WorldWideScience

Sample records for grain growth process

  1. Manufacturing process to reduce large grain growth in zirconium alloys

    International Nuclear Information System (INIS)

    Rosecrans, P.M.

    1987-01-01

    A method is described of treating cold worked zirconium alloys to reduce large grain growth during thermal treatment above its recrystallization temperature. The method comprises heating the zirconium alloy at a temperature of about 1300 0 F. to 1350 0 F. for about 1 to 3 hours subsequent to cold working the zirconium alloy and prior to the thermal treatment at a temperature of between 1450 0 -1550 0 F., the thermal treatment temperature being above the recrystallization temperature

  2. Multiseeding with (100)/(100) Grain Junctions in Top Seeded Melt Growth Processed YBCO Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.J.; Gee, Y.A.; Hong, G.W. [Korea Atomic Energy Research Institute, Taejon (Korea); Kim, H.J.; Joo, J.H. [Sungkyunkwan University, Suwon (Korea); Han, S.C.; Han, Y.H.; Sung, T.H.; Kim, S.J. [Korea Electric Power Research Institute, Taejon (Korea)

    2000-06-01

    Multiseeding with (100)/(100) grain junctions of top-seeded melt growth (TSMG) processed YBCO superconductors was studied. Multiple seeding shortened the processing time for the fabrication of TSMG-processed YBCO superconductors. The relationship among the number of seeds, the levitation forces and the trapped magnetic fields of the TSMG-processed YBCO samples is reported. The characteristic of the (100)/(100) grain junction is discussed in terms of a wetting angle of a melt. (author). 25 refs., 7 figs.

  3. Analysis of grain growth process in melt spun Fe-B alloys under the initial saturated grain boundary segregation condition

    International Nuclear Information System (INIS)

    Chen, Z.; Liu, F.; Yang, X.Q.; Fan, Y.; Shen, C.J.

    2012-01-01

    Highlights: → We compared pure kinetic, pure thermodynamic and extended thermo-kinetic models. → An initial saturated GB segregation condition of nanoscale Fe-B alloys was determined. → The controlled-mechanism was proposed using two characteristic times (t 1 and t 2 ). - Abstract: A grain growth process in the melt spun low-solid-solubility Fe-B alloys was analyzed under the initial saturated grain boundary (GB) segregation condition. Applying melt spinning technique, single-phase supersaturated nanograins were prepared. Grain growth behavior of the single-phase supersaturated nanograins was investigated by performing isothermal annealing at 700 deg. C. Combined with the effect of GB segregation on the initial GB excess amount, the thermo-kinetic model [Chen et al., Acta Mater. 57 (2009) 1466] was extended to describe the initial GB segregation condition of nanoscale Fe-B alloys. In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, an initial saturated GB segregation condition was determined. The controlled-mechanism of grain growth under initial saturated GB segregation condition was proposed using two characteristic annealing times (t 1 and t 2 ), which included a mainly kinetic-controlled process (t ≤ t 1 ), a transition from kinetic-mechanism to thermodynamic-mechanism (t 1 2 ) and pure thermodynamic-controlled process (t ≥ t 2 ).

  4. Large-scale grain growth in the solid-state process: From "Abnormal" to "Normal"

    Science.gov (United States)

    Jiang, Minhong; Han, Shengnan; Zhang, Jingwei; Song, Jiageng; Hao, Chongyan; Deng, Manjiao; Ge, Lingjing; Gu, Zhengfei; Liu, Xinyu

    2018-02-01

    Abnormal grain growth (AGG) has been a common phenomenon during the ceramic or metallurgy processing since prehistoric times. However, usually it had been very difficult to grow big single crystal (centimeter scale over) by using the AGG method due to its so-called occasionality. Based on the AGG, a solid-state crystal growth (SSCG) method was developed. The greatest advantages of the SSCG technology are the simplicity and cost-effectiveness of the technique. But the traditional SSCG technology is still uncontrollable. This article first summarizes the history and current status of AGG, and then reports recent technical developments from AGG to SSCG, and further introduces a new seed-free, solid-state crystal growth (SFSSCG) technology. This SFSSCG method allows us to repeatedly and controllably fabricate large-scale single crystals with appreciable high quality and relatively stable chemical composition at a relatively low temperature, at least in (K0.5Na0.5)NbO3(KNN) and Cu-Al-Mn systems. In this sense, the exaggerated grain growth is no longer 'Abnormal' but 'Normal' since it is able to be artificially controllable and repeated now. This article also provides a crystal growth model to qualitatively explain the mechanism of SFSSCG for KNN system. Compared with the traditional melt and high temperature solution growth methods, the SFSSCG method has the advantages of low energy consumption, low investment, simple technique, composition homogeneity overcoming the issues with incongruent melting and high volatility. This SFSSCG could be helpful for improving the mechanical and physical properties of single crystals, which should be promising for industrial applications.

  5. Investigation of the instability and low water kefir grain growth during an industrial water kefir fermentation process.

    Science.gov (United States)

    Laureys, David; Van Jean, Amandine; Dumont, Jean; De Vuyst, Luc

    2017-04-01

    A poorly performing industrial water kefir production process consisting of a first fermentation process, a rest period at low temperature, and a second fermentation process was characterized to elucidate the causes of its low water kefir grain growth and instability. The frozen-stored water kefir grain inoculum was thawed and reactivated during three consecutive prefermentations before the water kefir production process was started. Freezing and thawing damaged the water kefir grains irreversibly, as their structure did not restore during the prefermentations nor the production process. The viable counts of the lactic acid bacteria and yeasts on the water kefir grains and in the liquors were as expected, whereas those of the acetic acid bacteria were high, due to the aerobic fermentation conditions. Nevertheless, the fermentations progressed slowly, which was caused by excessive substrate concentrations resulting in a high osmotic stress. Lactobacillus nagelii, Lactobacillus paracasei, Lactobacillus hilgardii, Leuconostoc mesenteroides, Bifidobacterium aquikefiri, Gluconobacter roseus/oxydans, Gluconobacter cerinus, Saccharomyces cerevisiae, and Zygotorulaspora florentina were the most prevalent microorganisms. Lb. hilgardii, the microorganism thought to be responsible for water kefir grain growth, was not found culture-dependently, which could explain the low water kefir grain growth of this industrial process.

  6. Concepts on Low Temperature Mechanical Grain Growth

    Energy Technology Data Exchange (ETDEWEB)

    Sharon, John Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Metallurgy and Materials Joining Dept.; Boyce, Brad Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Metallurgy and Materials Joining Dept.

    2013-11-01

    In metals, as grain size is reduced below 100nm, conventional dislocation plasticity is suppressed resulting in improvements in strength, hardness, and wears resistance. Existing and emerging components use fine grained metals for these beneficial attributes. However, these benefits can be lost in service if the grains undergo growth during the component’s lifespan. While grain growth is traditionally viewed as a purely thermal process that requires elevated temperature exposure, recent evidence shows that some metals, especially those with nanocrystalline grain structure, can undergo grain growth even at room temperature or below due to mechanical loading. This report has been assembled to survey the key concepts regarding how mechanical loads can drive grain coarsening at room temperature and below. Topics outlined include the atomic level mechanisms that facilitate grain growth, grain boundary mobility, and the impact of boundary structure, loading scheme, and temperature.

  7. A model for strain hardening, recovery, recrystallization and grain growth with applications to forming processes of nickel base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Riedel, Hermann, E-mail: hermann.riedel@iwm.fraunhofer.de [Fraunhofer Institute for Materials Mechanics, Wöhlerstr. 11, 79108 Freiburg (Germany); Svoboda, Jiri, E-mail: svobj@ipm.cz [Institute of Physics of Materials, Academy of Science of the Czech Republic, Zizkova 22, Brno (Czech Republic)

    2016-05-17

    An ensemble of n spherical grains is considered, each of which is characterized by its radius r{sub i} and by a hardening variable a{sub i}. The hardening variable obeys a Chaboche-type evolution equation with dynamic and static recovery. The grain growth law includes the usual contribution of the grain boundary energy, a term for the stored energy associated with the hardening variable, and the Zener pinning force exerted by particles on the migrating grain boundaries. New grains develop by recrystallization in grains whose stored energy density exceeds a critical value. The growth or shrinkage of the particles, which restrain grain boundary migration, obeys a thermodynamic/kinetic evolution equation. This set of first order differential equations for r{sub i}, a{sub i} and the particle radius is integrated numerically. Fictitious model parameters for a virtual nickel base alloy are used to demonstrate the properties and capabilities of the model. For a real nickel alloy, model parameters are adjusted using measured stress-strain curves, as well as recrystallized volume fractions and grain size distributions. Finally the model with adjusted parameters is applied to a forming process with complex temperature-strain rate histories.

  8. Computer simulation of grain growth in HAZ

    Science.gov (United States)

    Gao, Jinhua

    Two different models for Monte Carlo simulation of normal grain growth in metals and alloys were developed. Each simulation model was based on a different approach to couple the Monte Carlo simulation time to real time-temperature. These models demonstrated the applicability of Monte Carlo simulation to grain growth in materials processing. A grain boundary migration (GBM) model coupled the Monte Carlo simulation to a first principle grain boundary migration model. The simulation results, by applying this model to isothermal grain growth in zone-refined tin, showed good agreement with experimental results. An experimental data based (EDB) model coupled the Monte Carlo simulation with grain growth kinetics obtained from the experiment. The results of the application of the EDB model to the grain growth during continuous heating of a beta titanium alloy correlated well with experimental data. In order to acquire the grain growth kinetics from the experiment, a new mathematical method was developed and utilized to analyze the experimental data on isothermal grain growth. Grain growth in the HAZ of 0.2% Cu-Al alloy was successfully simulated using the EDB model combined with grain growth kinetics obtained from the experiment and measured thermal cycles from the welding process. The simulated grain size distribution in the HAZ was in good agreement with experimental results. The pinning effect of second phase particles on grain growth was also simulated in this work. The simulation results confirmed that by introducing the variable R, degree of contact between grain boundaries and second phase particles, the Zener pinning model can be modified as${D/ r} = {K/{Rf}}$where D is the pinned grain size, r the mean size of second phase particles, K a constant, f the area fraction (or the volume fraction in 3-D) of second phase.

  9. Stochastic theory of grain growth

    International Nuclear Information System (INIS)

    Hu Haiyun; Xing Xiusan.

    1990-11-01

    The purpose of this note is to set up a stochastic theory of grain growth and to derive the statistical distribution function and the average value of the grain radius so as to match them with the experiment further. 8 refs, 1 fig

  10. Effect of V-Nd co-doping on phase transformation and grain growth process of TiO2

    Science.gov (United States)

    Khatun, Nasima; Amin, Ruhul; Anita, Sen, Somaditya

    2018-05-01

    The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2.

  11. Investigation of fatigue crack growth rate of Al 5484 ultrafine grained alloy after ECAP process

    Energy Technology Data Exchange (ETDEWEB)

    Brynk, Tomasz; Rasinski, Marcin; Pakiela, Zbigniew; Kurzydlowski, Krzysztof J. [Faculty of Materials Science and Engineering, Warsaw University of Technology (Poland); Olejnik, Lech [Faculty of Production Engineering, Warsaw University of Technology (Poland)

    2010-05-15

    During the last decade equal-channel angular pressing (ECAP) has emerged as a widely used fabrication route of ultrafine-grained (UFG) metals and alloys. Enhanced mechanical properties of UFG materials produced by severe plastic deformation, with a grain size smaller than 1 {mu}m, have been reported in a large number of publications. However, the higher strength does not imply higher resistance to fatigue both high- and low-cyclic. In fact, due to reduced plasticity, higher fatigue crack propagation rates are reported for UFG materials, particularly in low-amplitude range. The aim of this work was to investigate fatigue crack propagation in samples of Al 5483 alloy subjected to ECAP treatment. Because of small dimensions of the coupons processed by ECAP, non-standard, mini-samples were used in a crack propagation tests. Two test procedures were used to estimate stress intensity factor (K). The first was based on optical measurements of crack length from images recorded during the test. The second method was based on digital image correlation (DIC), which was used to determine K value directly from displacement field near the crack tip. Comparison of these two methods is made and the relationship between the intensity of ECAP process (measured in terms of the number of ECAP passes) and fatigue crack propagation rates proposed. In addition to fatigue resistance, the results of tensile tests carried out with mini-samples are presented. Applicability of such samples in the investigations of the mechanical properties of UFG materials is discussed. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  12. Effects of grain size distribution on the interstellar dust mass growth

    OpenAIRE

    Hirashita, Hiroyuki; Kuo, Tzu-Ming

    2011-01-01

    Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size di...

  13. Grain growth in UO2

    International Nuclear Information System (INIS)

    Hastings, I.J.; Scoberg, J.A.; Walden, W.

    1979-06-01

    Grain growth studies have been carried out on UO 2 to provide data for the fuel modelling program and to evaluate fuel fabricated in commissioning the Mixed Oxide Fuel Fabrication Laboratory at Chalk River Nuclear Laboratories. Fuel examined includes natural UO 2 commercially fabricated from ADU powder for CANDU reactors; natural UO 2 commercially fabricated from AU powder; natural UO 2 from ADU and AU powder, fabricated in the MOFFL; and commercially fabricated UO 2 enriched 1.7, 4.5, and 9.6 wt. percent U-235 in U. Samples were step-annealed in vacuo at 1870-2070 K for up to 32.5 h. All data fit a (grain size)sup(2.5) versus annealing time relationship. Apparent activation energy for grain growth, Q, depends on fuel type and varies from 150+-10 kJ/mol for early AU powder to 360+-10 kJ/mol for pellets from ADU fabricated in the MOFFL. Grain sizes calculated using the laboratory equation in a fuel performance code tend to be greater than those measured in irradiated natural fuel, suggesting irradiation-induced inhibition of grain growth. However, any inhibition is equivalent to that expected for a systematic 5 percent underpredicition in reactor power. (author)

  14. Statistical Theory of Normal Grain Growth Revisited

    International Nuclear Information System (INIS)

    Gadomski, A.; Luczka, J.

    2002-01-01

    In this paper, we discuss three physically relevant problems concerning the normal grain growth process. These are: Infinite vs finite size of the system under study (a step towards more realistic modeling); conditions of fine-grained structure formation, with possible applications to thin films and biomembranes, and interesting relations to superplasticity of materials; approach to log-normality, an ubiquitous natural phenomenon, frequently reported in literature. It turns out that all three important points mentioned are possible to be included in a Mulheran-Harding type behavior of evolving grains-containing systems that we have studied previously. (author)

  15. Abnormal Grain Growth Suppression in Aluminum Alloys

    Science.gov (United States)

    Hales, Stephen J. (Inventor); Claytor, Harold Dale (Inventor); Alexa, Joel A. (Inventor)

    2015-01-01

    The present invention provides a process for suppressing abnormal grain growth in friction stir welded aluminum alloys by inserting an intermediate annealing treatment ("IAT") after the welding step on the article. The IAT may be followed by a solution heat treatment (SHT) on the article under effectively high solution heat treatment conditions. In at least some embodiments, a deformation step is conducted on the article under effective spin-forming deformation conditions or under effective superplastic deformation conditions. The invention further provides a welded article having suppressed abnormal grain growth, prepared by the process above. Preferably the article is characterized with greater than about 90% reduction in area fraction abnormal grain growth in any friction-stir-welded nugget.

  16. Grain-growth law during Stage 1 sintering of materials

    International Nuclear Information System (INIS)

    He Zeming; Ma, J.

    2002-01-01

    This work investigates the grain-growth behaviour of powder compact during Stage 1 sintering (<90{%} theoretical density). It is widely accepted that grain size is an important state variable in the constitutive modelling in material sintering. However, it is noted that all the existing grain-growth laws proposed in the literature do not incorporate the effect of externally applied stress independently. In this work, a grain-growth law with externally applied stress as a variable was proposed. Alumina powders were forge-sintered at different applied stresses to examine the proposed grain-growth relationship. The proposed grain-growth law was then applied to model the grain-growth process on the sinter forging of tool steel. It is shown that the present proposed grain-growth law provides a good description on the experimental results. (author)

  17. Grain nucleation and growth during phase transformations

    DEFF Research Database (Denmark)

    Offerman, S.E.; Dijk, N.H. van; Sietsma, J.

    2002-01-01

    of individual grains. Our measurements show that the activation energy for grain nucleation is at least two orders of magnitude smaller than that predicted by thermodynamic models. The observed growth curves of the newly formed grains confirm the parabolic growth model but also show three fundamentally...... different types of growth. Insight into the grain nucleation and growth mechanisms during phase transformations contributes to the development of materials with optimal mechanical properties....

  18. Grain-boundary engineering applied to grain growth in a high temperature material

    International Nuclear Information System (INIS)

    Huda, Z.

    1993-01-01

    Crystallography of grain boundaries are determined for a high temperature material, before and after grain growth processes, so as to study the induction of special properties useful for application in components of a gas-turbine engine. The philosophy of grain-boundary engineering is applied to grain growth in APK-6, a powder formed nickel-base superalloy so as to establish the possible structure/property relationships. The alloy in the as received condition is shown to possess a strong texture and contained coincident site lattices (CSL) boundaries with most boundaries having sigma values in the range of 3 > sigma > 25. A normal grain-growth heat treatment result in a good population of low angle grain boundaries, and drastically reduces the proportion of CSL boundaries. A strong [011] annealing texture is observed after an intermediate grain growth; most grain boundaries, here, tend to be high angle indicating a possibility of possessing special properties. (author)

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  20. Phase field simulation of grain growth in porous uranium dioxide

    International Nuclear Information System (INIS)

    Ahmed, Karim; Pakarinen, Janne; Allen, Todd; El-Azab, Anter

    2014-01-01

    Graphical abstract: Display Omitted -- Abstract: A novel phase field model has been developed to investigate grain growth in porous polycrystalline UO 2 . Based on a system of Cahn–Hilliard and Allen–Cahn equations, the model takes into consideration both the curvature driven grain boundary motion and pore migration by surface diffusion. As such, the model accounts for the interaction between pore and grain boundary kinetics, which tends to retard the growth process. The phase field model parameters are found in terms of measurable material properties. Hence, quantitative results that can be compared with experiments were obtained. The model has been used to investigate the effect of porosity on the kinetics of grain growth in UO 2 . It is found that, as the amount of porosity increases, grain growth in UO 2 gradually changes from boundary controlled growth to pore controlled growth. For high porosity levels, the grain growth completely stops after a short evolution time. It is also found that the inhomogeneous distribution of pores leads to abnormal grain growth even without taking into account the anisotropy in grain boundary energy and mobility. The effects of porosity, temperature and initial microstructure on grain growth were thoroughly investigated. The model predictions are in good agreement with published experimental results of grain growth in UO 2

  1. Grain growth studies on nanocrystalline Ni powder

    International Nuclear Information System (INIS)

    Rane, G.K.; Welzel, U.; Mittemeijer, E.J.

    2012-01-01

    The microstructure of nanocrystalline Ni powder produced by ball-milling and its thermal stability were investigated by applying different methods of X-ray diffraction line-profile analysis: single-line analysis, whole powder-pattern modelling and the (modified) Warren–Averbach method were employed. The kinetics of grain growth were investigated by both ex-situ and in-situ X-ray diffraction measurements. With increasing milling time, the grain-size reduction is accompanied by a considerable narrowing of the size distribution and an increase in the microstrain. Upon annealing, initial, rapid grain growth occurs, accompanied by the (almost complete) annihilation of microstrain. For longer annealing times, the grain-growth kinetics depend on the initial microstructure: a smaller microstrain with a broad grain-size distribution leads to linear grain growth, followed by parabolic grain growth, whereas a larger microstrain with a narrow grain-size distribution leads to incessant linear grain growth. These effects have been shown to be incompatible with grain-boundary curvature driven growth. The observed kinetics are ascribed to the role of excess free volume at the grain boundaries of nanocrystalline material and the prevalence of an “abnormal grain-growth” mechanism.

  2. Randomly grain growth in metallic materials

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, A. [Instituto Politecnico Nacional, (SEPI-ESIME), Unidad Profesional Ticoman, Av. Ticoman 600, Del. G.A.M., C.P. 07340 Distrito Federal, Mexico (Mexico); Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico)], E-mail: adaramil@yahoo.com.mx; Chavez, F. [Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico); Demedices, L. [Instituto Politecnico Nacional, (SEPI-ESIME), Unidad Profesional Ticoman, Av. Ticoman 600, Del. G.A.M., C.P. 07340 Distrito Federal, Mexico (Mexico); Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico); Cruz, A.; Macias, M. [Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico)

    2009-10-30

    Computational modeling of grain structures is a very important topic in materials science. In this work, the development of the computational algorithms for a mathematical model to predict grain nucleation and grain growth is presented. The model place a number of nucleated points randomly in a liquid pool according with the solid and liquid fractions (X{sub sol} and X{sub liq}) of metal solute and the local temperature distribution (SS{sub I,J}). Then these points grows isotropically until obtain a grain structure with straight interfaces. Different grain morphologies such as columnar and equiaxed can be obtained as a function of the temperature distributions and growth directions.

  3. Randomly grain growth in metallic materials

    International Nuclear Information System (INIS)

    Ramirez, A.; Chavez, F.; Demedices, L.; Cruz, A.; Macias, M.

    2009-01-01

    Computational modeling of grain structures is a very important topic in materials science. In this work, the development of the computational algorithms for a mathematical model to predict grain nucleation and grain growth is presented. The model place a number of nucleated points randomly in a liquid pool according with the solid and liquid fractions (X sol and X liq ) of metal solute and the local temperature distribution (SS I,J ). Then these points grows isotropically until obtain a grain structure with straight interfaces. Different grain morphologies such as columnar and equiaxed can be obtained as a function of the temperature distributions and growth directions.

  4. A new treatment of transient grain growth

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; Fratzl, P.; Zickler, G. A.; Fischer, F. D.

    2016-01-01

    Roč. 115, AUG (2016), s. 442-447 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA15-06390S Institutional support: RVO:68081723 Keywords : Grain size distribution * Grain growth * Growth kinetics * Thermodynamic modelling * Numerical solution of integro-differential equations Subject RIV: BJ - Thermodynamic s Impact factor: 5.301, year: 2016

  5. Equi-axed and columnar grain growth in UO2

    International Nuclear Information System (INIS)

    White, R.J.

    1997-01-01

    The grain size of UO 2 is an important parameter in the actual performance and the modelling of the performance of reactor fuel elements. Many processes depend critically on the grain size, for example, the degree of initial densification, the evolution rate of stable fission gases, the release rates of radiologically hazardous fission products, the fission gas bubble swelling rates and the fuel creep. Many of these processes are thermally activated and further impact on the fuel thermal behavior thus creating complex feedback processes. In order to model the fuel performance accurately it is necessary to model the evolution of the fuel grain radius. When UO 2 is irradiated, the fission gases xenon and krypton are created from the fissioning uranium nucleus. At high temperatures these gases diffuse rapidly to the grain boundaries where they nucleate immobile lenticular shaped fission gas bubbles. In this paper the Hillert grain growth model is adapted to account for the inhibiting ''Zener'' effects of grain boundary fission gas porosity on grain boundary mobility and hence grain growth. It is shown that normal grain growth ceases at relatively low levels of irradiation. At high burnups, high temperatures and in regions of high temperature gradients, columnar grain growth is often observed, in some cases extending over more than fifty percent of the fuel radius. The model is further extended to account for the de-pinning of grains in the radial direction by the thermal gradient induced force on a fission gas grain boundary bubble. The observed columnar/equi-axed boundary is in fair agreement with the predictions of an evaporation/condensation model. The grain growth model described in this paper requires information concerning the scale of grain boundary porosity, the local fuel temperature and the local temperature gradient. The model is currently used in the Nuclear Electric version of the ENIGMA fuel modelling code. (author). 14 refs, 3 figs, 1 tab

  6. Methods of assessing grain-size distribution during grain growth

    DEFF Research Database (Denmark)

    Tweed, Cherry J.; Hansen, Niels; Ralph, Brian

    1985-01-01

    This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related...... distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference...

  7. Stress-driven grain growth

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1998-11-13

    Full Text Available of length b (1+ epsilon) is parallel to sigma, embedded in a grain in which the lattice vector b (1+ epsilon) is transverse to sigma. If the embedded grain grows at the expense of its matrix, the source of the stress will do work, and therefore the presence...

  8. Modelling grain growth in the framework of Rational Extended Thermodynamics

    International Nuclear Information System (INIS)

    Kertsch, Lukas; Helm, Dirk

    2016-01-01

    Grain growth is a significant phenomenon for the thermomechanical processing of metals. Since the mobility of the grain boundaries is thermally activated and energy stored in the grain boundaries is released during their motion, a mutual interaction with the process conditions occurs. To model such phenomena, a thermodynamic framework for the representation of thermomechanical coupling phenomena in metals including a microstructure description is required. For this purpose, Rational Extended Thermodynamics appears to be a useful tool. We apply an entropy principle to derive a thermodynamically consistent model for grain coarsening due to the growth and shrinkage of individual grains. Despite the rather different approaches applied, we obtain a grain growth model which is similar to existing ones and can be regarded as a thermodynamic extension of that by Hillert (1965) to more general systems. To demonstrate the applicability of the model, we compare our simulation results to grain growth experiments in pure copper by different authors, which we are able to reproduce very accurately. Finally, we study the implications of the energy release due to grain growth on the energy balance. The present unified approach combining a microstructure description and continuum mechanics is ready to be further used to develop more elaborate material models for complex thermo-chemo-mechanical coupling phenomena. (paper)

  9. Modelling grain growth in the framework of Rational Extended Thermodynamics

    Science.gov (United States)

    Kertsch, Lukas; Helm, Dirk

    2016-05-01

    Grain growth is a significant phenomenon for the thermomechanical processing of metals. Since the mobility of the grain boundaries is thermally activated and energy stored in the grain boundaries is released during their motion, a mutual interaction with the process conditions occurs. To model such phenomena, a thermodynamic framework for the representation of thermomechanical coupling phenomena in metals including a microstructure description is required. For this purpose, Rational Extended Thermodynamics appears to be a useful tool. We apply an entropy principle to derive a thermodynamically consistent model for grain coarsening due to the growth and shrinkage of individual grains. Despite the rather different approaches applied, we obtain a grain growth model which is similar to existing ones and can be regarded as a thermodynamic extension of that by Hillert (1965) to more general systems. To demonstrate the applicability of the model, we compare our simulation results to grain growth experiments in pure copper by different authors, which we are able to reproduce very accurately. Finally, we study the implications of the energy release due to grain growth on the energy balance. The present unified approach combining a microstructure description and continuum mechanics is ready to be further used to develop more elaborate material models for complex thermo-chemo-mechanical coupling phenomena.

  10. Fenton process-affected transformation of roxarsone in paddy rice soils: Effects on plant growth and arsenic accumulation in rice grain.

    Science.gov (United States)

    Qin, Junhao; Li, Huashou; Lin, Chuxia

    2016-08-01

    Batch and greenhouse experiments were conducted to examine the effects of Fenton process on transformation of roxarsone in soils and its resulting impacts on the growth of and As uptake by a rice plant cultivar. The results show that addition of Fenton reagent markedly accelerated the degradation of roxarsone and produced arsenite, which was otherwise absent in the soil without added Fenton reagent. Methylation of arsenate was also enhanced by Fenton process in the earlier part of the experiment due to abundant supply of arsenate from Roxarsone degradation. Overall, addition of Fenton reagent resulted in the predominant presence of arsenate in the soils. Fenton process significantly improved the growth of rice in the maturity stage of the first crop, The concentration of methylated As species in the rice plant tissues among the different growth stages was highly variable. Addition of Fenton reagent into the soils led to reduced uptake of soil-borne As by the rice plants and this had a significant effect on reducing the accumulation of As in rice grains. The findings have implications for understanding As biogeochemistry in paddy rice field receiving rainwater-borne H2O2 and for development of mitigation strategies to reduce accumulation of As in rice grains. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. The influence of slow cooling on Y211 size and content in single-grain YBCO bulk superconductor through the infiltration-growth process

    Energy Technology Data Exchange (ETDEWEB)

    Ouerghi, A [Systems and Applied Mechanics Laboratory LASMAP, Polytechnic School of Tunisia, Rue El Kawarezmi La Marsa 743, Université de Carthage Tunis (Tunisia); Moutalbi, N., E-mail: nahed.moutalbi@yahoo.fr [Systems and Applied Mechanics Laboratory LASMAP, Polytechnic School of Tunisia, Rue El Kawarezmi La Marsa 743, Université de Carthage Tunis (Tunisia); Noudem, J.G. [CRISMAT-ENSICAEN (UMR-CNRS 6508), Université de Caen-Basse-Normandie, F-14050 Caen (France); LUSAC, Université de Caen-Basse-Normandie F-50130 Cherbourg-Octeville (France); M' chirgui, A. [Systems and Applied Mechanics Laboratory LASMAP, Polytechnic School of Tunisia, Rue El Kawarezmi La Marsa 743, Université de Carthage Tunis (Tunisia)

    2017-03-15

    Highlights: • YBCO bulk superconductors are produced by optimized Seeded Infiltration and Growth process. • The slow cooling time, in a fixed slow cooling temperature window, affects considerably the surface morphology and the bulk’s microstructure. • The Y211 particle’s size and content depend on the slow cooling time and its distribution behavior changes from one position to another. • There is an optimum slow cooling time, estimated to 88h, over which the shrinkage for both the liquid phase and the Y211 pellet is maximal, without any improvement of the crystal grain growth. • The magnetic trapped flux distribution for a given sample brings out the single grain characteristic. - Abstract: Highly textured YBa{sub 2}Cu{sub 3}O{sub 7-δ} (Y123) superconductors were produced using modified Textured Top Seeded Infiltration Growth (TSIG) process. The liquid source is made of only Y123 powder whereas the solid source is composed of Y{sub 2}BaCuO{sub 5} (Y211) powder. We aim to control the amount of liquid that infiltrates the solid pellet, which in turn controls the final amount of Y{sub 2}BaCuO{sub 5} particles in Y123 matrix. The effect of the slow cooling kinetics on sample morphology, on grain growth and on final microstructure was too investigated. It is shown that appropriate slow cooling time may also contribute to the control of the amount of Y211 inclusions in the final structure of Y123 bulk. We report herein the Y211 particle size and density distribution in the whole Y123 matrix. The present work proves that finest Y211 particles locate under the seed and that their size and density increase with distance from the seed.

  12. Novel mechanisms for solid-state processing and grain growth with microstructure alignment in alnico-8 based permanent magnets

    Science.gov (United States)

    Kassen, Aaron G.; White, Emma M. H.; Hu, Liangfa; Tang, Wei; Zhou, Lin; Kramer, Matthew J.; Anderson, Iver E.

    2018-05-01

    An estimated 750,000 new hybrid electric and plug-in battery vehicles, most with permanent magnet synchronous alternating current (PMAC) drive motors, took to the road in 2016 alone. Accompanied by 40% year over year growth in the EV market significant challenges exist in producing large quantities of permanent magnets (on the order of tens of millions) for reliable, low-cost traction motors [IE Agency, Energy Technology Perspectives (2017)]. Since the rare earth permanent magnet (REPM) market is essentially 100% net import reliant in the United States and has proven to have an unstable cost and supply structure in recent years, a replacement RE-free PM material must be designed or selected, fully developed, and implemented. Alnico, with its high saturation magnetization and excellent thermal stability, appears to be uniquely suited for this task. Further, while alnico typically has been considered a relatively low coercivity hard magnet, strides have been made to increase the coercivity to levels suitable for traction drive motors [W Tang, IEEE Trans. Magn., 51 (2015)]. If a simple non-cast approach for achieving near [001] easy axis grain aligned permanent magnets can be found, this would allow mass-produced final-shape anisotropic high energy product magnets suitable for usage in compact high RPM rotor designs. Therefore, a powder metallurgical approach is being explored that uses classic compression molding with "de-bind and sinter" methods, where a novel applied uniaxial loading, and an applied magnetic field may create final-shape magnets with highly textured resulting microstructures by two different mechanisms. Results indicate a positive correlation between applied uniaxial load and resulting texture (Fig. 1), along with benefits from using an applied magnetic field for improved texture, as well. The apparent mechanisms and resulting properties will be described using closed loop hysteresisgraph measurements, EBSD orientation mapping, and high

  13. Monte Carlo simulation of grain growth

    Directory of Open Access Journals (Sweden)

    Paulo Blikstein

    1999-07-01

    Full Text Available Understanding and predicting grain growth in Metallurgy is meaningful. Monte Carlo methods have been used in computer simulations in many different fields of knowledge. Grain growth simulation using this method is especially attractive as the statistical behavior of the atoms is properly reproduced; microstructural evolution depends only on the real topology of the grains and not on any kind of geometric simplification. Computer simulation has the advantage of allowing the user to visualize graphically the procedures, even dynamically and in three dimensions. Single-phase alloy grain growth simulation was carried out by calculating the free energy of each atom in the lattice (with its present crystallographic orientation and comparing this value to another one calculated with a different random orientation. When the resulting free energy is lower or equal to the initial value, the new orientation replaces the former. The measure of time is the Monte Carlo Step (MCS, which involves a series of trials throughout the lattice. A very close relationship between experimental and theoretical values for the grain growth exponent (n was observed.

  14. Abnormal grain growth: a non-equilibrium thermodynamic model for multi-grain binary systems

    International Nuclear Information System (INIS)

    Svoboda, J; Fischer, F D

    2014-01-01

    Abnormal grain growth as the abrupt growth of a group of the largest grains in a multi-grain system is treated within the context of unequal retardation of grain growth due to the segregation of solute atoms from the bulk of the grains into the grain boundaries. During grain boundary migration, the segregated solute atoms are dragged under a small driving force or left behind the migrating grain boundary under a large driving force. Thus, the solute atoms in the grain boundaries of large grains, exhibiting a large driving force, can be released from the grain boundary. The mobility of these grain boundaries becomes significantly higher and abnormal grain growth is spontaneously provoked. The mean-field model presented here assumes that each grain is described by its grain radius and by its individual segregation parameter. The thermodynamic extremal principle is engaged to obtain explicit evolution equations for the radius and segregation parameter of each grain. Simulations of grain growth kinetics for various conditions of segregation with the same initial setting (100 000 grains with a given radius distribution) are presented. Depending on the diffusion coefficients of the solute in the grain boundaries, abnormal grain growth may be strongly or marginally pronounced. Solute segregation and drag can also significantly contribute to the stabilization of the grain structure. Qualitative agreement with several experimental results is reported. (paper)

  15. Grain growth in ultrafine titanium powders during sintering

    International Nuclear Information System (INIS)

    Panigrahi, B.B.; Godkhindi, M.M.

    2006-01-01

    Grain growth behaviour of fine (∼3 μm) and attrition milled nanocrystalline (∼32 nm) titanium powers during sintering have been studied. The activation energies of grain growth (Q g ) in fine titanium were found to be 192.9 and 142.4 kJ/mol at lower and higher temperature ranges, respectively. The nanocrystalline titanium showed very low values of Q g (54.6 kJ/mol) at lower temperatures and it increased to 273.2 kJ/mol at higher temperatures. The constant (n) in nano Ti system was found to have unusually very high values of 6.5-8.2. The grain boundary rotation along with the diffusional processes could be the grain growth mechanism in nanocrystalline and in fine titanium powders

  16. Investigation of grain competitive growth during directional solidification of single-crystal nickel-based superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xinbao [National Energy R and D Center of Clean and High-Efficiency Fossil-Fired Power Generation Technology, Xi' an Thermal Power Research Institute Co. Ltd., Xi' an (China); Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, Xi' an (China); Liu, Lin; Zhang, Jun [Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, Xi' an (China)

    2015-08-15

    Grain competitive growth of nickel-based single-crystal superalloys during directional solidification was investigated. A detailed characterization of bi-crystals' competitive growth was performed to explore the competitive grain evolution. It was found that high withdrawal rate improved the efficiency of grain competitive growth. The overgrowth rate was increased when the misorientation increased. Four patterns of grain competitive growth with differently oriented dispositions were characterized. The results indicated that the positive branching of the dendrites played a significant role in the competitive growth process. The effect of crystal orientation and heat flow on the competitive growth can be attributed to the blocking mechanism between the adjacent grains. (orig.)

  17. A grain-boundary diffusion model of dynamic grain growth during superplastic deformation

    International Nuclear Information System (INIS)

    Kim, Byung-Nam; Hiraga, Keijiro; Sakka, Yoshio; Ahn, Byung-Wook

    1999-01-01

    Dynamic grain growth during superplastic deformation is modelled on the basis of a grain-boundary diffusion mechanism. On the grain boundary where a static and a dynamic potential difference coexist, matter transport along the boundary is assumed to contribute to dynamic grain growth through depositing the matter on the grain surface located opposite to the direction of grain-boundary migration. The amount of the diffusive matter during deformation is calculated for an aggregate of spherical grains and is converted to the increment of mean boundary migration velocity. The obtained relationship between the strain rate and the dynamic grain growth rate is shown to be independent of deformation mechanisms, provided that the grain growth is controlled by grain-boundary diffusion. The strain dependence, strain-rate dependence and temperature dependence of grain growth predicted from this model are consistent with those observed in superplastic ZrO 2 -dispersed Al 2 O 3

  18. Accretion growth of water-ice grains in astrophysically-relevant dusty plasma experiment

    Science.gov (United States)

    Chai, Kil-Byoung; Marshall, Ryan; Bellan, Paul

    2016-10-01

    The grain growth process in the Caltech water-ice dusty plasma experiment has been studied using a high-speed camera equipped with a long-distance microscope lens. It is found that (i) the ice grain number density decreases four-fold as the average grain length increases from 20 to 80 um, (ii) the ice grain length has a log-normal distribution rather than a power-law dependence, and (iii) no collisions between ice grains are apparent. The grains have a large negative charge so the agglomeration growth is prevented by their strong mutual repulsion. It is concluded that direct accretion of water molecules is in good agreement with the observed ice grain growth. The volumetric packing factor of the ice grains must be less than 0.25 in order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains; this conclusion is consistent with ice grain images showing a fractal character.

  19. Mesoscopic simulation of recrystallization and grain growth

    International Nuclear Information System (INIS)

    Rollett, A.D.

    2000-01-01

    A brief summary of simulation techniques for recrystallization and grain growth is given. The available methods include surface evolver, front tracking (including finite element methods and vertex methods), networks of curves, phase field, cellular automata, and Monte Carlo. Two of the models that use a regular lattice, the Potts model and the Cellular Automaton (CA) model, have proved to be very useful. Microstructure is represented on a discrete lattice where the value of the field at each point represents the local orientation of the material and boundaries exist between points of unlike orientation. Two issues are discussed: one is a hybrid approach to combining the standard Monte Carlo and cellular automata algorithms for recrystallization modeling. The second is adaptation of the MC method for modeling grain growth (and recrystallization) with physically based boundary properties. Both models have significant limitations in their standard forms. The CA model is very useful and efficient for simulating recrystallization with deterministic motion of the recrystallization fronts. It can be adapted to simulate curvature driven migration provided that multiple sub-lattices are used with a probabilistic switching rule. The Potts model is very successful in modeling curvature driven boundary migration and grain growth. It does not simulate the proportionality between boundary velocity and a stored energy driving force, however, unless rather restricted conditions of stored energy (in relation to the grain boundary energy) and lattice temperature are satisfied. A new approach based on a hybrid of the Potts model (MC) and the Cellular Automaton (CA) model has been developed to obtain the desired limiting behavior for both curvature-driven and stored energy-driven grain boundary migration. The combination of methods is achieved by interleaving the two different types of reorientation event in time. The results show that the hybrid algorithm models the Gibbs

  20. Evolution of grain boundary character distributions in alloy 825 tubes during high temperature annealing: Is grain boundary engineering achieved through recrystallization or grain growth?

    International Nuclear Information System (INIS)

    Bai, Qin; Zhao, Qing; Xia, Shuang; Wang, Baoshun; Zhou, Bangxin; Su, Cheng

    2017-01-01

    Grain boundary engineering (GBE) of nickel-based alloy 825 tubes was carried out with different cold drawing deformations by using a draw-bench on a factory production line and subsequent annealing at various temperatures. The microstructure evolution of alloy 825 during thermal-mechanical processing (TMP) was characterized by means of the electron backscatter diffraction (EBSD) technique to study the TMP effects on the grain boundary network and the evolution of grain boundary character distributions during high temperature annealing. The results showed that the proportion of ∑ 3 n coincidence site lattice (CSL) boundaries of alloy 825 tubes could be increased to > 75% by the TMP of 5% cold drawing and subsequent annealing at 1050 °C for 10 min. The microstructures of the partially recrystallized samples and the fully recrystallized samples suggested that the proportion of low ∑ CSL grain boundaries depended on the annealing time. The frequency of low ∑ CSL grain boundaries increases rapidly with increasing annealing time associating with the formation of large-size highly-twinned grains-cluster microstructure during recrystallization. However, upon further increasing annealing time, the frequency of low ∑ CSL grain boundaries decreased markedly during grain growth. So it is concluded that grain boundary engineering is achieved through recrystallization rather than grain growth. - Highlights: •The grain boundary engineering (GBE) is applicable to 825 tubes. •GBE is achieved through recrystallization rather than grain growth. •The low ∑ CSL grain boundaries in 825 tubes can be increased to > 75%.

  1. Nanoscale grain growth behaviour of CoAl intermetallic synthesized ...

    Indian Academy of Sciences (India)

    Grain growth behaviour of the nanocrystalline CoAl intermetallic compound synthesized by mechanical alloying has been studied by isothermal annealing at different temperatures and durations. X-ray diffraction method was employed to investigate structural evolutions during mechanical alloying and annealing processes.

  2. UO2 Grain Growth: Developing Phase Field Models for Pore Dragging, Solute Dragging and Anisotropic Grain Boundary Energies

    International Nuclear Information System (INIS)

    Ahmed, K.; Tonks, M.; Zhang, Y.; Biner, B.

    2016-01-01

    A detailed phase field model for the effect of pore drag on grain growth kinetics was implemented in MARMOT. The model takes into consideration both the curvature-driven grain boundary motion and pore migration by surface diffusion. As such, the model accounts for the interaction between pore and grain boundary kinetics, which tends to retard the grain growth process. Our 2D and 3D simulations demonstrate that the model capture all possible pore-grain boundary interactions proposed in theoretical models. For high enough surface mobility, the pores move along with the migrating boundary as a quasi-rigid-body, albeit hindering its migration rate compared to the pore-free case. For less mobile pores, the migrating boundary can separate from the pores. For the pore-controlled grain growth kinetics, the model predicts a strong dependence of the growth rate on the number of pores, pore size, and surface diffusivity in agreement with theroretical models. An evolution equation for the grain size that includes these parameters was derived and showed to agree well with numerical solution. It shows a smooth transition from boundary-controlled kinetics to pore-controlled kinetics as the surface diffusivity decreases or the number of pores or their size increases. This equation can be utilized in BISON to give accurate estimate for the grain size evolution. This will be accomplished in the near future. The effect of solute drag and anisotropy of grain boundary on grain growth will be investigated in future studies.

  3. Growth rate of YBCO-Ag superconducting single grains

    Science.gov (United States)

    Congreve, J. V. J.; Shi, Y. H.; Dennis, A. R.; Durrell, J. H.; Cardwell, D. A.

    2017-12-01

    The large scale use of (RE)Ba2Cu3O7 bulk superconductors, where RE=Y, Gd, Sm, is, in part, limited by the relatively poor mechanical properties of these inherently brittle ceramic materials. It is reported that alloying of (RE)Ba2Cu3O7 with silver enables a significant improvement in the mechanical strength of bulk, single grain samples without any detrimental effect on their superconducting properties. However, due to the complexity and number of inter-related variables involved in the top seeded melt growth (TSMG) process, the growth of large single grains is difficult and the addition of silver makes it even more difficult to achieve successful growth reliably. The key processing variables in the TSMG process include the times and temperatures of the stages within the heating profile, which can be derived from the growth rate during the growth process. To date, the growth rate of the YBa2Cu3O7-Ag system has not been reported in detail and it is this lacuna that we have sought to address. In this work we measure the growth rate of the YBCO-Ag system using a method based on continuous cooling and isothermal holding (CCIH). We have determined the growth rate by measuring the side length of the crystallised region for a number of samples for specified isothermal hold temperatures and periods. This has enabled the growth rate to be modelled and from this an optimized heating profile for the successful growth of YBCO-Ag single grains to be derived.

  4. The destruction and growth of dust grains in interstellar space

    International Nuclear Information System (INIS)

    Barlow, M.J.

    1978-01-01

    The processes governing the destruction and growth of dust grains in interstellar space are investigated with a view to establishing the conditions required for the existence of ice mantles. In this paper sputtering by particles with energies in the eV to GeV range is considered. Previous sputtering yield estimates which were based on theoretical considerations are shown to be greatly in error for incident particle energies of less than 1 keV. Empirical formulae for the sputtering threshold energy and the sputtering yield are derived from the extensive experimental data available. The sputtering of grains in H II regions, in the inter-cloud medium, and in shock waves produced by cloud-cloud collisions and by supernova remnants, is investigated. Of these, supernova remnants are shown to be the most important, leading to lifetimes of approximately 2 x 10 8 yr for ice grains and between 5 to 20 x 10 8 yr for refractory grains. Destruction rates are estimated for grains bombarded by MeV and GeV cosmic rays. It is shown that collision cascade sputtering dominates evaporative sputtering produced by thermal spikes. It is also shown that even if all electron excitation energy loss in a grain material could be transferred to the lattice particles, the observed cosmic ray flux spectrum could not cause significant destruction of ice grains. (author)

  5. Abnormal grain growth: a non-equilibrium thermodynamic model for multi-grain binary systems

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; Fischer, F. D.

    2014-01-01

    Roč. 22, č. 1 (2014), Art . No. 015013 ISSN 0965-0393 Institutional support: RVO:68081723 Keywords : grain boundary segregation * abnormal grain growth * theory * modelling * solute drag Subject RIV: BJ - Thermodynamics Impact factor: 2.167, year: 2014

  6. Grain processes in massive star formation

    International Nuclear Information System (INIS)

    Wolfire, M.G.; Cassinelli, J.P.

    1986-01-01

    Observational evidence suggests that stars greater than 100 M(solar) exist in the Galaxy and Large Magellanic Cloud (LMC), however classical star formation theory predicts stellar mass limits of only approx. 60 M(solar). A protostellar accretion flow consists of inflowing gas and dust. Grains are destroyed as they are near the central protostar creating a dust shell or cocoon. Radiation pressure acting on the grain can halt the inflow of material thereby limiting the amount of mass accumulated by the protostar. We first consider rather general constraints on the initial grain to gas ratio and mass accretion rates that permit inflow. We further constrain these results by constructing a numerical model. Radiative deceleration of grains and grain destruction processes are explicitly accounted for in an iterative solution of the radiation-hydrodynamic equations. Findings seem to suggest that star formation by spherical accretion requires rather extreme preconditioning of the grain and gas environment

  7. Nanoscale abnormal grain growth in (001) epitaxial ceria

    International Nuclear Information System (INIS)

    Solovyov, Vyacheslav F.; Develos-Bagarinao, Katherine; Nykypanchuk, Dmytro

    2009-01-01

    X-ray reciprocal-space mapping and atomic force microscopy (AFM) are used to study kinetics and mechanisms of lateral grain growth in epitaxial (001) ceria (CeO 2 ) deposited by pulsed laser deposition on (001) yttria-stabilized zirconia (YSZ) and (12 lowbar 10) (r-cut) sapphire. Rate and character of the grain growth during postannealing at 1050 deg. C are found to be strongly dependent on the type of the epitaxial substrate. Films deposited on YSZ exhibit signatures of normal grain growth, which stagnated after the lateral grain size reaches 40 nm, consistent with the grain-boundary pinning by the thermal grooving. In contrast, when r-cut sapphire substrate was used, abnormal (secondary) grain growth is observed. A small population of grains grow to well over 100 nm consuming smaller, 100 nm large (001) terminations and rendering the sample single-crystalline quality. The grain growth is accompanied by reduction in lateral rms strain, resulting in a universal grain size--rms strain dependence. Analysis of the AFM and x-ray diffraction data leads to the conclusion that bimodal initial grain population consisting of grains with very different sizes is responsible for initiation of the abnormal growth in (001) CeO 2 films on r-cut sapphire. Due to different surface chemistry, when a YSZ substrate is used, the initial grain distribution is monomodal, therefore only normal growth is active. We demonstrate that a 2.2 deg. miscut of the sapphire substrate eliminates the large-grain population, thus suppressing abnormal grain growth. It is concluded that utilization of abnormal grain growth is a promising way for synthesis of large (001) ceria terminations.

  8. Anisotropic atomic packing model for abnormal grain growth mechanism of WC-25 wt.% Co alloy

    International Nuclear Information System (INIS)

    Ryoo, H.S.; Hwang, S.K.

    1998-01-01

    During liquid phase sintering, cemented carbide particles grow into either faceted or non-faceted grain shapes depending on ally system. In case of WC-Co alloy, prism-shape faceted grains with (0001) planes and {1 bar 100} planes on each face are observed, and furthermore an abnormal grain growth has been reported to occur. When abnormal grain growth occurs in WC crystals, dimension ratio, R, of the length of the side of the triangular prism face to the height of the prism is higher than 4 whereas that for normal grains is approximately 2. Abnormal grain growth in this alloy is accelerated by the fineness of starting powders and by high sintering temperature. To account for the mechanism of the abnormal grain growth, there are two proposed models which drew much research attention: nucleation and subsequent carburization and transformation of η (W 3 Co 3 C) phase into WC, and coalescence of coarse WC grains through dissolution and re-precipitation. Park et al. proposed a two-dimensional nucleation theory to explain the abnormal grain growth of faceted grains. There are questions, however, on the role of η phase on abnormal grain growth. The mechanism of coalescence of spherical grains as proposed by Kingery is also unsuitable for faceted grains. So far theories on abnormal grain growth do not provide a satisfactory explanation on the change of R value during the growth process. In the present work a new mechanism of nucleation and growth of faceted WC grains is proposed on the ground of anisotropic packing sequence of each atom

  9. Computer-aided analysis of grain growth in metals

    DEFF Research Database (Denmark)

    Klimanek, P.; May, C.; Richter, H.

    1993-01-01

    Isothermal grain growth in aluminium, copper and alpha-iron was investigated experimentally at elevated temperatures and quantitatively interpreted by computer simulation on the base of a statistical model described in [4,5,6]. As it is demonstrated for the grain growth kinetics, the experimental...... data can be fitted satisfactorly....

  10. Direct observation of densification and grain growth in a W--Ni alloy

    International Nuclear Information System (INIS)

    Riegger, H.; Pask, J.A.; Exner, H.E.

    1979-04-01

    Densification and grain growth in a tungsten--nickel alloy containing 32 vol % of liquid at 1550 0 C were studied by conventional methods aided by hot stage scanning electron microscopy and cinematography. This technique yields important additional qualitative information on the mechanisms. Two stages can be discerned. In stage 1, essentially complete pore elimination, rapid grain growth and adjustment of microstructural geometry take place. In the second stage, microstructure coarsening occurs which is characterized by geometric similarity. Columnar grain growth at the surface is observed due to squeezing out of Ni--W liquid, flooding of surface grains and fast evaporation of the Ni. The driving forces for these processes are discussed showing that a high ratio of grain boundary energy to liquid surface energy is essential. A W--Cu alloy with 32 vol % liquid at 1100 0 C did not show any grain growth due to essentially no solubility of W in Cu at this temperature

  11. Equi-axed and columnar grain growth in UO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    White, R J [Berkely Technology Centre, Nuclear Electric plc, Berkeley (United Kingdom)

    1997-08-01

    The grain size of UO{sub 2} is an important parameter in the actual performance and the modelling of the performance of reactor fuel elements. Many processes depend critically on the grain size, for example, the degree of initial densification, the evolution rate of stable fission gases, the release rates of radiologically hazardous fission products, the fission gas bubble swelling rates and the fuel creep. Many of these processes are thermally activated and further impact on the fuel thermal behavior thus creating complex feedback processes. In order to model the fuel performance accurately it is necessary to model the evolution of the fuel grain radius. When UO{sub 2} is irradiated, the fission gases xenon and krypton are created from the fissioning uranium nucleus. At high temperatures these gases diffuse rapidly to the grain boundaries where they nucleate immobile lenticular shaped fission gas bubbles. In this paper the Hillert grain growth model is adapted to account for the inhibiting ``Zener`` effects of grain boundary fission gas porosity on grain boundary mobility and hence grain growth. It is shown that normal grain growth ceases at relatively low levels of irradiation. At high burnups, high temperatures and in regions of high temperature gradients, columnar grain growth is often observed, in some cases extending over more than fifty percent of the fuel radius. The model is further extended to account for the de-pinning of grains in the radial direction by the thermal gradient induced force on a fission gas grain boundary bubble. The observed columnar/equi-axed boundary is in fair agreement with the predictions of an evaporation/condensation model. The grain growth model described in this paper requires information concerning the scale of grain boundary porosity, the local fuel temperature and the local temperature gradient. The model is currently used in the Nuclear Electric version of the ENIGMA fuel modelling code. (author). 14 refs, 3 figs, 1 tab.

  12. Correlation of thermodynamics and grain growth kinetics in nanocrystalline metals

    International Nuclear Information System (INIS)

    Song Xiaoyan; Zhang Jiuxing; Li Lingmei; Yang Keyong; Liu Guoquan

    2006-01-01

    We investigated the correlation of thermodynamics and grain growth kinetics of nanocrystalline metals both theoretically and experimentally. A model was developed to describe the thermodynamic properties of nanograin boundaries, which could give reliable predictions in the destabilization characteristics of nanograin structures and the slowing down of grain growth kinetics at a constant temperature. Both the temperature-varying and isothermal nanograin growth behaviors in pure nanocrystalline Co were studied to verify the thermodynamic predictions. The experimental results showing that discontinuous nanograin growth takes place at a certain temperature and grain growth rate decreases monotonically with time confirm our thermodynamics-based description of nanograin growth characteristics. Therefore, we propose a thermodynamic viewpoint to explain the deviation of grain growth kinetics in nanocrystalline metals from those of polycrystalline materials

  13. A comparison of grain boundary evolution during grain growth in fcc metals

    International Nuclear Information System (INIS)

    Brons, J.G.; Thompson, G.B.

    2013-01-01

    Grain growth of Cu and Ni thin films, subjected to in situ annealing within a transmission electron microscope, has been quantified using a precession-enhanced electron diffraction technique. The orientation of each grain and its misorientation with respect to its neighboring grains were calculated. The Cu underwent grain growth that maintained a monomodal grain size distribution, with its low-angle grain boundaries being consumed, and the Ni exhibited grain size distributions in stages, from monomodal to bimodal to monomodal. The onset of Ni’s abnormal grain growth was accompanied by a sharp increase in the Σ3 and Σ9 boundary fractions, which is attributed to simulation predictions of their increased mobility. These Σ3 and Σ9 fractions then dropped to their room temperature values during the third stage of grain growth. In addition to the Σ3 and Σ9 boundaries, the Σ5 and Σ7 boundaries also underwent an increase in total boundary fraction with increasing temperature in both metals

  14. The Pinning by Particles of Low and High Angle Grain Boundaries during Grain Growth

    DEFF Research Database (Denmark)

    Tweed, C.J.; Ralph, B.; Hansen, Niels

    1984-01-01

    A study has been made using transmission electron microscopy of the pinning of grain boundaries in aluminium during grain growth by fine dispersions of alumina particles. The boundary parameters have been determined with precision and the pinning effects measured using an approach due to Ashby...

  15. Growth of preexisting abnormal grains in molybdenum under static and dynamic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Noell, Philip J. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-0889 (United States); Worthington, Daniel L. [Verily Life Sciences, 269 E. Grand Ave., South San Francisco, CA 94080, USA (United States); Taleff, Eric M., E-mail: taleff@utexas.edu [The University of Texas at Austin, Department of Mechanical Engineering, 204 East Dean Keeton St., Stop C2200, Austin, TX 78712 (United States)

    2017-04-24

    This investigation compares the growth rates of preexisting abnormal grains under both static and dynamic conditions. Abnormal grains several millimeters in length were produced in two commercial-purity molybdenum (Mo) materials by tensile straining at temperatures from 1923 to 2073 K (1650–1800 °C). This process is termed dynamic abnormal grain growth (DAGG) because it produces abnormal grains during concurrent plastic straining. DAGG creates abnormal grains at much lower temperatures than does static abnormal grain growth (SAGG). Abnormal grains created through DAGG were characterized with their surrounding microstructures and were then subjected to annealing treatments. Only one-third of the preexisting abnormal grains subsequently grew by SAGG. Among these, SAGG occurred only in those specimens that required the largest strains to initiate DAGG when creating the abnormal grain(s). The rates of boundary migration observed for SAGG were approximately two orders of magnitude slower than those for DAGG. When DAGG in one specimen was interrupted by extended static annealing, it did not recur when straining resumed. The dislocation substructure developed during hot deformation, which includes subgrains typical of five-power creep, is critically important to both DAGG and SAGG of preexisting abnormal grains under the conditions examined.

  16. Advection-diffusion model for normal grain growth and the stagnation of normal grain growth in thin films

    International Nuclear Information System (INIS)

    Lou, C.

    2002-01-01

    An advection-diffusion model has been set up to describe normal grain growth. In this model grains are divided into different groups according to their topological classes (number of sides of a grain). Topological transformations are modelled by advective and diffusive flows governed by advective and diffusive coefficients respectively, which are assumed to be proportional to topological classes. The ordinary differential equations governing self-similar time-independent grain size distribution can be derived analytically from continuity equations. It is proved that the time-independent distributions obtained by solving the ordinary differential equations have the same form as the time-dependent distributions obtained by solving the continuity equations. The advection-diffusion model is extended to describe the stagnation of normal grain growth in thin films. Grain boundary grooving prevents grain boundaries from moving, and the correlation between neighbouring grains accelerates the stagnation of normal grain growth. After introducing grain boundary grooving and the correlation between neighbouring grains into the model, the grain size distribution is close to a lognormal distribution, which is usually found in experiments. A vertex computer simulation of normal grain growth has also been carried out to make a cross comparison with the advection-diffusion model. The result from the simulation did not verify the assumption that the advective and diffusive coefficients are proportional to topological classes. Instead, we have observed that topological transformations usually occur on certain topological classes. This suggests that the advection-diffusion model can be improved by making a more realistic assumption on topological transformations. (author)

  17. Search for grain growth toward the center of L1544

    NARCIS (Netherlands)

    Chacón-Tanarro, A.; Caselli, P.; Bizzocchi, L.; Pineda, J. E.; Harju, J.; Spaans, M.; Désert, F.-X.

    2017-01-01

    In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is not clear, however, if dust growth and coagulation take place before the protostar switches on. This is an important issue as the presence of large grains may affect the chemical structure of dense cloud cores,

  18. Grain Growth in Samples of Aluminum Containing Alumina Particles

    DEFF Research Database (Denmark)

    Tweed, C. J.; Hansen, Niels; Ralph, B.

    1983-01-01

    A study of the two-dimensional and three-dimensional grain size distributions before and after grain growth treatments has been made in samples having a range of oxide contents. In order to collect statistically useful amounts of data, an automatic image analyzer was used and the resulting data w...

  19. Grain Growth in Nanocrystalline Mg-Al Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Kruska, Karen; Rohatgi, Aashish; Vemuri, Venkata Rama Ses; Kovarik, Libor; Moser, Trevor H.; Evans, James E.; Browning, Nigel D.

    2017-10-05

    An improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg - Al thin films containing ~10 wt.% Al and with 14.5 nm average grain size were produced by magnetron-sputtering and subjected to heat-treatments. The grain growth evolution in the early stages of heat treatment at 423 K (150 °C), 473 K (200 °C) and 573K (300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7±2 and the activation energy for grain growth was 31.1±13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. The low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.

  20. Austenite Grain Growth Behavior of AISI 4140 Alloy Steel

    Directory of Open Access Journals (Sweden)

    Lin Wang

    2013-01-01

    Full Text Available AISI 4140 alloy steel is widely applied in the manufacture of various parts such as gears, rams, and spindles due to its good performance of strength, toughness, and wear resistance. The former researches most focused on its deformation and recrystallization behaviors under high temperature. However, the evolution laws of austenite grain growth were rarely studied. This behavior also plays an important role in the mechanical properties of parts made of this steel. In this study, samples are heated to a certain temperature of 1073 K, 1173 K, 1273 K, and 1373 K at a heating rate of 5 K per second and hold for different times of 0 s, 120 s, 240 s, 360 s, and 480 s before being quenched with water. The experimental results suggest that the austenite grains enlarge with increasing temperature and holding time. A mathematical model and an application developed in Matlab environment are established on the basis of previous works and experimental results to predict austenite grains size in hot deformation processes. The predicted results are in good agreement with experimental results which indicates that the model and the application are reliable.

  1. Strain-induced grain growth of cryomilled nanocrystalline Al in trimodal composites during forging

    International Nuclear Information System (INIS)

    Yao, B.; Simkin, B.; Majumdar, B.; Smith, C.; Bergh, M. van den; Cho, K.; Sohn, Y.H.

    2012-01-01

    Highlights: ► Grain growth of cryomilled nanocrystalline aluminum during hot forging. ► Use of hollow cone dark field imaging technique in TEM for grain size measurement. ► Grain growth model of strain, strain rate and temperature for forging optimization. - Abstract: Grain growth of nanocrystalline aluminum ( nc Al) in trimodal Al metal-matrix-composites (MMCs) during hot forging was investigated. The nc Al phase formed through cryomilling of inert gas-atomized powders in liquid nitrogen has an average grain size down to 21 nm, exhibits excellent thermal stability. However, substantial grain growth of nc Al up to 63 nm was observed when the Al MMCs were thermo-mechanically processed even at relatively low temperatures. Grain growth of the cryomilled nc Al phase in trimodal Al MMCs after hot forging was documented with respect to temperature ranging from 175 °C to 287 °C, true strain ranging from 0.4 to 1.35 and strain rate ranging from 0.1 to 0.5 s −1 . Hollow cone dark field imaging technique was employed to provide statistically confident measurements of nc Al grain size that ranged from 21 to 63 nm. An increase in forging temperature and an increase in true strain were correlated with an increase in grain size of nc Al. Results were correlated to devise a phenomenological grain growth model for forging that takes strain, strain rate and temperature into consideration. Activation energy for the grain growth during thermo-mechanical hot-forging was determined to be 35 kJ/mol, approximately a quarter of activation energy for bulk diffusion of Al and a half of activation energy for static recrystallization.

  2. Identification of Accretion as Grain Growth Mechanism in Astrophysically Relevant Water&ice Dusty Plasma Experiment

    Science.gov (United States)

    Marshall, Ryan S.; Chai, Kil-Byoung; Bellan, Paul M.

    2017-03-01

    The grain growth process in the Caltech water-ice dusty plasma experiment has been studied using a high-speed camera and a long-distance microscope lens. It is observed that (I) the ice grain number density decreases fourfold as the average grain major axis increases from 20 to 80 μm, (II) the major axis length has a log-normal distribution rather than a power-law dependence, and (III) no collisions between ice grains are apparent. The grains have a large negative charge resulting in strong mutual repulsion and this, combined with the fractal character of the ice grains, prevents them from agglomerating. In order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains, the volumetric packing factor (I.e., ratio of the actual volume to the volume of a circumscribing ellipsoid) of the ice grains must be less than ˜0.1 depending on the exact relative velocity of the grains in question. Thus, it is concluded that direct accretion of water molecules is very likely to dominate the observed ice grain growth.

  3. Identification of Accretion as Grain Growth Mechanism in Astrophysically Relevant Water–Ice Dusty Plasma Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, Ryan S.; Chai, Kil-Byoung; Bellan, Paul M. [Applied Physics and Materials Science, Caltech, Pasadena, CA 91125 (United States)

    2017-03-01

    The grain growth process in the Caltech water–ice dusty plasma experiment has been studied using a high-speed camera and a long-distance microscope lens. It is observed that (i) the ice grain number density decreases fourfold as the average grain major axis increases from 20 to 80 μ m, (ii) the major axis length has a log-normal distribution rather than a power-law dependence, and (iii) no collisions between ice grains are apparent. The grains have a large negative charge resulting in strong mutual repulsion and this, combined with the fractal character of the ice grains, prevents them from agglomerating. In order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains, the volumetric packing factor (i.e., ratio of the actual volume to the volume of a circumscribing ellipsoid) of the ice grains must be less than ∼0.1 depending on the exact relative velocity of the grains in question. Thus, it is concluded that direct accretion of water molecules is very likely to dominate the observed ice grain growth.

  4. The Relationship Between Debris and Grain Growth in Polycrystalline Ice

    Science.gov (United States)

    Rivera, A.; McCarthy, C.

    2017-12-01

    An understanding of the mechanisms of ice flow, as well as the factors that affect it, must be improved in order to make more accurate predictions of glacial melting rates, and hence, sea level rise. Both field and laboratory studies have made an association between smaller grain sizes of ice and more rapid deformation. Therefore, it is essential to understand the different factors that affect grain size. Observations from ice cores have shown a correlation between debris content in layers of ice with smaller grain sizes, whereas layers with very little debris have larger grain sizes. Static grain growth rates for both pure ice and ice containing bubbles are well constrained, but the effect of small rock/dust particles has received less attention. We tested the relationship between debris and grain growth in polycrystalline ice with controlled annealing at -5°C and microstructural characterization. Three samples, two containing fine rock powder and one without, were fabricated, annealed, and imaged over time. The samples containing powder had different initial grain sizes due to solidification temperature during fabrication. Microstructural analysis was done on all samples after initial fabrication and at various times during the anneal using a light microscope housed in a cold room. Microstructural images were analyzed by the linear-intercept method. When comparing average grain size over time between pure ice and ice with debris, it was found that the rate of growth for the pure ice was larger than the rate of growth for the ice with debris at both initial grain sizes. These results confirm the observations seen in nature, and suggest that small grain size is indeed influenced by debris content. By understanding this, scientists could gain a more in-depth understanding of internal ice deformation and the mechanisms of ice flow. This, in turn, helps improve the accuracy of glacial melting predictions, and sea level rise in the future.

