured Microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Livescu, Veronica [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bronkhorst, Curt Allan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vander Wiel, Scott Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mayeur, Jason Rhea [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brown, Donald William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dippo, Olivia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-12

    The underlying mechanisms and kinetics controlling damage nucleation and growth as a function of material microstructure and loading paths are discussed. These experiments indicate that structural features such as grain boundaries, grain size distribution, grain morphology crystallographic texture are all factors that influence mechanical behavior.

  11. Surface microstructure replication in injection molding

    DEFF Research Database (Denmark)

    Theilade, Uffe Arlø; Hansen, Hans Nørgaard

    2006-01-01

    In recent years, polymer components with surface microstructures have been in rising demand for applications such as lab-on-a-chip and optical components. Injection molding has proven to be a feasible and efficient way to manufacture such components. In injection molding, the mold surface topogra...

  12. Bilaterally Microstructured Thin Polydimethylsiloxane Film Production

    DEFF Research Database (Denmark)

    Vudayagiri, Sindhu; Yu, Liyun; Hassouneh, Suzan Sager;

    2015-01-01

    Thin PDMS films with complex microstructures are used in the manufacturing of dielectric electro active polymer (DEAP) actuators, sensors and generators, to protect the metal electrode from large strains and to assure controlled actuation. The current manufacturing process at Danfoss Polypower A/...

  13. Microstructured extremely thin absorber solar cells

    DEFF Research Database (Denmark)

    Biancardo, Matteo; Krebs, Frederik C

    2007-01-01

    In this paper we present the realization of extremely thin absorber (ETA) solar cells employing conductive glass substrates functionalized with TiO2 microstructures produced by embossing. Nanocrystalline or compact TiO2 films on Indium doped tin oxide (ITO) glass substrates were embossed...

  14. Topological microstructure analysis using persistence landscapes

    Science.gov (United States)

    Dłotko, Paweł; Wanner, Thomas

    2016-11-01

    Phase separation mechanisms can produce a variety of complicated and intricate microstructures, which often can be difficult to characterize in a quantitative way. In recent years, a number of novel topological metrics for microstructures have been proposed, which measure essential connectivity information and are based on techniques from algebraic topology. Such metrics are inherently computable using computational homology, provided the microstructures are discretized using a thresholding process. However, while in many cases the thresholding is straightforward, noise and measurement errors can lead to misleading metric values. In such situations, persistence landscapes have been proposed as a natural topology metric. Common to all of these approaches is the enormous data reduction, which passes from complicated patterns to discrete information. It is therefore natural to wonder what type of information is actually retained by the topology. In the present paper, we demonstrate that averaged persistence landscapes can be used to recover central system information in the Cahn-Hilliard theory of phase separation. More precisely, we show that topological information of evolving microstructures alone suffices to accurately detect both concentration information and the actual decomposition stage of a data snapshot. Considering that persistent homology only measures discrete connectivity information, regardless of the size of the topological features, these results indicate that the system parameters in a phase separation process affect the topology considerably more than anticipated. We believe that the methods discussed in this paper could provide a valuable tool for relating experimental data to model simulations.

  15. Optimizing the microstructure of dissipative materials

    DEFF Research Database (Denmark)

    Andreassen, Erik; Lazarov, Boyan Stefanov; Jensen, Jakob Søndergaard

    The aim of this work is to present a method to design material microstructures with high dissipation using topology optimization. In order to compute the macroscopic energy dissipation in periodic structures, we focus both on capturing the physical dissipation mechanism and to find the effective...

  16. Spontaneous emission from active dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Tromborg, Bjarne

    2001-01-01

    and engineered due to the dependence of the emission rate on the location and polarisation of the emitters in the structure. This paper addresses the methods of quantum electrodynamics of dielectric media which enable calculation of the local rate of spontaneous emission in active microstructures....

  17. Microstructured optical fiber refractive index sensor

    DEFF Research Database (Denmark)

    Town, Graham E.; McCosker, Ravi; Yuan, Scott Wu

    2010-01-01

    We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show that sel...

  18. Microstructure and transformation kinetics in bainitic steels

    NARCIS (Netherlands)

    Luzginova, N.V.

    2008-01-01

    With the aim of reaching a better understanding of the microstructure evolution and the overall phase transformation kinetics in hyper-eutectoid steels a commercial SAE 52100 bearing steel and 7 model alloys with different concentrations of chromium, cobalt and aluminum have been studied in this wor

  19. On the microstructure of bituminous binders

    NARCIS (Netherlands)

    Fischer, H.R.; Dillingh, E.C.; Hermse, C.G.M.

