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Sample records for rietveld refinement method

  1. Synthesis and refinement of ferroelectric ceramic BaBi4Ti4O15 (BBT) using Rietveld Methods

    International Nuclear Information System (INIS)

    Silva, P.M.O.; Sales, A.J.M.; Carneiro, J.C.S.; Sancho, E.O.; Sales, J.C.; Sombra, A.S.B.

    2012-01-01

    The lead zirconate titanate (PZT) has potential application in nonvolatile ferroelectric memory and capacitors, however this material is linked to environmental pollution. In order to remedy this problem, we propose the synthesis of the compound, BaBi 4 TI 4 O 15 (BBT) because of similarity to PZT. The phase of the BBT has been prepared by the method of solid state. Reagents (BaCO 3 , Bi 2 O 3 and TiO 2 ) were ground for 6 hours at 360 rpm in a planetary ball mill and suffered high energy heat treatment for 2 hours at temperatures of 850, 900, 950 and 1000 ° C. The calcined powder was characterized by X-ray diffraction (XRD) and refined by the program DBWSTools 2.3 Beta based on the Rietveld method. The results obtained confirmed the refinement of the single-phase with tetragonal structure BaBi 4 TI 4 O 15 for all samples. The sample calcined at 950 °C presented the best densification (7.508 g/cm³). (author)

  2. Refinement of the crystal structure of lead titanate with different degrees of imperfection of cationic and anionic sublattices by the Rietveld method

    International Nuclear Information System (INIS)

    Akimov, A.I.; Savchuk, G.K.; Rubtsov, V.A.; Letko, A.K.

    2003-01-01

    The parameters of the crystal structure of lead titanate with different degrees of imperfection of the anionic and cationic sublattices are refined by the Rietveld method. The experiments are carried out on a DRON-4 diffractometer (CuK α radiation; 20 deg. d 5.0-6.0%

  3. Refinement by Rietveld method of a rolled sheet Al-Mg-Si 6063 alloy with preferential orientation

    International Nuclear Information System (INIS)

    Carrio, J.A.G.; Hattori, C.S.; Miranda, L.F.; Domingues Junior, N.I.; Lima, N.B.; Couto, A.A.; Aguiar, A.A.

    2010-01-01

    The Rietveld refinement of a sample with preferential orientation was accomplished using data of X ray diffraction of a rolled 6063 aluminum alloy. The refinement of the preferential orientation by spherical harmonic was accomplished using a symmetry of sample mmm (rolling) until the order of 8 and was compared with experimental pole figures. The four pole figures presented indicate a sharp texture of the planes (111), (200), (220) and (311). The calculated pole figures obtained from the refinement of the X ray diffraction spectrum can incur in mistakes of preferential orientation. This happens because the measure is restricted to the planes parallel to the surface without inference to the symmetry of the sample. (author)

  4. Mathematical aspects of Rietveld refinement and crystal structure ...

    Indian Academy of Sciences (India)

    Administrator

    The core mathematics, goodness-of-fit parameters of Rietveld refinement technique is introduced for structural ... transducers in medical and solar applications (Obmann ..... Prince 1985 in Structure and statistics in crystallography (ed.).

  5. Influence of the milling time in the microstructural parameters of TA2O5-Al powder refined by Rietveld method

    International Nuclear Information System (INIS)

    Brito, R.A.; Mendes, M.W.D.; Alves Junior, C.; Costa, F.A. da; Gomes, U.U.

    2009-01-01

    Mechanical alloying (MA) is a solid-state powder processing technique involving repeated welding, fracturing, and re-welding of powder particles in a high energy mill. This process is used for producing of fine powders containing unique microstructures. The process starts with mixing of the powders in the desired proportion. Then, the mixture is milled using the established time in the high-energy mill. The powder particles are submitted to repeated cycles of cold working and fracture, and the final product correspond to a composite powder, containing characteristics different of the initial constituents. Ta 2 O 5 -Al powders were milled in a planetary ball mill for different times in order to evaluate the influence of the milling time in their microstructural parameters like crystallite size and micro deformation. The microstructural parameters were obtained by the Rietveld Method. The results showed that the microstructural parameters were influenced by the increase of the milling time. (author)

  6. Measurements of Residual Stresses In Cold-Rolled 304 Stainless Steel Plates Using X-Ray Diffraction with Rietveld Refinement Method

    International Nuclear Information System (INIS)

    Parikin; Killen, P; Rafterry, A.

    2009-01-01

    The determination of the residual stresses using X-ray powder diffraction in a series of cold-rolled 304 stainless steel plates, deforming 0, 34, 84, 152, 158, 175 and 196 % reduction in thickness has been carried out. The diffraction data were analyzed using the Rietveld structure refinement method. The analysis shows that for all specimens, the martensite particles are closely in compression and the austenite matrix is in tension. Both the martensite and austenite, for a sample reducing 34% in thickness (containing of about 1% martensite phase) the average lattice strains are anisotropic and decrease approximately exponential with an increase in the corresponding percent reduction (essentially phase content). It is shown that this feature can be qualitatively understood by taking into consideration the thermal expansion mismatch between the martensite and austenite grains. Also, for all cold-rolled stainless steel specimens, the diffraction peaks are broader than the unrolled one (instrumental resolution), indicating that the strains in these specimens are inhomogeneous. From an analysis of the refined peak shape parameters, the average root-mean square strain, which describes the distribution of the inhomogeneous strain field, was predicted. The average residual stresses in cold-rolled 304 stainless steel plates showed a combination effect of hydrostatic stresses of the martensite particles and the austenite matrix. (author)

  7. Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources

    International Nuclear Information System (INIS)

    David, W.I.F.; Jorgensen, J.D.

    1990-10-01

    The recent development of accelerator-based pulsed neutron sources has led to the widespread use of the time-of-flight technique for neutron powder diffraction. The properties of the pulsed source make possible unusually high resolution over a wide range of d spacings, high count rates, and the ability to collect complete data at fixed scattering angles. The peak shape and other instrument characteristics can be accurately modelled, which make Rietveld refinement possible for complex structures. In this paper we briefly review the development of the Rietveld method for time-of-flight diffraction data from pulsed neutron sources and discuss the latest developments in high resolution instrumentation and advanced Rietveld analysis methods. 50 refs., 12 figs., 14 tabs

  8. Possibilities and limitations of parametric Rietveld refinement on high pressure data. The case study of LaFeO3

    International Nuclear Information System (INIS)

    Etter, Martin; Mueller, Melanie; Dinnebier, Robert E.; Hanfland, Michael

    2014-01-01

    Parametric Rietveld refinement is a powerful technique to apply directly physical or empirical equations to the refinement of in situ powder diffraction data. In order to investigate the possibilities and limitations of parametric Rietveld refinements for high pressure data four competitive crystallographic approaches were used to carry out a full structural investigation of the orthoferrite LaFeO 3 (Pbnm at ambient conditions) under high pressure up to 47 GPa. Approach A with traditional Rietveld refinement using atomic coordinates, Approach B where the Rietveld refinement was done by using the rigid body method, Approach C where symmetry modes were used and Approach D where the newly developed method of the rotational symmetry mode description for a rigid body was used. For all approaches sequential as well as parametric refinements were carried out, confirming a second order phase transition of LaFeO 3 to a higher symmetric phase (space group Ibmm) at around 21.1?GPa and an isostructural first order phase transition at around 38 GPa. Limitations due to non-hydrostatic conditions as well as the possibilities of a direct modeling of phase transitions with parametric Rietveld refinement are discussed in detail. (orig.)

  9. Characterization of barium titanate powder doped with sodium and potassium ions by using Rietveld refining

    International Nuclear Information System (INIS)

    Andrade, M.C.; Assis, J.T.; Pereira, F.R.

    2009-01-01

    A solid-reaction synthesis of doped barium titanate was done by employing barium carbonates, sodium, potassium and titanium oxides with classic procedures. Rietveld refining of X ray diffraction data of perovskite samples with tetragonal symmetry was applying and show good agreement. Besides, the treatment performed from 600 deg C produces nanocrystals of barium titanate with average size of 33 nm. The presence of endothermic peaks related to BaTiO 3 formation at relatively low temperatures was determined by thermal analysis. A pseudo-Voigt Thompson-Cox-Hastings function was used to fit the standard samples of barium titanate. The Rietveld method has showed be efficient to detect the influences of temperature and doping on barium titanate microstructures. (author)

  10. Profex: a graphical user interface for the Rietveld refinement program BGMN

    OpenAIRE

    Doebelin, Nicola; Kleeberg, Reinhard

    2015-01-01

    Profex is a graphical user interface for the Rietveld refinement program BGMN. Its interface focuses on preserving BGMN’s powerful and flexible scripting features by giving direct access to BGMN input files. Very efficient workflows for single or batch refinements are achieved by managing refinement control files and structure files, by providing dialogues and shortcuts for many operations, by performing operations in the background, and by providing import filters for CIF and XML crystal str...

  11. Possibilities and limitations of parametric Rietveld refinement on high pressure data. The case study of LaFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Etter, Martin; Mueller, Melanie; Dinnebier, Robert E. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Hanfland, Michael [European Synchrotron Radiation Facility (ESRF), Grenoble (France)

    2014-04-01

    Parametric Rietveld refinement is a powerful technique to apply directly physical or empirical equations to the refinement of in situ powder diffraction data. In order to investigate the possibilities and limitations of parametric Rietveld refinements for high pressure data four competitive crystallographic approaches were used to carry out a full structural investigation of the orthoferrite LaFeO{sub 3} (Pbnm at ambient conditions) under high pressure up to 47 GPa. Approach A with traditional Rietveld refinement using atomic coordinates, Approach B where the Rietveld refinement was done by using the rigid body method, Approach C where symmetry modes were used and Approach D where the newly developed method of the rotational symmetry mode description for a rigid body was used. For all approaches sequential as well as parametric refinements were carried out, confirming a second order phase transition of LaFeO{sub 3} to a higher symmetric phase (space group Ibmm) at around 21.1?GPa and an isostructural first order phase transition at around 38 GPa. Limitations due to non-hydrostatic conditions as well as the possibilities of a direct modeling of phase transitions with parametric Rietveld refinement are discussed in detail. (orig.)

  12. Determination of phases of {alpha} - Fe{sub 2}O{sub 3}: SiO{sub 2} compound by the Rietveld refinement

    Energy Technology Data Exchange (ETDEWEB)

    Palomares S, S.A. [Istituto Materiali Speciali per Elettronica e Magnetismo (MASPEC), Parco Area delle Scienze 37A-43010 Loc. Fontanni, Parma (Italy); Ponce C, S.; Martinez, J.R. [Facultad de Ciencias, Universidad Autonoma de San Luis Potosi, 78000 San Luis Potosi (Mexico); Ruiz, F. [Instituto Potosino de Investigacion Cientifica y Tecnologica, Av. V. Carranza 2025, San Luis Potosi (Mexico)

    2002-07-01

    We use a variation of the Rietveld refinement method to calculate the amorphous content of composites formed by a silica xerogel amorphous matrix and iron particles embedded into. In order to apply the Rietveld refinement to amorphous structures an initial crystalline model is assumed with the same composition as the material to be modelled. In this work we try to refine the structure of compounds using the program MAUD. It is shown how this program can be used to determine the amorphous and crystalline fractions in composites consisting of an amorphous matrix and incorporated iron oxide particles. The analysed compounds underwent different thermal treatments. (Author)

  13. Full quantitative phase analysis of hydrated lime using the Rietveld method

    International Nuclear Information System (INIS)

    Lassinantti Gualtieri, Magdalena; Romagnoli, Marcello; Miselli, Paola; Cannio, Maria; Gualtieri, Alessandro F.

    2012-01-01

    Full quantitative phase analysis (FQPA) using X-ray powder diffraction and Rietveld refinements is a well-established method for the characterization of various hydraulic binders such as Portland cement and hydraulic limes. In this paper, the Rietveld method is applied to hydrated lime, a non-hydraulic traditional binder. The potential presence of an amorphous phase in this material is generally ignored. Both synchrotron radiation and a conventional X-ray source were used for data collection. The applicability of the developed control file for the Rietveld refinements was investigated using samples spiked with glass. The results were cross-checked by other independent methods such as thermal and chemical analyses. The sample microstructure was observed by transmission electron microscopy. It was found that the consistency between the different methods was satisfactory, supporting the validity of FQPA for this material. For the samples studied in this work, the amount of amorphous material was in the range 2–15 wt.%.

  14. Full quantitative phase analysis of hydrated lime using the Rietveld method

    Energy Technology Data Exchange (ETDEWEB)

    Lassinantti Gualtieri, Magdalena, E-mail: magdalena.gualtieri@unimore.it [Dipartimento Ingegneria dei Materiali e dell' Ambiente, Universita Degli Studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41100 Modena (Italy); Romagnoli, Marcello; Miselli, Paola; Cannio, Maria [Dipartimento Ingegneria dei Materiali e dell' Ambiente, Universita Degli Studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41100 Modena (Italy); Gualtieri, Alessandro F. [Dipartimento di Scienze della Terra, Universita Degli Studi di Modena e Reggio Emilia, I-41100 Modena (Italy)

    2012-09-15

    Full quantitative phase analysis (FQPA) using X-ray powder diffraction and Rietveld refinements is a well-established method for the characterization of various hydraulic binders such as Portland cement and hydraulic limes. In this paper, the Rietveld method is applied to hydrated lime, a non-hydraulic traditional binder. The potential presence of an amorphous phase in this material is generally ignored. Both synchrotron radiation and a conventional X-ray source were used for data collection. The applicability of the developed control file for the Rietveld refinements was investigated using samples spiked with glass. The results were cross-checked by other independent methods such as thermal and chemical analyses. The sample microstructure was observed by transmission electron microscopy. It was found that the consistency between the different methods was satisfactory, supporting the validity of FQPA for this material. For the samples studied in this work, the amount of amorphous material was in the range 2-15 wt.%.

  15. Magnesium substitution in carbonated hydroxyapatite: Structural and microstructural characterization by Rietveld's refinement

    Energy Technology Data Exchange (ETDEWEB)

    Lala, S. [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India); Ghosh, M.; Das, P.K. [Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Das, D. [UGC-DAE Consortium for Scientific Research, Kolkata 700098 (India); Kar, T. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Pradhan, S.K., E-mail: skpradhan@phys.buruniv.ac.in [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India)

    2016-02-15

    Four stoichiometric compositions of nanocrystalline Mg doped carbonated hydroxyapatite (cHAp) powders are synthesized by mechanical alloying (ball milling) the powder mixtures of CaCO{sub 3}, CaHPO{sub 4}.2H{sub 2}O and MgO in open air at room temperature. FTIR analysis confirms the A-type carbonation in all milled HAp powder samples (A-cHAp). Microstructure characterization in terms of lattice imperfections and phase quantification of ball milled samples are made by analyzing XRD patterns employing Rietveld's structure refinement method. Transmission electron microscopy (TEM) study of 15 mol % Mg doped A-cHAp sample reveals microstructure similar to that obtained from XRD pattern analysis. Cumulative effect of Mg substitution and mechanical alloying results in amorphization of a major part of crystalline A-cHAp, analogous to native bone mineral. Rietveld analysis reveals that the Ca2 vacancy site is energetically more favorable for occupation of Mg substitution. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals sufficiently high percentage cell viability confirming the cytocompatibility of the sample. - Graphical abstract: Mg substitution for Ca2 site. - Highlights: • Single phase Mg doped A-cHAp synthesized by mechanical alloying (MA). • FTIR analysis confirms A-type carbonation in HAp. • Amorphization of a part of crystalline A-cHAp due to MA and Mg insertion. • Mg{sup 2+} ions substitute the Ca2 vacancy site. • High cell viability under MTT assay.

  16. Chemical analysis of superconductor material by Rietveld method; Analise quimica de material superconductor atraves do metodo de Rietveld

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Junior, E.S.; Gomes Junior, G.G.; Ogasawara, T., E-mail: georges@metalmat.ufrj.b [Universidade Federal do Rio de Janeiro (COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Dept. de Eng. Metalurgica e Materiais; Bispo, E.R.; Polasek, A. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Amorim, H.S. [Universidade Federal do Rio de Janeiro (IF/UFRJ), RJ (Brazil). Inst. de Fisica

    2010-07-01

    Among the main superconducting systems, the system Bi-Sr-Ca-Cu-O is extremely important because it presents two stages of high superconducting critical temperature. To manufacture samples of the superconducting phase (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}Ox (Bi-2223) were used oxides and carbonates of high purity. The mixture was calcined and sintered for 100-200h in air. To characterize the material we used X-ray diffraction, SEM / EDS and measurement of critical temperature (Tc). The Rietveld method was used for structure refinement, and quantification of phases and to estimate the chemical composition of samples in order to obtain greater control of chemical composition using only the data of X-ray diffraction. The results were compared with the refinement results of X-ray fluorescence and was observed a discrepancy of about 8%. This result indicates that the Rietveld method can be an interesting alternative to perform chemical analysis. (author)

  17. Modulation wave approach to the structural parameterization and Rietveld refinement of low carnegieite

    International Nuclear Information System (INIS)

    Withers, R.L.; Thompson, J.G.

    1993-01-01

    The crystal structure of low carnegieite, NaAlSiO 4 [M r =142.05, orthorhombic, Pb2 1 a, a=10.261(1), b=14.030(2), c=5.1566(6) A, D x =2.542 g cm -3 , Z=4, Cu Kα 1 , λ=1.5406 A, μ=77.52 cm -1 , F(000)=559.85], is determined via Rietveld refinement from powder data, R p =0.057, R wp =0.076, R Bragg =0.050. Given that there are far too many parameters to be determined via unconstrained Rietveld refinement, a group theoretical or modulation wave approach is used in order to parameterize the structural deviation of low carnegieite from its underlying C9 aristotype. Appropriate crystal chemical constraints are applied in order to provide two distinct plausible starting models for the structure of the aluminosilicate framework. The correct starting model for the aluminosilicate framework as well as the ordering and positions of the non-framework Na atoms are then determined via Rietveld refinement. At all stages, chemical plausibility is checked via the use of the bond-length-bond-valence formalism. The JCPDS file number for low carnegieite is 44-1496. (orig.)

  18. Profex: a graphical user interface for the Rietveld refinement program BGMN.

    Science.gov (United States)

    Doebelin, Nicola; Kleeberg, Reinhard

    2015-10-01

    Profex is a graphical user interface for the Rietveld refinement program BGMN . Its interface focuses on preserving BGMN 's powerful and flexible scripting features by giving direct access to BGMN input files. Very efficient workflows for single or batch refinements are achieved by managing refinement control files and structure files, by providing dialogues and shortcuts for many operations, by performing operations in the background, and by providing import filters for CIF and XML crystal structure files. Refinement results can be easily exported for further processing. State-of-the-art graphical export of diffraction patterns to pixel and vector graphics formats allows the creation of publication-quality graphs with minimum effort. Profex reads and converts a variety of proprietary raw data formats and is thus largely instrument independent. Profex and BGMN are available under an open-source license for Windows, Linux and OS X operating systems.

  19. Rietveld refinement of Y2O3 using the pearson VII profile shape function

    International Nuclear Information System (INIS)

    Smrcok, L.

    1989-01-01

    Very good agreement between the observed and the calculated intensities was obtained using the Pearson VII profile shape function. The variable exponent m could be refined only in the damped iterations involving exclusively the profile parameters. Simultaneous refinement of the m with the positional and/or thermal parameters has led to large oscillations of the shifts of almost all parameters. Precision of the refined atomic coordinates is better than those from previously published Rietveld refinement and is comparable with single crystal results. The degree of serial correlation in residuals has been determined by the use of the Durbin-Watson d statistic. Normal probability plot based on δR i has been almost linear with the slope greater than one. The weighting scheme with w i = 1/y oi has proved to be good first approximation. (author)

  20. Rietveld refinement of magnetic structures from pulsed-neutron-source powder-diffraction data

    International Nuclear Information System (INIS)

    Robinson, R.A.; Lawson, A.C.; Larson, A.C.; Von Dreele, R.B.; Goldstone, J.A.

    1994-01-01

    The General Structure Analysis System, GSAS, has recently been modified to include magnetic neutron- scattering cross-sections. Low-temperature diffraction data have been taken on the hexagonal noncollinear antiferromagnet UPdSn on both the HIPD and the NPD powder diffractometers ail LANSCE. The low-resolution data reveal that the magnetic structure has orthorhombic symmetry (magnetic space group P c m'c2 1 ) between 25K and 40K, and monoclinic symmetry (magnetic space group PC 1121 ) below 25K. The high-resolution data reveal that there are structural distortions with corresponding symmetry changes in each of these phases, to give chemical space groups Cmc2 1 and P2 1 , respectively, while the paramagnetic phase above 40K has space group P6 3 mc. Using GSAS, we have refined data sets from both diffractometers simultaneously, including both magnetic and structural cross-sections. Magnetoelastic coefficients for the distortions have been extracted and we have determined the sign of the coupling between the structural monoclinicity and the magnetic monoclinicity. The magnetic results from Rietveld refinement are in good agreement with model fitting to the integrated intensities of seven independent magnetic reflections and these, in turn, agree with measurements made on the same sample using the constant-wavelength reactor technique. Our results therefore validate, to some level, both the technique of using spallation sources for complicated magnetic structures and the specifics of the GSAS Rietveld code

  1. Determination of Cation Distributions in Mineral Structures by use of the Rietveld Full-Profile Refinement Technique

    International Nuclear Information System (INIS)

    Nord, A.G.

    1986-01-01

    Use of the Rietveld full-profile refinement technique with X-ray or neutron powder diffraction data for the determination of divalent-metal cation distributions in three mineral structure types (farringtonite, grafonite, sarcopside) is demonstrated. The accuracy of the conventional cation distribution coefficient Ksub(D) is about 5-10 percent with 24-46 parameters to be refined, and the averaged metal-oxygen distances are reliable and well correlated to the observed cation distribution pattern. In particular the usefulness of the Rietveld technique in combination with Moessbauer spectroscopy is stressed. Some concluding remarks are also given

  2. A modified Rietveld method to model highly anisotropic ceramics

    International Nuclear Information System (INIS)

    Tutuncu, G.; Motahari, M.; Daymond, M.R.; Ustundag, E.

    2012-01-01

    High energy X-ray diffraction was employed to probe the complex constitutive behavior of a polycrystalline ferroelectric material in various sample orientations. Pb(Zn,Nb)O 3 –Pb(Zr,Ti)O 3 (PZN–PZT) ceramics were subjected to a cyclic bipolar electric field while diffraction patterns were taken. Using transmission geometry and a two-dimensional detector, lattice strain and texture evolution (domain switching) were measured in multiple sample directions simultaneously. In addition, texture analysis suggests that non-180° domain switching is coupled with lattice strain evolution during uniaxial electrical loading. As a result of this material’s high strain anisotropy, the full-pattern Rietveld method was inadequate to analyze the diffraction data. Instead, a modified Rietveld method, which includes an elastic anisotropy term, yielded significant improvements in the data analysis results.

  3. In-situ high-energy X-ray diffraction and batch Rietveld refinement of phase changes in titanium aluminides

    International Nuclear Information System (INIS)

    Whitfield, R.

    2007-01-01

    Full text: We have used the Rietveld refinement method for the analysis of high-energy X-ray power diffraction for quantitatve phase analysis. This method has the advantage of being able to model the multiple phases appearing in the diffraction pattern and tell us about the composition of the phases of a sample as we change the temperature. It has been applied to various TiAl compounds allowing us to follow in detail the phase transitions of the intermetallics when heated to around 1400 0 Cand subsequently cooled. Small amounts of additives like V, Cr and Gd as well as signatures from different production processes can be seen to have an effect on the phase transitions. With increasing temperature we can see the evolution of the unit cell due to thermal expansion, chemical segregation and the relative proportion of phase changes

  4. Characterization of barium titanate powder doped with sodium and potassium ions by using Rietveld refining; Caracterizacao do po de titanato de bario dopado com ions sodio e potasio com o refinamento de Rietveld

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, M.C.; Assis, J.T.; Pereira, F.R., E-mail: mcalixto@iprj.uerj.b [Universidade do Estado do Rio de Janeiro (IPRJ/UERJ), Nova Friburgo, RJ (Brazil). Instituto Politecnico; Araujo, J.C. [Universidade do Estado do Rio de Janeiro (FFP/UERJ), Sao Goncalo, RJ (Brazil). Fac. de Formacao de Professores; Moreira, E.L.; Moraes, V.C.A.; Lopes, A.R. [Centro Brasileiro de Pesquisas Fisicas (CBPF/MCT), Rio de Janeiro, RJ (Brazil)

    2009-07-01

    A solid-reaction synthesis of doped barium titanate was done by employing barium carbonates, sodium, potassium and titanium oxides with classic procedures. Rietveld refining of X ray diffraction data of perovskite samples with tetragonal symmetry was applying and show good agreement. Besides, the treatment performed from 600 deg C produces nanocrystals of barium titanate with average size of 33 nm. The presence of endothermic peaks related to BaTiO{sub 3} formation at relatively low temperatures was determined by thermal analysis. A pseudo-Voigt Thompson-Cox-Hastings function was used to fit the standard samples of barium titanate. The Rietveld method has showed be efficient to detect the influences of temperature and doping on barium titanate microstructures. (author)

  5. Rietveld refinement of the crystal structures of Rb2XSi5O12 (X = Ni, Mn

    Directory of Open Access Journals (Sweden)

    Anthony M. T. Bell

    2016-02-01

    Full Text Available The synthetic leucite silicate framework mineral analogues Rb2XSi5O12 {X = Ni [dirubidium nickel(II pentasilicate] and Mn [dirubidium manganese(II pentasilicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetrahedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb+ cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetrahedrally coordinated sites (T-sites. However, the Ni displacement parameter and the Ni—O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder.

  6. Rietveld refinement and FTIR analysis of bulk ceramic Co3-xMnxO4 compositions

    Science.gov (United States)

    Meena, P. L.; Kumar, Ravi; Sreenivas, K.

    2013-02-01

    Co3-xMnxO4 (x = 0.0, 0.6, 1.2) prepared by solid state reaction method and characterized by powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR). Lattice parameters (a), oxygen parameter (u), and ionic radii of cations have been determined through Rietveld analysis. Both a and u parameters are related to expansion of octahedral site as Mn content in Co3O4. Analysis of XRD data show that Mn (x ≤ 1.2) is accommodated at the octahedral site, while retaining the cubic spinel structure. FTIR results also confirm the same and signify strong interactions due to overlapping of Co and Mn octahedra.

  7. The role of iron in tetrahedrite and tennantite determined by Rietveld refinement of neutron powder diffraction data

    DEFF Research Database (Denmark)

    Andreasen, Jens Wenzel; Makovicky, Emil; Lebech, Bente

    2008-01-01

    Rietveld refinement of neutron powder diffraction data on four samples of synthetic, iron-bearing tetrahedrite (Cu12-xFexSb4S13) with x = 0.28, 0.69, 0.91, 2.19 and four samples of synthetic tennantite (Cu12-xFexAs4S13) with x = 0.33, 0.38, 0.86, 1.5 indicate unambiguously that iron is incorporated...

  8. Rietveld refinement and electronic structure studies for the Sm2FeMnO6 new complex perovskite

    International Nuclear Information System (INIS)

    Landinez Tellez, D.A.; Munevar, J.A.; Arbey Rodriguez, J.M.; Fajardo, F.; Roa-Rojas, J.

    2008-01-01

    We report synthesis and crystalline structure study of the Sm 2 FeMnO 6 new complex perovskite, by X-ray diffraction experiments and through the application of Rietveld refinement. Results revealed the crystallization of system in a structure given by Pmn21 (no. 31) space group and lattice parameters a=7.621(1) A, b=5.675(3) A and c=5.378(3) A. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system by the density functional theory (DFT) and using the full-potential linearized augmented plane waves (FP-LAPW) method. All calculations were carried out using spin polarization. Material evidences a conductor-like character, predominantly due to d-xy Fe orbital of the spin down channel. Magnetic response of system has contributions of Fe and Mn spin up orientation. The calculated magnetic moment in cell was 34.48 μ B and the magnetic moment in interstitial was 1.54 μ B

  9. Separation of the overlapping effects in spectra for WDXRF using the Rietveld method

    International Nuclear Information System (INIS)

    Salvador, Vera Lucia Ribeiro

    2005-01-01

    This work presents a new methodology for the overlapping spectra separation obtained by the technique of wavelength dispersion X-ray fluorescence (WDXRF). This methodology allows to improve the conventional analytic results and to facilitate the determination of chemical species of a same element without chemical separation, by means of the separation of coming spectra of electronic transitions of valence electrons or chemical effects in internal electrons. With the software 'GSAS-EXPGUI' and the method of Rietveld overcomes the problem of overlapping lines of the present species in the sample and it facilitates the determination of the same ones simultaneously, without the need of samples patterns and calibration curves, what means an expressive gain in relation to other techniques. The preparation of the surface of the sample for the collection of the spectrum represents a critical stage for the acting of the analysis whose effects can be minimized being used the refinement of Rietveld, that allows the determination of the relationships of the intensities of the lines put upon by means of mathematical models, what establishes the basic conditions for obtaining of more precise results in the quantitative analysis. In the case of the determination of chemical species it can separate, for example Cr (III), Cr (VI) and Fe (II), Fe(III) that present overlapping of almost 100%. (author)

  10. Effect of data quality on quantitative phase analysis (QPA) using the Rietveld method

    International Nuclear Information System (INIS)

    Scarlett, N.; Madsen, I.; Lwin, T.

    1999-01-01

    Full text: Quantitative phase analysis using the Rietveld method has become a valuable tool in modern X-ray diffraction. XRD is a recognised research tool and has been successfully employed in the developmental stages of many industrial processes. It is now becoming increasingly important as a means of process control either (i) in site quality control laboratories or (ii) even on-line. In on-line applications, the optimisation of data collection regimes is of critical importance if rapid turn-around, and hence timely process control, is to be achieved. This paper examines the effect of data quality on the quantification of phases in well characterised suites of minerals. A range of data collection regimes has been systematically investigated with a view to determining the minimum data required for acceptable quantitative phase analyses. Data has been collected with variations in the following process factors: 1st step, width ranging from 0.01 to 0.3 deg 2θ ;2nd step, counting time ranging from 0.0125 to 4 sec/step 3rd step, upper limit in the scan range varying from 40 to 148 deg 2θ. The data has been analysed using whole-pattern (Rietveld) based methods using two distinctly different analytical approaches: (i) refinement of only pattern background and individual scale factors for each phase; (ii) refinement of unit cell dimensions, overall thermal parameters, peak width and shape in addition to the background and scale factors. The experimental design for this work included a ternary design of the three component phases (fluorite, CaF 2 ; zincite, ZnO; corundum, Al 2 O 3 ) to form seven mixtures of major and minor phases of different scattering powers and the combination of the three process factors (variables) to form a factorial plan. The final data generation plan is a combination/crossing of the three process variable factorial plan with the three component mixture plan. It allows a detailed data analysis to provide information on the effect of the process

  11. Tailoring diffraction technique Rietveld method on residual stress measurements of cold-can oiled 304 stainless steel plates

    International Nuclear Information System (INIS)

    Parikin; Killen, P.; Anis, M.

    2003-01-01

    Tailoring of diffraction technique-Rietveld method on residual stress measurements of cold-canailed stainless steel 304 plates assuming the material is isotopic, the residual stress measurements using X-ray powder diffraction is just performed for a plane lying in a large angle. For anisotropic materials, the real measurements will not be represented by the methods. By Utilizing of all diffraction peaks in the observation region, tailoring diffraction technique-Rietveld analysis is able to cover the limitations. The residual stress measurement using X-ray powder diffraction tailored by Rietveld method, in a series of cold-canailed stainless steel 304 plates deforming; 0, 34, 84, 152, 158, 175, and 196 % reduction in thickness, have been reported. The diffraction data were analyzed by using Rietveld structure refinement method. Also, for all cold-canailed stainless steel 304 plates cuplikans, the diffraction peaks are broader than the uncanailed one, indicating that the strains in these cuplikans are inhomogeneous. From an analysis of the refined peak shape parameters, the average root-mean square strain, which describes the distribution of the inhomogeneous strain field, was calculated. Finally, the average residual stresses in cold-canailed stainless steel 304 plates were shown to be a combination effect of hydrostatic stresses of martensite particles and austenite matrix. The average residual stresses were evaluated from the experimentally determined average lattice strains in each phase. It was found the tensile residual stress in a cuplikan was maximum, reaching 442 MPa, for a cuplikan reducing 34% in thickness and minimum for a 196% cuplikan

  12. Investigation on the evolution of microstructure and texture of electroplated Ni–Ti composite coating by Rietveld method

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yuantao, E-mail: zhaoyuantao@sjtu.edu.cn; Cai, Fei, E-mail: caifei32@126.com; Wang, Chengxi, E-mail: sjtucxw@sjtu.edu.cn; Chai, Ze, E-mail: zechaisjtu@163.com; Zhu, Kaiyuan, E-mail: xrd125@163.com; Xu, Zhou, E-mail: xuzhou@sjtu.edu.cn; Jiang, Chuanhai, E-mail: chjiang-sjtu@hotmail.com

    2015-10-30

    Highlights: • Ni–Ti composite coatings were prepared by electroplating. • Morphology and Ti content of Ni–Ti coatings were studied upon SEM and EDXS. • Microstructures of Ni–Ti coatings were studied upon the Rietveld method. • The texture of Ni–Ti coatings was studied upon the pole figure. - Abstract: Rietveld refinement was utilized to investigate the evolution of microstructure and texture of the Ni–Ti composite coatings electroplated at different applied current densities. Scanning Electron Microscope and Energy Dispersive Spectroscopy were utilized to investigate the morphology and chemical composition of the coatings. Relative texture coefficients (RTC) and measured pole figures were utilized to investigate the texture evolution of the coatings. The results showed that the surface morphology of the coatings changed from a colonial structure to a polyhedral one. And the incorporated Ti content decreased with increasing applied current density. As the applied current density increased, the crystallite sizes increased and their distribution got less uniform, and the microstrain and dislocation density decreased. The results of simulated pole figures obtained from Rietveld refinement illustrated that the texture of the coatings changed from no obvious texture to a strong [2 0 0] fiber texture with increasing applied current density. The texture evolution obtained from simulated pole figures was confirmed by the result of RTC and the measured pole figures. The evolutions of the microstructure and texture were derived from the change of the applied current density and incorporated Ti content in the Ni–Ti composite coatings.

  13. Rietveld structure refinement and elastic properties of MgAlxCrxFe2-2xO4 spinel ferrites

    Science.gov (United States)

    Thummer, K. P.; Tanna, Ashish R.; Joshi, Hiren H.