  5. Simulation study on the growth of grains in dusty plasmas

    International Nuclear Information System (INIS)

    Sato, Tetsuya; Watanabe, Kunihiko

    1997-01-01

    A new particle simulation code is developed for studying the dynamics of the grains which are exposed to charging by the background plasma particles. Effects of regular attachment of electrons and ions, effects of secondary electron emission, and coagulation of grains are included in this code. Simulation results show that grains randomly change their charges from negative to positive, or from positive to negative in a 'flip-flop' fashion as a result of competition between the electron attachment and secondary electron emission. It is found that the flip-flop effect becomes remarkable when the radius of grains is of the order of 10 nm, because the attachment of a single electron to a grain is less effective on the surface potential for larger grains, while the average probability of electron attachment is smaller for smaller grains. Grains with opposite charges attract each other to coagulate, so that grains of size of 10 nm are likely to grow in size. The flip-flop effect is found to be essential to the growth of grains. (author)

  6. Grain growth kinetics for B2O3-doped ZnO ceramics

    Directory of Open Access Journals (Sweden)

    Yuksel Berat

    2015-06-01

    Full Text Available Grain growth kinetics in 0.1 to 2 mol % B2O3-added ZnO ceramics was studied by using a simplified phenomenological grain growth kinetics equation Gn = K0 · t · exp(-Q/RT together with the physical properties of sintered samples. The samples, prepared by conventional ceramics processing techniques, were sintered at temperatures between 1050 to 1250 °C for 1, 2, 3, 5 and 10 hours in air. The kinetic grain growth exponent value (n and the activation energy for the grain growth of the 0.1 mol % B2O3-doped ZnO ceramics were found to be 2.8 and 332 kJ/mol, respectively. By increasing B2O3 content to 1 mol %, the grain growth exponent value (n and the activation energy decreased to 2 and 238 kJ/mol, respectively. The XRD study revealed the presence of a second phase, Zn3B2O6 formed when the B2O3 content was > 1 mol %. The formation of Zn3B2O6 phase gave rise to an increase of the grain growth kinetic exponent and the grain growth activation energy. The kinetic grain growth exponent value (n and the activation energy for the grain growth of the 2 mol % B2O3-doped ZnO ceramics were found to be 3 and 307 kJ/mol, respectively. This can be attributed to the second particle drag (pinning mechanism in the liquid phase sintering.

  7. AUTOMATION OF TRACEABILITY PROCESS AT GRAIN TERMINAL LLC “ UKRTRANSAGRO"

    Directory of Open Access Journals (Sweden)

    F. A. TRISHYN

    2017-07-01

    Full Text Available A positive trend of growth in both grain production and export is indicated. In the current marketing year the export potential of the Ukrainian grain market is close to the record level. However, the high positions in the rating of world exporters are achieved not only due to the high export potential, but also because of higher quality and logistics. These factors depend directly on the quality of enterprise management and all processes occurring at it. One of the perspective ways of enterprise development is the implementation of the traceability system and further automation of the traceability process. European integration laws are obliging Ukrainian enterprises to have a traceability system. Traceability is an ability to follow the movement of a feed or food through specified stages of production, processing and distribution. The process of traceability is managing by people, which implies a human factor. Automation will allow, in a greater extent, to exclude the human factor that will mean decreasing of errors in documentation and will speed up the process of grain transshipment. Research work on the process was carried out on the most modern grain terminal - LLC “UkrTransAgro”. The terminal is located in the Ukrainian water area of the Azov Sea (Mariupol, Ukraine. Characteristics of the terminal: capacity of a simultaneous storage - 48,120 thousand tons, acceptance of crops from transport - 4,500 tons / day; acceptance of crops from railway transport - 3000 tons / day, transshipment capacity - up to 1.2 million tons per year, shipment to the sea vessels - 7000 tons / day. The analysis of the automation level of the grain terminal is carried out. The company uses software from 1C - «1C: Enterprise 8. Accounting for grain elevator, mill, and feed mill for Ukraine». This software is used for quantitative and qualitative registration at the elevator in accordance with industry guidelines and standards. The software product has many

  8. Effect of Strain Restored Energy on Abnormal Grain Growth in Mg Alloy Simulated by Phase Field Methods

    Science.gov (United States)

    Wu, Yan; Huang, Yuan-yuan

    2018-03-01

    Abnormal grain growth of single phase AZ31 Mg alloy in the spatio-temporal process has been simulated by phase field models, and the influencing factors of abnormal grain growth are studied in order to find the ways to control secondary recrystallization in the microstructure. The study aims to find out the mechanisms for abnormal grain growth in real alloys. It is shown from the simulated results that the abnormal grain growth can be controlled by the strain restored energy. Secondary recrystallization after an annealing treatment can be induced if there are grains of a certain orientation in the microstructure with local high restored energy. However, if the value of the local restored energy at a certain grain orientation is not greater than 1.1E 0, there may be no abnormal grain growth in the microstructure.

  9. A grain boundary sliding model for cavitation, crack growth and ...

    African Journals Online (AJOL)

    A model is presented for cavity growth, crack propagation and fracture resulting from grain boundary sliding (GBS) during high temperature creep deformation. The theory of cavity growth by GBS was based on energy balance criteria on the assumption that the matrix is sufficiently plastic to accommodate misfit strains ...

  10. Grain growth of metal uranium; Rast zrna kod metalnog urana

    Energy Technology Data Exchange (ETDEWEB)

    Cerovic, D [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-11-15

    In order to study the grain growth, uranium samples were deformed by molding up to 50% and then by rolling at 600 deg C for recrystallization. Grains obtained by recrystallization having diameter 10 - 15 {mu} were heated at different temperatures and during different time intervals to record the changes of grain size. Characteristic grain growth values, rate constants, time exponent and activation energy, were calculated by using the obtained data. U cilju proucavanja rasta zrna uzorci urana deformisani su valjanjem do 50%, a zatim zareni na 600 deg C da rekristalisu. Rekristalizacijom su dobijena sitna zrna, precnika 10-15 {mu} koja su zatim podvrgavana zarenju pri raznim temperaturama i razlicitm vremenskim intervalima, pri cemu je pracena promena velicine zrna. Na osnovu dobijenih podataka izracunate su karakteristicne velicine rasta zrna: konstante brzine, vremenski eksponent i energija aktivacije (author)

  11. Kinetics of Grain Growth in 718 Ni-Base Superalloy

    Directory of Open Access Journals (Sweden)

    Huda Z.

    2014-10-01

    Full Text Available The Haynes® 718 Ni-base superalloy has been investigated by use of modern material characterization, metallographic and heat treatment equipment. Grain growth annealing experiments at temperatures in the range of 1050 – 1200 oC (1323–1473K for time durations in the range of 20 min-22h have been conducted. The kinetic equations and an Arrhenius-type equation have been applied to compute the grain-growth exponent n and the activation energy for grain growth, Qg, for the investigated alloy. The grain growth exponent, n, was computed to be in the range of 0.066-0.206; and the n values have been critically discussed in relation to the literature. The activation energy for grain growth, Qg, for the investigated alloy has been computed to be around 440 kJ/mol; and the Qg data for the investigated alloy has been compared with other metals and alloys and ceramics; and critically analyzed in relation to our results.

  12. Understanding and Tailoring Grain Growth of Lead-Halide Perovskite for Solar Cell Application.

    Science.gov (United States)

    Ma, Yongchao; Liu, Yanliang; Shin, Insoo; Hwang, In-Wook; Jung, Yun Kyung; Jeong, Jung Hyun; Park, Sung Heum; Kim, Kwang Ho

    2017-10-04

    The fundamental mechanism of grain growth evolution in the fabrication process from the precursor phase to the perovskite phase is not fully understood despite its importance in achieving high-quality grains in organic-inorganic hybrid perovskites, which are strongly affected by processing parameters. In this work, we investigate the fundamental conversion mechanism from the precursor phase of perovskite to the complete perovskite phase and how the intermediate phase promotes growth of the perovskite grains during the fabrication process. By monitoring the morphological evolution of the perovskite during the film fabrication process, we observed a clear rod-shaped intermediate phase in the highly crystalline perovskite and investigated the role of the nanorod intermediate phase on the growth of the grains of the perovskite film. Furthermore, on the basis of these findings, we developed a simple and effective method to tailor grain properties including the crystallinity, size, and number of grain boundaries, and then utilized the film with the tailored grains to develop perovskite solar cells.

  13. Grain growth in uranium nitride prepared by spark plasma sintering

    Science.gov (United States)

    Johnson, Kyle D.; Lopes, Denise Adorno

    2018-05-01

    Uranium mononitride (UN) has long been considered a potential high density, high performance fuel candidate for light water reactor (LWR) and fast reactor (FR) applications. However, deployability of this fuel has been limited by the notable resistance to sintering and subsequent difficulty in producing a desirable microstructure, the high costs associated with 15N enrichment, as well as the known proclivity to oxidation and interaction with steam. In this study, the stimulation of grain growth in UN pellets sintered using SPS has been investigated. The results reveal that by using SPS and controlling temperature, time, and holding pressure, grain growth can be stimulated and controlled to produce a material featuring both a desired porosity and grain size, at least within the range of interest for nuclear fuel candidates. Grain sizes up to 31 μm were obtained using temperatures of 1650 °C and hold times of 15 min. Evaluation by EBSD reveal grain rotation and coalescence as the dominant mechanism in grain growth, which is suppressed by the application of higher external pressure. Moreover, complete closure of the porosity of the material was observed at relative densities of 96% TD, resulting in a material with sufficient porosity to accommodate LWR burnup. These results indicate that a method exists for the economic fabrication of an 15N-bearing uranium mononitride fuel with favorable microstructural characteristics compatible with use in a light water-cooled nuclear reactor.

  14. Yttria-Ceria stabilized tetragonal zirconia polycrystals: Sintering, grain growth and grain boundary segregation

    NARCIS (Netherlands)

    Boutz, M.M.R.; Boutz, M.M.R.; Winnubst, Aloysius J.A.; Burggraaf, Anthonie; Burggraaf, A.J.

    1994-01-01

    An analysis is presented of grain growth and densification of yttria-ceria stabilized tetragonal zirconia polycrystals (Y, Ce-TZPs) using both isothermal and non-isothermal techniques. The characteristics of Y, Ce-TZPs are compared to those of Y-TZP and Ce-TZP and the effect of increasing ceria

  15. Competitive grain growth in directional solidification investigated by phase field simulation

    International Nuclear Information System (INIS)

    Li Junjie; Wang Zhijun; Wang Jincheng; Yang Yujuan

    2012-01-01

    During directional solidification, the competitive dendritic growth between various oriented grains is a key factor to obtain desirable texture. In order to understand the mechanism of competitive dendritic growth, the phase field method was adopted to simulate the microstructure evolution of bicrystal samples. The simulation has well reproduced the whole competitive growth process for both diverging and converging dendrites. In converging case, besides the block of the unfavorably oriented dendrite by the favorably oriented one, the unfavorably oriented dendrite is also able to overgrow the favorable one under the condition of relatively low pulling velocity. This unusual overgrowth is dictated by the solute interaction of the converging dendrite tips. In diverging case, it was found that the grain boundary can be either inclined or parallel to the favorably oriented grain depending on the disposition of two grains.

  16. Giant secondary grain growth in Cu films on sapphire

    Directory of Open Access Journals (Sweden)

    David L. Miller

    2013-08-01

    Full Text Available Single crystal metal films on insulating substrates are attractive for microelectronics and other applications, but they are difficult to achieve on macroscopic length scales. The conventional approach to obtaining such films is epitaxial growth at high temperature using slow deposition in ultrahigh vacuum conditions. Here we describe a different approach that is both simpler to implement and produces superior results: sputter deposition at modest temperatures followed by annealing to induce secondary grain growth. We show that polycrystalline as-deposited Cu on α-Al2O3(0001 can be transformed into Cu(111 with centimeter-sized grains. Employing optical microscopy, x-ray diffraction, and electron backscatter diffraction to characterize the films before and after annealing, we find a particular as-deposited grain structure that promotes the growth of giant grains upon annealing. To demonstrate one potential application of such films, we grow graphene by chemical vapor deposition on wafers of annealed Cu and obtain epitaxial graphene grains of 0.2 mm diameter.

  17. Grain growth kinetics in uranium-plutonium mixed oxides

    International Nuclear Information System (INIS)

    Sari, C.

    1986-01-01

    Grain growth rates were investigated in uranium-plutonium mixed oxide specimens with oxygen-to-metal ratios 1.97 and 2.0. The specimens in the form of cylindrical pellets were heated in a temperature gradient similar to that existing in a fast reactor. The results are in agreement with the cubic rate law. The mean grain size D(μm) after annealing for time t (min) is represented by D 3 -D 0 3 =1.11x10 12 . exp(-445870/RT).t and D 3 -D 0 3 =2.55x10 9 .exp(-319240/RT).t for specimens with overall oxygen-to-metal ratios 1.97 and 2.0, respectively (activation energies expressed in J/mol). An example for the influence of the oxygen-to-metal ratio on the grain growth in mixed oxide fuel during operation in a fast reactor is also given. (orig.)

  18. Grain boundary cavity growth under applied stress and internal pressure

    International Nuclear Information System (INIS)

    Mancuso, J.F.

    1977-08-01

    The growth of grain boundary cavities under applied stress and internal gas pressure was investigated. Methane gas filled cavities were produced by the C + 4H reversible CH4 reaction in the grain boundaries of type 270 nickel by hydrogen charging in an autoclave at 500 0 C with a hydrogen pressure of either 3.4 or 14.5 MPa. Intergranular fracture of nickel was achieved at a charging temperature of 300 0 C and 10.3 MPa hydrogen pressure. Cavities on the grain boundaries were observed in the scanning electron microscope after fracture. Photomicrographs of the cavities were produced in stereo pairs which were analyzed so as to correct for perspective distortion and also to determine the orientational dependence of cavity growth under an applied tensile stress

  19. Growth, assimilate partitioning and grain yield response of soybean ...

    African Journals Online (AJOL)

    This investigation tested variation in the growth components, assimilate partitioning and grain yield of soybean (Glycine max L. Merrrill) varieties established in CO2 enriched atmosphere when inoculated with mixtures of Arbuscular mycorrhizal fungi (AMF) species in the humid rainforest of Nigeria. A pot and a field ...

  20. Nanoscale grain growth behaviour of CoAl intermetallic synthesized ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Grain growth behaviour of the nanocrystalline CoAl intermetallic compound synthesized by mechanical alloying has been studied by isothermal annealing at different temperatures and durations. X-ray diffraction method was employed to investigate structural evolutions during mechanical alloying and anneal-.

  1. Abnormal growth of faceted (WC) grains in a (Co) liquid matrix

    International Nuclear Information System (INIS)

    Park, Y.J.; Yoon, D.Y.

    1996-01-01

    If the grains dispersed in a liquid matrix are spherical, their surface atomic structure is expected to be rough (diffuse), and their coarsening has been observed to be controlled by diffusion in the matrix. They do not, furthermore, undergo abnormal growth. On the other hand, in some compound material systems, the grains in liquid matrices are faceted and often show abnormal coarsening behavior. Their faceted surface planes are expected to be singular (atomically flat) and therefore grow by a defect-assisted process and two-dimensional (2-D) nucleation. Contrary to the usual coarsening theories, their growth velocity is not linearly dependent on the driving force arising from the grain size difference. If the growth of the faceted grains occurs by 2-D nucleation, the rate is expected to increase abruptly at a critical supersaturation, as has been observed in crystal growth in melts and solutions. It is proposed that this growth mechanism leads to the abnormal grain coarsening. The 2-D nucleation theory predicts that there is a threshold initial grain size for the abnormal grain growth (AGG), and the propensity for AGG will increase with the heat-treatment temperature. The AGG behavior will also vary with the defects in the grains. These predictions are qualitatively confirmed in the sintered WC-Co alloy prepared from fine (0.85-microm) and coarse (5.48-microm) WC powders and their mixtures. The observed dependence of the AGG behavior on the sintering temperature and the milling of the WC powder is also qualitatively consistent with the predicted behavior

  2. Evolution of the Annealing Twin Density during δ-Supersolvus Grain Growth in the Nickel-Based Superalloy Inconel™ 718

    Directory of Open Access Journals (Sweden)

    Yuan Jin

    2015-12-01

    Full Text Available Grain growth experiments were performed on Inconel™ 718 to investigate the possible correlation of the annealing twin density with grain size and with annealing temperature. Those experiments were conducted at different temperatures in the δ supersolvus domain and under such conditions that only capillarity forces were involved in the grain boundary migration process. In the investigated range, there is a strong inverse correlation of the twin density with the average grain size. On the other hand, the twin density at a given average grain size is not sensitive to annealing temperature. Consistent with previous results for pure nickel, the twin density evolution in Inconel™ 718 is likely to be mainly controlled by the propagation of the pre-existing twins of the growing grains; i.e., the largest ones of the initial microstructure. Almost no new twin boundaries are created during the grain growth process itself. Therefore, the twin density at a given average grain size is mainly dependent on the twin density in the largest grains of the initial microstructure and independent of the temperature at which grains grow. Based on the observations, a mean field model is proposed to predict annealing twin density as a function of grain size during grain growth.

  3. Analysis of controlled-mechanism of grain growth in undercooled Fe-Cu alloy

    International Nuclear Information System (INIS)

    Chen Zheng; Liu Feng; Yang Xiaoqin; Shen Chengjin; Fan Yu

    2011-01-01

    Highlights: → In terms of a thermo-kinetic model applicable for micro-scale undercooled Fe-4 at.% Cu alloy, grain growth behavior of the single-phase supersaturated granular grain was investigated. → In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, two characteristic annealing time were determined. → The controlled-mechanism of grain growth in undercooled Fe-Cu alloy was proposed, including a mainly kinetic-controlled process, a transition from kinetic-mechanism to thermodynamic-mechanism and purely thermodynamic-controlled process. - Abstract: An analysis of controlled-mechanism of grain growth in the undercooled Fe-4 at.% Cu immiscible alloy was presented. Grain growth behavior of the single-phase supersaturated granular grains prepared in Fe-Cu immiscible alloy melt was investigated by performing isothermal annealings at 500-800 deg. C. The thermo-kinetic model [Chen et al., Acta Mater. 57 (2009) 1466] applicable for nano-scale materials was extended to the system of micro-scale undercooled Fe-4 at.% Cu alloy. In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, two characteristic annealing time (t 1 and t 2 ) were determined. The controlled-mechanism of grain growth in undercooled Fe-Cu alloy was proposed, including a mainly kinetic-controlled process (t ≤ t 1 ), a transition from kinetic-mechanism to thermodynamic-mechanism (t 1 2 ) and purely thermodynamic-controlled process (t ≥ t 2 ).

  4. Morphology and grain structure evolution during epitaxial growth of Ag films on native-oxide-covered Si surface

    International Nuclear Information System (INIS)

    Hur, Tae-Bong; Kim, Hong Koo; Perello, David; Yun, Minhee; Kulovits, Andreas; Wiezorek, Joerg

    2008-01-01

    Epitaxial nanocrystalline Ag films were grown on initially native-oxide-covered Si(001) substrates using radio-frequency magnetron sputtering. Mechanisms of grain growth and morphology evolution were investigated. An epitaxially oriented Ag layer (∼5 nm thick) formed on the oxide-desorbed Si surface during the initial growth phase. After a period of growth instability, characterized as kinetic roughening, grain growth stagnation, and increase of step-edge density, a layer of nanocrystalline Ag grains with a uniform size distribution appeared on the quasi-two-dimensional layer. This hierarchical process of film formation is attributed to the dynamic interplay between incoming energetic Ag particles and native oxide. The cyclic interaction (desorption and migration) of the oxide with the growing Ag film is found to play a crucial role in the characteristic evolution of grain growth and morphology change involving an interval of grain growth stagnation

  5. Grain size refinement of inconel 718 thermomechanical processing

    International Nuclear Information System (INIS)

    Okimoto, P.C.

    1988-01-01

    Inconel 718 is a Ni-Fe precipitation treated superalloy. It presents good thermal fatigue properties when the material has small grain size. The aim of this work is to study the grain size refinement by thermomechanical processing, through observations of the microstructural evolution and the influence of some of the process variables in the final grain size. The results have shown that this refinement occured by static recrystallization. The presence of precipitates have influenced the final grain size if the deformations are below 60%. For greater deformations the grain size is independent of the precipitate distribution in the matrix and tends to a limit size of 5 μm. (author)

  6. Constitutive modeling of stress-driven grain growth in nanocrystalline metals

    KAUST Repository

    Gürses, Ercan

    2013-02-08

    In this work, we present a variational multiscale model for grain growth in face-centered cubic nanocrystalline (nc) metals. In particular, grain-growth-induced stress softening and the resulting relaxation phenomena are addressed. The behavior of the polycrystal is described by a conventional Taylor-type averaging scheme in which the grains are treated as two-phase composites consisting of a grain interior phase and a grain boundary-affected zone. Furthermore, a grain-growth law that captures the experimentally observed characteristics of the grain coarsening phenomena is proposed. To this end, the grain size is not taken as constant and varies according to the proposed stress-driven growth law. Several parametric studies are conducted to emphasize the influence of the grain-growth rule on the overall macroscopic response. Finally, the model is shown to provide a good description of the experimentally observed grain-growth-induced relaxation in nc-copper. © 2013 IOP Publishing Ltd.

  7. Densification and Grain Growth in Polycrystalline Olivine Rocks Synthesized By Evacuated Hot-Pressing

    Science.gov (United States)

    Meyers, C. D.; Kohlstedt, D. L.; Zimmerman, M. E.

    2017-12-01

    Experiments on laboratory-synthesized olivine-rich rocks form the starting material for many investigations of physical processes in the Earth's upper mantle (e.g., creep behavior, ionic diffusion, and grain growth). Typically, a fit of a constitutive law to experimental data provides a description of the kinetics of a process needed to extrapolate across several orders of magnitude from laboratory to geological timescales. Although grain-size is a critical parameter in determining physical properties such as viscosity, broad disagreement persists amongst the results of various studies of grain growth kinetics in olivine-rich rocks. Small amounts of impurities or porosity dramatically affect the kinetics of grain growth. In this study, we developed an improved method for densifying olivine-rich rocks fabricated from powdered, gem-quality single crystals that involves evacuating the pore space, with the aim of refining measurements of the kinetics of mantle materials. In previous studies, olivine powders were sealed in a metal can and hydrostatically annealed at roughly 300 MPa and 1250 °C. These samples, which appear opaque and milky-green, typically retain a small amount of porosity. Consequently, when annealed at 1 atm, extensive pore growth occurs, inhibiting grain growth. In addition, Fourier-transform infrared and confocal Raman spectroscopy reveal absorption peaks characteristic of CO2 in the pores of conventionally hot-pressed material. To avoid trapping of adsorbed contaminants, we developed an evacuated hot-pressing method, wherein the pore space of powder compacts is vented to vacuum during heating and pressurization. This method produces a highly dense, green-tinted, transparent material. No CO2 absorptions peaks exist in evacuated hot-pressed material. When reheated to annealing temperatures at 1 atm, the evacuated hot-pressed material undergoes limited pore growth and dramatically enhanced grain-growth rates. High-strain deformation experiments on

  8. The water kefir grain inoculum determines the characteristics of the resulting water kefir fermentation process.

    Science.gov (United States)

    Laureys, D; De Vuyst, L

    2017-03-01

    To investigate the influence of the water kefir grain inoculum on the characteristics of the water kefir fermentation process. Three water kefir fermentation processes were started with different water kefir grain inocula and followed as a function of time regarding microbial species diversity, community dynamics, substrate consumption profile and metabolite production course. The inoculum determined the water kefir grain growth, the viable counts on the grains, the time until total carbohydrate exhaustion, the final metabolite concentrations and the microbial species diversity. There were always 2-10 lactic acid bacterial cells for every yeast cell and the majority of these micro-organisms was always present on the grains. Lactobacillus paracasei, Lactobacillus hilgardii, Lactobacillus nagelii and Saccharomyces cerevisiae were always present and may be the key micro-organisms during water kefir fermentation. Low water kefir grain growth was associated with small grains with high viable counts of micro-organisms, fast fermentation and low pH values, and was not caused by the absence of exopolysaccharide-producing lactic acid bacteria. The water kefir grain inoculum influences the microbial species diversity and characteristics of the fermentation process. A select group of key micro-organisms was always present during fermentation. This study allows a rational selection of a water kefir grain inoculum. © 2016 The Society for Applied Microbiology.

  9. Influence of Different Growth Conditions on the Kefir Grains Production, used in the Kefiran Synthesis

    Directory of Open Access Journals (Sweden)

    Carmen Rodica Pop

    2014-11-01

    Full Text Available The purpose of this study was to optimize the kefir grains biomass production, using milk as culture media. The kefir grains were cultured at different changed conditions (temperature, time, shaker rotating speed, culture media supplemented to evaluate their effects. Results showed that optimal culture conditions were using the organic skim milk, incubated at 25°C for 24 hours with a rotation rate of 125 rpm. According to results, the growth rate was 38.9 g/L for 24 h, at 25°C using the organic milk - OSM, 36.87 g/L during 24 hours, optimal time for propagation process gave 37.93 g/L kefir grains biomass when the effect of temperature level was tested. The homogenization of medium with shaker rotating induced a greater growth rate, it was obtained 38.9 g/L for 24 h, at 25°C using rotation rate at 125 rpm. The growing medium (conventional milk supplemented with different minerals and vitamins may lead to improve the growth conditions of kefir grains biomass. The optimization of the growth environment is very important for achieving the maximum production of kefir grains biomass, substrate necessary to obtain the polysaccharide kefiran

  10. New Process for Grain Refinement of Aluminum. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Joseph A. Megy

    2000-09-22

    A new method of grain refining aluminum involving in-situ formation of boride nuclei in molten aluminum just prior to casting has been developed in the subject DOE program over the last thirty months by a team consisting of JDC, Inc., Alcoa Technical Center, GRAS, Inc., Touchstone Labs, and GKS Engineering Services. The Manufacturing process to make boron trichloride for grain refining is much simpler than preparing conventional grain refiners, with attendant environmental, capital, and energy savings. The manufacture of boride grain refining nuclei using the fy-Gem process avoids clusters, salt and oxide inclusions that cause quality problems in aluminum today.

  11. Processing and properties of large grain (RE)BCO

    International Nuclear Information System (INIS)

    Cardwell, D.A.

    1998-01-01

    The potential of high temperature superconductors to generate large magnetic fields and to carry current with low power dissipation at 77 K is particularly attractive for a variety of permanent magnet applications. As a result large grain bulk (RE)-Ba-Cu-O ((RE)BCO) materials have been developed by melt process techniques in an attempt to fabricate practical materials for use in high field devices. This review outlines the current state of the art in this field of processing, including seeding requirements for the controlled fabrication of these materials, the origin of striking growth features such as the formation of a facet plane around the seed, platelet boundaries and (RE) 2 BaCuO 5 (RE-211) inclusions in the seeded melt grown microstructure. An observed variation in critical current density in large grain (RE)BCO samples is accounted for by Sm contamination of the material in the vicinity of the seed and with the development of a non-uniform growth morphology at ∼4 mm from the seed position. (RE)Ba 2 Cu 3 O 7-δ (RE-123) dendrites are observed to form and bro[en preferentially within the a/b plane of the lattice in this growth regime. Finally, trapped fields in excess of 3 T have been reported in irr[iated U-doped YBCO and (RE) 1+x Ba 2-x Cu 3 O y (RE=Sm, Nd) materials have been observed to carry transport current in fields of up to 10 T at 77 K. This underlines the potential of bulk (RE)BCO materials for practical permanent magnet type applications. (orig.)

  12. Ultra-large single crystals by abnormal grain growth.

    Science.gov (United States)

    Kusama, Tomoe; Omori, Toshihiro; Saito, Takashi; Kise, Sumio; Tanaka, Toyonobu; Araki, Yoshikazu; Kainuma, Ryosuke

    2017-08-25

    Producing a single crystal is expensive because of low mass productivity. Therefore, many metallic materials are being used in polycrystalline form, even though material properties are superior in a single crystal. Here we show that an extraordinarily large Cu-Al-Mn single crystal can be obtained by abnormal grain growth (AGG) induced by simple heat treatment with high mass productivity. In AGG, the sub-boundary energy introduced by cyclic heat treatment (CHT) is dominant in the driving pressure, and the grain boundary migration rate is accelerated by repeating the low-temperature CHT due to the increase of the sub-boundary energy. With such treatment, fabrication of single crystal bars 70 cm in length is achieved. This result ensures that the range of applications of shape memory alloys will spread beyond small-sized devices to large-scale components and may enable new applications of single crystals in other metallic and ceramics materials having similar microstructural features.Growing large single crystals cheaply and reliably for structural applications remains challenging. Here, the authors combine accelerated abnormal grain growth and cyclic heat treatments to grow a superelastic shape memory alloy single crystal to 70 cm.

  13. A parallelized three-dimensional cellular automaton model for grain growth during additive manufacturing

    Science.gov (United States)

    Lian, Yanping; Lin, Stephen; Yan, Wentao; Liu, Wing Kam; Wagner, Gregory J.

    2018-01-01

    In this paper, a parallelized 3D cellular automaton computational model is developed to predict grain morphology for solidification of metal during the additive manufacturing process. Solidification phenomena are characterized by highly localized events, such as the nucleation and growth of multiple grains. As a result, parallelization requires careful treatment of load balancing between processors as well as interprocess communication in order to maintain a high parallel efficiency. We give a detailed summary of the formulation of the model, as well as a description of the communication strategies implemented to ensure parallel efficiency. Scaling tests on a representative problem with about half a billion cells demonstrate parallel efficiency of more than 80% on 8 processors and around 50% on 64; loss of efficiency is attributable to load imbalance due to near-surface grain nucleation in this test problem. The model is further demonstrated through an additive manufacturing simulation with resulting grain structures showing reasonable agreement with those observed in experiments.

  14. A parallelized three-dimensional cellular automaton model for grain growth during additive manufacturing

    Science.gov (United States)

    Lian, Yanping; Lin, Stephen; Yan, Wentao; Liu, Wing Kam; Wagner, Gregory J.

    2018-05-01

    In this paper, a parallelized 3D cellular automaton computational model is developed to predict grain morphology for solidification of metal during the additive manufacturing process. Solidification phenomena are characterized by highly localized events, such as the nucleation and growth of multiple grains. As a result, parallelization requires careful treatment of load balancing between processors as well as interprocess communication in order to maintain a high parallel efficiency. We give a detailed summary of the formulation of the model, as well as a description of the communication strategies implemented to ensure parallel efficiency. Scaling tests on a representative problem with about half a billion cells demonstrate parallel efficiency of more than 80% on 8 processors and around 50% on 64; loss of efficiency is attributable to load imbalance due to near-surface grain nucleation in this test problem. The model is further demonstrated through an additive manufacturing simulation with resulting grain structures showing reasonable agreement with those observed in experiments.

  15. The diffusional growth of a grain boundary crack

    International Nuclear Information System (INIS)

    Puls, M.P.; Dutton, R.

    1977-10-01

    This report considers the possibility of high temperature rupture occurring by a grain boundary diffusional mechanism. It is assumed that a pre-existing, intergranular crack grows by loss of atoms from the crack tip to the grain boundary. Rupture occurs when the crack has grown to a critical length. A theoretical treatment of the kinetics of crack growth is presented and equations are derived for the crack velocity and time to rupture. A comparison is made with a previous theoretical model developed by Charles, together with rupture data obtained experimentally for the nickel-based alloy, Nimonic 80A. We conclude that experimental verification of the theoretical models requires a comparison with crack velocity data rather than time to rupture data. (author)

  16. Grain Growth and Precipitation Behavior of Iridium Alloy DOP-26 During Long Term Aging

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Dean T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Muralidharan, Govindarajan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fox, Ethan E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cox, Victoria A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Geer, Tom [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-01

    The influence of long term aging on grain growth and precipitate sizes and spatial distribution in iridium alloy DOP-26 was studied. Samples of DOP-26 were fabricated using the new process, recrystallized for 1 hour (h) at 1375 C, then aged at either 1300, 1400, or 1500 C for times ranging from 50 to 10,000 h. Grain size measurements (vertical and horizontal mean linear intercept and horizontal and vertical projection) and analyses of iridium-thorium precipitates (size and spacing) were made on the longitudinal, transverse, and rolling surfaces of the as-recrystallized and aged specimens from which the two-dimensional spatial distribution and mean sizes of the precipitates were obtained. The results obtained from this study are intended to provide input to grain growth models.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-08-01

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

  19. Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

    Science.gov (United States)

    Kim, Jeong Min; Min, Guensik; Shim, Jae-Hyeok; Lee, Kyung Jong

    2018-05-01

    The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.

  20. Normal and abnormal grain growth in fine-grained Nd-Fe-B sintered magnets prepared from He jet milled powders

    Energy Technology Data Exchange (ETDEWEB)

    Bittner, F., E-mail: f.bittner@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Technische Universität Dresden, Institute of Materials Science, 01062 Dresden (Germany); Woodcock, T.G. [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Schultz, L. [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Technische Universität Dresden, Institute of Materials Science, 01062 Dresden (Germany); Schwöbel, C. [Technische Universität Darmstadt, Materialwissenschaft, Alarich-Weiß-Str. 16, 64287 Darmstadt (Germany); Gutfleisch, O. [Technische Universität Darmstadt, Materialwissenschaft, Alarich-Weiß-Str. 16, 64287 Darmstadt (Germany); Fraunhofer ISC, Projektgruppe für Werkstoffkreisläufe und Ressourcenstrategie IWKS, Rodenbacher Chaussee 4, 63457 Hanau (Germany); Zickler, G.A.; Fidler, J. [Technische Universität Wien, Institute of Solid State Physics, Wiedner Hauptstr. 8-10, 1040 Wien (Austria); Üstüner, K.; Katter, M. [Vacuumschmelze GmbH & Co. KG, 63412 Hanau (Germany)

    2017-03-15

    Fine-grained, heavy rare earth free Nd-Fe-B sintered magnets were prepared from He jet milled powders with an average particle size of 1.5 µm by low temperature sintering at 920 °C or 980 °C. A coercivity of >1600 kA/m was achieved for an average grain size of 1.68 µm. Transmission electron microscopy showed that the distribution and composition of intergranular and grain boundary junction phases was similar to that in conventionally processed magnets. Microstructural analysis on different length scales revealed the occurrence of abnormal grain growth, which is unexpected for sintering temperatures below 1000 °C. A larger area fraction of abnormal grains was observed in the sample sintered at 920 °C compared to that sintered at 980 °C. Microtexture investigation showed a better crystallographic alignment of the abnormal grains compared to the fine-grained matrix, which is explained by a size dependent alignment of the powder particles during magnetic field alignment prior to sintering. Slightly larger particles in the initial powder show a better alignment and will act as nucleation sites for abnormal grain growth. Magneto-optical Kerr investigations confirmed the lower switching field of the abnormal grains compared to the fine-grained matrix. The demagnetisation curve of the sample sintered at 920 °C showed reduced rectangularity and this was attributed to a cooperative effect of the larger fraction of abnormal grains with low switching field and, as a minor effect, a reduced degree of crystallographic texture in this sample compared to the material sintered at 980 °C, which did not show the reduced rectangularity of the demagnetisation curve. - Highlights: • He Jet milling to reduce Nd-Fe-B grain size and to enhance coercivity. • Normal and abnormal grain growth observed for low temperature sintering. • Well oriented abnormal grown grains explained by size dependent field alignment. • Poor rectangularity is caused by low nucleation field of

  1. Normal and abnormal grain growth in fine-grained Nd-Fe-B sintered magnets prepared from He jet milled powders

    International Nuclear Information System (INIS)

    Bittner, F.; Woodcock, T.G.; Schultz, L.; Schwöbel, C.; Gutfleisch, O.; Zickler, G.A.; Fidler, J.; Üstüner, K.; Katter, M.

    2017-01-01

    Fine-grained, heavy rare earth free Nd-Fe-B sintered magnets were prepared from He jet milled powders with an average particle size of 1.5 µm by low temperature sintering at 920 °C or 980 °C. A coercivity of >1600 kA/m was achieved for an average grain size of 1.68 µm. Transmission electron microscopy showed that the distribution and composition of intergranular and grain boundary junction phases was similar to that in conventionally processed magnets. Microstructural analysis on different length scales revealed the occurrence of abnormal grain growth, which is unexpected for sintering temperatures below 1000 °C. A larger area fraction of abnormal grains was observed in the sample sintered at 920 °C compared to that sintered at 980 °C. Microtexture investigation showed a better crystallographic alignment of the abnormal grains compared to the fine-grained matrix, which is explained by a size dependent alignment of the powder particles during magnetic field alignment prior to sintering. Slightly larger particles in the initial powder show a better alignment and will act as nucleation sites for abnormal grain growth. Magneto-optical Kerr investigations confirmed the lower switching field of the abnormal grains compared to the fine-grained matrix. The demagnetisation curve of the sample sintered at 920 °C showed reduced rectangularity and this was attributed to a cooperative effect of the larger fraction of abnormal grains with low switching field and, as a minor effect, a reduced degree of crystallographic texture in this sample compared to the material sintered at 980 °C, which did not show the reduced rectangularity of the demagnetisation curve. - Highlights: • He Jet milling to reduce Nd-Fe-B grain size and to enhance coercivity. • Normal and abnormal grain growth observed for low temperature sintering. • Well oriented abnormal grown grains explained by size dependent field alignment. • Poor rectangularity is caused by low nucleation field of

  2. The growth mechanism of grain boundary carbide in Alloy 690

    International Nuclear Information System (INIS)

    Li, Hui; Xia, Shuang; Zhou, Bangxin; Peng, Jianchao

    2013-01-01

    The growth mechanism of grain boundary M 23 C 6 carbides in nickel base Alloy 690 after aging at 715 °C was investigated by high resolution transmission electron microscopy. The grain boundary carbides have coherent orientation relationship with only one side of the matrix. The incoherent phase interface between M 23 C 6 and matrix was curved, and did not lie on any specific crystal plane. The M 23 C 6 carbide transforms from the matrix phase directly at the incoherent interface. The flat coherent phase interface generally lies on low index crystal planes, such as (011) and (111) planes. The M 23 C 6 carbide transforms from a transition phase found at curved coherent phase interface. The transition phase has a complex hexagonal crystal structure, and has coherent orientation relationship with matrix and M 23 C 6 : (111) matrix //(0001) transition //(111) carbide , ¯ > matrix // ¯ 10> transition // ¯ > carbide . The crystal lattice constants of transition phase are c transition =√(3)×a matrix and a transition =√(6)/2×a matrix . Based on the experimental results, the growth mechanism of M 23 C 6 and the formation mechanism of transition phase are discussed. - Highlights: • A transition phase was observed at the coherent interfaces of M 23 C 6 and matrix. • The transition phase has hexagonal structure, and is coherent with matrix and M 23 C 6 . • The M 23 C 6 transforms from the matrix directly at the incoherent phase interface

  3. Grain growth in thoria and thoria-base fuel pellets (LWBR development program)

    Energy Technology Data Exchange (ETDEWEB)

    Smid, R.J.

    1976-01-01

    The kinetics of grain growth in ThO/sub 2/-base sintered compacts were investigated to determine the cause of a nonuniform microstructural cross section. It was concluded that trace impurities which inhibit continuous grain growth at the pellet interior were removed by vaporization at the pellet exterior. This resulted in relatively normal grain growth at the pellet surface and discontinuous grain growth at the pellet interior. Calcining the starting ThO/sub 2/ powder to a slightly higher temperature removed inhibiting impurities but also decreased the driving force for grain growth by reducing the surface area of the powder. Mixing high and low temperature calcined ThO/sub 2/ resulted in improved grain growth. Increased oxygen partial pressure and temperature during sintering increased grain boundary mobility in spite of the inhibiting impurity. The specific inhibiting impurity was not isolated during this investigation.

  4. Creep of quartz by dislocation and grain boundary processes

    Science.gov (United States)

    Fukuda, J. I.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    Wet polycrystalline quartz aggregates deformed at temperatures T of 600°-900°C and strain rates of 10-4-10-6 s-1 at a confining pressure Pc of 1.5 GPa exhibit plasticity at low T, governed by dislocation glide and limited recovery, and grain size-sensitive creep at high T, governed by diffusion and sliding at grain boundaries. Quartz aggregates were HIP-synthesized, subjecting natural milky quartz powder to T=900°C and Pc=1.5 GPa, and grain sizes (2 to 25 mm) were varied by annealing at these conditions for up to 10 days. Infrared absorption spectra exhibit a broad OH band at 3400 cm-1 due to molecular water inclusions with a calculated OH content (~4000 ppm, H/106Si) that is unchanged by deformation. Rate-stepping experiments reveal different stress-strain rate functions at different temperatures and grain sizes, which correspond to differing stress-temperature sensitivities. At 600-700°C and grain sizes of 5-10 mm, flow law parameters compare favorably with those for basal plasticity and dislocation creep of wet quartzites (effective stress exponents n of 3 to 6 and activation enthalpy H* ~150 kJ/mol). Deformed samples show undulatory extinction, limited recrystallization, and c-axis maxima parallel to the shortening direction. Similarly fine-grained samples deformed at 800°-900°C exhibit flow parameters n=1.3-2.0 and H*=135-200 kJ/mol corresponding to grain size-sensitive Newtonian creep. Deformed samples show some undulatory extinction and grain sizes change by recrystallization; however, grain boundary deformation processes are indicated by the low value of n. Our experimental results for grain size-sensitive creep can be compared with models of grain boundary diffusion and grain boundary sliding using measured rates of silicon grain boundary diffusion. While many quartz mylonites show microstructural and textural evidence for dislocation creep, results for grain size-sensitive creep may apply to very fine-grained (<10 mm) quartz mylonites.

  5. Grain refinement through severe plastic deformation (SPD) processing

    International Nuclear Information System (INIS)

    Izairi, N.; Vevecka - Priftaj, A.

    2012-01-01

    There is considerable current interest in processing metallic samples through procedures involving the imposition of severe plastic deformation (SPD). These procedures lead to very significant grain refinement to the submicrometer or even the nanometer level, resulting in advanced physical properties. Among various SPD processes, Equal Channel Angular Pressing, High pressure Torsion and Accumulated Roll Bonding have been widely used for many metals and alloys. In the present work, we present an overview of the most used methods of SPD for grain refinement and the production of bulk nano structured materials with enhancement in their mechanical and functional properties. In order to examine the potential for using ECAP to refine the grain size and improve the mechanical properties, two commercial 5754 Al alloy and AA 3004 , were selected for study. Processing by ECAP gives a reduction in the grain size and an increase in the microhardness. (Author)

  6. Growth modes of individual ferrite grains in the austenite to ferrite transformation of low carbon steels

    International Nuclear Information System (INIS)

    Li, D.Z.; Xiao, N.M.; Lan, Y.J.; Zheng, C.W.; Li, Y.Y.

    2007-01-01

    The mesoscale deterministic cellular automaton (CA) method and probabilistic Q-state Potts-based Monte Carlo (MC) model have been adopted to investigate independently the individual growth behavior of ferrite grain during the austenite (γ)-ferrite (α) transformation. In these models, the γ-α phase transformation and ferrite grain coarsening induced by α/α grain boundary migration could be simulated simultaneously. The simulations demonstrated that both the hard impingement (ferrite grain coarsening) and the soft impingement (overlapping carbon concentration field) have a great influence on the individual ferrite growth behavior. Generally, ferrite grains displayed six modes of growth behavior: parabolic growth, delayed nucleation and growth, temporary shrinkage, partial shrinkage, complete shrinkage and accelerated growth in the transformation. Some modes have been observed before by the synchrotron X-ray diffraction experiment. The mesoscopic simulation provides an alternative tool for investigating both the individual grain growth behavior and the overall transformation behavior simultaneously during transformation

  7. Flotation process diagnostics and modelling by coal grain analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ofori, P; O' Brien, G.; Firth, B.; Jenkins, B. [CSIRO Energy Technology, Brisbane, Qld. (Australia)

    2006-05-15

    In coal flotation, particles of different components of the coal such as maceral groups and mineral matter and their associations have different hydrophobicities and therefore different flotation responses. By using a new coal grain analysis method for characterising individual grains, more detailed flotation performance analysis and modelling approaches have been developed. The method involves the use of microscopic imaging techniques to obtain estimates of size, compositional and density information on individual grains of fine coal. The density and composition partitioning of coal processed through different flotation systems provides an avenue to pinpoint the actual cause of poor process performance so that corrective action may be initiated. The information on grain size, density and composition is being used as input data to develop more detailed flotation process models to provide better predictions of process performance for both mechanical and column flotation devices. A number of approaches may be taken to flotation modelling such as the probability approach and the kinetic model approach or a combination of the two. In the work reported here, a simple probability approach has been taken, which will be further refined in due course. The use of grain data to map the responses of different types of coal grains through various fine coal cleaning processes provided a more advanced diagnostic capability for fine coal cleaning circuits. This enabled flotation performance curves analogous to partition curves for density separators to be produced for flotation devices.

  8. Grain growth: The key to understand solid-state dewetting of silver thin films

    International Nuclear Information System (INIS)

    Jacquet, P.; Podor, R.; Ravaux, J.; Teisseire, J.; Gozhyk, I.; Jupille, J.; Lazzari, R.

    2016-01-01

    The dynamics of solid-state dewetting of polycrystalline silver thin films in oxygen atmosphere was investigated with in situ and real-time environmental Scanning Electron Microscopy at high temperature combined with Atomic Force Microscopy. Three steps were identified during dewetting: induction, hole propagation without specific rim and sintering. Moreover, it was observed that a very selective grain growth, promoted by surface diffusion, plays a key role all along the process.

  9. Limit of grain refinement during ECAP process. Temperature influence

    International Nuclear Information System (INIS)

    Chuvil'deev, V.N.; Kopylov, V.I.; Nokhrin, A.V.; Makarov, I.M.; Lopatin, Yu.G.

    2004-01-01

    Experimental and theoretical study results are reported for the process of deformation grain refinement under severe plastic deformation. A generalization is made for experimental study results on deformation dispersing of unalloyed metals and aluminium and magnesium base alloys. The model is built that allows calculating the value of minimum grain size attained by the method of equal-channel angular pressing. The expressions are derived which describe the dependence of grain refinement limit on the nature of material and the temperature of severe plastic deformation [ru

  10. Grain size of fine-grained windblown sediment: a powerful proxy for process identification

    NARCIS (Netherlands)

    Vandenberghe, J.

    2013-01-01

    Dust transport by the wind is not a uniform process but may occur in different modes according to source area conditions and transport height and distance. Subsequently, these differences are expressed in terms of grain-size and fluxes of the aeolian deposits. Transport distances may vary from

  11. Anomalous grain growth in nanocrystalline Fe73.5Cu1Nb3Su13.5B9 alloys

    DEFF Research Database (Denmark)

    Jiang, Jianzhong

    1997-01-01

    The grain growth of the FeSi phase during the crystallization process of the amorphous Fe73.5Cu1Nb3Si13.5B9 alloy was studied using transmission electron microscopy and x-ray diffractometry. An anomalous grain growth behaviour of the FeSi phase in the samples annealed in temperature range from 743...... to 823 K for one hour was observed, i.e. the grain size of the FeSi phase slightly decreases when the annealing temperature increases from 743 K ot 823 K. The mechanism of the anomalous grain growth may be due to the different nucleation and volume diffusion rates in the samples anneales at low and high...

  12. Irreversible thermodynamics, parabolic law and self-similar state in grain growth

    International Nuclear Information System (INIS)

    Rios, P.R.

    2004-01-01

    The formalism of the thermodynamic theory of irreversible processes is applied to grain growth to investigate the nature of the self-similar state and its corresponding parabolic law. Grain growth does not reach a steady state in the sense that the entropy production remains constant. However, the entropy production can be written as a product of two factors: a scale factor that tends to zero for long times and a scaled entropy production. It is suggested that the parabolic law and the self-similar state may be associated with the minimum of this scaled entropy production. This result implies that the parabolic law and the self-similar state have a sound irreversible thermodynamical basis

  13. Growth order and activation energies for grain growth of Ti-6Al-4V alloy in β phase

    International Nuclear Information System (INIS)

    Gil, F.J.; Planell, J.A.

    1991-01-01

    This paper reports that one of the reasons usually stated for avoiding annealing treatments and hot working of Ti-6Al-4V alloy at temperatures over the β transus is the large grain growth which takes place at such temperatures. The aim of the present work is to quantify the grain growth kinetics when the alloy is heat treated in its β phase. It is well known that the driving force for grain growth comes from the surface energy of the grain boundaries. When thermal energy is given to the material, diffusion takes place which leads to grain selection. This means that the number of grains decreases, their size increases, the area of the grain boundaries decreases with the total energy stored in them and consequently a state of higher thermodynamic stability is reached

  14. Monte carlo simulation of anisotropic grain growth in liquid phase sintering

    International Nuclear Information System (INIS)

    Han, Yoon Soo; Kim, Do Kyung

    2003-01-01

    One of the key techniques in modern engineering ceramic system is microstructural control of anisotropic grain growth because grain orientation and shape proved to have an influence on mechanic, dielectric and electric behavior of ceramics. But until now, computer simulation for grain growth has not sufficiently addressed to this subject. The reason is that simulation algorithm was laborious because it has to contain mass transfer through liquid phase and especially anisotropic grain growth has to be considered based on interfacial properties in real system. The goal of present study is simulation of anisotropic grain growth in liquid phase by Q-states model. To give anisotropic inherency to grains, constraint on mobility to specific boundaries was applied. For comparison, we measured grain size distribution and deduced grain growth kinetics from relation ship between average grain size and time. As a result, the grain size distribution functions become broader and the peak height decreases as the anisotropy is increased. The growth exponent 0.67 and 0.47 found by linear fitting have slightly different values in comparison with work of Grest et al. but similar is trend to the decrease of exponent with anisotropy

  15. The influence of external conditions on the grain storage process

    Directory of Open Access Journals (Sweden)

    O. A. Orlovtseva

    2016-01-01

    Full Text Available .High quality grain - a pledge of his safety, reduce losses and the costs of storage. Wheat is the main source of human nutrition. Elements contained in wheat perform a fundamental role in human life. Storing grain quality is an urgent task. One of the labor-intensive operations in this process is the correct placement of parties in wheat granary and timely monitoring of key parameters (humidity and temperature. In this regard, we consider methods for determining the intensity of the grain breathing method for determining the moisture content and temperature of the grain of wheat. Humidity was determined by electrical hygrometer. To measure the temperature of wheat used mercury thermometer. In analyzing the breathing wheat energy depending on the humidity it was found that the intensity of respiration increasingly affects humidity increase than an increase in temperature. As objects of study used wheat varieties: Hordeiforme 432 and Multiroom 321. According to the results obtained in the study plot the respiratory activity of the grain from moisture. According to the schedules we concluded that the sharp increase in wheat breathing energy occurs with increasing moisture content to a value of more than 15%. Just found out that in addition to breathing in highly humid grain appears vital functions of harmful microorganisms, which under the influence of grain rots and becomes stale. Thus, ho-well-organized and skilled observation, the correct analysis of the obtained data allow to bring the maximum reduction in spending of dry matter and therefore achieve lower grain weight loss during storage.

  16. Determination of Sintered (Th,U)O2 Pellet at the Grain Growth Step

    International Nuclear Information System (INIS)

    Indrati-Y, Tundjung; Pristi-Hartati, Murdani; Ari-Handayani; Ginting, Aslina Br

    2000-01-01

    The determination of sintered (Th,U)O 2 pellet at the grain growth stephave been done by dilatometer and Scanning Electron Microscope (SEM). Thecalculation method based on the densification curve and quantitativemetallurgy. The green pellet be produced by single action compaction. Itspellet was heated on the dilatometer with heating rate 11 o C/minute and inthe argon atmosphere, 2 liters/hour. The activation energy at thedensification step can be calculated by densification curve only, but theactivation energy at the grain growth step can be calculated by densificationcurve or quantitative metallurgy. The capability of the dilatometer can beoperated until 1200 o C, so the densification curve based on the experiencecan be used to calculate activation energy at the densification step, 4.492kcal/mole. The activation energy at the grain growth step, which is 25.277kcal/mole, can be predicted by trial and error on n value. That activationenergy is almost the same with activation energy that based on thequantitative metallurgy method 25.042 kcal/mole. All of the activation energyfor the (Th,U)O 2 pellet sintering process is 29.769 kcal/mole. (author)

  17. On the fission gas release from oxide fuels during normal grain growth

    International Nuclear Information System (INIS)

    Paraschiv, M.C.; Paraschiv, A.; Glodeanu, F.

    1997-01-01

    A mathematical formalism for calculating the fission gas release from oxide fuels considering an arbitrary distribution of fuel grain size with only zero boundary condition for gas diffusion at the grain boundary is proposed. It has also been proved that it becomes unnecessary to consider the grain volume distribution function for fission products diffusion when the grain boundary gas resolution is considered, if thermodynamic forces on grain boundaries are only time dependent. In order to highlight the effect of the normal grain growth on fission gas release from oxide fuels Hillert's and Lifshitz and Slyozov's theories have been selected. The last one was used to give an adequate treatment of normal grain growth for the diffusion-controlled grain boundary movement in oxide fuels. It has been shown that during the fuel irradiation, the asymptotic form of the grain volume distribution functions given by Hillert and Lifshitz and Slyozov models can be maintained but the grain growth rate constant becomes time dependent itself. Experimental results have been used to correlate the two theoretical models of normal grain growth to the fission gas release from oxide fuels. (orig.)

  18. Constitutive modeling of stress-driven grain growth in nanocrystalline metals

    KAUST Repository

    Gü rses, Ercan; Wafai, Husam; El Sayed, Tamer S.

    2013-01-01

    the influence of the grain-growth rule on the overall macroscopic response. Finally, the model is shown to provide a good description of the experimentally observed grain-growth-induced relaxation in nc-copper. © 2013 IOP Publishing Ltd.

  19. Dynamic grain growth in superplastic Y-TZP and Al2O3/YTZ

    International Nuclear Information System (INIS)

    Nieh, T.G.; Tomasello, C.M.; Wadsworth, J.

    1990-01-01

    This paper reports that both static and dynamic grain growth have been studied during superplastic deformation of fine-grained yttria-stabilized tetragonal zirconia (Y-TZP) and alumina reinforced yttria-stabilized tetragonal zirconia (Al 2 O 3 /YTZ). Grain growth was observed in both materials at temperatures above 1350 degrees C. In the case of Y-TZP, both static and dynamic grain growth were found to obey a similar equation of the form: D 3 -D 0 3 = kt where D is the instantaneous grain size, D 0 is the initial grain size, t is the time, and k is a kinetic constant which depends primarily on temperature and grain boundary energy. The activation energies for Y-TZP were approximately 580 and 520 kJ/mol, for static and dynamic grain growth, respectively. In the case of Al 2 O 3 /YTZ, it was found that the grain growth rate for the Al 2 O 3 phase was slower than that for the ZrO 2 phase. The growth rate of the ZrO 2 phase in Al 2 O 3 /YTZ is, however, similar to that in monolithic ZrO 2 i.e., Y-TZP

  20. Processing properties of grains from some maize cultivars ...

    African Journals Online (AJOL)

    For the dry milling, whole or pealed grains were simply processed in a hammer mill and the flour fractions separated as with wet milling. Results indicated some variation in the proximate composition with nine cultivars exhibiting protein contents above 8%. High protein cultivars were in order hybrids 88094X87036, ...

  1. Grain refinement of Aluminium alloys using friction stir processing

    International Nuclear Information System (INIS)

    Khraisheh, M.

    2004-01-01

    Full text.Friction Stir Processing (FSP) is a new advanced material processing technique used to refine and homogenize the microstructure of sheet metals. FSP is a solid state processing technique that uses a rapidly rotating non-consumable high strength tool steel pin that extends from a cylindrical shoulder. The rotating pin is forced with a predetermined load into the work piece and moved along with the work pieces, while the rotating pin deforms and stirs the locally heated material. It is a hot working process in which a large amount of deformation is imparted to the sheet. FS processed zone is characterized by dynamic recrystallization which results in grain refinement . this promising emerging process needs further investigations to develop optimum process parameters to produce the desired microstructure. In this work, we present preliminary results on the effects of rotational and translational speeds on grain refinement of AA5052. Under certain processing conditions, sub-micron grain structure was produced using this technique

  2. Flow processes at low temperatures in ultrafine-grained aluminum

    International Nuclear Information System (INIS)

    Chinh, Nguyen Q.; Szommer, Peter; Csanadi, Tamas; Langdon, Terence G.

    2006-01-01

    Experiments were conducted to evaluate the flow behavior of pure aluminum at low temperatures. Samples were processed by equal-channel angular pressing (ECAP) to give a grain size of ∼1.2 μm and compression samples were cut from the as-pressed billets and tested over a range of strain rates at temperatures up to 473 K. The results show the occurrence of steady-state flow in these highly deformed samples and a detailed analysis gives a low strain rate sensitivity and an activation energy similar to the value for grain boundary diffusion. By using depth-sensing indentation testing and atomic force microscopy, it is shown that grain boundary sliding occurs in this material at low temperatures. This result is attributed to the presence of high-energy non-equilibrium boundaries in the severely deformed samples

  3. Statistical mechanics of normal grain growth in one dimension: A partial integro-differential equation model

    International Nuclear Information System (INIS)

    Ng, Felix S.L.

    2016-01-01

    We develop a statistical-mechanical model of one-dimensional normal grain growth that does not require any drift-velocity parameterization for grain size, such as used in the continuity equation of traditional mean-field theories. The model tracks the population by considering grain sizes in neighbour pairs; the probability of a pair having neighbours of certain sizes is determined by the size-frequency distribution of all pairs. Accordingly, the evolution obeys a partial integro-differential equation (PIDE) over ‘grain size versus neighbour grain size’ space, so that the grain-size distribution is a projection of the PIDE's solution. This model, which is applicable before as well as after statistically self-similar grain growth has been reached, shows that the traditional continuity equation is invalid outside this state. During statistically self-similar growth, the PIDE correctly predicts the coarsening rate, invariant grain-size distribution and spatial grain size correlations observed in direct simulations. The PIDE is then reducible to the standard continuity equation, and we derive an explicit expression for the drift velocity. It should be possible to formulate similar parameterization-free models of normal grain growth in two and three dimensions.

  4. Dynamic recrystallization and grain growth in olivine rocks

    NARCIS (Netherlands)

    Kellermann Slotemaker, A.

    2006-01-01

    A mechanism based description of the rheology of olivine is essential for modeling of upper mantle geodynamics. Previously, mantle flow has been investigated using flow laws for grain size insensitive (GSI) dislocation creep and/or grain size sensitive (GSS) diffusion creep of olivine. Generally,

  5. Electric-Loading Enhanced Kinetics in Oxide Ceramics: Pore Migration, Sintering and Grain Growth: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-Wei [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science & Engineering

    2018-02-02

    Solid oxide fuel cells and solid oxide electrolysis cells rely on solid electrolytes in which a large ionic current dominates. This project was initiated to investigate microstructural changes in such devices under electrochemical forces, because nominally insignificant processes may couple to the large ionic current to yield non-equilibrium phenomena that alter the microstructure. Our studies had focused on yttria-stabilized cubic zirconia (YSZ) widely used in these devices. The experiments have revealed enhanced grain growth at higher temperatures, pore and gas bubble migration at all temperatures, and the latter also lead to enhanced sintering of highly porous ceramics into fully dense ceramics at unprecedentedly low temperatures. These results have shed light on kinetic processes that fall completely outside the realm of classical ceramic processing. Other fast-oxygen oxide ceramics closely related to, and often used in conjunction with zirconia ceramics, have also be investigated, as are closely related scientific problems in zirconia ceramics. These include crystal structures, defects, diffusion kinetics, oxygen potentials, low temperature sintering, flash sintering, and coarsening theory, and all have resulted in greater clarity in scientific understanding. The knowledge is leveraged to provide new insight to electrode kinetics and near-electrode mixed conductivity and to new materials. In the following areas, our research has resulted in completely new knowledge that defines the state-of-the-art of the field. (a) Electrical current driven non-equilibrium phenomena, (b) Enhanced grain growth under electrochemically reducing conditions, (c) Development of oxygen potential polarization in electrically loaded electrolyte, (d) Low temperature sintering and grain growth, and (e) Structure, defects and cation kinetics of fluorite-structured oxides. Our research has also contributed to synthesis of new energy-relevant electrochemical materials and new understanding

  6. Abnormal grain growth in Eurofer-97 steel in the ferrite phase field

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, V.B. [Lorena School of Engineering, University of Sao Paulo, Lorena, SP, 12602-810 (Brazil); Sandim, H.R.Z., E-mail: hsandim@demar.eel.usp.br [Lorena School of Engineering, University of Sao Paulo, Lorena, SP, 12602-810 (Brazil); Raabe, D. [Max-Planck-Institut für Eisenforschung, Düsseldorf, D-40237 (Germany)

    2017-03-15

    Reduced-activation ferritic-martensitic (RAFM) Eurofer-97 steel is a candidate material for structural applications in future fusion reactors. Depending on the amount of prior cold rolling strain and annealing temperature, important solid-state softening reactions such as recovery, recrystallization, and grain growth occur. Eurofer-97 steel was cold rolled up to 70, 80 and 90% reductions in thickness and annealed in the ferrite phase field (below ≈ 800 °C). Changes in microstructure, micro-, and mesotexture were followed by orientation mappings provided by electron backscatter diffraction (EBSD). Eurofer-97 steel undergoes abnormal grain growth above 650 °C and this solid-state reaction seems to be closely related to the high mobility of a few special grain boundaries that overcome pinning effects caused by fine particles. This solid-state reaction promotes important changes in the microstructure and microtexture of this steel. Abnormal grain growth kinetics for each condition was determined by means of quantitative metallography. - Highlights: • Abnormal grain growth (AGG) occurs in Eurofer-97 steel deformed to several strains. • Kinetics of abnormal grain growth has been determined at 750 and 800 °C. • Significant changes in crystallographic texture take place during AGG. • Grain boundaries with misorientations above 45° may explain abnormal grain growth. • Local microstructural instabilities (coarsening of M23C6 carbides) also explain AGG.

  7. Recycling process of Mn-Al doped large grain UO2 pellets

    International Nuclear Information System (INIS)

    Nam, Ik Hui; Yang, Jae Ho; Rhee, Young Woo; Kim, Dong Joo; Kim, Jong Hun; Kim, Keon Sik; Song, Kun Woo

    2010-01-01

    To reduce the fuel cycle costs and the total mass of spent light water reactor (LWR) fuels, it is necessary to extend the fuel discharged burn-up. Research on fuel pellets focuses on increasing the pellet density and grain size to increase the uranium contents and the high burnup safety margins for LWRs. KAERI are developing the large grain UO 2 pellet for the same purpose. Small amount of additives doping technology are used to increase the grain size and the high temperature deformation of UO 2 pellets. Various promising additive candidates had been developed during the last 3 years and the MnO-Al 2 O 3 doped UO 2 fuel pellet is one of the most promising candidates. In a commercial UO 2 fuel pellet manufacturing process, defective UO 2 pellets or scraps are produced and those should be reused. A common recycling method for defective UO 2 pellets or scraps is that they are oxidized in air at about 450 .deg. C to make U 3 O 8 powder and then added to UO 2 powder. In the oxidation of a UO 2 pellet, the oxygen propagates along the grain boundary. The U 3 O 8 formation on the grain boundary causes a spallation of the grains. So, size and shape of U 3 O 8 powder deeply depend on the initial grain size of UO 2 pellets. In the case of Mn-Al doped large grain pellets, the average grain size is about 45μm and about 5 times larger than a typical un-doped UO 2 pellet which has grain size of about 8∼10μm. That big difference in grain size is expected to cause a big difference in recycled U 3 O 8 powder morphology. Addition of U 3 O 8 to UO 2 leads to a drop in the pellet density, impeding a grain growth and the formation of graph- like pore segregates. Such degradation of the UO 2 pellet properties by adding the recycled U 3 O 8 powder depend on the U 3 O 8 powder properties. So, it is necessary to understand the property and its effect on the pellet of the recycled U 3 O 8 . This paper shows a preliminary result about the recycled U 3 O 8 powder which was obtained by

  8. Effects of seed geometry on the crystal growth and the magnetic properties of single grain REBCO bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hwi Joo; Lee, Hee Gyoun [Korea Polytechnic University, Siheung (Korea, Republic of); Park, Soon Dong; Jun, Bung Hyack; Kim, Chan Joong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-09-15

    This study presents that the orientation and the geometry of seed affect on the growth behavior of melt processed single grain REBCO bulk superconductor and its magnetic properties. The effects of seed geometry have been investigated for thin 30mm x 30mm rectangular powder compacts. Single grain REBCO bulk superconductors have been grown successfully by a top seed melt growth method for 8-mm thick vertical thin REBCO slab. Asymmetric structures have been developed at the front surface and at the rear surface of the specimen. Higher magnetic properties have been obtained for the specimen that c-axis is normal to the specimen surface. The relationships between microstructure, grain growth and magnetic properties have been discussed.

  9. Stochastic simulation of grain growth during continuous casting

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, A. [Department of Aerounatical Engineering, S.E.P.I., E.S.I.M.E., IPN, Instituto Politecnico Nacional (Unidad Profesional Ticoman), Av. Ticoman 600, Col. Ticoman, C.P.07340 (Mexico)]. E-mail: adalop123@mailbanamex.com; Carrillo, F. [Department of Processing Materials, CICATA-IPN Unidad Altamira Tamps (Mexico); Gonzalez, J.L. [Department of Metallurgy and Materials Engineering, E.S.I.Q.I.E.-IPN (Mexico); Lopez, S. [Department of Molecular Engineering of I.M.P., AP 14-805 (Mexico)

    2006-04-15

    The evolution of microstructure is a very important topic in material science engineering because the solidification conditions of steel billets during continuous casting process affect directly the properties of the final products. In this paper a mathematical model is described in order to simulate the dendritic growth using data of real casting operations; here a combination of deterministic and stochastic methods was used as a function of the solidification time of every node in order to create a reconstruction about the morphology of cast structures.

  10. Stochastic simulation of grain growth during continuous casting

    International Nuclear Information System (INIS)

    Ramirez, A.; Carrillo, F.; Gonzalez, J.L.; Lopez, S.