    2014-01-01

    The objective of this work is to study the common features and the evolution of microstructures of bituminous binders regardless of their grade (PEN 10/20 to 160/220) and source/origin using the atomic force microscope operated in phase contrast mode. All bituminous binders show the same microstruct

  20. Elastocapillary fabrication of three-dimensional microstructures

    NARCIS (Netherlands)

    Honschoten, van J.W.; Berenschot, J.W.; Ondarcuhu, T.; Sanders, R.G.P.; Sundaram, J.; Elwenspoek, M.; Tas, N.R.

    2010-01-01

    We describe the fabrication of three-dimensional microstructures by means of capillary forces. Using an origami-like technique, planar silicon nitride structures of various geometries are folded to produce three-dimensional objects of 50–100 m. Capillarity is a particularly effective mechanism since

  1. Microstructure and transformation kinetics in bainitic steels

    NARCIS (Netherlands)

    Luzginova, N.V.

    2008-01-01

    With the aim of reaching a better understanding of the microstructure evolution and the overall phase transformation kinetics in hyper-eutectoid steels a commercial SAE 52100 bearing steel and 7 model alloys with different concentrations of chromium, cobalt and aluminum have been studied in this

  2. Microstructural characterization of stone wool fibre network

    DEFF Research Database (Denmark)

    Chapelle, Lucie; Brøndsted, Povl; Kusano, Yukihiro;

    2014-01-01

    Understanding the mechanical properties of fibrous network as complex as stone wool materials requires a relevant description of their microstructure and architecture. In this study, different methods have been proposed to characterize the fibre orientation, diameter and length of fibres as well...

  3. Influence of Material Microstructures in Micromilling of Ti6Al4V Alloy

    Science.gov (United States)

    Attanasio, Aldo; Gelfi, Marcello; Pola, Annalisa; Ceretti, Elisabetta; Giardini, Claudio

    2013-01-01

    In the most recent decades the introduction of unconventional machining processes allowed the development of micromachining techniques. In this work, the influence of material microstructures on the micromilling process was investigated. Ti6Al4V alloy was selected as workpiece material since it is a very common material for micro applications and because its duplex microstructure can be easily changed by proper thermal treatments. Four different microstructures (namely bimodal, fully equiaxed, fully lamellar and mill annealed) were obtained through recrystallization annealing treatments carried out at different times and temperatures. The mechanical properties of the samples were assessed by microhardness measurements. Nano-indentations were also performed on single grains to understand how the different hardness of phases and structures present in the Ti6Al4V alloy can affect the micromilling process. Microchannels using two flute flat end mills with a diameter equal to 200 µm were realized on the treated samples. Two different feed-per-tooth values were used during the tests. Cutting force, channel shape and burr dimension were investigated. Morphological and energy dispersive spectroscopy (EDS) analyses were performed on tools by means of a scanning electron microscope (SEM): in this way the phenomena mainly influencing the tool status were also identified. Lower cutting forces and reduced tool wear were observed when working fully lamellar microstructures compared to the other ones. PMID:28788331

  4. Microstructures in a ternary eutectic alloy: devising metrics based on neighbourhood relationships

    Science.gov (United States)

    Dennstedt, A.; Choudhury, A.; Ratke, L.; Nestler, B.

    2016-03-01

    Ternary eutectics, where three phases form simultaneously from the melt, present an opportunity to study the fundamental science of microstructural pattern formation during the process of solidification. In this paper we investigate these phenomena, both experimentally and by phase-field simulations. The aim is to develop necessary characterisation tools which can be applied to both experimentally determined and simulated microstructures for a quantitative comparison between simulations and experiments. In SEM images of experimental cross sections of directionally solidified Ag-Al-Cu ternary eutectic alloy at least six different types of microstructures are observed. Corresponding 3D phase-field simulations for different solidification conditions and compositions allow us to span and isolate the material parameters which influence the formation of three-phase patterns. Both experimental and simulated microstructures were analysed regarding interface lengths, triple points and number of neighbours. As a result of this integrated experimental and computational effort we conclude that neighbourhood relationships as described herein, turn out to be an appropriate basis to characterise order in patterns.