    2017-05-01

    MgAlxCrxFe2-2xO4 (x = 0.1, 03 & 0.6) ferrites are synthesized by solid state reaction method. The Rietveld refinement of X-ray diffraction (XRD) data confirms the cubic spinel structure with Fd3m space group. The Fourier Transform Infrared Transmission Spectroscopy (FTIR) is employed to study elastic properties of present systems at 300K. The force constants for tetrahedral (A) and octahedral (B) sites of the spinel lattice are determined by infrared spectral and X-ray diffraction analysis. The elastic constants like bulk modulus, rigidity modulus, Young's modulus, Poisson's ratio and Debye temperature are determined. The vibrational frequency of both the interstitial sites increases as Al-Cr content increases hence the force constant and elastic moduli for all the samples are found to increase for the present ferrite system.

  14. Analysis of Polymorphic Nanocrystals of TiO2 by X-Ray Rietveld Refinement and High-Resolution Transmission Electron Microscopy: Acetaldehyde Decomposition

    Directory of Open Access Journals (Sweden)

    R. Carrera

    2008-01-01

    Full Text Available In this work, TiO2 nanocrystals were synthesized by the sol-gel method. These materials were annealed at 200 and 500∘C; and characterized by the XRD-Rietveld refinement; and by BET and TEM. As for the low-temperature-treated sample (200∘C, nanocrystals with small crystallite sizes (7 nm and high abundance of anatase, coexisting with the brookite phase, were obtained. Meanwhile, the sample annealed at 500∘C showed an increased crystallite size (22 nm and an important polymorphic increment. The sample annealed at 200∘C showed a high activity in the photocatalytic decomposition of acetaldehyde.

  15. Crystal structure analysis of LaMnO_3 with x-ray diffraction technique using the Rietveld method

    International Nuclear Information System (INIS)

    Engkir Sukirman; Wisnu Ari Adi; Yustinus Purwamargapratala

    2010-01-01

    Crystal structure analysis of LaMnO_3 using the Rietveld method has been carried out. The LaMnO_3 sample was synthesized with high energy mechanical milling from the raw materials of La_2O_3 and MnO_2 with the appropriate mol ratio. Milling were performed for 10 hours, pelletized and hereinafter sintered at 1350 °C for 6 hours. The sample characterizations covered the crystal structure and electric-magnetic properties of the materials by X-ray diffraction technique using the Rietveld method and the four point probe, respectively. The Rietveld refinement results based on the X-rays diffraction data indicate that the sample of LaMnO_3 is single phase with the crystal system: orthorhombic, the space group: Pnma No. 62 and the lattice parameters: a = 55.4405(9) Å; b = 7.717(1) Å dan c = 5.537(1) Å. The material owns Magnetic Resonance (MR) respond of 7 %, the mean value of crystallite size, D = 17 nm and lattice strain, e = - 0.5 %. So, the material go through a compressive strain, and according to the Nanda's strain model, it becomes a type G antiferromagnetic insulator. Because the insulator properties of the material does not change although being hit by the external magnetic field, hence the MR respond is only caused by the order of electron spin. Therefore at room temperature, LaMnO_3_._0 just exhibits a small MR respond. (author)

  16. Quantitative phase analysis of uranium carbide from x-ray diffraction data using the Rietveld method

    International Nuclear Information System (INIS)

    Singh Mudher, K.D.; Krishnan, K.

    2003-01-01

    Quantitative phase analysis of a uranium carbide sample was carried out from the x-ray diffraction data by Rietveld profile fitting method. The method does not require the addition of any reference material. The percentage of UC, UC 2 and UO 2 phases in the sample were determined. (author)

  17. A new approach to texture measurements: Orientation distribution function (ODF) determination by Rietveld refinement

    International Nuclear Information System (INIS)

    Vondreele, R.; Larson, A.; Lawson, A.; Sheldon, R.; Wright, S.

    1996-01-01

    The preferred orientation of crystal grains within a manufactured part is described most fully by its orientation distribution function (ODF), which is a mapping of the probability of each of the possible grain orientations with respect to the exterior dimensions. Traditionally, an ODF is determined from pole figures for a relatively small number of reflections. These pole figures are measured with x-rays or neutrons using short detector scans over the center of an individual diffraction peak for a large number of different sample orientations. This is efficient if the selected diffraction peaks are reasonably strong (relative to background) and well separated, such as in pure fcc and bcc metals. It is also appropriate for constant wavelength sources where collection of individual diffraction peak intensities is a reasonably efficient use of the source. However, the traditional method is not very efficient for neutron diffraction at a spallation source such as LANSCE where the entire diffraction pattern is accessible for each sample setting. Moreover, a different approach is necessary for complicated diffraction patterns, such as from composite materials, intermetallic compounds, high T c ceramics, polyphasic minerals and polymers where there is expected to be heavy overlap of adjacent diffraction peaks. In addition, the large number of settings normally collected for an individual pole figure may not be necessary, since the entire pattern is obtained at each setting. Thus, a new method of ODF analysis needs to be developed to handle the more complex diffraction patterns obtained from modern technological materials as well as take advantage of the particular characteristics of spallation neutron sources. This project sought to develop the experimental procedures and the mathematical treatment needed to produce an orientation distribution function (ODF) directly from full diffraction patterns from a sample in a limited number of orientations

  18. Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250 degrees C by means of Rietveld refinement of synchrotron data

    DEFF Research Database (Denmark)

    Friese, K.; Grzechnik, A.; Makovicky, E.

    2008-01-01

    Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M-12(Sb,As)(4)S-13. Measurements were performed at 25 and 250 degrees C. For both the phases...

  19. Structural Rietveld refinement and vibrational study of MgCr{sub x}Fe{sub 2−x}O{sub 4} spinel ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Sabri, K. [Laboratoire des Sciences et technique de l’Environnement et de la Valorisation, département de Génie des Procédés, Université de Mostaganem, Mostaganem (Algeria); Rais, A., E-mail: amrais@yahoo.com [Laboratoire des Sciences et technique de l’Environnement et de la Valorisation, département de Génie des Procédés, Université de Mostaganem, Mostaganem (Algeria); Taibi, K. [Laboratoire de Science et Génie des Matériaux, USTHB, Alger, Algéria (Algeria); Moreau, M.; Ouddane, B. [Laboratory of LASIR Spectrochemistry, University of Science and Technology, 59650 Villeneuve d’Ascq (France); Addou, A. [Laboratoire des Sciences et technique de l’Environnement et de la Valorisation, département de Génie des Procédés, Université de Mostaganem, Mostaganem (Algeria)

    2016-11-15

    Spinel ferrites with the general formula MgCr{sub x}Fe{sub 2−x}O{sub 4} (0≤x≤1) were synthesized by the standard ceramic technique and characterized by X-ray diffraction. The XRD patterns confirmed that the mixed ferrite samples are in the cubic spinel structure which is further validated by Rietveld refinement in the space group Fd3m. The crystal structure and cell parameters were refined by Rietveld analysis. The vibrational study was achieved using Fourier Transform-InfraRed (FT-IR) and Raman spectroscopy. From FT-IR band frequencies, the force constants K{sub t} and K{sub o} , for tetrahedral (A) and octahedral (B) sites respectively, have been calculated and discussed with the trend of bond lengths obtained from Rietveld refinement. For all compositions, Raman spectra revealed the five active modes showing the vibration of O{sup 2−} ions at both the A-site and B-site ions. The frequencies trend with chromium content of both FT-IR and Raman spectra showed a shift toward higher values for all modes.

  20. Application of the Rietveld method in structural analysis of catalysts based on CuO/CeO2

    International Nuclear Information System (INIS)

    Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Simoes, A.N.; Gama, L.

    2011-01-01

    This work has as aim to synthesize catalysts composed by CuO/CeO 2 by means two distinct methods of synthesis, they are: combustion synthesis and Pechini. The catalysts composed by CuO/CeO 2 were synthesized with CuO in condition of dopant element. The value of the CuO concentration ranged between 0 and 0.5 mol. Has been done a structural analysis related to how the kind of synthesis method used influences over physical characteristic of the catalytic material. The obtained catalysts were characterized by X-ray diffraction with refinement by Rietveld method. According to results, the synthesized catalysts showed crystalline structures formed mostly by CeO 2 phase, as expected, since this is the host matrix for the dopant element. The catalysts obtained by the Pechini method presented structures with a smaller amount of segregated phases formed by CuO, according to the results of the structural analysis. (author)

  1. Quantitative determination of the crystalline phases of the ceramic materials utilizing the Rietveld method

    International Nuclear Information System (INIS)

    Kniess, C.T.; Prates, P.B.; Lima, J.C. de; Kuhnen, N.C.; Riella, H.G.; Maliska, A.M.

    2009-01-01

    Ceramic materials have properties defined by their chemical and micro-structural composition. The quantification of the crystalline phases is a fundamental stage in the determination of the structure, properties and applications of a ceramic material. Within this context, this study aims is the quantitative determination of the crystalline phases of the ceramic materials developed with addition of mineral coal bottom ash, utilizing the X ray diffraction technique, through the method proposed by Rietveld. For the formulation of the ceramic mixtures a {3,3} simplex-lattice design was used, giving ten formulations of three components (two different types of clays and coal bottom ash). The crystalline phases identified in the ceramic materials after sintering at 1150 deg C during two hours are: quartz, tridimite, mullite and hematite. The proposed methodology utilizing the Rietveld method for the quantification relating to crystalline phases of the materials was shown to be adequate and efficient. (author)

  2. Application of the Rietveld method to assess chromium(VI) speciation in chromite ore processing residue

    International Nuclear Information System (INIS)

    Chrysochoou, Maria; Dermatas, Dimitris

    2007-01-01

    The Rietveld method allows the quantification of crystalline phases and amorphous material identified by X-ray powder diffraction (XRPD) and other diffraction methods. The method assists in determining the speciation of contaminants in solid matrices both qualitatively and quantitatively in a statistically defensible approach, as it does not focus on a microscale. Rietveld was applied to chromite ore processing residue (COPR), a cementitious waste containing hexavalent chromium. Calcium aluminum chromium oxide hydrates (CACs) were the crystalline phases identified by XRPD that bind Cr 6+ in COPR according to their chemical formula. Rietveld quantification, combined with mass balances on Cr 6+ , showed that CACs may bind Cr 6+ in variable percentages, ranging from 25% to 85%. Analysis of duplicate samples showed that material variability is the predominant factor of uncertainty in evaluating the role of CACs in Cr 6+ speciation, provided that a consistent quantification strategy is pursued. The choice of strategy was performed on the basis of the pertinent literature, preliminary analyses of the equipment and the software settings, and mass balances. The correlation between the average CAC-bound Cr 6+ concentration and the total Cr 6+ for five samples (R 2 = 0.94), extracted from different zones and soil borings, suggests that CACs are a primary sink for Cr 6+ in COPR

  3. Crystal phase analysis of SnO2-based varistor ceramic using the Rietveld method

    International Nuclear Information System (INIS)

    Moreira, M.L.; Pianaro, S.A.; Andrade, A.V.C.; Zara, A.J.

    2006-01-01

    A second addition of l mol% of CoO to a pre calcined SnO 2 -based ceramic doped with 1.0 mol% of CoO, 0.05 mol% of Nb 2 O 5 and 0.05 mol% of Cr 2 O 3 promotes the appearance of a secondary phase, Co 2 SnO 4 , besides the SnO 2 cassiterite phase, when the ceramic was sintered at 1350 deg. C/2 h. This was observed using X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray techniques. Rietveld refinement was carried out to quantify the phases present in the ceramic system. The results of the quantitative analysis were 97 wt.% SnO 2 and 3 wt.% Co 2 SnO 4 . The microstructural analysis showed that a certain amount of cobalt ion remains into cassiterite grains

  4. Study of crystallite size of yttria-stabilized zirconia powders by Rietveld method

    International Nuclear Information System (INIS)

    Leite, Wellington Claiton; Brinatti, Andre Mauricio; Ribeiro, Mauricio Aparecido; Andrade, Andre Vitor Chaves de; Chinelatto, Adriana Scoton Antonio; Chinelatto, Adilson Luiz

    2009-01-01

    The yttria-stabilized zirconia (YSZ) is used in a great variety of applications, for example, electrolytes of solid oxide fuel cells and oxygen sensors. In the study of YSZ, the particle size powders and sintering processes are important to define the final properties of the zirconia products. The objectives of this work were to determine the phases and the crystalline size using X-Ray Diffraction (XRD) data and the Rietveld Method (RM) of the YSZ powders obtained by chemical synthesis based on the Pechini method. It was used ZrOCl 2.8 H 2 O and Y(NO 3 ) 3.5 H 2 O as precursors reagents. After calcination at 550 deg C during 24 hours, the powder was analyzed by XRD and scanning electronic microscopy (SEM). From XRD and using Rietveld method were verified that there is only cubic phase with lattice parameter a = 5.1307(1) Å and the space group Fm3m. Due to substitution of the Zr atoms in the Y atoms sites, there were vacancies in 17.72 % of O atoms sites. However, the percentage of substitution of Zr atoms in Y atoms sites in the structure not was determinate because the curves of atomic scattering of them are very similar. Using Scherrer equation and considering anisotropy effect, the average crystalline size was determinate: 10,43 nm (c axis) and 10,39 (b axis). This spherical symmetry also observed for SEM. (author)

  5. Study the oxidation kinetics of uranium using XRD and Rietveld method

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yanzhi; Guan Weijun; Wang Qinguo; Wang Xiaolin; Lai Xinchun; Shuai Maobing, E-mail: yanzhizh@163.com [China Academy of Engineering Physics, PO Box 919-71, Mianyang, Sichuan, 621900 (China)

    2010-03-15

    The surface oxidation of uranium metal has been studied by X-ray diffraction (XRD) and Rietveld method in the range of 50{approx}300deg. C in air. The oxidation processes are analyzed by XRD to determine the extent of surface oxidation and the oxide structure. The dynamics expression for the formation of UO{sub 2} was derived. At the beginning, the dynamic expression was nonlinear, but switched to linear subsequently for uranium in air and humid oxygen. That is, the growth kinetics of UO{sub 2} can be divided into two stages: nonlinear portion and linear portion. Using the kinetic data of linear portion, the activation energy of reaction between uranium and air was calculated about 46.0 kJ/mol. However the content of oxide as a function of time was linear in humid helium ambience. Contrast the dynamics results, it prove that the absence of oxygen would accelerate the corrosion rate of uranium in the humid gas. We can find that the XRD and Rietveld method are a useful convenient method to estimate the kinetics and thermodynamics of solid-gas reaction.

  6. Study the oxidation kinetics of uranium using XRD and Rietveld method

    Science.gov (United States)

    Zhang, Yanzhi; Guan, Weijun; Wang, Qinguo; Wang, Xiaolin; Lai, Xinchun; Shuai, Maobing

    2010-03-01

    The surface oxidation of uranium metal has been studied by X-ray diffraction (XRD) and Rietveld method in the range of 50~300°C in air. The oxidation processes are analyzed by XRD to determine the extent of surface oxidation and the oxide structure. The dynamics expression for the formation of UO2 was derived. At the beginning, the dynamic expression was nonlinear, but switched to linear subsequently for uranium in air and humid oxygen. That is, the growth kinetics of UO2 can be divided into two stages: nonlinear portion and linear portion. Using the kinetic data of linear portion, the activation energy of reaction between uranium and air was calculated about 46.0 kJ/mol. However the content of oxide as a function of time was linear in humid helium ambience. Contrast the dynamics results, it prove that the absence of oxygen would accelerate the corrosion rate of uranium in the humid gas. We can find that the XRD and Rietveld method are a useful convenient method to estimate the kinetics and thermodynamics of solid-gas reaction.

  7. Study of the superconducting compound Hg,Re-1223 by X-Ray diffraction with application of Rietveld method

    International Nuclear Information System (INIS)

    Putvinskis, Rodrigo

    2008-01-01

    The objective of this work was to study the crystal structure of the superconductor compound of nominal composition Hg 0,82 Re 0,18 Ba 2 Ca 2 Cu 3 O 8+δ and general formula Hg,Re- 1223 and different oxygen contents, by the X-ray diffraction technique, by using the Rietveld method. The studied samples present different oxygen stoichiometry because during the synthesis process, had been heat treated under different oxygen/argon gas mixtures in the ratios: 5:95, 10:90 and 15:85. The results of structural refinement for the samples show that different oxygen contents imply in different cell parameters, atomic positions and distances for the main phase of each sample. The segregation of two superconducting phases with the same crystal structure, but slightly different cell parameters was confirmed for the studied samples both by Rietveld analysis and anomalous X-ray diffraction experiments. It was also confirmed that one of the segregated phases does not incorporate Re cations its composition. The main phase, who incorporates the Re cations, is here called Hg,Re-1223 and the Re-free secondary phase is called Hg- 1223. It was found that the superconducting phases present different crystallite sizes and the sample treated under gas flow composed of 10% oxygen and 90% argon presents the highest fraction of superconducting phases. From these results it was possible to conclude that the sample produced from the precursor compound treated under flow of O 2 /Ar gas at the ratio 10/90 presents the better results for the synthesis of this superconducting compound. (author)

  8. Structural studies of TiC1−xOx solid solution by Rietveld refinement and first-principles calculations

    International Nuclear Information System (INIS)

    Jiang, Bo; Hou, Na; Huang, Shanyan; Zhou, Gege; Hou, Jungang; Cao, Zhanmin; Zhu, Hongmin

    2013-01-01

    The lattice parameters, structural stability and electronic structure of titanium oxycarbides (TiC 1−x O x , 0≤x≤1) solid solution were investigated by Rietveld refinement and first-principles calculations. Series of TiC 1−x O x were precisely synthesized by sintering process under the vacuum. Rietveld refinement results of XRD patterns show the properties of continuous solid solution in TiC 1−x O x over the whole composition range. The lattice parameters vary from 0.4324 nm to 0.4194 nm decreasing with increasing oxygen concentration. Results of first-principles calculations reveal that the disorder C/O structure is stable than the order C/O structure. Further investigations of the vacancy in Ti 1−Va (C 1−x O x ) 1−Va solid solution present that the structure of vacancy segregated in TiO-part is more stable than the disorder C/O structure, which can be ascribed to the Ti–Ti bond across O-vacancy and the charge redistributed around Ti-vacancy via the analysis of the electron density difference plots and PDOS. - Graphical abstract: XRD of series of titanium oxycarbides (TiC 1−x O x , 0≤x≤1) solid solution prepared by adjusting the proportion of TiO in the starting material. Highlights: • Titanium oxycarbides were obtained by sintering TiO and TiC under carefully controlled conditions. • Rietveld refinement results show continuous solid solution with FCC structure in TiC 1−x O x . • The disorder C/O structure is stable than the order C/O structure. • Introduction of vacancy segregated in TiO-part is more stable than disorder C/O structure. • Ti–Ti bond across O-vacancy and the charge redistributed around Ti-vacancy enhance structural stability

  9. Rietica - a visual Rietveld program

    International Nuclear Information System (INIS)

    Hunter, B.A.

    2000-01-01

    Full text: Rietica is a Rietveld analysis program that allows interaction with the refinement process on a cycle by cycle basis using a graphic interface. Rietica was developed to aid in the creation and updating of the Rietveld input files, as well as to control the LHPM program. It is a Windows 95 based program allowing point and click control of all the functionality of LHPM. Some of the features of the Rietica program are: multiple x-ray and/or neutron histograms (datasets) allowing different scales, zeros, peak profile types and values, backgrounds, wavelengths, preferred orientations for each histogram - all of which are refinable, (1) ability to calculate and refine neutron time-of-flight (TOF) data, (2) ability to refine Δf' and Δf'' now allows extra flexibility with synchrotron diffraction data, (3) can interpolate x-ray form factors from a series of (sin(θ)/λ, f) values (eg Bessel functions), (4) a new absorption correction formula allowing μR > 1.0 for cylindrical geometry and a flat plate absorption correction based surface roughness, (5) new background functions, (6) quantitative phase analysis routines, (7) point and click data entry and program control, (8) data display and easy background and excluded region input via mouse control, (9) control of the refinement process, including automatic updating of the calculated pattern display after each step, (10) can refine using 3 strategies: a) a point and click mode of data entry and refinement control (beginners/intermediate/advanced users); b) a manual editing of the input file, but still with all the benefits of the visual interface and online graphics (intermediate/advanced users); and c) a Basic scripting language that can be used to control the refinement process and graphics output. It could be used, say, for automatic refinement of large numbers of datasets (advanced users). The program currently reads in LHPM and GSAS/Fullprof/DWBS experiment files and export in a variety of formats. The

  10. Rietveld refinement and dielectric studies of Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Kaswan, Kavita, E-mail: kaswan.kavita@gmail.com; Agarwal, Ashish; Sanghi, Sujata; Rangi, Manisha; Jangra, Sandhaya; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar 125001, Haryana (India)

    2016-05-23

    Polycrystalline Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3} ceramic has been synthesized via conventional solid state reaction technique. The Rietveld refinement of x-ray powder diffraction revealed that the sample has a rhombohedral crystal structure (space group R3c). With increase in temperature, the values of dielectric constant (ϵ′) and dielectric loss (tan δ) are found to be increase at different frequencies which may be the result of increase in the number of charge carriers and their mobilities due to the thermal activation. Further the ac conductivity data is analyzed by using Jonscher’s universal power law. The values of frequency exponent ‘s’ lies in the range 0.2 ≤ s ≤ 0.7 and decreases with increase in temperature which can be explained on the basis of CBH (Correlated Barrier Height) model.

  11. Rietveld refinement and dielectric relaxation of a new rare earth based double perovskite oxide: BaPrCoNbO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Bharti, Chandrahas, E-mail: bharti.chandrahas@gmail.com [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Das, Mrinmoy K.; Sen, A. [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Chanda, Sadhan; Sinha, T.P. [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata-700009 (India)

    2014-02-15

    A new rare earth based double perovskite oxide barium praseodymium cobalt niobate, BaPrCoNbO{sub 6} (BPCN) is synthesized by solid-state reaction technique. Rietveld analysis of X-ray diffraction (XRD) data shows that the compound crystallizes in a perovskite like tetragonal structure which belongs to the I4/mmm space group with lattice parameters a=b=5.6828(9) Å, c=8.063(2) Å. Structural analysis reveals 1:1 ordered arrangement for the Co{sup 2+} and Nb{sup 5+} cations over the six-coordinate B-sites of BPCN. The superlattice line (1 0 1) at 2θ=19.10° arising from the alternate ordering of Co{sup 2+} and Nb{sup 5+} sites is observed in the XRD pattern which confirms the presence of cation ordering in BPCN. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO{sub 6} stretching vibration. The relaxation dynamics of the conductive process in BPCN is investigated in the temperature range 303 to 503 K and in the frequency range 100 Hz to 1 MHz using impedance spectroscopy. The relaxation mechanism of the sample in the framework of electric modulus formalism is modeled by Davidson–Cole model (DCM). The values of α (distribution of relaxation time) for the DCM varies from 0.1 to 0.3 which suggests the asymmetric distribution of relaxation time for BPCN. The activation energy of the sample, calculated from both conductivity and modulus spectra, are found to be almost the same ∼0.4 eV, which indicates that the conduction mechanism for BPCN is polaron hopping. The scaling behaviour of the imaginary part of electric modulus suggests that the relaxation follows the same mechanism at various temperatures. - Graphical abstract: Rietveld refinement plot for BPCN. Inset shows the schematic presentation of the BPCN tetragonal unit cell. The Co{sup 2+} atoms are located at the centers of the CoO{sub 6} (blue) octahedra. The Nb{sup 5+} atoms are located at the centers of the NbO{sub 6} (green) octahedra. Display Omitted

  12. A research of the mineralogy phases of clinker in a spanish cement using the method of Rietveld

    International Nuclear Information System (INIS)

    Castanon Ana M; Garcia Granda Santiago; Guerrero Ana M; Gomez Fernandez Fernando

    2012-01-01

    In order to introduce continuously a quality control method in a Spanish cement factory to improve the final product feature new research methodology is being developed. The Rietveld method [1] has been successfully used to analyze the composition of the main phases of clinker. Using this methodologies, research has been carried out to quantize appropriately the minor phase of free lime which is extremely important in the clinker quality. This method leads to satisfactory results on samples with contents in CaO from 3%. These results are possible combining X- ray diffraction and fluorescence techniques as well as the chemical analysis data. Clinker, the Rietveld method, free lime.

  13. The use of the Rietveld method as an evaluation tool in the stages of production of nanostructured hard metal

    International Nuclear Information System (INIS)

    Batista, A.C.; Perpetuo, G.J.; Oliveira, H.C.P. de; Silva, T.R.G. da

    2014-01-01

    The processing of the composite WC-10% Co, with nanometric grain size was analyzed aiming at identifying changes undergone by the material during mixing and compaction steps. Use the X-ray diffraction and the Rietveld method to obtain accurate data on the behavior of powders before these steps. This paper describes the use of the Rietveld method as an evaluation tool to obtain information about the behavior of powders of WC and Co steps during mixing and compaction prior to sintering of the composite. (author)

  14. Structural analysis of a carbonated hydroxyapatite by the Rietveld method using different profile functions; Analise estrutural de uma hidroxiapatita carbonatada pelo metodo de Rietveld aplicando funcoes de perfil diferentes

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Jorge C. de [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Dept. de Matematica], e-mail: jcaraujo@iprj.uerj.br; Moreira, Elizabeth L.; Moraes, Valeria Conde Alves [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)], e-mail: beth@cbpf.br, e-mail: conde@cbpf.br; Moreira, Ana Paula D. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Quimica. Dept. de Quimica Analitica], e-mail: duarteap@gmail.com

    2008-10-15

    The crystal structure of the synthetic hydroxyapatite with 12.8 ({+-} 0,64) wt. % CO{sub 3}{sup 2-} ion content was analyzed by X-ray diffraction using the Rietveld refinement method employing Pearson VII and pseudo-Voigt functions to fit the X-ray profile. The results obtained for unit cell parameters when compared to pattern hydroxyapatite showed a decrease in the a (=b) parameter and an increase in the c parameter without significant difference between the functions employed. The separation of the anisotropic broadening of reflections originated from unit cell strains indicated that this effect is dominant in reflection line broadening, principally to hkl plans with an interatomic distance lower than 2,24 angstrom. Modifications in the atomic coordinates of C atom were noted mainly in PO{sub 4}{sup 3-} (B site) and OH{sup -} (A site) sites. The average crystallite size in the crystallography axis directions (002 and 300) suggests equi axial morphology. The results obtained to CO{sub 3}{sup 2}- content were 11.72 ({+-} 0,64) wt. % to Pearson VII and 13.20 ({+-} 0,64) wt. % to pseudo-Voigt function. The refinement of the occupancy factors to C atoms in both sites PO{sub 4}{sup 3-}(B) and OH{sup -} (A) indicated higher insertion in phosphate site than hydroxide site. However, the relative occupancy of the C atom observed in the B site is lower than in the A site. (author)

  15. Quantitative study of Portland cement hydration by X-ray diffraction/Rietveld analysis and independent methods

    International Nuclear Information System (INIS)

    Scrivener, K.L.; Fuellmann, T.; Gallucci, E.; Walenta, G.; Bermejo, E.

    2004-01-01

    X-ray diffraction (XRD) is a powerful technique for the study of crystalline materials. The technique of Rietveld refinement now enables the amounts of different phases in anhydrous cementitious materials to be determined to a good degree of precision. This paper describes the extension of this technique to a pilot study of the hydration of a typical Portland cement. To validate this XRD-Rietveld analysis technique, its results were compared with independent measures of the same materials by the analysis of backscattered electron images (BSE/IA) and thermogravimetric analysis (TGA). In addition, the internal consistency of the measurements was studied by comparing the XRD estimates of the amounts of hydrates formed with the amounts expected to form from the XRD estimates of the amounts of anhydrous materials reacted

  16. Rietveld refinement of the structures of 1.0 C-S-H and 1.5 C-S-H

    KAUST Repository

    Battocchio, Francesco

    2012-11-01

    Low-Q region Rietveld analyses were performed on C-S-H synchrotron XRD patterns, using the software MAUD. Two different crystal structures of tobermorite 11 Å were used as a starting model: monoclinic ordered Merlino tobermorite, and orthorhombic disordered Hamid tobermorite. Structural modifications were required to adapt the structures to the chemical composition and the different interlayer spacing of the C-S-H samples. Refinement of atomic positions was done by using special constraints called fragments that maintain interatomic distances and orientations within atomic polyhedra. Anisotropic crystallite size refinement showed that C-S-H has a nanocrystalline disordered structure with a preferred direction of elongation of the nanocrystallites in the plane of the Ca interlayer. The quality of the fit showed that the monoclinic structure gives a more adequate representation of C-S-H, whereas the disordered orthorhombic structure can be considered a more realistic model if the lack of long-range order of the silica chain along the c-direction is assumed. © 2012 Elsevier Ltd. All rights reserved.

  17. Rietveld analysis, powder diffraction and cement

    International Nuclear Information System (INIS)

    Peterson, V.

    2002-01-01

    Full text: Phase quantification of cement is essential in its industrial use, however many methods are inaccurate and/or time consuming. Powder diffraction is one of the more accurate techniques used for quantitative phase analysis of cement. There has been an increase in the use of Rietveld refinement and powder diffraction for the analysis and phase quantification of cement and its components in recent years. The complex nature of cement components, existence of solid solutions, polymorphic variation of phases and overlapping phase peaks in diffraction patterns makes phase quantification of cements by powder diffraction difficult. The main phase in cement is alite, a solid solution of tricalcium silicate. Tricalcium silicate has been found to exist in seven modifications in three crystal systems, including triclinic, monoclinic, and rhombohedral structures. Hence, phase quantification of cements using Rietveld methods usually involves the simultaneous modelling of several tricalcium silicate structures to fit the complex alite phase. An industry ordinary Portland cement, industry and standard clinker, and a synthetic tricalcium silicate were characterised using neutron, laboratory x-ray and synchrotron powder diffraction. Diffraction patterns were analysed using full-profile Rietveld refinement. This enabled comparison of x-ray, neutron and synchrotron data for phase quantification of the cement and examination of the tricalcium silicate. Excellent Rietveld fits were achieved, however the results showed that the quantitative phase analysis results differed for some phases in the same clinker sample between various data sources. This presentation will give a short introduction about cement components including polymorphism, followed by the presentation of some problems in phase quantification of cements and the role of Rietveld refinement in solving these problems. Copyright (2002) Australian X-ray Analytical Association Inc

  18. Strain and stress tensors of rolled uranium plate by Rietveld refinement of TOF neutron-diffraction data

    International Nuclear Information System (INIS)

    Balzar, D.; Popa, N.C.; Vogel, S.

    2010-01-01

    We report the complete macroscopic average strain and stress tensors for a cold-rolled uranium plate, based on the neutron TOF measurements. Both tensors were determined by the least-squares refinement of the interplanar spacings of 19 Bragg reflections. Based on the pole figures, as determined by GSAS, a triclinic sample symmetry of the uranium plate was assumed. Strain and stress are tensile in both the transverse and rolling directions and very small in the normal direction (through the thickness of the plate). Shear strain and stress components are compressive and of significant magnitude.

  19. Application of the Rietveld method in structural analysis of catalysts based on CuO/CeO{sub 2}; Aplicacao do metodo de Rietveld na analise estrutural de catalisadores a base de CuO/CeO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Simoes, A.N.; Gama, L., E-mail: lsoutoneiva@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais

    2011-07-01

    This work has as aim to synthesize catalysts composed by CuO/CeO{sub 2} by means two distinct methods of synthesis, they are: combustion synthesis and Pechini. The catalysts composed by CuO/CeO{sub 2} were synthesized with CuO in condition of dopant element. The value of the CuO concentration ranged between 0 and 0.5 mol. Has been done a structural analysis related to how the kind of synthesis method used influences over physical characteristic of the catalytic material. The obtained catalysts were characterized by X-ray diffraction with refinement by Rietveld method. According to results, the synthesized catalysts showed crystalline structures formed mostly by CeO{sub 2} phase, as expected, since this is the host matrix for the dopant element. The catalysts obtained by the Pechini method presented structures with a smaller amount of segregated phases formed by CuO, according to the results of the structural analysis. (author)

  20. Rietveld refinement of the crystal structure of perovskite solar cells using CH3NH3PbI3 and other compounds

    Science.gov (United States)

    Ando, Yuji; Ohishi, Yuya; Suzuki, Kohei; Suzuki, Atsushi; Oku, Takeo

    2018-01-01

    The crystal structures of perovskite thin films including CH3NH3PbI3, CH3NH3Pb1-xSbxI3, and CH3NH3PbI3-yCly in the solar cell configuration were studied by using Rietveld refinement. For the CH3NH3PbI3 and CH3NH3Pb1-xSbxI3 samples, satisfactory agreement with the measured profiles was obtained with a weighted profile R-factor (Rwp) of as low as 3%. It was shown that the site occupancy of methylammonium (MA) was decreased in the antimonized cell due to the compensation effect of an increased positive charge brought about by replacing Pb2+ with Sb3+. Photovoltaic measurements showed that the power conversion efficiency was enhanced by adding a small amount of Sb to the CH3NH3PbI3 cell, but it was monotonically decreased as the mole fraction of Sb exceeded 0.03. This variation of the conversion efficiency was considered as a result of suppressed crystallization of PbI2 and carrier recombination via MA vacancies in the antimonized cells. In the case of CH3NH3PbI2.88Cl0.12 sample, the agreement with the measured profile with an Rwp of as high as 7% suggested the co-existence of cubic and tetragonal phases in the chlorinated cell.

  1. Rietveld refinement, dielectric and magnetic properties of Nb modified Bi0.80Ba0.20FeO3 ceramic

    Science.gov (United States)

    Jangra, Sandhaya; Sanghi, Sujata; Agarwal, Ashish; Rangi, Manisha

    2018-05-01

    Bi0.80Ba0.20Fe0.95Nb0.05O3 ceramic has been prepared via conventional solid state reaction method. Structure analysis was carried out by X-ray diffraction (XRD) technique at room temperature. XRD pattern confirmed the crystalline nature of prepared sample. Rietveld analysis used for further structural investigations and confirmed the existence of rhombohedral symmetry (R3c space group). The dielectric response shows dispersion at lower frequency range and becomes frequency independent at high frequency. The approximation of conduction mechanism is determined by the temperature dependent behavior of frequency exponent `s'. Fitting results suggests the applicability of small polaron conduction mechanism at lower temperatures and CBH model at higher temperature. Room temperature magnetic measurements give the evidence of significant enhancement in magnetic properties with remanent magnetization (Mr = 0.1218 emu/g) and coercive field (Hc = 3.5342 kOe).

  2. Quantitative phase analysis of alumina/calcium-hexaluminate composites using neutron diffraction data and the Rietveld method

    International Nuclear Information System (INIS)

    Asmi, D.; Low, I.M.; O'Connor, B.H.; Kennedy, S.J.