    2006-01-01

    The evolution of microstructure is a very important topic in material science engineering because the solidification conditions of steel billets during continuous casting process affect directly the properties of the final products. In this paper a mathematical model is described in order to simulate the dendritic growth using data of real casting operations; here a combination of deterministic and stochastic methods was used as a function of the solidification time of every node in order to create a reconstruction about the morphology of cast structures

  11. Microstructural characterization and grain growth kinetics of atomized Fe-6%Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Florio Filho, A.; Bolfarini, C.; Kiminami, C.S. [Dept. de Engenharia de Materiais, Univ. Federal de Sao Carlos, Sao Carlos SP (Brazil)

    2001-07-01

    The microstructural characterization of the overspray powders is considered an important step to evaluate the as-cast microstructure of preforms fabricated by spray forming process. The particles generated during the high pressure gas atomization fly toward a substrate located at the middle height into the atomization chamber and consolidate to a dense deposit. The solidification process begins already during the flight of the droplets and high cooling rate can be achieved by the droplets of the molten metal during the atomization step. Consequently, the microstructure of the preform has some typical features presented by rapidly solidified metals as low level of porosity and segregation and it is strongly influenced by the thermal history of the droplets during flight. In the present work the microstructure of the particles of the Fe-6%Si alloy was analysed by light microscopy and scanning electron microscopy (SEM). The experimental determination of the kinetic exponent n for grain boundary migration in both powder and preform was determined by isothermal treatment under argon atmosphere. It has been stated that the larger the particle size the greater the grain size in Fe-6%Si alloy. It was observed also that the interface morphology is strongly related to the particle size. Furthermore, the grain growth kinetic in the preform seems to not obey the migration mechanism where the self diffusion of elemental Fe drive the boundary displacement. (orig.)

  12. Innovative biological systems for anaerobic treatment of grain and food processing wastewaters

    Energy Technology Data Exchange (ETDEWEB)

    Sutton, P M

    1986-09-01

    The application of two innovative fixed film and suspended growth anaerobic biological systems to the treatment of grain and food processing wastewaters is discussed. A fluidized bed fixed film system and a suspended growth membrane system are described. The technical and economic factors dictating which system is selected for treatment of a specific industrial wastewater are discussed. Case history results from successful operation of full-scale, demonstration, and pilot-scale systems treating respectively, soy whey, cheese whey, and wheat flour processing wastewaters are presented.

  13. A micromechanical approach of suffusion based on a length scale analysis of the grain detachment and grain transport processes.

    Science.gov (United States)

    Wautier, Antoine; Bonelli, Stéphane; Nicot, François

    2017-06-01

    Suffusion is the selective erosion of the finest particles of a soil subjected to an internal flow. Among the four types of internal erosion and piping identified today, suffusion is the least understood. Indeed, there is a lack of micromechanical approaches for identifying the critical microstructural parameters responsible for this process. Based on a discrete element modeling of non cohesive granular assemblies, specific micromechanical tools are developed in a unified framework to account for the two first steps of suffusion, namely the grain detachment and the grain transport processes. Thanks to the use of an enhanced force chain definition and autocorrelation functions the typical lengths scales associated with grain detachment are characterized. From the definition of transport paths based on a graph description of the pore space the typical lengths scales associated with grain transport are recovered. For a uniform grain size distribution, a separation of scales between these two processes exists for the finest particles of a soil

  14. Appraisal on Textured Grain Growth and Photoconductivity of ZnO Thin Film SILAR

    Directory of Open Access Journals (Sweden)

    Deepu Thomas

    2014-01-01

    Full Text Available ZnO thin films were prepared by successive ionic layer adsorption reaction (SILAR method. The textured grain growth along c-axis in pure ZnO thin films and doped with Sn was studied. The structural analysis of the thin films was done by X-ray diffraction and surface morphology by scanning electron microscopy. Textured grain growth of the samples was measured by comparing the peak intensities. Textured grain growth and photo current in ZnO thin films were found to be enhanced by doping with Sn. ZnO thin film having good crystallinity with preferential (002 orientation is a semiconductor with photonic properties of potential benefit to biophotonics. From energy dispersive X-ray analysis, it is inferred that oxygen vacancy creation is responsible for the enhanced textured grain growth in ZnO thin films.

  15. New 3DXRD results on recrystallization and grain growth

    DEFF Research Database (Denmark)

    Juul Jensen, Dorte; West, Stine; Poulsen, Stefan Othmar

    2012-01-01

    New in-situ 3DXRD results obtained since the last Rex&GG conference are presented and discussed. This includes: Documentation of the formation of nuclei with new orientations, determination of apparent activation energies for individual bulk grains during recrystallization and evolution in the 3D...

  16. Stochastic modeling of columnar dendritic grain growth in weld pool of Al-Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Z.B.; Tian, N. [The State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin (China); Wei, Y.H. [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing (China); The State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin (China); Zhan, X.H.

    2009-04-15

    A multi-scale model is used to simulate columnar dendritic growth in TIG (tungsten inert-gas) weld molten pool of Al-Cu alloy. The grain morphologies at the edge of the weld pool are studied. The simulated results indicate that the average primary dendrite spacing changes during the solidification process in the weld pool because of the complicated thermal field, solute diffusion field and competitive growth. And it is shown that the secondary dendrite arms grow insufficiently in the space between dendrite trunks if the primary dendrite spacing is small. And the phenomenon has been explained by analyzing the influence of the solute accumulation on the constitutional undercooling and undercooling gradient when there are two different opposite solute diffusion fields. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Theory and modeling of microstructural evolution in polycrystalline materials: Solute segregation, grain growth and phase transformations

    Science.gov (United States)

    Ma, Ning

    2005-11-01

    To accurately predict microstructure evolution and, hence, to synthesis metal and ceramic alloys with desirable properties involves many fundamental as well as practical issues. In the present study, novel theoretical and phase field approaches have been developed to address some of these issues including solute drag and segregation transition at grain boundaries and dislocations, grain growth in systems of anisotropic boundary properties, and precipitate microstructure development in polycrystalline materials. The segregation model has allowed for the prediction of a first-order segregation transition, which could be related to the sharp transition of solute concentration of grain boundary as a function of temperature. The incorporating of interfacial energy and mobility as functions of misorientation and inclination in the phase field model has allowed for the study of concurrent grain growth and texture evolution. The simulation results were analyzed using the concept of local grain boundary energy density, which simplified significantly the development of governing equations for texture controlled grain growth in Ti-6Al-4V. Quantitative phase field modeling techniques have been developed by incorporating thermodynamic and diffusivity databases. The models have been validated against DICTRA simulations in simple 1D problems and applied to simulate realistic microstructural evolutions in Ti-6Al-4V, including grain boundary a and globular a growth and sideplate development under both isothermal aging and continuous cooling conditions. The simulation predictions agree well with experimental observations.

  18. Grain growth behavior and high-temperature high-strain-rate tensile ductility of iridium alloy DOP-26

    International Nuclear Information System (INIS)

    McKamey, C.G.; Gubbi, A.N.; Lin, Y.; Cohron, J.W.; Lee, E.H.; George, E.P.

    1998-04-01

    This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the new-process iridium-based DOP-26 alloy used for the Cassini space mission. This alloy was developed at Oak Ridge National Laboratory (ORNL) in the early 1980's and is currently used by NASA for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. Included within this report are data generated on grain growth in vacuum or low-pressure oxygen environments; a comparison of grain growth in vacuum of the clad vent set cup material with sheet material; effect of grain size, test temperature, and oxygen exposure on high-temperature high-strain-rate tensile ductility; and grain growth in vacuum and high-temperature high-strain-rate tensile ductility of welded DOP-26. The data for the new-process material is compared to available old-process data

  19. The effect of some growth regulators on enzyme systems in irradiated barley grain using disinfestation doses

    International Nuclear Information System (INIS)

    Bachman, S.

    1973-01-01

    Disinfestation doses of 20 to 100 krad may cause changes in the biological systems of barley grain and, therefore, may influence undesirably the technological quality of malted grain. The effect of some growth regulators on irradiated grain has been investigated. The experiments have been carried out on brewery barley var. Visa Breuns. Following growth-regulators were used: gibberellic acid (Polish preparation ''Gibrescol''), kinetin (6-furfurylo-aminopurin), CCC (2-chloroethyl trimethyl ammonium chloride), and betaine hydrochloride. By treating the irradiated barley with solutions of growth regulators it was possible to diminish the loss of enzyme activity. A ''regenerating'' effect of growth substances, mainly gibberellic acid and betain hydrochloride in 10 -4 M solutions, was observed. Amylolytic activity decreased immediately after irradiation but in samples treated with growth regulators it was higher than in those without regulators. The results may have a practical importance since gibberellic acid has just been introduced into the brewery industry. (F.J.)

  20. Nanocrystalline growth and grain-size effects in Au-Cu electrodeposits

    International Nuclear Information System (INIS)

    Jankowski, Alan F.; Saw, Cheng K.; Harper, Jennifer F.; Vallier, Bobby F.; Ferreira, James L.; Hayes, Jeffrey P.

    2006-01-01

    The processing-structure-property relationship is investigated for electrodeposited foils of the gold-copper alloy system. A model is presented that relates the deposition process parameters to the nanocrystalline grain size. An activation energy of 1.52 eV atom -1 for growth is determined for a long-pulse (> 10 msec) mode, and is 0.16 eV atom -1 for short pulses ( 6 nm) is observed for Au-Cu samples with 1-12 wt.% Cu as tested in cross-section. The hardness increases three-fold from a rule-of-mixtures value < 1 GPa to a maximum of 2.9 GPa

  1. Fine-Grained Turbidites: Facies, Attributes and Process Implications

    Science.gov (United States)

    Stow, Dorrik; Omoniyi, Bayonle

    2016-04-01

    Within turbidite systems, fine-grained sediments are still the poor relation and sport several contrasting facies models linked to process of deposition. These are volumetrically the dominant facies in deepwater and, from a resource perspective, they form important marginal and tight reservoirs, and have great potential for unconventional shale gas, source rocks and seals. They are also significant hosts of metals and rare earth elements. Based on a large number of studies of modern, ancient and subsurface systems, including 1000s of metres of section logging, we define the principal genetic elements of fine-grained deepwater facies, present a new synthesis of facies models and their sedimentary attributes. The principal architectural elements include: non-channelised slope-aprons, channel-fill, channel levee and overbank, turbidite lobes, mass-transport deposits, contourite drifts, basin sheets and drapes. These comprise a variable intercalation of fine-grained facies - thin-bedded and very thin-bedded turbidites, contourites, hemipelagites and pelagites - and associated coarse-grained facies. Characteristic attributes used to discriminate between these different elements are: facies and facies associations; sand-shale ratio, sand and shale geometry and dimensions, sand connectivity; sediment texture and small-scale sedimentary structures; sediment fabric and microfabric; and small-scale vertical sequences of bed thickness. To some extent, we can relate facies and attribute characteristics to different depositional environments. We identify four distinct facies models: (a) silt-laminated mud turbidites, (b) siliciclastic mud turbidites, (c) carbonate mud turbidites, (d) disorganized silty-mud turbidites, and (e) hemiturbidites. Within the grainsize-velocity matrix turbidite plot, these all fall within the region of mean size < 0.063mm, maximum grainsize (one percentile) <0.2mm, and depositional velocity 0.1-0.5 m/s. Silt-laminated turbidites and many mud

  2. Large scale statistics for computational verification of grain growth simulations with experiments

    International Nuclear Information System (INIS)

    Demirel, Melik C.; Kuprat, Andrew P.; George, Denise C.; Straub, G.K.; Misra, Amit; Alexander, Kathleen B.; Rollett, Anthony D.

    2002-01-01

    It is known that by controlling microstructural development, desirable properties of materials can be achieved. The main objective of our research is to understand and control interface dominated material properties, and finally, to verify experimental results with computer simulations. We have previously showed a strong similarity between small-scale grain growth experiments and anisotropic three-dimensional simulations obtained from the Electron Backscattered Diffraction (EBSD) measurements. Using the same technique, we obtained 5170-grain data from an Aluminum-film (120 (micro)m thick) with a columnar grain structure. Experimentally obtained starting microstructure and grain boundary properties are input for the three-dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 C. Characterization of the structures and properties of grain boundary networks (GBN) to produce desirable microstructures is one of the fundamental problems in interface science. There is an ongoing research for the development of new experimental and analytical techniques in order to obtain and synthesize information related to GBN. The grain boundary energy and mobility data were characterized by Electron Backscattered Diffraction (EBSD) technique and Atomic Force Microscopy (AFM) observations (i.e., for ceramic MgO and for the metal Al). Grain boundary energies are extracted from triple junction (TJ) geometry considering the local equilibrium condition at TJ's. Relative boundary mobilities were also extracted from TJ's through a statistical/multiscale analysis. Additionally, there are recent theoretical developments of grain boundary evolution in microstructures. In this paper, a new technique for three-dimensional grain growth simulations was used to simulate interface migration

  3. EFFECT OF SOME PLANT GROWTH REGULATORS WITH RETARDING ACTIVITY ON SPRING PEA FOR GRAIN

    Directory of Open Access Journals (Sweden)

    Tsenka ZHELYAZKOVA

    2012-12-01

    Full Text Available A field experiment was conducted at Trakia University - Stara Zagora to establish the effect of some growth retardants on morphological and productive parameters in spring pea for grain variety Bogatir. Three combined preparations: Trisalvit (phenylphthalamic acid + chlorocholine chloride + chlorophenoxyacetic acid +salicylic acid at doses of 300 and 400 сmз*ha-1; SM-21 (phenylphthalamic acid + chlorocholine chloride at doses of 300 and 400 сmз*ha-1 and PNSA-44 (phenylphthalamic acid + naphthaleneacetic acid + chlorophenoxyacetic acid at doses of 200 and 300 сmз*ha-1 were applied in the early growth phase of the plant up to a height of 15-20 cm. The study showed that the greatest reduction in the stem height (by 12.8% compared to untreated plants was achieved by applying SM-21 (400 сmз*ha-1. The application of growth regulators Trisalvit and SM-21 had no appreciable effect on the production of spring pea grain. Maximum values of yield structure components (number of pods and grain per plant, grain mass per plant and mass of 1000 grain and the yield were obtained after application of PNSA-44 (300 сmз*ha-1 - up to 5.6% (117.2 kg*ha-1 more grain than the control. The investigation of the influence of tested factors (retardant, dose and year demonstrated that the conditions of the year as a factor had the strongest effect on plant height and grain yield.

  4. Growth process of helium bubbles in aluminium

    International Nuclear Information System (INIS)

    Shiraishi, Haruki; Sakairi, Hideo; Yagi, Eiichi; Karasawa, Takashi; Hashiguti, R.R.

    1975-01-01

    The growth process of helium bubbles in α-particle bombarded pure aluminum during isothermal anneal ranging 200 to 645 0 C and 1 to 100 hr was observed by a transmission electron microscope and the possible growth mechanisms are discussed. The effects of helium concentration and cold work were investigated. The helium bubbles are detectable only at the anneal above 550 0 C in both annealed and cold worked samples. The cold work does not cause any extra coarsening trend of bubbles. The observed types of bubble distribution in the grain interior are divided into two categories, irrespective of helium concentration and cold work; (1) the fine and uniform bubble distribution, in which case the average size is limited to about 200 A or less in diameter even at the anneal just below the melting point, and (2) the coarsened and non-uniform bubble distribution ranging 500 to 4000 A in diameter. The intermediate size bubbles are scarcely found in any cases. In the above fine bubble distribution, the increase of helium concentration by a factor of two increases the density by the same factor of two, but does not change the mean size of bubbles. Corresponding to the above two characteristic bubble distributions, it is concluded that two different mechanisms are operative in this experiment; (1) the growth of bubbles by the Brownian motion, in which the growth rate of bubbles is decreased to almost zero by bubble faceting and this results in the bubble size constancy during the prolonged annealing, and (2) the growth of bubbles by the grain boundary sweep-out mechanism, by which the abrupt coarsening of bubbles is caused. The lack of existence of the intermediate size bubbles is explained in this way. (auth.)

  5. Niobium effects on the austenitic grain growth and hardenability of steels for mechanical construction

    International Nuclear Information System (INIS)

    Vieira, R.R.; Arruda Camargo, L.M. de; Oliveira Junior, G.G. de; Dias Filho, A.G.C.

    1983-01-01

    The austenitic grain growth and hardenability of SAE 86XX and 5120 steels modified with 0,001 to 0,20 per-cent niobium content were studied when submitted to case hardening and quenching heat treatments. The results show that niobium controlS the austenite grain size better than molybdenum up to 950 0 C austenitization temperature. The hardenability, evaluated by the Jominy test which the modified SAE 8640 steels, is more strongly inflencied by the grain refining resulting from niobium addition than by any other supposed effect. (Author) [pt

  6. Austenite grain growth and microstructure control in simulated heat affected zones of microalloyed HSLA steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei [Department of Machine Tools and Factory Management, Technical University of Berlin, Pascalstraße 8 – 9, 10587, Berlin (Germany); Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Kannengiesser, Thomas [Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Institute of Materials and Joining Technology, Otto von Guericke University Magdeburg, Universitetsplatz 2, 39106, Magdeburg (Germany)

    2014-09-08

    The roles of microalloying niobium, titanium and vanadium for controlling austenite grain growth, microstructure evolution and hardness were investigated at different simulated heat affected zones (HAZ) for high strength low alloy (HSLA) S690QL steel. High resolution FEG-SEM has been used to characterize fine bainitic ferrite, martensite and nanosized second phases at simulated coarse and fine grain HAZs. It was found that for Ti bearing steel (Ti/N ratio is 2) austenite grain had the slowest growth rate due to the presence of most stable TiN. The fine cuboidal particles promoted intragranular acicular ferrite (IGF) formation. Nb bearing steel exhibited relatively weaker grain growth retardation compared with titanium bearing steels and a mixed microstructure of bainite and martensite was present for all simulated HAZs. IGF existed at coarse grain HAZ of Ti+V bearing steel but it was totally replaced by bainite at fine grain HAZs. Hardness result was closely related to the morphology of bainitic ferrite, intragranular ferrite and second phases within ferrite. The microstructure and hardness results of different simulated HAZs were in good agreement with welded experimental results.

  7. Explosive anisotropic grain growth of delta-NiMo by solid-state diffusion

    International Nuclear Information System (INIS)

    Chou, T.C.; Nieh, T.G.

    1991-01-01

    Anomalous, anisotropic grain growth has been observed in delta(δ)-NiMo intermetallic compound during the annealings of Mo/Ni thin-film diffusion couples at 700 and 800 degree C. Two layered microstructures showing median-sized, equiaxed grains and large columnar single crystalline grains were generated. The growth direction of the columnar grains was parallel to the direction of Ni diffusion flux. Electron diffraction indicated that both the median-sized and the columnar grains were δ-NiMo. The composition of δ-NiMo was determined to be Ni48-Mo52 (at.%). According to the thickness of reaction-formed δ-NiMo, the apparent interdiffusion coefficient was measured to be about 10 -10 cm 2 /s which is 4 to 5 orders of magnitude greater than literature data. The enhanced diffusion rate in Ni-Mo, and the anomalous anisotropic grain growth of δ-NiMo compound are discussed on the basis of exothermic reactions between Ni and Mo during diffusional intermixing. The enthalpy of the formation of δ-NiMo is calculated and demonstrated to be sufficient to cause melting/solidification of the compound

  8. Effect of Cassava Processing Effluent on Soil Properties, Growth and ...

    African Journals Online (AJOL)

    A study, comprising a survey, greenhouse and field experiments was conducted to examine the effect of Cassava Processing Effluent (CPE) on soil chemical properties, maize growth performances and grain yield. In the survey, soil samples were taken (0-15 and 15 – 30cm) of CPE contaminated and non contaminated ...

  9. Influence of intermediate annealing on abnormal Goss grain growth in the rolled columnar-grained Fe-Ga-Al alloys

    International Nuclear Information System (INIS)

    Liu, Yangyang; Li, Jiheng; Gao, Xuexu

    2017-01-01

    Highlights: • Texture of primary IA sample was dominated by γ-fiber with a peak at {1 1 1}<1 1 0>. • Texture of primary CR sample was dominated by {1 1 3}<1 1 4> texture. • Inhomogeneous microstructure was significantly improved in primary IA sample. • Strong Goss texture was obtained in final IA sample without surface energy control. - Abstract: Magnetostrictive Fe 82 Ga 4.5 Al 13.5 sheets with 0.1 at% NbC were prepared from directional solidified alloys with <0 0 1> preferred orientation. The slabs were hot rolled at 650 °C and warm rolled at 500 °C. Then some warm-rolled sheets were annealed intermediately at 850 °C for 5 min but the others not. After that, all the sheets were cold rolled to a final thickness of ∼0.3 mm. The microstructures, the textures and the distributions of second phase particles in the primary recrystallized samples were investigated. With intermediate annealing, the inhomogeneous microstructure was improved remarkably and strong Goss ({1 1 0}<0 0 1>) and γ-fiber (<1 1 1>//normal direction [ND]) textures were produced in the primary recrystallized samples. But, an evident disadvantage in size and quantity was observed for Goss grains in the primary recrystallized sample without intermediate annealing. After a final annealing, the final textures and magnetostrictions of samples with and without intermediate annealing were characterized. For samples without intermediate annealing, abnormal growth of {1 1 3} grains occurred and deteriorated the magnetostriction. In contrast, abnormal Goss grain growth occurred completely in samples with intermediate annealing and led to saturation magnetostriction as high as 156 ppm.

  10. Influence of intermediate annealing on abnormal Goss grain growth in the rolled columnar-grained Fe-Ga-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yangyang; Li, Jiheng; Gao, Xuexu, E-mail: gaox@skl.ustb.edu.cn

    2017-08-01

    Highlights: • Texture of primary IA sample was dominated by γ-fiber with a peak at {1 1 1}<1 1 0>. • Texture of primary CR sample was dominated by {1 1 3}<1 1 4> texture. • Inhomogeneous microstructure was significantly improved in primary IA sample. • Strong Goss texture was obtained in final IA sample without surface energy control. - Abstract: Magnetostrictive Fe{sub 82}Ga{sub 4.5}Al{sub 13.5} sheets with 0.1 at% NbC were prepared from directional solidified alloys with <0 0 1> preferred orientation. The slabs were hot rolled at 650 °C and warm rolled at 500 °C. Then some warm-rolled sheets were annealed intermediately at 850 °C for 5 min but the others not. After that, all the sheets were cold rolled to a final thickness of ∼0.3 mm. The microstructures, the textures and the distributions of second phase particles in the primary recrystallized samples were investigated. With intermediate annealing, the inhomogeneous microstructure was improved remarkably and strong Goss ({1 1 0}<0 0 1>) and γ-fiber (<1 1 1>//normal direction [ND]) textures were produced in the primary recrystallized samples. But, an evident disadvantage in size and quantity was observed for Goss grains in the primary recrystallized sample without intermediate annealing. After a final annealing, the final textures and magnetostrictions of samples with and without intermediate annealing were characterized. For samples without intermediate annealing, abnormal growth of {1 1 3} grains occurred and deteriorated the magnetostriction. In contrast, abnormal Goss grain growth occurred completely in samples with intermediate annealing and led to saturation magnetostriction as high as 156 ppm.

  11. A simple method to evaluate the fission gas release at fuel grain boundary including the grain growth both at constant and at transient power histories

    International Nuclear Information System (INIS)

    Paraschiv, M.; Paraschiv, A.

    1991-01-01

    A method to rewrite Fick's second law for a region with a moving boundary when the moving law in time of this boundary is known, has been proposed. This method was applied to Booth's sphere model for radioactive and stable fission product diffusion from the oxide fuel grain in order to take into account the grain growth. The solution of this new equation was presented in the mathematical formulation for power histories from ANS 5.4 model for the stable species. It is very simple to apply and very accurate. The results obtained with this solution for constant and transient temperatures show that the fission gas release (FGR) at grain boundary is strongly dependent on kinetics of grain growth. The utilization of two semiempirical grain growth laws, from published information, shows that the fuel microstructural properties need to be multicitly considered in the fission gas release for every manufacturer of fuel. (orig.)

  12. Toxic micromycetes in grain raw material during its processing.

    Science.gov (United States)

    Lugauskas, Albinas; Raila, Algirdas; Railiene, Marija; Raudoniene, Vita

    2006-01-01

    In 2003-2005 micromycetes were isolated and identified from wheat, barley, rye, buckwheat grain brought into mills or from processing enterprises. Contamination of the produced flour with micromycete propagules (cfu g(-1)), changes in micromycete diversity and abundance in the course of flour storage, preparation and baking of bread, production of groats or other food products and fodder were determined. Most attention was given to widely distributed micromycetes, known producers of toxins: Alternaria alternata, Aspergillus candidus, A. clavatus, A. flavus, A. fumigatus, A. niger, A. oryzae, A. (=Eurotium) repens, Fusarium culmorum, F. equiseti, F. graminearum, F. moniliforme, F. oxysporum, F. poae, F. sporotrichioides, Penicillium brevicompactum, P. chrysogenum, P. cyclopium, P. daleae, P. expansum, P. funiculosum, P. roqueforti, P. urticae, P. verruculosum, P. viridicatum, Phoma exiqua, Rhizomucor pusillus, Rhizopus stolonifer, Trichothecium roseum. Abilities of these micromycetes to produce secondary toxic metabolites were determined as well as possible hazard caused to people consuming the contaminated products.

  13. Effects of grain source, grain processing, and protein degradability on rumen kinetics and microbial protein synthesis in Boer kids.

    Science.gov (United States)

    Brassard, M-E; Chouinard, P Y; Berthiaume, R; Tremblay, G F; Gervais, R; Martineau, R; Cinq-Mars, D

    2015-11-01

    Microbial protein synthesis in the rumen would be optimized when dietary carbohydrates and proteins have synchronized rates and extent of degradation. The aim of this study was to evaluate the effect of varying ruminal degradation rate of energy and nitrogen sources on intake, nitrogen balance, microbial protein yield, and kinetics of nutrients in the rumen of growing kids. Eight Boer goats (38.2 ± 3.0 kg) were used. The treatments were arranged in a split-plot Latin square design with grain sources (barley or corn) forming the main plots (squares). Grain processing methods and levels of protein degradability formed the subplots in a 2 × 2 factorial arrangement for a total of 8 dietary treatments. The grain processing method was rolling for barley and cracking for corn. Levels of protein degradability were obtained by feeding untreated soybean meal (SBM) or heat-treated soybean meal (HSBM). Each experimental period lasted 21 d, consisting of a 10-d adaptation period, a 7-d digestibility determination period, and a 4-d rumen evacuation and sampling period. Kids fed with corn had higher purine derivatives (PD) excretion when coupled with SBM compared with HSBM and the opposite occurred with barley-fed kids ( ≤ 0.01). Unprocessed grain offered with SBM led to higher PD excretion than with HSBM whereas protein degradability had no effect when processed grain was fed ( ≤ 0.03). Results of the current experiment with high-concentrate diets showed that microbial N synthesis could be maximized in goat kids by combining slowly fermented grains (corn or unprocessed grains) with a highly degradable protein supplement (SBM). With barley, a more rapidly fermented grain, a greater microbial N synthesis was observed when supplementing a low-degradable protein (HSBM).

  14. Interaction Between Second-Phase Particle Dissolution and Abnormal Grain Growth in an Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Dutra J.C.

    2002-01-01

    Full Text Available The continuing development of stainless steels has resulted in complex steel compositions with substantial amounts of alloying elements. The benefits of such additions invariably come attached to unavoidable disadvantages. One of the most critical item is the potential microstructural instability of the material. Alloying elements may be in a supersaturated solid solution, in which the precipitation of carbides, nitrides, borides and intermetallic phases occurs in a wide range of temperatures. In order to dissolve the mentioned precipitates, solution annealing is commonly performed. However, at the temperature range in which this treatment is carried out, the onset of abnormal grain growth can occur. The interaction between the dissolution of these second-phase particles and the occurrence of abnormal grain growth is investigated in this work. This study also shows that the thermodynamics and the kinetics of dissolution of precipitates may be used to predict whether abnormal grain growth takes place.

  15. Structure and grain coarsening during the processing of engineering ceramics

    International Nuclear Information System (INIS)

    Shaw, N.J.

    1987-11-01

    Studies have been made of three ceramic systems (Al 2 O 3 , Y 2 O 3 /MgO, and SiC/C/B), both to explore a surface area/density diagram approach to examining the coarsening processes during sintering and to explore an alternative coarsening parameter, i.e., the grain boundary surface area (raising it at a given value of the density) and not the pore surface area; therefore, pinning of the grain boundaries by solid-solution drag is the only function evidenced by these results. The importance of such pinning even at densities as low as 75% of theoretical is linked to the existence of microstructural inhomogeneities. The early stages of sintering of Y 2 O 3 powder have been examined using two techniques, BET surface area analysis and transmission electron microscopy. Each has given some insight into the process occurring and, used together, have provided some indication of the effect of MgO on coarsening during sintering. Attempts to further elucidate effects of MgO on the coarsening behavior of Y 2 O 3 by the surface area/density diagram approach were unsuccessful due to masking effects of contaminating reactions during sintering and/or thermal etching. The behavior of the undoped SiC which only coarsens can be clearly distinguished by the surface area/density diagram from that of SiC/C/B which also concurrently densifies. Little additional information was obtainable by this method due to unfavorable sample etching characteristics. The advantages, disadvantages, and difficulties of application of these techniques to the study of coarsening during sintering are discussed

  16. Growth behavior of fatigue cracks in ultrafine grained Cu smooth specimens with a small hole

    Directory of Open Access Journals (Sweden)

    Masahiro Goto

    2015-10-01

    Full Text Available In order to study the growth mechanism of fatigue cracks in ultrafine grained copper, stresscontrolled fatigue tests of round-bar specimens with a small blind hole as a crack starter were conducted. The hole was drilled on the surface where an intersection between the shear plane of the final ECAP processing and the specimen surface makes an angle of 45° or 90° with respect to the loading axis. At a low stress (  a = 90 MPa, the direction of crack paths was nearly perpendicular to the loading direction regardless of the location of the hole. Profile of crack face was examined, showing the aspect ratio (b/a of b/a = 0.82. At a high stress (  a = 240 MPa, although the growth directions inclined 45° and 90° to the loading-axis were observed depending on the location of the drilling hole, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the final ECAP shear plane. The value of aspect ratios was b/a = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions, respectively. The role of deformation mode at the crack tip areas on crack growth behavior were discussed in terms of the mixed-mode stress intensity factor. The crack path formation at high stress amplitudes was affected by the in-plane shear-mode deformation at the crack tip.

  17. Effect of additives on enhanced sintering and grain growth in uranium dioxide

    International Nuclear Information System (INIS)

    Bourgeois, L.

    1992-06-01

    The use of sintering additives has been the most effective way of promoting grain growth of uranium dioxide. We have established a same mechanism for additives which belongs to corundum structure: chromium, aluminium, vanadium and titanium sesquioxides. Study of thermodynamical stabilities of dopants has lead to define suitable sintering atmospheres in order to enhance grain growth. Low solubility limits have been defined at T=1700 deg C for four additives, from variations of final grain size versus initial dopant concentration Identification of second phase after cooling has been done from electronic diffraction patterns. It appears that these solubilities decrease sharply as positive deviation from stoichiometry of uranium dioxide increases. Dilatometric analysis of sintering of doped uranium dioxide has shown in certain cases some enhancement in densification rates, at the point of onset of abnormal grain growth, which is believed to be the source. Nevertheless, the following growth is accompanied with pores coalescence mechanisms and pores entrapment inside grains. Increased thermal stability, during standard annealing, is expected, limiting thereby redensification of nuclear fuel in reactors. Finally, from investigations of additives vaporizations, Al 2 O 3 and Cr 2 O 3 , oxygen exchanges between additives and matrix are believed to occur, which should lead to enhance pore mobility. (Author)., refs., figs., tabs

  18. Y{sub 2}BaCuO{sub 5} particle distribution in YBa{sub 2}Cu{sub 3}O{sub 7-y} grains of melt growth processed YBCO oxides; Y{sub 2}BaCuO{sub 5}-Partikelverteilung in YBa{sub 2}Cu{sub 3}O{sub 7-y}-Koernern durch das Melt-Growth-Verfahren verarbeiteter YBCO-Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chan-Joong; Park, Soon-Dong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of). Neutron Science Div.; Park, Hai-Woong [Korea Univ. of Technology and Education, Chungnam (Korea, Republic of). College of Energy, Materials and Chemical Engineering

    2013-02-01

    Y{sub 2}BaCuO{sub 5} (Y211) particle distribution within YBa{sub 2}Cu{sub 3}O{sub 7-y} (Y123) grains of YBCO samples melt growth (MG) processed was examined. To understand the processing variables on the Y211 distribution, a cooling rate (R{sub C}=1 K/h to R{sub C}=20 K/h) through a peritectic temperature (T{sub p} = 1010 C), a precursor powder size and composition were changed. Two different Y211 distributions (a linear x-like track and planar butterfly-like pattern) were observed, depending on the processing variables. The linear x-like Y211 tracks were observed in the Y123 samples prepared using a stoichiometric Y123 precursor, whereas the planar butterfly-like Y211 patterns were observed in the Y{sub 1.8}Ba{sub 2.4}Cu{sub 3.4}O{sub 7-d} (Y1.8) samples prepared using an Y211-excess composition precursor. The track and planar Y211 patterns were clearer at lower R{sub C} (slower growth rate of Y123 grains) and for the smaller Y211 particles. In contrast, the random Y211 distribution was dominant at the higher R{sub C} and for the larger Y211 particles. The Y211 distribution patterns in the Y123 grains were explained in terms of the interfacial energy difference among growing Y123 fronts. (orig.)

  19. A buffer bridge process for growing multiple YBa2Cu3O7-y grains from one top seed

    International Nuclear Information System (INIS)

    Lee, J-H; Park, S-D; Jun, B-H; Lee, J S; Kim, C-J; Han, S C; Han, Y H

    2011-01-01

    This study presents a buffer bridge process that allows growing multiple YBa 2 Cu 3 O 7-y (Y123) grains from one top seed. This process uses a buffer bridge pellet (Y 2 BaCuO 5 or Y123) to deliver the Y123 growth from one seed to several Y123 compacts. The top seeded melt growth (TSMG) process combined with the buffer bridge process facilitated the fabrication of several single-grained Y123 superconductors using one seed. In addition to achieving the growth of multiple Y123 grains, this process ensured a uniform distribution of superconducting properties of the top surface because the seed/compact interface area (the number of seeds), which is the route for the impurities from the seeds, was minimized. Additionally, the impurity contamination from a seed was considerably suppressed using a buffer pellet. One (110) diagonal facet line, as a result of the corner-to-corner growth, developed on the top surfaces of the prepared Y123 compacts, which is comparable to the x-like facet line of the conventional TSMG processed samples. The trapped magnetic field (H) profiles at 77 K of the prepared Y123 compacts, which were estimated using an Nd-B-Fe permanent magnet, showed the H contour map of a single-grain mode. The force-distance curves for the field cooled and zero-field cooled Y123 compacts at 77 K showed high and reliable levitation forces with a small deviation among compacts. The buffer bridge process can be applied to a batch process for the mass production of single-grain REBa 2 Cu 3 O 7-y (RE: rare-earth elements) superconductors with uniform top surface properties.

  20. Numerical study of the grain growth and the thermal properties of ceramics

    International Nuclear Information System (INIS)

    Shahtahmasebi, N.; Shariaty ghleno, A.M.; Hosaini, M.

    2000-04-01

    The physical properties of ceramics strongly depends on the grain size, which itself depends on the sintering process. In this work we propose a model for sintering based on the gross features known experimental and the preform numerical study

  1. Effect of sintering condition on the grain growth of Cr{sub 2}O{sub 3} doped UO{sub 2} pellets

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jang Soo; Kim, Keon Sik; Kim, Dong Joo; Kim, Jong Hun; Yang, Jae Ho [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In this paper, Cr{sub 2}O{sub 3} doped UO{sub 2} pellets were fabricated by two-step sintering process. The grain growth of pellet is related to dwell time in a hydrogen atmosphere during sintering process. A large grain pellet can minimize fission gas release and deform easily at an elevated temperature. So, the recent development of nuclear fuel pellet materials is mainly focused on the large grain pellets. The various methods of fabrication processes for large grain UO{sub 2} pellets have been investigated extensively. Those parameters include the additives, sintering temperature, sintering time, sintering atmosphere, and so on. Cr-doped UO{sub 2} pellet is one of the promising candidates for PCI remedy. It was shown that the grain size and softness of UO{sub 2} pellets could be enhanced by doping Cr or Cr compound in UO{sub 2}. Various in-pile test results revealed that the PCI properties were enhanced considerably [4]. In the sintering process of Cr-doped UO{sub 2} pellet, it was known that tight adjusting of sintering atmosphere is most important to achieve large grain pellet. The relevant research revealed that the doped Cr{sub 2}O{sub 3} became liquid phase in optimized oxygen potential and that liquid phase promoted the grain growth. Recently, KAERI has shown that grain size of Cr-doped UO{sub 2} pellet could be more enlarged by adjusting process parameters. In this paper, we introduced a sintering process which can form a liquid phase for a large grain growth in Cr{sub 2}O{sub 3} doped UO{sub 2} pellet. The study on the effect of dwell time in H{sub 2} atmosphere during sintering process on the grain structure of sintered pellet is also a part of this work. In order to obtain large grain in pellet, it is important to increase amount of Cr that can form a liquid phase for grain growth by increasing dwell time in a hydrogen atmosphere during sintering process.

  2. Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples

    Science.gov (United States)

    Suslova, A.; El-Atwani, O.; Sagapuram, D.; Harilal, S. S.; Hassanein, A.

    2014-11-01

    Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten.

  3. A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

    Science.gov (United States)

    Paquette, John A.; Ferguson, Frank T.; Nuth, Joseph A., III

    2011-01-01

    Based on its abundance, high bond energy, and recent measurements of its vapor pressure SiO is a natural candidate for dust nucleation in circumstellar outflows around asymptotic giant branch stars. In this paper, we describe a model of the nucleation and growth of silicate dust in such outflows. The sensitivity of the model to varying choices of poorly constrained chemical parameters is explored, and the merits of using scaled rather than classical nucleation theory are briefly considered, An elaboration of the model that includes magnesium and iron as growth species is then presented and discussed. The composition of the bulk of the grains derived from the model is consistent with olivines and pyroxenes, but somewhat metal-rich grains and very small, nearly pure SiO grains are also produced,

  4. Multiple oxide content media for columnar grain growth in L10 FePt thin films

    International Nuclear Information System (INIS)

    Ho, Hoan; Yang, En; Laughlin, David E.; Zhu, Jian-Gang

    2013-01-01

    An approach to enhance the height-to-diameter ratio of FePt grains in heat-assisted magnetic recording media is proposed. The FePt-SiO x thin films are deposited with a decrease of the SiO x percentage along the film growth direction. When bi-layer and tri-layer media are sputtered at 410 °C, we observe discontinuities in the FePt grains at interfaces between layers, which lead to poor epitaxial growth. Due to increased atomic diffusion, the bi-layer media sputtered at 450 °C is shown to (1) grow into continuous columnar grains with similar size as single-layer media but much higher aspect ratio, (2) have better L1 0 ordering and larger coercivity.

  5. Short-time beta grain growth kinetics for a conventional titanium alloy

    International Nuclear Information System (INIS)

    Semiatin, S.L.; Sukonnik, I.M.

    1996-01-01

    The kinetics of beta grain growth during short-time, supertransus heat treatment of Ti-5Al-4V were determined using a salt-pot technique. The finite-time, subtransus temperature transient during salt-pot heating was quantified through measurements of the heat transfer coefficient characterizing conduction across the salt-titanium interface and a simple heat conduction analysis which incorporated this heat transfer coefficient. Grain size versus time data adjusted to account for the subtransus temperature transient were successfully fit to the parabolic grain growth law d n - d 0 n = kt exp(-Q/RT) using an exponent n equal to 2.0. Comparison of the present results to rapid, continuous heat treatment data in the literature for a similar titanium alloy revealed a number of semi-quantitative similarities

  6. Numerical and Experimental Investigation of the Influence of Growth Restriction on Grain Size in Binary Cu Alloys

    Directory of Open Access Journals (Sweden)

    Andreas Cziegler

    2017-09-01

    Full Text Available Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the growth restriction factor Q, grain size modelling was performed. The results obtained by the grain size model were compared to variations in the grain size of binary Cu alloys with increasing solute content under defined cooling conditions of the TP-1 grain refiner test of the Aluminium Association©. It was found that the experimental results differed significantly from the predicted grain size values for several alloying elements. A decreasing grain size with increasing alloy concentration was observed independently of the growth restriction potency of the alloying elements. Furthermore, excessive grain coarsening was found for several solutes beyond a transition point. It is assumed that contradictory variations in grain size result from a change in the nucleating particle density of the melt. Significant decreases in grain size are supposed to be due to the in-situ formation of potent nucleation sites. Excessive grain coarsening with increasing solute content may occur due to the removal of nucleating particles. The model shows that the difference in the actual number of particles before and beyond the transition point must be in the range of several orders of magnitude.

  7. Achieving excellent thermal stability and very high activation energy in an ultrafine-grained magnesium silver rare earth alloy prepared by friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Khan MD, F. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Panigrahi, S.K., E-mail: skpanigrahi@iitm.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

    2016-10-15

    Ultrafine-grained microstructure of a QE22 alloy prepared by Friction Stir processing (FSP) is isochronally annealed to study the thermal stability and grain growth kinetics. The FSPed microstructure of QE22 alloy is thermally stable under ultrafine-grained regime up to 300 °C and the activation energy required for grain growth is found to be exceptionally high as compared to conventional ultrafine-grained magnesium alloys. The high thermal stability and activation energy of the FSPed QE22 alloy is due to Zener pinning effect from thermally stable eutectic Mg{sub 12}Nd and fine precipitates Mg{sub 12}Nd{sub 2}Ag and solute drag effect from segregation of Neodymium (Nd) solute atoms at grain boundaries.

  8. Watching the growth of bulk grains during recrystallization of deformed metals

    DEFF Research Database (Denmark)

    Schmidt, Søren; Fæster Nielsen, Søren; Gundlach, C.

    2004-01-01

    , contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical...

  9. Grain growth kinetics of textured-BaTiO3 ceramics

    Indian Academy of Sciences (India)

    Administrator

    3Department of Physics and Materials Science, City University of Hong Kong, Hong Kong ... Abstract. Textured BaTiO3 (BT) ceramics were fabricated by templated grain growth method. Effects of ... approaches to improve electrical properties of lead-free ceramics. ... modification methods to enhance the piezoelectric pro-.

  10. Effect of pre- and post-heading waterlogging on growth and grain yield of four millets

    Directory of Open Access Journals (Sweden)

    Asana Matsuura

    2016-07-01

    Full Text Available Seeds of Panicum miliaceum, Panicum sumatrense, Setaria glauca, and Setaria italica were raised in polyvinylchloride tubes filled with soil to determine interspecific differences in waterlogging tolerance and the effect of pre- and post-heading waterlogging on growth and grain yield. Four treatments were conducted including control (no-waterlogging stress during growth. Pre-heading waterlogging treatment was initiated 17 days after sowing to heading (TC. Post-heading waterlogging treatment was initiated heading till harvest (CT. Waterlogging treatment was initiated 17 days after sowing to harvesting (TT. The grain yield of P. miliaceum, S. glauca, and S. italica decreased 16, 18, and 4%, while that of P. sumatrense increased 210% under TT treatment and this showed P. sumatrense had most waterlogging tolerance. The grain yield was more affected under TC treatment in S. italica and P. miliaceum. However, there was not significant differences the grain yield between TC and CT treatment in P. sumatrense and S. glauca. Total dry weight, total root dry weight, number of crown root, and the proportion of lysigenous aerenchyma of P. sumatrense were significantly higher than those of other millets at harvesting. Plant growth rate, total root dry weight, number of crown root, and the proportion of lysigenous aerenchyma of P. sumatrense were significantly higher than those of other millets at heading. These results suggest that P. sumatrense exhibits waterlogging tolerance by enhancing root growth characterized by a high proportion of lysigenous aerenchyma in the crown root.

  11. Nano grained AZ31 alloy achieved by equal channel angular rolling process

    International Nuclear Information System (INIS)

    Hassani, F.Z.; Ketabchi, M.

    2011-01-01

    Equal channel angular rolling (ECAR) is a severe plastic deformation process which is carried out on large, thin sheets. The grain size could be significantly decreased by this process. The main purpose of this study is to investigate the possibility of grain refinement of AZ31 magnesium alloy sheet by this process to nanometer. The effect of the number of ECAR passes on texture evolution of AZ31 magnesium alloy was investigated. ECAR temperature was controlled to maximize the grain refinement efficiency along with preventing cracking. The initial microstructure of as-received AZ31 sheet showed an average grain size of about 21 μm. The amount of grain refinement increased with increasing the pass number. After 10 passes of the process, significant grain refinement occurred and the field emission scanning electron microscopic (FESEM) micrographs showed that the size of grains were decreased significantly to about 14-70 nm. These grains were formed at the grain boundaries and inside some of the previous larger micrometer grains. Observation of optical microstructures and X-ray diffraction patterns (XRD) showed the formation of twins after ECAR process. Micro-hardness of material was studied at room temperature. There was a continuous enhancement of hardness by increasing the pass number of ECAR process. At the 8th pass, hardness values increased by 53%. At final passes hardness reduced slightly, which was attributed to saturation of strain in high number of passes.

  12. The evolution of grain mantles and silicate dust growth at high redshift

    Science.gov (United States)

    Ceccarelli, Cecilia; Viti, Serena; Balucani, Nadia; Taquet, Vianney

    2018-05-01

    In dense molecular clouds, interstellar grains are covered by mantles of iced molecules. The formation of the grain mantles has two important consequences: it removes species from the gas phase and promotes the synthesis of new molecules on the grain surfaces. The composition of the mantle is a strong function of the environment that the cloud belongs to. Therefore, clouds in high-zeta galaxies, where conditions - like temperature, metallicity, and cosmic ray flux - are different from those in the Milky Way, will have different grain mantles. In the last years, several authors have suggested that silicate grains might grow by accretion of silicon-bearing species on smaller seeds. This would occur simultaneously with the formation of the iced mantles and be greatly affected by its composition as a function of time. In this work, we present a numerical study of the grain mantle formation in high-zeta galaxies, and we quantitatively address the possibility of silicate growth. We find that the mantle thickness decreases with increasing redshift, from about 120 to 20 layers for z varying from 0 to 8. Furthermore, the mantle composition is also a strong function of the cloud redshift, with the relative importance of CO, CO2, ammonia, methane, and methanol highly varying with z. Finally, being Si-bearing species always a very minor component of the mantle, the formation of silicates in molecular clouds is practically impossible.

  13. Quantitative Phase-Field Approach for Simulating Grain Growth in Anisotropic Systems with Arbitrary Inclination and Misorientation Dependence

    International Nuclear Information System (INIS)

    Moelans, N.; Blanpain, B.; Wollants, P.

    2008-01-01

    A phase-field approach for quantitative simulations of grain growth in anisotropic systems is introduced, together with a new methodology to derive appropriate model parameters that reproduce given misorientation and inclination dependent grain boundary energy and mobility in the simulations. The proposed model formulation and parameter choice guarantee a constant diffuse interface width and consequently give high controllability of the accuracy in grain growth simulations

  14. Front tracking based modeling of the solid grain growth on the adaptive control volume grid

    Science.gov (United States)

    Seredyński, Mirosław; Łapka, Piotr

    2017-07-01

    The paper presents the micro-scale model of unconstrained solidification of the grain immersed in under-cooled liquid, based on the front tracking approach. For this length scale, the interface tracked through the domain is meant as the solid-liquid boundary. To prevent generation of huge meshes the energy transport equation is discretized on the adaptive control volume (c.v.) mesh. The coupling of dynamically changing mesh and moving front position is addressed. Preliminary results of simulation of a test case, the growth of single grain, are presented and discussed.

  15. The use of thermally stimulated depolarization currents to study grain growth in ceramic thorium dioxide

    International Nuclear Information System (INIS)

    Muccillo, R.; Campos, L.L.

    1979-01-01

    Depolarization Current Spectra resulting from the destruction of the thermoelectret state in polycrystalline ThO 2 samples have been detected in the temperature range 100K-350K. The induced polarization is found to be due to migration of charge carriers over microscopic distances in the bulk of the specimens with trapping at grain boundaries. Moreover the density of charge carriers released from trapping sites, upon heating the cooled previously dc biased specimen decreases for increasing sintering temperature, suggesting the use of the technique to the study of grain growth in the bulk of ceramic oxides. (Author) [pt

  16. Grain growth effects on magnetic properties of Ni0.6Zn0.4Fe2O4 material prepared using mechanically alloyed nanoparticles

    Science.gov (United States)

    Syazwan, M. M.; Hapishah, A. N.; Azis, R. S.; Abbas, Z.; Hamidon, M. N.

    2018-06-01

    The effect of grain growth via sintering temperature on some magnetic properties is reported in this research. Ni0.6Zn0.4Fe2O4 nanoparticles were mechanically alloyed for 6 h and the sintering process starting from 600 to 1200 °C with 25 °C increment with only one sample subjected to all sintering scheme. The resulting change in the material was observed after each sintering. Single phase has been formed at 600 °C and above and the intensity peaks increased with sintering temperature as well as crystallinity increment. The morphological studies showed grain size increment as the sintering temperature increased. Moreover, the density increased while the porosity decreased with increasing sintering temperature. The saturation induction, Bs increased with the increased of grain size. On the other hand, the coercivity-vs-grain size plot reveals the critical single-domain-to-multidomain grain size to be about ∼400 nm. The initial permeability, μi value was increased with grain size enhancement. The microstructural grain growth, as exposed for the first time by this research, is shown as a process of multiple activation energy barriers.

  17. Texture development due to preferential grain growth of Ho--Ba--Cu--O in 1.6-T magnetic field

    International Nuclear Information System (INIS)

    Holloway, A.; McCallum, R.W.; Arrasmith, S.R.

    1993-01-01

    It has been experimentally observed that the application of even a relatively weak magnetic field of 1.6-T during sintering of HoBa 2 Cu 3 O 7-δ (hereafter HoBCO) results in a significant degree of grain alignment. The orientation of grains is found to be controlled by the direction and magnitude of a magnetic field. The degree of alignment was monitored by x-ray diffraction measurements on the flat surface of the samples and by metallography. It has been observed that the degree of alignment grows as the magnitude of the field increases between 0 and 1.6 T for a fixed temperature and processing time. The degree of alignment also increases when the processing temperature changes from 930 degree C to 965 degree C for a fixed field and time. It has also been observed that for both a fixed field and processing temperature, the alignment grows when the processing time increases between 16 and 72 hours. Metallography measurements on the flat and cross-sectional parts of the samples showed that the texture propagates into the bulk of the samples. In the presence of a sufficient amount of the liquid phase, the enhancement of the grain growth in the direction favorable to the magnetic field produces rather large single-crystals (0.3 to 0.5 mm linear size) within the sample

  18. Effect of Deforming Temperature and Strain on Abnormal Grain Growth of Extruded FGH96 Superalloy

    Directory of Open Access Journals (Sweden)

    WANG Chaoyuan

    2016-10-01

    Full Text Available Based on the experiments of isothermal forging wedge-shaped samples, Deform-3D numerical simulation software was used to confirm the strain distribution in the wedge-shaped samples. The effect of deforming temperature and strain on abnormal grain growth(AGG in extruded FGH96 superalloy was examined. It is found that when the forging speed is 0.04 mm/s,the critical AGG occurring temperature is 1100℃,and the critical strain is 2%.AGG does not occur within 1000-1070℃,but still shows the feature of ‘critical strain’,and the region with strain of 5%-10% has the largest average grain size.AGG can be avoided and the uniform fine grains can be gained when the strain is not less than 15%.

  19. Creep crack growth by grain boundary cavitation under monotonic and cyclic loading

    Science.gov (United States)

    Wen, Jian-Feng; Srivastava, Ankit; Benzerga, Amine; Tu, Shan-Tung; Needleman, Alan

    2017-11-01

    Plane strain finite deformation finite element calculations of mode I crack growth under small scale creep conditions are carried out. Attention is confined to isothermal conditions and two time histories of the applied stress intensity factor: (i) a monononic increase to a plateau value subsequently held fixed; and (ii) a cyclic time variation. The crack growth calculations are based on a micromechanics constitutive relation that couples creep deformation and damage due to grain boundary cavitation. Grain boundary cavitation, with cavity growth due to both creep and diffusion, is taken as the sole failure mechanism contributing to crack growth. The influence on the crack growth rate of loading history parameters, such as the magnitude of the applied stress intensity factor, the ratio of the applied minimum to maximum stress intensity factors, the loading rate, the hold time and the cyclic loading frequency, are explored. The crack growth rate under cyclic loading conditions is found to be greater than under monotonic creep loading with the plateau applied stress intensity factor equal to its maximum value under cyclic loading conditions. Several features of the crack growth behavior observed in creep-fatigue tests naturally emerge, for example, a Paris law type relation is obtained for cyclic loading.

  20. Ultrafine grained steels processed by equal channel angular pressing

    International Nuclear Information System (INIS)

    Shin, Dong Hyuk; Park, Kyung-Tae

    2005-01-01

    Recent development of ultrafine grained (UFG) low carbon steels by using equal channel angular pressing (ECAP) and their room temperature tensile properties are reviewed, focusing on the strategies overcoming their inherent mechanical drawbacks. In addition to ferrite grain refinement, when proper post heat treatments are imposed, carbon atom dissolution from pearlitic cementite during ECAP can be utilized for microstructural modification such as uniform distribution of nano-sized cementite particles or microalloying element carbides inside UFG ferrite grains and fabrication of UFG ferrite/martensite dual phase steel. The utilization of nano-sized particles is effective on improving thermal stability of UFG low carbon ferrite/pearlite steel but less effective on improving its tensile properties. By contrast, UFG ferrite/martensite dual phase steel exhibits an excellent combination of ultrahigh strength, large uniform elongation and extensive strain hardenability

  1. Processing, microstructure and properties of grain-oriented ferroelectric ceramics

    International Nuclear Information System (INIS)

    Okazaki, K.; Igarashi, H.; Nagata, K.; Yamamoto, T.; Tashiro, S.

    1986-01-01

    Grain oriented ferroelectric ceramics such as PbBi/sub 2/Nb/sub 2/O/sub 9/, bismuth compound with layer structure, (PbLa)Nb/sub 2/O/sub 6/, tungsten-bronze structure and SbSI were prepared by an uni-axial hot-pressing, a double-stage hot-pressing and tape casting methods. Microstructures of them were examined by SEM and the prefered textures of the ceramics composed of thin plate and/or needle crystallites were ascertained. Grain orientation effects on electrical, piezoelectric, optical and mechanical properties are discussed

  2. Proteomic analysis of maize grain development using iTRAQ reveals temporal programs of diverse metabolic processes.

    Science.gov (United States)

    Yu, Tao; Li, Geng; Dong, Shuting; Liu, Peng; Zhang, Jiwang; Zhao, Bin

    2016-11-04

    Grain development in maize is an essential process in the plant's life cycle and is vital for use of the plant as a crop for animals and humans. However, little is known regarding the protein regulatory networks that control grain development. Here, isobaric tag for relative and absolute quantification (iTRAQ) technology was used to analyze temporal changes in protein expression during maize grain development. Maize grain proteins and changes in protein expression at eight developmental stages from 3 to 50 d after pollination (DAP) were performed using iTRAQ-based proteomics. Overall, 4751 proteins were identified; 2639 of these were quantified and 1235 showed at least 1.5-fold changes in expression levels at different developmental stages and were identified as differentially expressed proteins (DEPs). The DEPs were involved in different cellular and metabolic processes with a preferential distribution to protein synthesis/destination and metabolism categories. A K-means clustering analysis revealed coordinated protein expression associated with different functional categories/subcategories at different development stages. Our results revealed developing maize grain display different proteomic characteristics at distinct stages, such as numerous DEPs for cell growth/division were highly expressed during early stages, whereas those for starch biosynthesis and defense/stress accumulated in middle and late stages, respectively. We also observed coordinated expression of multiple proteins of the antioxidant system, which are essential for the maintenance of reactive oxygen species (ROS) homeostasis during grain development. Particularly, some DEPs, such as zinc metallothionein class II, pyruvate orthophosphate dikinase (PPDK) and 14-3-3 proteins, undergo major changes in expression at specific developmental stages, suggesting their roles in maize grain development. These results provide a valuable resource for analyzing protein function on a global scale and also

  3. Effect of Fungicide Applications on Grain Sorghum (Sorghum bicolor L. Growth and Yield

    Directory of Open Access Journals (Sweden)

    Dan D. Fromme

    2017-01-01

    Full Text Available Field studies were conducted in the upper Texas Gulf Coast and in central Louisiana during the 2013 through 2015 growing seasons to evaluate the effects of fungicides on grain sorghum growth and development when disease pressure was low or nonexistent. Azoxystrobin and flutriafol at 1.0 L/ha and pyraclostrobin at 0.78 L/ha were applied to the plants of two grain sorghum hybrids (DKS 54-00, DKS 53-67 at 25% bloom and compared with the nontreated check for leaf chlorophyll content, leaf temperature, and plant lodging during the growing season as well as grain mold, test weight, yield, and nitrogen and protein content of the harvested grain. The application of a fungicide had no effect on any of the variables tested with grain sorghum hybrid responses noted. DKS 53-67 produced higher yield, greater test weight, higher percent protein, and N than DKS 54-00. Results of this study indicate that the application of a fungicide when little or no disease is present does not promote overall plant health or increase yield.

  4. Three-dimensional cellular automaton-finite element modeling of solidification grain structures for arc-welding processes

    International Nuclear Information System (INIS)

    Chen, Shijia; Guillemot, Gildas; Gandin, Charles-André

    2016-01-01

    Solidification grain structure has significant impact on the final properties of welded parts using fusion welding processes. Direct simulation of grain structure at industrial scale is yet rarely reported in the literature and remains a challenge. A three-dimensional (3D) coupled Cellular Automaton (CA) – Finite Element (FE) model is presented that predicts the grain structure formation during multiple passes Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW). The FE model is established in a level set (LS) approach that tracks the evolution of the metal-shielding gas interface due to the addition of metal. The FE method solves the mass, energy and momentum conservation equations for the metal plus shielding gas system based on an adaptive mesh (FE mesh). Fields are projected in a second FE mesh, named CA mesh. A CA grid made of a regular lattice of cubic cells is created to overlay the fixed CA mesh. The CA model based on the CA grid simulates the melting and growth of the grain boundaries in the liquid pool. In order to handle large computational domains while keeping reasonable computational costs, parallel computations and dynamic strategies for the allocation/deallocation of the CA grid are introduced. These strategies correspond to significant optimizations of the computer memories that are demonstrated. The 3D CAFE model is first applied to the simple configuration of single linear passes by GTAW of a duplex stainless steel URANUS 2202. It is then applied to a more persuasive example considering GMAW in spray transfer mode during multiple passes to fill a V-groove chamfer. Simulations reveal the possibility to handle domains with millions of grains in representative domain sizes while following the formation of textures that result from the growth competition among columnar grains. -- Graphical abstract: Simulated 3D grain structure (3D CAFE model) for GTAW multiple linear passes at the surface of a duplex stainless steel (URANUS 22002

  5. Composition and microstructure alteration of triticale grain surface after processing by enzymes of cellulase complex

    Directory of Open Access Journals (Sweden)

    Elena Kuznetsova

    2016-01-01

    Full Text Available It is found that the pericarp tissue of grain have considerable strength and stiffness, that has an adverse effect on quality of whole-grain bread. Thereby, there exists the need for preliminary chemical and biochemical processing of durable cell walls before industrial use. Increasingly used in the production of bread finds an artificial hybrid of the traditional grain crops of wheat and rye - triticale, grain which has high nutritional value. The purpose of this research was to evaluate the influence of cellulose complex (Penicillium canescens enzymes on composition and microstructure alteration of triticale grain surface, for grain used in baking. Triticale grain was processed by cellulolytic enzyme preparations with different composition (producer is Penicillium canescens. During experiment it is found that triticale grain processing by enzymes of cellulase complex leads to an increase in the content of water-soluble pentosans by 36.3 - 39.2%. The total amount of low molecular sugars increased by 3.8 - 10.5 %. Studies show that under the influence of enzymes the microstructure of the triticale grain surface is changing. Microphotographs characterizing grain surface structure alteration in dynamic (every 2 hours during 10 hours of substrate hydrolysis are shown. It is found that the depth and direction of destruction process for non-starch polysaccharides of grain integument are determined by the composition of the enzyme complex preparation and duration of exposure. It is found, that xylanase involved in the modification of hemicelluloses fiber having both longitudinal and radial orientation. Hydrolysis of non-starch polysaccharides from grain shells led to increase of antioxidant activity. Ferulic acid was identified in alcoholic extract of triticale grain after enzymatic hydrolysis under the influence of complex preparation containing cellulase, xylanase and β-glucanase. Grain processing by independent enzymes containing in complex

  6. Process for the preparation of fine grain metal carbide powders

    International Nuclear Information System (INIS)

    Gortsema, F.P.

    1976-01-01

    Fine grain metal carbide powders are conveniently prepared from the corresponding metal oxide by heating in an atmosphere of methane in hydrogen. Sintered articles having a density approaching the theoretical density of the metal carbide itself can be fabricated from the powders by cold pressing, hot pressing or other techniques. 8 claims, no drawings

  7. DUST PROPERTIES AND DISK STRUCTURE OF EVOLVED PROTOPLANETARY DISKS IN Cep OB2: GRAIN GROWTH, SETTLING, GAS AND DUST MASS, AND INSIDE-OUT EVOLUTION

    International Nuclear Information System (INIS)

    Sicilia-Aguilar, Aurora; Henning, Thomas; Dullemond, Cornelis P.; Bouwman, Jeroen; Sturm, Bernhard; Patel, Nimesh; Juhász, Attila

    2011-01-01

    We present Spitzer/Infrared Spectrograph spectra of 31 T Tauri stars (TTS) and IRAM/1.3 mm observations for 34 low- and intermediate-mass stars in the Cep OB2 region. Including our previously published data, we analyze 56 TTS and 3 intermediate-mass stars with silicate features in Tr 37 (∼4 Myr) and NGC 7160 (∼12 Myr). The silicate emission features are well reproduced with a mixture of amorphous (with olivine, forsterite, and silica stoichiometry) and crystalline grains (forsterite, enstatite). We explore grain size and disk structure using radiative transfer disk models, finding that most objects have suffered substantial evolution (grain growth, settling). About half of the disks show inside-out evolution, with either dust-cleared inner holes or a radially dependent dust distribution, typically with larger grains and more settling in the innermost disk. The typical strong silicate features nevertheless require the presence of small dust grains, and could be explained by differential settling according to grain size, anomalous dust distributions, and/or optically thin dust populations within disk gaps. M-type stars tend to have weaker silicate emission and steeper spectral energy distributions than K-type objects. The inferred low dust masses are in a strong contrast with the relatively high gas accretion rates, suggesting global grain growth and/or an anomalous gas-to-dust ratio. Transition disks in the Cep OB2 region display strongly processed grains, suggesting that they are dominated by dust evolution and settling. Finally, the presence of rare but remarkable disks with strong accretion at old ages reveals that some very massive disks may still survive to grain growth, gravitational instabilities, and planet formation.

  8. Fission gas release and grain growth in THO2-UO2 fuel irradiated at high temperature

    International Nuclear Information System (INIS)

    Goldberg, I.; Waldman, L.A.; Giovengo, J.F.; Campbell, W.R.

    1979-01-01

    Data are presented on fission gas release and grain growth in ThO 2 -UO 2 fuels irradiated as part of the LWBR fuel element development program. These data for rods that experienced peak linear power outputs ranging from 15 to 22 KW/ft supplement fission gas release data previously reported for 51 rods containing ThO 2 and ThO 2 -UO 2 fuel irradiated at peak linear powers predominantly below 14 KW/ft. Fission gas release was relatively high (up to 15.0 percent) for the rods operated at high power in contrast to the relatively low fission gas release (0.1 to 5.2 percent) measured for the rods operated at lower power. Metallographic examination revealed extensive equiaxed grain growth in the fuel at the high power axial locations of the three rods

  9. Graphene growth process modeling: a physical-statistical approach

    Science.gov (United States)

    Wu, Jian; Huang, Qiang

    2014-09-01

    As a zero-band semiconductor, graphene is an attractive material for a wide variety of applications such as optoelectronics. Among various techniques developed for graphene synthesis, chemical vapor deposition on copper foils shows high potential for producing few-layer and large-area graphene. Since fabrication of high-quality graphene sheets requires the understanding of growth mechanisms, and methods of characterization and control of grain size of graphene flakes, analytical modeling of graphene growth process is therefore essential for controlled fabrication. The graphene growth process starts with randomly nucleated islands that gradually develop into complex shapes, grow in size, and eventually connect together to cover the copper foil. To model this complex process, we develop a physical-statistical approach under the assumption of self-similarity during graphene growth. The growth kinetics is uncovered by separating island shapes from area growth rate. We propose to characterize the area growth velocity using a confined exponential model, which not only has clear physical explanation, but also fits the real data well. For the shape modeling, we develop a parametric shape model which can be well explained by the angular-dependent growth rate. This work can provide useful information for the control and optimization of graphene growth process on Cu foil.

  10. Numerical simulation of temperature distribution using finite difference equations and estimation of the grain size during friction stir processing

    International Nuclear Information System (INIS)

    Arora, H.S.; Singh, H.; Dhindaw, B.K.

    2012-01-01

    Highlights: ► Magnesium alloy AE42 was friction stir processed under different cooling conditions. ► Heat flow model was developed using finite difference heat equations. ► Generalized MATLAB code was developed for solving heat flow model. ► Regression equation for estimation of grain size was developed. - Abstract: The present investigation is aimed at developing a heat flow model to simulate temperature history during friction stir processing (FSP). A new approach of developing implicit form of finite difference heat equations solved using MATLAB code was used. A magnesium based alloy AE42 was friction stir processed (FSPed) at different FSP parameters and cooling conditions. Temperature history was continuously recorded in the nugget zone during FSP using data acquisition system and k type thermocouples. The developed code was validated at different FSP parameters and cooling conditions during FSP experimentation. The temperature history at different locations in the nugget zone at different instants of time was further utilized for the estimation of grain growth rate and final average grain size of the FSPed specimen. A regression equation relating the final grain size, maximum temperature during FSP and the cooling rate was developed. The metallurgical characterization was done using optical microscopy, SEM, and FIB-SIM analysis. The simulated temperature profiles and final average grain size were found to be in good agreement with the experimental results. The presence of fine precipitate particles generated in situ in the investigated magnesium alloy also contributed in the evolution of fine grain structure through Zener pining effect at the grain boundaries.

  11. Densification and Grain Growth during Early-stage Sintering of Ce0.9Gd0.1O1.95-δ in Reducing Atmosphere

    DEFF Research Database (Denmark)

    He, Zeming; Yuan, Hao; Glasscock, Julie

    2010-01-01

    The present work investigates the processes of densification and grain growth of Ce0.9Gd0.1O1.95-δ (CGO10) during sintering in reducing atmosphere. Sintering variables were experimentally characterized and analyzed using defect chemistry and sintering constitutive laws. Based on the achieved...