  5. Microstructural Anisotropy of Magnetocaloric Gadolinium Cylinders: Effect on the Mechanical Properties of the Material

    Directory of Open Access Journals (Sweden)

    Darja Steiner Petrovič

    2016-05-01

    Full Text Available The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy, EDS (Energy-dispersive X-ray Spectroscopy, and BSE (Back-scattered Electrons in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces.

  6. A novel method for evaluating brain function and microstructural changes in Parkinson′s disease

    Directory of Open Access Journals (Sweden)

    Ming-fang Jiang

    2015-01-01

    Full Text Available In this study, microstructural brain damage in Parkinson′s disease patients was examined using diffusion tensor imaging and tract-based spatial statistics. The analyses revealed the presence of neuronal damage in the substantia nigra and putamen in the Parkinson′s disease patients. Moreover, disease symptoms worsened with increasing damage to the substantia nigra, confirming that the substantia nigra and basal ganglia are the main structures affected in Parkinson′s disease. We also found that microstructural damage to the putamen, caudate nucleus and frontal lobe positively correlated with depression. Based on the tract-based spatial statistics, various white matter tracts appeared to have microstructural damage, and this correlated with cognitive disorder and depression. Taken together, our results suggest that diffusion tensor imaging and tract-based spatial statistics can be used to effectively study brain function and microstructural changes in patients with Parkinson′s disease. Our novel findings should contribute to our understanding of the histopathological basis of cognitive dysfunction and depression in Parkinson′s disease.

  7. Altered Sputum Microstructure as a Marker of Airway Obstruction in Cystic Fibrosis Patients

    Science.gov (United States)

    Duncan, Gregg; Jung, James; West, Natalie; Boyle, Michael; Suk, Jung Soo; Hanes, Justin

    In the lungs of cystic fibrosis (CF) patients, highly viscoelastic mucus remains stagnant in the lung leading to obstructed airways prone to recurrent infections. Bulk-fluid rheological measurement is primarily used to assess the pathological features of mucus. However, this approach is limited in detecting microscopic properties on the length scale of pathogens and immune cells. We have shown in prior work based on the transport of muco-inert nanoparticles (MIP) in CF sputum that patients can carry significantly different microstructural properties. In this study, we aimed to determine the factors leading to variations between patients in sputum microstructure and their clinical implications. The microrheological properties of CF sputum were measured using multi-particle tracking experiments of MIP. MIP were made by grafting polyethylene glycol onto the surface of polystyrene nanoparticles which prior work has shown prevents adhesion to CF sputum. Biochemical analyses show that sputum microstructure was significantly altered by elevated mucin and DNA content. Reduction in sputum pore size is characteristic of patients with obstructed airways as indicated by measured pulmonary function tests. Our microstructural read-out may serve as a novel biomarker for CF.

  8. Facile fabrication of hierarchical ZnO microstructures assisted with PAMPSA and enhancement of green emission

    Science.gov (United States)

    Huang, Qiang; Cun, Tangxiang; Zuo, Wenbin; Liu, Jianping

    2015-03-01

    We report the fabrication of hierarchically microstructured flower-like ZnO by a facile and single-step procedure involving poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) assisted aqueous chemical method. The shapes and sizes can be controlled just by varying the concentrations of the water-soluble polymer. When a suitable PAMPAS concentration was utilized, uniform well-defined and mono-dispersed chrysanthemum-like ZnO microstructures based on nanorod building blocks were obtained. The formation mechanism of the hierarchical structure was presented. The structured studies using XRD, HRTEM and SAED reveal these ZnO nanorods are composed of a single phase nature with wurtzite structure and grow along with the c-axis. FTIR spectrum indicated the incorporation of a trace of PAMPSA into ZnO crystals. HRTEM, Raman and XPS analyses showed that the hierarchical ZnO microstructures contain high concentration of oxygen vacancies which enable them exhibiting a significant intense deep-level emission centered at green luminescence in its photoluminescence spectra. They also show enhanced photocatalytic efficiency in degradation of methylene blue. It is hoped that the present work may provide a simple method to fabricate ZnO hierarchical microstructures and a positive relationship among polar plane, oxygen vacancy and green emission.