    2000-01-01

    Full text: The Al 2 O 3 -CaO system is the basis of an important class of high-temperature refractories in the steel industry. It contains a number of stable intermediate compounds which include C 3 A, C 12 A 7 , CA, CA 2 , and CA 6 . These calcium aluminates are also important constituents of high alumina cement and have been used to produce high-strength and high-toughness ceramic-polymer composite materials. More recently, alumina composites containing 30 wt% CA 6 platelets have been developed by An et al which show characteristics of self-reinforcement and enhanced toughening through crack-bridging. In this paper, we describe the use of high-temperature neutron diffraction to monitor the in-situ phase formation and abundances of calcium aluminates (CA, CA 2 , and CA 6 ) in alumina composites containing 5-50 wt % CA 6 .at temperatures in the range 1000 - 1600 deg C. These composites were produced using reaction sintering of alumina and calcium oxide. For comparison purposes, control samples of pure α-alumina and CA 6 were also produced. Determination of relative phase abundances in these materials has been performed using the standardless Rietveld refinement method. Results show that the relative phase abundance of calcium aluminates in the composites increased with temperature and in proportion with the amount of calcium oxide present. The formation temperatures of CA, CA 2 , and CA 6 have been observed to occur at 1000 deg , 1200 deg, and ∼1350 deg C respectively, which agree well with results obtained from x-ray diffraction, synchrotron radiation diffraction and differential thermal analysis

  3. PETROGRAPHY AND APPLICATION OF THE RIETVELD METHOD TO THE QUANTITATIVE ANALYSIS OF PHASES OF NATURAL CLINKER GENERATED BY COAL SPONTANEOUS COMBUSTION

    Directory of Open Access Journals (Sweden)

    Pinilla A. Jesús Andelfo

    2010-06-01

    Full Text Available

    Fine-grained and mainly reddish color, compact and slightly breccious and vesicular pyrometamorphic rocks (natural clinker are associated to the spontaneous combustion of coal seams of the Cerrejón Formation exploited by Carbones del Cerrejón Limited in La Guajira Peninsula (Caribbean Region of Colombia. These rocks constitute remaining inorganic materials derived from claystones, mudstones and sandstones originally associated with the coal and are essentially a complex mixture of various amorphous and crystalline inorganic constituents. In this paper, a petrographic characterization of natural clinker, aswell as the application of the X-ray diffraction (Rietveld method by mean of quantitative analysis of its mineral phases were carried out. The RIQAS program was used for the refinement of X ray powder diffraction profiles, analyzing the importance of using the correct isostructural models for each of the existing phases, which were obtained from the Inorganic Crystal Structure Database (ICSD. The results obtained in this investigation show that the Rietveld method can be used as a powerful tool in the quantitative analysis of phases in polycrystalline samples, which has been a traditional problem in geology.

  4. Quantitative determination of phases in ZrO2 (MgO) (Y2O3) using the Rietveld method

    International Nuclear Information System (INIS)

    Castro, Antonio Carlos de

    2007-01-01

    The key objective of this work is the crystallographic characterization of the zircon co-doped with Yttria and magnesium with the application of the Rietveld method for quantitative phase analysis of zircon polymorph (zircon monoclinic, tetragonal, and cubic). Samples of zircon polymorph were obtained from zircon doped with Yttria and magnesium at defined molar concentrations. The zircon polymorph stability during subeutetoid aging at 1350 deg C were investigated to determine ZrO 2 - MgO - Y 2 0 3 phases degradation and to define the solid solutions stability environment. ZrO 2 powders doped with 8 mol por cent of MgO and 1 mol por cent of Y 2 O 3 , and 9 mol por cent of MgO and 0 mol por cent of Y 2 O 3 have been prepared by chemical route using the co-precipitation method. These samples have been calcinate at 550 deg C, sintered at 1500 deg C and characterized by the Rietveld method using the X-ray diffraction data. The variation of the lattice parameter, changes in the phase composition and their microstructures are discussed. The application of the Rietveld method for quantitative phase analysis of zircon polymorph (zircon tetragonal and cubic) reveals no formation of tetragonal phase and indicating that the matrix is the cubic phase with low concentration of monoclinic phase.(author)

  5. Rietveld refinement of the structures of 1.0 C-S-H and 1.5 C-S-H

    KAUST Repository

    Battocchio, Francesco; Monteiro, Paulo J.M.; Wenk, Hans-Rudolf

    2012-01-01

    Low-Q region Rietveld analyses were performed on C-S-H synchrotron XRD patterns, using the software MAUD. Two different crystal structures of tobermorite 11 Å were used as a starting model: monoclinic ordered Merlino tobermorite, and orthorhombic

  6. Application of the Rietveld method in powders of strontium-doped lanthanum manganite calcined in different temperatures

    International Nuclear Information System (INIS)

    Chiba, R.; Vargas, R.A.; Martinez, L.G.; Andreoli, M.; Seo, E.S.M.

    2010-01-01

    The strontium-doped lanthanum manganite (LSM) is a ceramic material used as cathode in device called High Temperature Solid Oxide Fuel Cell. In this work, the LSM was synthesized by the citrate technique with the objective to get powders without the formation of secondary phases, such as lanthanum oxide and the lanthanum hydroxide, harmful for the functional performance of the device. The definitive calcination temperatures had been 700, 900 and 1100 deg C, due the decomposition of the polymeric precursors to present stabilization from 480 deg C. The analysis by X-ray diffraction of the calcined powders in different temperatures shows the formation only of phase LSM of hexagonal crystalline structure, type pseudo-perovskite. Using the refinement of Rietveld was determined the parameters and volumes of unity cells, atomic positions and occupations. These results confirm that the chemical compositions obtained are similar to the nominal. (author)

  7. A research of the mineralogy phases of clinker in a spanish cement using the method of Rietveld

    International Nuclear Information System (INIS)

    Castanon, Ana M; Garcia, Granda Santiago; Guerrero, Ana M; Gomez Fernandez, Fernando

    2012-01-01

    In order to introduce continuously a quality control method in a Spanish cement factory to improve the final product feature new research methodology is being developed. The Rietveld method [1] has been successfully used to analyze the composition of the main phases of clinker. Using this methodologies, research has been carried out to quantize appropriately the minor phase of free lime which is extremely important in the clinker quality. This method leads to satisfactory results on samples with contents in CaO from 3%. These results are possible combining X- ray diffraction and fluorescence techniques as well as the chemical analysis data.

  8. A method for refining oil

    Energy Technology Data Exchange (ETDEWEB)

    Bruskin, Yu.A.; Gorokhov, V.V.; Kotler, L.D.; Kovalenko, N.F.; Spasskiy, Yu.B.; Titov, A.M.; Vlasenko, V.Ye.; Vytnov, V.A.

    1983-01-01

    In the method for refining oil through its distillation with the isolation of directly distilled gases and a benzine fraction (BS) with the use of a benzine fraction pyrolysis, in order to increase the output of the lower olefines and to reduce the energy expenditures, the distillation is conducted with the isolation of 10 to 40 percent of the benzine fraction from its potential content along with the directly distilled gases. The obtained mixture of the remaining part of the benzine fraction is absorbed at a pressure of 1.5 to 6 atmospheres with the feeding of the obtained saturated absorbent to pyrolysis and subsequent mixing of the obtained pyrolysis gas with the unabsorbed product and their joint gas division. As compared to the known method, the proposed method makes it possible to reduce the energy expenditures which is achieved through a reduction in the volume of irrigation in the tower, and to increase the output of the olefines through processing of the steam and gas mixture of the benzine and the directly distilled gases.

  9. Mineralogical characterization of a highly-weathered soil by the Rietveld Method Caracterização mineralógica de um solo altamente intemperizado pelo Método de Rietveld

    Directory of Open Access Journals (Sweden)

    André Maurício Brinatti

    2010-08-01

    Full Text Available The mineralogical characterization through mineral quantification of Brazilian soils by X-ray diffraction data using the Rietveld Method is not common. A mineralogical quantification of an Acric Ferralsol from the Ponta Grossa region, state of Paraná, Brazil, was carried out using this Method with X-Ray Diffraction data to verify if this method was suitable for mineral quantification of a highly-weathered soil. The A, AB and B3 horizons were fractioned to separate the different particle sizes: clay, silt, fine sand (by Stokes Law and coarse sand fractions (by sieving, with the procedure free of chemical treatments. X-ray Fluorescence, Inductively Coupled Plasma Atomic Emission Spectrometry, Infrared Spectroscopy and Mössbauer Spectroscopy were used in order to assist the mineral identification and quantification. The Rietveld Method enabled the quantification of the present minerals. In a general way, the quantitative mineralogical characterization by the Rietveld Method revealed that quartz, gibbsite, rutile, hematite, goethite, kaolinite and halloysite were present in the clay and silt fractions of all horizons. The silt fractions of the deeper horizons were different from the more superficial ones due to the presence of large amounts of quartz. The fine and the coarse sand fractions are constituted mainly by quartz. Therefore, a mineralogical quantification of the finer fraction (clay and silt by the Rietveld Method was successful.A caracterização mineralógica por meio da quantificação dos minerais presentes em solos brasileiros por difração de raios X usando o Método de Rietveld é, ainda, pouco comum. Neste trabalho foi realizada a quantificação mineralógica de um Latossolo Vermelho ácrico da região de Ponta Grossa, Paraná, Brasil, utilizando o Método de Rietveld com dados de Difração de Raios X e também verificado se o método foi adequado na quantificação mineral de um solo altamente intemperizado. Os horizontes A

  10. Rietveld analysis system RIETAN (translation)

    International Nuclear Information System (INIS)

    Izumi, Fujio

    1991-09-01

    This is the manual of the RIETAN system (a Rietveld analysis program) which is originally written in Japanese by Fujio Izumi. The manual consists of two parts. Part I is a general description of the fundamental concepts and methods of the RIETAN system. Part II is the user's manual of the RIETAN which mainly describes in detail how to create user's data sets, procedures of Rietveld analysis and how to read the results of analysis. (author)

  11. Homogeneity characterisation of (U,Gd)O2 sintered pellets by X-ray diffraction powder analysis applying Rietveld method

    International Nuclear Information System (INIS)

    Leyva, Ana G.; Vega, Daniel R.; Trimarco, Veronica G.; Marchi, Daniel E.

    1999-01-01

    The (U,Gd)O 2 sintered pellets are fabricated by different methods. The homogeneity characterisation of Gd content seems to be necessary as a production control to qualify the process and the final product. The micrographic technique is the most common method used to analyse the homogeneity of these samples, this method requires time and expertise to obtain good results. In this paper, we propose an analysis of the X-ray diffraction powder patterns through the Rietveld method, in which the differences between the experimental data and the calculated from a crystalline structure model proposed are evaluated. This result allows to determine the cell parameters, that can be correlated with the Gd concentration, and the existence of other phases with different Gd ratio. (author)

  12. Rietveld analysis using powder diffraction data with anomalous scattering effect obtained by focused beam flat sample method

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Masahiko, E-mail: masahiko@spring8.or.jp; Katsuya, Yoshio, E-mail: katsuya@spring8.or.jp; Sakata, Osami, E-mail: SAKATA.Osami@nims.go.jp [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

    2016-07-27

    Focused-beam flat-sample method (FFM) is a new trial for synchrotron powder diffraction method, which is a combination of beam focusing optics, flat shape powder sample and area detectors. The method has advantages for X-ray diffraction experiments applying anomalous scattering effect (anomalous diffraction), because of 1. Absorption correction without approximation, 2. High intensity X-rays of focused incident beams and high signal noise ratio of diffracted X-rays 3. Rapid data collection with area detectors. We applied the FFM to anomalous diffraction experiments and collected synchrotron X-ray powder diffraction data of CoFe{sub 2}O{sub 4} (inverse spinel structure) using X-rays near Fe K absorption edge, which can distinguish Co and Fe by anomalous scattering effect. We conducted Rietveld analyses with the obtained powder diffraction data and successfully determined the distribution of Co and Fe ions in CoFe{sub 2}O{sub 4} crystal structure.

  13. Rietveld analysis using powder diffraction data with anomalous scattering effect obtained by focused beam flat sample method

    International Nuclear Information System (INIS)

    Tanaka, Masahiko; Katsuya, Yoshio; Sakata, Osami

    2016-01-01

    Focused-beam flat-sample method (FFM) is a new trial for synchrotron powder diffraction method, which is a combination of beam focusing optics, flat shape powder sample and area detectors. The method has advantages for X-ray diffraction experiments applying anomalous scattering effect (anomalous diffraction), because of 1. Absorption correction without approximation, 2. High intensity X-rays of focused incident beams and high signal noise ratio of diffracted X-rays 3. Rapid data collection with area detectors. We applied the FFM to anomalous diffraction experiments and collected synchrotron X-ray powder diffraction data of CoFe_2O_4 (inverse spinel structure) using X-rays near Fe K absorption edge, which can distinguish Co and Fe by anomalous scattering effect. We conducted Rietveld analyses with the obtained powder diffraction data and successfully determined the distribution of Co and Fe ions in CoFe_2O_4 crystal structure.

  14. Crystal structures of new cuprates containing CO3 analyzed by the Rietveld method of neutron powder diffraction

    International Nuclear Information System (INIS)

    Miyazaki, Y.; Yamane, H.; Kajitani, T.; Hiraga, K.; Hirai, T.; Morii, Y.; Funahashi, S.

    1993-01-01

    New compounds containing CO 3 groups, Sr 2 CuO 2 (CO 3 ), (C 0.4 Cu 0.6 )Sr 2 (Y 0.86 Sr 0.14 )Cu 2 O 7 and (C 0.35 Cu 0.65 )Sr 2 (Y 0.73 Ce 0.27 ) 2 Cu 2 O 9 , were prepared as stable phases at 1273-1303 K in a flowing gas of O 2 -CO 2 . The crystal structures of these compounds were refined by means of the Rietveld analysis for neutron powder diffraction data collected using a high resolution powder diffractometer (HRPD) in the JRR-3M reactor hall of the Japan Atomic Energy Research Institute (JAERI). Positions of CO 3 groups were satisfactorily determined. The distances of C-O bonds in the CO 3 groups were around 1.3A and the O-C-O angles were almost equal to the ideal bond angle of 120deg. (author)

  15. Synthesis of Zr-Si-O-N phases by carbonitriding reaction. Characterization of crystalline phases using the Rietveld method

    Directory of Open Access Journals (Sweden)

    Mazzoni A.D.

    2001-01-01

    Full Text Available Zirconium compounds are of great interest for ceramic application due to their excellent thermal and mechanical properties. Zirconium phases of the system Zr-O-C-N were obtained using carbonitriding reactions of zircon mineral (ZrO2.SiO2, under different reaction conditions. The reaction products were studied by X-ray diffraction (XRD using the Rietveld method. Silicon was employed as internal standard. Zirconium compounds formed were m-ZrO2 (monoclinic, beta"-zirconium oxynitride and a cubic Zr(C,N,O phase whose lattice parameter a o depends on the composition. The crystallite sizes of the three zirconium phases were determined also by XRD. The minority phases present are the ones of the Si-O-N-C system. The reaction conditions employed allows to obtain reaction products with low or without silicon content.

  16. Structural determination of new solid solutions [Y2-x Mx ][Sn2-x Mx ]O7-3x/2 (M = Mg or Zn by Rietveld method

    Directory of Open Access Journals (Sweden)

    Mohamed Douma

    2010-12-01

    Full Text Available New [Y2-x Mx][Sn2-x Mx]O7-3x/2 (0 ≤x≤ 0.30 for M = Mg and 0 ≤x≤ 0.36 for M = Zn solid solutions with the pyrochlore structure were synthesized via high-temperature solid-state reaction method. Powder X-ray diffraction (PXRD patterns and Fourier transform infrared (FT-IR spectra showed that these materials are new non-stoichiometric solid solutions with the pyrochlore type structure. The structural parameters for the solids obtained were successfully determined by Rietveld refinement based on the analysis of the PXRD diagrams. Lattice parameter (a of these solid solutions decreases when x increases in both series. All samples obtained have the pyrochlore structure Fd-3m, no. 227 (origin at center -3m with M2+ (M = Mg2+ or Zn2+ cations in Y3+ and Sn4+ sites, thus creating vacancies in the anionic sublattice.

  17. Influence of diopside: feldspar ratio in ceramic reactions assessed by quantitative phase analysis (X-ray diffraction - Rietveld method)

    International Nuclear Information System (INIS)

    Kuzmickas, L.; Andrade, F.R.D.; Szabo, G.A.J.; Motta, J.F.M.; Cabral Junior, M.

    2013-01-01

    White ceramics were produced with raw mixtures prepared with varying proportions of diopside-rich rock (0 to 20 wt.%) and potassic feldspar (40 to 20 wt.%), and fixed proportions of kaolinite (40 wt.%) and quartz (20 wt.%), fired in a temperature range from 1170 to 1210 deg C. The phases identified in the experimental ceramics were quartz, anorthite, mullite and glass, and their relative mass proportions were determined by X-ray diffraction (Rietveld method). The addition of diopside as a partial substitute for potassic feldspar causes the formation of a calcium silicate, analogous of the natural anorthite (CaSi 2 Al 2 O 8 ) in the ceramics, with proportional reduction in its glass and mullite contents. Water absorption and porosity of the ceramic bodies clearly decrease with increasing firing temperature, while the effect of the raw mixture composition on the physical and mechanical properties of the ceramics is less evident. Diopside-rich rock has low iron content (1.5 wt.% Fe 2 O 3 ) and, therefore, promotes white burning. (author)

  18. Influence of diopside: feldspar ratio in ceramic reactions assessed by quantitative phase analysis (X-ray diffraction - Rietveld method)

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmickas, L.; Andrade, F.R.D.; Szabo, G.A.J. [Universidade de Sao Paulo (IGc/USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotecnia; Motta, J.F.M.; Cabral Junior, M., E-mail: lukuzmickas@gmail.com, E-mail: dias@usp.br, E-mail: gajszabo@usp.b, E-mail: motta.jf@gmail.com, E-mail: marsis@ipt.br [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil). Secao de Recursos Minerais e Tecnologia Ceramica

    2013-04-15

    White ceramics were produced with raw mixtures prepared with varying proportions of diopside-rich rock (0 to 20 wt.%) and potassic feldspar (40 to 20 wt.%), and fixed proportions of kaolinite (40 wt.%) and quartz (20 wt.%), fired in a temperature range from 1170 to 1210 deg C. The phases identified in the experimental ceramics were quartz, anorthite, mullite and glass, and their relative mass proportions were determined by X-ray diffraction (Rietveld method). The addition of diopside as a partial substitute for potassic feldspar causes the formation of a calcium silicate, analogous of the natural anorthite (CaSi{sub 2}Al{sub 2}O{sub 8}) in the ceramics, with proportional reduction in its glass and mullite contents. Water absorption and porosity of the ceramic bodies clearly decrease with increasing firing temperature, while the effect of the raw mixture composition on the physical and mechanical properties of the ceramics is less evident. Diopside-rich rock has low iron content (1.5 wt.% Fe{sub 2}O{sub 3}) and, therefore, promotes white burning. (author)

  19. Crystal structure refinement of Ba5Nb4O15 and Ba5Nb4O15-x by Rietveld analysis of neutron and X-ray diffraction data

    International Nuclear Information System (INIS)

    Pagola, S.; Leyva, G.; Casais, M.T.; Alonso, J.A.; Rasines, I.; Carbonio, R.E.

    1996-01-01

    Both X-ray and neutron diffraction data were analyzed by the Rietveld method, taking as starting structural model that of the Ba 5 Ta 4 O 15 structure. The results of such an analysis show that the progressive elimination of oxygen ions produce only small changes in the structure. A decrease in the unit-cell parameters as the number of oxygen vacancies increases has been observed, which can be correlated with a gradual loss of oxygen ions in the close-packed layers. No ordering of the oxygen vacancies was found even in the sample with the highest x value, x=0.56. (orig.)

  20. X-ray diffraction analysis of stan nite, wurtz-stan nite and pseudo-cubic quaternary compounds by Rietveld method

    Energy Technology Data Exchange (ETDEWEB)

    Quintero, M.; Quintero, E.; Moreno, E.; Alvarez, S.; Rincon, C.; Grima, P.; Bocaranda, P.; Rivero, D. [Universidad de Los Andes, Centro de Estudios de Semiconductores, 5101 Merida (Venezuela, Bolivarian Republic of); Marquina, J. [Universidad de Los Andes, Centro de Estudios Avanzados en Optica, 5101 Merida (Venezuela, Bolivarian Republic of); Henao, J. A.; Macias, M. A., E-mail: mquinterg@gmail.com [Universidad Industrial de Santander, Facultad de Ciencias, Escuela de Quimica, Grupo de Investigacion en Quimica Estructural, Apdo. Aereo 678, Bucaramanga (Colombia)

    2014-07-01

    Room temperature X-ray powder diffraction measurements were carried out on nine polycrystalline samples of the Cu{sub 2}B{sup II}C{sup IV}X{sub 4} (B=Mn, or Fe, or Co; C=Si, or Ge, or Sn; X=S, or Se or Te) magnetic semiconductor compounds. The diffraction patterns were used to show the equilibrium conditions and to derive crystalline parameters values. The results showed that four of these compounds have a tetragonal stan nite structure with space group 142 m(N{sup o} 121), two and orthorhombic wurtz-stan nite structure with space group Pmn2{sub 1}(N{sup o} 31) and three of them and orthorhombic pseudo-cubic structure with space group F222 (N{sup o} 22). In each case, the structure was refined using the Rietveld method. When the obtained atomic parameter values for the tetragonal compounds were plotted as a function of molecular weight W, it was found that the values of the atomic positions, the cation-anion bond distances, tetragonal distortion and internal distortion of the compounds containing S and /or Se lay on different lines. Also, it was found that when the experimental points of the cation-anion bond distances d{sub Cu-VI}, d{sub II-VI} and d{sub IV-VI} were plotted against the effective lattice parameter a{sub c} = (V/N){sup 1/3}, a linear variation of these distances with a{sub c} was obtained. Values of the ionic energy gap C{sub i} and homopolar energy gap E{sub h} using the Phillips-Van Vechten scheme, with the present experimental crystallographic results as well as using the atomic data, were determined. It was found that the observed and predicted values of C{sub i} and E{sub h} lie on the same straight line. (Author)

  1. A Study on the quantification of hydration and the strength development mechanism of cementitious materials including amorphous phases by using XRD/Rietveld method

    International Nuclear Information System (INIS)

    Yamada, Kazuo; Hoshino, Seiichi; Hirao, Hiroshi; Yamashita, Hiroki

    2008-01-01

    X-ray diffraction (XRD)/Rietveld method was applied to measure the phase composition of cement. The quantative analysis concerning the progress of hydration was accomplished in an error of about the maximum 2-3% in spite of including amorphous materials such as blast furnace slag, fly ash, silica fume and C-S-H. The influence of the compressive strength on the lime stone fine powder mixture material was studied from the hydration analysis by Rietveld method. The two stages were observed in the strength development mechanism of cement; the hydration promotion of C 3 S in the early stage and the filling of cavities by carbonate hydrate for the longer term. It is useful to use various mixture materials for the formation of the resource recycling society and the durability improvement of concrete. (author)

  2. Rare earths refining by vacuum sublimation method

    International Nuclear Information System (INIS)

    Rytus, N.N.

    1983-01-01

    The process of rare earths refining by the sUblimation; method in high and superhigh oil-free vacuum, is investigated. The method is effective for rare earths obtaining and permits to prepare metal samples with a high value of electric resistance ratio γ=RsUb(298 K)/Rsub(4.2 K). The estimation of general purity is performed for Sm, Eu, Yb, Tm, Dy, Ho, Er and Se

  3. Assessment of firing conditions in old fired-clay bricks. The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering

    Czech Academy of Sciences Publication Activity Database

    Viani, Alberto; Sotiriadis, Konstantinos; Len, A.; Šašek, Petr; Ševčík, Radek

    2016-01-01

    Roč. 116, June (2016), s. 33-43 ISSN 1044-5803 R&D Projects: GA MŠk(CZ) LO1219 Keywords : fired- clay brick * Rietveld method * small angle neutron scattering * X-ray diffraction * firing temperature Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.714, year: 2016 http://www.sciencedirect.com/science/article/pii/S1044580316300870

  4. Quantitative phase analysis of a highly textured industrial sample using a Rietveld profile analysis

    International Nuclear Information System (INIS)

    Shin, Eunjoo; Huh, Moo-Young; Seong, Baek-Seok; Lee, Chang-Hee

    2001-01-01

    For the quantitative phase analysis on highly textured two-phase materials, samples with known weight fractions of zirconium and aluminum were prepared. Strong texture components prevailed in both zirconium and aluminum sheet. The diffraction patterns of samples were measured by the neutron and refined by the Rietveld method. The preferred orientation correction of diffraction patterns was carried out by means of recalculated pole figures from the ODF. The present Rietveld analysis of various samples with different weight fractions showed that the absolute error of the calculated weight fractions was less than 7.1%. (author)

  5. Profile agreement indices in Rietveld and pattern-fitting analysis

    International Nuclear Information System (INIS)

    Hill, R.J.; Fischer, R.X.

    1990-01-01

    Two definitions of profile agreement indices are now in common use for estimating the degree of fit in Rietveld refinement and in structure-independent pattern-fitting methods of powder diffraction analysis. In the original program written by Rietveld, the background was subtracted and the 'non-peak' regions of the pattern were removed from further consideration in a preliminary data-reduction stage prior to structure refinement. However, the agreement indices used in many of the more recent programs retain the background counts in the observed step intensities and include all portions of the pattern in the sums. These latter definitions are strongly dependent on the signal-to-noise ratio and on the relative amount of 'background-only' regions and do not, therefore, provide a sound basis for comparing the degree of fit of peak profile and crystal structure model refinements in the general case. The extent of this dependence is illustrated quantitatively using conventional and synchrotron X-ray and constant-wavelength and time-of-flight neutron data sets with different inherent background levels and peak densities. The unweighted background-corrected peak-only profile agreement index R' p =Σ i vertical strokeY io -Y ic vertical stroke/Σ i vertical strokeY io -Y ib vertical stroke (and, to a lesser extent, its weighted equivalent) is recommended as the most appropriate criterion of fit for comparative work between diffraction patterns of all kinds. (orig.)

  6. Assessment of firing conditions in old fired-clay bricks: The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Viani, Alberto, E-mail: viani@itam.cas.cz [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic); Sotiriadis, Konstantinos [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic); Len, Adél [Wigner Research Centre for Physics HAS, Konkoly-Thege 29-33, 1121 Budapest (Hungary); Šašek, Petr; Ševčík, Radek [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic)

    2016-06-15

    Full characterization of fired-clay bricks is crucial for the improvement of process variables in manufacturing and, in case of old bricks, for restoration/replacement purposes. To this aim, five bricks produced in a plant in Czech Republic in the past have been investigated with a combination of analytical techniques in order to derive information on the firing process. An additional old brick from another brickyard was also used to study the influence of different raw materials on sample microstructure. The potential of X-ray diffraction with the Rietveld method and small angle neutron scattering technique has been exploited to describe the phase transformations taking place during firing and characterize the brick microstructure. Unit-cell parameter of spinel and amount of hematite are proposed as indicators of the maximum firing temperature, although for the latter, limited to bricks produced from the same raw material. The fractal quality of the surface area of pores obtained from small angle neutron scattering is also suggested as a method to distinguish between bricks produced from different raw clays. - Highlights: • Rietveld method helps in describing microstructure and physical properties of bricks. • XRPD derived cell parameter of spinel is proposed as an indicator of firing temperature. • SANS effectively describes brick micro and nanostructure, including closed porosity. • Fractal quality of pore surface is proposed as ‘fingerprint’ of brick manufacturing.

  7. Rietveld refinement of the orthorhombic Pbca structures of Rb2CdSi5O12, Cs2MnSiO5O12, Cs2CoSi5O12 and Cs2NiSi5O12 leucites by synchrotron X-ray powder diffraction

    International Nuclear Information System (INIS)

    Bell, A.M.T.; Henderson, C.M.B.

    1996-01-01

    Analysis of high-resolution synchrotron X-ray powder diffraction patterns for hydrothermally synthesized Rb 2 CdSi 5 O 12 and Cs 2 MnSi 5 O 12 leucite analogues, and dry-synthesized Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite analogues showed that they have an orthorhombic Pbca structure. The structures have been refined by the Rietveld method, showing that the tetrahedrally coordinated atoms (Si, Cd, Mn, Co and Ni) are ordered on separate sites. The Cs 2 MnSi 5 O 12 , Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite samples are unusual in containing SiO 4 tetrahedra which are more distorted, on average, than the larger MnO 4 , CoO 4 and NiO 4 tetrahedra. The JCPDS file numbers for Rb 2 CdSi 5 O 12 , Cs 2 MnSi 5 O 12 and Cs 2 CoSi 5 O 12 are 46-1491, 46-1492 and 46-1493, respectively. (orig.)

  8. Rietveld refinement and dielectric properties of (Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kaswan, Kavita, E-mail: kaswan.kavita@gmail.com; Agarwal, Ashish; Sanghi, Sujata; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar-125001 (India)

    2015-06-24

    (1-x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-x(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) lead free ceramics (NBT, NBT-BBFO; x = 0.0, 0.1 respectively) have been synthesized by conventional solid state reaction method. Crystalline phase of sintered ceramics was investigated at room temperature using X-ray diffraction. Rietveld refinement of XRD data performed by FullProf revealed that both the samples exhibited rhombohedral structure with R3c space group. Dielectric properties of these ceramics were studied at different temperatures in a wide frequency range using impedance analyzer. Dielectric constant and dielectric loss were found to be increase with increase of BBFO content. The prepared ceramics exhibit a broad maximum in dielectric permittivity at 593K and dispersive permittivity at high temperatures. The NBT-BBFO sample shows a relaxor ferroelectric behavior at different frequencies.

  9. Study of effect of sintering time on the 2223 phase growth Bi-Pb-Sr-Ca-Cu-O superconductor by Rietveld method

    International Nuclear Information System (INIS)

    Parikin; Prasuad, W; Gunawan

    1996-01-01

    It has been reported that the sintering time is as important for the preparation of superconductor as the sintering temperature and method. This paper reports on the finding of the optimum sintering time in the preparation of the 2223 phase bismuth (Bi) superconductor. The samples were synthesized with nominal composition 1.84 : 0.34 : 1.91 : 2.03 : 3.06 from raw materials by solid state reaction and sintered at 860 o C for five days. The resintering were done three times, i.e. 24, 48 and 96 hours. The Rietveld analysis shows that the 2223 phase grows continuously as a function of the sintering time. The highest percentage of the 2223 phase (80.64%) were obtained at 96 hours sintering time. The result suggests that the 2223 phase can be obtained effectively by sintering with sufficiently long time

  10. Mineralogical analysis of clays in hardsetting soil horizons, by X-ray fluorescence and X-ray diffraction using Rietveld method

    International Nuclear Information System (INIS)

    Prandel, L.V.; Saab, S.C.; Brinatti, A.M.; Giarola, N.F.B.; Leite, W.C.; Cassaro, F.A.M.

    2014-01-01

    Diffraction and spectroscopic techniques have been shown to be suitable for obtaining physical and mineralogical properties in polycrystalline soil samples, and also in their precursor compounds. For instance, the X-ray fluorescence (XRF) spectroscopy allows obtaining the elemental composition of an investigated sample, while the X-ray diffraction (XRD) technique permits obtaining qualitative and quantitative composition of the soil minerals through the Rietveld method (RM). In this study Yellow Latosol (Oxisol), Yellow Argisol (Ultisol) and Gray Argisol (Ultisol) soil samples, classified as “hardsetting soils”, extracted from areas located at Northeast and Southeast of Brazilian coast were investigated. The soils and their fractions were analyzed in an EDX-700 and an XRD-6000 (Cu K α radiation). XRF results indicate high percentages of Si and Al, and small percentage of Fe and Ti in the investigated samples. The DRX data and RM indicate that there was a predominance of kaolinite and halloysite minerals (kaolin group minerals) in the clay fractions, which are presumably responsible for the formation of kaolinitic plasma in these soils. Also, the obtained results showed that the XRF, XRD techniques and RM were very helpful for investigating the mineralogical composition of a hardsetting soil. - Highlights: ► Elemental composition of soil samples through X-Ray fluorescence. ► Mineralogical quantification through X-ray diffraction and Rietveld method. ► Oxisol and Ultisol, Brazil ‘Barreiras’ formation. ► High amounts of Si and Al oxides and low amounts of Fe and Ti oxides. ► Predominance of kaolinite in the clay fraction

  11. Quantitative determination of phases in ZrO{sub 2} (MgO) (Y{sub 2}O{sub 3}) using the Rietveld method; Determinacao quantitativa de fases em ZrO{sub 2} - MgO - Y{sub 2}O{sub 3} utilizando o metodo de Rietveld

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Antonio Carlos de

    2007-07-01

    The key objective of this work is the crystallographic characterization of the zircon co-doped with Yttria and magnesium with the application of the Rietveld method for quantitative phase analysis of zircon polymorph (zircon monoclinic, tetragonal, and cubic). Samples of zircon polymorph were obtained from zircon doped with Yttria and magnesium at defined molar concentrations. The zircon polymorph stability during subeutetoid aging at 1350 deg C were investigated to determine ZrO{sub 2} - MgO - Y{sub 2}0{sub 3} phases degradation and to define the solid solutions stability environment. ZrO{sub 2} powders doped with 8 mol por cent of MgO and 1 mol por cent of Y{sub 2}O{sub 3}, and 9 mol por cent of MgO and 0 mol por cent of Y{sub 2}O{sub 3} have been prepared by chemical route using the co-precipitation method. These samples have been calcinate at 550 deg C, sintered at 1500 deg C and characterized by the Rietveld method using the X-ray diffraction data. The variation of the lattice parameter, changes in the phase composition and their microstructures are discussed. The application of the Rietveld method for quantitative phase analysis of zircon polymorph (zircon tetragonal and cubic) reveals no formation of tetragonal phase and indicating that the matrix is the cubic phase with low concentration of monoclinic phase.(author)

  12. The Rietveld method applied to the quantitative mineralogical analysis of some soil samples from Argentina Aplicación del método de Rietveld al análisis mineral��gico cuantitativo de algunas muestras de suelos de la Argentina

    Directory of Open Access Journals (Sweden)

    Stella M Zabala

    2007-07-01

    Full Text Available The mineralogical quantification of soils species is mainly obtained by analysis of X-ray diffraction (XRD patterns. The classic method, for these analyses, is limited to semi quantitative determinations due to the overlapping of different specie's peaks and processes of absorption of the constituents, the wide range of particle size distribution, etc. The use of the Rietveld method for XRD quantitative analysis, in mixtures of minerals, has allowed to improve the accuracy of the quantitative results and to extend it to complex systems, as soils, transforming it in a meaningful tool for soils investigation. In this work, quantitative results obtained by the application of classic and Rietveld methods, are compared in different soils samples from Argentina. A set of mixtures of minerals with similar composition to three studied samples, was also quantified by Rietveld method, with absolute error lower than 3%. Obtained results indicate that quantitative analysis by Rietveld method, can improve the results found by XRD classic method and may be used for the quantitative determination of soil minerals.La cuantificación mineralógica de componentes del suelo es obtenida principalmente por análisis de espectros de difracción de rayos X (DRX. El método clásico aplicado para dicho análisis está limitado a determinaciones semi-cuantitativas debido a la superposición de picos de las distintas especies y procesos de absorción de los constituyentes, el amplio rango de distribución de tamaño de partícula, etc. El uso del método de Rietveld para el análisis cuantitativo por DRX, en mezclas de minerales, ha permitido mejorar la exactitud de los resultados cuantitativos y extenderlo a sistemas complejos, como lo son los suelos, transformándose en una herramienta significativa para su investigación. En este trabajo se comparan los resultados cuantitativos obtenidos por la aplicación del método clásico y de Rietveld, a diferentes muestras de

  13. Method of optimization of the natural gas refining process

    Energy Technology Data Exchange (ETDEWEB)

    Sadykh-Zade, E.S.; Bagirov, A.A.; Mardakhayev, I.M.; Razamat, M.S.; Tagiyev, V.G.