  12. Contribution to the study of the creep of uranium dioxide. Role of grain growth promoters

    International Nuclear Information System (INIS)

    Vivant-Duguay, Christelle

    1998-01-01

    Improvement of nuclear fuel performances involves enhancing the plasticity of uranium dioxide UO 2 , in order to reduce the stress applied by the pellet to the cladding during a power ramp. The objective of this work is to identify and to formulate the effects produced by the nature and the concentration of additives of corundum structure, Cr 2 O 3 or Al 2 O 3 , which are grain growth promoters for UO 2 . The review of literature data establishes that oxygen content, grain size or porosity markedly affect the mechanical properties of uranium dioxide. On the other hand, there is relatively little reported work on the influence of doping. Prepared samples have been deformed by uniaxial compression. In the case of standard undoped UO 2 , two distinct preponderant creep mechanisms occur depending on stress level: a grain boundary diffusional creep, as per Coble, for stresses below the transition stress and a dislocation creep above. The doped materials have a large grained microstructure, which allows a dislocation creep only. In the range of temperature and stress investigated here, doping significantly improves the plasticity of standard UO 2 . This common effect of dopants is characterized by a decrease in the flow stress for tests with constant strain rate and by enhanced steady-state creep rates. Cr 2 O 3 doping is the more effective. The apparent benefit of doping results from the gain due to the increased grain size, but it is compensated by the strengthening effect of the additive. The creep law used to describe the behavior of standard UO 2 , has been modified to account for the influence of the dopant, by including either the concentration or the grain size. (author) [fr

  13. Experimental studies of Micro- and Nano-grained UO2: Grain Growth Behavior, Sufrace Morphology, and Fracture Toughness

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States); Mo, Kun [Argonne National Lab. (ANL), Argonne, IL (United States); Jamison, Laura M. [Argonne National Lab. (ANL), Argonne, IL (United States); Lian, Jie [Rensselaer Polytechnic Inst., Troy, NY (United States); Yao, Tiankai [Rensselaer Polytechnic Inst., Troy, NY (United States); Bhattacharya, Sumit [Argonne National Lab. (ANL), Argonne, IL (United States); Northwestern Univ., Evanston, IL (United States)

    2016-01-01

    This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructure-based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize the experimental efforts in FY16 including the following important experiments: (1) in-situ grain growth measurement of nano-grained UO2; (2) investigation of surface morphology in micrograined UO2; (3) Nano-indentation experiments on nano- and micro-grained UO2. The highlight of this year is: we have successfully demonstrated our capability to in-situ measure grain size development while maintaining the stoichiometry of nano-grained UO2 materials; the experiment is, for the first time, using synchrotron X-ray diffraction to in-situ measure grain growth behavior of UO2.

  14. Additional grain refinement in recrystallization controlled rolling of Ti-microalloyed steels processed by near-net-shape casting technology

    International Nuclear Information System (INIS)

    Arribas, M.; Lopez, B.; Rodriguez-Ibabe, J.M.

    2008-01-01

    This paper analyzes the recrystallization kinetics in Ti-microalloyed steels processed using 'beam blank' casting technology. The faster solidification rates associated with this technology brings a finer precipitation of TiN particles which are very effective in controlling austenite grain growth during hot working. Furthermore, these small precipitates have been shown to delay static and dynamic recrystallization. The finer the precipitates the higher the delay in recrystallization. Nevertheless, beyond particle size and distribution, the level of delay is very dependent on microstructure (above all austenite grain size) and deformation conditions (strain and temperature). This paper studies the effects of this recrystallization delay on the microstructure evolution during hot rolling. Special attention was paid to the study of the occurrence of partial recrystallization during the final stages of rolling, which could lead to the presence of mixed microstructures before transformation. The possibility of achieving an additional austenite grain size refinement prior to transformation was evaluated

  15. Effects of Sb-doping on the grain growth of Cu(In, Ga)Se2 thin films fabricated by means of single-target sputtering

    International Nuclear Information System (INIS)

    Zhang, Shu; Wu, Lu; Yue, Ruoyu; Yan, Zongkai; Zhan, Haoran; Xiang, Yong

    2013-01-01

    To investigate the effects of Sb doping on the kinetics of grain growth in Cu(In,Ga)Se 2 (CIGS) thin films during annealing, CIGS thin films were sputtered onto Mo coated substrates from a single CIGS alloy target, followed by chemical bath deposition of Sb 2 S 3 thin layers on top of CIGS layers and subsequent annealing at different temperatures for 30 min in Se vapors. X-ray diffraction results showed that CIGS thin films were obtained directly using the single-target sputtering method. After annealing, the In/Ga ratio in Sb-doped CIGS thin films remained stable compared to undoped film, possibly because Sb can promote the incorporation of Ga into CIGS. The grain growth in CIGS thin films was enhanced after Sb doping, exhibiting significantly larger grains after annealing at 400 °C or 450 °C compared to films without Sb. In particular, the effect was strikingly significant in grain growth across the film thickness, resulting in columnar grain structure in Sb-doped films. This grain growth improvement may be led by the diffusion of Sb from the front surface to the CIGS-Mo back interface, which promoted the mass transport process in CIGS thin films. - Highlights: ► Cu(In,Ga)Se 2 (CIGS) thin films made by sputtering from a single CIGS target. ► Chemical bath deposition used to introduce antimony into CIGS absorber layers. ► In/Ga ratio decreases in Sb-doped annealed films, comparatively to undoped films. ► Sb-doped CIGS films are superior to undoped films in terms of grain-growth kinetics

  16. Why do interstellar grains exist

    International Nuclear Information System (INIS)

    Seab, C.G.; Hollenbach, D.J.; Mckee, C.F.; Tielens, A.G.G.M.

    1986-01-01

    There exists a discrepancy between calculated destruction rates of grains in the interstellar medium and postulated sources of new grains. This problem was examined by modelling the global life cycle of grains in the galaxy. The model includes: grain destruction due to supernovae shock waves; grain injection from cool stars, planetary nebulae, star formation, novae, and supernovae; grain growth by accretion in dark clouds; and a mixing scheme between phases of the interstellar medium. Grain growth in molecular clouds is considered as a mechanism or increasing the formation rate. To decrease the shock destruction rate, several new physical processes, such as partial vaporization effects in grain-grain collisions, breakdown of the small Larmor radius approximation for betatron acceleration, and relaxation of the steady-state shock assumption are included

  17. Mechanisms of dust grain charging in plasma with allowance for electron emission processes

    Energy Technology Data Exchange (ETDEWEB)

    Mol’kov, S. I.; Savin, V. N., E-mail: moped@onego.ru [Petrozavodsk State University (Russian Federation)

    2017-02-15

    The process of dust grain charging is described with allowance for secondary, ion-induced, photoelectric, and thermal electron emission from the grain surface. The roughness of the grain surface is taken into account. An intermediate charging regime involving ion–atom collisions and electron ionization in the perturbed plasma region is analyzed using the moment equations and Poisson’s equation. A calculation method is proposed that allows one to take into account the influence of all the above effects and determine the radius of the plasma region perturbed by the dust grain.

  18. Repeated growth and bubbling transfer of graphene with millimetre-size single-crystal grains using platinum.

    Science.gov (United States)

    Gao, Libo; Ren, Wencai; Xu, Huilong; Jin, Li; Wang, Zhenxing; Ma, Teng; Ma, Lai-Peng; Zhang, Zhiyong; Fu, Qiang; Peng, Lian-Mao; Bao, Xinhe; Cheng, Hui-Ming

    2012-02-28

    Large single-crystal graphene is highly desired and important for the applications of graphene in electronics, as grain boundaries between graphene grains markedly degrade its quality and properties. Here we report the growth of millimetre-sized hexagonal single-crystal graphene and graphene films joined from such grains on Pt by ambient-pressure chemical vapour deposition. We report a bubbling method to transfer these single graphene grains and graphene films to arbitrary substrate, which is nondestructive not only to graphene, but also to the Pt substrates. The Pt substrates can be repeatedly used for graphene growth. The graphene shows high crystal quality with the reported lowest wrinkle height of 0.8 nm and a carrier mobility of greater than 7,100 cm(2) V(-1) s(-1) under ambient conditions. The repeatable growth of graphene with large single-crystal grains on Pt and its nondestructive transfer may enable various applications.

  19. Modeling Nucleation and Grain Growth in the Solar Nebula: Initial Progress Report

    Science.gov (United States)

    Nuth, Joseph A.; Paquette, J. A.; Ferguson, F. T.

    2010-01-01

    The primitive solar nebula was a violent and chaotic environment where high energy collisions, lightning, shocks and magnetic re-connection events rapidly vaporized some fraction of nebular dust, melted larger particles while leaving the largest grains virtually undisturbed. At the same time, some tiny grains containing very easily disturbed noble gas signatures (e.g., small, pre-solar graphite or SiC particles) never experienced this violence, yet can be found directly adjacent to much larger meteoritic components (chondrules or CAIs) that did. Additional components in the matrix of the most primitive carbonaceous chondrites and in some chondritic porous interplanetary dust particles include tiny nebular condensates, aggregates of condensates and partially annealed aggregates. Grains formed in violent transient events in the solar nebula did not come to equilibrium with their surroundings. To understand the formation and textures of these materials as well as their nebular abundances we must rely on Nucleation Theory and kinetic models of grain growth, coagulation and annealing. Such models have been very uncertain in the past: we will discuss the steps we are taking to increase their reliability.

  20. CONSTRAINTS ON THE RADIAL VARIATION OF GRAIN GROWTH IN THE AS 209 CIRCUMSTELLAR DISK

    International Nuclear Information System (INIS)

    Pérez, Laura M.; Carpenter, John M.; Isella, Andrea; Ricci, Luca; Sargent, Anneila I.; Chandler, Claire J.; Andrews, Sean M.; Harris, Robert J.; Calvet, Nuria; Corder, Stuartt A.; Deller, Adam T.; Dullemond, Cornelis P.; Linz, Hendrik; Greaves, Jane S.; Henning, Thomas; Kwon, Woojin; Lazio, Joseph; Mundy, Lee G.; Storm, Shaye; Testi, Leonardo

    2012-01-01

    We present dust continuum observations of the protoplanetary disk surrounding the pre-main-sequence star AS 209, spanning more than an order of magnitude in wavelength from 0.88 to 9.8 mm. The disk was observed with subarcsecond angular resolution (0.''2-0.''5) to investigate radial variations in its dust properties. At longer wavelengths, the disk emission structure is notably more compact, providing model-independent evidence for changes in the grain properties across the disk. We find that physical models which reproduce the disk emission require a radial dependence of the dust opacity κ ν . Assuming that the observed wavelength-dependent structure can be attributed to radial variations in the dust opacity spectral index (β), we find that β(R) increases from β 1.5 for R ∼> 80 AU, inconsistent with a constant value of β across the disk (at the 10σ level). Furthermore, if radial variations of κ ν are caused by particle growth, we find that the maximum size of the particle-size distribution (a max ) increases from submillimeter-sized grains in the outer disk (R ∼> 70 AU) to millimeter- and centimeter-sized grains in the inner disk regions (R ∼ max (R) with predictions from physical models of dust evolution in protoplanetary disks. For the dust composition and particle-size distribution investigated here, our observational constraints on a max (R) are consistent with models where the maximum grain size is limited by radial drift.

  1. Analysis of grain filling process to the varied meteorological conditions in winter wheat [Triticum aestivum] cultivars

    International Nuclear Information System (INIS)

    Inoue, K.; Nakazono, K.; Wakiyama, Y.

    2005-01-01

    This paper describes effects of varied meteorological conditions on the grain filling periods, stabilities of yield and quality of winter wheat cultivars with different maturity characteristics (cv. Ayahikari, Norin61, Bandowase, and Tsurupikari). In the field experiments, the meteorological treatments were made during the first heading time on 17 April 2001 and the middle heading time on 24 April 2000. Air temperature, global solar radiation and soil moisture were controlled using a rain shelter, cheesecloth and irrigation system. The growth speed and growth period of wheat grains varied among four winter wheat cultivars, depending on meteorological conditions. The growth speed increased within 1 8.4 deg C of mean air temperature over the 30 days after the anthesis. On the other hand, it was found that the growth speed of wheat grains and the maximum number of wheat grains (Ymax) decreased greatly with the 44.4% interception of global solar radiation. Logistic functions were fitted to the relationship between the relative thousand-kernel-weight (Y/Ymax) and the total integrated temperature (sigmaTa) after heading for all treatment conditions. The maximum weight of grains (Ymax) achieved at the harvest time varied somewhat clearly among four winter wheat cultivars and meteorological conditions. Multiple regression analysis showed that the grain yield (Ymax) of four wheat cultivars correlated positively with daily mean solar radiation. It was also found that the cultivar Ayahikari had a highly significant negative correlation between its grain weight and soil moisture. Namely, the grain weight of high soil moisture plot with pF=1.5 was lower by about 9% than that of a control plot with pF=3.5. On the other hand, the grain yield of cultivar Norin61 responded inversely to a wet environment, indicating that its grain weight was higher for high soil moisture and high wet-bulb temperature than for a dry environment. The grain yield of early varieties of Bandowase and

  2. Finite-Element Thermal Analysis and Grain Growth Behavior of HAZ on Argon Tungsten-Arc Welding of 443 Stainless Steel

    Directory of Open Access Journals (Sweden)

    Yichen Wang

    2016-03-01

    Full Text Available This paper presents a numerical and infrared experimental study of thermal and grain growth behavior during argon tungsten arc welding of 443 stainless steel. A 3D finite element model was proposed to simulate the welding process. The simulations were carried out via the Ansys Parametric Design Language (APDL available in the finite-element code, ANSYS. To validate the simulation accuracy, a series of experiments using a fully-automated welding process was conducted. The results of the numerical analysis show that the simulation weld bead size and the experiment results have good agreement. The grain growth in the heat-affected zone of 443 stainless steel is influenced via three factors: (1 the thermal cycle experienced; (2 grain boundary migration; and (3 particle precipitation. Grain boundary migration is the main factor. The modified coefficient k of the grain growth index is calculated. The value is 1.16. Moreover, the microhardness of the weld bead softened slightly compared to the base metal.

  3. CH3NH3PbI3 grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

    Science.gov (United States)

    Yao, Zhibo; Wang, Wenli; Shen, Heping; Zhang, Ye; Luo, Qiang; Yin, Xuewen; Dai, Xuezeng; Li, Jianbao; Lin, Hong

    2017-12-01

    Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C(PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C(PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

  4. Use of a multifunctional column for the determination of deoxynivalenol in grains, grain products, and processed foods.

    Science.gov (United States)

    Bao, Lei; Oles, Carolyn J; White, Kevin D; Sapp, Chelsea; Trucksess, Mary W

    2011-01-01

    Deoxynivalenol (DON), also known as vomitoxin, belongs to a class of naturally occurring mycotoxins produced by Fusarium spp. DON, 12, 13-epoxy-3,7 trihydroxytrichothec-9-en-8-one, is one of the most frequently detected mycotoxins in agricultural commodities worldwide. A method consisting of extraction, filtration, column cleanup, and RP-HPLC-UV separation and quantitation was validated for the determination of DON in grains (rice and barley), grain products (whole wheat flour, white flour, wheat germ, and wheat bran), and processed foods (bread, breakfast cereals, and pretzels). A 25 g test portion was extracted with 100 mL acetonitrile-water (84 + 16, v/v). After blending for 3 min, the supernatant was applied to a multifunctional column (MycoSep 225). The purified filtrate (2 mL) was evaporated to dryness and redissolved in the mobile phase. The toxins were then subjected to RP-HPLC-UV analysis. The accuracy and repeatability characteristics of the method were determined. Recoveries of DON added at levels ranging from 0.5 to 1.5 microg/g for all test matrixes were from 75 to 98%. SD and RSD(r) ranged from 0.7 to 11.6% and 0.9 to 12.7%, respectively. Within-laboratory HorRat values were from 0.1 to 0.7 for all matrixes analyzed. The method was found to meet AOAC method performance criteria for grains, grain products, and processed foods. The identity of DON in naturally contaminated test sample extracts was confirmed by HPLC/MS/MS analysis.

  5. Columnar grain growth of FePt(L10) thin films

    International Nuclear Information System (INIS)

    Yang En; Ho Hoan; Laughlin, David E.; Zhu Jiangang

    2012-01-01

    An experimental approach for obtaining perpendicular FePt-SiOx thin films with a large height to diameter ratio FePt(L1 0 ) columnar grains is presented in this work. The microstructure for FePt-SiOx composite thin films as a function of oxide volume fraction, substrate temperature, and film thickness is studied by plan view and cross section TEM. The relations between processing, microstructure, epitaxial texture, and magnetic properties are discussed. By tuning the thickness of the magnetic layer and the volume fraction of oxide in the film at a sputtering temperature of 410 deg. C, a 16 nm thick perpendicular FePt film with ∼8 nm diameter of FePt grains was obtained. The height to diameter ratio of the FePt grains was as large as 2. Ordering at lower temperature can be achieved by introducing a Ag sacrificial layer.

  6. Grain Formation Processes in Oxygen-Rich Circumstellar Outflows: Testing the Metastable Eutectic Condensation Hypothesis and Measuring Atom-Grain & Grain-Grain Sticking Coefficients (A Sub-orbital Investigation)

    Science.gov (United States)

    Nuth, Joseph

    An experimentally-based model of grain formation in oxygen-rich circumstellar outflows that includes vapor-solid nucleation, grain growth, thermal annealing and grain aggregation in sufficient detail to predict the spectral energy distribution (SED) of the shells for comparison with observations of a wide range of stellar sources still lacks critical data. In order to gather this data we propose to conduct a series of laboratory experiments using our proven experimental system and microgravity condensation, growth and grain aggregation experiments on sounding rockets with a flight-proven payload provided by Dr. Yuki Kimura of Hokkaido University. We have proposed that solids from a hydrogen-rich, supersaturated, Fe-Mg-SiO vapor condense at metastable eutectic points in this ternary phase diagram. Because the FeOMgO system is totally miscible (has no eutectic or metastable eutectic compositions), this predicts that condensates will be pure Mg-silicate or Fe-silicate grains and that no primary condensate will be a mixed Fe-Mg-silicate. We have shown that this observation leads to a logical explanation as to why pure magnesium olivine and enstatite minerals are detected in circumstellar winds rather than the mixed Mg-Fe-silicate grains that might otherwise be expected (Rietmeijer, Nuth & Karner, 1999). This simplifying hypothesis has been built into our models of circumstellar condensation and growth. However, these experimental results require confirmation and testing since they should apply to other, quite similar condensable systems. We propose to test this hypothesis by condensing solids from the Fe-Mg-AlO ternary vapor system. Since FeO-MgO miscibility also applies to this system, the primary condensates from such a vapor should consist of pure amorphous Fe-aluminates and Mg-aluminates. No mixed Fe-Mg-spinels should be detected as primary condensates if this hypothesis is correct, just as none were detected for the FeO-MgO-SiO system. Confirmation of this

  7. Effects of seed orientation on the growth behavior of single grain REBCO bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hee Gyoun [Korea Polytechnic University, Siheung (Korea, Republic of)

    2017-06-15

    This study presents a simple method to control the seed orientation which leads to the various growth characteristics of a single grain REBCO (RE: rare-earth elements) bulk superconductors. Seed orientation was varied systematically from c-axis to a-axis with every 30 degree rotation around b-axis. Orientations of a REBCO single grain was successfully controlled by placing the seed with various angles on the prismatic indent prepared on the surface of REBCO powder compacts. Growth pattern was changed from cubic to rectangular when the seed orientation normal to compact surface was varied from c-axis to a-axis. Macroscopic shape change has been explained by the variation of the wetting angle of un-reacted melt depending on the interface energy between YBa2Cu3O7-y (Y123) grain and melt. Higher magnetic levitation force was obtained for the specimen prepared using tilted seed with an angle of 30 degree rotation around b-axis.

  8. Mitigating Abnormal Grain Growth for Friction Stir Welded Al-Li 2195 Spun Formed Domes

    Science.gov (United States)

    Chen, Po-Shou; Russell, Carolyn

    2012-01-01

    Formability and abnormal grain growth (AGG) are the two major issues that have been encountered for Al alloy spun formed dome development using friction stir welded blanks. Material properties that have significant influence on the formability include forming range and strain hardening exponent. In this study, tensile tests were performed for two 2195 friction stir weld parameter sets at 400 F to study the effects of post weld anneal on the forming range and strain hardening exponent. It was found that the formability can be enhanced by applying a newly developed post weld anneal to heat treat the friction stir welded panels. This new post weld anneal leads to a higher forming range and much improved strain hardening exponent. AGG in the weld nugget is known to cause a significant reduction of ductility and fracture toughness. This study also investigated how AGG may be influenced by the heating rate to the solution heat treatment temperature. After post-weld annealing, friction stir welds were strained to 15% and 39% by compression at 400 F before they were subjected to SHT at 950 F for 1 hour. Salt bath SHT is very effective in reducing the grain size as it helps arrest the onset of AGG and promote normal recrystallization and grain growth. However, heat treating a 18 ft dome using a salt bath is not practical. Efforts are continuing at Marshall Space Flight Center to identify the welding parameters and heat treating parameters that can help mitigate the AGG in the friction stir welds.

  9. The coupled kinetics of grain growth and fission product behavior in nuclear fuel under degraded-core accident conditions

    International Nuclear Information System (INIS)

    Rest, J.

    1985-01-01

    The theoretical FASTGRASS-VFP model has been used in the interpretation of fission gas, iodine, and cesium release from (1) irradiated high-burnup LWR fuel in a flowing steam atmosphere during high-temperature, in-cell heating tests (performed at Oak Ridge National Laboratory) and (2) trace-irratiated LWR fuel during severe-fuel-damage (SFD) tests (performed in the PBF reactor in Idaho). A theory of grain boundary sweeping of gas bubbles has been included within the FASTGRASS-VFP formalism. This theory considers the interaction between the moving grain boundary and two distinct size classes of bubbles, those on grain faces and on grain edges, and provides a means of determining whether gas bubbles are caught up and moved along by a moving grain boundary or whether the grain boundary is only temporarily retarded by the bubbles and then breaks away. In addition, as FASTGRASS-VFP provides for a mechanistic calculation of intra- and intergranular fission product behavior, the coupled calculation between fission gas behavior and grain growth is kinetically comprehensive. Results of the analyses demonstrate that intragranular fission product behavior during both types of tests can be interpreted in terms of a grain-growth/grain-boundary-sweeping mechanism that enhances the flow of fission products from within the grains to the grain boundaries. The effect of fuel oxidation by steam on fission product and grain growth behavior is also considered. The FASTGRASS-VFP predictions, measured release rates from the above tests, and previously published release rates are compared and differences between fission product behavior in trace-irradiated and in high-burnup fuel are highlighted. (orig.)

  10. Grain growth kinetics of ringwoodite and majorite garnet mixtures and implications for the rheology of the transition zone

    Science.gov (United States)

    Ezad, I.; Dobson, D. P.; Brodholt, J. P.; Thomson, A.; Hunt, S.

    2017-12-01

    The grain size of the transition zone is a poorly known but important geophysical parameter. Among others, the grain size may control the rheology, seismic attenuation and radiative thermal conductivity of the mantle. However, the grain size of the transition zone minerals ringwoodite (Mg,Fe)2SiO4 and majorite garnet MgSiO3 under appropriate zone conditions is currently unknown and there are very few experiments with which to constrain it. In order to determine the grain size of the transition zone, the grain growth kinetics must be determined for a range of mantle compositions. We have, therefore, experimentally determined the grain growth kinetics of the lowermost transition zone minerals through multi anvil experiments at University College London (UCL). This is achieved through a comprehensive set of time series experiments at pressures of 21 GPa and temperatures relevant to the transition zone. We have also determined the effect of varying water content, oxygen fugacity, iron content and aluminium content also discussed by Dobson and Mariani., (2014). Our initial grain growth experiments conducted at 1200°C and 1400°C at 18 GPa show extremely slow grain growth kinetics; time series experiments extended to 105.8 seconds are unable to produce grains larger than 100 nm. This suggests that fine-grained material at the base of the transition zone will persist on geological timescales. Such small grains size suggests that diffusion creep might be the dominant deformation mechanism in this region. Reference: Dobson, D.P., Mariani, E., 2014. The kinetics of the reaction of majorite plus ferropericlase to ringwoodite: Implications for mantle upwellings crossing the 660 km discontinuity. Earth Planet. Sci. Lett. 408, 110-118. doi:10.1016/j.epsl.2014.10.009

  11. Magnetization reversal processes of isotropic permanent magnets with various inter-grain exchange interactions

    Directory of Open Access Journals (Sweden)

    Hiroshi Tsukahara

    2017-05-01

    Full Text Available We performed a large-scale micromagnetics simulation on a supercomputing system to investigate the properties of isotropic nanocrystalline permanent magnets consisting of cubic grains. In the simulation, we solved the Landau–Lifshitz–Gilbert equation under a periodic boundary condition for accurate calculation of the magnetization dynamics inside the nanocrystalline isotropic magnet. We reduced the inter-grain exchange interaction perpendicular and parallel to the external field independently. Propagation of the magnetization reversal process is inhibited by reducing the inter-grain exchange interaction perpendicular to the external field, and the coercivity is enhanced by this restraint. In contrast, when we reduce the inter-grain exchange interaction parallel to the external field, the coercivity decreases because the magnetization reversal process propagates owing to dipole interaction. These behaviors show that the coercivity of an isotropic permanent magnet depends on the direction of the inter-grain exchange interaction.

  12. Analytical expression for the evolution of interfacial area density between transformed grains during nucleation and growth transformations

    DEFF Research Database (Denmark)

    Rios, P.R.; Godiksen, R.B.; Schmidt, Søren

    2006-01-01

    This paper shows that interfacial area density between transformed grains during nucleation and growth transformations and the contiguity are useful descriptors of microstructural evolution. These descriptors are evaluated analytically and compared with results from computer simulation. Usage...

  13. Computer simulation of 2D grain growth using a cellular automata model based on the lowest energy principle

    International Nuclear Information System (INIS)

    He Yizhu; Ding Hanlin; Liu Liufa; Shin, Keesam

    2006-01-01

    The morphology, topology and kinetics of normal grain growth in two-dimension were studied by computer simulation using a cellular automata (Canada) model based on the lowest energy principle. The thermodynamic energy that follows Maxwell-Boltzmann statistics has been introduced into this model for the calculation of energy change. The transition that can reduce the system energy to the lowest level is chosen to occur when there is more than one possible transition direction. The simulation results show that the kinetics of normal grain growth follows the Burke equation with the growth exponent m = 2. The analysis of topology further indicates that normal grain growth can be simulated fairly well by the present CA model. The vanishing of grains with different number of sides is discussed in the simulation

  14. High day- and night-time temperatures affect grain growth dynamics in contrasting rice genotypes.

    Science.gov (United States)

    Shi, Wanju; Yin, Xinyou; Struik, Paul C; Solis, Celymar; Xie, Fangming; Schmidt, Ralf C; Huang, Min; Zou, Yingbin; Ye, Changrong; Jagadish, S V Krishna

    2017-11-02

    Rice grain yield and quality are predicted to be highly vulnerable to global warming. Five genotypes including heat-tolerant and susceptible checks, a heat-tolerant near-isogenic line and two hybrids were exposed to control (31 °C/23 °C, day/night), high night-time temperature (HNT; 31 °C/30 °C), high day-time temperature (HDT; 38 °C/23 °C) and high day- and night-time temperature (HNDT; 38 °C/30 °C) treatments for 20 consecutive days during the grain-filling stage. Grain-filling dynamics, starch metabolism enzymes, temporal starch accumulation patterns and the process of chalk formation were quantified. Compensation between the rate and duration of grain filling minimized the impact of HNT, but irreversible impacts on seed-set, grain filling and ultimately grain weight were recorded with HDT and HNDT. Scanning electron microscopy demonstrated irregular and smaller starch granule formation affecting amyloplast build-up with HDT and HNDT, while a quicker but normal amylopast build-up was recorded with HNT. Our findings revealed temporal variation in the starch metabolism enzymes in all three stress treatments. Changes in the enzymatic activity did not derail starch accumulation under HNT when assimilates were sufficiently available, while both sucrose supply and the conversion of sucrose into starch were affected by HDT and HNDT. The findings indicate differential mechanisms leading to high day and high night temperature stress-induced loss in yield and quality. Additional genetic improvement is needed to sustain rice productivity and quality under future climates. © Society for Experimental Biology 2017.

  15. Variations in grain lipophilic phytochemicals, proteins and resistance to Fusarium spp. growth during grain storage as affected by biological plant protection with Aureobasidium pullulans (de Bary).

    Science.gov (United States)

    Wachowska, Urszula; Tańska, Małgorzata; Konopka, Iwona

    2016-06-16

    Modern agriculture relies on an integrated approach, where chemical treatment is reduced to a minimum and replaced by biological control that involves the use of active microorganisms. The effect of the antagonistic yeast-like fungus Aureobasidium pullulans on proteins and bioactive compounds (alkylresorcinols, sterols, tocols and carotenoids) in winter wheat grain and on the colonization of wheat kernels by fungal microbiota, mainly Fusarium spp. pathogens, was investigated. Biological treatment contributed to a slight increase contents of tocols, alkylresorcinols and sterols in grain. At the same time, the variation of wheat grain proteins was low and not significant. Application of A. pullulans enhanced the natural yeast colonization after six months of grain storage and inhibited growth of F. culmorum pathogens penetrating wheat kernel. This study demonstrated that an integrated approach of wheat grain protection with the use of the yeast-like fungus A. pullulans reduced kernel colonization by Fusarium spp. pathogens and increased the content of nutritionally beneficial phytochemicals in wheat grain without a loss of gluten proteins responsible for baking value. Copyright © 2016. Published by Elsevier B.V.

  16. Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

    Energy Technology Data Exchange (ETDEWEB)

    Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R; Graham, G; Bajt, S; Bradley, J; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

    2007-03-28

    While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium.

  17. Rate and Timing Effects of Growth Regulating Herbicides Applications on Grain Sorghum (Sorghum bicolor Growth and Yield

    Directory of Open Access Journals (Sweden)

    Thierry E. Besançon

    2016-01-01

    Full Text Available Dicamba and 2,4-D are among the most common and inexpensive herbicides used to control broadleaf weeds. However, different studies have pointed the risk of crop injury and grain sorghum yield reduction with postemergence applications of 2,4-D. No research data on grain sorghum response to 2,4-D or dicamba exists in the Southeastern United States. Consequently, a study was conducted to investigate crop growth and yield response to 2,4-D (100, 220, and 330 g acid equivalent ha−1 and dicamba (280 g acid equivalent ha−1 applied on 20 to 65 cm tall sorghum. Greater stunting resulted from 2,4-D applied at 330 g acid equivalent ha−1 or below 45 cm tall sorghum whereas lodging prevailed with 2,4-D at 330 g acid equivalent ha−1 and dicamba applied beyond 35 cm tall crop. Regardless of local environmental conditions, 2,4-D applied up to 35 cm tall did not negatively impact grain yield. There was a trend for yields to be somewhat lower when 2,4-D was applied on 45 or 55 cm tall sorghum whereas application on 65 cm tall sorghum systematically decreased yields. More caution should be taken with dicamba since yield reduction has been reported as early as applications made on 35 cm tall sorghum for a potentially dicamba sensitive cultivar.

  18. Coarse-grained stochastic processes and kinetic Monte Carlo simulators for the diffusion of interacting particles

    Science.gov (United States)

    Katsoulakis, Markos A.; Vlachos, Dionisios G.

    2003-11-01

    We derive a hierarchy of successively coarse-grained stochastic processes and associated coarse-grained Monte Carlo (CGMC) algorithms directly from the microscopic processes as approximations in larger length scales for the case of diffusion of interacting particles on a lattice. This hierarchy of models spans length scales between microscopic and mesoscopic, satisfies a detailed balance, and gives self-consistent fluctuation mechanisms whose noise is asymptotically identical to the microscopic MC. Rigorous, detailed asymptotics justify and clarify these connections. Gradient continuous time microscopic MC and CGMC simulations are compared under far from equilibrium conditions to illustrate the validity of our theory and delineate the errors obtained by rigorous asymptotics. Information theory estimates are employed for the first time to provide rigorous error estimates between the solutions of microscopic MC and CGMC, describing the loss of information during the coarse-graining process. Simulations under periodic boundary conditions are used to verify the information theory error estimates. It is shown that coarse-graining in space leads also to coarse-graining in time by q2, where q is the level of coarse-graining, and overcomes in part the hydrodynamic slowdown. Operation counting and CGMC simulations demonstrate significant CPU savings in continuous time MC simulations that vary from q3 for short potentials to q4 for long potentials. Finally, connections of the new coarse-grained stochastic processes to stochastic mesoscopic and Cahn-Hilliard-Cook models are made.

  19. MODERNIZATION OF THE FILTERS FOR THE DEDUSTING OF ASPIRATION EMISSION OF GRAIN PROCESSING ENTERPRISES

    Directory of Open Access Journals (Sweden)

    S. Ju. Panov

    2012-01-01

    Full Text Available Data are presented on the successful modernization of the filter to replace the mechanical cleaning system for low pressure pulsed jet regeneration in order to improve system performance dedusting aspiration emission of grain processing enterprises.

  20. NUMERICAL SIMULATIONS OF SUPERNOVA DUST DESTRUCTION. I. CLOUD-CRUSHING AND POST-PROCESSED GRAIN SPUTTERING

    International Nuclear Information System (INIS)

    Silvia, Devin W.; Smith, Britton D.; Michael Shull, J.

    2010-01-01

    We investigate through hydrodynamic simulations the destruction of newly formed dust grains by sputtering in the reverse shocks of supernova (SN) remnants. Using an idealized setup of a planar shock impacting a dense, spherical clump, we implant a population of Lagrangian particles into the clump to represent a distribution of dust grains in size and composition. We then post-process the simulation output to calculate the grain sputtering for a variety of species and size distributions. We explore the parameter space appropriate for this problem by altering the overdensity of the ejecta clumps and the speed of the reverse shocks. Since radiative cooling could lower the temperature of the medium in which the dust is embedded and potentially protect the dust by slowing or halting grain sputtering, we study the effects of different cooling methods over the timescale of the simulations. In general, our results indicate that grains with radii less than 0.1 μm are sputtered to much smaller radii and often destroyed completely, while larger grains survive their interaction with the reverse shock. We also find that, for high ejecta densities, the percentage of dust that survives is strongly dependent on the relative velocity between the clump and the reverse shock, causing up to 50% more destruction for the highest velocity shocks. The fraction of dust destroyed varies widely across grain species, ranging from total destruction of Al 2 O 3 grains to minimal destruction of Fe grains (only 20% destruction in the most extreme cases). C and SiO 2 grains show moderate to strong sputtering as well, with 38% and 80% mass loss. The survival rate of grains formed by early SNe is crucial in determining whether or not they can act as the 'dust factories' needed to explain high-redshift dust.

  1. Russian Kefir Grains Microbial Composition and Its Changes during Production Process.

    Science.gov (United States)

    Kotova, I B; Cherdyntseva, T A; Netrusov, A I

    2016-01-01

    By combining DGGE-PCR method, classical microbiological analysis and light- and electron microscopic observations, it was found that the composition of microbial communities of central Russia regions kefir grains, starter and kefir drink include bacteria of the genera Lactobacillus, Leuconostoc and Lactococcus, and yeast anamorphs of the genera Saccharomyces, Kazachstania and Gibellulopsis. Fifteen prokaryotic and four eukaryotic pure cultures of microorganisms were isolated and identified from kefir grains. It has been shown that members of the genus Lactobacillus prevailed in kefir grains, whereas strains Leuconostoc pseudomesenteroides and Lactococcus lactis dominated in the final product - kefir drink. Yeasts contained in kefir grains in small amounts have reached a significant number of cells in the process of development of this dairy product. The possibility of reverse cell aggregation has been attempted in a mixed cultivation of all isolated pure cultures, but full formation kefir grains is not yet observed after 1.5 years of observation and reinoculations.

  2. Grain refinement and mechanical properties of CP-Ti processed by warm accumulative roll bonding

    International Nuclear Information System (INIS)

    Milner, Justin L.; Abu-Farha, Fadi; Bunget, Cristina; Kurfess, Thomas; Hammond, Vincent H.

    2013-01-01

    Accumulative roll bonding (ARB), a severe plastic deformation technique, was used in this study to process commercially pure titanium (CP-Ti) at 450 °C. Sheet samples were processed by seven consecutive ARB cycles, with an overall equivalent strain of 5.6. Mechanical characterization and microstructural examination were carried out on the processed material to track their changes and relationships with regard to one another. Electron microscopy, TEM in particular, revealed significant grain refinement in the material, with submicron microstructure achieved even after one cycle of warm processing. Further processing was shown to progressively fragment the highly elongated grains, ultimately producing a predominantly-equiaxed ultrafine grain structure with an average grain size of ∼100 nm. Tensile strength and microhardness of the material increased with the number of ARB cycles; the strength–grain size relationship followed the Hall–Petch equation. The overall grain refinement and strengthening levels observed here are close to those reported in the literature for ARB processing of CP-Ti at ambient temperatures. This demonstrates the ability of warm ARB can be as effective as cold ARB, while offering several advantages for industrial utilization.

  3. Physical quality of grains subjected to moistening and drying processes for marketing

    Directory of Open Access Journals (Sweden)

    Paulo C. Coradi

    Full Text Available ABSTRACT The aim was to evaluate the physical quality of conventional and transgenic corn grains, through drying and wetting processes for marketing. The experimental design was completely randomized in a factorial scheme (7 x 3 x 2, corresponding to seven drying times (0, 20, 40, 60, 80, 100 and 120 min, three temperatures of the drying air (80, 100 and 120 °C and two hybrids of corn (conventional AG 1051 and transgenic Herculex@ 30S31H. Grain drying was held in convection oven with forced air ventilation while the wetting was done in a B.O.D chamber. The water movement in the grain, the volume and the electrical conductivity were evaluated periodically. The results showed that the transgenic corn grain reduced the negative effects of drying and moistening on the physical quality. The increase in drying air temperature accelerated the physical deterioration of conventional and transgenic corn grains. The increase in water content by the moistening process caused losses in grain physical quality, similar to the drying process, for both the conventional and transgenic corn grains.

  4. Parameters Online Detection and Model Predictive Control during the Grain Drying Process

    Directory of Open Access Journals (Sweden)

    Lihui Zhang

    2013-01-01

    Full Text Available In order to improve the grain drying quality and automation level, combined with the structural characteristics of the cross-flow circulation grain dryer designed and developed by us, the temperature, moisture, and other parameters measuring sensors were placed on the dryer, to achieve online automatic detection of process parameters during the grain drying process. A drying model predictive control system was set up. A grain dry predictive control model at constant velocity and variable temperature was established, in which the entire process was dried at constant velocity (i.e., precipitation rate per hour is a constant and variable temperature. Combining PC with PLC, and based on LabVIEW, a system control platform was designed.

  5. INFRARED SPECTROSCOPIC SURVEY OF THE QUIESCENT MEDIUM OF NEARBY CLOUDS. I. ICE FORMATION AND GRAIN GROWTH IN LUPUS

    Energy Technology Data Exchange (ETDEWEB)

    Boogert, A. C. A. [IPAC, NASA Herschel Science Center, Mail Code 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Chiar, J. E. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Knez, C.; Mundy, L. G. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Öberg, K. I. [Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Pendleton, Y. J. [Solar System Exploration Research Virtual Institute, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Tielens, A. G. G. M.; Van Dishoeck, E. F., E-mail: aboogert@ipac.caltech.edu [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

    2013-11-01

    Infrared photometry and spectroscopy (1-25 μm) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H{sub 2}O ices form at extinctions of A{sub K} = 0.25 ± 0.07 mag (A{sub V} = 2.1 ± 0.6). Such a low ice formation threshold is consistent with the absence of nearby hot stars. Overall, the Lupus clouds are in an early chemical phase. The abundance of H{sub 2}O ice (2.3 ± 0.1 × 10{sup –5} relative to N{sub H}) is typical for quiescent regions, but lower by a factor of three to four compared to dense envelopes of young stellar objects. The low solid CH{sub 3}OH abundance (<3%-8% relative to H{sub 2}O) indicates a low gas phase H/CO ratio, which is consistent with the observed incomplete CO freeze out. Furthermore it is found that the grains in Lupus experienced growth by coagulation. The mid-infrared (>5 μm) continuum extinction relative to A{sub K} increases as a function of A{sub K}. Most Lupus lines of sight are well fitted with empirically derived extinction curves corresponding to R{sub V} ∼ 3.5 (A{sub K} = 0.71) and R{sub V} ∼ 5.0 (A{sub K} = 1.47). For lines of sight with A{sub K} > 1.0 mag, the τ{sub 9.7}/A{sub K} ratio is a factor of two lower compared to the diffuse medium. Below 1.0 mag, values scatter between the dense and diffuse medium ratios. The absence of a gradual transition between diffuse and dense medium-type dust indicates that local conditions matter in the process that sets the τ{sub 9.7}/A{sub K} ratio. This process is likely related to grain growth by coagulation, as traced by the A{sub 7.4}/A{sub K} continuum extinction ratio, but not to ice mantle formation. Conversely, grains acquire ice mantles before the process of coagulation starts.

  6. INFRARED SPECTROSCOPIC SURVEY OF THE QUIESCENT MEDIUM OF NEARBY CLOUDS. I. ICE FORMATION AND GRAIN GROWTH IN LUPUS

    International Nuclear Information System (INIS)

    Boogert, A. C. A.; Chiar, J. E.; Knez, C.; Mundy, L. G.; Öberg, K. I.; Pendleton, Y. J.; Tielens, A. G. G. M.; Van Dishoeck, E. F.

    2013-01-01

    Infrared photometry and spectroscopy (1-25 μm) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H 2 O ices form at extinctions of A K = 0.25 ± 0.07 mag (A V = 2.1 ± 0.6). Such a low ice formation threshold is consistent with the absence of nearby hot stars. Overall, the Lupus clouds are in an early chemical phase. The abundance of H 2 O ice (2.3 ± 0.1 × 10 –5 relative to N H ) is typical for quiescent regions, but lower by a factor of three to four compared to dense envelopes of young stellar objects. The low solid CH 3 OH abundance ( 2 O) indicates a low gas phase H/CO ratio, which is consistent with the observed incomplete CO freeze out. Furthermore it is found that the grains in Lupus experienced growth by coagulation. The mid-infrared (>5 μm) continuum extinction relative to A K increases as a function of A K . Most Lupus lines of sight are well fitted with empirically derived extinction curves corresponding to R V ∼ 3.5 (A K = 0.71) and R V ∼ 5.0 (A K = 1.47). For lines of sight with A K > 1.0 mag, the τ 9.7 /A K ratio is a factor of two lower compared to the diffuse medium. Below 1.0 mag, values scatter between the dense and diffuse medium ratios. The absence of a gradual transition between diffuse and dense medium-type dust indicates that local conditions matter in the process that sets the τ 9.7 /A K ratio. This process is likely related to grain growth by coagulation, as traced by the A 7.4 /A K continuum extinction ratio, but not to ice mantle formation. Conversely, grains acquire ice mantles before the process of coagulation starts

  7. A multiscale coupled finite-element and phase-field framework to modeling stressed grain growth in polycrystalline thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jamshidian, M., E-mail: jamshidian@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); Thamburaja, P., E-mail: prakash.thamburaja@gmail.com [Department of Mechanical & Materials Engineering, Universiti Kebangsaan Malaysia (UKM), Bangi 43600 (Malaysia); Rabczuk, T., E-mail: timon.rabczuk@tdt.edu.vn [Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City (Viet Nam); Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City (Viet Nam)

    2016-12-15

    A previously-developed finite-deformation- and crystal-elasticity-based constitutive theory for stressed grain growth in cubic polycrystalline bodies has been augmented to include a description of excess surface energy and grain-growth stagnation mechanisms through the use of surface effect state variables in a thermodynamically-consistent manner. The constitutive theory was also implemented into a multiscale coupled finite-element and phase-field computational framework. With the material parameters in the constitutive theory suitably calibrated, our three-dimensional numerical simulations show that the constitutive model is able to accurately predict the experimentally-determined evolution of crystallographic texture and grain size statistics in polycrystalline copper thin films deposited on polyimide substrate and annealed at high-homologous temperatures. In particular, our numerical analyses show that the broad texture transition observed in the annealing experiments of polycrystalline thin films is caused by grain growth stagnation mechanisms. - Graphical abstract: - Highlights: • Developing a theory for stressed grain growth in polycrystalline thin films. • Implementation into a multiscale coupled finite-element and phase-field framework. • Quantitative reproduction of the experimental grain growth data by simulations. • Revealing the cause of texture transition to be due to the stagnation mechanisms.

  8. Determination of the growth restriction factor and grain size for aluminum alloys by a quasi-binary equivalent method

    International Nuclear Information System (INIS)

    Mitrašinović, A.M.; Robles Hernández, F.C.

    2012-01-01

    Highlights: ► A new method to determine the growth restricting factor. (Q) is proposed ► The proposed method is highly accurate (R 2 = 0.99) and simple. ► A major novelty of this method is the determination of Q for non-dilute samples. ► The method proposed herein is based on quasi-binary phase diagrams and composition. ► This method can be easily implemented industrially or as a research tool. - Abstract: In the present research paper is suggested a new methodology to determine the growth restricting factor (Q) and grain size (GS) for various Al-alloys. The present method combines a thermodynamical component based on the liquidus behavior of each alloying element that is later incorporated into the well known growth restricting models for multi-component alloys. This approach that can be used to determine Q and/or GS based on the chemical composition and the slope of the liquidus temperature of any Al-alloy solidified in close to equilibrium conditions. This method can be modified further in order to assess the effect of cooling rate or thermomechanical processing on growth restricting factor and grain size. In the present paper is proposed a highly accurate (R 2 = 0.99) and validated model for Al–Si alloys, but it can be modified for any other Al–X alloying system. The present method can be used for alloys with relatively high solute content and due to the use of the thermodynamics of liquidus this system considers the poisoning effects of single and multi-component alloying elements.

  9. Coercivity enhancement of hot-deformed Nd-Fe-B magnets by the eutectic grain boundary diffusion process

    International Nuclear Information System (INIS)

    Liu, Lihua; Sepehri-Amin, H.; Ohkubo, T.; Yano, M.; Kato, A.; Shoji, T.; Hono, K.

    2016-01-01

    Nd-M (M = Al, Cu, Ga, Zn, Mn) alloys with compositions close to eutectic points were investigated as diffusion sources for the grain boundary diffusion process to hot-deformed Nd-Fe-B magnets. Coercivity enhancement was observed for most of the alloys. Among them, the sample processed with Nd 90 Al 10 exhibited the highest coercivity of 2.5 T at room temperature. However, the sample processed with Nd 70 Cu 30 exhibited the highest coercivity of 0.7 T at 200 ° C. Microstructural observations using scanning transmission electron microscope (STEM) showed that nonferromagnetic Nd-rich intergranular phase envelops the Nd 2 Fe 14 B grains after the diffusion process. Abnormal grain growth and the dissolution of Al into the Nd 2 Fe 14 B grains were observed in the sample processed with Nd 90 Al 10 , which explains its inferior thermal stability of coercivity compared to the sample processed with Nd 70 Cu 30 . The coercivity enhancement and poor thermal stability of the coercivity of the Nd 90 Al 10 diffusion-processed sample are discussed based on microstructure studies by transmission electron microscopy. - Highlights: • Coercivity of hot-deformed Nd-Fe-B magnets is enhanced by the infiltration of various R-TM eutectic alloys. • The sample infiltrated with Nd 90 Al 10 shows the highest coercivity of 2.5 T at room temperature. • At 200 °C, Nd 70 Cu 30 diffusion-processed sample possesses the highest coercivity of 0.7 T.

  10. Coercivity enhancement of hot-deformed Nd-Fe-B magnets by the eutectic grain boundary diffusion process

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lihua [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577 (Japan); Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Yano, M.; Kato, A.; Shoji, T. [Toyota Motor Corporation, Advanced Material Engineering Div., Susono 410-1193 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577 (Japan)

    2016-05-05

    Nd-M (M = Al, Cu, Ga, Zn, Mn) alloys with compositions close to eutectic points were investigated as diffusion sources for the grain boundary diffusion process to hot-deformed Nd-Fe-B magnets. Coercivity enhancement was observed for most of the alloys. Among them, the sample processed with Nd{sub 90}Al{sub 10} exhibited the highest coercivity of 2.5 T at room temperature. However, the sample processed with Nd{sub 70}Cu{sub 30} exhibited the highest coercivity of 0.7 T at 200 {sup °}C. Microstructural observations using scanning transmission electron microscope (STEM) showed that nonferromagnetic Nd-rich intergranular phase envelops the Nd{sub 2}Fe{sub 14}B grains after the diffusion process. Abnormal grain growth and the dissolution of Al into the Nd{sub 2}Fe{sub 14}B grains were observed in the sample processed with Nd{sub 90}Al{sub 10}, which explains its inferior thermal stability of coercivity compared to the sample processed with Nd{sub 70}Cu{sub 30}. The coercivity enhancement and poor thermal stability of the coercivity of the Nd{sub 90}Al{sub 10} diffusion-processed sample are discussed based on microstructure studies by transmission electron microscopy. - Highlights: • Coercivity of hot-deformed Nd-Fe-B magnets is enhanced by the infiltration of various R-TM eutectic alloys. • The sample infiltrated with Nd{sub 90}Al{sub 10} shows the highest coercivity of 2.5 T at room temperature. • At 200 °C, Nd{sub 70}Cu{sub 30} diffusion-processed sample possesses the highest coercivity of 0.7 T.

  11. Influence of hydrothermal processing on functional properties and grain morphology of finger millet.

    Science.gov (United States)

    Dharmaraj, Usha; Meera, M S; Reddy, S Yella; Malleshi, Nagappa G

    2015-03-01

    Finger millet was hydrothermally processed followed by decortication. Changes in color, diameter, density, sphericity, thermal and textural characteristics and also some of the functional properties of the millet along with the grain morphology of the kernels after hydrothermal processing and decortication were studied. It was observed that, the millet turned dark after hydrothermal processing and color improved over native millet after decortication. A slight decrease in grain diameter was observed but sphericity of the grains increased on decortication. The soft and fragile endosperm turned into a hard texture and grain hardness increased by about 6 fold. Hydrothermal processing increased solubility and swelling power of the millet at ambient temperature. Pasting profile indicated that, peak viscosity decreased significantly on hydrothermal processing and both hydrothermally processed and decorticated millet exhibited zero breakdown viscosity. Enthalpy was negative for hydrothermally processed millet and positive for decorticated grains. Microscopic studies revealed that the orderly structure of endosperm changed to a coherent mass after hydrothermal processing and the different layers of seed coat get fused with the endosperm.

  12. Enhancement of Growth and Grain Yield of Rice in Nutrient Deficient Soils by Rice Probiotic Bacteria

    Institute of Scientific and Technical Information of China (English)

    Md Mohibul Alam KHAN; Effi HAQUE; Narayan Chandra PAUL; Md Abdul KHALEQUE; Saleh M. S. AL-GARNI; Mahfuzur RAHMAN; Md Tofazzal ISLAM

    2017-01-01

    Plant associated bacteria are promising alternatives to chemical fertilizers for plant growth and yield improvement in an eco-friendly manner. In this study, rice associated bacteria were isolated and assessed for mineral phosphate solubilization and indole-3-acetic acid (IAA) production activity in vitro. Six promising strains, which were tentatively identified as phylotaxon Pseudochrobactrum sp. (BRRh-1), Burkholderia sp. (BRRh-2), Burkholderia sp. (BRRh-3), Burkholderia sp. (BRRh-4), Pseudomonas aeruginosa (BRRh-5 and BRRh-6) based on their 16S rRNA gene phylogeny, exhibited significant phosphate solubilizing activity in National Botanical Research Institute phosphate growth medium, and BRRh-4 displayed the highest phosphate solubilizing activity, followed by BRRh-5. The pH of the culture broth declined, resulting in increase of growth rate of bacteria at pH 7, which might be due to organic acid secretion by the strains. In presence of L-tryptophan, five isolates synthesized IAA and the maximum IAA was produced by BRRh-2, followed by BRRh-1. Application of two most efficient phosphate solubilizing isolates BRRh-4 and BRRh-5 by root dipping (colonization) of seedling and spraying at the flowering stage significantly enhanced the growth and grain yield of rice variety BRRI dhan-29. Interestingly, application of both strains with 50% of recommended nitrogen, phosphorus and potassium fertilizers produced equivalent or higher grain yield of rice compared to the control grown with full recommended fertilizer doses, which suggests that these strains may have the potential to be used as bioinoculants for sustainable rice production.

  13. SPECTROSCOPIC INFRARED EXTINCTION MAPPING AS A PROBE OF GRAIN GROWTH IN IRDCs

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Wanggi [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Carey, Sean J. [Infrared Processing Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Tan, Jonathan C. [Departments of Astronomy and Physics, University of Florida, Gainesville, FL 32611 (United States)

    2015-11-20

    We present spectroscopic tests of MIR to FIR extinction laws in IRDC G028.36+00.07, a potential site of massive star and star cluster formation. Lim and Tan developed methods of FIR extinction mapping of this source using Spitzer-MIPS 24 μm and Herschel-PACS 70 μm images, and by comparing to MIR Spitzer-IRAC 3–8 μm extinction maps, found tentative evidence for grain growth in the highest mass surface density regions. Here we present results of spectroscopic infrared extinction mapping using Spitzer-IRS (14–38 μm) data of the same Infrared dark cloud (IRDC). These methods allow us to first measure the SED of the diffuse Galactic interstellar medium that is in the foreground of the IRDC. We then carry out our primary investigation of measuring the MIR to FIR opacity law and searching for potential variations as a function of mass surface density within the IRDC. We find relatively flat, featureless MIR–FIR opacity laws that lack the ∼12 and ∼35 μm features associated with the thick water ice mantle models of Ossenkopf and Henning. Their thin ice mantle models and the coagulating aggregate dust models of Ormel et al. are a generally better match to the observed opacity laws. We also find evidence for generally flatter MIR to FIR extinction laws as mass surface density increases, strengthening the evidence for grain and ice mantle growth in higher density regions.

  14. SPECTROSCOPIC INFRARED EXTINCTION MAPPING AS A PROBE OF GRAIN GROWTH IN IRDCs

    International Nuclear Information System (INIS)

    Lim, Wanggi; Carey, Sean J.; Tan, Jonathan C.

    2015-01-01

    We present spectroscopic tests of MIR to FIR extinction laws in IRDC G028.36+00.07, a potential site of massive star and star cluster formation. Lim and Tan developed methods of FIR extinction mapping of this source using Spitzer-MIPS 24 μm and Herschel-PACS 70 μm images, and by comparing to MIR Spitzer-IRAC 3–8 μm extinction maps, found tentative evidence for grain growth in the highest mass surface density regions. Here we present results of spectroscopic infrared extinction mapping using Spitzer-IRS (14–38 μm) data of the same Infrared dark cloud (IRDC). These methods allow us to first measure the SED of the diffuse Galactic interstellar medium that is in the foreground of the IRDC. We then carry out our primary investigation of measuring the MIR to FIR opacity law and searching for potential variations as a function of mass surface density within the IRDC. We find relatively flat, featureless MIR–FIR opacity laws that lack the ∼12 and ∼35 μm features associated with the thick water ice mantle models of Ossenkopf and Henning. Their thin ice mantle models and the coagulating aggregate dust models of Ormel et al. are a generally better match to the observed opacity laws. We also find evidence for generally flatter MIR to FIR extinction laws as mass surface density increases, strengthening the evidence for grain and ice mantle growth in higher density regions

  15. Residual-stress-induced grain growth of twinned grains and its effect on formability of magnesium alloy sheet at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Se-Jong [Korea Institute of Material Science, 66 Sangnam-dong, C-si, Gyeongnam 641-831 (Korea, Republic of); Kim, Daeyong, E-mail: daeyong@kims.re.kr [Korea Institute of Material Science, 66 Sangnam-dong, C-si, Gyeongnam 641-831 (Korea, Republic of); Lee, Keunho; Cho, Hoon-Hwe; Han, Heung Nam [Department of Materials Science and Engineering and RIAM, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2015-11-15

    A magnesium alloy sheet was subjected to in-plane compression along with a vertical load to avoid buckling during compression. Pre-compressed specimens machined from the sheet were annealed at different temperatures and the changes in microstructure and texture were observed using electron back scattered diffraction (EBSD). Twinned grains preferentially grew during annealing at 300 °C, so that a strong texture with the < 0001 > direction parallel to the transverse direction developed. EBSD analysis confirmed that the friction caused by the vertical load induced inhomogeneous distribution of residual stress, which acted as an additional driving force for preferential grain growth of twinned grain during annealing. The annealed specimen showed excellent formability. - Highlights: • A magnesium alloy sheet subjected to in-plane compression under a vertical load • The vertical load induced inhomogeneous distribution of the residual stress. • The residual stress acted as an additional driving force for grain growth. • The annealed specimen with strong non-basal texture showed excellent formability.

  16. CHARACTERIZATION OF THE GRAINS IN 2014 ALUMINIUM ALLOY AFTER EQUAL CHANNEL ANGULAR EXTRUSION (ECAE PROCESS

    Directory of Open Access Journals (Sweden)

    Sonia Boczkal

    2011-05-01

    Full Text Available In 2014 alloy deformed by Equal Channel Angular Extrusion process (ECAE the changes in the size and shape of structural constituents were examined. The samples subjected after deformation to additional annealing at 300°C/10min were characterized by larger grains of nearly-equiaxial shapes. The microstructure after deformation was composed of a large number of the mutually crossing bands and microbands. The intersection of microbands resulted in formation of rectangular and rhombohedral grains. It was noted that the average grain size after ε = 4.6 (4 passes was 0.2 μm.

  17. Performance of process-based models for simulation of grain N in crop rotations across Europe

    DEFF Research Database (Denmark)

    Yin, Xiaogang; Kersebaum, KC; Kollas, C

    2017-01-01

    The accurate estimation of crop grain nitrogen (N; N in grain yield) is crucial for optimizing agricultural N management, especially in crop rotations. In the present study, 12 process-based models were applied to simulate the grain N of i) seven crops in rotations, ii) across various pedo...... (Brassica napus L.). These differences are linked to the intensity of parameterization with better parameterized crops showing lower prediction errors. The model performance was influenced by N fertilization and irrigation treatments, and a majority of the predictions were more accurate under low N...

  18. Solar Ion Processing of Itokawa Grains: Reconciling Model Predictions with Sample Observations

    Science.gov (United States)

    Christoffersen, Roy; Keller, L. P.

    2014-01-01

    Analytical TEM observations of Itokawa grains reported to date show complex solar wind ion processing effects in the outer 30-100 nm of pyroxene and olivine grains. The effects include loss of long-range structural order, formation of isolated interval cavities or "bubbles", and other nanoscale compositional/microstructural variations. None of the effects so far described have, however, included complete ion-induced amorphization. To link the array of observed relationships to grain surface exposure times, we have adapted our previous numerical model for progressive solar ion processing effects in lunar regolith grains to the Itokawa samples. The model uses SRIM ion collision damage and implantation calculations within a framework of a constant-deposited-energy model for amorphization. Inputs include experimentally-measured amorphization fluences, a Pi steradian variable ion incidence geometry required for a rotating asteroid, and a numerical flux-versus-velocity solar wind spectrum.

  19. Microstructure evolution and grain refinement of Ti-6Al-4V alloy by laser shock processing

    Energy Technology Data Exchange (ETDEWEB)

    Ren, X.D., E-mail: renxd@mail.ujs.edu.cn [Department of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China); Research Center of Fluid Machinery Engineering and Technical, Jiangsu University, Zhenjiang, 212013 (China); Zhou, W.F.; Liu, F.F.; Ren, Y.P. [Department of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China); Yuan, S.Q. [Research Center of Fluid Machinery Engineering and Technical, Jiangsu University, Zhenjiang, 212013 (China); Ren, N.F.; Xu, S.D.; Yang, T. [Department of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China)

    2016-02-15

    Graphical abstract: The grain refinement process of Ti-6Al-4V alloy under LSP: (a) LDD in original grains; (b) Dislocations in β phase; (c) DTIs in α phase; (d) DTs transform into DCs; (e) DWs develop into sub-GBs; (f) GR accomplishes. - Highlights: • LSP could repair the surface defects and reduce the surface roughness. • Microstructure evolution of α phase in Ti-6Al-4V alloy processed by LSP is distinct from β phase. • Multidirectional twin intersections and subgrain boundaries are the main mechanism of grain refinement of Ti-6Al-4V alloy. • Grain refinement process of the Ti-6Al-4V alloy was illustrated. - Abstract: Microstructure evolution and grain refinement of Ti-6Al-4V alloy after laser shock processing (LSP) are systematically investigated in this paper. Laser shock waves were induced by a Q-switched Nd:YAG laser system operated with a wave-length of 1064 nm and 10 ns pulse width. The microstructures of LSP samples were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Present results indicate that the surface hardness of samples subjected to LSP impacts has significantly improved. Multidirectional twin intersections and dislocation movements lead to grain subdivision in α phase with ultra-high plastic deformation. High-density dislocations are found in β phase. Multidirectional twin intersections and division of sub-grain boundaries play an important role in the grain refinement of Ti-6Al-4V alloy under LSP loading conditions.

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

    DEFF Research Database (Denmark)

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

    1983-01-01

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

  1. Drought priming at vegetative growth stages improves tolerance to drought and heat stresses occurring during grain filling in spring wheat

    DEFF Research Database (Denmark)

    Wang, Xiao; Vignjevic, Marija; Liu, Fulai

    2015-01-01

    Plants of spring wheat (Triticum aestivum L. cv. Vinjett) were exposed to moderate water deficit at the vegetative growth stages six-leaf and/or stem elongation to investigate drought priming effects on tolerance to drought and heat stress events occurring during the grain filling stage. Compared......Plants of spring wheat (Triticum aestivum L. cv. Vinjett) were exposed to moderate water deficit at the vegetative growth stages six-leaf and/or stem elongation to investigate drought priming effects on tolerance to drought and heat stress events occurring during the grain filling stage...... of abscisic acid in primed plants under drought stress could contribute to higher grain yield compared to the non-primed plants. Taken together, the results indicate that drought priming during vegetative stages improved tolerance to both drought and heat stress events occurring during grain filling in wheat....

  2. Grain growth kinetics and electrical properties of lanthanum modified lead zirconate titanate (9/65/35) based ferroelectric ceramics

    International Nuclear Information System (INIS)

    Roca, R. Alvarez; Guerrero, F.; Botero, E. R.; Garcia, D.; Eiras, J. A.; Guerra, J. D. S.

    2009-01-01

    The influence of the microstructural characteristics on the dielectric and electrical properties has been investigated for Nd 3+ doped lanthanum modified lead zirconate titanate ferroelectric ceramics, obtained by the conventional solid-state reaction method, by taking into account different sintering conditions. The grain growth mechanism has been investigated and a cubic-type grain growth law was observed for samples with grain size varying from 1.00 up to 2.35 μm. The porosity and grain size dependences of the phase transition parameters, such as the maximum dielectric permittivity and its corresponding temperature (ε m and T m , respectively) were also investigated. The ac conductivity analyses followed the universal Jonscher law. The behavior of the frequency exponent (s) was analyzed through the correlated barrier hopping model. Both ac and dc conductivity results have been correlated with the observed microstructural features

  3. Materials process and applications of single grain (RE)-Ba-Cu-O bulk high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Li Beizhan; Zhou Difan; Xu Kun; Hara, Shogo; Tsuzuki, Keita; Miki, Motohiro; Felder, Brice; Deng Zigang [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology (TUMSAT), 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Izumi, Mitsuru, E-mail: izumi@kaiyodai.ac.jp [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology (TUMSAT), 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan)

    2012-11-20

    This paper reviews recent advances in the melt process of (RE)-Ba-Cu-O [(RE)BCO, where RE represents a rare earth element] single grain high-temperature superconductors (HTSs), bulks and its applications. The efforts on the improvement of the magnetic flux pinning with employing the top-seeded melt-growth process technique and using a seeded infiltration and growth process are discussed. Which including various chemical doping strategies and controlled pushing effect based on the peritectic reaction of (RE)BCO. The typical experiment results, such as the largest single domain bulk, the clear TEM observations and the significant critical current density, are summarized together with the magnetization techniques. Finally, we highlight the recent prominent progress of HTS bulk applications, including Maglev, flywheel, power device, magnetic drug delivery system and magnetic resonance devices.

  4. Materials process and applications of single grain (RE)-Ba-Cu-O bulk high-temperature superconductors

    Science.gov (United States)

    Li, Beizhan; Zhou, Difan; Xu, Kun; Hara, Shogo; Tsuzuki, Keita; Miki, Motohiro; Felder, Brice; Deng, Zigang; Izumi, Mitsuru

    2012-11-01

    This paper reviews recent advances in the melt process of (RE)-Ba-Cu-O [(RE)BCO, where RE represents a rare earth element] single grain high-temperature superconductors (HTSs), bulks and its applications. The efforts on the improvement of the magnetic flux pinning with employing the top-seeded melt-growth process technique and using a seeded infiltration and growth process are discussed. Which including various chemical doping strategies and controlled pushing effect based on the peritectic reaction of (RE)BCO. The typical experiment results, such as the largest single domain bulk, the clear TEM observations and the significant critical current density, are summarized together with the magnetization techniques. Finally, we highlight the recent prominent progress of HTS bulk applications, including Maglev, flywheel, power device, magnetic drug delivery system and magnetic resonance devices.

  5. Abnormal Grain Growth in the Heat Affected Zone of Friction Stir Welded Joint of 32Mn-7Cr-1Mo-0.3N Steel during Post-Weld Heat Treatment

    Directory of Open Access Journals (Sweden)

    Yijun Li

    2018-04-01

    Full Text Available The abnormal grain growth in the heat affected zone of the friction stir welded joint of 32Mn-7Cr-1Mo-0.3N steel after post-weld heat treatment was confirmed by physical simulation experiments. The microstructural stability of the heat affected zone can be weakened by the welding thermal cycle. It was speculated to be due to the variation of the non-equilibrium segregation state of solute atoms at the grain boundaries. In addition, the pressure stress in the welding process can promote abnormal grain growth in the post-weld heat treatment.

  6. On the strengthening behavior of ultrafine-grained nickel processed from nanopowders

    International Nuclear Information System (INIS)

    Bui, Q.H.; Dirras, G.; Ramtani, S.; Gubicza, J.