  9. Three-dimensional Reconstruction of the Microstructure of Human Acellular Nerve Allograft

    Science.gov (United States)

    Zhu, Shuang; Zhu, Qingtang; Liu, Xiaolin; Yang, Weihong; Jian, Yutao; Zhou, Xiang; He, Bo; Gu, Liqiang; Yan, Liwei; Lin, Tao; Xiang, Jianping; Qi, Jian

    2016-01-01

    The exact inner 3D microstructure of the human peripheral nerve has been a mystery for decades. Therefore, it has been difficult to solve several problems regarding peripheral nerve injury and repair. We used high-resolution X-ray computed microtomography (microCT) to scan a freeze-dried human acellular nerve allograft (hANA). The microCT images were then used to reconstruct a 3D digital model, which was used to print a 3D resin model of the nerve graft. The 3D digital model of the hANA allowed visualization of all planes. The magnified 3D resin model clearly showed the nerve bundles and basement membrane tubes of the hANA. Scanning electron microscopy (SEM) was used to analyse the microstructure of the hANA. Compared to the SEM images, the microCT image clearly demonstrated the microstructure of the hANA cross section at a resolution of up to 1.2 μm. The 3D digital model of the hANA facilitates a clear and easy understanding of peripheral nerve microstructure. Furthermore, the enlarged 3D resin model duplicates the unique inner structure of each individual hANA. This is a crucial step towards achieving 3D printing of a hANA or nerve that can be used as a nerve graft. PMID:27476584

  10. Development of Microstructure and Crystallographic Texture in a Double-Sided Friction Stir Welded Microalloyed Steel

    Science.gov (United States)

    Rahimi, S.; Wynne, B. P.; Baker, T. N.

    2017-01-01

    The evolution of microstructure and crystallographic texture has been investigated in double-sided friction stir welded microalloyed steel, using electron backscatter diffraction (EBSD). The microstructure analyses show that the center of stirred zone reached a temperature between Ac1 and Ac3 during FSW, resulting in a dual-phase austenitic/ ferritic microstructure. The temperatures in the thermo-mechanically affected zone and the overlapped area between the first and second weld pass did not exceed the Ac1. The shear generated by the rotation probe occurs in austenitic/ferritic phase field where the austenite portion of the microstructure is transformed to a bainitic ferrite, on cooling. Analysis of crystallographic textures with regard to shear flow lines generated by the probe tool shows the dominance of simple shear components across the whole weld. The austenite texture at Ac1 - Ac3 is dominated by the B { {1bar{1}2} }stirred zone and the ferrites in the thermo-mechanically affected zones and the overlapped area underwent shear deformation with textures dominated by the D1 { {bar{1}bar{1}2} }weld pass. This is due to continuous dynamic strain-induced recrystallization as a result of simultaneous severe shear deformation and drastic undercooling.

  11. Microstructural Anisotropy of Magnetocaloric Gadolinium Cylinders: Effect on the Mechanical Properties of the Material.

    Science.gov (United States)

    Petrovič, Darja Steiner; Šturm, Roman; Naglič, Iztok; Markoli, Boštjan; Pepelnjak, Tomaž

    2016-05-17

    The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces.

  12. Equivalent Antisymmetry Performance of Three-Dimensional Heterogeneous Anisotropic Composites

    Institute of Scientific and Technical Information of China (English)

    李永; 宋健; 张志民

    2003-01-01

    Starting from the physical features of materials, heterogeneous anisotropic composites (HACs) are analysed on the basis of the understanding and applications of its equivalent antisymmetry performance. Moreover, the design parameter is optimized to attain the goal of maximizing the use of materials, which is quite meaningful. The HAC structure is defined as a kind of equivalent structures according to the structure and properties of materials.We apply the mature plate theory and the composite materials laminate theory in analysis of the HAC structure,and in this way a new concept and a new idea are expected.

  13. Wireless sensors in heterogeneous networked systems configuration and operation middleware

    CERN Document Server

    Cecilio, José

    2014-01-01

    This book presents an examination of the middleware that can be used to configure and operate heterogeneous node platforms and sensor networks. The middleware requirements for a range of application scenarios are compared and analysed. The text then defines middleware architecture that has been integrated in an approach demonstrated live in a refinery. Features: presents a thorough introduction to the major concepts behind wireless sensor networks (WSNs); reviews the various application scenarios and existing middleware solutions for WSNs; discusses the middleware mechanisms necessary for hete

  14. Titanium oxide incorporation on zeolites for heterogeneous photocatalisis

    OpenAIRE

    Merg, Jean C.; Franciele Rossett; Penha,Fábio G; Sibele B. C Pergher; Petkowicz,Diego I.; João H. Z. dos Santos

    2010-01-01

    This work proposes the study of heterogeneous photocatalysis using TiO2 impregnated in zeolites beta, ZSM-5, mordenite, NaXb, NaXp and NaY for the decomposition of methylene blue. The catalysts were characterized by XRD, IR, textural analyses by N2 adsorption, SEM, DRS and the reaction of decomposition was monitored by UV visible. The results indicated that didn't have structural changes in the catalysts after Ti impregnations, only in the case of NaY and NaX zeolites. The better photocatalys...