    1980-01-01

    The SATUM (automatic control system of technical operations) system introduced at the Shatlyk field should assure good quality of gas refining. In order to optimize the natural gas refining processes and experimental-analytical method is used in compiling the mathematical descriptions. The program, compiled in Fortran language, in addition to parameters of optimal conditions gives information on the yield of concentrate and water, concentration and consumption of DEG, composition and characteristics of the gas and condensate. The algorithm for calculating optimum engineering conditions of gas refining is proposed to be used in ''advice'' mode, and also for monitoring progress of the gas refining process.

  14. Refinement of RAIM via Implementation of Implicit Euler Method

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yoonhee; Kim, Han-Chul [Korea Institute of Nuclear and Safety, Daejeon (Korea, Republic of)

    2016-10-15

    The first approach is a mechanistic approach which is used in LIRIC in which more than 200 reactions are modeled in detail. This approach enables to perform the detailed analysis. However, it requires huge computation burden. The other approach is a simplified model approach which is used in the IMOD, ASTEC/IODE, and etc. Recently, KINS has developed RAIM (Radio-Active Iodine chemistry Model) based on the simplified model approach. Since the numerical analysis module in RAIM is based on the explicit Euler method, there are major issues on the stability of the module. Therefore, implementation of a stable numerical method becomes essential. In this study, RAIM is refined via implementation of implicit Euler method in which the Newton method is used to find the solutions at each time step. The refined RAIM is tested by comparing to RAIM based on the explicit Euler method. In this paper, RAIM was refined by implementing the implicit Euler method. At each time step of the method in the refined RAIM, the reaction kinetics equations are solved by the Newton method in which elements of the Jacobian matrix are expressed analytically. With the results of OECD-BIP P10T2 test, the refined RAIM was compared to RAIM with the explicit Euler method. The refined RAIM shows better agreement with the experimental data than those from the explicit Euler method. For the rapid change of pH during the experiment, the refined RAIM gives more realistic changes in the concentrations of chemical species than those from the explicit Euler method. In addition, in terms of computing time, the refined RAIM shows comparable computing time to that with explicit Euler method. These comparisons are attributed to ⁓10 times larger time step size used in the implicit Euler method, even though computation burden at each time step in the refined RAIM is much higher than that of the explicit Euler method. Compared to the experimental data, the refined RAIM still shows discrepancy, which are attributed

  15. Refinement of RAIM via Implementation of Implicit Euler Method

    International Nuclear Information System (INIS)

    Lee, Yoonhee; Kim, Han-Chul

    2016-01-01

    The first approach is a mechanistic approach which is used in LIRIC in which more than 200 reactions are modeled in detail. This approach enables to perform the detailed analysis. However, it requires huge computation burden. The other approach is a simplified model approach which is used in the IMOD, ASTEC/IODE, and etc. Recently, KINS has developed RAIM (Radio-Active Iodine chemistry Model) based on the simplified model approach. Since the numerical analysis module in RAIM is based on the explicit Euler method, there are major issues on the stability of the module. Therefore, implementation of a stable numerical method becomes essential. In this study, RAIM is refined via implementation of implicit Euler method in which the Newton method is used to find the solutions at each time step. The refined RAIM is tested by comparing to RAIM based on the explicit Euler method. In this paper, RAIM was refined by implementing the implicit Euler method. At each time step of the method in the refined RAIM, the reaction kinetics equations are solved by the Newton method in which elements of the Jacobian matrix are expressed analytically. With the results of OECD-BIP P10T2 test, the refined RAIM was compared to RAIM with the explicit Euler method. The refined RAIM shows better agreement with the experimental data than those from the explicit Euler method. For the rapid change of pH during the experiment, the refined RAIM gives more realistic changes in the concentrations of chemical species than those from the explicit Euler method. In addition, in terms of computing time, the refined RAIM shows comparable computing time to that with explicit Euler method. These comparisons are attributed to ⁓10 times larger time step size used in the implicit Euler method, even though computation burden at each time step in the refined RAIM is much higher than that of the explicit Euler method. Compared to the experimental data, the refined RAIM still shows discrepancy, which are attributed

  16. Rietveld originals : Handle with care!

    NARCIS (Netherlands)

    Zijlstra, H.

    2009-01-01

    The work of architect Gerrit Th. Rietveld (1888 – 1964) is appreciated throughout the world. Many of the well-known buildings he designed have survived to the present. Some have been restored or refurbished, depending on the condition of the building, current needs of the building users, etc.

  17. Trajectory Optimization Based on Multi-Interval Mesh Refinement Method

    Directory of Open Access Journals (Sweden)

    Ningbo Li

    2017-01-01

    Full Text Available In order to improve the optimization accuracy and convergence rate for trajectory optimization of the air-to-air missile, a multi-interval mesh refinement Radau pseudospectral method was introduced. This method made the mesh endpoints converge to the practical nonsmooth points and decreased the overall collocation points to improve convergence rate and computational efficiency. The trajectory was divided into four phases according to the working time of engine and handover of midcourse and terminal guidance, and then the optimization model was built. The multi-interval mesh refinement Radau pseudospectral method with different collocation points in each mesh interval was used to solve the trajectory optimization model. Moreover, this method was compared with traditional h method. Simulation results show that this method can decrease the dimensionality of nonlinear programming (NLP problem and therefore improve the efficiency of pseudospectral methods for solving trajectory optimization problems.

  18. Iterative Refinement Methods for Time-Domain Equalizer Design

    Directory of Open Access Journals (Sweden)

    Evans Brian L

    2006-01-01

    Full Text Available Commonly used time domain equalizer (TEQ design methods have been recently unified as an optimization problem involving an objective function in the form of a Rayleigh quotient. The direct generalized eigenvalue solution relies on matrix decompositions. To reduce implementation complexity, we propose an iterative refinement approach in which the TEQ length starts at two taps and increases by one tap at each iteration. Each iteration involves matrix-vector multiplications and vector additions with matrices and two-element vectors. At each iteration, the optimization of the objective function either improves or the approach terminates. The iterative refinement approach provides a range of communication performance versus implementation complexity tradeoffs for any TEQ method that fits the Rayleigh quotient framework. We apply the proposed approach to three such TEQ design methods: maximum shortening signal-to-noise ratio, minimum intersymbol interference, and minimum delay spread.

  19. A method of refining aromatic hydrocarbons from coal chemical production

    Energy Technology Data Exchange (ETDEWEB)

    Zieborak, K.; Koprowski, A.; Ratajczak, W.

    1979-10-01

    A method is disclosed for refining aromatic hydrocarbons of coal chemical production by contact of liquid aromatic hydrocarbons and their mixtures with a strongly acid macroporous sulfocationite in the H-form at atmospheric pressure and high temperature. The method is distinguished in that the aromatic hydrocarbons and their mixtures, from which alkali compounds have already been removed, are supplied for refinement with the sulfocationite with simultaneous addition of olefin derivatives of aromatic hydrocarbons, followed by separation of pure hydrocarbons by rectification. Styrene or alpha-methylstyrene is used as the olefin derivatives of the aromatic hydrocarbons. The method is performed in several stages with addition of olefin derivatives of aromatic hydrocarbons at each stage.

  20. An efficient method for model refinement in diffuse optical tomography

    Science.gov (United States)

    Zirak, A. R.; Khademi, M.

    2007-11-01

    Diffuse optical tomography (DOT) is a non-linear, ill-posed, boundary value and optimization problem which necessitates regularization. Also, Bayesian methods are suitable owing to measurements data are sparse and correlated. In such problems which are solved with iterative methods, for stabilization and better convergence, the solution space must be small. These constraints subject to extensive and overdetermined system of equations which model retrieving criteria specially total least squares (TLS) must to refine model error. Using TLS is limited to linear systems which is not achievable when applying traditional Bayesian methods. This paper presents an efficient method for model refinement using regularized total least squares (RTLS) for treating on linearized DOT problem, having maximum a posteriori (MAP) estimator and Tikhonov regulator. This is done with combination Bayesian and regularization tools as preconditioner matrices, applying them to equations and then using RTLS to the resulting linear equations. The preconditioning matrixes are guided by patient specific information as well as a priori knowledge gained from the training set. Simulation results illustrate that proposed method improves the image reconstruction performance and localize the abnormally well.

  1. Rietveld analysis and electronic bands structure on Tc superconductors systems

    International Nuclear Information System (INIS)

    Aldea, N.; Tiusan, C. V.; Sandu, V.

    1999-01-01

    A procedure for simultaneous refinement of structural and micro-structural disorder parameters for polycrystalline YBa 2 Cu 3 O 7-x system is proposed. It is based on Rietveld method combined with Fourier analysis for broadened peaks Another purpose of this paper consists in electronic structure determination studied by using the self-consistent Tight Binding Linear Muffin-Tin Orbital Atomic Spheres Approximation TB-LMTO-ASA methods. The Rietveld method uses an analytical function that describes the profiles, usually pseudo-Voigt (pV) or Pearson VII (PVII). The parameters of the analytical profiles describe its amplitude, position and peak shape. The full width at half maximum (FWHM) is supposed to vary with the diffraction angle in agreement with the Caglioti, Paoletti and Ricci's relationship. The best structural parameters are determined in the least squares sense by the minimisation a classical residual using the Marquardt method. In this case, the peak profiles were modelled by the pseudo-Voigt function corrected by the instrumental asymmetry. The physical information obtained are: scale factor, lattice parameters, atomic position and displacements, atomic occupation numbers, temperature factor (isotropy or anisotropy), preferred orientation parameter, crystalline size and micro-strain along different crystallographic directions, distributions of crystallite size and micro-strain functions. This procedure was implemented on computer code and it has a friendly graphical interface based on pull down menus technique. From the experimental point of view the X-ray diffraction data were collected using a horizontal powder diffractometer in the Bragg-Brentano (BB) geometry with a Ni filtered CuKα, λ = 1.54178 A, at room temperature using a DRON 2 set-up. The diffraction profiles were measured with a proportional gas detector, a single channel pulse-height discrimination and a standard associated counting circuit. The electronic band calculations are based on the TB

  2. Method of refining mineral and shale oils, etc

    Energy Technology Data Exchange (ETDEWEB)

    1950-12-06

    A method is described for refining mineral oils, shale oils, tar oil. The oil is preferably treated with concentrated sulphuric acid, of not less than 90% by weight concentration or with chloro-sulphonic acid in order to extract the more reactive components of the oil. The solution (extract phase) is separated from the treated oil (raffinate phase) by centrifuging, characterised by centrifugally separating the extract phase from the raffinate phase before any noticeable chemical reaction with subsequent solution of acid reaction products in the raffinate phase has taken place. The acid remaining in the raffinate phase is allowed to react chemically with the more reactive constituents. The sludge formed is removed from the raffinate phase by centrifuging.

  3. Refining waste hardmetals into tungsten oxide nanosheets via facile method

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhifei; Zheng, Guangwei; Wang, Jinshu, E-mail: wangjsh@bjut.edu.cn; Li, Hongyi, E-mail: lhy06@bjut.edu.cn; Wu, Junshu; Du, Yucheng [Beijing University of Technology, Key Laboratory of Advanced Functional Materials, School of Materials Science and Engineering (China)

    2016-04-15

    A new hydrothermal system has been designed to recycle waste WC–Co hardmetal with low cobalt (Co) content (3 %). In the solution system, nitric acid was designed to dissolve Co, H{sub 2}O{sub 2} served as oxidant to accelerate the oxidation of the WC–Co hardmetals, and fluorine (F{sup −}) was designed to dissolve and recrystallize generated tungsten oxides, which were found to possess a layered structure using scanning electron microscopy and transmission electron microscopy. The obtained tungsten oxides were identified as WO{sub 3}·0.33H{sub 2}O by X-ray diffraction and their specific surface area was measured as 89.2 m{sup 2} g{sup −1} via N{sub 2} adsorption–desorption techniques. The present layered structure tungsten oxides exhibited a promising capability for removing lead ion (Pb{sup 2+}) and organic species, such as methyl blue. The adsorption model was found to be in agreement with Langmuir isotherm model. Given the facile synthesis procedure and promising properties of final products, this new approach should have great potential for refining some other waste hardmetals or tungsten products.Graphical AbstractA new hydrothermal system was designed to recycle waste hardmetal with low cobalt content. Through this method, waste hardmetal was refined into WO{sub 3}·0.33H{sub 2}O nanosheets which shows excellent adsorption capacities toward methylene blue and lead ion (Pb{sup 2+}).

  4. A refined method for creating saccular aneurysms in the rabbit

    Energy Technology Data Exchange (ETDEWEB)

    Krings, Timo [Department of Neuroradiology, University Hospital of the University of Technology Aachen, Pauwelsstrase 30, 52057, Aachen (Germany); Department of Neurosurgery, University Hospital of the University of Technology Aachen, Pauwelsstrase 30, 52057, Aachen (Germany); Moeller-Hartmann, Walter; Meetz, Alexander; Dreeskamp, Heiko; Stein, Klaus-Peter; Thron, Armin [Department of Neuroradiology, University Hospital of the University of Technology Aachen, Pauwelsstrase 30, 52057, Aachen (Germany); Hans, Franz-Josef; Thiex, Ruth; Gilsbach, Joachim M. [Department of Neurosurgery, University Hospital of the University of Technology Aachen, Pauwelsstrase 30, 52057, Aachen (Germany); Brunn, Anna [Department of Neuropathology, University Hospital of the University of Technology Aachen, Pauwelsstrase 30, 52057, Aachen (Germany); Scherer, Kira [Department of Laboratory Animal Science, University Hospital of the University of Technology Aachen, Pauwelsstrase 30, 52057, Aachen (Germany)

    2003-07-01

    We describe a refined animal model of human intracerebral aneurysms for testing endovascular devices for interventional neuroradiological procedures. Saccular aneurysms resulting from a stump of the right common carotid artery (CCA) were created in 15 New Zealand White rabbits by intraluminal incubation of elastase that was applied to the CCA after distal ligation of the CCA and proximal occlusion of the vessel using a pliable balloon. Subsequently a microcatheter was advanced to a position cranial to the balloon and the elastase was infused under fluoroscopic guidance to avoid retrograde flow to the trachea via aberrant vessels. Contrast-enhanced (CE) MRA at 1.5 T and conventional digital subtraction angiography was performed to test for aneurysm size, morphology and neck anatomy. In all 15 animals aneurysms resulted from the stump of the right CCA, ranging in size from 2.0 to 9.9 mm (mean 6.3 mm) in craniocaudal direction, 1.0 to 5.5 mm (mean 3.8 mm) in mediolateral direction and 1.0 to 3.8 mm (mean 2.4 mm) in neck diameter. Aneurysm morphology could be adequately demonstrated using CE MRA. On histological evaluation a loss of the internal elastic lamina was noted. The described method represents an easy, reliable, and reproducible method of aneurysm creation in the rabbit in an area of high shear stress. These aneurysms can be used for testing new endovascular devices for embolization of intracranial aneurysms. (orig.)

  5. A refined method for creating saccular aneurysms in the rabbit

    International Nuclear Information System (INIS)

    Krings, Timo; Moeller-Hartmann, Walter; Meetz, Alexander; Dreeskamp, Heiko; Stein, Klaus-Peter; Thron, Armin; Hans, Franz-Josef; Thiex, Ruth; Gilsbach, Joachim M.; Brunn, Anna; Scherer, Kira

    2003-01-01

    We describe a refined animal model of human intracerebral aneurysms for testing endovascular devices for interventional neuroradiological procedures. Saccular aneurysms resulting from a stump of the right common carotid artery (CCA) were created in 15 New Zealand White rabbits by intraluminal incubation of elastase that was applied to the CCA after distal ligation of the CCA and proximal occlusion of the vessel using a pliable balloon. Subsequently a microcatheter was advanced to a position cranial to the balloon and the elastase was infused under fluoroscopic guidance to avoid retrograde flow to the trachea via aberrant vessels. Contrast-enhanced (CE) MRA at 1.5 T and conventional digital subtraction angiography was performed to test for aneurysm size, morphology and neck anatomy. In all 15 animals aneurysms resulted from the stump of the right CCA, ranging in size from 2.0 to 9.9 mm (mean 6.3 mm) in craniocaudal direction, 1.0 to 5.5 mm (mean 3.8 mm) in mediolateral direction and 1.0 to 3.8 mm (mean 2.4 mm) in neck diameter. Aneurysm morphology could be adequately demonstrated using CE MRA. On histological evaluation a loss of the internal elastic lamina was noted. The described method represents an easy, reliable, and reproducible method of aneurysm creation in the rabbit in an area of high shear stress. These aneurysms can be used for testing new endovascular devices for embolization of intracranial aneurysms. (orig.)

  6. A refined method for calculating equivalent effective stratospheric chlorine

    Science.gov (United States)

    Engel, Andreas; Bönisch, Harald; Ostermöller, Jennifer; Chipperfield, Martyn P.; Dhomse, Sandip; Jöckel, Patrick

    2018-01-01

    Chlorine and bromine atoms lead to catalytic depletion of ozone in the stratosphere. Therefore the use and production of ozone-depleting substances (ODSs) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent effective stratospheric chlorine (EESC) has been adopted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a refined formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. We show that a much better agreement with inorganic halogen loading from the chemistry transport model TOMCAT is achieved compared with using the current formulation. The refined formulation shows EESC levels in the year 1980 for the mid-latitude lower stratosphere, which are significantly lower than previously calculated. The year 1980 is commonly used as a benchmark to which EESC must return in order to reach significant progress towards halogen and ozone recovery. Assuming that - under otherwise unchanged conditions - the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than estimated in this region of the stratosphere with the current method for calculation of EESC. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We further discuss the value of EESC as a proxy for future evolution of inorganic halogen loading under changing atmospheric dynamics using simulations from

  7. Combined PDF and Rietveld studies of ADORable zeolites and the disordered intermediate IPC-1P

    Czech Academy of Sciences Publication Activity Database

    Morris, S. A.; Wheatley, P. S.; Položij, M.; Nachtigall, P.; Eliášová, Pavla; Čejka, Jiří; Lucas, T. C.; Hriljac, J. A.; Pinar, A. B.; Morris, R. E.

    2016-01-01

    Roč. 45, č. 36 (2016), s. 14124-14130 ISSN 1477-9226 R&D Projects: GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : Distribution functions * Rietveld refinement * Zeolites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.029, year: 2016

  8. Refining developmental coordination disorder subtyping with multivariate statistical methods

    Directory of Open Access Journals (Sweden)

    Lalanne Christophe

    2012-07-01

    Full Text Available Abstract Background With a large number of potentially relevant clinical indicators penalization and ensemble learning methods are thought to provide better predictive performance than usual linear predictors. However, little is known about how they perform in clinical studies where few cases are available. We used Random Forests and Partial Least Squares Discriminant Analysis to select the most salient impairments in Developmental Coordination Disorder (DCD and assess patients similarity. Methods We considered a wide-range testing battery for various neuropsychological and visuo-motor impairments which aimed at characterizing subtypes of DCD in a sample of 63 children. Classifiers were optimized on a training sample, and they were used subsequently to rank the 49 items according to a permuted measure of variable importance. In addition, subtyping consistency was assessed with cluster analysis on the training sample. Clustering fitness and predictive accuracy were evaluated on the validation sample. Results Both classifiers yielded a relevant subset of items impairments that altogether accounted for a sharp discrimination between three DCD subtypes: ideomotor, visual-spatial and constructional, and mixt dyspraxia. The main impairments that were found to characterize the three subtypes were: digital perception, imitations of gestures, digital praxia, lego blocks, visual spatial structuration, visual motor integration, coordination between upper and lower limbs. Classification accuracy was above 90% for all classifiers, and clustering fitness was found to be satisfactory. Conclusions Random Forests and Partial Least Squares Discriminant Analysis are useful tools to extract salient features from a large pool of correlated binary predictors, but also provide a way to assess individuals proximities in a reduced factor space. Less than 15 neuro-visual, neuro-psychomotor and neuro-psychological tests might be required to provide a sensitive and

  9. Multilevel local refinement and multigrid methods for 3-D turbulent flow

    Energy Technology Data Exchange (ETDEWEB)

    Liao, C.; Liu, C. [UCD, Denver, CO (United States); Sung, C.H.; Huang, T.T. [David Taylor Model Basin, Bethesda, MD (United States)

    1996-12-31

    A numerical approach based on multigrid, multilevel local refinement, and preconditioning methods for solving incompressible Reynolds-averaged Navier-Stokes equations is presented. 3-D turbulent flow around an underwater vehicle is computed. 3 multigrid levels and 2 local refinement grid levels are used. The global grid is 24 x 8 x 12. The first patch is 40 x 16 x 20 and the second patch is 72 x 32 x 36. 4th order artificial dissipation are used for numerical stability. The conservative artificial compressibility method are used for further improvement of convergence. To improve the accuracy of coarse/fine grid interface of local refinement, flux interpolation method for refined grid boundary is used. The numerical results are in good agreement with experimental data. The local refinement can improve the prediction accuracy significantly. The flux interpolation method for local refinement can keep conservation for a composite grid, therefore further modify the prediction accuracy.

  10. Adaptive mesh refinement and adjoint methods in geophysics simulations

    Science.gov (United States)

    Burstedde, Carsten

    2013-04-01

    It is an ongoing challenge to increase the resolution that can be achieved by numerical geophysics simulations. This applies to considering sub-kilometer mesh spacings in global-scale mantle convection simulations as well as to using frequencies up to 1 Hz in seismic wave propagation simulations. One central issue is the numerical cost, since for three-dimensional space discretizations, possibly combined with time stepping schemes, a doubling of resolution can lead to an increase in storage requirements and run time by factors between 8 and 16. A related challenge lies in the fact that an increase in resolution also increases the dimensionality of the model space that is needed to fully parametrize the physical properties of the simulated object (a.k.a. earth). Systems that exhibit a multiscale structure in space are candidates for employing adaptive mesh refinement, which varies the resolution locally. An example that we found well suited is the mantle, where plate boundaries and fault zones require a resolution on the km scale, while deeper area can be treated with 50 or 100 km mesh spacings. This approach effectively reduces the number of computational variables by several orders of magnitude. While in this case it is possible to derive the local adaptation pattern from known physical parameters, it is often unclear what are the most suitable criteria for adaptation. We will present the goal-oriented error estimation procedure, where such criteria are derived from an objective functional that represents the observables to be computed most accurately. Even though this approach is well studied, it is rarely used in the geophysics community. A related strategy to make finer resolution manageable is to design methods that automate the inference of model parameters. Tweaking more than a handful of numbers and judging the quality of the simulation by adhoc comparisons to known facts and observations is a tedious task and fundamentally limited by the turnaround times

  11. A melt refining method for uranium-contaminated aluminum

    International Nuclear Information System (INIS)

    Uda, T.; Iba, H.; Hanawa, K.

    1986-01-01

    Melt refining of uranium-contaminated aluminum which has been difficult to decontaminate because of the high reactivity of aluminum, was experimentally studied. Samples of contaminated aluminum and its alloys were melted after adding various halide fluxes at various melting temperatures and various melting times. Uranium concentration in the resulting ingots was determined. Effective flux compositions were mixtures of chlorides and fluorides, such as LiF, KCl, and BaCl 2 , at a fluoride/chloride mole ratio of 1 to 1.5. The removal of uranium from aluminum (the ''decontamination effect'') increased with decreasing melting temperature, but the time allowed for reaction had little influence. Pure aluminum was difficult to decontaminate from uranium; however, uranium could be removed from alloys containing magnesium. This was because the activity of the aluminum was decreased by formation of the intermetallic compound Al-Mg. With a flux of LiF-KCl-BaCl 2 and a temperature of 800 0 C, uranium added to give an initial concentration of 500 ppm was removed from a commercial alloy of aluminum, A5056, which contains 5% magnesium, to a final concentration of 0.6 ppm, which is near that in the initial aluminum alloy

  12. Rietveld refinement, impedance spectroscopy and magnetic properties of Bi{sub 0.8}Sr{sub 0.2}FeO{sub 3} substituted Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Rekha [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Ahlawat, Neetu, E-mail: neetugju@yahoo.co.in [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Agarwal, Ashish; Sanghi, Sujata [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Sindhu, Monica [Department of Physics, MKJK College, Rohtak 124001, Haryana (India); Ahlawat, Navneet [Matu Ram Institute of Engineering and Management, Rohtak 124001, Haryana (India)

    2016-09-15

    We herein presented the investigation on the structural, electrical and magnetic properties of (1−x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})–x(Bi{sub 0.8}Sr{sub 0.2}FeO{sub 3}) polycrystalline ceramic samples, with x=0.1, 0.3, 0.5 and 0.7. These samples were prepared by conventional solid state reaction method and the crystalline phase of prepared ceramics was identified with the help of X-ray diffraction pattern. Rietveld analysis of the obtained XRD data confirmed that all the synthesized samples adopt the rhombohedral crystal structure with R3c space group. Impedance spectroscopic measurements were performed on all the compositions in the frequency range 10 Hz–5 MHz to probe the electrical microstructure of polycrystalline (1−x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})–x(Bi{sub 0.8}Sr{sub 0.2}FeO{sub 3}) ceramics, which changes significantly as a function of x (content of BSFO). A significant increase in dielectric constant has been observed with increase in BSFO concentration, which was attributed to enhancement of oxygen vacancies. Detailed study of impedance complex plane plots revealed the presence of non-Debye type relaxation for all the prepared systems and enabled us to separate the contribution from grains and grain boundaries. Equivalent circuit model (R{sub g}CPE{sub g})(R{sub gb}CPE{sub gb})(R{sub e}CPE{sub e}) was employed to explain the impedance data for all the prepared samples. The activation energies obtained from electric modulus as well as dc conductivity increase with increase in BSFO content, which approaches the value 1 eV and indicates an Arrehenius type thermally activated process. Remnant magnetization (M{sub r}) and coercive field (H{sub c}) are found to be increase with BSFO concentration. - Highlights: • (1−x)NBT–xBSFO (x=0.1, 0.3, 0.5, 0.7) ceramics were prepared. • There is no change in crystal structure. • These can be used as data storage materials.

  13. Spatially adaptive hp refinement approach for PN neutron transport equation using spectral element method

    International Nuclear Information System (INIS)

    Nahavandi, N.; Minuchehr, A.; Zolfaghari, A.; Abbasi, M.

    2015-01-01

    Highlights: • Powerful hp-SEM refinement approach for P N neutron transport equation has been presented. • The method provides great geometrical flexibility and lower computational cost. • There is a capability of using arbitrary high order and non uniform meshes. • Both posteriori and priori local error estimation approaches have been employed. • High accurate results are compared against other common adaptive and uniform grids. - Abstract: In this work we presented the adaptive hp-SEM approach which is obtained from the incorporation of Spectral Element Method (SEM) and adaptive hp refinement. The SEM nodal discretization and hp adaptive grid-refinement for even-parity Boltzmann neutron transport equation creates powerful grid refinement approach with high accuracy solutions. In this regard a computer code has been developed to solve multi-group neutron transport equation in one-dimensional geometry using even-parity transport theory. The spatial dependence of flux has been developed via SEM method with Lobatto orthogonal polynomial. Two commonly error estimation approaches, the posteriori and the priori has been implemented. The incorporation of SEM nodal discretization method and adaptive hp grid refinement leads to high accurate solutions. Coarser meshes efficiency and significant reduction of computer program runtime in comparison with other common refining methods and uniform meshing approaches is tested along several well-known transport benchmarks

  14. “Best fit” framework synthesis: refining the method

    Science.gov (United States)

    2013-01-01

    Background Following publication of the first worked example of the “best fit” method of evidence synthesis for the systematic review of qualitative evidence in this journal, the originators of the method identified a need to specify more fully some aspects of this particular derivative of framework synthesis. Methods and Results We therefore present a second such worked example in which all techniques are defined and explained, and their appropriateness is assessed. Specified features of the method include the development of new techniques to identify theories in a systematic manner; the creation of an a priori framework for the synthesis; and the “testing” of the synthesis. An innovative combination of existing methods of quality assessment, analysis and synthesis is used to complete the process. This second worked example was a qualitative evidence synthesis of employees’ views of workplace smoking cessation interventions, in which the “best fit” method was found to be practical and fit for purpose. Conclusions The method is suited to producing context-specific conceptual models for describing or explaining the decision-making and health behaviours of patients and other groups. It offers a pragmatic means of conducting rapid qualitative evidence synthesis and generating programme theories relating to intervention effectiveness, which might be of relevance both to researchers and policy-makers. PMID:23497061

  15. Synthesis of Al-5Ti-1B Refiner by Melt Reaction Method

    OpenAIRE

    LI He; CHAI Li-hua; MA Teng-fei; CHEN Zi-yong

    2017-01-01

    Al-5Ti-1B refiner was successfully prepared by melt reaction method. Through the thermodynamics calculation, the initial reaction temperature was determined. The influence of reaction temperature on microstructure and absorption rate of the alloy was investigated. The phase and microstructure of the alloy were observed by X-ray diffraction, scanning electron microscope and energy dispersive spectrometer. The Al-5Ti-1B refiner was extruded at high temperature to wire with the diameter of 9.5mm...

  16. Methods of refining natural oils, and methods of producing fuel compositions

    Science.gov (United States)

    Firth, Bruce E.; Kirk, Sharon E.

    2015-10-27

    A method of refining a natural oil includes: (a) providing a feedstock that includes a natural oil; (b) reacting the feedstock in the presence of a metathesis catalyst to form a metathesized product that includes olefins and esters; (c) passivating residual metathesis catalyst with an agent that comprises nitric acid; (d) separating the olefins in the metathesized product from the esters in the metathesized product; and (e) transesterifying the esters in the presence of an alcohol to form a transesterified product and/or hydrogenating the olefins to form a fully or partially saturated hydrogenated product. Methods for suppressing isomerization of olefin metathesis products produced in a metathesis reaction, and methods of producing fuel compositions are described.

  17. Usability Testing as a Method to Refine a Health Sciences Library Website.

    Science.gov (United States)

    Denton, Andrea H; Moody, David A; Bennett, Jason C

    2016-01-01

    User testing, a method of assessing website usability, can be a cost-effective and easily administered process to collect information about a website's effectiveness. A user experience (UX) team at an academic health sciences library has employed user testing for over three years to help refine the library's home page. Test methodology used in-person testers using the "think aloud" method to complete tasks on the home page. Review of test results revealed problem areas of the design and redesign; further testing was effective in refining the page. User testing has proved to be a valuable method to engage users and provide feedback to continually improve the library's home page.

  18. A simple nodal force distribution method in refined finite element meshes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jai Hak [Chungbuk National University, Chungju (Korea, Republic of); Shin, Kyu In [Gentec Co., Daejeon (Korea, Republic of); Lee, Dong Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cho, Seungyon [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2017-05-15

    In finite element analyses, mesh refinement is frequently performed to obtain accurate stress or strain values or to accurately define the geometry. After mesh refinement, equivalent nodal forces should be calculated at the nodes in the refined mesh. If field variables and material properties are available at the integration points in each element, then the accurate equivalent nodal forces can be calculated using an adequate numerical integration. However, in certain circumstances, equivalent nodal forces cannot be calculated because field variable data are not available. In this study, a very simple nodal force distribution method was proposed. Nodal forces of the original finite element mesh are distributed to the nodes of refined meshes to satisfy the equilibrium conditions. The effect of element size should also be considered in determining the magnitude of the distributing nodal forces. A program was developed based on the proposed method, and several example problems were solved to verify the accuracy and effectiveness of the proposed method. From the results, accurate stress field can be recognized to be obtained from refined meshes using the proposed nodal force distribution method. In example problems, the difference between the obtained maximum stress and target stress value was less than 6 % in models with 8-node hexahedral elements and less than 1 % in models with 20-node hexahedral elements or 10-node tetrahedral elements.

  19. A summary of available Rietveld and related software resources

    International Nuclear Information System (INIS)

    Cranswick, L.M.D

    1999-01-01

    Full text: There is a wide variety of Rietveld software available from both commercial and academic institutions. These resources will be reviewed along with the importance of validating Rietveld quantitative analysis results and gaining skills in complementary areas. This part of the workshop will mention a number of relevant programs and their main functionality: Rietveld software, Rietveld utilities, Rietveld friendly software and other powder diffraction utilities. Some of the main benefits of appreciating the availability of a wide range of software include: cross validation of results, data quality and diffractometer alignment, exploring new areas of research and analysis, solving new problems, nuances that occur as part of Rietveld analysis. Copyright (1999) Australian X-ray Analytical Association Inc

  20. Grid refinement model in lattice Boltzmann method for stream function-vorticity formulations

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Myung Seob [Dept. of Mechanical Engineering, Dongyang Mirae University, Seoul (Korea, Republic of)

    2015-03-15

    In this study, we present a grid refinement model in the lattice Boltzmann method (LBM) for two-dimensional incompressible fluid flow. That is, the model combines the desirable features of the lattice Boltzmann method and stream function-vorticity formulations. In order to obtain an accurate result, very fine grid (or lattice) is required near the solid boundary. Therefore, the grid refinement model is used in the lattice Boltzmann method for stream function-vorticity formulation. This approach is more efficient in that it can obtain the same accurate solution as that in single-block approach even if few lattices are used for computation. In order to validate the grid refinement approach for the stream function-vorticity formulation, the numerical simulations of lid-driven cavity flows were performed and good results were obtained.