    2010-01-01

    Bulk ultrafine-grained nickel specimens having grain sizes in the range of 0.25-5 μm were processed by a spark plasma sintering method. The resulting microstructures were characterized by electron backscattering diffraction, transmission electron microscopy and X-ray diffraction analysis. Compression tests were carried out at room temperature and at a strain rate of 1.6 x 10 -4 s -1 . It was found that the fine-grained microstructure and the presence of NiO phase were the main strengthening factors in the as-processed bulk materials. The contribution of the oxide phase to strengthening was even more pronounced for lower grain sizes. This contribution was calculated as the difference between the measured strength and the value obtained from a Hall-Petch plot of oxide-free samples, and this yielded a flow stress increment of about 635 MPa for the lowest grain size studied here. In addition, a transition from work-hardening to -softening occurred for materials having a mean grain size smaller than about 300 nm and having boundaries that could have been weakened by the presence of a high amount of NiO phase.

  7. [Impacts of drought stress on the growth and development and grain yield of spring maize in Northeast China].

    Science.gov (United States)

    Ji, Rui-Peng; Che, Yu-Sheng; Zhu, Yong-Ning; Liang, Tao; Feng, Rui; Yu, Wen-Ying; Zhang, Yu-Shu

    2012-11-01

    Taking spring maize variety Danyu-39 as test object, an experiment was conducted in a large-scale agricultural water controlling experimental field to study the impacts of drought stress at three key growth stages, i. e. , 3-leaf-jointing, jointing-silking, and silking-milk ripe, on the growth and development and grain yield of spring maize in Northeast China. Two treatments were installed, including moderate drought stress (MS) and re-watering to suitable water (CK). Compared with CK, the MS at 3-leaf-jointing stage postponed the whole growth period of Danyu-39 by 13 d, and the plant height and leaf area at jointing stage were decreased by 29.8% and 41.2%, respectively. After re-watering, the plant height and grain yield recovered obviously, and the differences in ear characteristics and final yield were insignificant. The MS at jointing-silking stage shortened the whole growth period by 7 d, the plant height and leaf area at silking stage were decreased by 18.6% and 14.1%, respectively, the ear length, grain number per ear, ear dry mass, and grain mass per ear decreased by 6.9%, 19.1%, 28.1%, and 29.4%, respectively, and the blank stem rate increased by 13.3%. When the maize suffered from moderate drought stress at silking-milk ripe stage, the whole growth period was shortened by 15 d, the plant height and leaf area at milk ripe stage were decreased by 2.3% and 37.3%, respectively, the ear length, grain number per ear, ear dry mass, and grain mass per ear decreased by 9.2%, 24.1%, 30.8%, and 27.9%, respectively, and the blank stem rate increased by 24.5%. After re-watering at the latter two stages, the recovery of plant height was little, and the grain yield decreased significantly.

  8. Phase transformation and grain growth behavior of a nanocrystalline 18/8 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kotan, Hasan, E-mail: hasankotan@gmail.com [Konya Necmettin Erbakan University, Department of Metallurgical & Materials Engineering, Konya 42090 (Turkey); Darling, Kris A. [US Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States)

    2017-02-16

    Fe-18Cr-8Ni and Fe-18Cr-8Ni-1Y (at%) stainless steel powders were nanostructured by mechanical alloying from elemental powders and subjected to 90 min annealing treatments at various temperatures. The microstructural evolutions as a function of alloy compositions and temperatures were investigated by in-situ and ex-situ x-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy. The dependence of hardness on the microstructure was utilized to study the mechanical changes. It was found that the resulting microstructures by mechanical alloying were bcc solid solution, the so-called α’-martensite structure. The high temperature in-situ x-ray diffraction experiments showed that the martensite-to-austenite reverse phase transformation was completed above 800 and 900 °C for Fe-18Cr-8Ni and Fe-18Cr-8Ni-1Y steels, respectively. A partial or complete retransformation to martensite was observed upon cooling to room temperature. Annealing of nanocrystalline Fe-18Cr-8Ni steel yielded grain growth reaching to micron sizes at 1100 °C while addition of 1 at% yttrium stabilized the microstructure around 160 nm grain size and 6 GPa hardness after 90 min annealing at 1200 °C.

  9. GROWTH PERFORMANCE AND CARCASS COMPOSITION OF RABBITS FED ON DIETS OF GRADUAL LEVELS OF BARLEY GRAIN

    Directory of Open Access Journals (Sweden)

    M.M. El-Adawy

    2012-05-01

    Full Text Available Forty-eight male New Zealand White rabbits of 6 weeks age (BW 875 ± 28.3 g were randomly allocated among six groups in different levels of barley grains (BG; 0 (B0, 5 (B5, 10 (B10, 15 (B15, 20 (B20, 25% (B25 of the total diet on growth performance and carcass composition of rabbits . The highest live BW value (P < 0.05 was obtained in B20 rabbits, whereas the highest feed intake (P < 0.05 value was obtained in B25 rabbits followed by those fed on the other diets. The better-feed conversion ratio (FCR was obtained in B20 rabbits followed by those of B15 and B25. Animals of B20 had better FCR than those of the other experimental diets. The relative contribution of soft feces to dry matter or crude protein intake differed (P < 0.05 among the experimental diets. The caecal turnover rate was increased (P < 0.05 in B15 and B20 rabbits than those other diets. The per-slaughter weight, hot and cold carcass weight and dressing percentage were differed (P < 0.05 among the experimental groups and highest values were recorded in B20 rabbits. Data suggested that a partial replacement of corn grains (CG by 20% BG in rabbit diets was increased live body weight, feed intake and feed conversion ratio.

  10. Ultrafine grained Cu processed by compression with oscillatory torsion

    OpenAIRE

    K. Rodak

    2007-01-01

    Purpose: The aim of this work is a study of Cu microstructure after severe plastic deformation process by usingcompression with oscillatory torsion test.Design/methodology/approach: Cu samples were deformed at torsion frequency (f) changed from 0 Hz(compression) to 1.8 Hz under a constant torsion angle (α) ≈8° and compression speed (v)=0.1mm/s. Structuralinvestigations were conducted by using light microscopy (LM) and transmission electron microscopy (TEM).Findings: The structural analysis ma...

  11. The effect of grain boundary chemistry on the slip transmission process through grain boundaries in Ni3Al

    International Nuclear Information System (INIS)

    Robertson, I.M.; Lee, T.C.; Subramanian, R.; Birnbaum, H.K.

    1992-01-01

    This paper reports on the conditions established in disordered FCC systems for predicting the slip system that will be activated by a grain boundary to relieve a local stress concentration that have been applied to the ordered FCC alloy Ni 3 Al. The slip transfer behavior in hypo-stoichiometric Ni 3 Al with (0.2 at. %B) and without boron was directly observed by performing the deformation experiments in situ in the transmission electron microscope. In the boron-free and boron-doped alloys, lattice dislocations were incorporated in the grain boundary, but did not show evidence of dissociation to grain boundary dislocations or of movement in the grain boundary plane. The stress concentration associated with the dislocation pileup at the grain boundary are relieved by the emission of dislocations from the grain boundary in the boron-doped alloy. The slip system initiated in the adjoining grain obeyed the conditions established for disordered FCC systems. In the boron-free alloy, the primary stress relief mechanism was grain-boundary cracking, although dislocation emission from the grain boundary also occurred and accompanied intergranular crack advance

  12. Process of Equiaxed Grains of RE-Al Alloy under Slope Vibration

    International Nuclear Information System (INIS)

    Xie Shikun; Yi Rongxi; Pan Xiaoliang; Zheng Xiaoqiu; Guo Xiuyan

    2010-01-01

    A new technique using slope vibration casting process during heating and isothermal holding period to prepare Al-7Si-2RE alloy has been studied. The small, near-spherical and non-dendritic microstructure with the semi-solid processing requirements has been obtained. Experiments show that the cooling method, pouring process and the convection of melt caused by slope vibration had significant effects on the formation of near-spherical primary gains. The water-cooled copper mold casting with slope vibration at the temperature near liquidus can obtain Al-7Si-2RE alloy with small homogeneous equiaxed grains, the average grain diameter is 48.3 μm, and the average grain roundness is 1.92.

  13. Study of variation grain size in desulfurization process of calcined petroleum coke

    Science.gov (United States)

    Pintowantoro, Sungging; Setiawan, Muhammad Arif; Abdul, Fakhreza

    2018-04-01

    Indonesia is a country with abundant natural resources, such as mineral mining and petroleum. In petroleum processing, crude oil can be processed into a source of fuel energy such as gasoline, diesel, oil, petroleum coke, and others. One of crude oil potentials in Indonesia is petroleum coke. Petroleum coke is a product from oil refining process. Sulfur reducing process in calcined petroleum cokes can be done by desulfurization process. The industries which have potential to become petroleum coke processing consumers are industries of aluminum smelting (anode, graphite block, carbon mortar), iron riser, calcined coke, foundry coke, etc. Sulfur reducing process in calcined petroleum coke can be done by thermal desulfurization process with alkaline substance NaOH. Desulfurization of petroleum coke process can be done in two ways, which are thermal desulfurization and hydrodesulphurization. This study aims to determine the effect of various grain size on sulfur, carbon, and chemical bond which contained by calcined petroleum coke. The raw material use calcined petroleum coke with 0.653% sulfur content. The grain size that used in this research is 50 mesh, then varied to 20 mesh and 100 mesh for each desulfurization process. Desulfurization are tested by ICP, UV-VIS, and FTIR to determine levels of sulfur, carbon, chemical bonding and sulfur dissolved water which contained in the residual washing of calcined petroleum coke. From various grain size that mentioned before, the optimal value is on 100 mesh grain size, where the sulfur content in petroleum coke is 0.24% and carbon content reaches the highest level of 97.8%. Meanwhile for grain size 100 mesh in the desulfurization process is enough to break the chemical bonds of organic sulfur in petroleum coke.

  14. Root growth, soil water variation, and grain yield response of winter wheat to supplemental irrigation

    Directory of Open Access Journals (Sweden)

    Jianguo Man

    2016-04-01

    Full Text Available Water shortage threatens agricultural sustainability in the Huang-Huai-Hai Plain of China. Thus, we investigated the effect of supplemental irrigation (SI on the root growth, soil water variation, and grain yield of winter wheat in this region by measuring the moisture content in different soil layers. Prior to SI, the soil water content (SWC at given soil depths was monitored to calculate amount of irritation water that can rehydrate the soil to target SWC. The SWC before SI was monitored to depths of 20, 40, and 60 cm in treatments of W20, W40, and W60, respectively. Rainfed treatment with no irrigation as the control (W0. The mean root weight density (RWD, triphenyl tetrazolium chloride reduction activity (TTC reduction activity, soluble protein (SP concentrations as well as catalase (CAT, and superoxide dismutase (SOD activities in W40 and W60 treatments were significantly higher than those in W20. The RWD in 60–100 cm soil layers and the root activity, SP concentrations, CAT and SOD activities in 40–60 cm soil layers in W40 treatment were significantly higher than those in W20 and W60. W40 treatment is characterized by higher SWC in the upper soil layers but lower SWC in the 60–100-cm soil layers during grain filling. The soil water consumption (SWU in the 60–100 cm soil layers from anthesis after SI to maturity was the highest in W40. The grain yield, water use efficiency (WUE, and irrigation water productivity were the highest in W40, with corresponding mean values of 9169 kg ha−1, 20.8 kg ha−1 mm−1, and 35.5 kg ha−1 mm−1. The RWD, root activities, SP concentrations, CAT and SOD activities, and SWU were strongly positively correlated with grain yield and WUE. Therefore, the optimum soil layer for SI of winter wheat after jointing is 0–40 cm.

  15. B2 Grain Growth Behavior of a Ti-22Al-25Nb Alloy Fabricated by Hot Pressing Sintering

    Science.gov (United States)

    Jia, Jianbo; Liu, Wenchao; Xu, Yan; Chen, Chen; Yang, Yue; Luo, Junting; Zhang, Kaifeng

    2018-05-01

    Grain growth behavior of a powder metallurgy (P/M) Ti-22Al-25Nb alloy was investigated by applying a series of isothermal treatment tests over a wide range of temperatures and holding times. An isothermal treatment scheme was conducted in the B2 phase region (1070-1110 °C) and α 2 + B2 phase region (1010-1050 °C) at holding times of 10, 30 min, 1, 2, and 3 h, respectively. The effects of temperature and holding time on the microstructure evolution and microhardness of the P/M Ti-22Al-25Nb alloy at elevated temperatures were evaluated using optical microscope, scanning electron microscope, x-ray diffraction, and Vickers hardness test techniques. The results revealed that the alloy's treated microstructure was closely linked to temperature and holding time, respectively. The change law of B2 grain growth with holding time and temperature can be well interpreted by the Beck equation and Hillert equation, respectively. The B2 grain growth exponent n and activation energy Q were acquired based on experimental data in the α 2 + B2 and B2 phase regions. In addition, the grain growth contour map for the P/M Ti-22Al-25Nb alloy was constructed to depict variations in B2 grain size based on holding time and temperature.

  16. Effect of continuous change of sintering atmosphere on the grain growth of Cr-doped UO2 pellets

    International Nuclear Information System (INIS)

    Yang, Jae Ho; Nam, Ik Hui; Kim, Jong Hun; Rhee, Young Woo; Kim, Dong Joo; Kim, Keon Sik; Song, Kun Woo

    2010-01-01

    Cr-doped UO 2 pellet is one of the promising candidates for the high burn-up fuel in commercial LWRs. Major nuclear fuel vendors of such as AREVA or Westinghouse initiated the development of Cr-doped or Cr-containing additives doped UO 2 pellets since at the mid of 90's. Now, qualification programs are on-going to provide these pellets commercially. The main characteristics of the Cr-doped pellets are large-grain and visco-plasticity. Large grain pellet can reduce the corrosive fission gas release at high burn up. Viscoplastic soft pellets can lower the pressure to a cladding caused by a thermal expansion of a pellet at an elevated temperature during transient operations. Those advantages can provide room for additional power uprates and high burnup limits. Especially, PCI resistance improvement can be achieved by enlarging the pellet grain size and enhancing the fuel deformation at an elevated temperature. In this paper, to study the effect of oxygen partial pressure on grain growth in Cr-doped UO 2 pellets, Cr- doped UO 2 samples have been sintered with and without a step-wise change of sintering atmospheres. An introduction of a step-wise variation of oxygen partial pressure during the sintering enhances the grain growth of UO 2 pellets greatly. This step-wise sintering effect has been explained in terms of a continuous increase of Cr concentration along the grain boundary. The observed grain growth behavior under step-wisely changed sintering atmospheres demonstrates the possibility of reducing the amount of Cr 2 O 3 to minimum via control of oxygen partial pressure while keeping the large grain size

  17. Application of binomial and multinomial probability statistics to the sampling design process of a global grain tracing and recall system

    Science.gov (United States)

    Small, coded, pill-sized tracers embedded in grain are proposed as a method for grain traceability. A sampling process for a grain traceability system was designed and investigated by applying probability statistics using a science-based sampling approach to collect an adequate number of tracers fo...

  18. Effects of feeding blends of grains naturally contaminated with Fusarium mycotoxins on growth and immunological parameters of broiler chickens.

    Science.gov (United States)

    Swamy, H V L N; Smith, T K; Karrow, N A; Boermans, H J

    2004-04-01

    An experiment was conducted to investigate the effects of feeding grains naturally contaminated with Fusarium mycotoxins on growth and immunological parameters of broiler chickens. Three hundred sixty, 1-d-old male broiler chicks were fed 1 of 4 diets containing grains naturally contaminated with Fusarium mycotoxins for 56 d. The diets included (1) control; (2) low level of contaminated grains (5.9 mg/kg deoxynivalenol (DON), 19.1 mg/kg fusaric acid (FA), 0.4 mg/kg zearalenone, and 0.3 mg/kg 15-acetyldeoxynivalenol; (3) high level of contaminated grains (9.5 mg/kg DON, 21.4 mg/kg FA, 0.7 mg/kg zearalenone, and 0.5 mg/kg 15-acetyldeoxynivalenol); and (4) high level of contaminated grains + 0.2% polymeric glucomannan mycotoxin adsorbent (GM polymer). Body weight gains and feed consumption of chickens fed contaminated grains decreased linearly with the inclusion of contaminated grains during the grower phase (d 21 to 42). Efficiency of feed utilization, however, was not affected by diet. Production parameters were not significantly affected by the supplementation of GM polymer to the contaminated grains. Peripheral blood monocytes decreased linearly in birds fed contaminated grains. The feeding of contaminated diets linearly reduced the B-cell count at the end of the experiment, whereas the T-cell count on d 28 responded quadratically to the contaminated diets. The feeding of contaminated diets did not significantly alter serum or bile immunoglobulin concentrations, contact hypersensitivity to dinitrochlorobenzene, or antibody response to SRBC. Supplementation with GM polymer in the contaminated diet nonspecifically increased white blood cell count and lymphocyte count, while preventing mycotoxin-induced decreases in B-cell counts. It was concluded that broiler chickens are susceptible during extended feeding of grains naturally contaminated with Fusarium mycotoxins.

  19. Advanced Materials Growth and Processing Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This most extensive of U.S. Army materials growth and processing facilities houses seven dedicated, state-of-the-art, molecular beam epitaxy and three metal organic...

  20. Aerosol chemistry in Titan's ionosphere: simultaneous growth and etching processes

    Science.gov (United States)

    Carrasco, Nathalie; Cernogora, Guy; Jomard, François; Etcheberry, Arnaud; Vigneron, Jackie

    2016-10-01

    Since the Cassini-CAPS measurements, organic aerosols are known to be present and formed at high altitudes in the diluted and partially ionized medium that is Titan's ionosphere [1]. This unexpected chemistry can be further investigated in the laboratory with plasma experiments simulating the complex ion-neutral chemistry starting from N2-CH4 [2]. Two sorts of solid organic samples can be produced in laboratory experiments simulating Titan's atmospheric reactivity: grains in the volume and thin films on the reactor walls. We expect that grains are more representative of Titan's atmospheric aerosols, but films are used to provide optical indices for radiative models of Titan's atmosphere.The aim of the present study is to address if these two sorts of analogues are chemically equivalent or not, when produced in the same N2-CH4 plasma discharge. The chemical compositions of both these materials are measured by using elemental analysis, XPS analysis and Secondary Ion Mass Spectrometry. We find that films are homogeneous but significantly less rich in nitrogen and hydrogen than grains produced in the same experimental conditions. This surprising difference in their chemical compositions is explained by the efficient etching occurring on the films, which stay in the discharge during the whole plasma duration, whereas the grains are ejected after a few minutes [3]. The impact for our understanding of Titan's aerosols chemical composition is important. Our study shows that chemical growth and etching process are simultaneously at stake in Titan's ionosphere. The more the aerosols stay in the ionosphere, the more graphitized they get through etching process. In order to infer Titan's aerosols composition, our work highlights a need for constraints on the residence time of aerosols in Titan's ionosphere. [1] Waite et al. (2009) Science , 316, p. 870[2] Szopa et al. (2006) PSS, 54, p. 394[3] Carrasco et al. (2016) PSS, 128, p. 52

  1. Grain growth competition during thin-sample directional solidification of dendritic microstructures: A phase-field study

    International Nuclear Information System (INIS)

    Tourret, D.; Song, Y.; Clarke, A.J.; Karma, A.

    2017-01-01

    We present the results of a comprehensive phase-field study of columnar grain growth competition in bi-crystalline samples in two dimensions (2D) and in three dimensions (3D) for small sample thicknesses allowing a single row of dendrites to form. We focus on the selection of grain boundary (GB) orientation during directional solidification in the steady-state dendritic regime, and study its dependence upon the orientation of two competing grains. In 2D, we map the entire orientation range for both grains, performing several simulations for each configuration to account for the stochasticity of GB orientation selection and to assess the average GB behavior. We find that GB orientation selection depends strongly on whether the primary dendrite growth directions have lateral components (i.e. components perpendicular to the axis of the temperature gradient) that point in the same or opposite directions in the two grains. We identify a range of grain orientations in which grain selection follows the classical description of Walton and Chalmers. We also identify conditions that favor unusual overgrowth of favorably-oriented dendrites at a converging GB. We propose a simple analytical description that reproduces the average GB orientation selection from 2D simulations within statistical fluctuations of a few degrees. In 3D, we find a similar GB orientation selection as in 2D when secondary branches grow in planes parallel and perpendicular to the sample walls. Remarkably, quasi-2D behavior is also observed even when those perpendicular sidebranching planes are rotated by a finite azimuthal angle about the primary dendrite growth axis as long as the absolute values of those azimuthal angles are equal in both grains. In contrast, when the absolute values of those azimuthal angles differ markedly, we find that unusual overgrowth events at a converging GB are promoted by a high azimuthal angle in the least-favorably-oriented grain. We also find that diverging GBs can be

  2. A review on the factors affecting mite growth in stored grain commodities.

    Science.gov (United States)

    Collins, D A

    2012-03-01

    A thorough review of the literature has identified the key factors and interactions that affect the growth of mite pests on stored grain commodities. Although many factors influence mite growth, the change and combinations of the physical conditions (temperature, relative humidity and/or moisture content) during the storage period are likely to have the greatest impact, with biological factors (e.g. predators and commodity) playing an important role. There is limited information on the effects of climate change, light, species interactions, local density dependant factors, spread of mycotoxins and action thresholds for mites. A greater understanding of these factors may identify alternative control techniques. The ability to predict mite population dynamics over a range of environmental conditions, both physical and biological, is essential in providing an early warning of mite infestations, advising when appropriate control measures are required and for evaluating control measures. This information may provide a useful aid in predicting and preventing mite population development as part of a risk based decision support system.

  3. Technological barriers to the growth of the export potential of Russian grain industry

    Directory of Open Access Journals (Sweden)

    O. A. Eremchenko

    2017-01-01

    Full Text Available Russia is the world's largest wheat exporter. The sales volume on foreign markets in 2015 amounted to $3.9 billion, or 10.1% of global exports. By the end of 2015, the volume of exports of agricultural products exceeded revenues from sales of arms in foreign markets. However, in dollar terms, wheat exports correspond to only a fifth place in the world. The article analyzes the reasons for a significant gap in the volume of exports and revenue, barriers to the development of export of agricultural deep processed products. The assumption is made that the development of technologies for deep processing of grain crops will increase the share of exports of Russian products with high added value.

  4. GRAPH MODELING OF THE GRAIN PROCESSING ENTERPRISE FOR SECONDARY EXPLOSION ESTIMATIONS

    Directory of Open Access Journals (Sweden)

    A. S. Popov

    2016-08-01

    Full Text Available Mathematical model for the possible development of the primary explosion at the grain processing enterprise is created. It is proved that only instability is possible for the combustion process. This model enables to estimate possibility of the secondary explosion at any object of the enterprise and forms the base for mathematical support of the decision support system for explosion-proof. Such decision support system can be included in the control system of the processing enterprise.

  5. Growth, Structure and Firm Dynamics in Grain Markets: The Case of ...

    African Journals Online (AJOL)

    Optiplex 7010 Pro

    In this paper we consider the microeconomic evidence on the determinants of firm performance in Ethiopia, with a focus on grain traders. We analyse both internal and external factors, and the relative impacts of these factors on the performance of grain traders. Different economic indicators seem to suggest that grain ...

  6. Effects of Two Different Pozole Preparation Processes on Quality Variables and Pasting Properties of Processed Maize Grain

    Directory of Open Access Journals (Sweden)

    María Gricelda Vázquez-Carrillo

    2017-01-01

    Full Text Available The effects of two different pozole preparation processes, traditional (TP and industrial (IP, on quality variables, chemical composition, and pasting properties of processed grain of nine maize landraces were evaluated. Nixtamalization and steeping time in TP (~15 h allowed more water absorption resulting in higher moisture content as well as softer debranned nixtamal relative to the debranned nixtamal produced by IP (52 min. Steeping in TP and bleaching in IP increased the pasting temperature, peak viscosity, and time to peak viscosity of maize starch. Flowering time was shorter in IP (120 min and was significantly affected by the hardness of debranned nixtamal and bleached precooked grains. Total dry matter loss was higher in IP (>10.5% than in TP (<5.0%, mainly due to the complete elimination of pedicel and pericarp by the Ca(OH2 + NaOH solution during cooking. Soft grains, with low test weight, a high proportion of floury endosperm, and high peak viscosity, are required to obtain higher yield of bleached precooked grains and soft flowered grains in both processes.

  7. Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

    International Nuclear Information System (INIS)

    Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H.Y.; Fu, B.Q.; Li, M.; Liu, W.

    2013-01-01

    Highlights: ► Recrystallization temperature of a rolled W was ∼2480 °C under applied HHF loads. ► Fine grains were obtained under HHF loads with appropriate short pulse length. ► With increasing pulse length, the recrystallized grains significantly grew larger. ► A linear relationship between ln d and 1/T max was found. ► Activation energy for grain growth in T evolution up to T max in 1.5 s was obtained. -- Abstract: Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m 2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/T max ) was found and accordingly the activation energy for grain growth in temperature evolution up to T max in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads

  8. THE ROLE OF TINY GRAINS ON THE ACCRETION PROCESS IN PROTOPLANETARY DISKS

    International Nuclear Information System (INIS)

    Bai Xuening

    2011-01-01

    Tiny grains such as polycyclic aromatic hydrocarbons (PAHs) have been thought to dramatically reduce the coupling between the gas and magnetic fields in weakly ionized gas such as in protoplanetary disks (PPDs) because they provide a tremendous surface area to recombine free electrons. The presence of tiny grains in PPDs thus raises the question of whether the magnetorotational instability (MRI) is able to drive rapid accretion consistent with observations. Charged tiny grains have similar conduction properties as ions, whose presence leads to qualitatively new behaviors in the conductivity tensor, characterized by n-bar /n e >1, where n e and n-bar denote the number densities of free electrons and all other charged species, respectively. In particular, Ohmic conductivity becomes dominated by charged grains rather than by electrons when n-bar /n e exceeds about 10 3 , and Hall and ambipolar diffusion (AD) coefficients are reduced by a factor of ( n-bar /n e ) 2 in the AD-dominated regime relative to that in the Ohmic regime. Applying the methodology of Bai, we find that in PPDs, when PAHs are sufficiently abundant (∼> 10 -9 per H 2 molecule), there exists a transition radius r trans of about 10-20 AU, beyond which the MRI active layer extends to the disk midplane. At r trans , the optimistically predicted MRI-driven accretion rate M-dot is one to two orders of magnitude smaller than that in the grain-free case, which is too small compared with the observed rates, but is in general no smaller than the predicted M-dot with solar-abundance 0.1 μm grains. At r > r trans , we find that, remarkably, the predicted M-dot exceeds the grain-free case due to a net reduction of AD by charged tiny grains and reaches a few times 10 -8 M sun yr -1 . This is sufficient to account for the observed M-dot in transitional disks. Larger grains (∼> 0.1 μm) are too massive to reach such high abundance as tiny grains and to facilitate the accretion process.

  9. A highly efficient 3D level-set grain growth algorithm tailored for ccNUMA architecture

    Science.gov (United States)

    Mießen, C.; Velinov, N.; Gottstein, G.; Barrales-Mora, L. A.

    2017-12-01

    A highly efficient simulation model for 2D and 3D grain growth was developed based on the level-set method. The model introduces modern computational concepts to achieve excellent performance on parallel computer architectures. Strong scalability was measured on cache-coherent non-uniform memory access (ccNUMA) architectures. To achieve this, the proposed approach considers the application of local level-set functions at the grain level. Ideal and non-ideal grain growth was simulated in 3D with the objective to study the evolution of statistical representative volume elements in polycrystals. In addition, microstructure evolution in an anisotropic magnetic material affected by an external magnetic field was simulated.

  10. Effect of second phase particles topology on the onset temperature of abnormal grain growth in Fe - 3%Si steels

    Directory of Open Access Journals (Sweden)

    Stoyka, V.

    2008-01-01

    Full Text Available The relations between regimes of dynamic annealing, state of secondary particles system and the onset temperature of abnormal grain growth are investigated. Two distinguish types of Fe-3%Si grain-oriented steels, after one and two stage cold rolling, were studied. The second phase particles remain unaffected in first type of steel during the heat treatment. Vice versa, the increased density of second phases was observed after annealing in the second type of the investigated materials. It is shown that start/onset of abnormal grain growth strongly depends on both volume fraction of second phase particles and annealing temperature. Texture and magnetic properties of the investigated samples are investigated within the current study.

  11. Growth and sedimentation of dust grains in the primitive solar nebular

    International Nuclear Information System (INIS)

    Battaglia, A.

    1987-01-01

    Formation of the planets in the solar system is envisioned to occur via a gravitational instability in a thin layer of dust located at the midplane of the primitive solar nebula. The break-up of the dust layer gives rise to seed plants (planetesimals) that, through successive collisions, eventually form the present-day planets. This thesis addresses the problem of the formation of the dust layer, beginning with a configuration in which the dust particles are uniformly mixed with the nebula's turbulent gas. To describe the properties of turbulence in the primitive solar nebula, models by Canuto et al. (1987) and by Cabot et al. (1987) are used. The available results concerning calculation of the velocity of particles embedded in a turbulent fluid were found to be unsatisfactory; therefore, a new formalism was developed to express the latter quantity in terms of the properties of the turbulence in the fluid. Following the space-time evolution of the grains, formalism was developed that simulates the simultaneous processes of collisions and sedimentation of the dust grains in the primitive solar nebula. It is concluded that, for the model of the primitive solar nebula considered, the formation of a dust layer at midplane is very unlikely

  12. Improving 6061-Al Grain Growth and Penetration across HIP-Bonded Clad Interfaces in Monolithic Fuel Plates: Initial Studies

    Energy Technology Data Exchange (ETDEWEB)

    Hackenberg, Robert E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); McCabe, Rodney J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Montalvo, Joel D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clarke, Kester D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dvornak, Matthew J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Edwards, Randall L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Crapps, Justin M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Trujillo, R. Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Aikin, Beverly [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vargas, Victor D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hollis, Kendall J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lienert, Thomas J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Forsyth, Robert T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harada, Kiichi L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2013-05-06

    Grain penetration across aluminum-aluminum cladding interfaces in research reactor fuel plates is desirable and was obtained by a legacy roll-bonding process, which attained 20-80% grain penetration. Significant grain penetration in monolithic fuel plates produced by Hot Isostatic Press (HIP) fabrication processing is equally desirable but has yet to be attained. The goal of this study was to modify the 6061-Al in such a way as to promote a much greater extent of crossinterface grain penetration in monolithic fuel plates fabricated by the HIP process. This study documents the outcomes of several strategies attempted to attain this goal. The grain response was characterized using light optical microscopy (LOM) electron backscatter diffraction (EBSD) as a function of these prospective process modifications done to the aluminum prior to the HIP cycle. The strategies included (1) adding macroscopic gaps in the sandwiches to enhance Al flow, (2) adding engineering asperities to enhance Al flow, (3) adding stored energy (cold work), and (4) alternative cleaning and coating. Additionally, two aqueous cleaning methods were compared as baseline control conditions. The results of the preliminary scoping studies in all the categories are presented. In general, none of these approaches were able to obtain >10% grain penetration. Recommended future work includes further development of macroscopic grooving, transferred-arc cleaning, and combinations of these with one another and with other processes.

  13. Microstructure and properties of ultrafine grain nickel 200 after hydrostatic extrusion processes

    Science.gov (United States)

    Sitek, R.; Krajewski, C.; Kamiński, J.; Spychalski, M.; Garbacz, H.; Pachla, W.; Kurzydłowski, K. J.

    2012-09-01

    This paper presents the results of the studies of the structure and properties of ultrafine grained nickel 200 obtained by hydrostatic extrusion processes. Microstructure was characterized by means of optical microscopy and electron transmission microscopy. Corrosion resistance was studied by impedance and potentiodynamic methods using an AutoLab PGSTAT 100 potentiostat in 0.1 M Na2SO4 solution and in acidified (by addition of H2SO4) 0.1 M NaCl solution at pH = 4.2 at room temperature. Microhardness tests were also performed. The results showed that hydrostatic extrusion produces a heterogeneous, ultrafine-grained microstructure in nickel 200. The corrosive resistance tests showed that the grain refinement by hydrostatic extrusion is accompanied by a decreased corrosive resistance of nickel 200.

  14. Effect of processing on phenolic antioxidants of fruits, vegetables, and grains--a review.

    Science.gov (United States)

    Nayak, Balunkeswar; Liu, Rui Hai; Tang, Juming

    2015-01-01

    Understanding the influence of processing operations such as drying/dehydration, canning, extrusion, high hydrostatic pressure, pulsed electric field, and ohmic heating on the phytochemicals of fruits, vegetables, and grains is important in retaining the health benefiting properties of these antioxidative compounds in processed food products. Most of the previous investigations in the literature on the antioxidants of fruits, vegetables, and grains have shown that food-processing operations reduced the antioxidants of the processed foods, which is also the usual consumer perception. However, in the last decade some articles in the literature reported that the evaluation of nutritional quality of processed fruits and vegetables not only depend on the quantity of vitamin C but should include analyses of other antioxidant phytochemicals and antioxidant activity. Thermal processing increased the total antioxidant activity of tomato and sweet corn. Most importantly, analysis also depends on the condition, type, and mechanism of antioxidant assays used. This review aims to provide concise information on the influence of various thermal and nonthermal food-processing operations on the stability and kinetics of health beneficial phenolic antioxidants of fruits, vegetables, and grains.

  15. Re-imagining the Growth Process

    DEFF Research Database (Denmark)

    Clarke, Jean; Holt, Robin; Blundel, Richard

    2014-01-01

    We investigate the role and influence of the biological metaphor 'growth' in studies of organizations, specifically in entrepreneurial settings. We argue that we need to reconsider metaphorical expressions of growth processes in entrepreneurship studies in order to better understand growth...... in the light of contemporary challenges, such as environmental concerns. Our argument is developed in two stages: first, we review the role of metaphor in organization and entrepreneurship studies. Second, we reflect critically on three conceptualizations of growth that have drawn on biological metaphors......: the growing organism, natural selection and co-evolution. We find the metaphor of co-evolution heuristically valuable but under-used and in need of further refinement. We propose three characteristics of the co-evolutionary metaphor that might enrich our understanding of entrepreneurial growth: relational...

  16. Grain Nucleation and Growth in Deformed NiTi Shape Memory Alloys: An In Situ TEM Study

    Science.gov (United States)

    Burow, J.; Frenzel, J.; Somsen, C.; Prokofiev, E.; Valiev, R.; Eggeler, G.

    2017-12-01

    The present study investigates the evolution of nanocrystalline (NC) and ultrafine-grained (UFG) microstructures in plastically deformed NiTi. Two deformed NiTi alloys were subjected to in situ annealing in a transmission electron microscope (TEM) at 400 and 550 °C: an amorphous material state produced by high-pressure torsion (HPT) and a mostly martensitic partly amorphous alloy produced by wire drawing. In situ annealing experiments were performed to characterize the microstructural evolution from the initial nonequilibrium states toward energetically more favorable microstructures. In general, the formation and evolution of nanocrystalline microstructures are governed by the nucleation of new grains and their subsequent growth. Austenite nuclei which form in HPT and wire-drawn microstructures have sizes close to 10 nm. Grain coarsening occurs in a sporadic, nonuniform manner and depends on the physical and chemical features of the local environment. The mobility of grain boundaries in NiTi is governed by the local interaction of each grain with its microstructural environment. Nanograin growth in thin TEM foils seems to follow similar kinetic laws to those in bulk microstructures. The present study demonstrates the strength of in situ TEM analysis and also highlights aspects which need to be considered when interpreting the results.

  17. THE INFLUENCE OF PROCESSED PRODUCTS OF WHEAT GERM ON GRAIN BREAD QUALITY

    Directory of Open Access Journals (Sweden)

    E. I. Ponomareva

    2014-01-01

    Full Text Available Development and introduction of new types of bakery products with increased nutritional value is one of the basic and urgent problems in the bakery industry. The solution of it is the use of whole grains, as well as secondary products of their processing. The use of by-products of wheat germ (oil, oilcake, oilcake flour, which are rich in proteins and enhances the nutritional value of products is considered to be a promising area in the bakery industry. At the same time the program objectives products, developed in the framework of the "Strategy of development of the food processing industry of the Russian Federation for the period up to 2020"products, are expanding the production of cereal-based foods , and involving of secondary resources in the economy. These technologies are re-source efficient. They allow efficient use of by-products raw materials of the milling industry. The process for the preparation of grain bread on the basis of a thick sourdough from bioactivated wheat grain is known. However, despite all the advantages of grain breads with high amounts of dietary fiber, minerals and vitamins, they exhibit low levels of protein and lysine deficiency. At present larger preference is given to the raw materials of natural origin (millet, buckwheat and oatmeal flours, fruit puree, whole grains, oil, flour and wheat germ flakes, and etc. for foods enrichment in modern food science. Products of processing of wheat germ: oil, flakes, oilcake and oil-cake flour are widely used in bakery technology. To improve the nutritional value flour from wheat germ oilcake was used in the work. In the course of the research its positive effect on the quality of semi-finished and finished products was found. They differed from the control sample in a high content of antioxidants and better digestibility of proteins bread crumb.

  18. Process kinetics and digestion efficiency of anaerobic batch fermentation of brewer`s spent grains (BSG)

    Energy Technology Data Exchange (ETDEWEB)

    Ezeonu, F.C.; Okaka, A.N.C. [Nnamdi Azikiwe University, Awka (Nigeria). Dept. of Applied Biochemistry

    1996-12-31

    The process kinetics of optimized anaerobic batch digestion of brewer`s spent grains (BSG) reveal that biomethanation is essentially a first order reaction interrupted intermittently by mixed order reactions. An apparent cellulose degradation efficiency of approximately 60% and a lignin degradation efficiency of about 40% was observed in the optimized process. Using the Ken and Hashimoto model, the operational efficiency of the digester was determined to be 26%. (author)

  19. Coarse-grained simulation of a real-time process control network under peak load

    International Nuclear Information System (INIS)

    George, A.D.; Clapp, N.E. Jr.

    1992-01-01

    This paper presents a simulation study on the real-time process control network proposed for the new ANS reactor system at ORNL. A background discussion is provided on networks, modeling, and simulation, followed by an overview of the ANS process control network, its three peak-load models, and the results of a series of coarse-grained simulation studies carried out on these models using implementations of 802.3, 802.4, and 802.5 standard local area networks

  20. Factors affecting the grain growth of austenite in low alloy steel

    International Nuclear Information System (INIS)

    Parker, J.D.; Storer, S.M.

    1995-01-01

    The performance of steels is linked to the metallurgical transformations which occur during manufacture. Clearly then the optimization of a fabrication procedure must be based on fundamental relationships linking specific thermal treatments with transformation behaviour. Optimized manufacture of thick-section, multipass welds is therefore particularly complex since the thermal cycles associated with fusion welding result in the formation of heterogeneous microstructures. Moreover, these transformations will take place under rapid heating and cooling conditions so that standard data based on equilibrium behaviour may not be directly relevant. The present study is part of an integrated research programme aimed at establishing the basic microstructural relationships required to optimize the manufacture and performance of weldments. Work to date demonstrates that utilization of a computer controlled Gleeble simulation system allows a wider range of heating and cooling rates to be applied than is possible with traditional heat treatment techniques. Additional advantages of this system include precise control of time at peak temperature and uniform temperatures within a defined work zone. Results presented for a CrMoV creep resistant low alloy steel indicate that grain growth behaviour in the range 955-1390 C can be related to the time at peak temperature. The effect of this transformation behaviour on weldment behaviour is discussed. (orig.)

  1. Antagonistic activity of Ocimum sanctum L. essential oil on growth and zearalenone production by Fusarium graminearum in maize grains

    Directory of Open Access Journals (Sweden)

    Naveen Kumar eKalagatur

    2015-09-01

    Full Text Available The present study was aimed to establish the antagonistic effects of Ocimum sanctum L. essential oil (OSEO on growth and zearalenone (ZEA production of Fusarium graminearum. GC-MS chemical profiling of OSEO revealed the existence of 43 compounds and the major compound was found to be eugenol (34.7%. DPPH free radical scavenging activity (IC50 of OSEO was determined to be 8.5µg/mL. Minimum inhibitory concentration (MIC and minimum fungicidal concentration (MFC of OSEO on F. graminearum were recorded as 1250 µg/mL and 1800 µg/mL, respectively. Scanning electron microscope observations showed significant micro morphological damage in OSEO exposed mycelia and spores compared to untreated control culture. Quantitative UHPLC studies revealed that OSEO negatively effected the production of ZEA; the concentration of toxin production was observed to be insignificant at 1500 µg/mL concentration of OSEO. On other hand ZEA concentration was quantified as 3.23 µg/mL in OSEO untreated control culture. Reverse transcriptase qPCR analysis of ZEA metabolic pathway genes (PKS4 and PKS13 revealed that increase in OSEO concentration (250 µg/mL to 1500 µg/mL significantly downregulated the expression of PKS4 and PKS13. These results were in agreement with the artificially contaminated maize grains as well. In conlusion, the antifungal and antimycotoxic effects of OSEO on F. graminearum in the present study reiterated that, the essential oil of O. sanctum could be a promising herbal fungicide in food processing industries as well as grain storage centers.

  2. Constitutive expression of CaPLA1 conferred enhanced growth and grain yield in transgenic rice plants.

    Science.gov (United States)

    Park, Ki Youl; Kim, Eun Yu; Seo, Young Sam; Kim, Woo Taek

    2016-03-01

    Phospholipids are not only important components of cell membranes, but participate in diverse processes in higher plants. In this study, we generated Capsicum annuum phospholipiase A1 (CaPLA1) overexpressing transgenic rice (Oryza sativa L.) plants under the control of the maize ubiquitin promoter. The T4 CaPLA1-overexpressing rice plants (Ubi:CaPLA1) had a higher root:shoot mass ratio than the wild-type plants in the vegetative stage. Leaf epidermal cells from transgenic plants had more cells than wild-type plants. Genes that code for cyclin and lipid metabolic enzymes were up-regulated in the transgenic lines. When grown under typical paddy field conditions, the transgenic plants produced more tillers, longer panicles and more branches per panicle than the wild-type plants, all of which resulted in greater grain yield. Microarray analysis suggests that gene expressions that are related with cell proliferation, lipid metabolism, and redox state were widely altered in CaPLA1-overexpressing transgenic rice plants. Ubi:CaPLA1 plants had a reduced membrane peroxidation state, as determined by malondialdehyde and conjugated diene levels and higher peroxidase activity than wild-type rice plants. Furthermore, three isoprenoid synthetic genes encoding terpenoid synthase, hydroxysteroid dehydrogenase and 3-hydroxy-3-methyl-glutaryl-CoA reductase were up-regulated in CaPLA1-overexpressing plants. We suggest that constitutive expression of CaPLA1 conferred increased grain yield with enhanced growth in transgenic rice plants by alteration of gene activities related with cell proliferation, lipid metabolism, membrane peroxidation state and isoprenoid biosynthesis.

  3. The free growth criterion for grain initiation in TiB 2 inoculated γ-titanium aluminide based alloys

    Science.gov (United States)

    Gosslar, D.; Günther, R.

    2014-02-01

    γ-titanium aluminide (γ-TiAl) based alloys enable for the design of light-weight and high-temperature resistant engine components. This work centers on a numerical study of the condition for grain initiation during solidification of TiB2 inoculated γ-TiAl based alloys. Grain initiation is treated according to the so-called free growth criterion. This means that the free growth barrier for grain initiation is determined by the maximum interfacial mean curvature between a nucleus and the melt. The strategy presented in this paper relies on iteratively increasing the volume of a nucleus, which partially wets a hexagonal TiB2 crystal, minimizing the interfacial energy and calculating the corresponding interfacial curvature. The hereby obtained maximum curvature yields a scaling relation between the size of TiB2 crystals and the free growth barrier. Comparison to a prototypical TiB2 crystal in an as cast γ-TiAl based alloy allowed then to predict the free growth barrier prevailing under experimental conditions. The validity of the free growth criterion is discussed by an interfacial energy criterion.

  4. High-coercivity ultrafine-grained anisotropic Nd–Fe–B magnets processed by hot deformation and the Nd–Cu grain boundary diffusion process

    International Nuclear Information System (INIS)

    Sepehri-Amin, H.; Ohkubo, T.; Nagashima, S.; Yano, M.; Shoji, T.; Kato, A.; Schrefl, T.; Hono, K.

    2013-01-01

    The grain boundary diffusion process using an Nd 70 Cu 30 eutectic alloy has been applied to hot-deformed anisotropic Nd–Fe–B magnets, resulting in a substantial enhancement of coercivity, from 1.5 T to 2.3 T, at the expense of remanence. Scanning electron microscopy showed that the areal fraction of an Nd-rich intergranular phase increased from 10% to 37%. The intergranular phase of the hot-deformed magnet initially contained ∼55 at.% ferromagnetic element, while it diminished to an undetectable level after the process. Microscale eutectic solidification of Nd/NdCu as well as a fine lamellae structure of Nd 70 (Co,Cu) 30 /Nd were observed in the intergranular phase. Micromagnetic simulations indicated that the reduction of the magnetization in the intergranular phases leads to the enhancement of coercivity in agreement with the experimental observation

  5. Analysis of recrystallization and grain growth in ultra low carbon steels using EBSD

    International Nuclear Information System (INIS)

    Novillo, E.; Petite, M. M.; Bocos, J. L.; Gutierrez, I.

    2004-01-01

    This work is focused on the study of recrystallization texture and micro texture in a cold rolled ultra low carbon steel and its relationship with the global texture. Aspects like nucleation, evolution of the volume fraction and grain size were considered. An important grain selection associated with a significant size and number advantages of the recrystallized grains is observed. This grain selection gives rise to the development, at the latest stages of recrystallization, of a strong γ-fibre associated to good drawing properties. (Author) 24 refs

  6. The spatial distribution of microfabric around gravel grains: indicator of till formation processes

    Science.gov (United States)

    KalväNs, Andis; Saks, Tomas

    2010-05-01

    Till micromorphology studies in thin sections is an established tool in the field of glacial geology. Often the thin sections are inspected only visually with help of mineralogical microscope. This can lead to subjective interpretation of observed structures. More objective method used in till micromorphology is measurement of apparent microfabric, usually seen as preferred orientation of elongated sand grains. In theses studies only small fraction of elongated sand grains often confined to small area of thin section usually are measured. We present a method for automated measurement of almost all elongated sand grains across the full area of the thin section. Apparently elongated sand grains are measured using simple image analysis tools, the data are processed in a way similar to regular till fabric data and visualised as a grid of rose diagrams. The method allows to draw statistical information about spatial variation of microfabric preferred orientation and fabric strength with resolution as fine as 1 mm. Late Weichselian tills from several sites in Western Latvia were studied and large variations in fabric strength and spatial distribution were observed in macroscopically similar till units. The observed types of microfabric spatial distributions include strong, monomodal and uniform distribution; weak and highly variable in small distances distribution; consistently bimodal distribution and domain-like pattern of preferred sand grain orientation. We suggest that the method can be readily used to identify the basic deformation and sedimentation processes active during the final stages of till formation. It is understood that the microfabric orientation will be significant affected by nearby large particles. The till is highly heterogonous sediment and the source of microfabric perturbations observed in thin section might lie outside the section plane. Therefore we suggest that microfabric distribution around visible sources of perturbation - gravel grains cut

  7. Effect of Plant Essential Oils and Gamma Irradiation on Growth and Aflatoxin Production by Aspergillus Flavus Isolated from Wheat Grains

    International Nuclear Information System (INIS)

    Salem, E.A.; Shalaby, Kh.

    2016-01-01

    The antifungal potential of essential oils of Thyme (Thymus vulgaris L.) and camphor ( Eucalyptus rostrata L.) was determined on Aspergillus flavus link isolated from wheat grains on Potato dextrose agar (PDA). They inhibited completely mycelia growth of the fungus at 1000 and 2000 ppm, and prevented aflatoxin production at sub lethal dose 500 and 1000 ppm respectively. Gamma radiation was used to control mycelia growth of Aspergillus flavus Link and inhibiting aflatoxin production. A dose level of 3.5 KGy gamma radiation prevented the fungal growth and aflatoxin production by A. flavus link, where a dose of 2.5 K Gy ( the sub lethal dose) prevented about 85% of aflatoxin production

  8. Effect of zirconium on grain growth and mechanical properties of a ball-milled nanocrystalline FeNi alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kotan, Hasan, E-mail: hkotan@ncsu.edu [Department of Materials Science and Engineering, NC State University, 911 Partners Way, Room 3078, Raleigh, NC 27606-7907 (United States); Darling, Kris A. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States); Saber, Mostafa; Koch, Carl C.; Scattergood, Ronald O. [Department of Materials Science and Engineering, NC State University, 911 Partners Way, Room 3078, Raleigh, NC 27606-7907 (United States)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer Pure Fe, Fe{sub 92}Ni{sub 8}, and Fe{sub 91}Ni{sub 8}Zr{sub 1} powders were hardened up to 10 GPa by ball milling. Black-Right-Pointing-Pointer Annealing of Fe and Fe{sub 92}Ni{sub 8} leads to reduced hardness and extensive grain growth. Black-Right-Pointing-Pointer The addition of Zr to Fe{sub 92}Ni{sub 8} increases its stability and strength by second phases. Black-Right-Pointing-Pointer The second phases are found to promote the stability of Fe{sub 91}Ni{sub 8}Zr{sub 1} by Zener pinning. Black-Right-Pointing-Pointer The Zr-containing precipitates contribute to the overall strength of the material. - Abstract: Grain growth of ball-milled pure Fe, Fe{sub 92}Ni{sub 8}, and Fe{sub 91}Ni{sub 8}Zr{sub 1} alloys has been studied using X-ray diffractometry (XRD), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). Mechanical properties with respect to compositional changes and annealing temperatures have been investigated using microhardness and shear punch tests. We found the rate of grain growth of the Fe{sub 91}Ni{sub 8}Zr{sub 1} alloy to be much less than that of pure Fe and the Fe{sub 92}Ni{sub 8} alloy at elevated temperatures. The microstructure of the ternary Fe{sub 91}Ni{sub 8}Zr{sub 1} alloy remains nanoscale up to 700 Degree-Sign C where only a few grains grow abnormally whereas annealing of pure iron and the Fe{sub 92}Ni{sub 8} alloy leads to extensive grain growth. The grain growth of the ternary alloy at high annealing temperatures is coupled with precipitation of Fe{sub 2}Zr. A fine dispersion of precipitated second phase is found to promote the microstructural stability at high annealing temperatures and to increase the hardness and ultimate shear strength of ternary Fe{sub 91}Ni{sub 8}Zr{sub 1} alloy drastically when the grain size is above nanoscale.

  9. 40 CFR 180.522 - Fumigants for processed grains used in production of fermented malt beverage; tolerances for...

    Science.gov (United States)

    2010-07-01

    ... production of fermented malt beverage; tolerances for residues. 180.522 Section 180.522 Protection of... PESTICIDE CHEMICAL RESIDUES IN FOOD Specific Tolerances § 180.522 Fumigants for processed grains used in production of fermented malt beverage; tolerances for residues. (a) General. Fumigants for processed grain...

  10. Grain growth across protoplanetary discs: 10 μm silicate feature versus millimetre slope

    NARCIS (Netherlands)

    Lommen, D.J.P.; van Dishoeck, E.F.; Wright, C.M.; Min, M.

    2010-01-01

    Context. Young stars are formed with dusty discs around them. The dust grains in the disc are originally of the same size as interstellar dust, i.e., of the order of 0.1 μm. Models predict that these grains will grow in size through coagulation. Observations of the silicate features around 10 and 20

  11. Yield and grain quality of spring barley as affected by biomass formation at early growth stages

    Czech Academy of Sciences Publication Activity Database

    Křen, J.; Klem, Karel; Svobodová, I.; Míša, P.; Neudert, L.

    2014-01-01

    Roč. 60, č. 5 (2014), s. 221-227 ISSN 1214-1178 R&D Projects: GA MZe QI111A133 Keywords : Hordeum vulgare L * above-ground biomass * tillering * grain yield formation * grain protein content Subject RIV: EH - Ecology, Behaviour Impact factor: 1.226, year: 2014

  12. Fine-grained pitch processing of music and speech in congenital amusia.

    Science.gov (United States)

    Tillmann, Barbara; Rusconi, Elena; Traube, Caroline; Butterworth, Brian; Umiltà, Carlo; Peretz, Isabelle

    2011-12-01

    Congenital amusia is a lifelong disorder of music processing that has been ascribed to impaired pitch perception and memory. The present study tested a large group of amusics (n=17) and provided evidence that their pitch deficit affects pitch processing in speech to a lesser extent: Fine-grained pitch discrimination was better in spoken syllables than in acoustically matched tones. Unlike amusics, control participants performed fine-grained pitch discrimination better for musical material than for verbal material. These findings suggest that pitch extraction can be influenced by the nature of the material (music vs speech), and that amusics' pitch deficit is not restricted to musical material, but extends to segmented speech events. © 2011 Acoustical Society of America

  13. Analysis of microstructure and microtexture in grain-oriented electrical steel (GOES during manufacturing process

    Directory of Open Access Journals (Sweden)

    A. Volodarskaja

    2015-10-01

    Full Text Available The final Goss texture in grain-oriented electrical steels (GOES is affected by microstructure evolution and inheritance during the whole production process. This paper presents the results of detailed microtexture and microstructure investigations on GOES after the basic steps of the industrial AlN + Cu manufacturing process: hot rolling, first cold rolling + decarburization annealing, second cold rolling and final high temperature annealing. Microstructure studies showed that a copper addition to GOES affected solubility of sulphides. Copper rich sulphides dissolved during hot rolling and re-precipitated during decarburization annealing. An intensive precipitation of AlN and Si3N4 took place during decarburization annealing. No ε - Cu precipitation was detected. After high temperature annealing the misorientation of individual grains reached up to 8°.

  14. Study of rapid grain boundary migration in a nanocrystalline Ni thin film

    International Nuclear Information System (INIS)

    Kacher, Josh; Robertson, I.M.; Nowell, Matt; Knapp, J.; Hattar, Khalid

    2011-01-01

    Research highlights: → Abnormal growth is distributed randomly in the foil and initiates at different times. → Growth occurs from seemingly uncorrelated regions of the grain boundary. → Growth twins are created during all stages of abnormal grain growth. → Grain growth patterns are qualitatively similar to a vacancy diffusion model. → Grain boundaries and orientations evolve during growth to minimize system energy. - Abstract: Grain boundary migration associated with abnormal grain growth in pulsed-laser deposited Ni was studied in real time by annealing electron transparent films in situ in the transmission electron microscope. The resulting texture evolution and grain boundary types produced were evaluated by ex situ electron backscatter diffraction of interrupted anneals. The combination of these two techniques allowed for the investigation of grain growth rates, grain morphologies, and the evolution of the orientation and grain boundary distributions. Grain boundaries were found to progress in a sporadic, start/stop fashion with no evidence of a characteristic grain growth rate. The orientations of the abnormally growing grains were found to be predominately //ND throughout the annealing process. A high fraction of twin boundaries developed during the annealing process. The intermittent growth from different locations of the grain boundary is discussed in terms of a vacancy diffusion model for grain growth.

  15. Numerical simulation and analysis of single grain YBCO processed from graded precursor powders

    OpenAIRE

    Zou, J; Ainslie, Mark Douglas; Hu, D; Zhai, W; Kumar, N Devendra; Durrell, John Hay; Shi, Yunhua; Cardwell, David Anthony

    2015-01-01

    Large single-grain bulk high-temperature superconducting materials can trap high magnetic fields in comparison with conventional permanent magnets, making them ideal candidates to develop more compact and efficient devices, such as actuators, magnetic levitation systems, flywheel energy storage systems and electric machines. However, macro-segregation of Y-211 inclusions in melt processed Y–Ba–Cu–O (YBCO) limits the macroscopic critical current density Jc of such bulk supercond...

  16. Replacement of mineral fertilizers with anaerobically digested pig slurry in paddy fields: assessment of plant growth and grain quality.

    Science.gov (United States)

    Zhang, Jin; Wang, Minyan; Cao, Yucheng; Liang, Peng; Wu, Shengchun; Leung, Anna Oi Wah; Christie, Peter

    2017-04-01

    Rice cultivation requires large quantities of irrigation water and mineral fertilizers. This provides an opportunity for the recycling of the plant nutrients in anaerobically digested pig slurry, large amounts of which are generated in Chinese pig farms. Hence, to promote the sustainable development of livestock and poultry breeding and rice production, a micro-plot field experiment was carried out to assess whether or not slurry can replace mineral fertilizers in rice paddy production in terms of plant tillering, grain quality, and yields. The results indicate that the total N content of the slurry can serve as an alternative source of N when compared to the control (450 kg ha -1 commercial compound fertilizer (N/P 2 O 5 /K 2 O = 15:15:15) as basal fertilizer, 300 kg ha -1 urea (N% = 46), and 150 kg ha -1 commercial compound fertilizer as top-dressed fertilizer). No negative effects on plant growth or grain yield were observed, although there may be a potential risk due to an increase in grain Cu concentration. The amylose content and gel consistency of the rice grains were enhanced significantly by the use of slurry as a basal fertilizer, but the grain protein and total amino acid contents decreased. The results suggest that anaerobically digested pig slurry can replace mineral fertilizers in rice production when applied as a basal dressing together with urea and commercial compound fertilizer as top-dressed fertilizers.

  17. Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

    Science.gov (United States)

    Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H. Y.; Fu, B. Q.; Li, M.; Liu, W.

    2013-02-01

    Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/Tmax) was found and accordingly the activation energy for grain growth in temperature evolution up to Tmax in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads.

  18. Degradability of dry matter and crude protein of dry grains and wet grain silages from different processing corn hybrids (Zea mays)

    OpenAIRE

    Wagner dos Reis; Ciniro Costa; Paulo Roberto de Lima Meirelles; Marina Gabriela Berchiol da Silva; Marco Aurélio Factori; Janaína Conte Hadlich; Kátia de Oliveira; Erikelly Aline Ribeiro de Santana; Cristiano Magalhães Pariz; Josineudson Augusto II de Vasconcelos Silva

    2013-01-01

    The objective of this work was to evaluate the effect of processing two corn hybrids conserved, dry and humid grains, the dry matter (DM) and crude protein (CP) degradability in situ. The particle size was determined and difference was verified in MGD (Medium Geometric Diameter) of processed ingredients. Three sheep were used with rumen canulated, in a completely randomized design, using a factorial outline 2 x 2 x 3, being two corn hybrid, two conservation methods and three processing forms ...

  19. Texturing of sodium bismuth titanate-barium titanate ceramics by templated grain growth

    Science.gov (United States)

    Yilmaz, Huseyin

    2002-01-01

    Sodium bismuth titanate modified with barium titanate, (Na1/2Bi 1/2)TiO3-BaTiO3 (NBT-BT), is a candidate lead-free piezoelectric material which has been shown to have comparatively high piezoelectric response. In this work, textured (Na1/2Bi1/2)TiO 3-BaTiO3 (5.5mol% BaTiO3) ceramics with pc (where pc denotes the pseudocubic perovskite cell) orientation were fabricated by Templated Grain Growth (TGG) or Reactive Templated Grain Growth (RTGG) using anisotropically shaped template particles. In the case of TGG, molten salt synthesized SrTiO3 platelets were tape cast with a (Na1/2Bi1/2)TiO3-5.5mol%BaTiO3 powder and sintered at 1200°C for up to 12 hours. For the RTGG approach, Bi4Ti3O12 (BiT) platelets were tape cast with a Na2CO3, Bi2O3, TiO 2, and BaCO3 powder mixture and reactively sintered. The TGG approach using SrTiO3 templates gave stronger texture along [001] compared to the RTGG approach using BiT templates. The textured ceramics were characterized by X-ray and electron backscatter diffraction for the quality of texture. The texture function was quantified by the Lotgering factor, rocking curve, pole figures, inverse pole figures, and orientation imaging microscopy. Electrical and electromechanical property characterization of randomly oriented and pc textured (Na1/2Bi1/2)TiO 3-5.5 mol% BaTiO3 rhombohedral ceramics showed 0.26% strain at 70 kV/cm, d33 coefficients over 500 pC/N have been obtained for highly textured samples (f ˜ 90%). The piezoelectric coefficient from Berlincourt was d33 ˜ 200 pC/N. The materials show considerable hysteresis. The presence of hysteresis in the unipolar-electric field curve is probably linked to the ferroelastic phase transition seen in the (Na 1/2Bi1/2)TiO3 system on cooling from high temperature at ˜520°C. The macroscopic physical properties (remanent polarization, dielectric constant, and piezoelectric coefficient) of random and textured ([001] pc) rhombohedral perovskites were estimated by linear averaging of single

  20. 3D microstructural evolution of primary recrystallization and grain growth in cold rolled single-phase aluminum alloys

    Science.gov (United States)

    Adam, Khaled; Zöllner, Dana; Field, David P.

    2018-04-01

    Modeling the microstructural evolution during recrystallization is a powerful tool for the profound understanding of alloy behavior and for use in optimizing engineering properties through annealing. In particular, the mechanical properties of metallic alloys are highly dependent upon evolved microstructure and texture from the softening process. In the present work, a Monte Carlo (MC) Potts model was used to model the primary recrystallization and grain growth in cold rolled single-phase Al alloy. The microstructural representation of two kinds of dislocation densities, statistically stored dislocations and geometrically necessary dislocations were quantified based on the ViscoPlastic Fast Fourier transform method. This representation was then introduced into the MC Potts model to identify the favorable sites for nucleation where orientation gradients and entanglements of dislocations are high. Additionally, in situ observations of non-isothermal microstructure evolution for single-phase aluminum alloy 1100 were made to validate the simulation. The influence of the texture inhomogeneity is analyzed from a theoretical point of view using an orientation distribution function for deformed and evolved texture.

  1. Growth of large-size-two-dimensional crystalline pentacene grains for high performance organic thin film transistors

    Directory of Open Access Journals (Sweden)

    Chuan Du

    2012-06-01

    Full Text Available New approach is presented for growth of pentacene crystalline thin film with large grain size. Modification of dielectric surfaces using a monolayer of small molecule results in the formation of pentacene thin films with well ordered large crystalline domain structures. This suggests that pentacene molecules may have significantly large diffusion constant on the modified surface. An average hole mobility about 1.52 cm2/Vs of pentacene based organic thin film transistors (OTFTs is achieved with good reproducibility.

  2. The Evolution of Dust in the Multiphase ISM: Grain Destruction Processes

    Science.gov (United States)

    Wolfire, Mark

    1999-01-01

    This proposal covered year one of a long term project in which we acquired the necessary hardware and softwaxe needed to calculate grain destruction processes in the interstellar medium (ISM). The long term goal of this research is to develop a model for the dust evolution in the ISM capable of explaining observations of elemental depletions, the grain size distribution, and the emission characteristics of the ISM from the X-ray through the FIR. We purchased a SUN Ultra 10 workstation and peripheral devices including an Exabyte Tape drive, HP Laser Printer, and Seagate External Hard Disk. The PI installed the hardware and Solaris operating system on the workstation and integrated the hardware into the network. Software was also purchased to enable connections to the workstation from a PC (Hummingbird Exceed). Additional freeware required to carry out the proposed program was installed on the system including compilers (g77, gcc, g++), editors (emacs), a markup language (LaTeX), and display programs (WIP, XV, SAOtng). We have also successfully modified the required plot files to work with our system which display the results of grain processing.

  3. Production of bio-fuel ethanol from distilled grain waste eluted from Chinese spirit making process.

    Science.gov (United States)

    Tan, Li; Sun, Zhaoyong; Zhang, Wenxue; Tang, Yueqin; Morimura, Shigeru; Kida, Kenji

    2014-10-01

    Distilled grain waste eluted from Chinese spirit making is rich in carbohydrates, and could potentially serve as feedstock for the production of bio-fuel ethanol. Our study evaluated two types of saccharification methods that convert distilled grain waste to monosaccharides: enzymatic saccharification and concentrated H2SO4 saccharification. Results showed that enzymatic saccharification performed unsatisfactorily because of inefficient removal of lignin during pretreatment. Concentrated H2SO4 saccharification led to a total sugar recovery efficiency of 79.0 %, and to considerably higher sugar concentrations than enzymatic saccharification. The process of ethanol production from distilled grain waste based on concentrated H2SO4 saccharification was then studied. The process mainly consisted of concentrated H2SO4 saccharification, solid-liquid separation, decoloration, sugar-acid separation, oligosaccharide hydrolysis, and continuous ethanol fermentation. An improved simulated moving bed system was employed to separate sugars from acid after concentrated H2SO4 saccharification, by which 95.8 % of glucose and 85.8 % of xylose went into the sugar-rich fraction, while 83.3 % of H2SO4 went into the acid-rich fraction. A flocculating yeast strain, Saccharomyces cerevisiae KF-7, was used for continuous ethanol fermentation, which produced an ethanol yield of 91.9-98.9 %, based on glucose concentration.

  4. Effect of surface roughness on grain growth and sintering of alumina

    Indian Academy of Sciences (India)

    Administrator

    Variation in surface roughness properties are also correlated with grain size. Rz ... ceramic product having accurate size and shape with per- fect flatness .... Figure 1. Variation in Ra with temperature: (a) fine, (b) intermediate and (c) coarse.

  5. Growth of single crystalline seeds into polycrystalline strontium titanate: Anisotropy of the mobility, intrinsic drag effects and kinetic shape of grain boundaries

    International Nuclear Information System (INIS)

    Rheinheimer, Wolfgang; Bäurer, Michael; Handwerker, Carol A.; Blendell, John E.; Hoffmann, Michael J.