  15. Comparison of one-dimensional probabilistic finite element method with direct numerical simulation of dynamically loaded heterogeneous materials

    Science.gov (United States)

    Robbins, Joshua; Voth, Thomas

    2011-06-01

    Material response to dynamic loading is often dominated by microstructure such as grain topology, porosity, inclusions, and defects; however, many models rely on assumptions of homogeneity. We use the probabilistic finite element method (WK Liu, IJNME, 1986) to introduce local uncertainty to account for material heterogeneity. The PFEM uses statistical information about the local material response (i.e., its expectation, coefficient of variation, and autocorrelation) drawn from knowledge of the microstructure, single crystal behavior, and direct numerical simulation (DNS) to determine the expectation and covariance of the system response (velocity, strain, stress, etc). This approach is compared to resolved grain-scale simulations of the equivalent system. The microstructures used for the DNS are produced using Monte Carlo simulations of grain growth, and a sufficient number of realizations are computed to ensure a meaningful comparison. Finally, comments are made regarding the suitability of one-dimensional PFEM for modeling material heterogeneity. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  16. Purchasing Power Parity and Heterogeneous Mean Reversion

    NARCIS (Netherlands)

    C.G. Koedijk (Kees); B. Tims (Ben); M.A. van Dijk (Mathijs)

    2005-01-01

    textabstractThis paper analyzes the properties of multivariate tests of purchasing power parity (PPP) that fail to take heterogeneity in the speed of mean reversion across real exchange rates into account. We compare the performance of homogeneous and heterogeneous unit root testing methodologies.

  17. Fixed export cost heterogeneity, trade and welfare

    DEFF Research Database (Denmark)

    Jørgensen, Jan Guldager; Schröder, Philipp J.H.

    2008-01-01

    Recent literature on the workhorse model of intra-industry trade has explored heterogeneous cost structures at the firm level. These approaches have proven to add realism and predictive power. This paper presents a new and simple heterogeneous-firms specification. We develop a symmetric two...

  18. Hybrid Interconnect Design for Heterogeneous Hardware Accelerators

    NARCIS (Netherlands)

    Pham-Quoc Cuong, P.

    2015-01-01

    Heterogeneous multicore systems are becoming increasingly important as the need for computation power grows, especially when we are entering into the big data era. As one of the main trends in heterogeneous multicore, hardware accelerator systems provide application specific hardware circuits and

  19. Modelling income processes with lots of heterogeneity

    DEFF Research Database (Denmark)

    Browning, Martin; Ejrnæs, Mette; Alvarez, Javier

    2010-01-01

    this observable homogeneity, we find more latent heterogeneity than previous investigators. We show that allowance for heterogeneity makes substantial differences to estimates of model parameters and to outcomes of interest. Additionally, we find strong evidence against the hypothesis that any worker has a unit...

  20. Characterizing heterogeneous cellular responses to perturbations.

    Science.gov (United States)

    Slack, Michael D; Martinez, Elisabeth D; Wu, Lani F; Altschuler, Steven J

    2008-12-01

    Cellular populations have been widely observed to respond heterogeneously to perturbation. However, interpreting the observed heterogeneity is an extremely challenging problem because of the complexity of possible cellular phenotypes, the large dimension of potential perturbations, and the lack of methods for separating meaningful biological information from noise. Here, we develop an image-based approach to characterize cellular phenotypes based on patterns of signaling marker colocalization. Heterogeneous cellular populations are characterized as mixtures of phenotypically distinct subpopulations, and responses to perturbations are summarized succinctly as probabilistic redistributions of these mixtures. We apply our method to characterize the heterogeneous responses of cancer cells to a panel of drugs. We find that cells treated with drugs of (dis-)similar mechanism exhibit (dis-)similar patterns of heterogeneity. Despite the observed phenotypic diversity of cells observed within our data, low-complexity models of heterogeneity were sufficient to distinguish most classes of drug mechanism. Our approach offers a computational framework for assessing the complexity of cellular heterogeneity, investigating the degree to which perturbations induce redistributions of a limited, but nontrivial, repertoire of underlying states and revealing functional significance contained within distinct patterns of heterogeneous responses.