  1. Analysis and development of spatial hp-refinement methods for solving the neutron transport equation

    International Nuclear Information System (INIS)

    Fournier, D.

    2011-01-01

    The different neutronic parameters have to be calculated with a higher accuracy in order to design the 4. generation reactor cores. As memory storage and computation time are limited, adaptive methods are a solution to solve the neutron transport equation. The neutronic flux, solution of this equation, depends on the energy, angle and space. The different variables are successively discretized. The energy with a multigroup approach, considering the different quantities to be constant on each group, the angle by a collocation method called SN approximation. Once the energy and angle variable are discretized, a system of spatially-dependent hyperbolic equations has to be solved. Discontinuous finite elements are used to make possible the development of hp-refinement methods. Thus, the accuracy of the solution can be improved by spatial refinement (h-refinement), consisting into subdividing a cell into sub-cells, or by order refinement (p-refinement), by increasing the order of the polynomial basis. In this thesis, the properties of this methods are analyzed showing the importance of the regularity of the solution to choose the type of refinement. Thus, two error estimators are used to lead the refinement process. Whereas the first one requires high regularity hypothesis (analytical solution), the second one supposes only the minimal hypothesis required for the solution to exist. The comparison of both estimators is done on benchmarks where the analytic solution is known by the method of manufactured solutions. Thus, the behaviour of the solution as a regard of the regularity can be studied. It leads to a hp-refinement method using the two estimators. Then, a comparison is done with other existing methods on simplified but also realistic benchmarks coming from nuclear cores. These adaptive methods considerably reduces the computational cost and memory footprint. To further improve these two points, an approach with energy-dependent meshes is proposed. Actually, as the

  2. Synthesis of Al-5Ti-1B Refiner by Melt Reaction Method

    Directory of Open Access Journals (Sweden)

    LI He

    2017-02-01

    Full Text Available Al-5Ti-1B refiner was successfully prepared by melt reaction method. Through the thermodynamics calculation, the initial reaction temperature was determined. The influence of reaction temperature on microstructure and absorption rate of the alloy was investigated. The phase and microstructure of the alloy were observed by X-ray diffraction, scanning electron microscope and energy dispersive spectrometer. The Al-5Ti-1B refiner was extruded at high temperature to wire with the diameter of 9.5mm, and then the refinement experiment was carried out on pure aluminium. The results indicate that the refiner consists of TiB2, TiAl3 and α-Al, and the microstructure prepared at 850℃ is the optimum and the absorption rate of Ti and B matches the best. The TiAl3 and TiB2 phases distribute homogeneously in the matrix after extrusion. When adding 0.2%(mass fraction of Al-5Ti-1B refiner, the grain size of pure aluminium reduces from 3.99mm to 0.45mm.

  3. Dense and refined microstructure 3D measurement method based on an optical microscope and varying illuminations

    International Nuclear Information System (INIS)

    Li, Zhongwei; Li, Y F

    2011-01-01

    We propose a novel microscopic photometric stereo (MPS) method based on a conventional optical microscope and varying illuminations for dense and refined microstructure 3D measurement. To guarantee the flexibility of the MPS, an uncalibrated photometric stereo (UPS) method, which does not require a priori knowledge of the light-source direction or the light-source intensity, is employed to recover surface normals and albedos from the captured multiple micro-images. Although the UPS has been studied before, there are some particular issues to be addressed to make it suitable for microscopic cases. For resolving the inherent generalized bas-relief (GBR) ambiguity of the UPS, we present a GBR disambiguation method based on a framework of entropy minimization, and extend it using a graph-cut energy minimization to decrease the influence of noise and further refine the recovered surface normal. The proposed MPS method has been tested on synthetic as well as real images and very encouraging results have been obtained. The experimental results show that this novel method can reconstruct dense and refined 3D points for the microstructure. It is an easy-to-implement yet effective alternative method for microstructure 3D measurement and can be applied to many potential fields

  4. An assessment of dietary exposure to glyphosate using refined deterministic and probabilistic methods.

    Science.gov (United States)

    Stephenson, C L; Harris, C A

    2016-09-01

    Glyphosate is a herbicide used to control broad-leaved weeds. Some uses of glyphosate in crop production can lead to residues of the active substance and related metabolites in food. This paper uses data on residue levels, processing information and consumption patterns, to assess theoretical lifetime dietary exposure to glyphosate. Initial estimates were made assuming exposure to the highest permitted residue levels in foods. These intakes were then refined using median residue levels from trials, processing information, and monitoring data to achieve a more realistic estimate of exposure. Estimates were made using deterministic and probabilistic methods. Exposures were compared to the acceptable daily intake (ADI)-the amount of a substance that can be consumed daily without an appreciable health risk. Refined deterministic intakes for all consumers were at or below 2.1% of the ADI. Variations were due to cultural differences in consumption patterns and the level of aggregation of the dietary information in calculation models, which allows refinements for processing. Probabilistic exposure estimates ranged from 0.03% to 0.90% of the ADI, depending on whether optimistic or pessimistic assumptions were made in the calculations. Additional refinements would be possible if further data on processing and from residues monitoring programmes were available. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  5. Unstructured Cartesian refinement with sharp interface immersed boundary method for 3D unsteady incompressible flows

    Science.gov (United States)

    Angelidis, Dionysios; Chawdhary, Saurabh; Sotiropoulos, Fotis

    2016-11-01

    A novel numerical method is developed for solving the 3D, unsteady, incompressible Navier-Stokes equations on locally refined fully unstructured Cartesian grids in domains with arbitrarily complex immersed boundaries. Owing to the utilization of the fractional step method on an unstructured Cartesian hybrid staggered/non-staggered grid layout, flux mismatch and pressure discontinuity issues are avoided and the divergence free constraint is inherently satisfied to machine zero. Auxiliary/hanging nodes are used to facilitate the discretization of the governing equations. The second-order accuracy of the solver is ensured by using multi-dimension Lagrange interpolation operators and appropriate differencing schemes at the interface of regions with different levels of refinement. The sharp interface immersed boundary method is augmented with local near-boundary refinement to handle arbitrarily complex boundaries. The discrete momentum equation is solved with the matrix free Newton-Krylov method and the Krylov-subspace method is employed to solve the Poisson equation. The second-order accuracy of the proposed method on unstructured Cartesian grids is demonstrated by solving the Poisson equation with a known analytical solution. A number of three-dimensional laminar flow simulations of increasing complexity illustrate the ability of the method to handle flows across a range of Reynolds numbers and flow regimes. Laminar steady and unsteady flows past a sphere and the oblique vortex shedding from a circular cylinder mounted between two end walls demonstrate the accuracy, the efficiency and the smooth transition of scales and coherent structures across refinement levels. Large-eddy simulation (LES) past a miniature wind turbine rotor, parameterized using the actuator line approach, indicates the ability of the fully unstructured solver to simulate complex turbulent flows. Finally, a geometry resolving LES of turbulent flow past a complete hydrokinetic turbine illustrates

  6. An adaptive mesh refinement approach for average current nodal expansion method in 2-D rectangular geometry

    International Nuclear Information System (INIS)

    Poursalehi, N.; Zolfaghari, A.; Minuchehr, A.

    2013-01-01

    Highlights: ► A new adaptive h-refinement approach has been developed for a class of nodal method. ► The resulting system of nodal equations is more amenable to efficient numerical solution. ► The benefit of the approach is reducing computational efforts relative to the uniform fine mesh modeling. ► Spatially adaptive approach greatly enhances the accuracy of the solution. - Abstract: The aim of this work is to develop a spatially adaptive coarse mesh strategy that progressively refines the nodes in appropriate regions of domain to solve the neutron balance equation by zeroth order nodal expansion method. A flux gradient based a posteriori estimation scheme has been utilized for checking the approximate solutions for various nodes. The relative surface net leakage of nodes has been considered as an assessment criterion. In this approach, the core module is called in by adaptive mesh generator to determine gradients of node surfaces flux to explore the possibility of node refinements in appropriate regions and directions of the problem. The benefit of the approach is reducing computational efforts relative to the uniform fine mesh modeling. For this purpose, a computer program ANRNE-2D, Adaptive Node Refinement Nodal Expansion, has been developed to solve neutron diffusion equation using average current nodal expansion method for 2D rectangular geometries. Implementing the adaptive algorithm confirms its superiority in enhancing the accuracy of the solution without using fine nodes throughout the domain and increasing the number of unknown solution. Some well-known benchmarks have been investigated and improvements are reported

  7. Adaptive local refinement and multi-level methods for simulating multiphasic flows

    International Nuclear Information System (INIS)

    Minjeaud, Sebastian

    2010-01-01

    This thesis describes some numerical and mathematical aspects of incompressible multiphase flows simulations with a diffuse interface Cahn-Hilliard / Navier-Stokes model (interfaces have a small but a positive thickness). The space discretization is performed thanks to a Galerkin formulation and the finite elements method. The presence of different scales in the system (interfaces have a very small thickness compared to the characteristic lengths of the domain) suggests the use of a local adaptive refinement method. The algorithm that is introduced allows to implicitly handle the non-conformities of the generated meshes to produce conformal finite elements approximation spaces. It consists in refining basis functions instead of cells. The refinement of a basis function is made possible by the conceptual existence of a nested sequence of uniformly refined grids from which 'parent-child' relationships are deduced, linking the basis functions of two consecutive refinement levels. Moreover, it is shown how this method can be exploited to build multigrid pre-conditioners. From a composite finite elements approximation space, it is indeed possible to rebuild, by 'coarsening', a sequence of auxiliary nested spaces which allows to enter in the abstract multigrid framework. Concerning the time discretization, it begins with the study of the Cahn-Hilliard system. A semi-implicit scheme is proposed to remedy to convergence failures of the Newton method used to solve this (non linear) system. It guarantees the decrease of the discrete free energy ensuring the stability of the scheme. The existence and convergence of discrete solutions towards the weak solution of the system are shown. The study continues with providing an unconditionally stable time discretization of the complete Cahn-Hilliard / Navier-Stokes model. An important point is that this discretization does not strongly couple the Cahn-Hilliard and Navier-Stokes systems allowing to independently solve the two systems

  8. A compressed sensing based method with support refinement for impulse noise cancelation in DSL

    KAUST Repository

    Quadeer, Ahmed Abdul

    2013-06-01

    This paper presents a compressed sensing based method to suppress impulse noise in digital subscriber line (DSL). The proposed algorithm exploits the sparse nature of the impulse noise and utilizes the carriers, already available in all practical DSL systems, for its estimation and cancelation. Specifically, compressed sensing is used for a coarse estimate of the impulse position, an a priori information based maximum aposteriori probability (MAP) metric for its refinement, followed by least squares (LS) or minimum mean square error (MMSE) estimation for estimating the impulse amplitudes. Simulation results show that the proposed scheme achieves higher rate as compared to other known sparse estimation algorithms in literature. The paper also demonstrates the superior performance of the proposed scheme compared to the ITU-T G992.3 standard that utilizes RS-coding for impulse noise refinement in DSL signals. © 2013 IEEE.

  9. Grid refinement for aeroacoustics in the lattice Boltzmann method: A directional splitting approach

    Science.gov (United States)

    Gendre, Félix; Ricot, Denis; Fritz, Guillaume; Sagaut, Pierre

    2017-08-01

    This study focuses on grid refinement techniques for the direct simulation of aeroacoustics, when using weakly compressible lattice Boltzmann models, such as the D3Q19 athermal velocity set. When it comes to direct noise computation, very small errors on the density or pressure field may have great negative consequences. Even strong acoustic density fluctuations have indeed a clearly lower amplitude than the hydrodynamic ones. This work deals with such very weak spurious fluctuations that emerge when a vortical structure crosses a refinement interface, which may contaminate the resulting aeroacoustic field. We show through an extensive literature review that, within the framework described above, this issue has never been addressed before. To tackle this problem, we develop an alternative algorithm and compare its behavior to a classical one, which fits our in-house vertex-centered data structure. Our main idea relies on a directional splitting of the continuous discrete velocity Boltzmann equation, followed by an integration over specific characteristics. This method can be seen as a specific coupling between finite difference and lattice Boltzmann, locally on the interface between the two grids. The method is assessed considering two cases: an acoustic pulse and a convected vortex. We show how very small errors on the density field arise and propagate throughout the domain when a vortical flow crosses the refinement interface. We also show that an increased free stream Mach number (but still within the weakly compressible regime) strongly deteriorates the situation, although the magnitude of the errors may remain negligible for purely aerodynamic studies. A drastically reduced level of error for the near-field spurious noise is obtained with our approach, especially for under-resolved simulations, a situation that is crucial for industrial applications. Thus, the vortex case is proved useful for aeroacoustic validations of any grid refinement algorithm.

  10. Continuous method for refining sodium. [for use in LMFBR type reactors

    Energy Technology Data Exchange (ETDEWEB)

    Batoux, B; Laurent-Atthalin, A; Salmon, M

    1973-11-16

    The invention relates to a refining method according to which commercial sodium provides a high purity sodium with, in particular, a very small calcium content. The method consists in continuously feeding a predetermined amount of sodium peroxide into a sodium stream, mixing and causing said sodium peroxide to reach with sodium at an appropriate temperature, and, finally, separating the reaction products from sodium by decanting and filtering same. The thus obtained high purity sodium meets the requirements of atomic industries in particular, in view of its possible use as coolant in nuclear reactors of the ''breeder'' type.

  11. Using high-order methods on adaptively refined block-structured meshes - discretizations, interpolations, and filters.

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Jaideep; Lefantzi, Sophia; Najm, Habib N.; Kennedy, Christopher A.

    2006-01-01

    Block-structured adaptively refined meshes (SAMR) strive for efficient resolution of partial differential equations (PDEs) solved on large computational domains by clustering mesh points only where required by large gradients. Previous work has indicated that fourth-order convergence can be achieved on such meshes by using a suitable combination of high-order discretizations, interpolations, and filters and can deliver significant computational savings over conventional second-order methods at engineering error tolerances. In this paper, we explore the interactions between the errors introduced by discretizations, interpolations and filters. We develop general expressions for high-order discretizations, interpolations, and filters, in multiple dimensions, using a Fourier approach, facilitating the high-order SAMR implementation. We derive a formulation for the necessary interpolation order for given discretization and derivative orders. We also illustrate this order relationship empirically using one and two-dimensional model problems on refined meshes. We study the observed increase in accuracy with increasing interpolation order. We also examine the empirically observed order of convergence, as the effective resolution of the mesh is increased by successively adding levels of refinement, with different orders of discretization, interpolation, or filtering.

  12. Automatic mesh refinement and local multigrid methods for contact problems: application to the Pellet-Cladding mechanical Interaction

    International Nuclear Information System (INIS)

    Liu, Hao

    2016-01-01

    This Ph.D. work takes place within the framework of studies on Pellet-Cladding mechanical Interaction (PCI) which occurs in the fuel rods of pressurized water reactor. This manuscript focuses on automatic mesh refinement to simulate more accurately this phenomena while maintaining acceptable computational time and memory space for industrial calculations. An automatic mesh refinement strategy based on the combination of the Local Defect Correction multigrid method (LDC) with the Zienkiewicz and Zhu a posteriori error estimator is proposed. The estimated error is used to detect the zones to be refined, where the local sub-grids of the LDC method are generated. Several stopping criteria are studied to end the refinement process when the solution is accurate enough or when the refinement does not improve the global solution accuracy anymore. Numerical results for elastic 2D test cases with pressure discontinuity show the efficiency of the proposed strategy. The automatic mesh refinement in case of unilateral contact problems is then considered. The strategy previously introduced can be easily adapted to the multi-body refinement by estimating solution error on each body separately. Post-processing is often necessary to ensure the conformity of the refined areas regarding the contact boundaries. A variety of numerical experiments with elastic contact (with or without friction, with or without an initial gap) confirms the efficiency and adaptability of the proposed strategy. (author) [fr

  13. AN AUTOMATIC OPTICAL AND SAR IMAGE REGISTRATION METHOD USING ITERATIVE MULTI-LEVEL AND REFINEMENT MODEL

    Directory of Open Access Journals (Sweden)

    C. Xu

    2016-06-01

    Full Text Available Automatic image registration is a vital yet challenging task, particularly for multi-sensor remote sensing images. Given the diversity of the data, it is unlikely that a single registration algorithm or a single image feature will work satisfactorily for all applications. Focusing on this issue, the mainly contribution of this paper is to propose an automatic optical-to-SAR image registration method using –level and refinement model: Firstly, a multi-level strategy of coarse-to-fine registration is presented, the visual saliency features is used to acquire coarse registration, and then specific area and line features are used to refine the registration result, after that, sub-pixel matching is applied using KNN Graph. Secondly, an iterative strategy that involves adaptive parameter adjustment for re-extracting and re-matching features is presented. Considering the fact that almost all feature-based registration methods rely on feature extraction results, the iterative strategy improve the robustness of feature matching. And all parameters can be automatically and adaptively adjusted in the iterative procedure. Thirdly, a uniform level set segmentation model for optical and SAR images is presented to segment conjugate features, and Voronoi diagram is introduced into Spectral Point Matching (VSPM to further enhance the matching accuracy between two sets of matching points. Experimental results show that the proposed method can effectively and robustly generate sufficient, reliable point pairs and provide accurate registration.

  14. An angularly refineable phase space finite element method with approximate sweeping procedure

    International Nuclear Information System (INIS)

    Kophazi, J.; Lathouwers, D.

    2013-01-01

    An angularly refineable phase space finite element method is proposed to solve the neutron transport equation. The method combines the advantages of two recently published schemes. The angular domain is discretized into small patches and patch-wise discontinuous angular basis functions are restricted to these patches, i.e. there is no overlap between basis functions corresponding to different patches. This approach yields block diagonal Jacobians with small block size and retains the possibility for S n -like approximate sweeping of the spatially discontinuous elements in order to provide efficient preconditioners for the solution procedure. On the other hand, the preservation of the full FEM framework (as opposed to collocation into a high-order S n scheme) retains the possibility of the Galerkin interpolated connection between phase space elements at arbitrary levels of discretization. Since the basis vectors are not orthonormal, a generalization of the Riemann procedure is introduced to separate the incoming and outgoing contributions in case of unstructured meshes. However, due to the properties of the angular discretization, the Riemann procedure can be avoided at a large fraction of the faces and this fraction rapidly increases as the level of refinement increases, contributing to the computational efficiency. In this paper the properties of the discretization scheme are studied with uniform refinement using an iterative solver based on the S 2 sweep order of the spatial elements. The fourth order convergence of the scalar flux is shown as anticipated from earlier schemes and the rapidly decreasing fraction of required Riemann faces is illustrated. (authors)

  15. Effect of powder sample granularity on fluorescent intensity and on thermal parameters in x-ray diffraction Rietveld analysis

    International Nuclear Information System (INIS)

    Sparks, C.J.; Specht, E.D.; Ice, G.E.; Kumar, R.; Zschack, P.; Shiraishi, T.; Hisatsune, K.

    1991-01-01

    The effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu 50 Au 44 Ni 6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity. A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30 degrees 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce >5 μm particles and high packing densities

  16. Refinement-Animation for Event-B - Towards a Method of Validation

    DEFF Research Database (Denmark)

    Hallerstede, Stefan; Leuschel, Michael; Plagge, Daniel

    2010-01-01

    We provide a detailed description of refinement in Event-B, both as a contribution in itself and as a foundation for the approach to simultaneous animation of multiple levels of refinement that we propose. We present an algorithm for simultaneous multi-level animation of refinement, and show how ...

  17. Rietveld and impedance analysis of cold and hot rolled duplex and lean duplex steels for application in paper and pulp industry

    Energy Technology Data Exchange (ETDEWEB)

    Esteves, Luiza; Lins, Vanessa de Freitas Cunha, E-mail: luizaeq@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Quimica; Paiva, Paulo Renato Perdigao [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET), Belo Horizonte, MG (Brazil); Viana, Adolfo Kalergis do Nascimento [APERAM South America, Timoteo, MG (Brazil)

    2017-01-15

    In this study, X-Ray Diffraction (XRD) and Rietveld Refinement were performed to identify and quantify the ferrite and austenite phase of cold and hot rolled duplex stainless steels (UNS S31803) and lean duplex stainless steels (UNS S32304). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the chemical behavior of duplex and lean duplex stainless steels in white, green, and black liquors of paper and pulp industry. Rietveld analysis results showed a higher austenite content than the standard limit for duplex steels in the hot rolled condition. The hot rolling condition plays a major role in improving corrosion resistance in white liquor mainly for the lean duplex steel. (author)

  18. Rietveld and impedance analysis of cold and hot rolled duplex and lean duplex steels for application in paper and pulp industry

    International Nuclear Information System (INIS)

    Esteves, Luiza; Lins, Vanessa de Freitas Cunha; Viana, Adolfo Kalergis do Nascimento

    2017-01-01

    In this study, X-Ray Diffraction (XRD) and Rietveld Refinement were performed to identify and quantify the ferrite and austenite phase of cold and hot rolled duplex stainless steels (UNS S31803) and lean duplex stainless steels (UNS S32304). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the chemical behavior of duplex and lean duplex stainless steels in white, green, and black liquors of paper and pulp industry. Rietveld analysis results showed a higher austenite content than the standard limit for duplex steels in the hot rolled condition. The hot rolling condition plays a major role in improving corrosion resistance in white liquor mainly for the lean duplex steel. (author)

  19. New Ghost-node method for linking different models with varied grid refinement

    International Nuclear Information System (INIS)

    Mehl, Steffen W.; Hill, Mary Catherine; James, Scott Carlton; Leake, Stanley A.; Zyvoloski, George A.; Dickinson, Jesse E.; Eddebbarh, Al A.

    2006-01-01

    A flexible, robust method for linking grids of locally refined models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined 'child' model that is contained within a larger and coarser 'parent' model that is based on the iterative method of Mehl and Hill (2002, 2004). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has either matching grids (parent cells border an integer number of child cells; Figure 2a) or non-matching grids (parent cells border a non-integer number of child cells; Figure 2b). The coupled grids are simulated using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models (Mehl and Hill, 2002). When the grids are non-matching, model accuracy is slightly increased over matching-grid cases. Overall, results indicate that the ghost-node technique is a viable means to accurately couple distinct models because the overall error is less than if only the regional model was used to simulate flow in the child model's domain

  20. New ghost-node method for linking different models with varied grid refinement

    Science.gov (United States)

    James, S.C.; Dickinson, J.E.; Mehl, S.W.; Hill, M.C.; Leake, S.A.; Zyvoloski, G.A.; Eddebbarh, A.-A.

    2006-01-01

    A flexible, robust method for linking grids of locally refined ground-water flow models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined "child" model that is contained within a larger and coarser "parent" model that is based on the iterative method of Steffen W. Mehl and Mary C. Hill (2002, Advances in Water Res., 25, p. 497-511; 2004, Advances in Water Res., 27, p. 899-912). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has matching grids (parent cells border an integer number of child cells) or nonmatching grids. The coupled grids are simulated by using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child-cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models. When the grids are nonmatching, model accuracy is slightly increased compared to that for matching-grid cases. Overall, results indicate that the ghost-node technique is a viable means to couple distinct models because the overall head and flow errors relative to the analytical solution are less than if only the regional coarse-grid model was used to simulate flow in the child model's domain.

  1. Structural refinement of artificial superlattices by the X-ray diffraction method

    CERN Document Server

    Ishibashi, Y; Tsurumi, T

    1999-01-01

    This paper reports a structural refinement of BaTiO sub 3 (BTO)/SrTiO sub 3 (STO) artificially superstructured thin films. The refinement was achieved by taking into account the effect of interdiffusion between BTO and STO. The samples were prepared by a molecular-beam epitaxy method on SrTiO sub 3 (001) substrate at 600 .deg. C. The phonon model was employed to simulate the X-ray diffraction (XRD) profiles. A discrepancy was observed in the intensities of the satellite peaks when the effect of the interdiffusion between BTO and STO was not incorporated in the simulation. In successive simulations, the concentration profile due to the interdiffusion was first calculated according to Fick's second law, and then the coefficients of the Fourier series describing the lattice distortion and the modulation of the structure factor were determined. The XRD profiles thus simulated almost completely agreed with those observed. This indicates that XRD analysis with the calculation process proposed in this study will ena...

  2. The IPNS rietveld analysis software package for TOF [time-of-flight] powder diffraction data: Recent developments

    International Nuclear Information System (INIS)

    Rotella, F.J.; Richardson, J.W. Jr.

    1987-01-01

    A system of FORTRAN programs for the analysis of time-of-flight (TOF) neutron powder diffraction data via the Rietveld method at IPNS has been modified recently, making it possible to analyze data that exhibit diffraction maxima broadened due to anisotropic strain and that can be modeled by individual atomic anharmonic thermal vibrations. The observation of noncrystalline scattering in data from some powder samples has led to the development of software to fit such scattering by a function related to a radial distribution function through Fourier-filtering techniques. The ''user friendliness'' of the IPNS Rietveld package has been enhanced by the development of ''RIETVELD,'' a menu-based VAX/VMS command language routine for interactive file manipulation and program execution

  3. Lattice-Boltzmann Method with Dynamic Grid Refinement for Simulating Particle Deposition on a Single Fibre

    Directory of Open Access Journals (Sweden)

    Helmut Schomburg

    2013-03-01

    Full Text Available In this work a numerical approach to predict the deposition behaviour of nano-scale particles on the surface of a single fibre by resolving the resulting dendrite-like particle structures in detail is presented. The gas flow simulation is carried out by a two-dimensional Lattice-Boltzmann method, which is coupled with a Lagrangian approach for the particle motion. To decrease calculation time and system requirements the Lattice-Boltzmann model is extended to allow for local grid refinement. Because of the a priori unknown location of deposition, the simulation procedure starts on a coarse mesh which is then locally refined in a fully adaptive way in regions of accumulated particles. After each deposition the fluid flow is recalculated in order to resolve the coupling of the flow with the growing particle structures correctly. For the purpose of avoiding unphysical blocking of flow by growing particle dendrites the Lattice-Boltzmann method is extended to permeable cells in these regions using the Brinkmann equation. This extended deposition model is compared to simpler approaches, where the deposit has no retroaction on the flow or is treated as a solid structure. It is clear that the permeable model is most realistic and allows considering the particle deposition on a fibre as two-dimensional problem. Comprehensive simulations were conducted for analysing the importance of different parameters, i.e. free-stream velocity and particle diameter on the deposit structure. The results of this sensitivity analysis agree qualitatively well with former published numerical and experimental results. Finally the structure of the particle deposit was quantitatively characterised by using a modified fractal dimension.

  4. Stabilized Conservative Level Set Method with Adaptive Wavelet-based Mesh Refinement

    Science.gov (United States)

    Shervani-Tabar, Navid; Vasilyev, Oleg V.

    2016-11-01

    This paper addresses one of the main challenges of the conservative level set method, namely the ill-conditioned behavior of the normal vector away from the interface. An alternative formulation for reconstruction of the interface is proposed. Unlike the commonly used methods which rely on the unit normal vector, Stabilized Conservative Level Set (SCLS) uses a modified renormalization vector with diminishing magnitude away from the interface. With the new formulation, in the vicinity of the interface the reinitialization procedure utilizes compressive flux and diffusive terms only in the normal direction to the interface, thus, preserving the conservative level set properties, while away from the interfaces the directional diffusion mechanism automatically switches to homogeneous diffusion. The proposed formulation is robust and general. It is especially well suited for use with adaptive mesh refinement (AMR) approaches due to need for a finer resolution in the vicinity of the interface in comparison with the rest of the domain. All of the results were obtained using the Adaptive Wavelet Collocation Method, a general AMR-type method, which utilizes wavelet decomposition to adapt on steep gradients in the solution while retaining a predetermined order of accuracy.

  5. Acquiring and refining CBT skills and competencies: which training methods are perceived to be most effective?

    Science.gov (United States)

    Bennett-Levy, James; McManus, Freda; Westling, Bengt E; Fennell, Melanie

    2009-10-01

    A theoretical and empirical base for CBT training and supervision has started to emerge. Increasingly sophisticated maps of CBT therapist competencies have recently been developed, and there is evidence that CBT training and supervision can produce enhancement of CBT skills. However, the evidence base suggesting which specific training techniques are most effective for the development of CBT competencies is lacking. This paper addresses the question: What training or supervision methods are perceived by experienced therapists to be most effective for training CBT competencies? 120 experienced CBT therapists rated which training or supervision methods in their experience had been most effective in enhancing different types of therapy-relevant knowledge or skills. In line with the main prediction, it was found that different training methods were perceived to be differentially effective. For instance, reading, lectures/talks and modelling were perceived to be most useful for the acquisition of declarative knowledge, while enactive learning strategies (role-play, self-experiential work), together with modelling and reflective practice, were perceived to be most effective in enhancing procedural skills. Self-experiential work and reflective practice were seen as particularly helpful in improving reflective capability and interpersonal skills. The study provides a framework for thinking about the acquisition and refinement of therapist skills that may help trainers, supervisors and clinicians target their learning objectives with the most effective training strategies.

  6. Analysis of a HP-refinement method for solving the neutron transport equation using two error estimators

    International Nuclear Information System (INIS)

    Fournier, D.; Le Tellier, R.; Suteau, C.; Herbin, R.

    2011-01-01

    The solution of the time-independent neutron transport equation in a deterministic way invariably consists in the successive discretization of the three variables: energy, angle and space. In the SNATCH solver used in this study, the energy and the angle are respectively discretized with a multigroup approach and the discrete ordinate method. A set of spatial coupled transport equations is obtained and solved using the Discontinuous Galerkin Finite Element Method (DGFEM). Within this method, the spatial domain is decomposed into elements and the solution is approximated by a hierarchical polynomial basis in each one. This approach is time and memory consuming when the mesh becomes fine or the basis order high. To improve the computational time and the memory footprint, adaptive algorithms are proposed. These algorithms are based on an error estimation in each cell. If the error is important in a given region, the mesh has to be refined (h−refinement) or the polynomial basis order increased (p−refinement). This paper is related to the choice between the two types of refinement. Two ways to estimate the error are compared on different benchmarks. Analyzing the differences, a hp−refinement method is proposed and tested. (author)

  7. Wavelet-based Adaptive Mesh Refinement Method for Global Atmospheric Chemical Transport Modeling

    Science.gov (United States)

    Rastigejev, Y.

    2011-12-01

    Numerical modeling of global atmospheric chemical transport presents enormous computational difficulties, associated with simulating a wide range of time and spatial scales. The described difficulties are exacerbated by the fact that hundreds of chemical species and thousands of chemical reactions typically are used for chemical kinetic mechanism description. These computational requirements very often forces researches to use relatively crude quasi-uniform numerical grids with inadequate spatial resolution that introduces significant numerical diffusion into the system. It was shown that this spurious diffusion significantly distorts the pollutant mixing and transport dynamics for typically used grid resolution. The described numerical difficulties have to be systematically addressed considering that the demand for fast, high-resolution chemical transport models will be exacerbated over the next decade by the need to interpret satellite observations of tropospheric ozone and related species. In this study we offer dynamically adaptive multilevel Wavelet-based Adaptive Mesh Refinement (WAMR) method for numerical modeling of atmospheric chemical evolution equations. The adaptive mesh refinement is performed by adding and removing finer levels of resolution in the locations of fine scale development and in the locations of smooth solution behavior accordingly. The algorithm is based on the mathematically well established wavelet theory. This allows us to provide error estimates of the solution that are used in conjunction with an appropriate threshold criteria to adapt the non-uniform grid. Other essential features of the numerical algorithm include: an efficient wavelet spatial discretization that allows to minimize the number of degrees of freedom for a prescribed accuracy, a fast algorithm for computing wavelet amplitudes, and efficient and accurate derivative approximations on an irregular grid. The method has been tested for a variety of benchmark problems

  8. A new method for grain refinement in magnesium alloy: High speed extrusion machining

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yao, E-mail: liuyao@ustb.edu.cn [School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083 (China); Cai, Songlin [China Electric Power Research Institute, State Grid Corporation of China, Beijing 100192 (China); Dai, Lanhong [State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Science, Beijing 100190 (China)

    2016-01-10

    Magnesium alloys have received broad attentions in industry due to their competitive strength to density ratio, but the poor ductility and strength limit their wide range of applications as engineering materials. A novel severe plastic deformation (SPD) technique of high speed extrusion machining (HSEM) was used here. This method could improve the aforementioned disadvantages of magnesium alloys by one single processing step. In this work, systematic HSEM experiments with different chip thickness ratios were conducted for magnesium alloy AZ31B. The microstructure of the chips reveals that HSEM is an effective SPD method for attaining magnesium alloys with different grain sizes and textures. The magnesium alloy with bimodal grain size distribution has increased mechanical properties than initial sample. The electron backscatter diffraction (EBSD) analysis shows that the dynamic recrystallization (DRX) affects the grain refinement and resulting hardness in AZ31B. Based on the experimental observations, a new theoretical model is put forward to describe the effect of DRX on materials during HSEM. Compared with the experimental measurements, the theoretical model is effective to predict the mechanical property of materials after HSEM.

  9. Refinement and fracture mechanisms of as-cast QT700-6 alloy by alloying method

    Directory of Open Access Journals (Sweden)

    Min-qiang Gao

    2017-01-01

    Full Text Available The as-cast QT700-6 alloy was synthesized with addition of a certain amount of copper, nickel, niobium and stannum elements by alloying method in a medium frequency induction furnace, aiming at improving its strength and toughness. Microstructures of the as-cast QT700-6 alloy were observed using a scanning-electron microscope (SEM and the mechanical properties were investigated using a universal tensile test machine. Results indicate that the ratio of pearlite/ferrite is about 9:1 and the graphite size is less than 40 μm in diameter in the as-cast QT700-6 alloy. The predominant refinement mechanism is attributed to the formation of niobium carbides, which increases the heterogeneous nucleus and hinders the growth of graphite. Meanwhile, niobium carbides also exist around the grain boundaries, which improve the strength of the ductile iron. The tensile strength and elongation of the as-cast QT700-6 alloy reach over 700 MPa and 6%, respectively, when the addition amount of niobium is 0.8%. The addition of copper and nickel elements contributed to the decrease of eutectoid transformation temperature, resulting in the decrease of pearlite lamellar spacing (about 248 nm, which is also beneficial to enhancing the tensile strength. The main fracture mechanism is cleavage fracture with the appearance of a small amount of dimples.

  10. Method of preparing an Al-Ti-B grain refiner for aluminium-comprising products, and a method of casting aluminium products

    OpenAIRE

    Brinkman, H.J.; Duszczyk, J.; Katgerman, L.

    1999-01-01

    The invention relates to a method of preparing an Al-Ti-B grain refiner for cast aluminium-comprising products. According to the invention the preparation is realized by mixing powders selected from the group comprising aluminium, titanium, boron, and alloys and intermetallic compounds thereof, compressing, heating in an inert environment until an exothermic reaction is initiated and cooling. It has been shown that when the grain refiner thus prepared is applied, the quality of cast products ...