    2015-01-01

    We present a suite of measurements and combined analyses of grain growth in SrTiO 3 for oriented single crystals into polycrystals. The growth distance and standard deviation and the microstructure evolution along the single crystal–matrix interface are used to locally characterize the change in migration behavior as a function of temperature, time and interface orientation. The relative grain boundary mobility was determined between 1250 °C and 1600 °C for four crystallographic orientations {1 0 0}, {1 1 0}, {1 1 1} and {3 1 0}. An absolute mobility of these orientations is estimated. Under fast growth conditions the morphology of single crystals shows macroscopic stepping with parts of the interface rotating to low mobility orientations. This effect represents a kinetic influence on the grain boundary morphology. The results also indicate dragging effects on microstructure coarsening, which indicate the existence of a critical driving force for grain growth. This critical driving force seems to be related to an ‘intrinsic’ interface drag similar to the solute drag, but based on intrinsic defects. At 1460 °C the growth of single crystals was significantly faster than expected from the mobility of the polycrystal and was identified as exaggerated grain growth. The findings give new insights into the recently published grain growth anomaly of strontium titanate, leading to a hypothesis based on the temperature dependent relative mobility of {1 0 0} oriented grain boundaries

  6. An Overview of Grain Growth Theories for Pure Single Phase Systems,

    Science.gov (United States)

    1986-10-01

    the fundamental causes for these distributions. This Blanc and Mocellin (1979) and Carnal and Mocellin (1981j set out to do. 7.1 Monte-Carlo Simulations...termed event B) (in 2-D) of 3-sided grains. (2) Neighbour-switching (termed event C). Blanc and Mocellin (1979) dealt with 2-D sections through...Kurtz and Carpay (1980a). 7.2 Analytical Method to Obtain fn Carnal and Mocellin (1981) obtained the distribution of grain coordination numbers in

  7. Influence of water activity and temperature on growth and fumonisin production by Fusarium proliferatum strains on irradiated wheat grains.

    Science.gov (United States)

    Cendoya, Eugenia; Monge, María Del Pilar; Chiacchiera, Stella Maris; Farnochi, María Cecilia; Ramirez, María Laura

    2018-02-02

    Wheat is the most important cereal consumed by the Argentine population. In previous studies performed in durum and common wheat grains in this country it has been observed fumonisin contamination as well as high incidence of Fusarium proliferatum. Fumonisins are toxic fungal metabolites, and consumption of fumonisin-contaminated maize has been epidemiologically associated with oesophageal cancer and neural tube defects in some human populations. Using irradiated wheat-grains, the effects of abiotic factors, temperature (15, 25, and 30°C) and water activity (a W ; 0.995, 0.98, 0.96, 0.94, 0.92, and 0.88), on mycelial growth and fumonisin biosynthesis were compared for three F. proliferatum strains isolated from wheat grains in Argentina. Although all isolates showed similar profiles of growth, the fumonisin production profiles were slightly different. Maximum growth rates were obtained at the highest a W (0.995) and 25°C, with growth decreasing as the a W of the medium was reduced. Maximum amounts of total fumonisins (FB 1 , FB 2 and FB 3 ) were produced at 0.995 a W and 15°C for 2 strains, and at 25°C and 0.995 a W for the third one. Fumonisins concentrations varied considerably depending on the a W and temperature interactions assayed. Studied strains showed different fumonisin production profiles. Two-dimensional profiles of a W by temperature interactions were developed from these data to identify areas where conditions indicate a significant risk of fumonisins accumulation on wheat. As a result, temperature and a W conditions that resulted in fumonisins production are those found during wheat grain development (especially milk and dough stages) in the field. This is the first study made using irradiated wheat grains and provides useful baseline data on conditions representing a low or a high risk for fumonisins contamination of wheat grains which is of concern because this cereal is destined mainly for human consumption. Copyright © 2017 Elsevier B.V. All

  8. Laboratory Studies of the Optical Properties and Condensation Processes of Cosmic Dust Grains

    Science.gov (United States)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; West, E.; Sheldon, R.; Witherow, W. K.; Gallagher, D. L.; Adrian, M. L.

    2002-01-01

    A laboratory facility for conducting a variety of experiments on single isolated dust particles of astrophysical interest levitated in an electrodynamics balance has been developed at NASA/Marshall Space Flight Center. The objective of the research is to employ this experimental technique for studies of the physical and optical properties of individual cosmic dust grains of 0.1-100 micron size in controlled pressure/temperatures environments simulating astrophysical conditions. The physical and optical properties of the analogs of interstellar and interplanetary dust grains of known composition and size distribution will be investigated by this facility. In particular, we will carry out three classes of experiments to study the micro-physics of cosmic dust grains. (1) Charge characteristics of micron size single dust grains to determine the photoelectric efficiencies, yields, and equilibrium potentials when exposed to UV radiation. (2) Infrared optical properties of dust particles (extinction coefficients and scattering phase functions) in the 1-30 micron region using infrared diode lasers and measuring the scattered radiation. (3) Condensation experiments to investigate the condensation of volatile gases on colder nucleated particles in dense interstellar clouds and lower planetary atmospheres. The condensation experiments will involve levitated nucleus dust grains of known composition and initial mass (or m/q ratio), cooled to a temperature and pressure (or scaled pressure) simulating the astrophysical conditions, and injection of a volatile gas at a higher temperature from a controlled port. The increase in the mass due to condensation on the particle will be monitored as a function of the dust particle temperature and the partial pressure of the injected volatile gas. The measured data will permit determination of the sticking coefficients of volatile gases and growth rates of dust particles of astrophysical interest. Some preliminary results based on

  9. Fine grained event processing on HPCs with the ATLAS Yoda system

    CERN Document Server

    Calafiura, Paolo; The ATLAS collaboration; Guan, Wen; Maeno, Tadashi; Nilsson, Paul; Oleynik, Danila; Panitkin, Sergey; Tsulaia, Vakhtang; van Gemmeren, Peter; Wenaus, Torre

    2015-01-01

    High performance computing facilities present unique challenges and opportunities for HENP event processing. The massive scale of many HPC systems means that fractionally small utilizations can yield large returns in processing throughput. Parallel applications which can dynamically and efficiently fill any scheduling opportunities the resource presents benefit both the facility (maximal utilization) and the (compute-limited) science. The ATLAS Yoda system provides this capability to HENP-like event processing applications by implementing event-level processing in an MPI-based master-client model that integrates seamlessly with the more broadly scoped ATLAS Event Service. Fine grained, event level work assignments are intelligently dispatched to parallel workers to sustain full utilization on all cores, with outputs streamed off to destination object stores in near real time with similarly fine granularity, such that processing can proceed until termination with full utilization. The system offers the efficie...

  10. Faceted shell structure in grain boundary diffusion-processed sintered Nd–Fe–B magnets

    Energy Technology Data Exchange (ETDEWEB)

    Seelam, U.M.R.; Ohkubo, T.; Abe, T.; Hirosawa, S.; Hono, K., E-mail: kazuhiro.hono@nims.go.jp

    2014-12-25

    Graphical abstract: The grain boundary diffusion process (GBDP) using a heavy rare earth elements (HRE) such as Dy and Tb is known as an effective method to enhance the coercivity of Nd–Fe–B sintered magnets without reducing remanence. This process has been industrially implemented to manufacture Nd–Fe–B based sintered magnets with high coercivity and high remanence. In this process, Dy is considered to diffuse through grain boundaries (GBs) to form (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B shells surrounding the Nd{sub 2}Fe{sub 14}B grains and the higher anisotropy field of the Dy-rich shell is considered to suppress the nucleation of reverse domains at low magnetic field. Although there are several investigations on the microstructure of HRE GBDP Nd–Fe–B magnets, no paper addressed the origin of the asymmetric formation of HRE rich shells. Based on detailed analysis of facet planes of core/shell interfaces, we propose a mechanism of the faceted core/shell microstructure formation in the GBDP sintered magnets. We believe that this gives new insights on understanding the coercivity enhancement by the GBDP. - Highlights: • Faceting was observed at the interfaces of cores and shells. • The core/shell interfaces are sharp with an abrupt change in Dy concentration. • Meting occurs at the interfaces of metalic Nd-rich/Nd{sub 2}Fe{sub 14}B phases above 685 °C due to eutectic reaction. • Solidification of Dy-enriched liquid phase from 900 °C can result in the shell formation. - Abstract: Dysprosium enriched shell structure formed by the grain boundary diffusion process (GBDP) of a sintered Nd–Fe–B magnet was characterized by using scanning electron microscopy, electron back-scattered diffraction and transmission electron microscopy. Faceted core–shell interfaces with an abrupt change in Dy concentration suggest the Dy-rich shells are formed by the solidification of the liquid phase during cooling from the GBDP temperature. The Nd-rich phases

  11. Faceted shell structure in grain boundary diffusion-processed sintered Nd–Fe–B magnets

    International Nuclear Information System (INIS)

    Seelam, U.M.R.; Ohkubo, T.; Abe, T.; Hirosawa, S.; Hono, K.

    2014-01-01

    Graphical abstract: The grain boundary diffusion process (GBDP) using a heavy rare earth elements (HRE) such as Dy and Tb is known as an effective method to enhance the coercivity of Nd–Fe–B sintered magnets without reducing remanence. This process has been industrially implemented to manufacture Nd–Fe–B based sintered magnets with high coercivity and high remanence. In this process, Dy is considered to diffuse through grain boundaries (GBs) to form (Nd 1−x Dy x ) 2 Fe 14 B shells surrounding the Nd 2 Fe 14 B grains and the higher anisotropy field of the Dy-rich shell is considered to suppress the nucleation of reverse domains at low magnetic field. Although there are several investigations on the microstructure of HRE GBDP Nd–Fe–B magnets, no paper addressed the origin of the asymmetric formation of HRE rich shells. Based on detailed analysis of facet planes of core/shell interfaces, we propose a mechanism of the faceted core/shell microstructure formation in the GBDP sintered magnets. We believe that this gives new insights on understanding the coercivity enhancement by the GBDP. - Highlights: • Faceting was observed at the interfaces of cores and shells. • The core/shell interfaces are sharp with an abrupt change in Dy concentration. • Meting occurs at the interfaces of metalic Nd-rich/Nd 2 Fe 14 B phases above 685 °C due to eutectic reaction. • Solidification of Dy-enriched liquid phase from 900 °C can result in the shell formation. - Abstract: Dysprosium enriched shell structure formed by the grain boundary diffusion process (GBDP) of a sintered Nd–Fe–B magnet was characterized by using scanning electron microscopy, electron back-scattered diffraction and transmission electron microscopy. Faceted core–shell interfaces with an abrupt change in Dy concentration suggest the Dy-rich shells are formed by the solidification of the liquid phase during cooling from the GBDP temperature. The Nd-rich phases are almost free from Dy, and

  12. The effect of grain type and processing on chewing activity in horses

    DEFF Research Database (Denmark)

    Brøkner, Christine; Nørgaard, Peder; Eriksen, Lis

    2005-01-01

    The aims of the present experiment were to study the effect of grain type and processing on chewing activity in horses. Three adult trotters (Exp.I) and 3 adult Icelandic horses (Exp.II) were fed 3 daily meals during 3 consecutive days in two 3 x 3 completely randomized block design experiments....... Meals of (Exp.I: 1.0 kg) and (Exp.II: 0.5 kg) oats, barley and wheat were fed whole, rolled and ground at 10 am, 12 pm, 2 pm. Jaw movements (JM) were identified from pressure oscillations in a tube around the mouth. The efficient chewing time (EPTIME, min/kg DM), corrected for pauses, the basic chewing...... rate (PBCR, JM/s) and the standard deviation of time interval between JM (SPDDT), which indicate chewing regularity, were estimated. The mean EPTIME was 24 and 15 min for the Icelandic and trotter horses, respectively. The EPTIME for whole grain was 20 min and shorter than for ground grain (P = 0...

  13. Experimental investigation of grain size effect on fatigue crack growth rate in turbine disc superalloy GH4169 under different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Dianyin [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China); Mao, Jianxing [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Song, Jun, E-mail: jun.song2@mcgill.ca [Mining and Materials Engineering, McGill University, Montreal, QC, Canada H3A 0C5 (Canada); Meng, Fanchao [Mining and Materials Engineering, McGill University, Montreal, QC, Canada H3A 0C5 (Canada); Shan, Xiaoming [China Aviation Powerplant Research Institute, Zhuzhou 412002 (China); Wang, Rongqiao, E-mail: wangrq@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China)

    2016-07-04

    Systematic experiments for fatigue crack growth (FCG) rate on compact tension (CT) specimens have been conducted in nickel-based superalloy GH4169 at a broad range of temperatures with a frequency of 10 Hz and a stress ratio of 0.1. In order to investigate the crack closure behavior, FCG experiments at stress ratio of 0.5 were also performed by comparing with the results at stress ration of 0.1. CT specimens were cut from three typical locations of an actual forged turbine disc to investigate the effect of grain size on the FCG behaviors. The grain size distribution, precipitates and fracture surface characteristics at different locations of the turbine disc were examined through optical microscope, transmission electron microscope (TEM) and scanning electronic microscope (SEM) analyses. Digital image correlation (DIC), optical interferometry and oxide film measurements were carried out to investigate the presence and inducement of the crack closure. Then a modified FCG model, with a distribution factor that evaluates the scattering in the FCG rate, was formulated to describe the dependence of FCG rate on grain size. Finally, the possible microscopic mechanisms to explain the grain size effect on the FCG behaviors based on crack deflection and blockage, and the crack closure inducements involving plasticity and oxide were discussed in this study.

  14. Effect of the New Plant Growth Biostimulants Based on Amino Acids on Yield and Grain Quality of Winter Wheat.

    Science.gov (United States)

    Popko, Małgorzata; Michalak, Izabela; Wilk, Radosław; Gramza, Mateusz; Chojnacka, Katarzyna; Górecki, Henryk

    2018-02-21

    Field and laboratory experiments were carried out in 2012-2013, aimed at evaluating the influence of new products stimulating plant growth based on amino acids on crop yield, characteristics of grain and content of macro- and micronutrients in winter wheat ( Triticum aestivum L.). The tests included two formulations produced in cooperation with INTERMAG Co. (Olkusz, Poland)-AminoPrim and AminoHort, containing 15% and 20% amino acids, respectively, and 0.27% and 2.1% microelements, respectively. Field experiments showed that the application of products based on amino acids influenced the increase of grain yield of winter wheat (5.4% and 11%, respectively, for the application of AminoPrim at a dose 1.0 L/ha and AminoHort at dose 1.25 L/ha) when compared to the control group without biostimulant. Laboratory tests showed an increase of technological characteristics of grain such as ash content, Zeleny sedimentation index and content of protein. The use of the tested preparations at different doses also contributed to the increase of the nutrients content in grains, in particular copper (ranging 31-50%), as well as sodium (35-43%), calcium (4.3-7.9%) and molybdenum (3.9-16%). Biostimulants based on amino acids, tested in the present study, can be recommended for an efficient agricultural production.

  15. The effects of particle size distribution and induced unpinning during grain growth

    International Nuclear Information System (INIS)

    Thompson, G.S.; Rickman, J.M.; Harmer, M.P.; Holm, E.A.

    1996-01-01

    The effect of a second-phase particle size distribution on grain boundary pinning was studied using a Monte Carlo simulation technique. Simulations were run using a constant number density of both whisker and rhombohedral particles, and the effect of size distribution was studied by varying the standard deviation of the distribution around a constant mean particle size. The results of present simulations indicate that, in accordance with the stereological assumption of the topological pinning model, changes in distribution width had no effect on the pinned grain size. The effect of induced unpinning of particles on microstructure was also studied. In contrast to predictions of the topological pinning model, a power law dependence of pinned grain size on particle size was observed at T=0.0. Based on this, a systematic deviation to the stereological predictions of the topological pinning model is observed. The results of simulations at higher temperatures indicate an increasing power law dependence of pinned grain size on particle size, with the slopes of the power law dependencies fitting an Arrhenius relation. The effect of induced unpinning of particles was also studied in order to obtain a correlation between particle/boundary concentration and equilibrium grain size. The results of simulations containing a constant number density of monosized rhombohedral particles suggest a strong power law correlation between the two parameters. copyright 1996 Materials Research Society

  16. Degradability of dry matter and crude protein of dry grains and wet grain silages from different processing corn hybrids (Zea mays

    Directory of Open Access Journals (Sweden)

    Wagner dos Reis

    2013-03-01

    Full Text Available The objective of this work was to evaluate the effect of processing two corn hybrids conserved, dry and humid grains, the dry matter (DM and crude protein (CP degradability in situ. The particle size was determined and difference was verified in MGD (Medium Geometric Diameter of processed ingredients. Three sheep were used with rumen canulated, in a completely randomized design, using a factorial outline 2 x 2 x 3, being two corn hybrid, two conservation methods and three processing forms (whole, coarsely and finely ground, with five times of incubation (3, 6, 12, 24 and 48 hours. The fraction A in SDC (silage of dent corn of DM was superior to GDC (grain of dent corn in all of the particles size. The ensiling process increased the DM solubility, reducing the fraction B in comparison to dry grain. The values regarding the fractions DP and DE the 5% per hour of the protein, were larger for SDC and GDC, it presents a decreasing when the incubation time advances. The fermentation rate was superior for SDC and GDC. The ensiling process has positive effect in the decreasing of DM and CP in comparison to GDC.

  17. From point process observations to collective neural dynamics: Nonlinear Hawkes process GLMs, low-dimensional dynamics and coarse graining.

    Science.gov (United States)

    Truccolo, Wilson

    2016-11-01

    This review presents a perspective on capturing collective dynamics in recorded neuronal ensembles based on multivariate point process models, inference of low-dimensional dynamics and coarse graining of spatiotemporal measurements. A general probabilistic framework for continuous time point processes reviewed, with an emphasis on multivariate nonlinear Hawkes processes with exogenous inputs. A point process generalized linear model (PP-GLM) framework for the estimation of discrete time multivariate nonlinear Hawkes processes is described. The approach is illustrated with the modeling of collective dynamics in neocortical neuronal ensembles recorded in human and non-human primates, and prediction of single-neuron spiking. A complementary approach to capture collective dynamics based on low-dimensional dynamics ("order parameters") inferred via latent state-space models with point process observations is presented. The approach is illustrated by inferring and decoding low-dimensional dynamics in primate motor cortex during naturalistic reach and grasp movements. Finally, we briefly review hypothesis tests based on conditional inference and spatiotemporal coarse graining for assessing collective dynamics in recorded neuronal ensembles. Published by Elsevier Ltd.

  18. Establishment and assessment of a novel cleaner production process of corn grain fuel ethanol.

    Science.gov (United States)

    Wang, Ke; Zhang, Jianhua; Tang, Lei; Zhang, Hongjian; Zhang, Guiying; Yang, Xizhao; Liu, Pei; Mao, Zhonggui

    2013-11-01

    An integrated corn ethanol-methane fermentation system was proposed to solve the problem of stillage handling, where thin stillage was treated by anaerobic digestion and then reused to make mash for the following ethanol fermentation. This system was evaluated at laboratory and pilot scale. Anaerobic digestion of thin stillage ran steadily with total chemical oxygen demand removal efficiency of 98% at laboratory scale and 97% at pilot scale. Ethanol production was not influenced by recycling anaerobic digestion effluent at laboratory and pilot scale. Compared with dried distillers' grains with solubles produced in conventional process, dried distillers' grains in the proposed system exhibited higher quality because of increased protein concentration and decreased salts concentration. Energetic assessment indicated that application of this novel process enhanced the net energy balance ratio from 1.26 (conventional process) to 1.76. In conclusion, the proposed system possessed technical advantage over the conventional process for corn fuel ethanol production. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Implicitly defined criteria for vector optimization in technological process of hydroponic germination of wheat grain

    Science.gov (United States)

    Koneva, M. S.; Rudenko, O. V.; Usatikov, S. V.; Bugaets, N. A.; Tereshchenko, I. V.

    2018-05-01

    To reduce the duration of the process and to ensure the microbiological purity of the germinated material, an improved method of germination has been developed based on the complex use of physical factors: electrochemically activated water (ECHA-water), electromagnetic field of extremely low frequencies (EMF ELF) with round-the-clock artificial illumination by LED lamps. The increase in the efficiency of the "numerical" technology for solving computational problems of parametric optimization of the technological process of hydroponic germination of wheat grains is considered. In this situation, the quality criteria are contradictory and part of them is given by implicit functions of many variables. A solution algorithm is offered without the construction of a Pareto set in which a relatively small number of elements of a set of alternatives is used to obtain a linear convolution of the criteria with given weights, normalized to their "ideal" values from the solution of the problems of single-criterion private optimizations. The use of the proposed mathematical models describing the processes of hydroponic germination of wheat grains made it possible to intensify the germination process and to shorten the time of obtaining wheat sprouts "Altayskaya 105" for 27 hours.

  20. Grain growth behavior of Li{sub 4}SiO{sub 4} pebbles fabricated by agar method for tritium breeder

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Maoqiao [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Zhang, Yingchun, E-mail: zycustb@126.com [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Zhang, Yun; Wang, Chaofu; Liu, Wei [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Yu, Yonghong [Department of Physics, Renmin University of China, Beijing, 100872 (China)

    2016-11-15

    Highlights: • Grain sizes of Li{sub 4}SiO{sub 4} were adjusted by different silicon sources. • Grain growth exponent of Li{sub 4}SiO{sub 4} was about 3. • Grain growth activation energy of Li{sub 4}SiO{sub 4} was about 125.54 kJ/mol. • Grain growth of Li{sub 4}SiO{sub 4} pebble was controlled by vapor transport. - Abstract: The Li{sub 4}SiO{sub 4} tritium breeding pebbles will be filled in the blanket and used for 2 years or more at high temperatures, which would increase the grain size and affect tritium release. Hence, grain sizes of the Li{sub 4}SiO{sub 4} pebbles fabricated by agar method were investigated, and two kinds of different silicon sources (crystal and amorphous SiO{sub 2}) with different particle sizes were used. The particle size of SiO{sub 2} could affect grain size and density of the Li{sub 4}SiO{sub 4} pebble. And the isothermal sintering was carried out to study the grain growth kinetics of Li{sub 4}SiO{sub 4}. The grain growth exponent (n) and the activation energy (Q) were calculated by the phenomenological kinetic equation. The calculated n values were 4.10, 3.98, 3.34 and 2.96, and corresponding Q values were 152.15, 147.99, 125.54 and 110.58 kJ/mol, respectively. At the higher sintering temperatures (950 and 1000 °C), the grain growth of Li{sub 4}SiO{sub 4} was controlled by vapor transport.

  1. Precipitation Processes during Non-Isothermal Ageing of Fine-Grained 2024 Alloy

    Directory of Open Access Journals (Sweden)

    Kozieł J.

    2016-03-01

    Full Text Available Mechanical alloying and powder metallurgy procedures were used to manufacture very fine-grained bulk material made from chips of the 2024 aluminum alloy. Studies of solution treatment and precipitation hardening of as-received material were based on differential scanning calorimetry (DSC tests and TEM/STEM/EDX structural observations. Structural observations complemented by literature data lead to the conclusion that in the case of highly refined structure of commercial 2024 alloys prepared by severe plastic deformation, typical multi-step G-P-B →θ” →θ’ →θ precipitation mechanism accompanied with G-P-B →S” →S’ →S precipitation sequences result in skipping the formation of metastable phases and direct growth of the stable phases. Exothermic effects on DSC characteristics, which are reported for precipitation sequences in commercial materials, were found to be reduced with increased milling time. Moreover, prolonged milling of 2024 chips was found to shift the exothermic peak to lower temperature with respect to the material produced by means of common metallurgy methods. This effect was concluded to result from preferred heterogeneous nucleation of particles at subboundaries and grain boundaries, enhanced by the boundary diffusion in highly refined structures.

  2. Grain growth control and transparency in spark plasma sintered self-doped alumina materials

    International Nuclear Information System (INIS)

    Suarez, M.; Fernandez, A.; Menendez, J.L.; Torrecillas, R.

    2009-01-01

    Doping alumina particles with aluminum alkoxides allows dense spark plasma sintered (SPSed) materials to be obtained that have a refined grain size compared to pure materials, which is critical for their transparency. An optical model considering pore and grain size distributions has been developed to obtain information about porosity in dense materials. This work suggests that the atomic diffusion mechanisms do not depend on the sintering technique. A reduction in the activation energy by a factor of 2 has been found in SPSed materials.

  3. THE INFLUENCE OF PROCESSED PRODUCTS OF WHEAT GERM ON GRAIN BREAD QUALITY

    OpenAIRE

    E. I. Ponomareva; N. N. Alekhinа; I. A. Bakayeva

    2014-01-01

    Development and introduction of new types of bakery products with increased nutritional value is one of the basic and urgent problems in the bakery industry. The solution of it is the use of whole grains, as well as secondary products of their processing. The use of by-products of wheat germ (oil, oilcake, oilcake flour), which are rich in proteins and enhances the nutritional value of products is considered to be a promising area in the bakery industry. At the same time the program objective...

  4. INNOVATIVE TECHNOLOGIES FOR SOIL PROCESSING AND EFFICIENCY OF THEIR APPLICATION IN THE GROWING OF GRAIN CULTURES IN CHERKASY REGION

    Directory of Open Access Journals (Sweden)

    Ulanchuk V.

    2018-01-01

    Full Text Available Introduction. Scientific and technological progress plays an important role in improving the efficiency of the production of grain products. At the same time, it also has a negative impact on the ecology of soils. World experience shows the possibility of suspending and overcoming destructive land processes by introducing innovative soil cultivation technologies in the cultivation of agricultural crops. Purpose. This article aims to substantiate expediency of introduction of innovative resource-saving technologies of soil cultivation at cultivation of grain crops in Cherkasy region. Results. In the article it is proved that the efficiency of grain production in agricultural enterprises of Cherkasy region, which are using minimal (Mini-till and zero (No-till tillage technologies, in comparison with enterprises that use traditional grain growing technology, have indicators, as the price of sale of 1 centner of grain, the profit per 1 centner of grain and the level of profitability, that are much higher. Thus, the price of 1 centner of grain produced by the “LNZ-Agro” (Mini-till in 2013-2015 was higher 573.86 UAH, at the “Shpola-Agro-Industry” (No-till at 390,94 UAH, profit per 1 centner grain is higher than 477.23 and 249.14 UAH; the level of profitability of grain – higher than 201.5 and 71.8 percentage points. A similar situation is observed in the production of the main grain crops (wheat and maize for grain. With the application of the newest soil cultivation technologies, there is a decrease in the calculation of fuel consumption and depreciation deductions per hectare. The expediency of using resource-saving technologies for soil tillage during the cultivation of grain products in agricultural enterprises of the Cherkasy region also indicates by such indicator as the amount of profit per 1 hectare of crops. So, LNZ-Agro (Mini-till for one hectare of crops received a profit of 43947 UAH, “Shpola-Agro-Industry” (No-till –16491

  5. What is this link doing here? Beginning a fine-grained process of identifying reasons for academic hyperlink creation

    Directory of Open Access Journals (Sweden)

    Thelwall Mike

    2003-01-01

    Full Text Available The purpose of this paper is to begin a [fine-grained] process of differentiating between creation motivations for links in academic Web sites and citations in journals on the basis that they are very different phenomena.

  6. Integrated Intelligent Modeling, Design and Control of Crystal Growth Processes

    National Research Council Canada - National Science Library

    Prasad, V

    2000-01-01

    .... This MURI program took an integrated approach towards modeling, design and control of crystal growth processes and in conjunction with growth and characterization experiments developed much better...

  7. A record-driven growth process

    International Nuclear Information System (INIS)

    Godrèche, C; Luck, J M

    2008-01-01

    We introduce a novel stochastic growth process, the record-driven growth process, which originates from the analysis of a class of growing networks in a universal limiting regime. Nodes are added one by one to a network, each node possessing a quality. The new incoming node connects to the pre-existing node with best quality, that is, with record value for the quality. The emergent structure is that of a growing network, where groups are formed around record nodes (nodes endowed with the best intrinsic qualities). Special emphasis is put on the statistics of leaders (nodes whose degrees are the largest). The asymptotic probability for a node to be a leader is equal to the Golomb–Dickman constant ω = 0.624 329 ..., which arises in problems of combinatorial nature. This outcome solves the problem of the determination of the record breaking rate for the sequence of correlated inter-record intervals. The process exhibits temporal self-similarity in the late-time regime. Connections with the statistics of the cycles of random permutations, the statistical properties of randomly broken intervals, and the Kesten variable are given

  8. High day- and night-time temperatures affect grain growth dynamics in contrasting rice genotypes

    NARCIS (Netherlands)

    Shi, Wanju; Yin, Xinyou; Struik, Paul C.; Solis, Celymar; Xie, Fangming; Schmidt, Ralf C.; Huang, Min; Zou, Yingbin; Ye, Changrong; Jagadish, S.V.K.

    2017-01-01

    Rice grain yield and quality are predicted to be highly vulnerable to global warming. Five genotypes including heat-tolerant and susceptible checks, a heat-tolerant near-isogenic line and two hybrids were exposed to control (31 °C/23 °C, day/night), high night-time temperature (HNT; 31 °C/30 °C),

  9. Heat stress in wheat (Triticum aestivum L.): Effects on grain growth and quality traits

    NARCIS (Netherlands)

    Spiertz, J.H.J.; Hamer, R.J.; Xu, H.; Primo-Martin, C.; Don, C.; Putten, P.E.L. van der

    2006-01-01

    Heat stress effects on grain dry mass and quality were studied in spring wheat genotypes (Triticum aestivum L.). Three cultivars were chosen with respect to heat tolerance: Lavett (genotype 1), selected for temperate growing conditions and two CIMMYT cultivars, Ciano-79 (genotype 2) and Attila

  10. Modeling the effect of neighboring grains on twin growth in HCP polycrystals

    Science.gov (United States)

    Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; Tomé, C. N.

    2017-09-01

    In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that account for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled by the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.

  11. Growth, Structure and Firm Dynamics in Grain Markets: The Case of ...

    African Journals Online (AJOL)

    Optiplex 7010 Pro

    market, firms faced with a U-shaped average cost curve will grow until they reach the ... Regulation and institutional challenges may also deter firm owners from making .... owners/managers account for only 10% of the grain traders. Women ...

  12. Na-assisted grain growth in CZTS nanoparticle thin films for solar cell applications

    DEFF Research Database (Denmark)

    Engberg, Sara Lena Josefin; Crovetto, Andrea; Hansen, Ole

    2017-01-01

    signal increased by a factor of 200 after Na-inclusion. Without Na, the grains were very difficult to sinter, the film was porous, and the photoluminescence was low. A concentration of Na/(Cu+Zn+Sn)=30% was necessary for the densification of the absorber, which is significantly higher than that used...

  13. Short communication: Effects of processing methods of barley grain in starter diets on feed intake and performance of dairy calves.

    Science.gov (United States)

    Jarrah, A; Ghorbani, G R; Rezamand, P; Khorvash, M

    2013-01-01

    The present study was conducted to evaluate the effects of different processing methods of barley grain in starter rations on feed intake, average daily gain, feed efficiency, skeletal growth, fecal score, and rumen pH of dairy calves. Thirty-two Holstein dairy calves (16 female and 16 male) were randomly allocated to 1 of 4 treatments consisting of coarse ground, whole, steam-rolled, or roasted barley from d 4 to 56 of birth in a completely randomized design. Starter diets were formulated to have similar ingredients and composition. All calves had free access to water and feed throughout the study period and received 4 L of milk/d from a bottle from d 4 to 41, 2L/d from d 41 to 45, and weaning occurred on d 45. Feed intake and fecal score were recorded daily. Body weight and skeletal growth measures were recorded on d 4 (beginning of the study), 45, and 56. Rumen fluid and blood samples were collected on d 35, 45, and 56. Data were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). The results indicate that different methods of processing barley had no detectable effect on dry matter intake, average daily gain, and feed efficiency and that skeletal growth, health, and rumen pH were not affected by dietary treatments. In conclusion, the results show that different processing methods of barley included in starter diets had no detectable effect on the performance of dairy calves under our experimental conditions. Therefore, feeding whole or coarsely ground barley would be a more economical method compared with steam rolled or roasted barley. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  14. Numerical Simulation of Shear Slitting Process of Grain Oriented Silicon Steel using SPH Method

    Directory of Open Access Journals (Sweden)

    Bohdal Łukasz

    2017-12-01

    Full Text Available Mechanical cutting allows separating of sheet material at low cost and therefore remains the most popular way to produce laminations for electrical machines and transformers. However, recent investigations revealed the deteriorating effect of cutting on the magnetic properties of the material close to the cut edge. The deformations generate elastic stresses in zones adjacent to the area of plastically deformed and strongly affect the magnetic properties. The knowledge about residual stresses is necessary in designing the process. This paper presents the new apprach of modeling residual stresses induced in shear slitting of grain oriented electrical steel using mesh-free method. The applications of SPH (Smoothed Particle Hydrodynamics methodology to the simulation and analysis of 3D shear slitting process is presented. In experimental studies, an advanced vision-based technology based on digital image correlation (DIC for monitoring the cutting process is used.

  15. CURVED WALLS: GRAIN GROWTH, SETTLING, AND COMPOSITION PATTERNS IN T TAURI DISK DUST SUBLIMATION FRONTS

    Energy Technology Data Exchange (ETDEWEB)

    McClure, M. K.; Calvet, N.; Hartmann, L.; Ingleby, L. [Department of Astronomy, The University of Michigan, 500 Church Street, 830 Dennison Building., Ann Arbor, MI 48109 (United States); D' Alessio, P. [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán (Mexico); Espaillat, C. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Sargent, B. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Watson, D. M. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Hernández, J., E-mail: melisma@umich.edu, E-mail: ncalvet@umich.edu, E-mail: lhartm@umich.edu, E-mail: lingleby@umich.edu, E-mail: p.dalessio@astrosmo.unam.mx, E-mail: cespaillat@cfa.harvard.edu, E-mail: baspci@rit.edu, E-mail: dmw@pas.rochester.edu, E-mail: hernandj@cida.ve [Centro de Investigaciones de Astronomía (CIDA), Mérida 5101-A (Venezuela, Bolivarian Republic of)

    2013-10-01

    The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best fits to the near- and mid-IR excesses are found for curved, two-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe) = 0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass accretion rates decrease from 10{sup –8} to 10{sup –10} M{sub ☉} yr{sup –1}, the maximum grain size in the lower layer decreases from ∼3 to 0.5 μm. We attribute this to a decrease in fragmentation and turbulent support for micron-sized grains with decreasing viscous heating. The atmosphere of these disks is depleted of dust with dust-gas mass ratios 1 × 10{sup –4} of the interstellar medium (ISM) value, while the midplane is enhanced to eight times the ISM value. For all accretion rates, the wall contributes at least half of the flux in the optically thin 10 μm silicate feature. Finally, we find evidence for an iron gradient in the disk, suggestive of that found in our solar system.

  16. CURVED WALLS: GRAIN GROWTH, SETTLING, AND COMPOSITION PATTERNS IN T TAURI DISK DUST SUBLIMATION FRONTS

    International Nuclear Information System (INIS)

    McClure, M. K.; Calvet, N.; Hartmann, L.; Ingleby, L.; D'Alessio, P.; Espaillat, C.; Sargent, B.; Watson, D. M.; Hernández, J.

    2013-01-01

    The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best fits to the near- and mid-IR excesses are found for curved, two-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe) = 0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass accretion rates decrease from 10 –8 to 10 –10 M ☉ yr –1 , the maximum grain size in the lower layer decreases from ∼3 to 0.5 μm. We attribute this to a decrease in fragmentation and turbulent support for micron-sized grains with decreasing viscous heating. The atmosphere of these disks is depleted of dust with dust-gas mass ratios 1 × 10 –4 of the interstellar medium (ISM) value, while the midplane is enhanced to eight times the ISM value. For all accretion rates, the wall contributes at least half of the flux in the optically thin 10 μm silicate feature. Finally, we find evidence for an iron gradient in the disk, suggestive of that found in our solar system

  17. Malting process optimization for protein digestibility enhancement in finger millet grain.

    Science.gov (United States)

    Hejazi, Sara Najdi; Orsat, Valérie

    2016-04-01

    Finger millet (Eleusine coracana) is a nutritious, gluten-free, and drought resistant cereal containing high amounts of protein, carbohydrate, and minerals. However, bio-availability of these nutrients is restricted due to the presence of an excessive level of anti-nutrient components, mainly phytic acid, tannin, and oxalate. It has been shown that a well-designed malting/germination process can significantly reduce these anti-nutrients and consequently enhance the nutrient availability. In the present study, the effects of two important germination factors, duration and temperature, on the enhancement of in-vitro protein digestibility of finger millet were thoroughly investigated and optimized. Based on a central composite design, the grains were germinated for 24, 36, and 48 h at 22, 26, and 30 °C. For all factor combinations, protein, peptide, phytic acid, tannin, and oxalate contents were evaluated and digestibility was assessed. It was shown that during the malting/germinating process, both temperature and duration factors significantly influenced the investigated quantities. Germination of finger millet for 48 h at 30 °C increased protein digestibility from 74 % (for native grain) up to 91 %. Besides, it notably decreased phytic acid, tannin, and oxalate contents by 45 %, 46 %, and 29 %, respectively. Linear correlations between protein digestibility and these anti-nutrients were observed.

  18. Cellulase production using different streams of wheat grain- and wheat straw-based ethanol processes.

    Science.gov (United States)

    Gyalai-Korpos, Miklós; Mangel, Réka; Alvira, Pablo; Dienes, Dóra; Ballesteros, Mercedes; Réczey, Kati

    2011-07-01

    Pretreatment is a necessary step in the biomass-to-ethanol conversion process. The side stream of the pretreatment step is the liquid fraction, also referred to as the hydrolyzate, which arises after the separation of the pretreated solid and is composed of valuable carbohydrates along with compounds that are potentially toxic to microbes (mainly furfural, acetic acid, and formic acid). The aim of our study was to utilize the liquid fraction from steam-exploded wheat straw as a carbon source for cellulase production by Trichoderma reesei RUT C30. Results showed that without detoxification, the fungus failed to utilize any dilution of the hydrolyzate; however, after a two-step detoxification process, it was able to grow on a fourfold dilution of the treated liquid fraction. Supplementation of the fourfold-diluted, treated liquid fraction with washed pretreated wheat straw or ground wheat grain led to enhanced cellulase (filter paper) activity. Produced enzymes were tested in hydrolysis of washed pretreated wheat straw. Supplementation with ground wheat grain provided a more efficient enzyme mixture for the hydrolysis by means of the near-doubled β-glucosidase activity obtained.

  19. Spatial Price Discovery, Dynamics, and Leadership in Evolving Distiller’s Grain Markets

    OpenAIRE

    Van Winkle, Tyler W.; Schroeder, Ted C.

    2008-01-01

    Recent dramatic growth in corn-based bio-refining has generated considerable growth in the by-product of this process, distiller’s grains. Distiller’s grains are rapidly becoming important livestock feed ingredient sources. However, little public market information is available on distiller’s grain. This study determines spatial and temporal price relationships among distiller’s grain markets. Results indicate spatial distiller’s grain markets operate somewhat independently suggesting potenti...

  20. Fine-grained zirconium-base material

    Science.gov (United States)

    Van Houten, G.R.

    1974-01-01

    A method is described for making zirconium with inhibited grain growth characteristics, by the process of vacuum melting the zirconium, adding 0.3 to 0.5% carbon, stirring, homogenizing, and cooling. (Official Gazette)

  1. Box-scan: A novel 3DXRD method for studies of recrystallization and grain growth

    DEFF Research Database (Denmark)

    Lyckegaard, Allan; Poulsen, Henning Friis; Ludwig, Wolfgang

    2012-01-01

    Within the last decade a number of x-ray diffraction methods have been presented for non-destructive 3D characterization of polycrystalline materials. 3DXRD [1] and Diffraction Contrast Tomography [2,3,4] are examples of such methods providing full spatial and crystallographic information...... of the individual grains. Both methods rely on specially designed high-resolution near-field detectors for acquire the shape of the illuminated grains, and therefore the spatial resolution is for both methods limited by the resolution of the detector, currently ~2 micrometers. Applying these methods using...... for dynamic studies requiring high temporal resolution and set-ups involving bulky sample environments (e.g. furnaces, stress-rigs etc.)...

  2. Magnetic losses reduction in grain oriented silicon steel by pulse and continuous fiber laser processing

    Science.gov (United States)

    Petryshynets, Ivan; Kováč, František; Puchý, Viktor; Šebek, Martin; Füzer, Ján; Kollár, Peter

    2018-04-01

    The present paper shows the impact of different laser scribing conditions on possible reduction of magnetic losses in grain oriented electrical steel sheets. The experimental Fe-3%Si steel was taken from industrial line after final box annealing. The surface of investigated steel was subjected to fiber laser processing using both pulse and continuous scribing regimes in order to generate residual thermal stresses inducing the magnetic domains structure refinement. The magnetic losses of experimental samples before and after individual laser scribing regimes were tested in AC magnetic field with 50Hz frequency and induction of 1.5T. The most significant magnetic losses reduction of 38% was obtained at optimized conditions of continuous laser scribing regime. A semi quantitative relationship has been found between the domain patterns and the used fiber laser processing.

  3. Magnetic losses reduction in grain oriented silicon steel by pulse and continuous fiber laser processing

    Directory of Open Access Journals (Sweden)

    Ivan Petryshynets

    2018-04-01

    Full Text Available The present paper shows the impact of different laser scribing conditions on possible reduction of magnetic losses in grain oriented electrical steel sheets. The experimental Fe-3%Si steel was taken from industrial line after final box annealing. The surface of investigated steel was subjected to fiber laser processing using both pulse and continuous scribing regimes in order to generate residual thermal stresses inducing the magnetic domains structure refinement. The magnetic losses of experimental samples before and after individual laser scribing regimes were tested in AC magnetic field with 50Hz frequency and induction of 1.5T. The most significant magnetic losses reduction of 38% was obtained at optimized conditions of continuous laser scribing regime. A semi quantitative relationship has been found between the domain patterns and the used fiber laser processing.

  4. High-strength bolt-forming of fine-grained aluminum alloy 6061 with a continuous hybrid process

    International Nuclear Information System (INIS)

    Kim, Ji Hun; Hwang, Sun Kwang; Im, Yong-Taek; Son, Il-Heon; Bae, Chul Min

    2012-01-01

    Highlights: ► Fine-grained AA6061-O was produced by a continuous hybrid process. ► It consists of rolling, ECAP, and drawing. ► High-strength bolt was manufactured with the fine-grained AA6061-O. ► The UTS and micro-hardness of the bolt was increased by 50%. ► The route C was better in making a uniform micro-hardness distribution in the bolt. - Abstract: It is well known that the development of a continuous manufacturing process to apply severe plastic deformation (SPD) is a major challenge for industrial usages to improve the mechanical properties of the material through grain refinement. In this study, fine-grained AA6061-O wire was manufactured by a two-pass hybrid process consisting of drawing, equal channel angular pressing and rolling in a continuous manner to investigate the effects of processing routes for two different routes, A and C, on the variation of ultimate tensile strength (UTS) and micro-hardness distribution. The UTS value (185 MPa) of the specimen processed by the two-pass hybrid process with route A was higher than that of 171 MPa obtained from the two-pass wire-drawing process and was equivalent to the level of 184 MPa processed by the three-pass wire-drawing process. The average micro-hardness value (Hv 58.0) obtained from the two-pass hybrid process through route C was the highest among all the cases. According to transmission electron microscopy, the original grain was subdivided and elongated owing to deformation during the processes. The specimen processed by the two-pass hybrid process through route C showed smaller deformation bands and had potentially higher angle grain boundaries compared to the specimen processed by the two-pass wire-drawing process. Finally, the high-strength bolt was manufactured using the fine-grained AA6061-O wire prepared by the continuous hybrid process to check its formability. A ductile fracture at the first thread right above the jaw was observed in the bolt tension test of the manufactured bolt

  5. Impact of integrated nutrient management on growth and grain yield of wheat under irrigated cropping system

    International Nuclear Information System (INIS)

    Nawab, K.; Amanullah, A.; Shah, P.; Arif, M.; Khan, A.M.

    2011-01-01

    Field study was conducted during 2001-02 and 2002-03 to investigate the effect of cropping patterns and farm yard manure, potassium and zinc on the grain yield of wheat. Trials were conducted at Agricultural Research Farm, KPK Agricultural University Peshawar, Pakistan. Two factors cropping patterns and manures/fertilizers were studied in the experiment. Randomized complete block design was used with split plot arrangements and four replications having net plot size of 12 m/sup 2/. Wheat variety Ghaznavi-98 was sown in November soon after ploughing the soil at proper moisture level suitable for wheat seed germination. Five cropping patterns were allotted to main plots and the eight combinations of FYM, K and Zn to the sub-plots. Same plots were used for next year sowing. Effects of five cropping patterns i.e., rice-wheat, maize-wheat, sunflower-wheat, sorghum-wheat and pigeon pea-wheat and three organic and in-organic fertilizers (Farmyard Manure, Potassium and Zinc) on subsequent wheat crop were observed. Highest grain yield was obtained when wheat was planted after pigeon pea. Manures/fertilizer application (Farmyard Manure, Potassium and Zinc) produced significantly higher grain yield than the control plots. The findings of the present study revealed that leguminous crops can significantly increase the yield of succeeding crops. Thus use of Farmyard Manure, Potassium and Zinc should be included in integrated crop management approaches for sustainable agriculture. (author)

  6. Plant growth-promoting actinobacteria: a new strategy for enhancing sustainable production and protection of grain legumes.

    Science.gov (United States)

    Sathya, Arumugam; Vijayabharathi, Rajendran; Gopalakrishnan, Subramaniam

    2017-06-01

    Grain legumes are a cost-effective alternative for the animal protein in improving the diets of the poor in South-East Asia and Africa. Legumes, through symbiotic nitrogen fixation, meet a major part of their own N demand and partially benefit the following crops of the system by enriching soil. In realization of this sustainability advantage and to promote pulse production, United Nations had declared 2016 as the "International Year of pulses". Grain legumes are frequently subjected to both abiotic and biotic stresses resulting in severe yield losses. Global yields of legumes have been stagnant for the past five decades in spite of adopting various conventional and molecular breeding approaches. Furthermore, the increasing costs and negative effects of pesticides and fertilizers for crop production necessitate the use of biological options of crop production and protection. The use of plant growth-promoting (PGP) bacteria for improving soil and plant health has become one of the attractive strategies for developing sustainable agricultural systems due to their eco-friendliness, low production cost and minimizing consumption of non-renewable resources. This review emphasizes on how the PGP actinobacteria and their metabolites can be used effectively in enhancing the yield and controlling the pests and pathogens of grain legumes.

  7. Multipass comminution process to produce precision wood particles of uniform size and shape with disrupted grain structure from wood chips

    Science.gov (United States)

    Dooley, James H; Lanning, David N

    2014-05-27

    A process of comminution of wood chips (C) having a grain direction to produce a mixture of wood particles (P), wherein the wood chips are characterized by an average length dimension (L.sub.C) as measured substantially parallel to the grain, an average width dimension (W.sub.C) as measured normal to L.sub.C and aligned cross grain, and an average height dimension (H.sub.C) as measured normal to W.sub.C and L.sub.C, and wherein the comminution process comprises the step of feeding the wood chips in a direction of travel substantially randomly to the grain direction one or more times through a counter rotating pair of intermeshing arrays of cutting discs (D) arrayed axially perpendicular to the direction of wood chip travel.

  8. Application of image processing and different types of imaging devices for three-dimensional imaging of coal grains

    OpenAIRE

    Oleszko, K.; Mlynarczuk, M.; Sitek, L. (Libor); Staš, L. (Lubomír)

    2015-01-01

    Precise particle size measurements are important in many aspects of engineering geology, e.g. in mineral processing and the study of methane hazard in coal mines. The volume of grains, estimated exclusively on the basis of dimensions of the grains differs tens of percent from the volume obtained from 3D digital measurements. This confirms that full three-dimensional automatic imaging can be used in the measurements of the particles. The paper discusses the technique of three-dimensional imagi...

  9. Silicon treatment to rice (oryza sativa l. cv 'gopumbyeo') plants during different growth periods and its effects on growth and grain yield

    International Nuclear Information System (INIS)

    Kim, Y.H.; Waqas, M.; Kamran, M.

    2012-01-01

    Silicon (Si) has been considered a beneficial element for plant growth. We have assessed the effects of Si application on rice (Oryza sativa L.) growth and its grain yield at field level. For this, we performed two experiments. In experiment 1, we applied Si of three different concentrations (liquid Si-10, 25 and 36%) to the seedbed of rice before transplantation into paddy field. The results of this experiment showed that Si application to rice seedbeds did not affected the rice plant height and shoot fresh weight but its application significantly increased the pushing resistance of rice plants from 12.2-16.7% as compared with water applied control plants. The lodging index of Si treated rice plants significantly decreased (13.7% on LS-25) as compared with control. Similarly, Si treated plants had significantly higher yield. Upon Si treatment (LS-36), the grain yield per 10 acre and panicles per plant were 15.1% and 6. 3% higher than the water treated control plants respectively. The best concentration (LS-36%) revealed in the first experiment was foliar applied at 10 days before heading stage, initial tilling stage and panicle initiation stage to the rice leaves and we observed that shoot biomass was not significantly different between control and Si treated plants. However, significantly higher pushing resistance (10.5%-13.8%) and plant height (12.2%-16.7%) were observed while lower lodging index (7.6-7.8%) was recorded for Si treated plants as compared to control plants. Similarly, Si application increased the number of panicles per plant as well as the grain yield per 10 acre as compared to control. In conclusion, the Si application can significantly regulate plant growth and yield if applied at proper time with feasible concentration. (author)

  10. Field Evaluation of Cereal Combine Harvesters Processing Losses on JD-955 and JD-1165 Combines Equipped with Grain Loss Monitor

    Directory of Open Access Journals (Sweden)

    M.R Mostofi Sarkari

    2014-09-01

    Full Text Available Grain loss monitors are installed on combine harvester and make it possible to measure grain loss on different parts of the combine. The instrument permits the operator to adjust a proper ground speed to keep grain loss within an acceptable range. In this study a loss monitoring system was implemented to measure grain losses continuously on straw walker and sieves. Two grain loss monitors (KEE and TeeJet were installed behind the straw walker and the sieves of JD-955 and JD-1165 combine harvesters. Harvesting performance parameters such as combine total and processing losses were then measured. To evaluate the precision and accuracy of the instruments, the measured and monitored losses were compared and investigated. The results of a two-year research showed that the average processing loss of the combine harvesters with 10-12% grain moisture content and 750 rpm drum speed was 0.82% which is whitin the acceptable range recommended by ASAE Standard No. S343.3. Furthermore, there was no significant difference between the measured and monitored values of processing loss.

  11. Effect of Plant Growth Promoting Rhizobacteria (PGPR on Phenological Traits, Grain Yield and Yield Components of Three Maize (Zea mays L. Cultivars

    Directory of Open Access Journals (Sweden)

    A Soleimani Fard

    2013-11-01

    Full Text Available To evaluate the effect of bio-fertilize on yield and its components in maize cultivars, an split plot experiment based on randomized complete bock design with three replications in was conducted in Payam-noor University of Ilam, Iran, in 2009-2010. Treatments were cultivar (SC604, SC704 and SC807 assigned to main plots and bio-fertilizer (non- inoculation, inoculation with Azetobacter, Azospirillum and dual inoculation ofAzotobacterand Azospirillum to subplots. The effect of cultivar on days to maturity, plant height, dry matter, ear length, stem diameter, number of grain per ear row, 1000-grain weight, grain yield, biological yield and protein content was significant cultivar. SC 704 had the highest dry matter (259.5 g.m-2, plant height (201.1 cm, number of grain per ear row (42.8 grain, grain yield (10850 kg.m-2, and biological yield (22040 kg.m-2. The effect of plant growth promoting rhizobacteria on all traits expect harvest index was significant. Dual inoculation ofAzotobacterand Azospirillum had the longest days to ear initiation (71.2 days, days to maturity (115.4 day, number of leaves above ear (5.6 ear, dry matter (240.4 g.m-2, ear length (24.3 cm, plant height (212.4 cm, seed number of rows per ear (14.5 row, number of grains per row (44.2 grain, grain yield (10190 kg.m-2, biological yield (21320 kg.m-2 and protein content (10.7%. Interaction effect of cultivar× plant growth promoting rhizobacteria on grain yield was significant. The highest and lowest grain yield was obtained from SC 704 and application of dual inoculation ofAzotobacterand Azospirillum (12320 kg.ha-1 and lowest from SC 604 when inoculation treatments were not used 7570 kg.ha-1 respectively.

  12. ECONOMIC ESSENCE OF MODERN INVESTMENT PROCESSES IN THE GRAIN PROCESSING INDUSTRY

    Directory of Open Access Journals (Sweden)

    Inna Kanashkina

    2015-11-01

    Full Text Available The subject of the research is theoretical and methodological bases of formation of effective investment in priorities feed processing industry in Ukraine. The object of research is the investment process in feed processing Ukrainian industry, the main direction and the way to increase the efficiency of the investment process in the industry. The aim is to develop an integrated approach to the study of the economic substance of investments to improve the methods to determine their effectiveness, the study of factors of investment environment, study methodology for determining business risk, development of proposals of the priority areas of investing in feed processing industry, the formation of effective investment strategies for its development in the conditions of market transformation. Methods. We used the following methods: dialectical, abstract logic, Economics and Statistics and the systemic-functional methods of knowledge of economic processes. The dialectical method has allowed the author to analyze the development of research in the last five years, identified reserves and propose ways for its further development. Abstract-logical method of waste classification of the factors influencing the efficiency of the investment process in the industry, the methodological approaches to the formation of the components of the conceptual apparatus studied category. Economic-statistical method used in the study and synthesis of trends and patterns of the dynamics of the industry at the present stage. Systemic-functional method allowed to generalize the theoretical and methodological foundations of development effectiveness feed processing industry. The study also used methods: a comparative analysis – for comparing actual data reporting and previous years; model approach – to determine the entrepreneurial risk in the enterprises of the industry; expert assessments and cost approaches to identify key trends and ways to improve the country

  13. Dynamic testing at high strain rates of an ultrafine-grained magnesium alloy processed by ECAP

    International Nuclear Information System (INIS)

    Li, B.; Joshi, S.; Azevedo, K.; Ma, E.; Ramesh, K.T.; Figueiredo, R.B.; Langdon, T.G.

    2009-01-01

    A ZK60 magnesium alloy was processed by equal-channel angular pressing (ECAP) at 473 K to produce a grain size of ∼0.8 μm and it was then tested under dynamic conditions at strain rates up to 4.0 x 10 3 s -1 using a split-Hopkinson bar. The stress-strain curves in dynamic testing exhibited upwards concave curvature suggesting the occurrence of twinning. Examination by transmission electron microscopy showed that dislocation slip played a major role in the flow behavior with dislocation accumulation as the main source of work hardening. An identification of Burgers vectors revealed the extensive presence of prismatic dislocations. Rod-shaped Mg 1 (Zn,Zr) 1 precipitates present in the as-received alloy become fragmented and overaged during ECAP.

  14. Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys

    Science.gov (United States)

    Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

    2018-01-01

    Al3TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al3Zr and Al3Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al3TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al3Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al3(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al3(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al3Zr-core or Al3Zr(Sc1-1)-core encircled with an Sc-rich shell forms. PMID:29677155

  15. Role of interfacial defect creation-annihilation processes at grain boundaries on the diffusional creep of polycrystalline alumina

    International Nuclear Information System (INIS)

    Ikuma, Y.; Gordon, R.S.

    1981-01-01

    It is generally assumed in the diffusional creep of a polycrystalline solid that grain boundaries act as perfect sources and sinks for lattice defects. However, if this assumption is not valid, then diffusional creep can become rate limited by interfacial defect reactions at grain boundaries. Steady state diffusional creep data will be presented at 1450 to 1500 0 C for polycrystalline alumina doped with Ti and a Mg-Ti co-dopant, which are consistent with interfacial controlled kinetics over an intermediate grain size range. A new type of creep deformation map will be presented which reveals the range of grain sizes and impurity concentrations over which interfacial defect creation and/or annihilation processes are important in the steady state creep of polycrystalline alumina

  16. Coarse-graining and hybrid methods for efficient simulation of stochastic multi-scale models of tumour growth

    Science.gov (United States)

    de la Cruz, Roberto; Guerrero, Pilar; Calvo, Juan; Alarcón, Tomás

    2017-12-01

    The development of hybrid methodologies is of current interest in both multi-scale modelling and stochastic reaction-diffusion systems regarding their applications to biology. We formulate a hybrid method for stochastic multi-scale models of cells populations that extends the remit of existing hybrid methods for reaction-diffusion systems. Such method is developed for a stochastic multi-scale model of tumour growth, i.e. population-dynamical models which account for the effects of intrinsic noise affecting both the number of cells and the intracellular dynamics. In order to formulate this method, we develop a coarse-grained approximation for both the full stochastic model and its mean-field limit. Such approximation involves averaging out the age-structure (which accounts for the multi-scale nature of the model) by assuming that the age distribution of the population settles onto equilibrium very fast. We then couple the coarse-grained mean-field model to the full stochastic multi-scale model. By doing so, within the mean-field region, we are neglecting noise in both cell numbers (population) and their birth rates (structure). This implies that, in addition to the issues that arise in stochastic-reaction diffusion systems, we need to account for the age-structure of the population when attempting to couple both descriptions. We exploit our coarse-graining model so that, within the mean-field region, the age-distribution is in equilibrium and we know its explicit form. This allows us to couple both domains consistently, as upon transference of cells from the mean-field to the stochastic region, we sample the equilibrium age distribution. Furthermore, our method allows us to investigate the effects of intracellular noise, i.e. fluctuations of the birth rate, on collective properties such as travelling wave velocity. We show that the combination of population and birth-rate noise gives rise to large fluctuations of the birth rate in the region at the leading edge of

  17. Coarse-graining and hybrid methods for efficient simulation of stochastic multi-scale models of tumour growth

    International Nuclear Information System (INIS)

    Cruz, Roberto de la; Guerrero, Pilar; Calvo, Juan; Alarcón, Tomás

    2017-01-01

    The development of hybrid methodologies is of current interest in both multi-scale modelling and stochastic reaction–diffusion systems regarding their applications to biology. We formulate a hybrid method for stochastic multi-scale models of cells populations that extends the remit of existing hybrid methods for reaction–diffusion systems. Such method is developed for a stochastic multi-scale model of tumour growth, i.e. population-dynamical models which account for the effects of intrinsic noise affecting both the number of cells and the intracellular dynamics. In order to formulate this method, we develop a coarse-grained approximation for both the full stochastic model and its mean-field limit. Such approximation involves averaging out the age-structure (which accounts for the multi-scale nature of the model) by assuming that the age distribution of the population settles onto equilibrium very fast. We then couple the coarse-grained mean-field model to the full stochastic multi-scale model. By doing so, within the mean-field region, we are neglecting noise in both cell numbers (population) and their birth rates (structure). This implies that, in addition to the issues that arise in stochastic-reaction diffusion systems, we need to account for the age-structure of the population when attempting to couple both descriptions. We exploit our coarse-graining model so that, within the mean-field region, the age-distribution is in equilibrium and we know its explicit form. This allows us to couple both domains consistently, as upon transference of cells from the mean-field to the stochastic region, we sample the equilibrium age distribution. Furthermore, our method allows us to investigate the effects of intracellular noise, i.e. fluctuations of the birth rate, on collective properties such as travelling wave velocity. We show that the combination of population and birth-rate noise gives rise to large fluctuations of the birth rate in the region at the leading edge

  18. The effect of coarse second-phase particles on the rate of grain refinement during severe deformation processing

    DEFF Research Database (Denmark)

    Apps, P.J.; Bowen, Jacob R.; Prangnell, P.B.

    2003-01-01

    The effect of second-phase particles on the rate of grain refinement during severe deformation processing has been investigated, by comparing the microstructure evolution in an AA8079 aluminium alloy, containing 2.5 vol.% of ~2 μm particles, with that in a high purity, single-phase, Al-0.13% Mg a...... by an effective strain of only five in the particle-containing alloy, compared to ten in the single-phase material. The mechanisms that contribute to this acceleration of the grain refinement process are discussed.......The effect of second-phase particles on the rate of grain refinement during severe deformation processing has been investigated, by comparing the microstructure evolution in an AA8079 aluminium alloy, containing 2.5 vol.% of ~2 μm particles, with that in a high purity, single-phase, Al-0.13% Mg...... alloy, deformed identically by ECAE to an effective strain of ten. The materials were analysed by high-resolution EBSD orientation mapping, which revealed that grain refinement occurred at a dramatically higher rate in the particle-containing alloy. A submicron grain structure could be achieved...

  19. Grain growth behavior of Cr dispersed UO{sub 2} pellets according to change of oxygen potential during the isothermal sintering

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jang Soo; Yang, Jae Ho; Kim, Dong Joo; Kim, Jong Hun; Nam, Ik Hui; Rhee, Young Woo; Kim, Keon Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    Recent development of advanced UO{sub 2} pellet materials for commercial reactors is mainly focused on the large grain pellet which can deform easily at an elevated temperature. Cr{sub 2}O{sub 3}-doped UO{sub 2} pellet is one of the promising candidates. To increase the grain size effectively, it is important to control the additive content and sintering atmosphere. Relevant research on the Cr{sub 2}O{sub 3} doped UO{sub 2} system revealed that the doped Cr{sub 2}O{sub 3} formed a liquid phase under optimized oxygen potential, and those liquid phases promoted the grain growth. Recent work also showed that step-wise variation of sintering atmosphere during the isothermal annealing step significantly increased the grain size of Cr{sub 2}O{sub 3} doped UO{sub 2} pellet. In this paper, we investigated effect of oxygen potential change at the beginning of isothermal sintering stage on the grain growth in metallic Cr dispersed UO{sub 2} pellets. The study on the milling effect of powder mixture on the grain growth is also a part of this work.

  20. An evaluation on fatigue crack growth in a fine-grained isotropic graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wang Hongtao; Sun Libin [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Li Chenfeng [College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Shi Li [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Wang Haitao, E-mail: wanght@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer The propagation of micro- and macro-fatigue cracks in IG-11 graphite was studied. Black-Right-Pointing-Pointer The curves of the fatigue crack growth rate versus the SIF range show three stages. Black-Right-Pointing-Pointer The fatigue microcrack propagation is very sensitive to graphite's microstructures. Black-Right-Pointing-Pointer Graphite's microstructures have no significant impact on fatigue macrocrack growth. Black-Right-Pointing-Pointer The fatigue fracture surface indicates the fracture mechanism of the IG-11 graphite. - Abstract: The aim of this paper is to investigate the mechanism of fatigue crack propagation in IG-11 graphite, and determine the crack growth rate in relation to the stress level. Experimental studies were performed at both micro and macro scales. For fatigue microcrack propagation, single-edge-notch specimens were chosen for testing and the fatigue crack growth was measured in situ with a scanning electron microscope. For fatigue macrocrack propagation, CT specimens were used and the fatigue crack growth was measured with a high-accuracy optic microscope. Combining the two groups of experimental results, the following conclusions are derived: (1) The heterogeneous microstructures of the graphite material have significant impact on the fatigue microcrack growth, while their influence on fatigue macrocrack growth is very limited. (2) The relationship between the fatigue crack growth rate and the crack-tip stress intensity factor range can be expressed in the form of Paris formulae, which contains three stages: an initial rising part with a small slope, an abrupt rise with a very large acceleration, and a short final part with a small slope. (3) The fatigue fracture surface of the graphite material contains considerable sliding of leaf-shape graphite flakes combined with small cotton-shape plastic deformations. These sliding traces are approximately aligned at 45 Degree-Sign , showing the

  1. An evaluation on fatigue crack growth in a fine-grained isotropic graphite

    International Nuclear Information System (INIS)

    Wang Hongtao; Sun Libin; Li Chenfeng; Shi Li; Wang Haitao

    2012-01-01

    Highlights: ► The propagation of micro- and macro-fatigue cracks in IG-11 graphite was studied. ► The curves of the fatigue crack growth rate versus the SIF range show three stages. ► The fatigue microcrack propagation is very sensitive to graphite's microstructures. ► Graphite's microstructures have no significant impact on fatigue macrocrack growth. ► The fatigue fracture surface indicates the fracture mechanism of the IG-11 graphite. - Abstract: The aim of this paper is to investigate the mechanism of fatigue crack propagation in IG-11 graphite, and determine the crack growth rate in relation to the stress level. Experimental studies were performed at both micro and macro scales. For fatigue microcrack propagation, single-edge-notch specimens were chosen for testing and the fatigue crack growth was measured in situ with a scanning electron microscope. For fatigue macrocrack propagation, CT specimens were used and the fatigue crack growth was measured with a high-accuracy optic microscope. Combining the two groups of experimental results, the following conclusions are derived: (1) The heterogeneous microstructures of the graphite material have significant impact on the fatigue microcrack growth, while their influence on fatigue macrocrack growth is very limited. (2) The relationship between the fatigue crack growth rate and the crack-tip stress intensity factor range can be expressed in the form of Paris formulae, which contains three stages: an initial rising part with a small slope, an abrupt rise with a very large acceleration, and a short final part with a small slope. (3) The fatigue fracture surface of the graphite material contains considerable sliding of leaf-shape graphite flakes combined with small cotton-shape plastic deformations. These sliding traces are approximately aligned at 45°, showing the main cause of the fatigue fracture is the shear stress. There are also a large amount of secondary cracks inside unit cells and on cell walls

  2. Responses of Rapid Viscoanalyzer Profile and Other Rice Grain Qualities to Exogenously Applied Plant Growth Regulators under High Day and High Night Temperatures.

    Directory of Open Access Journals (Sweden)

    Shah Fahad

    Full Text Available High-temperature stress degrades the grain quality of rice; nevertheless, the exogenous application of plant growth regulators (PGRs might alleviate the negative effects of high temperatures. In the present study, we investigated the responses of rice grain quality to exogenously applied PGRs under high day temperatures (HDT and high night temperatures (HNT under controlled conditions. Four different combinations of ascorbic acid (Vc, alpha-tocopherol (Ve, brassinosteroids (Br, methyl jasmonates (MeJA and triazoles (Tr were exogenously applied to two rice cultivars (IR-64 and Huanghuazhan prior to the high-temperature treatment. A Nothing applied Control (NAC was included for comparison. The results demonstrated that high-temperature stress was detrimental for grain appearance and milling qualities and that both HDT and HNT reduced the grain length, grain width, grain area, head rice percentage and milled rice percentage but increased the chalkiness percentage and percent area of endosperm chalkiness in both cultivars compared with ambient temperature (AT. Significantly higher grain breakdown, set back, consistence viscosity and gelatinization temperature, and significantly lower peak, trough and final viscosities were observed under high-temperature stress compared with AT. Thus, HNT was more devastating for grain quality than HDT. The exogenous application of PGRs ameliorated the adverse effects of high temperature in both rice cultivars, and Vc+Ve+MejA+Br was the best combination for both cultivars under high temperature stress.