  11. Quantitative Mineralogical Analysis of Mars Analogues Using CHEMIN Data and Rietveld Refinement

    Science.gov (United States)

    Bish, D. L.; Sarrazin, P.; Chipera, S. J.; Vaniman, D. T.; Blake, D.

    2004-01-01

    Mineralogical analysis is a critical component of planetary surface exploration. Chemical data alone leave serious gaps in our understanding of the surfaces of planets where complex minerals may form in combination with H, S, and halogens. On such planets (e.g., Mars) a single chemical composition may represent a range of mineral assemblages. For example, Viking chemical analyses of excavated duricrust indicate that Mg and S are correlated and 10% MgSO4 (anhydrous weight) is a likely cementing agent. Pathfinder chemical data support a similar abundance of MgSO4 in the most altered materials. However, there are many possible Mg-sulfates with widely varying hydration states (including dehydrated and 1-, 2-, 3-, 4-, 5-, 6-, and 7-hydrates). In addition, other sulfate minerals such as gypsum (CaSO4 .2H2O) and other salts containing Cl may also exist. X-ray diffraction (XRD) has the ability to decipher mixtures of these phases that would be difficult, if not impossible to unravel using only chemical or spectral data.

  12. Rietveld refinement of KLaTiO4 from X-ray powder data

    Directory of Open Access Journals (Sweden)

    Bai-Chuan Zhu

    2011-04-01

    Full Text Available Potassium lanthanum titanate(IV, KLaTiO4, has been synthesized by conventional solid-state reaction. It crystallizes isotypically with the NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu family. Five of the six atoms in the asymmetric unit (one K, one La, one Ti and two O atoms are situated on sites with 4mm symmetry, whereas one O atom has 2mm. site symmetry. The crystal structure can be described as being composed of single layers of distorted corner-sharing TiO6 octahedra extending parallel to (001. The layers are alternately separated by K+ and La3+ cations along [001]. The coordination number of both K+ and La3+ cations is nine, resulting in distorted KO9 and LaO9 polyhedra.

  13. Method of cleansing and refining of liquid hydrocarbons and derivatives of hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, C A; Nielsen, H

    1934-10-11

    A process is described for cleaning and refining liquid hydrocarbons and derivatives by utilization of acids, followed by washing partly with a basic solution, partly with clean water. The process is characterized by using, in connection with the acid solutions mentioned, a strong solution of a mixture of sulfuric acid and phosphoric acid.

  14. Adaptive Mesh Refinement and High Order Geometrical Moment Method for the Simulation of Polydisperse Evaporating Sprays

    Directory of Open Access Journals (Sweden)

    Essadki Mohamed

    2016-09-01

    Full Text Available Predictive simulation of liquid fuel injection in automotive engines has become a major challenge for science and applications. The key issue in order to properly predict various combustion regimes and pollutant formation is to accurately describe the interaction between the carrier gaseous phase and the polydisperse evaporating spray produced through atomization. For this purpose, we rely on the EMSM (Eulerian Multi-Size Moment Eulerian polydisperse model. It is based on a high order moment method in size, with a maximization of entropy technique in order to provide a smooth reconstruction of the distribution, derived from a Williams-Boltzmann mesoscopic model under the monokinetic assumption [O. Emre (2014 PhD Thesis, École Centrale Paris; O. Emre, R.O. Fox, M. Massot, S. Chaisemartin, S. Jay, F. Laurent (2014 Flow, Turbulence and Combustion 93, 689-722; O. Emre, D. Kah, S. Jay, Q.-H. Tran, A. Velghe, S. de Chaisemartin, F. Laurent, M. Massot (2015 Atomization Sprays 25, 189-254; D. Kah, F. Laurent, M. Massot, S. Jay (2012 J. Comput. Phys. 231, 394-422; D. Kah, O. Emre, Q.-H. Tran, S. de Chaisemartin, S. Jay, F. Laurent, M. Massot (2015 Int. J. Multiphase Flows 71, 38-65; A. Vié, F. Laurent, M. Massot (2013 J. Comp. Phys. 237, 277-310]. The present contribution relies on a major extension of this model [M. Essadki, S. de Chaisemartin, F. Laurent, A. Larat, M. Massot (2016 Submitted to SIAM J. Appl. Math.], with the aim of building a unified approach and coupling with a separated phases model describing the dynamics and atomization of the interface near the injector. The novelty is to be found in terms of modeling, numerical schemes and implementation. A new high order moment approach is introduced using fractional moments in surface, which can be related to geometrical quantities of the gas-liquid interface. We also provide a novel algorithm for an accurate resolution of the evaporation. Adaptive mesh refinement properly scaling on massively

  15. Refining revolution

    Energy Technology Data Exchange (ETDEWEB)

    Fesharaki, F.; Isaak, D.

    1984-01-01

    A review of changes in the oil refining industry since 1973 examines the drop in capacity use and its effect on profits of the Organization of Economic Cooperation and Development (OECD) countries compared to world refining. OPEC countries used their new oil revenues to expand Gulf refineries, which put additional pressure on OECD refiners. OPEC involvement in global marketing, however, could help to secure supplies. Scrapping some older OECD refineries could improve the percentage of capacity in use if new construction is kept to a minimum. Other issues facing refiners are the changes in oil demand patterns and government responses to the market. 2 tables.

  16. A rich solution spray as a refining method in a small capacity, single effect, solar assisted absorption machine with the pair NH3/H2O: Experimental results

    International Nuclear Information System (INIS)

    Mendes, L.F.; Collares-Pereira, M.; Ziegler, F.

    2007-01-01

    Ammonia vapour refining is a common procedure in ammonia-water absorption machines. A solar assisted single effect absorption machine that uses the pair ammonia-water was developed and tested. Its desorber has a built-in adiabatic refining column constituted by a rich solution spray. The refining method proved its feasibility. The spray provided a more or less constant ammonia vapour enrichment of about 1% which is enough for the working temperature ranges of this type of machine. It was also verified that the refining effect of the spray is almost independent of the refrigerant vapour and solution mass flow rates

  17. Method of preparing an Al-Ti-B grain refiner for aluminium-comprising products, and a method of casting aluminium products

    NARCIS (Netherlands)

    Brinkman, H.J.; Duszczyk, J.; Katgerman, L.

    1999-01-01

    The invention relates to a method of preparing an Al-Ti-B grain refiner for cast aluminium-comprising products. According to the invention the preparation is realized by mixing powders selected from the group comprising aluminium, titanium, boron, and alloys and intermetallic compounds thereof,

  18. Application of the heat-balance and refined integral methods to the Korteweg-de Vries equation

    Directory of Open Access Journals (Sweden)

    Myers Timothy G.

    2009-01-01

    Full Text Available In this paper we consider approximate travelling wave solutions to the Korteweg-de Vries equation. The heat-balance integral method is first applied to the problem, using two different quartic approximating functions, and then the refined integral method is investigated. We examine two types of solution, chosen by matching the wave speed to that of the exact solution and by imposing the same area. The first set of solutions is generally better with an error that is fixed in time. The second set of solutions has an error that grows with time. This is shown to be due to slight discrepancies in the wave speed.

  19. A high-order finite-volume method for hyperbolic conservation laws on locally-refined grids

    Energy Technology Data Exchange (ETDEWEB)

    McCorquodale, Peter; Colella, Phillip

    2011-01-28

    We present a fourth-order accurate finite-volume method for solving time-dependent hyperbolic systems of conservation laws on Cartesian grids with multiple levels of refinement. The underlying method is a generalization of that in [5] to nonlinear systems, and is based on using fourth-order accurate quadratures for computing fluxes on faces, combined with fourth-order accurate Runge?Kutta discretization in time. To interpolate boundary conditions at refinement boundaries, we interpolate in time in a manner consistent with the individual stages of the Runge-Kutta method, and interpolate in space by solving a least-squares problem over a neighborhood of each target cell for the coefficients of a cubic polynomial. The method also uses a variation on the extremum-preserving limiter in [8], as well as slope flattening and a fourth-order accurate artificial viscosity for strong shocks. We show that the resulting method is fourth-order accurate for smooth solutions, and is robust in the presence of complex combinations of shocks and smooth flows.

  20. Liver segmentation in contrast enhanced CT data using graph cuts and interactive 3D segmentation refinement methods

    International Nuclear Information System (INIS)

    Beichel, Reinhard; Bornik, Alexander; Bauer, Christian; Sorantin, Erich

    2012-01-01

    Purpose: Liver segmentation is an important prerequisite for the assessment of liver cancer treatment options like tumor resection, image-guided radiation therapy (IGRT), radiofrequency ablation, etc. The purpose of this work was to evaluate a new approach for liver segmentation. Methods: A graph cuts segmentation method was combined with a three-dimensional virtual reality based segmentation refinement approach. The developed interactive segmentation system allowed the user to manipulate volume chunks and/or surfaces instead of 2D contours in cross-sectional images (i.e, slice-by-slice). The method was evaluated on twenty routinely acquired portal-phase contrast enhanced multislice computed tomography (CT) data sets. An independent reference was generated by utilizing a currently clinically utilized slice-by-slice segmentation method. After 1 h of introduction to the developed segmentation system, three experts were asked to segment all twenty data sets with the proposed method. Results: Compared to the independent standard, the relative volumetric segmentation overlap error averaged over all three experts and all twenty data sets was 3.74%. Liver segmentation required on average 16 min of user interaction per case. The calculated relative volumetric overlap errors were not found to be significantly different [analysis of variance (ANOVA) test, p = 0.82] between experts who utilized the proposed 3D system. In contrast, the time required by each expert for segmentation was found to be significantly different (ANOVA test, p = 0.0009). Major differences between generated segmentations and independent references were observed in areas were vessels enter or leave the liver and no accepted criteria for defining liver boundaries exist. In comparison, slice-by-slice based generation of the independent standard utilizing a live wire tool took 70.1 min on average. A standard 2D segmentation refinement approach applied to all twenty data sets required on average 38.2 min of

  1. Liver segmentation in contrast enhanced CT data using graph cuts and interactive 3D segmentation refinement methods

    Energy Technology Data Exchange (ETDEWEB)

    Beichel, Reinhard; Bornik, Alexander; Bauer, Christian; Sorantin, Erich [Departments of Electrical and Computer Engineering and Internal Medicine, Iowa Institute for Biomedical Imaging, University of Iowa, Iowa City, Iowa 52242 (United States); Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16, A-8010 Graz (Austria); Department of Electrical and Computer Engineering, Iowa Institute for Biomedical Imaging, University of Iowa, Iowa City, Iowa 52242 (United States); Department of Radiology, Medical University Graz, Auenbruggerplatz 34, A-8010 Graz (Austria)

    2012-03-15

    Purpose: Liver segmentation is an important prerequisite for the assessment of liver cancer treatment options like tumor resection, image-guided radiation therapy (IGRT), radiofrequency ablation, etc. The purpose of this work was to evaluate a new approach for liver segmentation. Methods: A graph cuts segmentation method was combined with a three-dimensional virtual reality based segmentation refinement approach. The developed interactive segmentation system allowed the user to manipulate volume chunks and/or surfaces instead of 2D contours in cross-sectional images (i.e, slice-by-slice). The method was evaluated on twenty routinely acquired portal-phase contrast enhanced multislice computed tomography (CT) data sets. An independent reference was generated by utilizing a currently clinically utilized slice-by-slice segmentation method. After 1 h of introduction to the developed segmentation system, three experts were asked to segment all twenty data sets with the proposed method. Results: Compared to the independent standard, the relative volumetric segmentation overlap error averaged over all three experts and all twenty data sets was 3.74%. Liver segmentation required on average 16 min of user interaction per case. The calculated relative volumetric overlap errors were not found to be significantly different [analysis of variance (ANOVA) test, p = 0.82] between experts who utilized the proposed 3D system. In contrast, the time required by each expert for segmentation was found to be significantly different (ANOVA test, p = 0.0009). Major differences between generated segmentations and independent references were observed in areas were vessels enter or leave the liver and no accepted criteria for defining liver boundaries exist. In comparison, slice-by-slice based generation of the independent standard utilizing a live wire tool took 70.1 min on average. A standard 2D segmentation refinement approach applied to all twenty data sets required on average 38.2 min of

  2. Development of an object oriented nodal code using the refined AFEN derived from the method of component decomposition

    International Nuclear Information System (INIS)

    Noh, J. M.; Yoo, J. W.; Joo, H. K.

    2004-01-01

    In this study, we invented a method of component decomposition to derive the systematic inter-nodal coupled equations of the refined AFEN method and developed an object oriented nodal code to solve the derived coupled equations. The method of component decomposition decomposes the intra-nodal flux expansion of a nodal method into even and odd components in three dimensions to reduce the large coupled linear system equation into several small single equations. This method requires no additional technique to accelerate the iteration process to solve the inter-nodal coupled equations, since the derived equations can automatically act as the coarse mesh re-balance equations. By utilizing the object oriented programming concepts such as abstraction, encapsulation, inheritance and polymorphism, dynamic memory allocation, and operator overloading, we developed an object oriented nodal code that can facilitate the input/output and the dynamic control of the memories, and can make the maintenance easy. (authors)

  3. Liver segmentation in contrast enhanced CT data using graph cuts and interactive 3D segmentation refinement methods.

    Science.gov (United States)

    Beichel, Reinhard; Bornik, Alexander; Bauer, Christian; Sorantin, Erich

    2012-03-01

    Liver segmentation is an important prerequisite for the assessment of liver cancer treatment options like tumor resection, image-guided radiation therapy (IGRT), radiofrequency ablation, etc. The purpose of this work was to evaluate a new approach for liver segmentation. A graph cuts segmentation method was combined with a three-dimensional virtual reality based segmentation refinement approach. The developed interactive segmentation system allowed the user to manipulate volume chunks and∕or surfaces instead of 2D contours in cross-sectional images (i.e, slice-by-slice). The method was evaluated on twenty routinely acquired portal-phase contrast enhanced multislice computed tomography (CT) data sets. An independent reference was generated by utilizing a currently clinically utilized slice-by-slice segmentation method. After 1 h of introduction to the developed segmentation system, three experts were asked to segment all twenty data sets with the proposed method. Compared to the independent standard, the relative volumetric segmentation overlap error averaged over all three experts and all twenty data sets was 3.74%. Liver segmentation required on average 16 min of user interaction per case. The calculated relative volumetric overlap errors were not found to be significantly different [analysis of variance (ANOVA) test, p = 0.82] between experts who utilized the proposed 3D system. In contrast, the time required by each expert for segmentation was found to be significantly different (ANOVA test, p = 0.0009). Major differences between generated segmentations and independent references were observed in areas were vessels enter or leave the liver and no accepted criteria for defining liver boundaries exist. In comparison, slice-by-slice based generation of the independent standard utilizing a live wire tool took 70.1 min on average. A standard 2D segmentation refinement approach applied to all twenty data sets required on average 38.2 min of user interaction

  4. Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

    International Nuclear Information System (INIS)

    Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.; Faber, J. Jr.

    1989-11-01

    Uranium silicides have been considered for use as reactor fuels in both high power and low enrichment applications. However, U 3 Si was found to become amorphous under irradiation and to become mechanically unstable to rapid growth by plastic flow. U 2 Si 2 appears to be stable against amorphization at low displacement rates, but the extent of this stability is uncertain. Although the mechanisms responsible for plastic flow in U 3 Si and other amorphous systems are unknown, as is the importance of crystal structure for amorphization, it may not be surprising that these materials amorphize, in light of the fact that many radioactive nuclide - containing minerals are known to metaminctize (lose crystallinity) under irradiation. The present experiment follows the detailed changes in the crystal structures of U 3 Si and U 3 Si 2 introduced by neutron bombardment and subsequent uranium fission at room temperature. U-Si seems the ideal system for a neutron diffraction investigation since the crystallographic and amorphous forms can be studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering of the non-crystalline scattering component

  5. Refined Diebold-Mariano Test Methods for the Evaluation of Wind Power Forecasting Models

    Directory of Open Access Journals (Sweden)

    Hao Chen

    2014-07-01

    Full Text Available The scientific evaluation methodology for the forecast accuracy of wind power forecasting models is an important issue in the domain of wind power forecasting. However, traditional forecast evaluation criteria, such as Mean Squared Error (MSE and Mean Absolute Error (MAE, have limitations in application to some degree. In this paper, a modern evaluation criterion, the Diebold-Mariano (DM test, is introduced. The DM test can discriminate the significant differences of forecasting accuracy between different models based on the scheme of quantitative analysis. Furthermore, the augmented DM test with rolling windows approach is proposed to give a more strict forecasting evaluation. By extending the loss function to an asymmetric structure, the asymmetric DM test is proposed. Case study indicates that the evaluation criteria based on DM test can relieve the influence of random sample disturbance. Moreover, the proposed augmented DM test can provide more evidence when the cost of changing models is expensive, and the proposed asymmetric DM test can add in the asymmetric factor, and provide practical evaluation of wind power forecasting models. It is concluded that the two refined DM tests can provide reference to the comprehensive evaluation for wind power forecasting models.

  6. 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.

  7. Discontinuous Galerkin finite element method with anisotropic local grid refinement for inviscid compressible flows

    NARCIS (Netherlands)

    van der Vegt, Jacobus J.W.; van der Ven, H.

    1998-01-01

    A new discretization method for the three-dimensional Euler equations of gas dynamics is presented, which is based on the discontinuous Galerkin finite element method. Special attention is paid to an efficient implementation of the discontinuous Galerkin method that minimizes the number of flux

  8. Fourier Collocation Approach With Mesh Refinement Method for Simulating Transit-Time Ultrasonic Flowmeters Under Multiphase Flow Conditions.

    Science.gov (United States)

    Simurda, Matej; Duggen, Lars; Basse, Nils T; Lassen, Benny

    2018-02-01

    A numerical model for transit-time ultrasonic flowmeters operating under multiphase flow conditions previously presented by us is extended by mesh refinement and grid point redistribution. The method solves modified first-order stress-velocity equations of elastodynamics with additional terms to account for the effect of the background flow. Spatial derivatives are calculated by a Fourier collocation scheme allowing the use of the fast Fourier transform, while the time integration is realized by the explicit third-order Runge-Kutta finite-difference scheme. The method is compared against analytical solutions and experimental measurements to verify the benefit of using mapped grids. Additionally, a study of clamp-on and in-line ultrasonic flowmeters operating under multiphase flow conditions is carried out.

  9. Some refinements on the comparison of areal sampling methods via simulation

    Science.gov (United States)

    Jeffrey Gove

    2017-01-01

    The design of forest inventories and development of new sampling methods useful in such inventories normally have a two-fold target of design unbiasedness and minimum variance in mind. Many considerations such as costs go into the choices of sampling method for operational and other levels of inventory. However, the variance in terms of meeting a specified level of...

  10. Gerrit Rietveld. Casas después de la Schroeder

    Directory of Open Access Journals (Sweden)

    Rafael García

    1997-07-01

    Full Text Available Las historias de la arquitectura moderna han incidido una y otra vez en un reducido número de obras que por su insistente atención, han llegado a convertirse en hitos imprescindibles. Entre estos edificios canónicos y prácticamente obligados, está la célebre casa Schröder-Schräder (1924' del arquitecto holandés Gerrit Rietveld. Ampliamente conocida por el público interesado, su gran popularidad ha tenido sin embargo, el efecto de dejar en segundo plano el resto de su obra arquitectónica. A ello se debe añadir además, el hecho de que su trayectoria está fundamentalmente asociada al movimiento neoplasticista, lo que ha tenido por resultado desviar la atención de una obra posterior, más difícilmente clasificable. Sin embargo, ello no significa que dicha obra sea en absoluto carente de atractivo.

  11. Crystal structure refinement of α-Si3N4 using synchrotron radiation powder diffraction data: unbiased refinement strategy

    International Nuclear Information System (INIS)

    Toraya, H.

    2000-01-01

    The crystal structure of α-silicon nitride (Si 3 N 4 ) was refined by the Rietveld method using synchrotron radiation powder diffraction data (wavelength = 1.2 A) collected at station BL-4B2 in the photon factory. A refinement procedure that adopted a new weight function, w = 1/Y o e (Y o is the observed profile intensity and e ≅ 2), for the least-squares fitting [Toraya (1998). J. Appl. Cryst. 31, 333-343] was studied. The most reasonable structural parameters were obtained with e = 1.7. Crystal data of α-Si 3 N 4 : trigonal, P31c, a = 7.75193 (3), c = 5.61949 (4) A, V = 292.447 (3) A 3 , Z = 4; R p = 5.08, R wp = 6.50, R B = 3.36, R F = 2.26%. The following five factors are considered equally important for deriving accurate structural parameters from powder diffraction data: (i) sufficiently large sin θ/λ range of >0.8 A -1 ; (ii) adequate counting statistics; (iii) correct profile model; (iv) proper weighting on observations to give a uniform distribution of the mean weighted squared residuals; (v) high-angular-resolution powder diffraction data. (orig.)

  12. Conservative multi-implicit integral deferred correction methods with adaptive mesh refinement

    International Nuclear Information System (INIS)

    Layton, A.T.

    2004-01-01

    In most models of reacting gas dynamics, the characteristic time scales of chemical reactions are much shorter than the hydrodynamic and diffusive time scales, rendering the reaction part of the model equations stiff. Moreover, nonlinear forcings may introduce into the solutions sharp gradients or shocks, the robust behavior and correct propagation of which require the use of specialized spatial discretization procedures. This study presents high-order conservative methods for the temporal integration of model equations of reacting flows. By means of a method of lines discretization on the flux difference form of the equations, these methods compute approximations to the cell-averaged or finite-volume solution. The temporal discretization is based on a multi-implicit generalization of integral deferred correction methods. The advection term is integrated explicitly, and the diffusion and reaction terms are treated implicitly but independently, with the splitting errors present in traditional operator splitting methods reduced via the integral deferred correction procedure. To reduce computational cost, time steps used to integrate processes with widely-differing time scales may differ in size. (author)

  13. Action Refinement

    NARCIS (Netherlands)

    Gorrieri, R.; Rensink, Arend; Bergstra, J.A.; Ponse, A.; Smolka, S.A.

    2001-01-01

    In this chapter, we give a comprehensive overview of the research results in the field of action refinement during the past 12 years. The different approaches that have been followed are outlined in detail and contrasted to each other in a uniform framework. We use two running examples to discuss

  14. Patched based methods for adaptive mesh refinement solutions of partial differential equations

    Energy Technology Data Exchange (ETDEWEB)

    Saltzman, J.

    1997-09-02

    This manuscript contains the lecture notes for a course taught from July 7th through July 11th at the 1997 Numerical Analysis Summer School sponsored by C.E.A., I.N.R.I.A., and E.D.F. The subject area was chosen to support the general theme of that year`s school which is ``Multiscale Methods and Wavelets in Numerical Simulation.`` The first topic covered in these notes is a description of the problem domain. This coverage is limited to classical PDEs with a heavier emphasis on hyperbolic systems and constrained hyperbolic systems. The next topic is difference schemes. These schemes are the foundation for the adaptive methods. After the background material is covered, attention is focused on a simple patched based adaptive algorithm and its associated data structures for square grids and hyperbolic conservation laws. Embellishments include curvilinear meshes, embedded boundary and overset meshes. Next, several strategies for parallel implementations are examined. The remainder of the notes contains descriptions of elliptic solutions on the mesh hierarchy, elliptically constrained flow solution methods and elliptically constrained flow solution methods with diffusion.

  15. Structure of incommensurate ammonium tetrafluoroberyllate studied by structure refinements and the maximum entropy method

    Czech Academy of Sciences Publication Activity Database

    Palatinus, Lukáš; Amami, M.; van Smaalen, S.

    2004-01-01

    Roč. 60, - (2004), s. 127-137 ISSN 0108-7681 Grant - others:DFG(DE) XX Institutional research plan: CEZ:AV0Z1010914 Keywords : incommensurate modulation * superspace * maximum entropy method Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.418, year: 2004

  16. Synthesis mechanism of an Al-Ti-C grain refiner master alloy prepared by a new method

    Science.gov (United States)

    Zhang, B. Q.; Lu, L.; Lai, M. O.; Fang, H. S.; Ma, H. T.; Li, J. G.

    2003-08-01

    The mechanisms of in-situ synthesis of an Al-Ti-C grain-refiner master alloy, prepared by adding a powder mixture of potassium titanium fluoride and carbon into an aluminum melt, have been systematically studied. It was found that vigorous reactions occurred at the initial stage of reaction and then slowed down. After about 20 minutes, the reactions, which led the formation of blocky titanium aluminides and submicron titanium carbides in the aluminum matrix, appeared to reach completion. Potassium titanium fluoride reacted with aluminum and carbon at 724 °C and 736 °C, respectively, resulting in the formation of titanium aluminides and titanium carbides in the aluminum matrix as well as in the formation of a low-melting-point slag of binary potassium aluminofluorides. The reaction between potassium titanium fluoride and carbon is believed to be the predominant mechanism in the synthesis of TiC by this method.

  17. A refinement of the potassium tracer method for residential wood smoke

    Science.gov (United States)

    Calloway, C. P.; Li, S.; Buchanan, J. W.; Stevens, R. K.

    Potassium has been used as a tracer for the mass of fine particles emitted to the air from residential wood burning stoves and fireplaces. The technique involves measurement by x-ray fluorescence of the total K collected on fine particle filters. Since wind blown soil particles also contain K, a correction for this contribution is made based upon soil analysis or an assumed K/Fe ratio in local soil. K in excess of this ratio is considered to be from wood smoke. The purpose of this study is to demonstrate an alternative method for determining wood smoke K. The underlying assumption is that wood smoke K is water soluble but that K in crustal particles is in a mineralized form and only slightly water soluble. Results from analyses of particle samples indicate the two methods yield essentially the same amount of wood smoke K.

  18. Towards automated crystallographic structure refinement with phenix.refine

    Energy Technology Data Exchange (ETDEWEB)

    Afonine, Pavel V., E-mail: pafonine@lbl.gov; Grosse-Kunstleve, Ralf W.; Echols, Nathaniel; Headd, Jeffrey J.; Moriarty, Nigel W. [Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720 (United States); Mustyakimov, Marat; Terwilliger, Thomas C. [Los Alamos National Laboratory, M888, Los Alamos, NM 87545 (United States); Urzhumtsev, Alexandre [CNRS–INSERM–UdS, 1 Rue Laurent Fries, BP 10142, 67404 Illkirch (France); Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy (France); Zwart, Peter H. [Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720 (United States); Adams, Paul D. [Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720 (United States); University of California Berkeley, Berkeley, CA 94720 (United States)

    2012-04-01

    phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. This paper presents an overview of the major phenix.refine features, with extensive literature references for readers interested in more detailed discussions of the methods. phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. It has several automation features and is also highly flexible. Several hundred parameters enable extensive customizations for complex use cases. Multiple user-defined refinement strategies can be applied to specific parts of the model in a single refinement run. An intuitive graphical user interface is available to guide novice users and to assist advanced users in managing refinement projects. X-ray or neutron diffraction data can be used separately or jointly in refinement. phenix.refine is tightly integrated into the PHENIX suite, where it serves as a critical component in automated model building, final structure refinement, structure validation and deposition to the wwPDB. This paper presents an overview of the major phenix.refine features, with extensive literature references for readers interested in more detailed discussions of the methods.

  19. Molecular Structure-Based Methods of Property Prediction in Application to Lipids: A Review and Refinement

    DEFF Research Database (Denmark)

    Cunico, Larissa; Hukkerikar, Amol; Ceriani, Roberta

    2013-01-01

    The paper is a review of the combined group contribution (GC)–atom connectivity index (CI) approachfor prediction of physical and thermodynamic properties of organic chemicals and their mixtures withspecial emphasis on lipids. The combined approach employs carefully selected datasets of different...... dependent, have been developed. For mixtures, properties related to phase equilibria aremodeled with GE-based models (UNIQUAC, UNIFAC, NRTL, and combined UNIFAC-CI method). The col-lected phase equilibrium data for VLE and SLE have been tested for thermodynamic consistency togetherwith a performance...... evaluation of the GE-models. The paper also reviews the role of the databases andthe mathematical and thermodynamic consistency of the measured/estimated data and the predictivenature of the developed models....

  20. Pareto-Lognormal Modeling of Known and Unknown Metal Resources. II. Method Refinement and Further Applications

    International Nuclear Information System (INIS)

    Agterberg, Frits

    2017-01-01

    Pareto-lognormal modeling of worldwide metal deposit size–frequency distributions was proposed in an earlier paper (Agterberg in Nat Resour 26:3–20, 2017). In the current paper, the approach is applied to four metals (Cu, Zn, Au and Ag) and a number of model improvements are described and illustrated in detail for copper and gold. The new approach has become possible because of the very large inventory of worldwide metal deposit data recently published by Patiño Douce (Nat Resour 25:97–124, 2016c). Worldwide metal deposits for Cu, Zn and Ag follow basic lognormal size–frequency distributions that form straight lines on lognormal Q–Q plots. Au deposits show a departure from the straight-line model in the vicinity of their median size. Both largest and smallest deposits for the four metals taken as examples exhibit hyperbolic size–frequency relations and their Pareto coefficients are determined by fitting straight lines on log rank–log size plots. As originally pointed out by Patiño Douce (Nat Resour Res 25:365–387, 2016d), the upper Pareto tail cannot be distinguished clearly from the tail of what would be a secondary lognormal distribution. The method previously used in Agterberg (2017) for fitting the bridge function separating the largest deposit size–frequency Pareto tail from the basic lognormal is significantly improved in this paper. A new method is presented for estimating the approximate deposit size value at which the upper tail Pareto comes into effect. Although a theoretical explanation of the proposed Pareto-lognormal distribution model is not a required condition for its applicability, it is shown that existing double Pareto-lognormal models based on Brownian motion generalizations of the multiplicative central limit theorem are not applicable to worldwide metal deposits. Neither are various upper tail frequency amplification models in their present form. Although a physicochemical explanation remains possible, it is argued that

  1. Pareto-Lognormal Modeling of Known and Unknown Metal Resources. II. Method Refinement and Further Applications

    Energy Technology Data Exchange (ETDEWEB)

    Agterberg, Frits, E-mail: agterber@nrcan.gc.ca [Geological Survey of Canada (Canada)

    2017-07-01

    Pareto-lognormal modeling of worldwide metal deposit size–frequency distributions was proposed in an earlier paper (Agterberg in Nat Resour 26:3–20, 2017). In the current paper, the approach is applied to four metals (Cu, Zn, Au and Ag) and a number of model improvements are described and illustrated in detail for copper and gold. The new approach has become possible because of the very large inventory of worldwide metal deposit data recently published by Patiño Douce (Nat Resour 25:97–124, 2016c). Worldwide metal deposits for Cu, Zn and Ag follow basic lognormal size–frequency distributions that form straight lines on lognormal Q–Q plots. Au deposits show a departure from the straight-line model in the vicinity of their median size. Both largest and smallest deposits for the four metals taken as examples exhibit hyperbolic size–frequency relations and their Pareto coefficients are determined by fitting straight lines on log rank–log size plots. As originally pointed out by Patiño Douce (Nat Resour Res 25:365–387, 2016d), the upper Pareto tail cannot be distinguished clearly from the tail of what would be a secondary lognormal distribution. The method previously used in Agterberg (2017) for fitting the bridge function separating the largest deposit size–frequency Pareto tail from the basic lognormal is significantly improved in this paper. A new method is presented for estimating the approximate deposit size value at which the upper tail Pareto comes into effect. Although a theoretical explanation of the proposed Pareto-lognormal distribution model is not a required condition for its applicability, it is shown that existing double Pareto-lognormal models based on Brownian motion generalizations of the multiplicative central limit theorem are not applicable to worldwide metal deposits. Neither are various upper tail frequency amplification models in their present form. Although a physicochemical explanation remains possible, it is argued that

  2. Impacts of Modification of Alloying Method on Inclusion Evolution in RH Refining of Silicon Steel

    Directory of Open Access Journals (Sweden)

    Fangjie Li

    2017-10-01

    Full Text Available This study explores the effect of introducing additional alloy elements not only in a different order but also at different stages of the Ruhrstahl-Heraeus (RH process of low-carbon silicon steel production. A more economical method, described as “pre-alloying”, has been introduced. The evolution of MnO-FeO inclusions produced by pre-alloying was investigated. Results show that spherical 3FeO·MnO inclusions form first, then shelled FeO·zMnO (z = 0.7–4 inclusions nucleate on the surface of pre-existing 3FeO·MnO. Spherical FeO·zMnO (z = 3–5 is further evolved from shelled 3FeO·MnO by diffusion. Because these MnO-FeO inclusions float up into the slag before degassing, the pre-alloying process does not affect the quality of the melt in the end. Both carbon content and inclusion size conform to industry standards.

  3. Impacts of Modification of Alloying Method on Inclusion Evolution in RH Refining of Silicon Steel.

    Science.gov (United States)

    Li, Fangjie; Li, Huigai; Zheng, Shaobo; You, Jinglin; Han, Ke; Zhai, Qijie

    2017-10-19

    This study explores the effect of introducing additional alloy elements not only in a different order but also at different stages of the Ruhrstahl-Heraeus (RH) process of low-carbon silicon steel production. A more economical method, described as "pre-alloying", has been introduced. The evolution of MnO-FeO inclusions produced by pre-alloying was investigated. Results show that spherical 3FeO·MnO inclusions form first, then shelled FeO·zMnO (z = 0.7-4) inclusions nucleate on the surface of pre-existing 3FeO·MnO. Spherical FeO·zMnO (z = 3-5) is further evolved from shelled 3FeO·MnO by diffusion. Because these MnO-FeO inclusions float up into the slag before degassing, the pre-alloying process does not affect the quality of the melt in the end. Both carbon content and inclusion size conform to industry standards.

  4. Spanish Refining

    International Nuclear Information System (INIS)

    Lores, F.R.

    2001-01-01

    An overview of petroleum refining in Spain is presented (by Repsol YPF) and some views on future trends are discussed. Spain depends heavily on imports. Sub-headings in the article cover: sources of crude imports, investments and logistics and marketing, -detailed data for each are shown diagrammatically. Tables show: (1) economic indicators (e.g. total GDP, vehicle numbers and inflation) for 1998-200; (2) crude oil imports for 1995-2000; (3) oil products balance for 1995-2000; (4) commodities demand, by product; (5) refining in Spain in terms of capacity per region; (6) outlets in Spain and other European countries in 2002 and (7) sales distribution channel by product

  5. Glycidyl fatty acid esters in refined edible oils: A review on formation, occurrence, analysis, and elimination methods

    Science.gov (United States)

    Glycidyl fatty acid esters (GEs), one of the main contaminants in processed oil, are mainly formed during the deodorization step in the oil refining process of edible oils and therefore occur in almost all refined edible oils. GEs are potential carcinogens, due to the fact that they hydrolyze into t...