  3. Fabrication and electrical properties of textured strontium(0.53)barium(0.47)niobium(2)oxygen(6) ceramics prepared by templated grain growth

    Science.gov (United States)

    Duran, Cihangir

    Sr0.53Ba0.47Nb2O6 (SBN53) ceramics were textured by the templated grain growth (TGG), in a matrix of SrNb2O6 and BaNb2O6 powders. Acicular KSr2Nb5O15 (KSN) template particles, synthesized by a molten salt process, were used to texture the samples in the c direction (i.e., [001]). Template growth was assisted by adding V2O5 as a liquid phase former for some compositions. The texture fraction also increased with higher sintering temperatures or times and with initial template concentration due to the preferential growth of the template particles. When V2O5 was present, SBN53 phase formation initiated on the KSN templates and texture development started at temperatures as low as 950°C. Phase formation in the V2O5-free samples, however, initiated in the matrix (i.e., independent of the KSN templates). The liquid phase adversely affected the template growth by favoring anisotropic grain growth in the matrix, which caused lower texture fraction and broader texture distribution in [001] at low template concentrations. Increased template-template interaction (e.g., tangling) during tape casting also resulted in broader texture distribution. Therefore, an optimum template content was found to be ˜10--15 wt%. However, a texture fraction of 0.93 to 0.98 was obtained using only 5 wt% templates when anisotropic matrix grain growth was prevented. Phase evolution was studied in the randomly oriented samples as a function of quenching temperature, heating rate, and liquid phase, using KSN powder (rather than acicular particles) as a seed material. The formation temperature for SBN53 was lowered substantially by adding more seeds, decreasing the heating rate, and introducing a liquid. The temperature decreased from 1260°C for the samples with no seeds to 1130°C for the samples with 15.4 wt% seeds + 0.8 mol% V2O5 at a heating rate of 4°C/min. For the V2O5-free samples, the activation energy was considerably lowered from 554 +/- 15 kJ/mol for the samples with no seeds to 241

  4. Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

    Energy Technology Data Exchange (ETDEWEB)

    Fattah-alhosseini, A. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Imantalab, O., E-mail: o.imantalab@gmail.com [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Mazaheri, Y. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Keshavarz, M.K. [Department of Engineering Physics, Polytechnique Montreal, Montreal (Canada)

    2016-01-05

    In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200 nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360 MPa and 396 MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

  5. Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

    International Nuclear Information System (INIS)

    Fattah-alhosseini, A.; Imantalab, O.; Mazaheri, Y.; Keshavarz, M.K.

    2016-01-01

    In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200 nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360 MPa and 396 MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

  6. Surfactant-assisted growth of anodic nanoporous niobium oxide with a grained surface

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jeong Eun [Department of Chemical Engineering, Inha University, 253 Yonghyun Dong, Nam-Gu, Incheon 402-751 (Korea, Republic of); Choi, Jinsub, E-mail: jinsub@inha.ac.k [Department of Chemical Engineering, Inha University, 253 Yonghyun Dong, Nam-Gu, Incheon 402-751 (Korea, Republic of)

    2010-07-15

    Nanoporous niobium oxide film with a maximum thickness of 520 nm was prepared by anodizing niobium in a mixture of 1 wt% HF, 1 M H{sub 3}PO{sub 4}, and a small amount of Sodium Dodecyl Sulfate (SDS) surfactant. The porosity of the anodic niobium oxide prepared without SDS is irregular with the surface of the oxide suggesting a grained surface pattern rather than an ordered porous structure. A proper amount of SDS addition can prepare a pore arrangement with stripe patterns. The pore depth and surface pattern were strongly affected by the concentration of SDS and bath temperature. We found that the addition of SDS surfactant facilitated improvement in the chemical resistance of niobium oxide, leading to the formation of pores with a longer length compared to those prepared without a SDS surfactant. This can be in part ascribed to the protection of the surface by the physical adsorption of SDS on the surface due to a charge-charge interaction and be in part attributed to the formation of Nb=O bonding on the outermost oxide layer by SDS. When anodization was carried out for 4 h, the surface dissolution of niobium oxide was observed, which means that the maximum tolerance time against chemical dissolution was less than 4 h.

  7. Co-extrusion of food grains-banana pulp for nutritious snacks: optimization of process variables.

    Science.gov (United States)

    Mridula, D; Sethi, Swati; Tushir, Surya; Bhadwal, Sheetal; Gupta, R K; Nanda, S K

    2017-08-01

    Present study was undertaken to optimize the process conditions for development of food grains (maize, defatted soy flour, sesame seed)-banana based nutritious expanded snacks using extrusion processing. Experiments were designed using Box-Behnken design with banana pulp (8-24 g), screw speed (300-350 rpm) and feed moisture (14-16% w.b.). Seven responses viz. expansion ratio (ER), bulk density (BD), water absorption index (WAI), protein, minerals, iron and sensory acceptability were considered for optimizing independent parameters. ER, BD, WAI, protein content, total minerals, iron content, and overall acceptability ranged 2.69-3.36, 153.43-238.83 kg/m 3 , 4.56-4.88 g/g, 15.19-15.52%, 2.06-2.27%, 4.39-4.67 mg/100 g (w.b.) and 6.76-7.36, respectively. ER was significantly affected by all three process variables while BD was influenced by banana pulp and screw speed only. Studied process variables did not affected colour quality except 'a' value with banana pulp and screw speed. Banana pulp had positive correlation with water solubility index, total minerals and iron content and negative with WAI, protein and overall acceptability. Based upon multiple response analysis, optimized conditions were 8 g banana pulp, 350 rpm screw speed and 14% feed moisture indicating the protein, calorie, iron content and overall sensory acceptability in sample as 15.46%, 401 kcal/100 g, 4.48 mg/100 g and 7.6 respectively.

  8. INTRODUCTION TO THE ANALYSIS OF THE MECHANICS OF THE DIAMOND GRINDING PROCESS WITH THE ACCOUNT OF WEAR OF WHEEL GRAINS

    Directory of Open Access Journals (Sweden)

    Feodor NOVIKOV

    2017-12-01

    Full Text Available The work is devoted to the theoretical analysis of the mechanics of the diamond grinding process, taking into account the wear of the wheel grains for scientifically based choice of optimal processing conditions. A multiplicative probabilistic approach to the generalization of the cutting profile of a diamond grinding wheel in its consideration in a state of some steady wear during processing is considered. This is achieved by working the wheel in a mode of properly established self-sharpening or with the use of effective dressing methods. In this case, the linear wear of individual grains of diamond abrasive located on the working surface of the grinding wheel and opened to mechanical contact with the material being processed is assumed to proportionally to the depth of the introduction of grain into it. The analytical dependence of the maximum thickness of the cut is presented, and the relationship between the maximum grain wear and the accepted universal relative characteristic of the steady wear with the operational parameters of the tool and the grinding mode is shown. The obtained results can be used in the development of analytical models of processing productivity and microgeometric engineering of the treated surface, new approaches to increasing the efficiency of diamond grinding. The research is based on modern technical possibilities of controlling the state of the cutting relief of diamond-abrasive tools, especially in electro-physical-mechanical grinding technologies, for example, using the diamond-spark method developed at the Kharkov Polytechnic Institute.

  9. Surface morphology study on chromium oxide growth on Cr films by Nd-YAG laser oxidation process

    International Nuclear Information System (INIS)

    Dong Qizhi; Hu Jiandong; Guo Zuoxing; Lian Jianshe; Chen Jiwei; Chen Bo

    2002-01-01

    Grain sized (60-100 nm) Cr 2 O 3 thin films were prepared on Cr thin film surfaces by Nd-YAG laser photothermal oxidation process. Surface morphology study showed crack-free short plateau-like oxide films formed. Increase of dislocation density after pulsed laser irradiation was found. Thin film external surfaces, grain boundaries and dislocations are main paths of laser surface oxidation. Pinning and sealing of grain boundary was the reason that deeper oxidation did not produce. Grain growth and agglomeration of Cr sub-layer yielded tensile stress on the surface Cr 2 O 3 thin film. It was the reason that short plateau-like surface morphology formed and cracks appeared sometimes. In oxygen annealing at 700 deg. C, grain boundaries were considered not to be pinned at the surface, mixture diffusion was main mechanism in growth of oxide. Compression stress development in whole film led to extrusion of grains that was the reason that multiple appearances such as pyramid-like and nutshell-like morphology formed

  10. The formation of PSB-like shear bands in cyclically deformed ultrafine grained copper processed by ECAP

    Energy Technology Data Exchange (ETDEWEB)

    Wu, S.D.; Wang, Z.G.; Jiang, C.B.; Li, G.Y.; Alexandrov, I.V.; Valiev, R.Z

    2003-06-15

    Cyclic deformation was performed on ultrafine grained copper processed by ECAP. Shear bands (SBs) and adjacent microstructures were investigated using electron channeling contrast in scanning electron microscope. The possible formation mechanism of SB was discussed based on the characteristic distribution of defects introduced by ECAP.

  11. Modeling of the inhomogeneity of grain refinement during combined metal forming process by finite element and cellular automata methods

    Energy Technology Data Exchange (ETDEWEB)

    Majta, Janusz; Madej, Łukasz; Svyetlichnyy, Dmytro S.; Perzyński, Konrad; Kwiecień, Marcin, E-mail: mkwiecie@agh.edu.pl; Muszka, Krzysztof

    2016-08-01

    The potential of discrete cellular automata technique to predict the grain refinement in wires produced using combined metal forming process is presented and discussed within the paper. The developed combined metal forming process can be treated as one of the Severe Plastic Deformation (SPD) techniques that consists of three different modes of deformation: asymmetric drawing with bending, namely accumulated angular drawing (AAD), wire drawing (WD) and wire flattening (WF). To accurately replicate complex stress state both at macro and micro scales during subsequent deformations two stage modeling approach was used. First, the Finite Element Method (FEM), implemented in commercial ABAQUS software, was applied to simulate entire combined forming process at the macro scale level. Then, based on FEM results, the Cellular Automata (CA) method was applied for simulation of grain refinement at the microstructure level. Data transferred between FEM and CA methods included set of files with strain tensor components obtained from selected integration points in the macro scale model. As a result of CA simulation, detailed information on microstructure evolution during severe plastic deformation conditions was obtained, namely: changes of shape and sizes of modeled representative volume with imposed microstructure, changes of the number of grains, subgrains and dislocation cells, development of grain boundaries angle distribution as well as changes in the pole figures. To evaluate CA model predictive capabilities, results of computer simulation were compared with scanning electron microscopy and electron back scattered diffraction images (SEM/EBSD) studies of samples after AAD+WD+WF process.

  12. p-process xenon isotope anomalies in stardust grains from meteorites

    International Nuclear Information System (INIS)

    Ott, U.

    2013-01-01

    Full text: In measurements on 'bulk' samples of meteorites isotopic variations due to the p-process usually have taken a backseat compared to such in s- or r-isotopes, and, in the best case, can be qualitatively attributed to the p-process, with little to no inferences concerning detailed isotopic yields. The situation is different for grains of stardust that survived in primitive meteorites. In fact, isotopically strange xenon was the key feature that led to the first identification of a stardust mineral, nanodiamonds containing xenon with overabundances of up to a factor of ∼2 in both the r-only (≡H-Xe) and p-only (≡L-Xe) isotopes. Relative excesses of the two r-only isotopes ( 134 Xe, 136 Xe) as well as of the two p-only isotopes ( 124 Xe, 126 Xe) are not equal, hence the processes responsible for HL-xenon must differ from the 'average' r- and p-processes as reflected in solar system abundances. However, while considerable effort has been put into explaining H-Xe, there has been little work on the p-side (L-Xe). Relying on scarce nuclear data, Heymann and Dziczkaniec have studied photodisintegration reactions of Xe and Ba seeds in intermediate zones of supernovae and found that the relative production of the p-Xe isotopes depends sensitively on the yield of the (γ, α) reaction on 128 Ba. Another suggestion - applicable to both the r- and p-anomalies in diamond xenon - is that of a 'rapid separation' between stable Xe isotopes and radioactive precursors produced in the 'standard' p- (as well as r-) process. For the p-isotopes to work, this would require the bulk (87%) of 126 Xe to be produced via the 126 Ba precursor, with a half live of ∼100 minutes, in order to explain the high 124 Xe/ 126 Xe. In contrast to diamond xenon, xenon in silicon carbide contains - besides the component from the s-process in their parent AGB stars - 'almost normal' Xe, with indications for 124 Xe/ 126 Xe being few (∼8)% lower than in solar Xe.

  13. Effect of Irrigation Timing on Root Zone Soil Temperature, Root Growth and Grain Yield and Chemical Composition in Corn

    Directory of Open Access Journals (Sweden)

    Xuejun Dong

    2016-05-01

    Full Text Available High air temperatures during the crop growing season can reduce harvestable yields in major agronomic crops worldwide. Repeated and prolonged high night air temperature stress may compromise plant growth and yield. Crop varieties with improved heat tolerance traits as well as crop management strategies at the farm scale are thus needed for climate change mitigation. Crop yield is especially sensitive to night-time warming trends. Current studies are mostly directed to the elevated night-time air temperature and its impact on crop growth and yield, but less attention is given to the understanding of night-time soil temperature management. Delivering irrigation water through drip early evening may reduce soil temperature and thus improve plant growth. In addition, corn growers typically use high-stature varieties that inevitably incur excessive respiratory carbon loss from roots and transpiration water loss under high night temperature conditions. The main objective of this study was to see if root-zone soil temperature can be reduced through drip irrigation applied at night-time, vs. daytime, using three corn hybrids of different above-ground architecture in Uvalde, TX where day and night temperatures during corn growing season are above U.S. averages. The experiment was conducted in 2014. Our results suggested that delivering well-water at night-time through drip irrigation reduced root-zone soil temperature by 0.6 °C, increase root length five folds, plant height 2%, and marginally increased grain yield by 10%. However, irrigation timing did not significantly affect leaf chlorophyll level and kernel crude protein, phosphorous, fat and starch concentrations. Different from our hypothesis, the shorter, more compact corn hybrid did not exhibit a higher yield and growth as compared with taller hybrids. As adjusting irrigation timing would not incur an extra cost for farmers, the finding reported here had immediate practical implications for farm

  14. Direct growth of large grain polycrystalline silicon films on aluminum-induced crystallization seed layer using hot-wire chemical vapor deposition

    International Nuclear Information System (INIS)

    Wu, Bing-Rui; Lo, Shih-Yung; Wuu, Dong-Sing; Ou, Sin-Liang; Mao, Hsin-Yuan; Wang, Jui-Hao; Horng, Ray-Hua

    2012-01-01

    Large grain polycrystalline silicon (poly-Si) films on glass substrates have been deposited on an aluminum-induced crystallization (AIC) seed layer using hot-wire chemical vapor deposition (HWCVD). A poly-Si seed layer was first formed by the AIC process and a thicker poly-Si film was subsequently deposited upon the seed layer using HWCVD. The effects of AIC annealing parameters on the structural and electrical properties of the poly-Si seed layers were characterized by Raman scattering spectroscopy, field-emission scanning electron microscopy, and Hall measurements. It was found that the crystallinity of seed layer was enhanced with increasing the annealing duration and temperature. The poly-Si seed layer formed at optimum annealing parameters can reach a grain size of 700 nm, hole concentration of 3.5 × 10 18 cm −3 , and Hall mobility of 22 cm 2 /Vs. After forming the seed layer, poly-Si films with good crystalline quality and high growth rate (> 1 nm/s) can be obtained using HWCVD. These results indicated that the HWCVD-deposited poly-Si film on an AIC seed layer could be a promising candidate for thin-film Si photovoltaic applications. - Highlights: ►Poly-Si seed layers are formed by aluminum-induced crystallization (AIC) process. ►Poly-Si on AIC seed layers are prepared by hot-wire chemical vapor deposition. ►AIC process parameters affect structural properties of poly-Si films. ►Increasing the annealing duration and temperature increases the film crystallinity.

  15. Processing, microstructure, and mechanical properties of large-grained zirconium diboride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Neuman, Eric W.; Hilmas, Gregory E., E-mail: ghilmas@mst.edu; Fahrenholtz, William G.

    2016-07-18

    Zirconium diboride ceramics produced using commercial ZrB{sub 2} powders, and milled with zirconium diboride grinding media, were fabricated by hot-pressing at temperatures of 2100–2200 °C with hold times of 30–120 min. This ZrB{sub 2} exhibits no additional impurities typically introduced by milling with grinding media of differing composition. Microstructure analysis revealed grain sizes ranging from ~25 to ~50 µm along with ~3 vol% porosity. Flexure strength ranged from 335 to 400 MPa, elastic modulus from 490 to 510 GPa, fracture toughness from 2.7 to 3.2 MPa m{sup ½}, and hardness from 13.0 to 14.4 GPa. Strength limiting flaws were identified as surface grain pullout induced by machining. Elastic modulus and hardness were found to increase with decreasing porosity. Compared to the fine grained ceramics typically reported, large grain zirconium diboride ceramics exhibit higher than expected room temperature strengths.

  16. Room temperature deformation mechanisms in ultrafine-grained materials processed by hot isostatic pressing

    International Nuclear Information System (INIS)

    Cao, W.Q.; Dirras, G.F.; Benyoucef, M.; Bacroix, B.

    2007-01-01

    Ultrafine-grained (uf-g) and microcrystalline-grained (mc-g) irons have been fabricated by hot isostatic pressing of nanopowders. The mechanical properties have been characterized by compressive tests at room temperature and the resulting microstructures and textures have been determined by combining electron back scatter diffraction and transmission electron microscopy. A transition of the deformation mode, from work hardening to work softening occurs for grain sizes below ∼1 μm, reflecting a transition of the deformation mode from homogeneous to localized deformation into shear bands (SBs). The homogeneous deformation is found to be lattice dislocation-based while the deformation within SBs involves lattice dislocations as well as boundary-related mechanisms, possibly grain boundary sliding accommodated by boundary opening

  17. Sodium induced grain growth, defect passivation and enhancement in the photovoltaic properties of Cu{sub 2}ZnSnS{sub 4} thin film solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Om Pal; Gour, Kuldeep Singh [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Parmar, Rahul [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Singh, Vidya Nand, E-mail: singhvn@nplindia.org [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)

    2016-07-01

    Sodium diffusion from soda lime glass (SLG) during high temperature annealing is known to play a crucial role in affecting the grain growth and defect passivation in chalocogenide/kesterite solar cells. Additional sodium is required when low temperature or short term annealing is used. Although this fact is known, a systematic comparative study for kesterite films is seldom reported. In the present study, Cu{sub 2}ZnSnS{sub 4} thin films were deposited on SLG and Mo coated SLG using stacked layer reactive sputtering. Na was deposited over the CZTS thin film and the film was annealed in N{sub 2} atmosphere in order to enhance the grain growth. This resulted in the shift in the XRD peak towards lower diffraction angle. The optical bandgap shifted from 1.45 eV to 1.38 eV with Na addition. Significant grain growth from hundreds of nanometer to micrometer was observed in samples with Na. Device fabricated in SLG/Mo/CZTS/CdS/ZnO/ITO configuration with Al front contact shows increase in efficiencies values from 1.50% to 2.84%. - Highlights: • Reactive sputtering with reduced annealing time have been used for the growth of CZTS thin film. • NaF has been deposited over precursor film before annealing. • Na addition resulted in grain growth, improved compactness and reduction in band gap. • An enhancement in the photovoltaic characteristics have been observed with addition of Na.

  18. Polymer-Coated Urea Delays Growth and Accumulation of Key Nutrients in Aerobic Rice but Does Not Affect Grain Mineral Concentrations

    Directory of Open Access Journals (Sweden)

    Terry J. Rose

    2016-01-01

    Full Text Available Enhanced efficiency nitrogen (N fertilizers (EEFs may improve crop recovery of fertilizer-N, but there is evidence that some EEFs cause a lag in crop growth compared to growth with standard urea. Biomass and mineral nutrient accumulation was investigated in rice fertilized with urea, urea-3,4-dimethylpyrazole phosphate (DMPP and polymer-coated urea (PCU to determine whether any delays in biomass production alter the accumulation patterns, and subsequent grain concentrations, of key mineral nutrients. Plant growth and mineral accumulation and partitioning to grains did not differ significantly between plants fertilized with urea or urea-DMPP. In contrast, biomass accumulation and the accumulation of phosphorus, potassium, calcium, magnesium, copper, zinc and manganese were delayed during the early growth phase of plants fertilized with PCU. However, plants in the PCU treatment ultimately compensated for this by increasing growth and nutrient uptake during the latter vegetative stages so that no differences in biomass or nutrient accumulation generally existed among N fertilizer treatments at anthesis. Delayed biomass accumulation in rice fertilized with PCU does not appear to reduce the total accumulation of mineral nutrients, nor to have any impact on grain mineral nutrition when biomass and grain yields are equal to those of rice grown with urea or urea-DMPP.

  19. Arabidopsis Growth Simulation Using Image Processing Technology

    Directory of Open Access Journals (Sweden)

    Junmei Zhang

    2014-01-01

    Full Text Available This paper aims to provide a method to represent the virtual Arabidopsis plant at each growth stage. It includes simulating the shape and providing growth parameters. The shape is described with elliptic Fourier descriptors. First, the plant is segmented from the background with the chromatic coordinates. With the segmentation result, the outer boundary series are obtained by using boundary tracking algorithm. The elliptic Fourier analysis is then carried out to extract the coefficients of the contour. The coefficients require less storage than the original contour points and can be used to simulate the shape of the plant. The growth parameters include total area and the number of leaves of the plant. The total area is obtained with the number of the plant pixels and the image calibration result. The number of leaves is derived by detecting the apex of each leaf. It is achieved by using wavelet transform to identify the local maximum of the distance signal between the contour points and the region centroid. Experiment result shows that this method can record the growth stage of Arabidopsis plant with fewer data and provide a visual platform for plant growth research.

  20. Authentication of bee pollen grains in bright-field microscopy by combining one-class classification techniques and image processing.

    Science.gov (United States)

    Chica, Manuel

    2012-11-01

    A novel method for authenticating pollen grains in bright-field microscopic images is presented in this work. The usage of this new method is clear in many application fields such as bee-keeping sector, where laboratory experts need to identify fraudulent bee pollen samples against local known pollen types. Our system is based on image processing and one-class classification to reject unknown pollen grain objects. The latter classification technique allows us to tackle the major difficulty of the problem, the existence of many possible fraudulent pollen types, and the impossibility of modeling all of them. Different one-class classification paradigms are compared to study the most suitable technique for solving the problem. In addition, feature selection algorithms are applied to reduce the complexity and increase the accuracy of the models. For each local pollen type, a one-class classifier is trained and aggregated into a multiclassifier model. This multiclassification scheme combines the output of all the one-class classifiers in a unique final response. The proposed method is validated by authenticating pollen grains belonging to different Spanish bee pollen types. The overall accuracy of the system on classifying fraudulent microscopic pollen grain objects is 92.3%. The system is able to rapidly reject pollen grains, which belong to nonlocal pollen types, reducing the laboratory work and effort. The number of possible applications of this authentication method in the microscopy research field is unlimited. Copyright © 2012 Wiley Periodicals, Inc.

  1. Electrical characterization of CdTe grain-boundary properties from as processed CdTe/CdS solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Woods, L.M.; Robinson, G.Y. [Colorado State Univ., Fort Collins, CO (United States); Levi, D.H.; Ahrenkiel, R.K. [National Renewable Energy Lab., Golden, CO (United States); Kaydanov, V. [Colorado School of Mines, Golden, CO (United States)

    1998-09-01

    An ability to liftoff or separate the thin-film polycrystalline CdTe from the CdS, without the use of chemical etches, has enabled direct electrical characterization of the as-processed CdTe near the CdTe/CdS heterointerface. The authors use this ability to understand how a back-contact, nitric-phosphoric (NP) etch affects the grain boundaries throughout the film. Quantitative determination of the grain-boundary barrier potentials and estimates of doping density near the grain perimeter are determined from theoretical fits to measurements of the current vs. temperature. Estimates of the bulk doping are determined from high-frequency resistivity measurements. The light and dark barrier potentials change after the NP etch, and the origin of this change is postulated. Also, a variable doping density within the grains of non-etched material has been determined. These results allow a semi-quantitative grain-boundary band diagram to be drawn that should aid in determining more accurate two-dimensional models for polycrystalline CdTe solar cells.

  2. Investigation on the asymmetry of thermal condition and grain defect formation in the customary directional solidification process

    International Nuclear Information System (INIS)

    Ma, D; Wu, Q; Hollad, S; Bührig-Polaczek, A

    2012-01-01

    In the present study, the non-uniformity of the thermal condition and the corresponding grain defect formation in the customary Bridgman process were investigated. The casting clusters in radial alignment were directionally solidified in a Bridgman furnace. It was found that in the casting cluster, the shadow side facing the central rod was ineffectively heated in the hot zone and ineffectively cooled in the cooling zone during withdrawal, compared with the heater side facing the furnace heater. The metallographic examination of the simplified turbine blades exhibited that the platforms on the shadow side are very prone to stray grain formation, while the heater side reveals a markedly lower tendency for that. The asymmetric thermal condition causes the asymmetrical formation of these grain defects. This non-uniformity of the thermal condition should be minimized as far as possible, in order to effectively optimize the quality of the SC superalloy components.

  3. Nutritional, functional and rheological properties of processed sorghum and ragi grains

    Directory of Open Access Journals (Sweden)

    Himadri Mahajan

    2015-12-01

    Full Text Available This study was undertaken to determine the effect of different treatments such as roasting, puffing and germination of white sorghum, red sorghum and ragi grains on physicochemical, antioxidant, protein, amylose, bulk density, colour index and rheological properties of respective flour. In case of ragi, after roasting treatment, total phenolic content (TPC content for flour was increased from 0.331 ± 0.001 to 0.373 ± 0.004 mg of gallic acid equivalents per gram of dry sample. However, total flavonoids content was also increased slightly after different processing treatments. The rheological properties of respective flour were studied using Chopin Mixolab, where wheat flour dough profile acts as a reference to study the effect of different treatments. Dough elasticity which is expressed by the values of amplitude (Nm was found to be low in case of untreated flour as compared to wheat flour dough. Elasticity values of untreated flour such as white sorghum, red sorghum and ragi were 0.02, 0.00 and 0.06 Nm, respectively. Whereas, after processing treatments, values of elasticity for roasted flour dough of white sorghum, puffed flour dough of red sorghum and roasted flour dough of ragi increased to 0.36, 0.11 and 0.15 Nm, respectively, as compared to wheat flour dough of 0.10 Nm. The results found that roasted ragi flour had higher rate of starch gelatinization, lower starch retrogradation, high antioxidant and amylose contents which were found to be prospective ingredients in whole wheat flour in various baked and fermented food applications.

  4. Comment on "Mitigating grain growth in binary nanocrystalline alloys through solute selection based on thermodynamic stability maps"

    Czech Academy of Sciences Publication Activity Database

    Lejček, Pavel; Hofmann, S.

    2015-01-01

    Roč. 107, Sep (2015), s. 235-237 ISSN 0927-0256 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : nanocrystalline materials * grain size * grain boundary energy * grain boundary segregation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.086, year: 2015

  5. Friction stir processing: a new grain refinement technique to achieve high strain rate superplasticity in commercial alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, R.S. [Missouri Univ., Rolla, MO (United States). Dept. of Metallurgical Engineering; Mahoney, M.W. [Rockwell International Corp., Thousand Oaks, CA (United States). Science Center

    2001-07-01

    Friction stir processing is a new thermo-mechanical processing technique that leads to a microstructure amenable for high strain rate superplasticity in commercial aluminum alloys. Friction stirring produces a combination of very fine grain size and high grain boundary misorientation angles. Preliminary results on a 7075 Al demonstrate high strain rate superplasticity in the temperature range of 430-510 C. For example, an elongation of >1000% was observed at 490 C and 1 x 10{sup -2} s{sup -1}. This demonstrates a new possibility to economically obtain a superplastic microstructure in commercial aluminum alloys. Based on these results, a three-step manufacturing process to fabricate complex shaped components can be envisaged: cast sheet or hot-pressed powder metallurgy sheet + friction stir processing + superplastic forging or forming. (orig.)

  6. ON THE ISSUE OF IMPORT SUBSTITUTION OF DEEP PROCESSING PRODUCTS FROM GRAIN AND POTATO

    Directory of Open Access Journals (Sweden)

    N. R. Andreev

    2014-01-01

    Full Text Available Summary. The analysis of structure of starch containing raw materials processing in Russia Federation is provided in the article. There was noted an increase in volumes of corn and wheat processing, however the share of processed potato is still low (below 4%. It was established that Russian starch products and starch sweeteners are on the same level on quality as best European samples and they are very competitive. Market demand in crystalline glucose for food and medical purposes (over 30 thous. tons is fully covered by import. The volume of import of modified starches exceeds 80 % of total consumption. The biggest volume of import among native starches belongs to potato starch – over 60 %. The article provides suggestions on import substitution of mentioned starch products. The growth of starch production in Russia was accompanied by concentration of production at large enterprises. So, in 2013 over 90 % of glucose syrup was produced at six enterprises, over 80 % of dry starch – at five enterprises. Efficiency of corn and wheat processing into starch and starch products is achieved by production and selling of co-products (dry gluten, gluten, corn germ or corn oil, corn extract, feed products.Development of starch sweeteners production from starch could be achieved by expanding the consumption areas of different kinds of glucose syrup and production of glucose-fructose syrups as full substitute of sugar, providing import substitution of sugar, crystalline glucose of food and medicine purpose, deep processing of glucose into polyols (sorbit, maltit, polylactites, aminoacids.

  7. Enhancement effects of dietary wheat distiller's dried grains with solubles on growth, immunology, and resistance to Edwardsiella ictaluri challenge of channel catfish, Ictalurus punctatus

    Science.gov (United States)

    This study evaluated the effects of the inclusion of wheat distiller’s dried grains with solubles (WDDGS) at levels of 0 (control), 10, 20, 30 and 40% without (diets 2-5) and with (diets 6-9) lysine supplementation, as substitutes of soybean meal and corn meal mixture on growth, body composition, he...

  8. Growth performance and total tract nutrient digestion for Holstein heifers limit-fed diets high in distillers grains with different forage particle sizes

    Science.gov (United States)

    This study evaluated dairy heifer growth performance and total tract nutrient digestion when fed diets high in dried distillers grains with solubles (DDGS) with different forage particle size. An 8-wk randomized complete block design study was conducted utilizing twenty-two Holstein heifers (123 ±...

  9. Decomposition of Fertilizer Use Intensity and Its Environmental Risk in China’s Grain Production Process

    Directory of Open Access Journals (Sweden)

    Jie Cai

    2018-02-01

    Full Text Available In order to fully explore the fertilizer use intensity and its potential threats to the ecological environment, this paper has studied the decomposition of fertilizer use intensity and its environmental risk in China’s grain production. Based on the statistical data collected from 10 provinces during 2004–2015 in China’s grain producing areas, this paper has analyzed the effect of fertilizer use intensity from a regional perspective. The environmental risk assessment model considers some factors such as the fertilizer application safety thresholds use efficiency, multiple cropping index, and environmental impact weight. The fertilizer application safety thresholds are calculated on the target output of local food crops. The results show that: (1 during 2004–2015, the fertilizer use intensity shows an increasing trend in China’s grain producing areas, and the intensity is significantly higher than the upper limit of the international safety fertilization; (2 the cumulative contribution rate of the increase of fertilizer use intensity caused by regional fertilizer use efficiency and grain planting structure adjustment are 57.03% and 1.81% respectively; (3 in 2015, China’s grain producing areas’ environmental risk index of phosphorus and potash was low, with the values in these two provinces being quite different and indicating the characteristics of aggregation and distribution. Therefore, the Chinese government should unswervingly encourage the application of some technology that could save fertilizer and increase efficiency, establish environmental risk monitoring and control systems, and improve relevant policies and regulations.

  10. Comminution process to produce precision wood particles of uniform size and shape with disrupted grain structure from wood chips

    Science.gov (United States)

    Dooley, James H; Lanning, David N

    2013-08-13

    A process of comminution of wood chips (C) having a grain direction to produce a mixture of wood particles (P), wherein the wood chips are characterized by an average length dimension (L.sub.C) as measured substantially parallel to the grain, an average width dimension (W.sub.C) as measured normal to L.sub.C and aligned cross grain, and an average height dimension (H.sub.C) as measured normal to W.sub.C and L.sub.C, and wherein the comminution process comprises the step of feeding the wood chips in a direction of travel substantially randomly to the grain direction through a counter rotating pair of intermeshing arrays of cutting discs (D) arrayed axially perpendicular to the direction of wood chip travel, wherein the cutting discs have a uniform thickness (T.sub.D), and wherein at least one of L.sub.C, W.sub.C, and H.sub.C is greater than T.sub.D.

  11. Growth process for gallium nitride porous nanorods

    Science.gov (United States)

    Wildeson, Isaac Harshman; Sands, Timothy David

    2015-03-24

    A GaN nanorod and formation method. Formation includes providing a substrate having a GaN film, depositing SiN.sub.x on the GaN film, etching a growth opening through the SiN.sub.x and into the GaN film, growing a GaN nanorod through the growth opening, the nanorod having a nanopore running substantially through its centerline. Focused ion beam etching can be used. The growing can be done using organometallic vapor phase epitaxy. The nanopore diameter can be controlled using the growth opening diameter or the growing step duration. The GaN nanorods can be removed from the substrate. The SiN.sub.x layer can be removed after the growing step. A SiO.sub.x template can be formed on the GaN film and the GaN can be grown to cover the SiO.sub.x template before depositing SiN.sub.x on the GaN film. The SiO.sub.x template can be removed after growing the nanorods.

  12. Coarse-grained molecular simulation of epidermal growth factor receptor protein tyrosine kinase multi-site self-phosphorylation.

    Directory of Open Access Journals (Sweden)

    John G Koland

    2014-01-01

    Full Text Available Upon the ligand-dependent dimerization of the epidermal growth factor receptor (EGFR, the intrinsic protein tyrosine kinase (PTK activity of one receptor monomer is activated, and the dimeric receptor undergoes self-phosphorylation at any of eight candidate phosphorylation sites (P-sites in either of the two C-terminal (CT domains. While the structures of the extracellular ligand binding and intracellular PTK domains are known, that of the ∼225-amino acid CT domain is not, presumably because it is disordered. Receptor phosphorylation on CT domain P-sites is critical in signaling because of the binding of specific signaling effector molecules to individual phosphorylated P-sites. To investigate how the combination of conventional substrate recognition and the unique topological factors involved in the CT domain self-phosphorylation reaction lead to selectivity in P-site phosphorylation, we performed coarse-grained molecular simulations of the P-site/catalytic site binding reactions that precede EGFR self-phosphorylation events. Our results indicate that self-phosphorylation of the dimeric EGFR, although generally believed to occur in trans, may well occur with a similar efficiency in cis, with the P-sites of both receptor monomers being phosphorylated to a similar extent. An exception was the case of the most kinase-proximal P-site-992, the catalytic site binding of which occurred exclusively in cis via an intramolecular reaction. We discovered that the in cis interaction of P-site-992 with the catalytic site was facilitated by a cleft between the N-terminal and C-terminal lobes of the PTK domain that allows the short CT domain sequence tethering P-site-992 to the PTK core to reach the catalytic site. Our work provides several new mechanistic insights into the EGFR self-phosphorylation reaction, and demonstrates the potential of coarse-grained molecular simulation approaches for investigating the complexities of self-phosphorylation in

  13. Fractal dust grains in plasma

    International Nuclear Information System (INIS)

    Huang, F.; Peng, R. D.; Liu, Y. H.; Chen, Z. Y.; Ye, M. F.; Wang, L.

    2012-01-01

    Fractal dust grains of different shapes are observed in a radially confined magnetized radio frequency plasma. The fractal dimensions of the dust structures in two-dimensional (2D) horizontal dust layers are calculated, and their evolution in the dust growth process is investigated. It is found that as the dust grains grow the fractal dimension of the dust structure decreases. In addition, the fractal dimension of the center region is larger than that of the entire region in the 2D dust layer. In the initial growth stage, the small dust particulates at a high number density in a 2D layer tend to fill space as a normal surface with fractal dimension D = 2. The mechanism of the formation of fractal dust grains is discussed.

  14. Whole-plant dynamic system of nitrogen use for vegetative growth and grain filling in rice plants (Oryza sativa L. as revealed through the production of 350 grains from a germinated seed over 150 days: a review and synthesis

    Directory of Open Access Journals (Sweden)

    Tadakatsu Yoneyama

    2016-08-01

    Full Text Available A single germinated rice (Oryza sativa L seed can produce 350 grains with the sequential development of 15 leaves on the main stem and 7 ‒ 10 leaves on 4 productive tillers (forming 5 panicles in total, using nitrogen (N taken up from the environment over a 150-day growing season. Nitrogen travels from uptake sites to the grain through growing organ-directed cycling among sequentially developed organs. Over the past 40 years, the dynamic system for N allocation during vegetative growth and grain filling has been elucidated through studies on N and 15N transport as well as enzymes and transporters involved. In this review, we synthesize the information obtained in these studies along the following main points: (1 During vegetative growth before grain-filling, about half of the total N in the growing organs, including young leaves, tillers, root tips and differentiating panicles is supplied via phloem from mature source organs such as leaves and roots, after turnover and remobilization of proteins, whereas the other half is newly taken up and supplied via xylem, with an efficient xylem-to-phloem transfer at stem nodes. Thus, the growth of new organs depends equally on both N sources. (2 A large fraction (as much as 80% of the grain N is derived largely from mature organs such as leaves and stems by degradation, including the autophagy pathway of chloroplast proteins (e.g., Rubisco. (3 Mobilized proteinogenic amino acids, including arginine, lysine, proline and valine, are derived mainly from protein degradation, with amino acid transporters playing a role in transferring these amino acids across cell membranes of source and sink organs, and enabling their efficient reutilization in the latter. On the other hand, amino acids such as glutamine, glutamic acid, γ-amino butyric acid, aspartic acid, and alanine are produced by assimilation of newly taken up N by roots and transported via xylem and phloem. The formation of 350 filled grains over 50

  15. Lessons Learned from Designing the Montium a Coarse-Grained Reconfigurable Processing Tile

    NARCIS (Netherlands)

    Smit, Gerardus Johannes Maria; Heysters, P.M.; Rosien, M.A.J.; Molenkamp, Egbert

    2004-01-01

    In this paper we describe in retrospective the main results of a four year project, called Chameleon. As part of this project we developed a coarse-grained reconfigurable core for DSP algorithms in wirelessdevices denoted MONTIUM. After presenting the main achievements within this project we present

  16. Effects of excessive grain growth on the magnetic and mechanical properties of hot-deformed NdFeB magnets

    Energy Technology Data Exchange (ETDEWEB)

    Lin, M., E-mail: linm@nimte.ac.c [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering Chinese Academy of Science, Ningbo 315201 (China); Wang, H.J. [Division of Functional Materials, Central Iron and Steel Research Institute, Beijing 100081 (China); Yi, P.P.; Yan, A.R. [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering Chinese Academy of Science, Ningbo 315201 (China)

    2010-08-15

    The magnetic and mechanical properties of rare-earth magnets hot-deformed at temperature range 750-950 deg. C have been investigated. The grains tended to grow excessively from dozens of nanometers to several microns at the temperatures above 850 deg. C. The alignment of grains was disrupted by the hot deformation at the high temperatures. The Nd-rich phase was extruded at the temperatures which are higher than 850 deg. C. The Nd-rich phase extrusion resulted in the reduction of density by 1% and the reduction of remanence from 1.42 to 0.72 T. The reduction of grain boundaries caused by flat platelet-shaped grains changing to spherical grains and the weak binding strength among large grains of Nd{sub 2}Fe{sub 14}B phase may be the main reasons for the low mechanical strength of hot-deformed magnets.

  17. Sugarcane Aphid Population Growth, Plant Injury, and Natural Enemies on Selected Grain Sorghum Hybrids in Texas and Louisiana.

    Science.gov (United States)

    Brewer, Michael J; Gordy, John W; Kerns, David L; Woolley, James B; Rooney, William L; Bowling, Robert D

    2017-10-01

    In response to the 2013 outbreak of sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), on sorghum, Sorghum bicolor (L.), in North America, experiments were conducted at three southern U.S. grain sorghum production locations (Corpus Christi, TX; Winnsboro, LA; Rosenberg, TX). The objectives were to authenticate yield decline on susceptible hybrids (2014 and 2015) and to measure aphid population growth and natural enemy prevalence on susceptible and resistant hybrids with similar genetic background (2014). Yield decline on susceptible hybrids (Tx 2752/Tx430 and DKS53-67) was more substantial when aphid population growth accelerated quickly and peaked above 300 aphids per leaf (50 to nearly 100% yield decline). Location and year variation in maximum aphid density and cumulative aphid-days was high, with doubling time values on the susceptible hybrids ranging between 3.9 and 7.9 d. On resistant Tx2752/Tx2783, leaf injury and yield decline were not seen or less severe than on its paired susceptible Tx2752/Tx430. Aphids declined on Tx2752/Tx2783 after initial colony establishment (Corpus Christi) or took about 60% longer to double in population size when compared with Tx2572/Tx430 (Winnsboro). The predominant natural enemy taxa were aphelinid mummies (Hymenoptera: Aphelinidae), ladybird beetles (Coleoptera: Coccinellidae), and sryphid flies (Diptera: Syrphidae), and they were more prevalent during flowering than prior to flowering. They were generally responsive to changes in aphid density of both susceptible and resistant hybrids, but variability points to need for further study. In future research, full season observations should continue as well as more detailed study of potential compatibility of sorghum resistance and biological control. © The Author 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  18. Effect of different types of processing on the total phenolic compound content, antioxidant capacity, and saponin content of Chenopodium quinoa Willd grains.

    Science.gov (United States)

    Nickel, Júlia; Spanier, Luciana Pio; Botelho, Fabiana Torma; Gularte, Márcia Arocha; Helbig, Elizabete

    2016-10-15

    The effects of five processing forms on the content of phenolic compounds, antioxidant capacity, and saponin content in quinoa grains were evaluated. The processes included washing, washing followed by hydration, cooking (with or without pressure), and toasting. The highest content of phenolic compounds was obtained after cooking under pressure; however, these compounds also increased with grain washing. The toasting process caused the greatest loss. The antioxidant capacity of the grains was similarly affected by the processing techniques. According to the amount of saponins, the grains were classified as bitter. Washing caused a reduction in these compounds, but the levels remained unchanged after cooking (with and without) pressure and toasting; however, they significantly increased after hydration. Cooking, especially with pressure, had greater effects than the other processes, and potentiated the functional properties of quinoa grains. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

    Energy Technology Data Exchange (ETDEWEB)

    Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; Schreiber, D. K.

    2018-02-01

    The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300-360°C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N2 gas. Results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

  20. Physical Alteration of Martian Dust Grains, Its Influence on Detection of Clays and Identification of Aqueous Processes on Mars

    Science.gov (United States)

    Bishop, Janice L.; Drief, Ahmed; Dyar, Darby

    2003-01-01

    Clays, if present on Mars, have been illusive. Determining whether or not clay minerals and other aqueous alteration species are present on Mars provides key information about the extent and duration of aqueous processes on Mars. The purpose of this study is to characterize in detail changes in the mineral grains resulting from grinding and to assess the influence of physical processes on clay minerals on the surface of Mars. Physical alteration through grinding was shown to greatly affect the structure and a number of properties of antigorite and kaolinite. This project builds on an initial study and includes a combination of SEM, HRTEM, reflectance and M ssbauer spectroscopies. Grain size was found to decrease, as expected, with grinding. In addition, nanophase carbonate, Si-OH and iron oxide species were formed.

  1. Investigation of Mediational Processes Using Parallel Process Latent Growth Curve Modeling

    Science.gov (United States)

    Cheong, JeeWon; MacKinnon, David P.; Khoo, Siek Toon

    2010-01-01

    This study investigated a method to evaluate mediational processes using latent growth curve modeling. The mediator and the outcome measured across multiple time points were viewed as 2 separate parallel processes. The mediational process was defined as the independent variable influencing the growth of the mediator, which, in turn, affected the growth of the outcome. To illustrate modeling procedures, empirical data from a longitudinal drug prevention program, Adolescents Training and Learning to Avoid Steroids, were used. The program effects on the growth of the mediator and the growth of the outcome were examined first in a 2-group structural equation model. The mediational process was then modeled and tested in a parallel process latent growth curve model by relating the prevention program condition, the growth rate factor of the mediator, and the growth rate factor of the outcome. PMID:20157639

  2. Effect of Process Variables on the Grain Size and Crystallographic Texture of Hot-Dip Galvanized Coatings

    Science.gov (United States)

    Kaboli, Shirin; McDermid, Joseph R.

    2014-08-01

    A galvanizing simulator was used to determine the effect of galvanizing bath antimony (Sb) content, substrate surface roughness, and cooling rate on the microstructural development of metallic zinc coatings. Substrate surface roughness was varied through the use of relatively rough hot-rolled and relatively smooth bright-rolled steels, cooling rates were varied from 0.1 to 10 K/s, and bulk bath Sb levels were varied from 0 to 0.1 wt pct. In general, it was found that increasing bath Sb content resulted in coatings with a larger grain size and strongly promoted the development of coatings with the close-packed {0002} basal plane parallel to the substrate surface. Increasing substrate surface roughness tended to decrease the coating grain size and promoted a more random coating crystallographic texture, except in the case of the highest Sb content bath (0.1 wt pct Sb), where substrate roughness had no significant effect on grain size except at higher cooling rates (10 K/s). Increased cooling rates tended to decrease the coating grain size and promote the {0002} basal orientation. Calculations showed that increasing the bath Sb content from 0 to 0.1 wt pct Sb increased the dendrite tip growth velocity from 0.06 to 0.11 cm/s by decreasing the solid-liquid interface surface energy from 0.77 to 0.45 J/m2. Increased dendrite tip velocity only partially explains the formation of larger zinc grains at higher Sb levels. It was also found that the classic nucleation theory cannot completely explain the present experimental observations, particularly the effect of increasing the bath Sb, where the classical theory predicts increased nucleation and a finer grain size. In this case, the "poisoning" theory of nucleation sites by segregated Sb may provide a partial explanation. However, any analysis is greatly hampered by the lack of fundamental thermodynamic information such as partition coefficients and surface energies and by a lack of fundamental structural studies. Overall

  3. Digital signal processing - growth of a technology

    International Nuclear Information System (INIS)

    Peek, J.B.H.

    1985-01-01

    The rapid development of microelectronics has led to an increasing extent in circuits and systems for digital signal processing. This happened first in professional applications, e.g. geophysics, astronomy and space flight, and now, with the Compact Disc player, these techniques have entered the consumer field. In the near future digital TV applications will undoubtedly follow. This article outlines a number of the developments behind the advancing 'digitization' of modern technology. The article also considers the main advantages and disadvantages of digital signal processing the main modules now used and some common applications. Particular attention is paid to medical applications. (Auth.)

  4. Mechanism for selective growth in electrical steel

    Science.gov (United States)

    Oh, Eun Jee; Heo, Nam Hoe; Kwon, Se Kyun; Koo, Yang Mo

    2018-01-01

    Through the competitive selective growth process between {100}, {110}, and {111} grains during final annealing which is governed by the primary grain size and the surface segregation concentration of sulfur, the sharp {110} annealing texture can be developed in a C-and Al-free Fe-3%Si-0.1%Mn electrical steel. Generally, the selective growth of the {110} grains occurs actively under the low surface segregation concentration of sulfur. In spite of the surface energy disadvantage, the selective growth of a {hkl} grain can however occur, if the {hkl} grain size is larger than the critical grain size linearly proportional to the strip thickness.

  5. Process for producing vegetative and tuber growth regulator

    Science.gov (United States)

    Stutte, Gary W. (Inventor); Yorio, Neil C. (Inventor)

    1999-01-01

    A process of making a vegetative and tuber growth regulator. The vegetative and tuber growth regulator is made by growing potato plants in a recirculating hydroponic system for a sufficient time to produce the growth regulator. Also, the use of the vegetative and growth regulator on solanaceous plants, tuber forming plants and ornamental seedlings by contacting the roots or shoots of the plant with a sufficient amount of the growth regulator to regulate the growth of the plant and one more of canopy size, plant height, stem length, internode number and presence of tubers in fresh mass. Finally, a method for regulating the growth of potato plants using a recirculating hydroponic system is described.

  6. Effects of partial replacement of corn grain with lactose in calf starters on ruminal fermentation and growth performance.

    Science.gov (United States)

    Saegusa, A; Inouchi, K; Ueno, M; Inabu, Y; Koike, S; Sugino, T; Oba, M

    2017-08-01

    The objective of this study was to evaluate effects of partial replacement of dry ground corn with lactose in calf starters on dry matter intake, growth rate, ruminal pH, and volatile fatty acid profile. Sixty Holstein bull calves were raised on a high plane of nutrition program until 55 d of age. Calves were fed texturized calf starters containing 30.1% steam-flaked grains and lactose at 0 (control), 5, or 10% (n = 20 for each treatment) on a dry matter basis. All calves were fed treatment calf starters ad libitum from d 7 and kleingrass hay from d 35. Ruminal pH was measured continuously immediately after weaning (d 55-62) for 15 calves (n = 5 per treatment), and 3 wk after weaning (d 77 to 80) for the other 45 calves (n = 15 per treatment). Dry matter intake, growth performance, and ruminal pH variables were not affected by treatment. However, according to Spearman's correlation coefficient (r s ) analyses, lactose intake was positively correlated with dairy minimum ruminal pH (r s = 0.306) for the data collected from d 77 to 80. Similarly, hay intake was not affected by treatment, but positively correlated with daily mean (r s = 0.338) and maximum ruminal pH (r s = 0.408) and negatively correlated with duration pH lactose than control (35.3 vs. 40.2%) for ruminal fluid collected on d 80; however, molar ratio of butyrate was not affected by treatment. These results indicate that lactose inclusion in calf starters up to 10% of dry matter might not affect dry matter intake and growth performance of calves, but that greater lactose and hay intake might be associated with higher ruminal pH. The Authors. Published by the Federation of Animal Science Societies and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

  7. Ultrafine-Grained Pure Ti Processed by New SPD Scheme Combining Drawing with Shear

    Science.gov (United States)

    Raab, A. G.; Bobruk, E. V.; Raab, G. I.

    2018-05-01

    The paper displays the results of the studies and analysis of a promising severe plastic deformation scheme that implements the conditions of a non-monotonous impact during shear drawing of long-length bulk metal materials. The paper describes the efficiency of the proposed severe plastic deformation technique to form a gradient ultrafine-grained state in rod-shaped billets on the example of commercially pure Ti and its further development for future industrial applications.

  8. Performance of process-based models for simulation of grain N in crop rotations across Europe

    Czech Academy of Sciences Publication Activity Database

    Xiaogang, Y.; Kesebaum, K. C.; Kollas, C.; Manevski, K.; Baby, S.; Beaudoin, N.; Öztürk, I.; Gaiser, T.; Wu, L.; Hoffmann, M.; Charfeddine, M.; Conradt, T.; Constantin, J.; Ewert, F.; de Cortazar-Atauri, I. G.; Giglio, L.; Hlavinka, Petr; Hoffmann, H.; Launay, M.; Louarn, G.; Manderscheid, R.; Mary, B.; Mirschel, W.; Nendel, C.; Pacholski, A.; Palouso, T.; Ripoche-Wachter, D.; Rötter, R. P.; Ruget, F.; Sharif, B.; Trnka, Miroslav; Ventrella, D.; Weigel, H-J.; Olesen, J. E.

    2017-01-01

    Roč. 154, JUN (2017), s. 63-77 ISSN 0308-521X R&D Projects: GA MŠk(CZ) LO1415; GA MZe QJ1310123 Institutional support: RVO:67179843 Keywords : Calibration * Crop model * Crop rotation * Grain N content * Model evaluation * Model initialization Subject RIV: EH - Ecology, Behaviour OBOR OECD: Environmental sciences (social aspects to be 5.7) Impact factor: 2.571, year: 2016

  9. The proportion of nitrate in leaf nitrogen, but not changes in root growth, are associated with decreased grain protein in wheat under elevated [CO2].

    Science.gov (United States)

    Bahrami, Helale; De Kok, Luit J; Armstrong, Roger; Fitzgerald, Glenn J; Bourgault, Maryse; Henty, Samuel; Tausz, Michael; Tausz-Posch, Sabine

    2017-09-01

    The atmospheric CO 2 concentration ([CO 2 ]) is increasing and predicted to reach ∼550ppm by 2050. Increasing [CO 2 ] typically stimulates crop growth and yield, but decreases concentrations of nutrients, such as nitrogen ([N]), and therefore protein, in plant tissues and grains. Such changes in grain composition are expected to have negative implications for the nutritional and economic value of grains. This study addresses two mechanisms potentially accountable for the phenomenon of elevated [CO 2 ]-induced decreases in [N]: N uptake per unit length of roots as well as inhibition of the assimilation of nitrate (NO 3 - ) into protein are investigated and related to grain protein. We analysed two wheat cultivars from a similar genetic background but contrasting in agronomic features (Triticum aestivum L. cv. Scout and Yitpi). Plants were field-grown within the Australian Grains Free Air CO 2 Enrichment (AGFACE) facility under two atmospheric [CO 2 ] (ambient, ∼400ppm, and elevated, ∼550ppm) and two water treatments (rain-fed and well-watered). Aboveground dry weight (ADW) and root length (RL, captured by a mini-rhizotron root growth monitoring system), as well as [N] and NO 3 - concentrations ([NO 3 - ]) were monitored throughout the growing season and related to grain protein at harvest. RL generally increased under e[CO 2 ] and varied between water supply and cultivars. The ratio of total aboveground N (TN) taken up per RL was affected by CO 2 treatment only later in the season and there was no significant correlation between TN/RL and grain protein concentration across cultivars and [CO 2 ] treatments. In contrast, a greater percentage of N remained as unassimilated [NO 3 - ] in the tissue of e[CO 2 ] grown crops (expressed as the ratio of NO 3 - to total N) and this was significantly correlated with decreased grain protein. These findings suggest that e[CO 2 ] directly affects the nitrate assimilation capacity of wheat with direct negative implications

  10. Regarding the perturbed operating process of DB propellant rocket motor at extreme initial grain temperatures

    Directory of Open Access Journals (Sweden)

    Ioan ION

    2012-03-01

    Full Text Available Despite many decades of study, the combustion instability of several DB propellants is still of particular concern, especially at extreme grain temperature conditions of rocket motor operating. The purpose of the first part of the paper is to give an overview of our main experimental results on combustion instabilities and pressure oscillations in DB propellant segmented grain rocket motors (SPRM-01, large L/D ratio, working at extreme initial grain temperatures. Thus, we recorded some particular pressure-time traces with significant perturbed pressure signal that was FFT analysed. An updated mathematical model incorporating transient frequency-dependent combustion response, in conjunction with pressure-dependent burning, is applied to investigate and predict the DB propellant combustion instability phenomenon. The susceptibility of the tested motor SPRM-01 with DB propellant to get a perturbed working and to go unstable with pressure was evidenced and this risk has to be evaluated. In the last part of our paper we evaluated the influence of recorded perturbed thrust on the rocket behaviour on the trajectory. The study revealed that at firing-table initial conditions, this kind of perturbed motor operating may not lead to an unstable rocket flight, but the ballistic parameters would be influenced in an unacceptable manner.

  11. The effect of secondary abnormal grain growth on the dielectric properties of La/Mn co-doped BaTiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Živković Lj.M.

    2006-01-01

    Full Text Available La/Mn-codoped BaTiO3 systems, obtained by solid state reactions, were investigated regarding their microstructure characteristics and ferroelectric properties. Different concentrations of La2O3 were used for doping, ranging from 0.1 to 5.0 at% La, while a content of Mn was constant at 0.05 at%. For all samples sintered below the eutectic temperature (1332°C, a uniform microstructure was formed with average grain size from 1-3 μm. The appearance of secondary abnormal grains with (111 double twins grains with curved or faceted grain boundaries were observed in La/Mn BaTiO3 ceramics after sintering at temperatures above the eutectic temperature. All sintered samples exhibited a high electrical resistivity. Better dielectric performances were obtained for low doped samples (0.1 at% La sintered at 1350°C. For samples with La content above 1.0 at% a lower value in dielectric permittivity at higher sintering temperature is due to secondary abnormal grain growth, and to the presence of a non-ferroelectric phase rich in La. The Curie constant together with other dielectric parameters were also calculated.

  12. Effects of die profile on grain refinement in Al–Mg alloy processed by repetitive corrugation and straightening

    Energy Technology Data Exchange (ETDEWEB)

    Thangapandian, N., E-mail: erpandian@gmail.com [Department of Mechanical Engineering, College of Engineering Guindy, Anna University, Chennai 600025 (India); Balasivanandha Prabu, S. [Department of Mechanical Engineering, College of Engineering Guindy, Anna University, Chennai 600025 (India); Padmanabhan, K.A. [Centre for Nanotechnology, University of Hyderabad, Hyderabad 500046 (India)

    2016-01-01

    It is shown that a proper selection of corrugation die profile and die parameters is essential for achieving homogeneous grain refinement in materials subjected to repetitive corrugation and straightening (RCS). An Al–Mg (AA 5083) alloy was subjected to the RCS process using three different corrugation die profiles (V-groove, Flat groove, and Semi-circular groove), followed by straightening to determine the allowable maximum number of passes prior to surface cracking/fracture. Mechanical properties, i.e., hardness and tensile strength of the RCS samples were measured and compared as functions of corrugation die profiles and number of passes and the changes in microstructure. Grain refinement was studied using Electron Back Scattered Diffraction (EBSD) analysis and Transmission Electron Microscopy (TEM).

  13. Evolution and the Growth Process: Natural Selection of Entrepreneurial Traits.

    Science.gov (United States)

    Galor, Oded; Michalopoulos, Stelios

    2012-03-01

    This research suggests that a Darwinian evolution of entrepreneurial spirit played a significant role in the process of economic development and the dynamics of inequality within and across societies. The study argues that entrepreneurial spirit evolved non-monotonically in the course of human history. In early stages of development, risk-tolerant, growth promoting traits generated an evolutionary advantage and their increased representation accelerated the pace of technological progress and the process of economic development. In mature stages of development, however, risk-averse traits gained an evolutionary advantage, diminishing the growth potential of advanced economies and contributing to convergence in economic growth across countries.

  14. Evolution and the Growth Process: Natural Selection of Entrepreneurial Traits*

    Science.gov (United States)

    Galor, Oded; Michalopoulos, Stelios

    2013-01-01

    This research suggests that a Darwinian evolution of entrepreneurial spirit played a significant role in the process of economic development and the dynamics of inequality within and across societies. The study argues that entrepreneurial spirit evolved non-monotonically in the course of human history. In early stages of development, risk-tolerant, growth promoting traits generated an evolutionary advantage and their increased representation accelerated the pace of technological progress and the process of economic development. In mature stages of development, however, risk-averse traits gained an evolutionary advantage, diminishing the growth potential of advanced economies and contributing to convergence in economic growth across countries. PMID:25089059

  15. Scaling behaviour of randomly alternating surface growth processes

    CERN Document Server

    Raychaudhuri, S

    2002-01-01

    The scaling properties of the roughness of surfaces grown by two different processes randomly alternating in time are addressed. The duration of each application of the two primary processes is assumed to be independently drawn from given distribution functions. We analytically address processes in which the two primary processes are linear and extend the conclusions to nonlinear processes as well. The growth scaling exponent of the average roughness with the number of applications is found to be determined by the long time tail of the distribution functions. For processes in which both mean application times are finite, the scaling behaviour follows that of the corresponding cyclical process in which the uniform application time of each primary process is given by its mean. If the distribution functions decay with a small enough power law for the mean application times to diverge, the growth exponent is found to depend continuously on this power-law exponent. In contrast, the roughness exponent does not depe...

  16. Role of high microwave power on growth and microstructure of thick nanocrystalline diamond films: A comparison with large grain polycrystalline diamond films

    Science.gov (United States)

    Tang, C. J.; Fernandes, A. J. S.; Girão, A. V.; Pereira, S.; Shi, Fa-Nian; Soares, M. R.; Costa, F.; Neves, A. J.; Pinto, J. L.

    2014-03-01

    In this work, we study the growth habit of nanocrystalline diamond (NCD) films by exploring the very high power regime, up to 4 kW, in a 5 kW microwave plasma chemical vapour deposition (MPCVD) reactor, through addition of a small amount of nitrogen and oxygen (0.24%) into 4% CH4 in H2 plasma. The coupled effect of high microwave power and substrate temperature on NCD growth behaviour is systematically investigated by varying only power, while fixing the remaining operating parameters. When the power increases from 2 kW to 4 kW, resulting also in rise of the Si substrate temperature higher than 150 °C, the diamond films obtained maintain the NCD habit, while the growth rate increases significantly. The highest growth rate of 4.6 μm/h is achieved for the film grown at 4 kW, which represents a growth rate enhancement of about 15 times compared with that obtained when using 2 kW power. Possible factors responsible for such remarkable growth rate enhancement of the NCD films are discussed. The evolution of NCD growth characteristics such as morphology, microstructure and texture is studied by growing thick films and comparing it with that of large grain polycrystalline (PCD) films. One important characteristic of the NCD films obtained, in contrast to PCD films, is that irrespective of deposition time (i.e. film thickness), their grain size and surface roughness remain in the nanometer range throughout the growth. Finally, based on our present and previous experimental results, a potential parameter window is established for fast growth of NCD films under high power conditions.

  17. DEVELOPMENT OF GRAIN MARKET IN UKRAINE

    Directory of Open Access Journals (Sweden)

    Aleksandr Maslak

    2015-11-01

    Full Text Available The subject of the research is a set of theoretical, methodological and practical fundamentals of organizational and economic functioning are integrated agricultural formations in the grain market of Ukraine. The methodological basis of research is the complex analysis of economic processes in the grain market in Ukraine and the world. During research we used such methods as method of systematization and comparison, statistic, economic, balance, constructive, target-oriented, and the methods of induction and deduction, analogy and comparison. Main aim of this article is the analysis of the situation on the grain market in Ukraine, defining the role of integrated agricultural formations in this market, improving the organizational-economic mechanism of its functioning, identifies ways of improving the competitiveness of Ukraine among world exporters of grain. Using results of the studies we examined trends grain market in Ukraine; influence of businesses in grain production; analysis of constraints to improve production efficiency of grain; defined domestic (internal needs of grain in Ukraine; assessed the status and expediency transformation infrastructure of the grain market of Ukraine; defined priority directions of development of the grain market in Ukraine. As a result of the preparation of articles, it is obtained the following conclusions: Ukraine is the world's largest producers and exporters of grain, the production of integrated agricultural units to a third of the total grain; technical condition of farm does not meet the needs of production; the domestic market is unable to provide the existing demand for grain production, contributing to export growth; Ukraine has a number of problems due to increased grain production, namely the shortage of storage capacity for the storage of grain, limited performance transshipment of grain in port elevators and imperfection and depreciation of transport systems; solving the existing problems is

  18. Stochastic process corrosion growth models for pipeline reliability

    International Nuclear Information System (INIS)

    Bazán, Felipe Alexander Vargas; Beck, André Teófilo

    2013-01-01

    Highlights: •Novel non-linear stochastic process corrosion growth model is proposed. •Corrosion rate modeled as random Poisson pulses. •Time to corrosion initiation and inherent time-variability properly represented. •Continuous corrosion growth histories obtained. •Model is shown to precisely fit actual corrosion data at two time points. -- Abstract: Linear random variable corrosion models are extensively employed in reliability analysis of pipelines. However, linear models grossly neglect well-known characteristics of the corrosion process. Herein, a non-linear model is proposed, where corrosion rate is represented as a Poisson square wave process. The resulting model represents inherent time-variability of corrosion growth, produces continuous growth and leads to mean growth at less-than-one power of time. Different corrosion models are adjusted to the same set of actual corrosion data for two inspections. The proposed non-linear random process corrosion growth model leads to the best fit to the data, while better representing problem physics

  19. Influence of fibre distribution and grain size on the mechanical behaviour of friction stir processed Mg–C composites

    Energy Technology Data Exchange (ETDEWEB)

    Mertens, A., E-mail: anne.mertens@ulg.ac.be [Université de Liège, Faculty of Applied Science, A& M Department, Metallic Materials Science Unit (Belgium); Simar, A. [Université catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (Belgium); Adrien, J.; Maire, E. [Institut National des Sciences Appliquées de Lyon (INSA Lyon), MATEIS Laboratory (France); Montrieux, H.-M. [Université de Liège, Faculty of Applied Science, A& M Department, Metallic Materials Science Unit (Belgium); Delannay, F. [Université catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (Belgium); Lecomte-Beckers, J. [Université de Liège, Faculty of Applied Science, A& M Department, Metallic Materials Science Unit (Belgium)

    2015-09-15

    Short C fibres–Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of Mg alloy AZ31B or AZ91D. This novel processing technique can allow the easy production of large-scale metal matrix composites. The paper investigates the microstructure of FSPed C fibre–Mg composites in relation with the fragmentation of the C fibres during FSP and their influence on the tensile properties. 3D X-ray tomography reveals that the fibres orient like onion rings and are more or less fragmented depending on the local shear stress during the process. The fibre volume fraction can be increased from 2.3% to 7.1% by reducing the nugget volume, i.e. by using a higher advancing speed in AZ31B alloy or a stronger matrix alloy, like AZ91D alloy. A higher fibre volume fraction leads to a smaller grain size which brings about an increase of the composite yield strength by 15 to 25%. However, a higher fibre volume fraction also leads to a lower fracture strain. Fracture surface observations reveal that damage occurs by fibre/matrix decohesion along fibres oriented perpendicularly to the loading direction. - Graphical abstract: Display Omitted - Highlights: • C–Mg MMCs were produced by FSP sandwiches made of a C fabric between Mg sheets. • Fibre fragmentation and erosion is larger when the temperature reached during FSP is lower. • A lower advancing speed brings a lower fibre volume fraction and a lower grain size. • X-ray tomography reveals that fibres orient along the FSP material flow. • The fibres and grain size reduction increase the yield strength by 15 to 25%.

  20. Modelling detrital coral grain-size and age: Insights from sediment abrasion process of Yongle Atoll of South China Sea

    Science.gov (United States)

    Li, Y.; Zou, X.; Ge, C.; Tan, M.; Wang, C.