  6. Refinement of a Method for Identifying Probable Archaeological Sites from Remotely Sensed Data

    Science.gov (United States)

    Tilton, James C.; Comer, Douglas C.; Priebe, Carey E.; Sussman, Daniel; Chen, Li

    2012-01-01

    To facilitate locating archaeological sites before they are compromised or destroyed, we are developing approaches for generating maps of probable archaeological sites, through detecting subtle anomalies in vegetative cover, soil chemistry, and soil moisture by analyzing remotely sensed data from multiple sources. We previously reported some success in this effort with a statistical analysis of slope, radar, and Ikonos data (including tasseled cap and NDVI transforms) with Student's t-test. We report here on new developments in our work, performing an analysis of 8-band multispectral Worldview-2 data. The Worldview-2 analysis begins by computing medians and median absolute deviations for the pixels in various annuli around each site of interest on the 28 band difference ratios. We then use principle components analysis followed by linear discriminant analysis to train a classifier which assigns a posterior probability that a location is an archaeological site. We tested the procedure using leave-one-out cross validation with a second leave-one-out step to choose parameters on a 9,859x23,000 subset of the WorldView-2 data over the western portion of Ft. Irwin, CA, USA. We used 100 known non-sites and trained one classifier for lithic sites (n=33) and one classifier for habitation sites (n=16). We then analyzed convex combinations of scores from the Archaeological Predictive Model (APM) and our scores. We found that that the combined scores had a higher area under the ROC curve than either individual method, indicating that including WorldView-2 data in analysis improved the predictive power of the provided APM.

  7. Creation and Delphi-method refinement of pediatric disaster triage simulations.

    Science.gov (United States)

    Cicero, Mark X; Brown, Linda; Overly, Frank; Yarzebski, Jorge; Meckler, Garth; Fuchs, Susan; Tomassoni, Anthony; Aghababian, Richard; Chung, Sarita; Garrett, Andrew; Fagbuyi, Daniel; Adelgais, Kathleen; Goldman, Ran; Parker, James; Auerbach, Marc; Riera, Antonio; Cone, David; Baum, Carl R

    2014-01-01

    There is a need for rigorously designed pediatric disaster triage (PDT) training simulations for paramedics. First, we sought to design three multiple patient incidents for EMS provider training simulations. Our second objective was to determine the appropriate interventions and triage level for each victim in each of the simulations and develop evaluation instruments for each simulation. The final objective was to ensure that each simulation and evaluation tool was free of bias toward any specific PDT strategy. We created mixed-methods disaster simulation scenarios with pediatric victims: a school shooting, a school bus crash, and a multiple-victim house fire. Standardized patients, high-fidelity manikins, and low-fidelity manikins were used to portray the victims. Each simulation had similar acuity of injuries and 10 victims. Examples include children with special health-care needs, gunshot wounds, and smoke inhalation. Checklist-based evaluation tools and behaviorally anchored global assessments of function were created for each simulation. Eight physicians and paramedics from areas with differing PDT strategies were recruited as Subject Matter Experts (SMEs) for a modified Delphi iterative critique of the simulations and evaluation tools. The modified Delphi was managed with an online survey tool. The SMEs provided an expected triage category for each patient. The target for modified Delphi consensus was ≥85%. Using Likert scales and free text, the SMEs assessed the validity of the simulations, including instances of bias toward a specific PDT strategy, clarity of learning objectives, and the correlation of the evaluation tools to the learning objectives and scenarios. After two rounds of the modified Delphi, consensus for expected triage level was >85% for 28 of 30 victims, with the remaining two achieving >85% consensus after three Delphi iterations. To achieve consensus, we amended 11 instances of bias toward a specific PDT strategy and corrected 10

  8. In situ X-ray Rietveld analysis of Ni-YSZ solid oxide fuel cell anodes during NiO reduction in H2

    International Nuclear Information System (INIS)

    Reyes Rojas, A; Esparza-Ponce, H E; Fuentes, L; Lopez-Ortiz, A; Keer, A; Reyes-Gasga, J

    2005-01-01

    A synthesis and characterization of solid oxide fuel cell (SOFC) anodes of nickel with 8%mol yttrium stabilized zirconia (Ni-YSZ) is presented. Attention was focused on the kinetics and phase composition associated with the transformation of NiO-YSZ to Ni-YSZ. The anodes were prepared with an alternative synthesis method that includes the use of nickel acetylacetonate as an inorganic precursor to obtain a highly porous material after sintering at 1400 deg. C and oxide reduction (NiO-YSZ → Ni-YSZ) at 800 deg. C for 8 h in a tubular reactor furnace using 10% H 2 /N 2 . The obtained material was compressed by unidirectional axial pressing into 1 cm-diameter discs with 15-66 wt% Ni and calcinated from room temperature to 800 deg. C. A heating rate of 1 deg. C min -1 showed the best results to avoid any anode cracking. Their structural and chemical characterization during the isothermal reduction were carried out by in situ time-resolved X-ray diffraction, refined with the Rietveld method (which allowed knowing the kinetic process of the reduction), scanning electron microscopy and X-ray energy dispersive spectroscopy. The results showed the formation of tetragonal YSZ 8%mol in the presence of nickel, a decrement in the unit cell volume of Ni and an increment of Ni in the Ni-YSZ anodes during the temperature reduction. The analysis indicated that the Johnson-Mehl-Avrami equation is unable to provide a good fit to the kinetics of the phase transformation. Instead, an alternative equation is presented

  9. Solution of free-boundary problems using finite-element/Newton methods and locally refined grids - Application to analysis of solidification microstructure

    Science.gov (United States)

    Tsiveriotis, K.; Brown, R. A.

    1993-01-01

    A new method is presented for the solution of free-boundary problems using Lagrangian finite element approximations defined on locally refined grids. The formulation allows for direct transition from coarse to fine grids without introducing non-conforming basis functions. The calculation of elemental stiffness matrices and residual vectors are unaffected by changes in the refinement level, which are accounted for in the loading of elemental data to the global stiffness matrix and residual vector. This technique for local mesh refinement is combined with recently developed mapping methods and Newton's method to form an efficient algorithm for the solution of free-boundary problems, as demonstrated here by sample calculations of cellular interfacial microstructure during directional solidification of a binary alloy.

  10. Refinement of Parallel and Reactive Programs

    OpenAIRE

    Back, R. J. R.

    1992-01-01

    We show how to apply the refinement calculus to stepwise refinement of parallel and reactive programs. We use action systems as our basic program model. Action systems are sequential programs which can be implemented in a parallel fashion. Hence refinement calculus methods, originally developed for sequential programs, carry over to the derivation of parallel programs. Refinement of reactive programs is handled by data refinement techniques originally developed for the sequential refinement c...

  11. Method for mercury refinement

    Science.gov (United States)

    Grossman, M.W.; Speer, R.; George, W.A.

    1991-04-09

    The effluent from mercury collected during the photochemical separation of the [sup 196]Hg isotope is often contaminated with particulate mercurous chloride, Hg[sub 2]Cl[sub 2]. The use of mechanical filtering via thin glass tubes, ultrasonic rinsing with acetone (dimethyl ketone) and a specially designed cold trap have been found effective in removing the particulate (i.e., solid) Hg[sub 2]Cl[sub 2] contaminant. The present invention is particularly directed to such filtering. 5 figures.

  12. Method for mercury refinement

    International Nuclear Information System (INIS)

    Grossman, M.W.; Speer, R.; George, W.A.

    1991-01-01

    The effluent from mercury collected during the photochemical separation of the 196 Hg isotope is often contaminated with particulate mercurous chloride, Hg 2 Cl 2 . The use of mechanical filtering via thin glass tubes, ultrasonic rinsing with acetone (dimethyl ketone) and a specially designed cold trap have been found effective in removing the particulate (i.e., solid) Hg 2 Cl 2 contaminant. The present invention is particularly directed to such filtering. 5 figures

  13. Haplotype analysis and a novel allele-sharing method refines a chromosome 4p locus linked to bipolar affective disorder.

    Science.gov (United States)

    Le Hellard, Stephanie; Lee, Andrew J; Underwood, Sarah; Thomson, Pippa A; Morris, Stewart W; Torrance, Helen S; Anderson, Susan M; Adams, Richard R; Navarro, Pau; Christoforou, Andrea; Houlihan, Lorna M; Detera-Wadleigh, Sevilla; Owen, Michael J; Asherson, Philip; Muir, Walter J; Blackwood, Douglas H R; Wray, Naomi R; Porteous, David J; Evans, Kathryn L

    2007-03-15

    Bipolar affective disorder (BPAD) and schizophrenia (SCZ) are common conditions. Their causes are unknown, but they include a substantial genetic component. Previously, we described significant linkage of BPAD to a chromosome 4p locus within a large pedigree (F22). Others subsequently have found evidence for linkage of BPAD and SCZ to this region. We constructed high-resolution haplotypes for four linked families, calculated logarithm of the odds (LOD) scores, and developed a novel method to assess the extent of allele sharing within genes between the families. We describe an increase in the F22 LOD score for this region. Definition and comparison of the linked haplotypes allowed us to prioritize two subregions of 3.8 and 4.4 Mb. Analysis of the extent of allele sharing within these subregions identified 200 kb that shows increased allele sharing between families. Linkage of BPAD to chromosome 4p has been strengthened. Haplotype analysis in the additional linked families refined the 20-Mb linkage region. Development of a novel allele-sharing method allowed us to bridge the gap between conventional linkage and association studies. Description of a 200-kb region of increased allele sharing prioritizes this region, which contains two functional candidate genes for BPAD, SLC2A9, and WDR1, for subsequent studies.

  14. A highly efficient sharp-interface immersed boundary method with adaptive mesh refinement for bio-inspired flow simulations

    Science.gov (United States)

    Deng, Xiaolong; Dong, Haibo

    2017-11-01

    Developing a high-fidelity, high-efficiency numerical method for bio-inspired flow problems with flow-structure interaction is important for understanding related physics and developing many bio-inspired technologies. To simulate a fast-swimming big fish with multiple finlets or fish schooling, we need fine grids and/or a big computational domain, which are big challenges for 3-D simulations. In current work, based on the 3-D finite-difference sharp-interface immersed boundary method for incompressible flows (Mittal et al., JCP 2008), we developed an octree-like Adaptive Mesh Refinement (AMR) technique to enhance the computational ability and increase the computational efficiency. The AMR is coupled with a multigrid acceleration technique and a MPI +OpenMP hybrid parallelization. In this work, different AMR layers are treated separately and the synchronization is performed in the buffer regions and iterations are performed for the convergence of solution. Each big region is calculated by a MPI process which then uses multiple OpenMP threads for further acceleration, so that the communication cost is reduced. With these acceleration techniques, various canonical and bio-inspired flow problems with complex boundaries can be simulated accurately and efficiently. This work is supported by the MURI Grant Number N00014-14-1-0533 and NSF Grant CBET-1605434.

  15. Adaptive mesh refinement for a finite volume method for flow and transport of radionuclides in heterogeneous porous media

    International Nuclear Information System (INIS)

    Amaziane, Brahim; Bourgeois, Marc; El Fatini, Mohamed

    2014-01-01

    In this paper, we consider adaptive numerical simulation of miscible displacement problems in porous media, which are modeled by single phase flow equations. A vertex-centred finite volume method is employed to discretize the coupled system: the Darcy flow equation and the diffusion-convection concentration equation. The convection term is approximated with a Godunov scheme over the dual finite volume mesh, whereas the diffusion-dispersion term is discretized by piecewise linear conforming finite elements. We introduce two kinds of indicators, both of them of residual type. The first one is related to time discretization and is local with respect to the time discretization: thus, at each time, it provides an appropriate information for the choice of the next time step. The second is related to space discretization and is local with respect to both the time and space variable and the idea is that at each time it is an efficient tool for mesh adaptivity. An error estimation procedure evaluates where additional refinement is needed and grid generation procedures dynamically create or remove fine-grid patches as resolution requirements change. The method was implemented in the software MELODIE, developed by the French Institute for Radiological Protection and Nuclear Safety (IRSN, Institut de Radioprotection et de Surete Nucleaire). The algorithm is then used to simulate the evolution of radionuclide migration from the waste packages through a heterogeneous disposal, demonstrating its capability to capture complex behavior of the resulting flow. (authors)

  16. Refined shape model fitting methods for detecting various types of phenological information on major U.S. crops

    Science.gov (United States)

    Sakamoto, Toshihiro

    2018-04-01

    Crop phenological information is a critical variable in evaluating the influence of environmental stress on the final crop yield in spatio-temporal dimensions. Although the MODIS (Moderate Resolution Imaging Spectroradiometer) Land Cover Dynamics product (MCD12Q2) is widely used in place of crop phenological information, the definitions of MCD12Q2-derived phenological events (e.g. green-up date, dormancy date) were not completely consistent with those of crop development stages used in statistical surveys (e.g. emerged date, harvested date). It has been necessary to devise an alternative method focused on detecting continental-scale crop developmental stages using a different approach. Therefore, this study aimed to refine the Shape Model Fitting (SMF) method to improve its applicability to multiple major U.S. crops. The newly-refined SMF methods could estimate the timing of 36 crop-development stages of major U.S. crops, including corn, soybeans, winter wheat, spring wheat, barley, sorghum, rice, and cotton. The newly-developed calibration process did not require any long-term field observation data, and could calibrate crop-specific phenological parameters, which were used as coefficients in estimated equation, by using only freely accessible public data. The calibration of phenological parameters was conducted in two steps. In the first step, the national common phenological parameters, referred to as X0[base], were calibrated by using the statistical data of 2008. The SMF method coupled using X0[base] was named the rSMF[base] method. The second step was a further calibration to gain regionally-adjusted phenological parameters for each state, referred to as X0[local], by using additional statistical data of 2015 and 2016. The rSMF method using the X0[local] was named the rSMF[local] method. This second calibration process improved the estimation accuracy for all tested crops. When applying the rSMF[base] method to the validation data set (2009-2014), the root

  17. Rietveld quantitative phase analysis of high surface area commercial alumina doped with niobia

    International Nuclear Information System (INIS)

    Gomes, L.B.; Pereira, A.S.; Pokorny, A.; Bergmann, C.P.

    2014-01-01

    The quantification of crystalline phases present in a given material can provide important information about the phenomena related to the diffusion of new elements in a ceramic matrix, as well as the formation and precipitation of minority phases and their microstructural evaluation. In this work, a high content of niobia (16 and 32 %w.t)was added to a high specific surface commercial alumina powder. The specimens were uniaxially pressed (200 MPa) and sintered in two stages: a first step at 1100°C for 3, 6 or 9 hours followed by a second step at 1350°C for 3 hours. The crystalline phases were analyzed by X-ray Diffraction (XRD) and quantified by the Rietveld method. The morphology of the samples was evaluated by Scanning Electron Microscopy (SEM). From the results obtained, some aluminum niobates phases expected for the Al_2O_3-Nb_2O_5 system could be identified as an intergranular phase and their relative fraction was quantified. (author)

  18. An efficient Adaptive Mesh Refinement (AMR) algorithm for the Discontinuous Galerkin method: Applications for the computation of compressible two-phase flows

    Science.gov (United States)

    Papoutsakis, Andreas; Sazhin, Sergei S.; Begg, Steven; Danaila, Ionut; Luddens, Francky

    2018-06-01

    We present an Adaptive Mesh Refinement (AMR) method suitable for hybrid unstructured meshes that allows for local refinement and de-refinement of the computational grid during the evolution of the flow. The adaptive implementation of the Discontinuous Galerkin (DG) method introduced in this work (ForestDG) is based on a topological representation of the computational mesh by a hierarchical structure consisting of oct- quad- and binary trees. Adaptive mesh refinement (h-refinement) enables us to increase the spatial resolution of the computational mesh in the vicinity of the points of interest such as interfaces, geometrical features, or flow discontinuities. The local increase in the expansion order (p-refinement) at areas of high strain rates or vorticity magnitude results in an increase of the order of accuracy in the region of shear layers and vortices. A graph of unitarian-trees, representing hexahedral, prismatic and tetrahedral elements is used for the representation of the initial domain. The ancestral elements of the mesh can be split into self-similar elements allowing each tree to grow branches to an arbitrary level of refinement. The connectivity of the elements, their genealogy and their partitioning are described by linked lists of pointers. An explicit calculation of these relations, presented in this paper, facilitates the on-the-fly splitting, merging and repartitioning of the computational mesh by rearranging the links of each node of the tree with a minimal computational overhead. The modal basis used in the DG implementation facilitates the mapping of the fluxes across the non conformal faces. The AMR methodology is presented and assessed using a series of inviscid and viscous test cases. Also, the AMR methodology is used for the modelling of the interaction between droplets and the carrier phase in a two-phase flow. This approach is applied to the analysis of a spray injected into a chamber of quiescent air, using the Eulerian

  19. Computational methods and modeling. 3. Adaptive Mesh Refinement for the Nodal Integral Method and Application to the Convection-Diffusion Equation

    International Nuclear Information System (INIS)

    Torej, Allen J.; Rizwan-Uddin

    2001-01-01

    The nodal integral method (NIM) has been developed for several problems, including the Navier-Stokes equations, the convection-diffusion equation, and the multigroup neutron diffusion equations. The coarse-mesh efficiency of the NIM is not fully realized in problems characterized by a wide range of spatial scales. However, the combination of adaptive mesh refinement (AMR) capability with the NIM can recover the coarse mesh efficiency by allowing high degrees of resolution in specific localized areas where it is needed and by using a lower resolution everywhere else. Furthermore, certain features of the NIM can be fruitfully exploited in the application of the AMR process. In this paper, we outline a general approach to couple nodal schemes with AMR and then apply it to the convection-diffusion (energy) equation. The development of the NIM with AMR capability (NIMAMR) is based on the well-known Berger-Oliger method for structured AMR. In general, the main components of all AMR schemes are 1. the solver; 2. the level-grid hierarchy; 3. the selection algorithm; 4. the communication procedures; 5. the governing algorithm. The first component, the solver, consists of the numerical scheme for the governing partial differential equations and the algorithm used to solve the resulting system of discrete algebraic equations. In the case of the NIM-AMR, the solver is the iterative approach to the solution of the set of discrete equations obtained by applying the NIM. Furthermore, in the NIM-AMR, the level-grid hierarchy (the second component) is based on the Hierarchical Adaptive Mesh Refinement (HAMR) system,6 and hence, the details of the hierarchy are omitted here. In the selection algorithm, regions of the domain that require mesh refinement are identified. The criterion to select regions for mesh refinement can be based on the magnitude of the gradient or on the Richardson truncation error estimate. Although an excellent choice for the selection criterion, the Richardson

  20. Rietveld refinement of the mixed boracite Fe1.59Zn1.41B7O13Br

    Directory of Open Access Journals (Sweden)

    Sandra Ulloa-Godínez

    2009-11-01

    Full Text Available The structural characterization of the new iron–zinc heptaborate bromide with composition Fe1.59Zn1.41B7O13Br, prepared by chemical transport is reported. A rigid-body model with constrained generalized coordinates was defined in order to hold the positions of the B atoms at reasonable interatomic distances that typically would reach unacceptable values because of the weak scattering power of boron. There are three independent sites for the B atoms of which two are tetrahedrally coordinated. The bond-valence sum around the third B atom, located on a threefold rotation axis, was calculated considering two cases of coordination of boron with oxygens: trigonal-planar and tetrahedral. The contribution of the fourth O atom to the bond-valence sum was found to be only 0.06 v.u., indicating the presence of a very weak bond in the right position to have a distorted tetrahedral coordination in favour of the trigonal-planar coordination for the third B atom. X-ray fluorescence (XRF was used to determinate the Fe/Zn ratio.

  1. Rietveld refinement of the mixed boracite Fe(1.59)Zn(1.41)B(7)O(13)Br.

    Science.gov (United States)

    Ulloa-Godínez, Sandra; Rosales, Ivonne; Bucio, Lauro; Farías, Mario H; Campa-Molina, Jorge

    2009-10-31

    The structural characterization of the new iron-zinc hepta-borate bromide with composition Fe(1.59)Zn(1.41)B(7)O(13)Br, prepared by chemical transport is reported. A rigid-body model with constrained generalized coordinates was defined in order to hold the positions of the B atoms at reasonable inter-atomic distances that typically would reach unacceptable values because of the weak scattering power of boron. There are three independent sites for the B atoms of which two are tetra-hedrally coordinated. The bond-valence sum around the third B atom, located on a threefold rotation axis, was calculated considering two cases of coordination of boron with oxygens: trigonal-planar and tetrahedral. The contribution of the fourth O atom to the bond-valence sum was found to be only 0.06 v.u., indicating the presence of a very weak bond in the right position to have a distorted tetra-hedral coordination in favour of the trigonal-planar coordination for the third B atom. X-ray fluorescence (XRF) was used to determinate the Fe/Zn ratio.

  2. Refining Nodes and Edges of State Machines

    DEFF Research Database (Denmark)

    Hallerstede, Stefan; Snook, Colin

    2011-01-01

    State machines are hierarchical automata that are widely used to structure complex behavioural specifications. We develop two notions of refinement of state machines, node refinement and edge refinement. We compare the two notions by means of examples and argue that, by adopting simple conventions...... refinement theory and UML-B state machine refinement influences the style of node refinement. Hence we propose a method with direct proof of state machine refinement avoiding the detour via Event-B that is needed by UML-B....

  3. A mass-conserving lattice Boltzmann method with dynamic grid refinement for immiscible two-phase flows

    International Nuclear Information System (INIS)

    Fakhari, Abbas; Geier, Martin; Lee, Taehun

    2016-01-01

    A mass-conserving lattice Boltzmann method (LBM) for multiphase flows is presented in this paper. The proposed LBM improves a previous model (Lee and Liu, 2010 [21]) in terms of mass conservation, speed-up, and efficiency, and also extends its capabilities for implementation on non-uniform grids. The presented model consists of a phase-field lattice Boltzmann equation (LBE) for tracking the interface between different fluids and a pressure-evolution LBM for recovering the hydrodynamic properties. In addition to the mass conservation property and the simplicity of the algorithm, the advantages of the current phase-field LBE are that it is an order of magnitude faster than the previous interface tracking LBE proposed by Lee and Liu (2010) [21] and it requires less memory resources for data storage. Meanwhile, the pressure-evolution LBM is equipped with a multi-relaxation-time (MRT) collision operator to facilitate attainability of small relaxation rates thereby allowing simulation of multiphase flows at higher Reynolds numbers. Additionally, we reformulate the presented MRT-LBM on nonuniform grids within an adaptive mesh refinement (AMR) framework. Various benchmark studies such as a rising bubble and a falling drop under buoyancy, droplet splashing on a wet surface, and droplet coalescence onto a fluid interface are conducted to examine the accuracy and versatility of the proposed AMR-LBM. The proposed model is further validated by comparing the results with other LB models on uniform grids. A factor of about 20 in savings of computational resources is achieved by using the proposed AMR-LBM. As a more demanding application, the Kelvin–Helmholtz instability (KHI) of a shear-layer flow is investigated for both density-matched and density-stratified binary fluids. The KHI results of the density-matched fluids are shown to be in good agreement with the benchmark AMR results based on the sharp-interface approach. When a density contrast between the two fluids exists, a

  4. A mass-conserving lattice Boltzmann method with dynamic grid refinement for immiscible two-phase flows

    Energy Technology Data Exchange (ETDEWEB)

    Fakhari, Abbas, E-mail: afakhari@nd.edu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Geier, Martin [TU Braunschweig, Institute for Computational Modeling in Civil Engineering (iRMB), TU-Braunschweig, Pockelsstr. 3, 38106 Braunschweig (Germany); Lee, Taehun [Department of Mechanical Engineering, The City College of the City University of New York, New York, NY 10031 (United States)

    2016-06-15

    A mass-conserving lattice Boltzmann method (LBM) for multiphase flows is presented in this paper. The proposed LBM improves a previous model (Lee and Liu, 2010 [21]) in terms of mass conservation, speed-up, and efficiency, and also extends its capabilities for implementation on non-uniform grids. The presented model consists of a phase-field lattice Boltzmann equation (LBE) for tracking the interface between different fluids and a pressure-evolution LBM for recovering the hydrodynamic properties. In addition to the mass conservation property and the simplicity of the algorithm, the advantages of the current phase-field LBE are that it is an order of magnitude faster than the previous interface tracking LBE proposed by Lee and Liu (2010) [21] and it requires less memory resources for data storage. Meanwhile, the pressure-evolution LBM is equipped with a multi-relaxation-time (MRT) collision operator to facilitate attainability of small relaxation rates thereby allowing simulation of multiphase flows at higher Reynolds numbers. Additionally, we reformulate the presented MRT-LBM on nonuniform grids within an adaptive mesh refinement (AMR) framework. Various benchmark studies such as a rising bubble and a falling drop under buoyancy, droplet splashing on a wet surface, and droplet coalescence onto a fluid interface are conducted to examine the accuracy and versatility of the proposed AMR-LBM. The proposed model is further validated by comparing the results with other LB models on uniform grids. A factor of about 20 in savings of computational resources is achieved by using the proposed AMR-LBM. As a more demanding application, the Kelvin–Helmholtz instability (KHI) of a shear-layer flow is investigated for both density-matched and density-stratified binary fluids. The KHI results of the density-matched fluids are shown to be in good agreement with the benchmark AMR results based on the sharp-interface approach. When a density contrast between the two fluids exists, a

  5. Rietveld profile analysis of calcined AlPO/sub 4/-11 using pulsed neutron powder diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, J.W. Jr.; Pluth, J.J.; Smith, J.V.

    1988-08-01

    Aluminium phosphate, AlPO/sub 4/, M/sub r/=121.95, orthorhombic, Icmm (disordered Al, P), Icm2 (ordered Al, P), a=13.5333(8), b=18.4845(10), c=8.3703(4) A, V=2094 A/sup 3/, Z=20, D/sub x/=1.93 g cm/sup -3/, T approx. = 295 K, R/sub wp/=0.031, R/sub F//sup 2/=0.109 (Icmm) and R/sub wp/=0.027, R/sub F//sup 2/=0.058 (Icm2) for 1017 independent reflections. Sample calcined at 873 K and dehydrated at 573 K. Time-of-flight neutron powder diffraction data were taken on the GPPD diffractometer at the Argonne National Laboratory Intense Pulsed Neutron Source. The structure was refined by Rietveld profile analysis in the range d=0.86-3.91 A in two space groups: Icmm assuming no ordering of Al and P, and Icm2 assuming strict alternation of Al and P on tetrahedral nodes. (orig./BHo).

  6. Preparation and Crystal Structures of Some AIVB2IIO4 Compounds: Powder X-Ray Diffraction and Rietveld Analysis

    Directory of Open Access Journals (Sweden)

    K. Jeyadheepan

    2014-01-01

    Full Text Available The AIVB2IIO4 compounds such as cadmium tin oxide (Cd2SnO4 or CTO and zinc tin oxide (Zn2SnO4 or ZTO are synthesized by solid state reaction of the subsequent binary oxides. The synthesized powders were analyzed through the powder X-ray diffraction (PXRD. Cell search done on the PXRD patterns shows that the Cd2SnO4 crystallizes in orthorhombic structure with space group Pbam and the cell parameters as a=5.568(2 Å, b=9.894(3 Å, and c=3.193(1 Å and the Zn2SnO4 crystallizes as cubic with the space group Fd3 -m and with the cell parameter a=8.660(2 Å. Rietveld refinement was done on the PXRD patterns to get the crystal structure of the Cd2SnO4 and Zn2SnO4 and to define the site deficiency of atoms which causes the electrical properties of the materials.

  7. Animal welfare and the refinement of neuroscience research methods--a case study of Huntington's disease models.

    Science.gov (United States)

    Olsson, I Anna S; Hansen, Axel K; Sandøe, Peter

    2008-07-01

    The use of animals in biomedical and other research presents an ethical dilemma: we do not want to lose scientific benefits, nor do we want to cause laboratory animals to suffer. Scientists often refer to the potential human benefits of animal models to justify their use. However, even if this is accepted, it still needs to be argued that the same benefits could not have been achieved with a mitigated impact on animal welfare. Reducing the adverse effects of scientific protocols ('refinement') is therefore crucial in animal-based research. It is especially important that researchers share knowledge on how to avoid causing unnecessary suffering. We have previously demonstrated that even in studies in which animal use leads to spontaneous death, scientists often fail to report measures to minimize animal distress (Olsson et al. 2007). In this paper, we present the full results of a case study examining reports, published in peer-reviewed journals between 2003 and 2004, of experiments employing animal models to study the neurodegenerative disorder Huntington's disease. In 51 references, experiments in which animals were expected to develop motor deficits so severe that they would have difficulty eating and drinking normally were conducted, yet only three references were made to housing adaptation to facilitate food and water intake. Experiments including end-stages of the disease were reported in 14 papers, yet of these only six referred to the euthanasia of moribund animals. If the reference in scientific publications reflects the actual application of refinement, researchers do not follow the 3Rs (replacement, reduction, refinement) principle. While in some cases, it is clear that less-than-optimal techniques were used, we recognize that scientists may apply refinement without referring to it; however, if they do not include such information in publications, it suggests they find it less relevant. Journal publishing policy could play an important role: first, in

  8. EL APARADOR DE RIETVELD DEL MUSEO NACIONAL DE ARTES DECORATIVAS (MADRID.

    Directory of Open Access Journals (Sweden)

    María Villalba Salvador

    2012-01-01

    Full Text Available Este artículo trata de hacer una aproximación al estudio de una de las piezas más relevantes de la historia del diseño de mobiliario de vanguardia: el aparador de Rietveld, también conocido como Buffet Elling. Su diseño data de 1919, y responde a la estética propia del autor en aquellos años posteriores a la Primera Guerra Mundial, cuyas piezas son coincidentes con los planteamientos artísticos del grupo De Stijl. Es representativo de los principios básicos de la obra de Rietveld, uno de los pioneros del funcionalismo junto con J.J.P. Oud, en cuanto a la opción por el diseño y la arquitectura, y por la producción en masa y el diseño industrial accesible al conjunto de la sociedad. Merece destacar la colaboración de Gerard A. Van de Groenekan, asistente de Rietveld a lo largo de toda su trayectoria artística. Esta pieza nos ayuda a estudiar el pensamiento de Gerrit Th. Rietvel en relación con el diseño de vanguardia.This article tries to be an approach to the study of one of the most relevant pieces of furniture in the history of the design of avant-garde furniture: Rietveld´s dresser, also known as Elling Buffet. It was designed in 1919, and it shows the author´s aesthetics in the years that followed World War I, with pieces that are much related to the artistic orientation of the group De Stijl. It clearly shows the main characteristics of Rietveld´s work, one of the pioneers of functionalism, together with J.J.P. Oud, regarding design and architecture, mass production and industrial design accessible to society as a whole. It is worth mentioning the collaboration of Gerard A. Van de Groenekan, Rietveld´s assistant throughout his artistic trajectory. This piece of furniture helps us study Rietveld´s thinking regarding avant-garde design.

  9. An efficient and target-oriented sample enrichment method for preparative separation of minor alkaloids by pH-zone-refining counter-current chromatography.

    Science.gov (United States)

    Feng, Rui-Hong; Hou, Jin-Jun; Zhang, Yi-Bei; Pan, Hui-Qin; Yang, Wenzhi; Qi, Peng; Yao, Shuai; Cai, Lu-Ying; Yang, Min; Jiang, Bao-Hong; Liu, Xuan; Wu, Wan-Ying; Guo, De-An

    2015-08-28

    An efficient and target-oriented sample enrichment method was established to increase the content of the minor alkaloids in crude extract by using the corresponding two-phase solvent system applied in pH-zone-refining counter-current chromatography. The enrichment and separation of seven minor indole alkaloids from Uncaria rhynchophylla (Miq.) Miq. ex Havil(UR) were selected as an example to show the advantage of this method. An optimized two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (3:7:1:9, v/v) was used in this study, where triethylamine (TEA) as the retainer and hydrochloric acid (HCl) as the eluter were added at the equimolar of 10mM. Crude alkaloids of UR dissolved in the corresponding upper phase (containing 10mM TEA) were extracted twice with lower phase (containing 10mM TEA) and lower phase (containing 10mM HCl), respectively, the second lower phase extract was subjected to pH-zone-refining CCC separation after alkalization and desalination. Finally, from 10g of crude alkaloids, 4g of refined alkaloids was obtained and the total content of seven target indole alkaloids was increased from 4.64% to 15.78%. Seven indole alkaloids, including 54mg isocorynoxeine, 21mg corynoxeine, 46mg isorhynchophylline, 35mg rhynchophylline, 65mg hirsutine, 51mg hirsuteine and 27mg geissoschizine methylether were all simultaneously separated from 2.5g of refined alkaloids, with the purity of 86.4%, 97.5%, 90.3%, 92.1%, 98.5%, 92.3%, and 92.8%, respectively. The total content and purities of the seven minor indole alkaloids were tested by HPLC and their chemical structures were elucidated by ESI-HRMS and (1)H NMR. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Proposal of method for quantifying uranium weight in the interior of gas centrifuge, and performance evaluation of IF7 treatment reaction product separation and refinement

    International Nuclear Information System (INIS)

    Ema, Akira; Kado, Kazumi; Suzuki, Kazuhiko

    2011-01-01

    In uranium enrichment plant decommissioning, it is important to treat and dispose the gas centrifuge reasonably. At the Ningyo-Toge Environmental Engineering Center of JAEA, it has been planned to carry out IF 7 treatment for the gas centrifuge in the uranium enrichment plant for decontamination before dismantling. In order to carry out this IF 7 treatment, a nondestructive measurement technology to estimate the uranium weight in the interior of the gas centrifuge was needed. However, it was difficult to estimate exactly uranium weight using former methods. Therefore, in this study, we investigated a new nondestructive measurement. As a result, we succeeded in constructing theoretically the methodology using γ-ray intensity measured outside the gas centrifuge and MCNP code. Furthermore, the UF 6 and IF 5 mixture was recovered by IF 7 treatment. A technology to separate and refine IF 5 from this mixture was needed in order to use as a material of IF 7 gas. Therefore, in this study, we carried out IF 5 separation and refinement examination. This paper shows the investigation result of reasonable separation condition and the full-scale examination result. As a result, it could be proved that 86% of IF 5 was separated and refined from UF 6 and IF 5 mixture. (author)

  11. The combination of activated natural zeolite-bentonite to reduce Fe and Cu in refined bleached palm oil (RBPO) by using atomic absorption spectrophotometer method

    Science.gov (United States)

    Zakwan; Raja, PM; Giyanto

    2018-02-01

    Indonesia is one of the crude palm oil (CPO) production country in the world. As many products are derivated from the CPO, the quality must be increased continuously. One of the things that influence the quality of palm oil is the Fe and Cu content. The objective of this research was to reduce Fe and Cu content in Refined Bleached Palm Oil (RBPO). In processing CPO or Refined Bleachead Palm Oil (RBPO) may be contaminated by Fe and Cu from metal tank and pipe in the factory. The zeolite and bentonite was activated by maceration method using hydrochloric acid (0,1 N). Four batch reactions consisting of refined palm oil (RPO), activated natural zeolite-bentonite (ANZB) was bleached by heating and stirring them at about 105°C and 1200 rpm for 30 minutes. The results showed that all combinations of ANZB can reduce the Fe content. Thereafter, the optimal combination of ANZB was obtained in K1, K2 and K4 with Cu content 0.02 ppm. In the future, it is needed to study on the reduction of the Fe and Cu content in palm oil with the other adsorbent.