    2017-12-01

    Reef islands situated on the rims of atolls are composed almost exclusively of bioclastic materials locally supplied from adjacent coral reefs. Major skeletal component of these islands include coral, coralline algae, mollusks and foraminifera, produced in adjacent reefs. As the island builder, the bioclastic material is the sedimentary products, which also is the point of penetration to decipher the process. The bioclast of coral islands decrease in size with the transportation process. The grain-size provides a proxy record for the abrasion history of the unconsolidated sediment. The 230Th age of coral record the abrasion time. We hereby present a model to calculate the abrasion rate based on the data of 230Th age and grain-size of Yongle Atoll of Xisha Island, South China Sea. The grain size pattern in Yongle Atoll environment have confirm that the coral article diminution behave exponentially. The sediment composition of Yongle Atoll is identified, coral is dominant sediment constituent and the Th230 age is shown to exert an age distribution characteristics of coral detritus. We illustrate this approach by calculate the coral debris age of Xude Atoll, which located near the Yongle Atoll and then by comparing actual measured age and calculated age and to explore the dependence of the model. Observed 230 Th ages are well matched by predicted ages for medium age sediment. A poorer match for young and old sediment may result from some combination of large analytical uncertainties in the detrital ages and inhomogeneous erosion rates within the atoll. Such mismatches emphasize the need for more accurate kinematic models and for sampling strategies that are adapted to atoll-specific geologic and geomorphic conditions. Results presented constitute important new insights into regional sediment abrasion processed and on the evolution of coral atoll islands.

  1. Elastocaloric effects in ultra-fine grained NiTi microwires processed by cold-drawing

    Directory of Open Access Journals (Sweden)

    Xuexi Zhang

    2018-03-01

    Full Text Available Efficient elastocaloric cooling in shape memory alloys requires a stable superelastic behavior in which high yield strength is needed. Here Ni50.4Ti49.6 microwires with diameter 130 μm and ultra-fine grains ∼30 nm were prepared by multi-step cold-drawing and low-temperature annealing. Enhanced cyclic stability of the elastocaloric effects induced by the superelastic training was demonstrated. The pre-trained microwire showed a stable ΔSe 43 J/(kg K with a broad working temperature range ΔT ∼ 70 K. The superelastic trained microwire, with giant and stable ΔSe over a wide working temperature window, may act as a promising elastocaloric cooling material for minor-sized devices.

  2. Effects of process parameters on the properties of barley containing snacks enriched with brewer's spent grain.

    Science.gov (United States)

    Kirjoranta, Satu; Tenkanen, Maija; Jouppila, Kirsi

    2016-01-01

    Brewer's spent grain (BSG), a by-product of malting of barley in the production of malt extract, was used as an ingredient in extruded barley-based snacks in order to improve the nutritional value of the snacks and widen the applications of this by-product in food sector. The effects of the extrusion parameters on the selected properties of the snacks were studied. Snacks with different ingredients including whole grain barley flour, BSG, whey protein isolate (WPI), barley starch and waxy corn starch were produced in 5 separate trials using a co-rotating twin-screw extruder. Extrusion parameters were water content of the mass (17-23 %), screw speed (200-500 rpm) and temperature of the last section and die (110-150 °C). Expansion, hardness and water content of the snacks were determined. Snacks containing barley flour and BSG (10 % of solids) had small expansion and high hardness. Addition of WPI (20 % of solids) increased expansion only slightly. Snacks with high expansion and small hardness were obtained when part of the barley flour was replaced with starch (barley or waxy corn). Yet, the highest expansion and the smallest hardness were achieved when barley flour was used with barley starch and WPI without BSG. Furthermore, expansion increased by increasing screw speed and decreasing water content of the mass in most of the trials. This study showed that BSG is a suitable material for extruded snacks rich in dietary fiber. Physical properties of the snacks could be improved by using barley or waxy corn starch and WPI.

  3. Thermal stability, thermal expansion and grain-growth in exchange-coupled Fe-Pt-Ag-B bulk nanocomposite magnets

    International Nuclear Information System (INIS)

    Nicula, R.; Crisan, O.; Crisan, A.D.; Mercioniu, I.; Stir, M.; Vasiliu, F.

    2015-01-01

    Highlights: • Formation of the L10 FePt hard-magnetic phase (>90%) directly in the as-cast state. • Specific alternating hard/soft nanostructure is stable to 600 °C without grain growth. • Anisotropic and non-linear thermal expansion effects. • The FePtAgB alloy behaves like a single magnetic phase (full exchange coupling). - Abstract: Rare-earth free (RE-free) exchange coupling nanocomposite magnets are intensively studied nowadays due to their potential use in applications demanding stable high-temperature operation and corrosion resistance. In this respect, the FePt alloy system is one of the most actively addressed potential permanent magnet solutions. In FePt alloys, promising magnetic features arise from the co-existence of hard magnetic L1 0 FePt and soft magnetic L1 2 Fe 3 Pt phases emerged from the same metastable precursor. The present work deals with an in-situ temperature-resolved synchrotron radiation study of the thermal stability, thermal expansion and microstructure evolution in exchange-coupled FePtAgB alloys. The as-cast microstructural state as well as the optimized magnetic behavior are given as reference and correlated to the observed microstructural evolution with temperature. The melt-spun Fe 48 Pt 28 Ag 6 B 18 alloy ribbons were examined in situ by synchrotron X-ray powder diffraction from ambient temperature up to 600 °C. The FePt-Fe 3 Pt exchange-coupled microstructure achieved by rapid solidification is not significantly altered during the high temperature exposure. The thermal expansion of the FePt L1 0 unit cell has been found to be strongly anisotropic, being essentially an in-plane expansion which may be seen as an anisotropic invar effect. For the FePt L1 0 phase, a significant deviation from linear thermal expansion is observed at the Curie temperature T C = 477 °C. This non-linear behavior above T C is tentatively linked to a diffusion/segregation mechanism of Ag. The promising hard magnetic properties as well as the

  4. Zirconia thin films from aqueous precursors: Processing, microstructural development, and epitaxial growth

    International Nuclear Information System (INIS)

    Miller, K.T.

    1991-01-01

    Thin films of ZrO 2 (Y 2 O 3 ) were prepared from aqueous salt precursors by spin coating. Films were pyrolyzed to produce porous polycrystalline thin films of 5-10 nm grain size. Subsequent microstructural development depends greatly upon the nature of the substrate. Upon randomly oriented sapphire, the films initially sintered to full density; further heat treatment and grain growth causes these films to break into interconnected islands and finally isolated particles. Thermodynamic calculations predict that breakup is energetically favorable when the grain-size film-thickness ratio exceeds a critical value. Upon basal-plane-oriented sapphire, grain growth and breakup prefer the (100) oriented grains, presumably because this orientation is a special interface of low energy. The isolated, oriented grains produced by film breakup act as seeds for the growth of newly deposited material. Upon (100) cubic zirconia, true epitaxial films develop. Epitaxial growth was observed for lattice mismatches up to 1.59%. Growth proceeds from a fine epitaxial layer which is produced during the initial stages of heat treatment, consuming the porous polycrystalline material and producing a dense epitaxial thin film whose misfit is accommodated by a combination of film strain and misfit dislocations

  5. The effect of feeding wheat varieties with different grain pigmentation on growth performance, texture, colour and meat sensory traits of broiler chickens

    Directory of Open Access Journals (Sweden)

    Ondřej Šťastník

    2017-01-01

    Full Text Available The feeding effect of of three spring wheat genotypes (Vánek, Konini and UC66049 with different grain colour on growth performance, body composition and meat quality parameters of broiler chickens was tested. Ninety chickens were divided into three groups (control, Konini and UC with 30 chickens in each. The tested genotypes were compares with standard variety Vánek (control with common (red grain colour. The two experimental groups received feed mixtures containing 38.2% of wheats with different grain colour: groups Konini (n = 30 and UC (n = 30 with. The third group (n = 30 had 38.2% of common wheat Vánek cultivar (Control group. The live weight of chickens between the experimental groups and control group was not significant different, as well as body composition and chemical analysis of breast and thigh meat of chickens. The feeding of wheat with different grain colour had no effect on performance parameters of broiler chickens. Breast meat tenderness according to the Razor Blade Shear Force was higher in control group against experimental groups. The colour change was not significantly different in all coordinates. pH values (measured after 1-hour post mortem were found significantly higher in the group fattening with Konini wheat than control and UC groups. Chickens meat from the experimental group was characterised by steady overall quality. The effect of various feeding had no effect on meat quality in terms of relevance to consumers.

  6. Evolution of microstructure, texture and inhibitor along the processing route for grain-oriented electrical steels using strip casting

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hai-Tao, E-mail: liuht@ral.neu.edu.cn [State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, Shenyang 110819 (China); Institute of Research of Iron and Steel, Shasteel, Zhangjiagang 215625, Jiangsu (China); Yao, Sheng-Jie [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, 264209 (China); Sun, Yu; Gao, Fei; Song, Hong-Yu; Liu, Guo-Huai [State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, Shenyang 110819 (China); Li, Lei; Geng, Dian-Qiao [Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Liu, Zhen-Yu; Wang, Guo-Dong [State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, Shenyang 110819 (China)

    2015-08-15

    In the present work, a regular grade GO sheet was produced successively by strip casting, hot rolling, normalizing annealing, two-stage cold rolling with intermediate annealing, primary recrystallization annealing, secondary recrystallization annealing and purification. The aim of this paper was to characterize the evolution of microstructure, texture and inhibitor along the new processing route by comprehensive utilization of optical microscopy, X-ray diffraction and transmission electron microscopy. It was found that a fine microstructure with the ferrite grain size range of 7–12 μm could be obtained in the primary recrystallization annealed sheet though a very coarse microstructure was produced in the initial as-cast strip. The main finding was that the “texture memory” effect on Goss texture started on the through-thickness intermediate annealed strip after first cold rolling, which was not similar to the “texture memory” effect on Goss texture starting on the surface layers of the hot rolled strip in the conventional production route. As a result, the origin of Goss nuclei capable of secondary recrystallization lied in the grains already presented in Goss orientation in the intermediate annealed strip after first cold rolling. Another finding was that fine and dispersive inhibitors (mainly AlN) were easy to be produced in the primary recrystallization microstructure due to the initial rapid solidification during strip casting and the subsequent rapid cooling, and the very high temperature reheating usually used before hot rolling in the conventional production route could be avoided. - Highlights: • A regular grade grain-oriented electrical steel was produced. • Evolution of microstructure, texture and inhibitor was characterized. • Origin of Goss nuclei lied in the intermediate annealed strip. • A fine primary recrystallization microstructure could be produced. • Effective inhibitors were easy to be obtained in the new processing route.

  7. Investigation of Abnormal Grain Growth in a Friction Stir Welded and Spin-Formed Al-Li Alloy 2195 Crew Module

    Science.gov (United States)

    Tayon, Wesley A.; Domack, Marcia S.; Hoffman, Eric K.; Hales, Stephen J.

    2013-01-01

    In order to improve manufacturing efficiency and reduce structural mass and costs in the production of launch vehicle structures, NASA is pursuing a wide-range of innovative, near-net shape manufacturing technologies. A technology that combines friction stir welding (FSW) and spin-forming has been applied to manufacture a single-piece crew module using Aluminum-Lithium (AL-Li) Alloy 2195. Plate size limitations for Al-Li alloy 2195 require that two plates be FSW together to produce a spin-forming blank of sufficient size to form the crew module. Subsequent forming of the FSW results in abnormal grain growth (AGG) within the weld region upon solution heat treatment (SHT), which detrimentally impacts strength, ductility, and fracture toughness. The current study seeks to identify microstructural factors that contribute to the development of AGG. Electron backscatter diffraction (EBSD) was used to correlate driving forces for AGG, such as stored energy, texture, and grain size distributions, with the propensity for AGG. Additionally, developmental annealing treatments prior to SHT are examined to reduce or eliminate the occurrence of AGG by promoting continuous, or uniform, grain growth

  8. The effect of grain refinement and silicon content on grain formation in hypoeutectic Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.C.; Dahle, A.K.; StJohn, D.H.; Hutt, J.E.C. [Queensland Univ., Brisbane (Australia). Dept. of Mining, Minerals and Mater. Eng.

    1999-01-15

    The effect of increasing the amount of added grain refiner on grain size and morphology has been investigated for a range of hypoeutectic Al-Si alloys. The results show a transition in grain size at a silicon concentration of about 3 wt% in unrefined alloys; the grain size decreasing with silicon content before the transition, and increasing beyond the transition point. A change in morphology also occurs with increased silicon content. The addition of grain refiner leads to greater refinement for silicon contents below the transition point than for those contents above the transition point, while the transition point seems to remain unchanged. The slope of the grain size versus silicon content curve after the transition seems to be unaffected by the degree of grain refinement. The results are related to the competitive processes of nucleation and constitutional effects during growth and their impact on nucleation kinetics. (orig.) 13 refs.

  9. Elevating Virtual Machine Introspection for Fine-Grained Process Monitoring: Techniques and Applications

    Science.gov (United States)

    Srinivasan, Deepa

    2013-01-01

    Recent rapid malware growth has exposed the limitations of traditional in-host malware-defense systems and motivated the development of secure virtualization-based solutions. By running vulnerable systems as virtual machines (VMs) and moving security software from inside VMs to the outside, the out-of-VM solutions securely isolate the anti-malware…

  10. The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

    Science.gov (United States)

    Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

    2017-09-01

    The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to

  11. The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

    Directory of Open Access Journals (Sweden)

    Florian Steinbach

    2017-09-01

    Full Text Available The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD have been used together with c-axis orientations using an optical technique (Fabric Analyser. Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be

  12. Growth

    Science.gov (United States)

    John R. Jones; George A. Schier

    1985-01-01

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

  13. Observation of changing crystal orientations during grain coarsening

    International Nuclear Information System (INIS)

    Sharma, Hemant; Huizenga, Richard M.; Bytchkov, Aleksei; Sietsma, Jilt; Offerman, S. Erik

    2012-01-01

    Understanding the underlying mechanisms of grain coarsening is important in controlling the properties of metals, which strongly depend on the microstructure that forms during the production process or during use at high temperature. Grain coarsening of austenite at 1273 K in a binary Fe–2 wt.% Mn alloy was studied using synchrotron radiation. Evolution of the volume, average crystallographic orientation and mosaicity of more than 2000 individual austenite grains was tracked during annealing. It was found that an approximately linear relationship exists between grain size and mosaicity, which means that orientation gradients are present in the grains. The orientation gradients remain constant during coarsening and consequently the character of grain boundaries changes during coarsening, affecting the coarsening rate. Furthermore, changes in the average orientation of grains during coarsening were observed. The changes could be understood by taking the observed orientation gradients and anisotropic movement of grain boundaries into account. Five basic modes of grain coarsening were deduced from the measurements, which include: anisotropic (I) and isotropic (II) growth (or shrinkage); movement of grain boundaries resulting in no change in volume but a change in shape (III); movement of grain boundaries resulting in no change in volume and mosaicity, but a change in crystallographic orientation (IV); no movement of grain boundaries (V).

  14. Removal of tetrachloroethylene from fine-grained soils by electrokinetic processes

    Energy Technology Data Exchange (ETDEWEB)

    Steger, H.; Zorn, R.; Haus, R.; Czurda, K. [Dept. of Applied Geology, Karlsruhe Univ. (Germany)

    2001-07-01

    The aim of this study was to investigate the mobilization of tetrachloroethylene (PCE) by a bench scale experiment in a naturally contaminated, undisturbed soil core of a fine-grained valley deposit, which was taken on a factory site in Germany. In order to regard the physico-chemical properties of PCE the experiment was carried out in an especially developed laboratory cell. In the beginning of the bench scale test natural in situ temperature conditions of 9 C were simulated in the sample by using an external, infinitely variable cooling. After 6 days the cooling was switched off. During the cooling period the electroosmotic permeability was about 1.5-2 times lower than under laboratory conditions. After 3.5 displaced pore volumes almost all PCE was removed out of the soil. Furthermore, no significant degradation reaction of PCE to trichloroethylene (TCE), cis-1,2-dichloroethene, trans-1,2 dichloroethene and 1,1 dichloroethene took place. A variation in the mineralogical composition was determined, due to the production of hydronium ions and hydroxide ions by electrolyse reactions at the electrodes. At the anode region carbonate was dissolved and at the cathode region calcium and magnesium hydroxide precipitated. (orig.)

  15. Infrared Spectroscopic Survey of the Quiescent Medium of Nearby Clouds. I. Ice Formation and Grain Growth in Lupus

    NARCIS (Netherlands)

    Boogert, A.; Chiar, J.; Knez, C.; Öberg, K.; Mundy, L.; Pendleton, Y.; Tielens, A.G.G.M.; Dishoeck, van E.F.

    2013-01-01

    Infrared photometry and spectroscopy (1-25 {$μ$}m) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H$_{2}$O ices form at extinctions of A

  16. The effect of dopants on grain growth and PL in CZTS nanoparticle thin films for solar cell applications

    DEFF Research Database (Denmark)

    Engberg, Sara Lena Josefin; Crovetto, Andrea; Hansen, Ole

    . In addition, the photoluminescence signal increased by a factor of 200 after Na-inclusion. Without Na, the grains were very difficult to sinter, the film was porous, and the photoluminescence was low. This suggests that including Na reduces interface recombination in CZTS nanoparticle absorber layers...

  17. Sediment transport processes in the Pearl River Estuary as revealed by grain-size end-member modeling and sediment trend analysis

    Science.gov (United States)

    Li, Tao; Li, Tuan-Jie

    2018-04-01

    The analysis of grain-size distribution enables us to decipher sediment transport processes and understand the causal relations between dynamic processes and grain-size distributions. In the present study, grain sizes were measured from surface sediments collected in the Pearl River Estuary and its adjacent coastal areas. End-member modeling analysis attempts to unmix the grain sizes into geologically meaningful populations. Six grain-size end-members were identified. Their dominant modes are 0 Φ, 1.5 Φ, 2.75 Φ, 4.5 Φ, 7 Φ, and 8 Φ, corresponding to coarse sand, medium sand, fine sand, very coarse silt, silt, and clay, respectively. The spatial distributions of the six end-members are influenced by sediment transport and depositional processes. The two coarsest end-members (coarse sand and medium sand) may reflect relict sediments deposited during the last glacial period. The fine sand end-member would be difficult to transport under fair weather conditions, and likely indicates storm deposits. The three remaining fine-grained end-members (very coarse silt, silt, and clay) are recognized as suspended particles transported by saltwater intrusion via the flood tidal current, the Guangdong Coastal Current, and riverine outflow. The grain-size trend analysis shows distinct transport patterns for the three fine-grained end-members. The landward transport of the very coarse silt end-member occurs in the eastern part of the estuary, the seaward transport of the silt end-member occurs in the western part, and the east-west transport of the clay end-member occurs in the coastal areas. The results show that grain-size end-member modeling analysis in combination with sediment trend analysis help to better understand sediment transport patterns and the associated transport mechanisms.

  18. Growth performance, feeding behavior, and selected blood metabolites of Holstein dairy calves fed restricted amounts of milk: No interactions between sources of finely ground grain and forage provision.

    Science.gov (United States)

    Mirzaei, M; Khorvash, M; Ghorbani, G R; Kazemi-Bonchenari, M; Ghaffari, M H

    2017-02-01

    The objective of this study was to investigate the effects of grain sources and forage provision on growth performance, blood metabolites, and feeding behaviors of dairy calves. Sixty 3-d-old Holstein dairy calves (42.2 ± 2.5 kg of body weight) were used in a 2 × 3 factorial arrangement with the factors being grain sources (barley and corn) and forage provision (no forage, alfalfa hay, and corn silage). Individually housed calves were randomly assigned (n = 10 calves per treatment: 5 males and 5 females) to 6 treatments: (1) barley grain (BG) without forage supplement, (2) BG with alfalfa hay (AH) supplementation, (3) BG with corn silage (CS) supplementation, (4) corn grain (CG) without forage supplement, (5) CG with AH supplementation, and (6) CG with CS supplementation. All calves had ad libitum access to water and starter feed throughout the experiment. All calves were weaned on d 49 and remained in the study until d 63. Starter feed intake and average daily gain (ADG) was greater for calves fed barley than those fed corn during the preweaning and overall periods. Calves supplemented with CS had greater final body weight and postweaning as well as overall starter feed intake than AH and non-forage-supplemented calves. During the preweaning and overall periods, feeding of CS was found to increase ADG compared with feeding AH and nonforage diets. However, feed efficiency was not affected by dietary treatments. Calves supplemented with CS spent more time ruminating compared with AH and control groups; nonnutritive oral behaviors were the greatest in non-forage-supplemented calves. Regardless of the grain sources, the rumen pH value was greater for AH calves compared with CS and non-forage-supplemented calves. Blood concentration of BHB was greater for CS-supplemented calves compared with AH and non-forage-supplemented calves. Furthermore, body length and heart girth were greater for calves fed barley compared with those fed corn, and also in forage

  19. Combining x-ray diffraction contrast tomography and mesoscale grain growth simulations in strontium titanate: An integrated approach for the investigation of microstructure evolution

    DEFF Research Database (Denmark)

    Syha, Melanie; Baürer, Michael; Rheinheimer, Wolfgang

    2013-01-01

    Motivated by the recently reported a growth anomaly in strontium titatate bulk samples1, the microstructure of bulk strontium titanate has been investigated by an integrated approach comprising conventional metallography, three dimensional X-ray diffraction contrast tomography (DCT)2, and the obs......Motivated by the recently reported a growth anomaly in strontium titatate bulk samples1, the microstructure of bulk strontium titanate has been investigated by an integrated approach comprising conventional metallography, three dimensional X-ray diffraction contrast tomography (DCT)2......, and the observation of pore shapes in combination with mesoscale grain growth simulations. The microstructural evolution in strontium titanate has been characterized alternating ex-situ annealing and high energy X-ray DCT measurements, resulting in three dimensional microstructure reconstructions which...

  20. Processing diets containing corn distillers' dried grains with solubles in growing broiler chickens: effects on performance, pellet quality, ileal amino acids digestibility, and intestinal microbiota.

    Science.gov (United States)

    Kim, J S; Hosseindoust, A R; Shim, Y H; Lee, S H; Choi, Y H; Kim, M J; Oh, S M; Ham, H B; Kumar, A; Chae, B J

    2018-04-03

    The present study investigated the effects of feed form and distillers' dried grains with solubles (DDGS) on growth performance, nutrient digestibility, and intestine microbiota in broilers. A total of 720 broilers (Ross 308; average BW 541 ± 6 g) was randomly allotted to 6 treatments on the basis of BW. There were 6 replicates in each treatment with 20 birds per replicate. Birds were fed 3 different feed forms (mash, simple pellet, and expanded pellet) and DDGS (0 or 20% of diet) in a 3 × 2 factorial arrangement. Simple pellet (SP) and expanded pellet (EP) fed birds showed an increase in BW gain (P digestibility of CP compared to mash feed. The inclusion of DDGS decreased the digestibility of CP, and tended to decrease digestibility of DM (P = 0.056) and gross energy (P = 0.069). Expanded pellet feeding decreased (P digestibility of isoleucine, lysine, methionine, phenylalanine, threonine, cysteine, and glutamine compared with mash diet. Processed feed increased (P digestibility. In addition, DDGS supplementation (20%) decreased pellet quality and CP digestibility in broiler chickens; however, the growth performance and feed intake were not affected.

  1. Interpretation of sedimentological processes of coarse-grained deposits applying a novel combined cluster and discriminant analysis

    Directory of Open Access Journals (Sweden)

    Farics Éva

    2017-10-01

    Full Text Available The main aim of this paper is to determine the depositional environments of an Upper-Eocene coarse-grained clastic succession in the Buda Hills, Hungary. First of all, we measured some commonly used parameters of samples (size, amount, roundness and sphericity in a much more objective overall and faster way than with traditional measurement approaches, using the newly developed Rock Analyst application. For the multivariate data obtained, we applied Combined Cluster and Discriminant Analysis (CCDA in order to determine homogeneous groups of the sampling locations based on the quantitative composition of the conglomerate as well as the shape parameters (roundness and sphericity. The result is the spatial pattern of these groups, which assists with the interpretation of the depositional processes. According to our concept, those sampling sites which belong to the same homogeneous groups were likely formed under similar geological circumstances and by similar geological processes.

  2. Molecular dynamics simulation of self-diffusion processes in titanium in bulk material, on grain junctions and on surface.

    Science.gov (United States)

    Sushko, Gennady B; Verkhovtsev, Alexey V; Yakubovich, Alexander V; Schramm, Stefan; Solov'yov, Andrey V

    2014-08-21

    The process of self-diffusion of titanium atoms in a bulk material, on grain junctions and on surface is explored numerically in a broad temperature range by means of classical molecular dynamics simulation. The analysis is carried out for a nanoscale cylindrical sample consisting of three adjacent sectors and various junctions between nanocrystals. The calculated diffusion coefficient varies by several orders of magnitude for different regions of the sample. The calculated values of the bulk diffusion coefficient correspond reasonably well to the experimental data obtained for solid and molten states of titanium. Investigation of diffusion in the nanocrystalline titanium is of a significant importance because of its numerous technological applications. This paper aims to reduce the lack of data on diffusion in titanium and describe the processes occurring in bulk, at different interfaces and on surface of the crystalline titanium.

  3. Coarse grain model for coupled thermo-mechano-chemical processes and its application to pressure-induced endothermic chemical reactions

    International Nuclear Information System (INIS)

    Antillon, Edwin; Banlusan, Kiettipong; Strachan, Alejandro

    2014-01-01

    We extend a thermally accurate model for coarse grain dynamics (Strachan and Holian 2005 Phys. Rev. Lett. 94 014301) to enable the description of stress-induced chemical reactions in the degrees of freedom internal to the mesoparticles. Similar to the breathing sphere model, we introduce an additional variable that describes the internal state of the particles and whose dynamics is governed both by an internal potential energy function and by interparticle forces. The equations of motion of these new variables are derived from a Hamiltonian and the model exhibits two desired features: total energy conservation and Galilean invariance. We use a simple model material with pairwise interactions between particles and study pressure-induced chemical reactions induced by hydrostatic and uniaxial compression. These examples demonstrate the ability of the model to capture non-trivial processes including the interplay between mechanical, thermal and chemical processes of interest in many applications. (paper)

  4. Scaling behaviour of randomly alternating surface growth processes

    International Nuclear Information System (INIS)

    Raychaudhuri, Subhadip; Shapir, Yonathan

    2002-01-01

    The scaling properties of the roughness of surfaces grown by two different processes randomly alternating in time are addressed. The duration of each application of the two primary processes is assumed to be independently drawn from given distribution functions. We analytically address processes in which the two primary processes are linear and extend the conclusions to nonlinear processes as well. The growth scaling exponent of the average roughness with the number of applications is found to be determined by the long time tail of the distribution functions. For processes in which both mean application times are finite, the scaling behaviour follows that of the corresponding cyclical process in which the uniform application time of each primary process is given by its mean. If the distribution functions decay with a small enough power law for the mean application times to diverge, the growth exponent is found to depend continuously on this power-law exponent. In contrast, the roughness exponent does not depend on the timing of the applications. The analytical results are supported by numerical simulations of various pairs of primary processes and with different distribution functions. Self-affine surfaces grown by two randomly alternating processes are common in nature (e.g., due to randomly changing weather conditions) and in man-made devices such as rechargeable batteries

  5. The mathematical description of the process of drying the grain of millet in the device with active hydromechanical mode

    Directory of Open Access Journals (Sweden)

    S. T. Antipov

    2016-01-01

    Full Text Available The basis for the creation of new designs dryers laid the mathematical description of the test process, taking into account the method of loading and handling of the product in the machine, how to supply coolant or other type of energy supply, the theoretical performance, and structural (geometric component of the apparatus. To simulate the process of our work was considered of cylindrical dryers with active hydrodynamic regime and microwave energy supply, one feature of which is the loading of the product in a stream tangential coolant flow. The object of the study was chosen millet grain, because of the high biological value and high prevalence in the southern regions of the Russian Federation. On the basis of theoretical analysis, it was decided to divide the mathematical model into two conditional components: the study of heat and mass transfer study of aerodynamic component of the drying process. In this paper, we have been disclosed in detail is the second part of the process. The basis of this model were the equations of motion of millet grains by Newton's second law. The coolant in the framework of the proposed model is considered to be a continuous medium, highly compressible and has an internal viscosity, described by the Navier-Stokes equations. The initial conditions of the mathematical model were the following assumptions: the speed of the mechanical motion elements are equal to zero, the initial density of the air environment in all nodes is the equilibrium density of the air, the initial velocity of the air quality in all nodes is zero. The boundary conditions can be described as the constancy of the flow temperature and humidity, and its displacement is directly design constraints of the drying chamber. This model will be useful for professionals engaged in the problems of calculation and design of drying equipment.

  6. The effect of texture and grain size on improving the mechanical properties of Mg-Al-Zn alloys by friction stir processing.

    Science.gov (United States)

    Peng, Jinhua; Zhang, Zhen; Liu, Zhao; Li, Yaozu; Guo, Peng; Zhou, Wei; Wu, Yucheng

    2018-03-08

    Friction stir processing (FSP) was used to achieve grain refinement on Mg-Al-Zn alloys, which also brought in significant texture modification. The different micro-texture characteristics were found to cause irregular micro-hardness distribution in FSPed region. The effects of texture and grain size were investigated by comparative analyses with strongly textured rolling sheet. Grain refinement improved both strength and elongation in condition of a basal texture while such led to an increment in yield stress and a drop in elongation and ultimate stress when the basal texture was modified by FSP.

  7. Microstructure, microtexture and precipitation in the ultrafine-grained surface layer of an Al-Zn-Mg-Cu alloy processed by sliding friction treatment

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yanxia [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Yang, Yanqing, E-mail: yqyang@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Feng, Zongqiang [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Zhao, Guangming; Huang, Bin; Luo, Xian [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Zhang, Yusheng; Zhang, Wei [Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China)

    2017-01-15

    Precipitate redistribution and texture evolution are usually two concurrent aspects accompanying grain refinement induced by various surface treatment. However, the detailed precipitate redistribution characteristics and process, as well as crystallographic texture in the surface refined grain layer, are still far from full understanding. In this study, we focused on the microstructural and crystallographic features of the sliding friction treatment (SFT) induced surface deformation layer in a 7050 aluminum alloy. With the combination of transmission electron microscopy (TEM) and high angle angular dark field scanning TEM (HAADF-STEM) observations, a surface ultrafine grain (UFG) layer composed of both equiaxed and lamellar ultrafine grains and decorated by high density of coarse grain boundary precipitates (GBPs) were revealed. Further precession electron diffraction (PED) assisted orientation mapping unraveled that high angle grain boundaries rather than low angle grain boundaries are the most favorable nucleation sites for GBPs. The prominent precipitate redistribution can be divided into three successive and interrelated stages, i.e. the mechanically induced precipitate dissolution, solute diffusion and reprecipitation. The quantitative prediction based on pipe diffusion along dislocations and grain boundary diffusion proved the distribution feasibility of GBPs around UFGs. Based on PED and electron backscatter diffraction (EBSD) analyses, the crystallographic texture of the surface UFG layer was identified as a shear texture composed of major rotated cube texture (001) 〈110〉 and minor (111) 〈112〉, while that of the adjoining lamellar coarse grained matrix was pure brass. The SFT induced surface severe shear deformation is responsible for texture evolution. - Highlights: •The surface ultrafine grain layer in a 7050 aluminum alloy was focused. •Precipitate redistribution and texture evolution were discussed. •The quantitative prediction proved the

  8. Becoming Counselors through Growth and Learning: The Entry Transition Process

    Science.gov (United States)

    Wagner, Holly H.; Hill, Nicole R.

    2015-01-01

    This article explored counselor development within the entry transition into counselor education programs using 4 interviews and interpretive dialogues with 8 beginning counselors. Six categories resulted from the authors' grounded theory analysis: Anticipation, Evolving Identity, Growth and Learning, Coping, Choosing to Trust the Process, and…

  9. Significance of grain boundaries and stacking faults on hydrogen storage properties of Mg2Ni intermetallics processed by high-pressure torsion

    International Nuclear Information System (INIS)

    Hongo, Toshifumi; Edalati, Kaveh; Arita, Makoto; Matsuda, Junko; Akiba, Etsuo; Horita, Zenji

    2015-01-01

    Mg 2 Ni intermetallics are processed using three different routes to produce three different microstructural features: annealing at high temperature for coarse grain formation, severe plastic deformation through high-pressure torsion (HPT) for nanograin formation, and HPT processing followed by annealing for the introduction of stacking faults. It is found that both grain boundaries and stacking faults are significantly effective to activate the Mg 2 Ni intermetallics for hydrogen storage at 423 K (150 °C). The hydrogenation kinetics is also considerably enhanced by the introduction of large fractions of grain boundaries and stacking faults while the hydrogenation thermodynamics remains unchanged. This study shows that, similar to grain boundaries and cracks, stacking faults can act as quick pathways for the transportation of hydrogen in the hydrogen storage materials

  10. MEASUREMENT OF THE HIGH-FIELD Q-DROP IN A LARGE-GRAIN NIOBIUM CAVITY FOR DIFFERENT OXIDATION PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    Gianluigi Ciovati; Peter Kneisel; Alex Gurevich

    2008-01-23

    In this contribution, we present the results from a series of RF tests at 1.7 K and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm2) grain niobium which underwent various oxidation processes. After initial buffered chemical polishing, anodization, baking in pure oxygen atmosphere and baking in air up to 180 °C was applied with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system was used allowing to measure the local temperature rise of the cavity outer surface due to RF losses, which gives information about the losses location, their field dependence and space distribution on the RF surface. The results confirmed that the depth affected by baking is about 20 – 30 nm from the surface and showed that the Q-drop did not re-appear in a previously baked cavity by further baking at 120 °C in pure oxygen atmosphere or in air up to 180 °C. A statistic of the position of the “hot-spots” on the cavity surface showed that grain-boundaries are not the preferred location. An interesting correlation was found between the Q-drop onset, the quench field and the low-field energy gap, which supports the hypothesis of thermo-magnetic instability governing the Q-drop and the baking effect.

  11. MEASUREMENT OF THE HIGH-FIELD Q-DROP IN A LARGE-GRAIN NIOBIUM CAVITY FOR DIFFERENT OXIDATION PROCESSES

    International Nuclear Information System (INIS)

    Gianluigi Ciovati; Peter Kneisel; Alex Gurevich

    2008-01-01

    In this contribution, we present the results from a series of RF tests at 1.7 K and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm2) grain niobium which underwent various oxidation processes. After initial buffered chemical polishing, anodization, baking in pure oxygen atmosphere and baking in air up to 180 C was applied with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system was used allowing to measure the local temperature rise of the cavity outer surface due to RF losses, which gives information about the losses location, their field dependence and space distribution on the RF surface. The results confirmed that the depth affected by baking is about 20-30 nm from the surface and showed that the Q-drop did not re-appear in a previously baked cavity by further baking at 120 C in pure oxygen atmosphere or in air up to 180 C. A statistic of the position of the ''hot-spots'' on the cavity surface showed that grain-boundaries are not the preferred location. An interesting correlation was found between the Q-drop onset, the quench field and the low-field energy gap, which supports the hypothesis of thermomagnetic instability governing the Q-drop and the baking effect.

  12. Processing of fine-grained W materials without detrimental phases and their mechanical properties at 200-432 K

    Energy Technology Data Exchange (ETDEWEB)

    Ishijima, Y.; Kannari, S. [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Kurishita, H. [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan)], E-mail: kurishi@imr.tohoku.ac.jp; Hasegawa, M. [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Hiraoka, Y. [Department of Applied Physics, Okayama University of Science, 1-1 Ridai-cho, Okayama, Okayama 700-0005 (Japan); Takida, T.; Takebe, K. [A.L.M.T. TECH Inc., 2 Iwasekoshi-machi, Toyama, Toyama 931-8543 (Japan)

    2008-01-25

    Low-temperature ductility improvements of tungsten (W) materials with microstructures of fine grains and fine transition metal-carbide dispersoids require sufficient reductions for consolidates that are free from detrimental dispersoids of the W{sub 2}C phase. In this paper the cause of the occurrence of the detrimental W{sub 2}C phase is studied and an appropriate processing method for its prevention and nearly full densification of mechanically alloyed powder is shown. By applying the method W-0.3 wt%Ti-0.006 wt%C (W-0.3TiC-0.006C) specimens with a negligible amount of the W{sub 2}C phase and reductions up to 78% were prepared. It is found that W-0.3TiC-0.006C exhibits an appreciable ductility even at room temperature by three-point bend impact tests and static tensile tests, with the ductile-to-brittle transition temperature of around 260 K. The observed ductility is likely due to elongated, very thin grain structures of the material. For further ductility improvements, control of oxygen impurities to suppress decarburization during sintering and assure appropriate amounts of (Ti,W)C dispersoids is required.

  13. 3D primary grain shapes resulting from semi-solid metal processing

    CSIR Research Space (South Africa)

    Curle, Ulyate A

    2017-07-01

    Full Text Available ) size. Are these 2D globules also spherical in shape in 3D or are these 2D shapes remnants of the 3D shapes after sectioning along planes? An Al-Si-Mg alloy is semi-solid processed using a patented processing coil that induces contactless stirring while...

  14. Giant grains

    International Nuclear Information System (INIS)

    Leitch-Devlin, M.A.; Millar, T.J.; Williams, D.A.

    1976-01-01

    Infrared observations of the Orion nebula have been interpreted by Rowan-Robinson (1975) to imply the existence of 'giant' grains, radius approximately 10 -2 cm, throughout a volume about a parsec in diameter. Although Rowan-Robinson's model of the nebula has been criticized and the presence of such grains in Orion is disputed, the proposition is accepted, that they exist, and in this paper situations in which giant grains could arise are examined. It is found that, while a giant-grain component to the interstellar grain density may exist, it is difficult to understand how giant grains arise to the extent apparently required by the Orion nebula model. (Auth.)

  15. Integrated Process for Extraction of Wax as a Value-Added Co-Product and Improved Ethanol Production by Converting Both Starch and Cellulosic Components in Sorghum Grains

    Directory of Open Access Journals (Sweden)

    Nhuan P. Nghiem

    2018-02-01

    Full Text Available Grain sorghum is a potential feedstock for fuel ethanol production due to its high starch content, which is equivalent to that of corn, and has been successfully used in several commercial corn ethanol plants in the United States. Some sorghum grain varieties contain significant levels of surface wax, which may interact with enzymes and make them less efficient toward starch hydrolysis. On the other hand, wax can be recovered as a valuable co-product and as such may help improve the overall process economics. Sorghum grains also contain lignocellulosic materials in the hulls, which can be converted to additional ethanol. An integrated process was developed, consisting of the following steps: 1. Extraction of wax with boiling ethanol, which is the final product of the proposed process; 2. Pretreatment of the dewaxed grains with dilute sulfuric acid; 3. Mashing and fermenting of the pretreated grains to produce ethanol. During the fermentation, commercial cellulase was also added to release fermentable sugars from the hulls, which then were converted to additional ethanol. The advantages of the developed process were illustrated with the following results: (1 Wax extracted (determined by weight loss: ~0.3 wt % of total mass. (2 Final ethanol concentration at 25 wt % solid using raw grains: 86.1 g/L. (3 Final ethanol concentration at 25 wt % solid using dewaxed grains: 106.2 g/L (23.3% improvement. (4 Final ethanol concentration at 25 wt % solid using dewaxed and acid-treated grains (1 wt % H2SO4 plus cellulase (CTec2: 117.8 g/L (36.8% improvement.

  16. Processing of fine grained AISI 304L austenitic stainless steel by cold rolling and high-temperature short-term annealing

    Science.gov (United States)

    Naghizadeh, Meysam; Mirzadeh, Hamed

    2018-05-01

    An advanced thermomechanical process based on the formation and reversion of deformation-induced martensite was used to refine the grain size and enhance the hardness of an AISI 304L austenitic stainless steel. Both low and high reversion annealing temperatures and also the repetition of the whole thermomechanical cycle were considered. While a microstructure with average austenite grain size of a few micrometers was achieved based on cold rolling and high-temperature short-term annealing, an extreme grain refinement up to submicrometer regime was obtained by cold rolling followed by low-temperature long-term annealing. However, the required annealing time was found to be much longer, which negates its appropriateness for industrial production. While a magnificent grain refinement was achieved by one pass of the high-temperature thermomechanical process, the reduction in grain size was negligible by the repetition of the whole cycle. It was found that the hardness of the thermomechanically processed material is much higher than that of the as-received material. The results of the present work were shown to be compatible with the general trend of grain size dependence of hardness for AISI 304L stainless steel based on the Hall-Petch relationship. The results were also discussed based on the X-ray evaluation of dislocation density by modified Williamson-Hall plots.

  17. Modelisation and numerical simulation for bulk crystal growth processes

    International Nuclear Information System (INIS)

    Duffar, F.; Dusserre, P.; Barat, C.; Nabot, J.P.

    1993-01-01

    The aim of this work is to study the relevance of numerical simulation for improving the process control in the field of crystal growth. This investigation focused on the growth of semiconductor and halide crystals by the Bridgman solidification technique, the principle of which is to cool a seeded feed material contained in a crucible, either by pulling the crucible or by decreasing the temperature in the furnace. Calculations are performed with the finite element method, and for comparison, experiments are carried out on Bridgman pulling machines operating either in a laboratory or in industrial plants. Calculations and experimental data have shown a good agreement and a satisfactory reliability

  18. Rare behavior of growth processes via umbrella sampling of trajectories

    Science.gov (United States)

    Klymko, Katherine; Geissler, Phillip L.; Garrahan, Juan P.; Whitelam, Stephen

    2018-03-01

    We compute probability distributions of trajectory observables for reversible and irreversible growth processes. These results reveal a correspondence between reversible and irreversible processes, at particular points in parameter space, in terms of their typical and atypical trajectories. Thus key features of growth processes can be insensitive to the precise form of the rate constants used to generate them, recalling the insensitivity to microscopic details of certain equilibrium behavior. We obtained these results using a sampling method, inspired by the "s -ensemble" large-deviation formalism, that amounts to umbrella sampling in trajectory space. The method is a simple variant of existing approaches, and applies to ensembles of trajectories controlled by the total number of events. It can be used to determine large-deviation rate functions for trajectory observables in or out of equilibrium.

  19. Cohesive zone model for intergranular slow crack growth in ceramics: influence of the process and the microstructure

    International Nuclear Information System (INIS)

    Romero de la Osa, M; Olagnon, C; Chevalier, J; Estevez, R; Tallaron, C

    2011-01-01

    Ceramic polycrystals are prone to slow crack growth (SCG) which is stress and environmentally assisted, similarly to observations reported for silica glasses. The kinetics of fracture are known to be dependent on the load level, the temperature and the relative humidity. In addition, evidence is available on the influence of the microstructure on the SCG rate with an increase in the crack velocity with decreasing the grain size. Crack propagation takes place beyond a load threshold, which is grain size dependent. We present a cohesive zone model for the intergranular failure process. The methodology accounts for an intrinsic opening that governs the length of the cohesive zone and allows the investigation of grain size effects. A rate and temperature-dependent cohesive model is proposed (Romero de la Osa M, Estevez R et al 2009 J. Mech. Adv. Mater. Struct. 16 623–31) to mimic the reaction–rupture mechanism. The formulation is inspired by Michalske and Freiman's picture (Michalske and Freiman 1983 J. Am. Ceram. Soc. 66 284–8) together with a recent study by Zhu et al (2005 J. Mech. Phys. Solids 53 1597–623) of the reaction–rupture mechanism. The present investigation extends a previous work (Romero de la Osa et al 2009 Int. J. Fracture 158 157–67) in which the problem is formulated. Here, we explore the influence of the microstructure in terms of grain size, their elastic properties and residual thermal stresses originating from the cooling from the sintering temperature down to ambient conditions. Their influence on SCG for static loadings is reported and the predictions compared with experimental trends. We show that the initial stress state is responsible for the grain size dependence reported experimentally for SCG. Furthermore, the account for the initial stresses enables the prediction of a load threshold below which no crack growth is observed: a crack arrest takes place when the crack path meets a region in compression

  20. Effects of Nano-Zinc oxide and Seed Inoculation by Plant Growth Promoting Rhizobacteria (PGPR on Yield, Yield Components and Grain Filling Period of Soybean (Glycine max L.

    Directory of Open Access Journals (Sweden)

    R. Seyed Sharifi

    2016-02-01

    promoting rhizobacteria application on yield, yield components and grain filling period of soybean. Materials and Methods In order to study the effects of Nano-Zinc oxide and seed inoculation with Brady rhizobium and plant growth promoting rhizobacteria on yield and some agronomic characteristics of soybean, a factorial experiment based on randomized complete block design with three replications was conducted in 2013 at the research farm of the Islamic Azad University, Ardabil Branch. Factors were included foliar application of Nano-Zinc oxide at four levels (Zero as control, 0.3, 0.6 and 0.9 g l-1 and seed inoculation with Brady rhizobium and plant growth promoting rhizobacteria at five levels (without inoculation as control, seed inoculation with Brady rhizobium japanicum, seed inoculation with Brady rhizobium japanicum+Azosprillum lipoferum strain OF, seed inoculation with Brady rhizobium japanicum+Psedomonas putida, seed inoculation with Brady rhizobium japanicum+ Azosprillum lipoferum strain OF+ Psedomonas putida. Results and Discussion The results of growth indices showed that the maximum total dry matter (530 g m-2, crop growth rate (9.48 g.m-2.day-1 and relative growth rate (0.1 g.g-1.day-1 were obtained at foliar application of 0.9 g l-1 Nano-Zinc oxide×seed inoculation with rhizobium+Azosprillum+ Psedomonas and the least of these indices were obtained without of foliar application Nano-Zinc oxide × seed inoculation. The results showed that plant height, the number of nodules per plant, the number of pod per plant, grain yield and grain 100 weight were significantly affected by Nano-Zinc oxide, seed inoculation and interaction of Nano-Zinc oxide×seed inoculation. Maximum of plant height, grain 100 weight, the number of nodules per plant and grain yield were obtained at foliar application of 0.9 g l-1 of Nano-Zinc oxide×seed inoculation with rhizobium and PGPR. Dry weight of nodules per plant, the number of pod per plant and the number of grains per plant

  1. Effect of nutrition, vitamin, grains, and temperature on the mycelium growth and antioxidant capacity of Cordyceps militaris (strains AG-1 and PSJ-1

    Directory of Open Access Journals (Sweden)

    Hung-Ngoc Dang

    2018-04-01

    Full Text Available Effects of subculture conditions on the mycelium growth and antioxidant capacity assessment of Cordyceps militaris trains AG-1 and PSJ-1 were carried out in laboratory during the autumn-winter season of 2015. Different temperature regimes and nutrition, vitamins levels, grain in substrate were evaluated for optimization on mycelium growth. The results showed that two strains AG-1 and PSJ-1 can grow the maximum mycelium radial at the temperature of 24 °C. The mycelium growth was improved by carbon sources such as glucose, dextrose, fructose, and maltose at 30 g/L concentration. Whereas glucose achieved the highest value of mycelium colony diameter in strains AG-1 and PSJ-1. Vitamins B1 concentrations at 0.03 g/L also gave the great values in mycelium colony diameter of both strains AG-1 and PSJ-1. The studies depicted that a substrate mixed with various grains sources (brown rice, white rice, and wheat, black glutinous rice Vietnam, and corn cultured at 24 °C, for 12 days supported maximum mycelia growth of the two strains AG-1 and PSJ-1 of C. militaris. The effect of liquid culture medium (MYPS and PD with mycelium on the anti-oxidation capacity was assessed. The results showed that the increasing of DPPH radical scavenging capacity with the extract concentration exist a proportional relation and Fe2+-chelating capacity as well. The cultured Cordyceps mycelium of two strains AG-1 and PSJ-1had the equally strong antioxidant capacity. Keywords: Cordyceps militaris, Mycelium growth, Nutritional condition, Temperature, Vitamins, Anti-oxidation activity

  2. Prospecting plant growth promoting bacteria and cyanobacteria as options for enrichment of macro- and micronutrients in grains in rice–wheat cropping sequence

    Directory of Open Access Journals (Sweden)

    Anuj Rana

    2015-12-01

    Full Text Available The influence of plant growth promoting bacteria (PGPB and cyanobacteria, alone and in combination, was investigated on micronutrient enrichment and yield in rice–wheat sequence, over a period of two years. Analysis of variance (ANOVA in both crops indicated significant differences in soil dehydrogenase activity and micronutrient enrichment in grains (Fe, Zn in rice, and Cu, Mn in wheat. The combined inoculation of Anabaena oscillarioides CR3, Brevundimonas diminuta PR7, and Ochrobactrum anthropi PR10 (T6 significantly increased nitrogen, phosphorus, and potassium (NPK content and improved rice yield by 21.2%, as compared to the application of recommended dose of NPK fertilizers (T2. The treatment T5 (Providencia sp. PR3 + B. diminuta PR7 + O. anthropi PR10 recorded an enhancement of 13–16% in Fe, Zn, Cu, and Mn concentrations, respectively, in rice grains. In wheat, Providencia sp. PW5 (T6 recorded the highest yield (5.23 Mg ha−1 and significantly higher enrichment of Fe and Cu (44–45% in the grains. This study highlighted the promise of combinations of cyanobacteria/bacteria and their synergistic action in biofortification and providing savings of 40–60 kg N ha−1. Future focus needs to be towards integrating such promising environment-friendly and environmentally sustainable options in nutrient management strategies for this cropping sequence.

  3. Retailing of Processed Dairy and Grain Products in Mali: Evidence from a City Retail Outlet Inventory

    Directory of Open Access Journals (Sweden)

    Veronique Theriault

    2018-03-01

    Full Text Available As in many sub-Saharan African countries, Mali is experiencing an unprecedented rate of urbanization and, with it, changes to its agri-food system. As more people live in urban areas, the demand for processed foods has been increasing rapidly. These changes have important implications for food and nutrition security. Yet, little is known about the scale and scope of the retailing of processed foods. To better understand this segment, we conducted a city retail outlet inventory of processed dairy and cereal foods in 2016. The main findings are that: (1 food availability is greater in the capital, high-income neighborhoods, and supermarkets; (2 there is a high prevalence of imported foods; (3 added sugar and vegetable fats are listed as a top-three ingredient in a quarter of processed products, highlighting issues related to healthfulness; (4 price premiums are paid for products that are imported from Europe, use improved packaging, and are retailed in supermarkets. Taken together, our findings indicate that the transformation in the Malian agri-food system is still at an early stage. The growing demand for processed foods presents economic opportunities for Malian farmers and processors, especially if they can improve product quality, packaging, and distribution.

  4. Grain size and microhardness evolution during annealing of a magnesium alloy processed by high-pressure torsion

    Directory of Open Access Journals (Sweden)

    Livia Raquel C. Malheiros

    2015-01-01

    Full Text Available High-pressure torsion (HPT was used to impose severe plastic deformation on a magnesium alloy AZ31. The material was processed for 0.5, 1, 2, 3, 5 and 7 turns at room temperature under a pressure of 6.0 GPa. Samples were annealed for 1800 s at temperatures of 373 K, 423 K, 473 K, 573 K and 673 K. Microhardness tests and metallography were used to determine the evolution of strength and grain size as a function of the annealing temperature. The results show that recrystallization takes place at temperatures higher than 423 K. The annealing behavior is independent of the number of turns in HPT.

  5. High moisture airtight storage of barley and triticale: Effect of moisture level and grain processing on nitrogen and phosphorus solubility

    DEFF Research Database (Denmark)

    Ton Nu, Mai Anh; Blaabjerg, Karoline; Labouriau, Rodrigo

    2015-01-01

    The aim of this study was to evaluate the effect of storage time, grain processing (whole vs. rolled) and the combination of phytase, xylanase, β-glucanase and protease on nitrogen (N) and phosphorus (P) solubility during high moisture airtight (HMA) storage of barley and triticale at various...... moisture levels (20, 23, 26 and 29% moisture) and to compare HMA storage of cereals with dry storage for 49 days. Dry stored barley and triticale (10 and 13% moisture, respectively) were kept in 10 L plastic buckets for 0 and 49 days. HMA stored cereals were kept in airtight bags (400 g per bag) at 15 °C......) in HMA storage at 29% moisture to a greater extent compared with dry storage (P levels increased P solubility (rolled barley, whole and rolled triticale) and N solubility (whole and rolled triticale) linearly and decreased Phytate P:Total P (rolled barley) linearly...

  6. Insight of Transmembrane Processes of Self-Assembling Nanotubes Based on a Cyclic Peptide Using Coarse Grained Molecular Dynamics Simulation.

    Science.gov (United States)

    Fu, Yankai; Yan, Tingxuan; Xu, Xia

    2017-09-28

    Transmembrane self-assembling cyclic peptide (SCP) nanotubes are promising candidates for delivering specific molecules through cell membranes. The detailed mechanisms behind the transmembrane processes, as well as stabilization factors of transmembrane structures, are difficult to elucidate through experiments. In this study, the effects of peptide sequence and oligomeric state on the transmembrane capabilities of SCP nanotubes and the perturbation of embedded SCP nanotubes acting on the membrane were investigated based on coarse grained molecular dynamics simulation. The simulation results reveal that hydrophilic SCP oligomers result in the elevation of the energy barrier while the oligomerization of hydrophobic SCPs causes the reduction of the energy barrier, further leading to membrane insertion. Once SCP nanotubes are embedded, membrane properties such as density, thickness, ordering state and lateral mobility are adjusted along the radial direction. This study provides insight into the transmembrane strategy of SCP nanotubes and sheds light on designing novel transport systems.

  7. Influence of porosity on densification and grain growth kinetics of Ce0.9Gd0.1O1.95 tape

    DEFF Research Database (Denmark)

    Ni, De Wei; Esposito, Vincenzo; Foghmoes, Søren Preben Vagn

    porous layer allowing gas flow is necessary in catalytic and in gas purification devices. During the sintering with shrinkage, the total solid volume is maintained to be a constant value but the shape and size of each particle change with the formation of grain boundaries. This change in solid particles...... is accompanied by the change of shape, size and fraction of pores in a given volume. Therefore, porosity can be treated as an extra phase during sintering study. In this work, we presented the densification and grain growth behaviour of Ce0.9Gd0.1O1.95 tape cast layers with different percentage of porosity....... The emphasis was put on the effect of porosity on densification and grain growth kinetics. Derived from the sintering constitutive laws, the densification and grain growth kinetics were experimentally characterized and analyzed. Furthermore, the activation energies for viscous flow were determined from master...

  8. Processing ultrafine-grained Aluminum alloy using Multi-ECAP-Conform technique

    International Nuclear Information System (INIS)

    Fakhretdinova, Elvira; Raab, Georgy; Valiev, Ruslan; Ryzhikov, Oleg

    2014-01-01

    The stress-strained state (SSS), contact and force parameters of a new SPD technique – Multi-ECAP-Conform – have been studied. The new technique ensures a high level of accumulated strain □=4...5 per one processing cycle. Physical and computer modeling by finite element method in Deform-3D software was applied to evaluate the parameters. It is shown that the results of physical and computer modeling correlate with each other. Equipment has been upgraded, and experimental samples of Al-Mg-Si system alloy have been processed

  9. Densification and grain growth during sintering of porous Ce0.9Gd0.1O1.95tape cast layers: A comprehensive study on heuristic methods

    DEFF Research Database (Denmark)

    Ni, De Wei; Schmidt, Cristine Grings; Teocoli, Francesca

    2013-01-01

    The sintering behavior of porous Ce0.9Gd0.1O1.95(CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine the domin...... and grain boundary mobility in the porous body was estimated around 10−18–10−16m3N−1s−1 at the investigated temperature range.© 2013 Elsevier Ltd. All rights reserved.......The sintering behavior of porous Ce0.9Gd0.1O1.95(CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine...... the dominant sintering mechanisms and kinetics, both in isothermal and at constant heating rate (iso-rate) conditions. Densification of porous CGO10 tape is thermally activated with typical activation energy which was estimated around 440–470 kJ mol−1. Grain growth showed similar thermal activation energy...

  10. Structure and grain coarsening during the processing of engineering ceramics. Ph.D. Thesis - Leeds Univ., United Kingdom

    Science.gov (United States)

    Shaw, Nancy J.

    1987-01-01

    Studies have been made of three ceramic systems (Al2O3, Y2O3/MgO, and SiC/C/B), both to explore a surface area/density diagram approach to examining the coarsening processes during sintering and to explore an alternative coarsening parameter, i.e., the grain boundary surface area (raising it at a given value of the density) and not the pore surface area; therefore, pinning of the grain boundaries by solid-solution drag is the only function evidenced by these results. The importance of such pinning even at densities as low as 75% of theoretical is linked to the existence of microstructural inhomogeneities. The early stages of sintering of Y2O3 powder have been examined using two techniques, BET surface area analysis and transmission electron microscopy. Each has given some insight into the process occurring and, used together, have provided some indication of the effect of MgO on coarsening during sintering. Attempts to further elucidate effects of MgO on the coarsening behavior of Y2O3 by the surface area/density diagram approach were unsuccessful due to masking effects of contaminating reactions during sintering and/or thermal etching. The behavior of the undoped SiC which only coarsens can be clearly distinguished by the surface area/density diagram from that of SiC/C/B which also concurrently densifies. Little additional information was obtainable by this method due to unfavorable sample etching characteristics. The advantages, disadvantages, and difficulties of application of these techniques to the study of coarsening during sintering are discussed.

  11. SPITZER survey of dust grain processing in stable discs around binary post-AGB stars

    NARCIS (Netherlands)

    Gielen, C.; van Winckel, H.; Min, M.; Waters, L.B.F.M.; Lloyd Evans, T.

    2008-01-01

    Aims. We investigate the mineralogy and dust processing in the circumbinary discs of binary post-AGB stars using high-resolution TIMMI2 and SPITZER infrared spectra. Methods: We perform a full spectral fitting to the infrared spectra using the most recent opacities of amorphous and crystalline dust

  12. Influence of processing conditions on apparent viscosity and system parameters during extrusion of distiller's dried grains-based snacks.

    Science.gov (United States)

    Singha, Poonam; Muthukumarappan, Kasiviswanathan; Krishnan, Padmanaban

    2018-01-01

    A combination of different levels of distillers dried grains processed for food application (FDDG), garbanzo flour and corn grits were chosen as a source of high-protein and high-fiber extruded snacks. A four-factor central composite rotatable design was adopted to study the effect of FDDG level, moisture content of blends, extrusion temperature, and screw speed on the apparent viscosity, mass flow rate or MFR, torque, and specific mechanical energy or SME during the extrusion process. With increase in the extrusion temperature from 100 to 140°C, apparent viscosity, specific mechanical energy, and torque value decreased. Increase in FDDG level resulted in increase in apparent viscosity, SME and torque. FDDG had no significant effect (p > .5) on mass flow rate. SME also increased with increase in the screw speed which could be due to the higher shear rates at higher screw speeds. Screw speed and moisture content had significant negative effect ( p  extruder and the system parameters were affected by the processing conditions. This study will be useful for control of extrusion process of blends containing these ingredients for the development of high-protein high-fiber extruded snacks.

  13. Modeling the hydration process of bean grains coated with carnauba wax

    Directory of Open Access Journals (Sweden)

    Aline Almeida da Paixão

    2017-08-01

    Full Text Available Edible waxes are widely used to maintain foodstuff until they are consumed. However, some products may be subjected to industrial procedures, such as hydration, prior to their consumption. Hydration of a material is a complex process, which aims to reconstitute the original characteristics of a product when in contact with a liquid phase. An important agricultural product that requires this procedure is beans. Thus, the purpose of this work is to study the hydration process of beans (cultivar BRSMG Majestoso in different temperatures and concentrations of carnauba wax, which is applied on the product surface. Beans with initial moisture content of 0.2015, 0.1972 and 0.1745 (d.b. corresponding to treatments 0 (witness, 1 (wax diluted in water in the ratio 1:1, and 2 (carnauba wax, without dilution were used. Later, these samples were imbibed in distilled water at temperatures of 20, 30 and 40 ºC, for 15 h. The temperature and the carnauba wax influenced the water absorption rate. The Peleg model described satisfactory experimental data and the Mitscherlich model presented biased residual distribution. The constants C1 and C2 of the Peleg model exhibited opposite behaviors with increasing temperatures in the hydration process.

  14. Growth and physical properties of top-seeded infiltration growth processed large grain (Gd, Dy)BCO bulk superconductors

    Czech Academy of Sciences Publication Activity Database

    Naik, S.P.K.; Muralidhar, M.; Jirsa, Miloš; Murakami, M.

    2017-01-01

    Roč. 122, č. 19 (2017), s. 1-10, č. článku 193902. ISSN 0021-8979 Institutional support: RVO:68378271 Keywords : silver sheathed superconducting tapes * thick REBaCuO films * electromagnetic properties * solid phase -liquid phase reaction Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.068, year: 2016

  15. Strengthening mechanisms in ultrafine grained Al-Mg-Si alloy processed by hydrostatic extrusion – Influence of ageing temperature

    Energy Technology Data Exchange (ETDEWEB)

    Chrominski, Witold, E-mail: wichr@inmat.pw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland); Wenner, Sigurd [Department of Physics, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway); Marioara, Calin D. [SINTEF Materials and Chemistry, 7465 Trondheim (Norway); Holmestad, Randi [Department of Physics, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway); Lewandowska, Malgorzata [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

    2016-07-04

    Microstructure of hydrostatically extruded Al-Mg-Si alloy was studied by the combination of electron backscattered diffraction and transmission electron microscopy. Three different grain types which feature various defects arrangements were detected. Post deformation ageing at two temperatures caused different precipitation phenomena which were strongly dependent on type of grain boundaries in the considered grain types. Thus, a combination of plastic deformation and ageing resulted in a material with complex microstructure. Based on transmission electron microscopy observations, contributions of different strengthening mechanisms were estimated and compared to experimental results. A good agreement between obtained data points confirmed that depending on grain type, different strengthening mechanisms are operative and the overall strength is a sum of hardening given by each of them. Ageing of ultrafine grain structure results in efficient precipitation strengthening. On the other hand ageing causes annihilation of low and high angle grains boundaries in which leads to softening of investigated material. This effect cannot be compensated by precipitation hardening.

  16. In vitro and in vivo studies of ultrafine-grain Ti as dental implant material processed by ECAP

    Energy Technology Data Exchange (ETDEWEB)

    An, Baili; Li, Zhirui; Diao, Xiaoou [State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); National Clinical Research Center for Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); Shannxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); Xin, Haitao, E-mail: xhthmj@fmmu.edu.cn [State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); National Clinical Research Center for Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); Shannxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); Zhang, Qiang; Jia, Xiaorui; Wu, Yulu; Li, Kai [State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); National Clinical Research Center for Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); Shannxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi' an 710032 (China); Guo, Yazhou [School of Aeronautics, Northwestern Polytechnical University, Xi' an 710032 (China)

    2016-10-01

    The aim of this study was to investigate the surface characterization of ultrafine-grain pure titanium (UFG-Ti) after sandblasting and acid-etching (SLA) and to evaluate its biocompatibility as dental implant material in vitro and in vivo. UFG-Ti was produced by equal channel angular pressing (ECAP) using commercially pure titanium (CP-Ti). Microstructure and yield strength were investigated. The morphology, wettability and roughness of the specimens were analyzed after they were modified by SLA. MC3T3-E1 osteoblasts were seeded onto the specimens to evaluate its biocompatibility in vitro. For the in vivo study, UFG-Ti implants after SLA were embedded into the femurs of New Zealand rabbits. Osseointegration was investigated though micro-CT analysis, histological assessment and pull-out test. The control group was CP-Ti. UFG-Ti with enhanced mechanical properties was produced by four passes of ECAP in B{sub C} route at room temperature. After SLA modification, the hierarchical porous structure on its surface exhibited excellent wettability. The adhesion, proliferation and viability of cells cultured on the UFG-Ti were superior to that of CP-Ti. In the in vivo study, favorable osseointegration occurred between the implant and bone in CP and UFG-Ti groups. The combination intensity of UF- Ti with bone was higher according to the pull-out test. This study supports the claim that UFG-Ti has grain refinement with outstanding mechanical properties and, with its excellent biocompatibility, has potential for use as dental implant material. - Highlights: • Yield strength and Vickers hardness of Ti are improved significantly after it is grain-refined by ECAP process. • The hierarchical micro-porous structure with superior wettability could be formed on the surface of ECAP Ti after SLA. • The results in vitro exhibited excellent cell biocompatibility of UFG-Ti after sandblasting and acid-etching. • The osseointegration between UFG-Ti implant and surrounding bone could

  17. In vitro and in vivo studies of ultrafine-grain Ti as dental implant material processed by ECAP

    International Nuclear Information System (INIS)

    An, Baili; Li, Zhirui; Diao, Xiaoou; Xin, Haitao; Zhang, Qiang; Jia, Xiaorui; Wu, Yulu; Li, Kai; Guo, Yazhou

    2016-01-01

    The aim of this study was to investigate the surface characterization of ultrafine-grain pure titanium (UFG-Ti) after sandblasting and acid-etching (SLA) and to evaluate its biocompatibility as dental implant material in vitro and in vivo. UFG-Ti was produced by equal channel angular pressing (ECAP) using commercially pure titanium (CP-Ti). Microstructure and yield strength were investigated. The morphology, wettability and roughness of the specimens were analyzed after they were modified by SLA. MC3T3-E1 osteoblasts were seeded onto the specimens to evaluate its biocompatibility in vitro. For the in vivo study, UFG-Ti implants after SLA were embedded into the femurs of New Zealand rabbits. Osseointegration was investigated though micro-CT analysis, histological assessment and pull-out test. The control group was CP-Ti. UFG-Ti with enhanced mechanical properties was produced by four passes of ECAP in B_C route at room temperature. After SLA modification, the hierarchical porous structure on its surface exhibited excellent wettability. The adhesion, proliferation and viability of cells cultured on the UFG-Ti were superior to that of CP-Ti. In the in vivo study, favorable osseointegration occurred between the implant and bone in CP and UFG-Ti groups. The combination intensity of UF- Ti with bone was higher according to the pull-out test. This study supports the claim that UFG-Ti has grain refinement with outstanding mechanical properties and, with its excellent biocompatibility, has potential for use as dental implant material. - Highlights: • Yield strength and Vickers hardness of Ti are improved significantly after it is grain-refined by ECAP process. • The hierarchical micro-porous structure with superior wettability could be formed on the surface of ECAP Ti after SLA. • The results in vitro exhibited excellent cell biocompatibility of UFG-Ti after sandblasting and acid-etching. • The osseointegration between UFG-Ti implant and surrounding bone could be

  18. Formation of dust grains with impurities in red giant winds

    Science.gov (United States)

    Dominik, Carsten

    1994-01-01

    Among the several proposed carriers of diffuse interstellar bands (DIB's) are impurities in small dust grains, especially in iron oxide grains (Huffman 1977) and silicate grains (Huffman 1970). Most promising are single ion impurities since they can reproduce the observed band widths (Whittet 1992). These oxygen