  12. Structure of 3 at.% and 9 at.% Si-doped HfO{sub 2} from combined refinement of X-ray and neutron diffraction patterns

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lili [Department of Materials Science and Engineering, North Carolina State University, NC 27695 (United States); School of Information Science and Technology, Northwest University, Xi' an 710127 (China); Hou, Dong; Usher, Tedi-Marie; Iamsasri, Thanakorn; Fancher, Chris M.; Forrester, Jennifer S. [Department of Materials Science and Engineering, North Carolina State University, NC 27695 (United States); Nishida, Toshikazu [Department of Electrical and Computer Engineering, University of Florida, FL 32611 (United States); Moghaddam, Saeed [Department of Mechanical and Aerospace Engineering, University of Florida, FL 32611 (United States); Jones, Jacob L., E-mail: jacobjones@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, NC 27695 (United States)

    2015-10-15

    The crystal structure of 3 at.% and 9 at.% Si-doped HfO{sub 2} powder was determined through refinements using X-ray and neutron diffraction patterns. The lattice parameters, atomic positions, dopant occupancy, and the second phase fraction were determined with high precision using a combined full pattern fitting via the Rietveld method. The results show that both 3 at.% and 9 at.% Si-doped HfO{sub 2} powder exhibit the monoclinic crystal structure with P 1 2{sub 1}/c 1 space group. Through the combined refinement, the crystal structure parameters, especially for the positions and occupancies of the lighter atoms, were more precisely determined compared to independent X-ray diffraction refinement. Although the ionic radius of Si{sup 4+} is smaller than Hf{sup 4+}, with increasing Si occupancy, the unit cell volume slightly increases; possible mechanisms for this effect are discussed. Moreover, the refined results provide evidence of the existence of a non-equilibrium phase of Hf{sub x}Si{sub 1−x}O{sub 2}. The second phase (SiO{sub 2}) fraction is determined as 0.17 at.% for 3 at.% Si-doped HfO{sub 2} powders and 1.7 at.% for 9 at.% Si-doped HfO{sub 2} powders. - Highlights: • X-ray and neutron diffraction patterns were used to determine crystal structure. • Results from independent refinements and a combined refinement were compared. • Highly precise structural parameters were obtained by the combined refinement. • Structural data of 3 at.% and 9 at.% Si-doped HfO{sub 2} are provided. • The unit cell volume slightly increases with Si concentration from 3 to 9 at.%.

  13. Micro-structural study and Rietveld analysis of fast reactor fuels: U–Mo fuels

    International Nuclear Information System (INIS)

    Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K.B.; Kumar, Arun

    2015-01-01

    U–Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U–Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U–Mo alloys as fast reactor fuel. - Highlights: • U–Mo alloys in as-cast as well as in annealed conditions have been studied using Optical Microscope, SEM, XRD. • The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. • The dendritic microstructure of γ-(U,Mo) and B.C.C. ‘Mo’ phase of 33 at.% U–Mo alloy have been analysed. • Rietveld analysis has been done to optimize lattice parameters and calculate phase fractions in annealed alloys. • The Vickers microhardness of U_2Mo phase shows lower hardness than two phase microstructures in annealed alloys.

  14. Micro-structural study and Rietveld analysis of fast reactor fuels: U–Mo fuels

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, S., E-mail: sibasis@barc.gov.in [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Choudhuri, G. [Atomic Fuels Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Banerjee, J. [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Agarwal, Renu [Product Development Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Khan, K.B.; Kumar, Arun [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India)

    2015-12-15

    U–Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U–Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U–Mo alloys as fast reactor fuel. - Highlights: • U–Mo alloys in as-cast as well as in annealed conditions have been studied using Optical Microscope, SEM, XRD. • The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. • The dendritic microstructure of γ-(U,Mo) and B.C.C. ‘Mo’ phase of 33 at.% U–Mo alloy have been analysed. • Rietveld analysis has been done to optimize lattice parameters and calculate phase fractions in annealed alloys. • The Vickers microhardness of U{sub 2}Mo phase shows lower hardness than two phase microstructures in annealed alloys.

  15. Dos artículos de Rietveld Comprensión. Nuevo Funcionalismo en la Arquitectura

    Directory of Open Access Journals (Sweden)

    Editor Cuaderno de Notas

    1995-12-01

    Full Text Available Los siguientes dos artículos de Rietveld (1888-1964 fueron publicados por primera vez en la revista i10 en 1928 y en De Vrije Bladen en 1932 respectivamente. Esta es su primera traducción al castellano, para lo que se ha partido de sus correspondientes traducciones inglesas; "Inzicht" (comprensión, en el libro de Theodore M.. Brown, The Work of G. Rietveld architect, Utrecht 1958, y "Nieuwe zakelijkheid in de Nederlandsche architectuur" (Nueva objetividad en la arquitectura holandesa, en la monografía-catálogo, Gerrit Rietveld 1888-1964. The complet works, Central Museum, Utrecht, 1992. En cuanto al último, de bastante mayor extensión, contaba originariamente con ilustraciones de obras de JA.Brinkman y L.C. van der Vlugt, A. Bodón, J. Duiker, J.J.P. Oud y Le Corbusier como único arquitecto extranjero representado, aparte de las de sus propio trabajo.

  16. A refined method for assessing sup(99m)Tc-MDP whole body retention in prostate cancer patients

    International Nuclear Information System (INIS)

    Castronovo, F.P. Jr.; Strauss, H.W.; McKusick, K.A.

    1987-01-01

    Whole body retention (WBR) of sup(99m)Tc labeled methylene diphosphonate (MDP) significantly differentiates various clinical stages of prostate cancer. Whole body measurements, when performed at 5 min and 24 h after i.v. administration of sup(99m)Tc-MDP, allows for the calculations of percentage whole body retention (% WBR) after one day. In an attempt to better describe the clinical course of prostate cancer patients with bone metastases we have refined the % WBR calculations to include a normalization factor. The latter consists of the mean 24-h value of WBR's as obtained from 10 prostate cancer patients without bony metastases as determined by bone scintigram. The % WBR is then divided by the normalization factor of choice and expressed as (% WRN)sup(N). These data are used to better express sup(99m)Tc MDP 24-h whole body retentions when following the clinical course of patients with metastatic carcinoma of the prostate. Caution should be exercised when interpreting these data when metabolic bone pathology is present. A false negative (% WBR)sup(N) value will result if an infiltration of the sup(99m)Tc-MDP occurs during administration. (author)

  17. A cellular automaton - finite volume method for the simulation of dendritic and eutectic growth in binary alloys using an adaptive mesh refinement

    Science.gov (United States)

    Dobravec, Tadej; Mavrič, Boštjan; Šarler, Božidar

    2017-11-01

    A two-dimensional model to simulate the dendritic and eutectic growth in binary alloys is developed. A cellular automaton method is adopted to track the movement of the solid-liquid interface. The diffusion equation is solved in the solid and liquid phases by using an explicit finite volume method. The computational domain is divided into square cells that can be hierarchically refined or coarsened using an adaptive mesh based on the quadtree algorithm. Such a mesh refines the regions of the domain near the solid-liquid interface, where the highest concentration gradients are observed. In the regions where the lowest concentration gradients are observed the cells are coarsened. The originality of the work is in the novel, adaptive approach to the efficient and accurate solution of the posed multiscale problem. The model is verified and assessed by comparison with the analytical results of the Lipton-Glicksman-Kurz model for the steady growth of a dendrite tip and the Jackson-Hunt model for regular eutectic growth. Several examples of typical microstructures are simulated and the features of the method as well as further developments are discussed.

  18. Structural refinement, photoluminescence and Raman spectroscopy of wurtzite Mn-doped Zn O pellets

    Energy Technology Data Exchange (ETDEWEB)

    Marquina, J.; Martin, J.; Luengo, J.; Vera, F.; Roa, L. [Centro de Estudios Avanzados en Optica, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Gonzalez, J. [Centro de Estudios de Semiconductores, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Rodriguez, F.; Renero L, C.; Valiente, R. [Malta-Consolider Team, CITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander 69005 (Spain); Delgado, G. E., E-mail: marquinajesus@gmail.com [Laboratorio de Cristalografia, Facultad de Ciencias, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of)

    2017-11-01

    We report the results of the Rietveld refinement, photoluminescence and Raman spectroscopy of Mn-doped Zn O ceramic pellets. Rietveld refinement shows that samples crystallize in the wurtzite structure and for the Mn-doped sample indicated that the Mn atoms substitute the Zn tetrahedral crystallographic sites in the Zn O host lattice. The emission and absorption spectra of Mn-doped Zn O have been investigated in the visible-UV region and the data have been interpreted in terms of the wurtzite Zn O electronic structure. Two broad bands, one due to superposition between donor bound excitons (DX) and free excitons (FX) and other due free-to bond excitonic recombination (FB) dominates the low-temperature photoluminescence spectra of Mn-doped Zn O bulk. In the Raman spectrum, an extra mode at ∼520 cm{sup -1} has been observed in agreement with earlier works, and it is an indicator for the incorporation of Mn{sup +2} ions into the Zn O host matrix since it is not is observed in Zn O pristine. Rietveld refinement of the X-ray diffraction patterns, energy-dispersive X-ray spectroscopy (EDS) technique, and Raman spectroscopies were performed to study these effects. (Author)

  19. Hirshfeld atom refinement.

    Science.gov (United States)

    Capelli, Silvia C; Bürgi, Hans-Beat; Dittrich, Birger; Grabowsky, Simon; Jayatilaka, Dylan

    2014-09-01

    Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly-l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree-Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs) are freely refined without constraints or restraints - even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu's), all other structural parameters agree within less than 2 csu's. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules), the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å(2) as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements - an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å.

  20. On the refinement calculus

    CERN Document Server

    Vickers, Trevor

    1992-01-01

    On the Refinement Calculus gives one view of the development of the refinement calculus and its attempt to bring together - among other things - Z specifications and Dijkstra's programming language. It is an excellent source of reference material for all those seeking the background and mathematical underpinnings of the refinement calculus.

  1. 77 FR 2064 - Availability of the Report on the International Workshop on Alternative Methods To Reduce, Refine...

    Science.gov (United States)

    2012-01-13

    ... Validation of Alternative Methods, and Health Canada. The workshop was co-sponsored by the Society of... Coordinating Committee on the Validation of Alternative Methods (ICCVAM), an interagency committee of the... prioritize research, development, and validation efforts needed to address these knowledge and data gaps in...

  2. Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

    Energy Technology Data Exchange (ETDEWEB)

    Alves, J.L.; Zanini, A.E.; Souza, M.E. de; Nascimento, M.L.F., E-mail: jeff_eq@yahoo.com.br, E-mail: mlfn@ufba.br [Universidade Federal da Bahia (UFBA/PROTEC/PEI), Salvador, BA (Brazil). Departamento de Engenharia Quimica

    2016-01-15

    Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitoria da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale. (author)

  3. Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

    Directory of Open Access Journals (Sweden)

    J. L. Alves

    2016-03-01

    Full Text Available Abstract Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitória da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8 μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale.

  4. Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

    International Nuclear Information System (INIS)

    Alves, J.L.; Zanini, A.E.; Souza, M.E. de; Nascimento, M.L.F.

    2016-01-01

    Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitoria da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale. (author)

  5. Implementation of the 3Rs (refinement, reduction, and replacement): validation and regulatory acceptance considerations for alternative toxicological test methods.

    Science.gov (United States)

    Schechtman, Leonard M

    2002-01-01

    Toxicological testing in the current regulatory environment is steeped in a history of using animals to answer questions about the safety of products to which humans are exposed. That history forms the basis for the testing strategies that have evolved to satisfy the needs of the regulatory bodies that render decisions that affect, for the most part, virtually all phases of premarket product development and evaluation and, to a lesser extent, postmarketing surveillance. Only relatively recently have the levels of awareness of, and responsiveness to, animal welfare issues reached current proportions. That paradigm shift, although sluggish, has nevertheless been progressive. New and alternative toxicological methods for hazard evaluation and risk assessment have now been adopted and are being viewed as a means to address those issues in a manner that considers humane treatment of animals yet maintains scientific credibility and preserves the goal of ensuring human safety. To facilitate this transition, regulatory agencies and regulated industry must work together toward improved approaches. They will need assurance that the methods will be reliable and the results comparable with, or better than, those derived from the current classical methods. That confidence will be a function of the scientific validation and resultant acceptance of any given method. In the United States, to fulfill this need, the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and its operational center, the National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM), have been constituted as prescribed in federal law. Under this mandate, ICCVAM has developed a process and established criteria for the scientific validation and regulatory acceptance of new and alternative methods. The role of ICCVAM in the validation and acceptance process and the criteria instituted toward that end are described. Also

  6. Development and refinement of new statistical methods for enhanced syndromic surveillance during the 2012 Olympic and Paralympic Games.

    Science.gov (United States)

    Morbey, Roger A; Elliot, Alex J; Charlett, Andre; Andrews, Nick; Verlander, Neville Q; Ibbotson, Sue; Smith, Gillian E

    2015-06-01

    Prior to the 2012 London Olympic and Paralympic Games, new statistical methods had to be developed for the enhanced syndromic surveillance during the Games. Different methods were developed depending on whether or not historical data were available. Practical solutions were needed to cope with the required daily reporting and data quality issues. During the Games, nearly 4800 signals were tested on average each day, generating statistical alarms that were assessed to provide information on areas of potential public health concern and reassurance that no major adverse incident had occurred. spjhi;21/2/159/FIG41460458213517577 F1 fig4-1460458213517577. © The Author(s) 2013.

  7. Nano sized La2Co2O6 double perovskite synthesized by sol gel method

    Science.gov (United States)

    Solanki, Neha; Lodhi, Pavitra Devi; Choudhary, K. K.; Kaurav, Netram

    2018-05-01

    We report here the synthesis of double perovskite La2Co2O6 (LCO) compound by a sol gel route method. The double perovskite structure of LCO system was confirmed via X-ray diffraction (XRD) analysis. Further, the lattice parameter, unit cell volume and bond length were refined by means of rietveld analysis using the full proof software. Debye Scherer formula was used to determine the particle size. The compound crystallized in triclinic structure with space group P-1 in ambient condition. We also obtained Raman modes from XRD spectra of poly-crystalline LCO sample. These results were interpreted for the observation of phonon excitations in this compound.

  8. Micro-structural study and Rietveld analysis of fast reactor fuels: U-Mo fuels

    Science.gov (United States)

    Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K. B.; Kumar, Arun

    2015-12-01

    U-Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U-Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U-Mo alloys as fast reactor fuel.

  9. Structure of the new Tl(Ba sub 1.0 Sr sub 1.0) PrCu sub 2 O sub 7-x by Rietveld analysis

    International Nuclear Information System (INIS)

    Yang, P.; Fun, H. K.; Lee, T.J.; Ku, H.C.; Lai, C.C.

    1994-01-01

    The crystalline structure of Tl(Ba sub 1.0 Sr sub 1.0)PrCu sub 2 O sub 7-x was obtained at room temperature from x-ray powder diffraction with CuK sub α radiation using Rietveld analysis. Tl(Ba sub 1.0 Sr sub 1.0)PrCu sub 2 O sub 7-x isomorphous at both room temperature (300 K) and low temperature (100 K) with TlBa sub 2 ca Cu sub 2 O sub 7-x type (1212) structure, crystallized with space group P4/mmm and one formula in the unit cell. At 300 K, cell parameters a=3.8892(2) A, c=12.3099(6) A, the structure was refined with 25 parameters to R sub WP = 6.30%, R sub P = 4.38% for 3551 step intensities and R sub b = 5.01%, R sub f = 4.20% for 156 reflections. The goodness of fitting S=3.18. At 100K, cell parameters a=3.8866(4) A, c= 12.289(1) A, the structure was refined with 26 parameters to R sub WP = 8.42%, R sub P = 6.21% for 2676 step intensities and R sub b = 6.72%, R sub f = 5.28% for 120 reflections. The goodness of fitting S=2.32. Reasonable anisotropic thermal parameters were obtained. The compositions of Ba and Sr atoms were refined to about Ba sub 1.1 Sr sub 0.9 compared with the stoichiometric Ba sub 1.0 Sr sub 1.0

  10. Study of the crystallite size of nitrosylpentacyanoferrate through refinement of structures

    International Nuclear Information System (INIS)

    Jimenez G, J.A.; Yee M, H.T.; Balmaceda E, J.; Reguera R, E.

    2006-01-01

    The development reached in the instrumentation and in the computer science of the diffraction of rays X, it has enlarged the reach of the method of powders considerably, in the resolution of crystalline structures of polycrystalline material converting it in a potent tool that, attended by spectroscopic techniques, it allows the fine characterization to atomic scale of having been accustomed to crystalline. In the thesis it is developed an effective methodology of determination of the crystallite size and structural refinement starting from data of diffraction of powders, based on the use of the equation of Sherrer for the estimate of the crystallite size and the method of Rietveld for the structural refinement; supplemented with the employment of the spectroscopic methods (IR and Moessbauer). The combined use of these techniques in the structural study of having been accustomed to crystalline lens of high complexity provides a novel and advanced work. The estimate of the crystallite size, it has been little explored to study accustomed to crystalline such as the pentacyanonitrosyl ferrates. One of the reasons for the which have intended to study the glass size in these structures it is due to that the molecular materials have attracted the attention of the international scientific community for their promissory properties in fields so diverse as: the absorption, desorption and separation of gases among others. Of the entreated information by means of databases and articles of scientific popularization were refined the structures of two compounds (NPCo and NPNi) obtained by powders diffraction; offering the possibility to develop a titled work: 'Physical description of the desorption of the water in nano structured material of nitrosyl penta cyano ferrates' which is carried out in parallel way to this thesis. This tools supplemented with the spectroscopic methods, potent the reach of the methods of diffraction of powders for the structural study of having been

  11. Creating value in refining

    International Nuclear Information System (INIS)

    Cobb, C.B.

    2001-01-01

    This article focuses on recent developments in the US refining industry and presents a model for improving the performance of refineries based on the analysis of the refining industry by Cap Gemini Ernst and Young. The identification of refineries in risk of failing, the construction of pipelines for refinery products from Gulf State refineries, mergers and acquisitions, and poor financial performance are discussed. Current challenges concerning the stagnant demand for refinery products, environmental regulations, and shareholder value are highlighted. The structure of the industry, the creation of value in refining, and the search for business models are examined. The top 25 US companies and US refining business groups are listed

  12. Methadone Detoxification Versus Traditional Gradual Decrease in the Consumed Amount of Refined Opium Dross (Shireh: The Preferred Method for Controlling Withdrawal Syndrome

    Directory of Open Access Journals (Sweden)

    Mohammadreza Farsinejad

    2012-08-01

    Full Text Available Background: The aim of this study was to compare the effectiveness of methadone detoxification with traditional method of gradual decrement in the abused amount of the refined opium dross (Shireh to control withdrawal syndrome in Shireh-addicted patients. Methods: In this study, two groups of Shireh addicts were compared. The first group was treated by methadone and the second group by gradual decrement in the amount of consumed Shireh. Those experiencing the adverse effects of the treatment were excluded from the study. Methadone dose was calculated based on the amount of the Shireh consumed and detoxification was performed during a 21-day period. In the second group, the amount of the consumed Shireh was gradually decreased within 21 days and some of the withdrawal symptoms were selected as indicators for patient evaluation. Results: A total of 35 patients (16 versus 19 patients in the first and second groups were evaluated. Their mean age was 43 ± 4 years and all were male. A statistically significant difference was found between these two groups in terms of severity and duration of withdrawal symptoms within the first five days and their duration after the 21st day of the onset of detoxification (P< 0.05. Conclusion: In comparison with methadone detoxification, traditional method of gradually decreasing the consumed amount of Shireh controls the severity and duration of withdrawal symptoms better in the course of detoxification.

  13. Bauxite Mining and Alumina Refining

    Science.gov (United States)

    Frisch, Neale; Olney, David

    2014-01-01

    Objective: To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Methods: Review article. Results: The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust, alumina dust, and caustic mist in contemporary best-practice bauxite mining and alumina refining operations have not been demonstrated to be associated with clinically significant decrements in lung function. Exposures to bauxite dust and alumina dust at such operations are also not associated with the incidence of cancer. Conclusions: A range of occupational health risks in bauxite mining and alumina refining require the maintenance of effective control measures. PMID:24806720

  14. Multigrid for refined triangle meshes

    Energy Technology Data Exchange (ETDEWEB)

    Shapira, Yair

    1997-02-01

    A two-level preconditioning method for the solution of (locally) refined finite element schemes using triangle meshes is introduced. In the isotropic SPD case, it is shown that the condition number of the preconditioned stiffness matrix is bounded uniformly for all sufficiently regular triangulations. This is also verified numerically for an isotropic diffusion problem with highly discontinuous coefficients.

  15. Relational Demonic Fuzzy Refinement

    Directory of Open Access Journals (Sweden)

    Fairouz Tchier

    2014-01-01

    Full Text Available We use relational algebra to define a refinement fuzzy order called demonic fuzzy refinement and also the associated fuzzy operators which are fuzzy demonic join (⊔fuz, fuzzy demonic meet (⊓fuz, and fuzzy demonic composition (□fuz. Our definitions and properties are illustrated by some examples using mathematica software (fuzzy logic.

  16. Refining cost-effectiveness analyses using the net benefit approach and econometric methods: an example from a trial of anti-depressant treatment.

    Science.gov (United States)

    Sabes-Figuera, Ramon; McCrone, Paul; Kendricks, Antony

    2013-04-01

    Economic evaluation analyses can be enhanced by employing regression methods, allowing for the identification of important sub-groups and to adjust for imperfect randomisation in clinical trials or to analyse non-randomised data. To explore the benefits of combining regression techniques and the standard Bayesian approach to refine cost-effectiveness analyses using data from randomised clinical trials. Data from a randomised trial of anti-depressant treatment were analysed and a regression model was used to explore the factors that have an impact on the net benefit (NB) statistic with the aim of using these findings to adjust the cost-effectiveness acceptability curves. Exploratory sub-samples' analyses were carried out to explore possible differences in cost-effectiveness. Results The analysis found that having suffered a previous similar depression is strongly correlated with a lower NB, independent of the outcome measure or follow-up point. In patients with previous similar depression, adding an selective serotonin reuptake inhibitors (SSRI) to supportive care for mild-to-moderate depression is probably cost-effective at the level used by the English National Institute for Health and Clinical Excellence to make recommendations. This analysis highlights the need for incorporation of econometric methods into cost-effectiveness analyses using the NB approach.

  17. A self-consistent MoD-WM/MM structural refinement method: characterization of hydrogen bonding in the orytricha nova G-1uar

    Energy Technology Data Exchange (ETDEWEB)

    Batista, Enrique R [Los Alamos National Laboratory; Newcomer, Micharel B [YALE UNIV; Raggin, Christina M [YALE UNIV; Gascon, Jose A [YALE UNIV; Loria, J Patrick [YALE UNIV; Batista, Victor S [YALE UNIV

    2008-01-01

    This paper generalizes the MoD-QM/MM hybrid method, developed for ab initio computations of protein electrostatic potentials [Gasc6n, l.A.; Leung, S.S.F.; Batista, E.R.; Batista, V.S. J. Chem. Theory Comput. 2006,2, 175-186], as a practical algorithm for structural refinement of extended systems. The computational protocol involves a space-domain decomposition scheme for the formal fragmentation of extended systems into smaller, partially overlapping, molecular domains and the iterative self-consistent energy minimization of the constituent domains by relaxation of their geometry and electronic structure. The method accounts for mutual polarization of the molecular domains, modeled as Quantum-Mechanical (QM) layers embedded in the otherwise classical Molecular-Mechanics (MM) environment according to QM/MM hybrid methods. The method is applied to the description of benchmark models systems that allow for direct comparisons with full QM calculations, and subsequently applied to the structural characterization of the DNA Oxytricha nova Guanine quadruplex (G4). The resulting MoD-QM/MM structural model of the DNA G4 is compared to recently reported highresolution X-ray diffraction and NMR models, and partially validated by direct comparisons between {sup 1}H NMR chemical shifts that are highly sensitive to hydrogen-bonding and stacking interactions and the corresponding theoretical values obtained at the density functional theory DFT QM/MM (BH&H/6-31 G*:Amber) level in conjunction with the gauge independent atomic orbital (GIAO) method for the ab initio self consistent-field (SCF) calculation of NMR chemical shifts.

  18. Analysis of the zirconia structure by `ab initio` and Rietveld methods; Analise da estrutura da zirconia por metodos `Ab initio` e de Rietveld

    Energy Technology Data Exchange (ETDEWEB)

    Bechepeche, A.P.; Nasar, R.S.; Longo, E. [Sao Carlos Univ., SP (Brazil). Dept. de Quimica; Treu Junior, O.; Varela, J.A. [UNESP, Araraquara, SP (Brazil). Inst. de Quimica

    1995-12-31

    The zirconia was doped with 0,113 mol of Mg O e 0,005 mol of Ti O{sub 2}, and it was calcined in 1550{sup d}eg C and it was analyzed by XRD. The results shows that pure zirconia contains 96,19% of monoclinic phase and 3,18% of cubic. However, the doping magnesia stabilizes the zirconia in 17,24 of monoclinic; 29,63 of tetragonal and 53,13% of cubic phase. The addition of titanium in zirconia gives 25,85% of tetragonal phase and 37,66% of cubic, and this shows the no stabilizing action of this transition metal. By the other side, the results with ab-initio calculating shows the same tendency resulting in the next values of total energy: pure zirconia - monoclinic -11.316,86ua; tetragonal -8742,09 ua and cubic -8742,80 ua and Zr O{sub 2} Ti O{sub 2} system - monoclinic -9463,02 ua, tetragonal -9459,39 ua and cubic -9459,97 ua (author) 3 figs., 2 tabs.

  19. An Isogeometric Design-through-analysis Methodology based on Adaptive Hierarchical Refinement of NURBS, Immersed Boundary Methods, and T-spline CAD Surfaces

    Science.gov (United States)

    2012-01-22

    Bungartz HJ, Rank E, Niggl A, Romberg R. Extending the p-Version of Finite Elements by an Octree-Based Hierarchy. In: Widlund OB, Keyes DE (eds...generalization to higher dimensions. We test hierarchical refinement of NURBS for some elementary fluid and structural analysis problems in two and three...with straightforward implementation in tree data structures and simple generalization to higher dimensions. We test hierarchical refinement of NURBS

  20. Creating a simplified model of oil refining and solution of the model using a linear programming method. Part 1, Model presentation

    Energy Technology Data Exchange (ETDEWEB)

    Duric, M; Novakovic, M; Stojkanovic, L

    1983-01-01

    Based on a detailed analysis of technological limitations in oil refining at an oil refinery (NPZ) in the separation of petroleum products, specifications with regard to quality and market limitations, a general model is created of oil refining. The number of actual variables is reduced to a minimum, while the number of linear limitations is adapted to the selected technology and raw material quality. The nonlinearity of certain characteristics is overcome using the so called movement factor.

  1. Analysis and development of spatial hp-refinement methods for solving the neutron transport equation; Analyse et developpement de methodes de raffinement hp en espace pour l'equation de transport des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, D.

    2011-10-10

    The different neutronic parameters have to be calculated with a higher accuracy in order to design the 4. generation reactor cores. As memory storage and computation time are limited, adaptive methods are a solution to solve the neutron transport equation. The neutronic flux, solution of this equation, depends on the energy, angle and space. The different variables are successively discretized. The energy with a multigroup approach, considering the different quantities to be constant on each group, the angle by a collocation method called SN approximation. Once the energy and angle variable are discretized, a system of spatially-dependent hyperbolic equations has to be solved. Discontinuous finite elements are used to make possible the development of hp-refinement methods. Thus, the accuracy of the solution can be improved by spatial refinement (h-refinement), consisting into subdividing a cell into sub-cells, or by order refinement (p-refinement), by increasing the order of the polynomial basis. In this thesis, the properties of this methods are analyzed showing the importance of the regularity of the solution to choose the type of refinement. Thus, two error estimators are used to lead the refinement process. Whereas the first one requires high regularity hypothesis (analytical solution), the second one supposes only the minimal hypothesis required for the solution to exist. The comparison of both estimators is done on benchmarks where the analytic solution is known by the method of manufactured solutions. Thus, the behaviour of the solution as a regard of the regularity can be studied. It leads to a hp-refinement method using the two estimators. Then, a comparison is done with other existing methods on simplified but also realistic benchmarks coming from nuclear cores. These adaptive methods considerably reduces the computational cost and memory footprint. To further improve these two points, an approach with energy-dependent meshes is proposed. Actually, as the

  2. A refined, rapid and reproducible high resolution melt (HRM-based method suitable for quantification of global LINE-1 repetitive element methylation

    Directory of Open Access Journals (Sweden)

    Tse M Yat

    2011-12-01

    Full Text Available Abstract Background The methylation of DNA is recognized as a key mechanism in the regulation of genomic stability and evidence for its role in the development of cancer is accumulating. LINE-1 methylation status represents a surrogate measure of genome-wide methylation. Findings Using high resolution melt (HRM curve analysis technology, we have established an in-tube assay that is linear (r > 0.9986 with a high amplification efficiency (90-105%, capable of discriminating between partcipant samples with small differences in methylation, and suitable for quantifying a wide range of LINE-1 methylation levels (0-100%--including the biologically relevant range of 50-90% expected in human DNA. We have optimized this procedure to perform using 2 μg of starting DNA and 2 ng of bisulfite-converted DNA for each PCR reaction. Intra- and inter-assay coefficients of variation were 1.44% and 0.49%, respectively, supporting the high reproducibility and precision of this approach. Conclusions In summary, this is a completely linear, quantitative HRM PCR method developed for the measurement of LINE-1 methylation. This cost-efficient, refined and reproducible assay can be performed using minimal amounts of starting DNA. These features make our assay suitable for high throughput analysis of multiple samples from large population-based studies.

  3. Refining margins and prospects

    International Nuclear Information System (INIS)

    Baudouin, C.; Favennec, J.P.

    1997-01-01

    Refining margins throughout the world have remained low in 1996. In Europe, in spite of an improvement, particularly during the last few weeks, they are still not high enough to finance new investments. Although the demand for petroleum products is increasing, experts are still sceptical about any rapid recovery due to prevailing overcapacity and to continuing capacity growth. After a historical review of margins and an analysis of margins by regions, we analyse refining over-capacities in Europe and the unbalances between production and demand. Then we discuss the current situation concerning barriers to the rationalization, agreements between oil companies, and the consequences on the future of refining capacities and margins. (author)

  4. North American refining

    International Nuclear Information System (INIS)

    Osten, James; Haltmaier, Susan

    2000-01-01

    This article examines the current status of the North American refining industry, and considers the North American economy and the growth in demand in the petroleum industry, petroleum product demand and quality, crude oil upgrading to meet product standards, and changes in crude oil feedstocks such as the use of heavier crudes and bitumens. Refining expansion, the declining profits in refining, and changes due to environmental standards are discussed. The Gross Domestic Product and oil demand for the USA, Canada, Mexico, and Venezuela for the years 1995-2020 are tabulated

  5. Application of low current intensity electrolytic treatment for the chlorides extraction in underwater archaeological objects of iron. Observation of the mineralogical phases evolution through XRD-Rietveld

    International Nuclear Information System (INIS)

    Bethencourt, M.; Gil, M. L. A.; Fernandez-Lorenzo, C.; Santos, A.

    2004-01-01

    With the purpose of optimising a suitable methodology for the conservation of an archaeological object of iron, a low current intensities electrolytic treatment has been applied, to a piece of cast iron, proving to be effective in the extraction of chloride ions from the structure of akaganeite, principal corrosion product of iron in the marine medium. The monitoring of the electrolytic treatment has been proven by applying the Rietveld method to the patterns XRD of samples extracted from the corroded surface before and after the treatment. This method has permitted the unequivocal determination of the akaganeite and its chemical composition. This identification has been corroborated by means of SEM and EDS. After the electrolytic treatment, akaganeite was not present in the sample. (Author) 9 refs

  6. Adaptive multilevel mesh refinement method for the solution of low Mach number reactive flows; Methode adaptative de raffinement local multi-niveaux pour le calcul d'ecoulements reactifs a faible nombre de Mach

    Energy Technology Data Exchange (ETDEWEB)

    Core, X.

    2002-02-01

    The isobar approximation for the system of the balance equations of mass, momentum, energy and chemical species is a suitable approximation to represent low Mach number reactive flows. In this approximation, which neglects acoustics phenomena, the mixture is hydrodynamically incompressible and the thermodynamic effects lead to an uniform compression of the system. We present a novel numerical scheme for this approximation. An incremental projection method, which uses the original form of mass balance equation, discretizes in time the Navier-Stokes equations. Spatial discretization is achieved through a finite volume approach on MAC-type staggered mesh. A higher order de-centered scheme is used to compute the convective fluxes. We associate to this discretization a local mesh refinement method, based on Flux Interface Correction technique. A first application concerns a forced flow with variable density which mimics a combustion problem. The second application is natural convection with first small temperature variations and then beyond the limit of validity of the Boussinesq approximation. Finally, we treat a third application which is a laminar diffusion flame. For each of these test problems, we demonstrate the robustness of the proposed numerical scheme, notably for the density spatial variations. We analyze the gain in accuracy obtained with the local mesh refinement method. (author)

  7. Analysis of the zirconia structure by 'ab initio' and Rietveld methods

    International Nuclear Information System (INIS)

    Bechepeche, A.P.; Nasar, R.S.; Longo, E.; Treu Junior, O.; Varela, J.A.

    1995-01-01

    The zirconia was doped with 0,113 mol of Mg O e 0,005 mol of Ti O 2 , and it was calcined in 1550 d eg C and it was analyzed by XRD. The results shows that pure zirconia contains 96,19% of monoclinic phase and 3,18% of cubic. However, the doping magnesia stabilizes the zirconia in 17,24 of monoclinic; 29,63 of tetragonal and 53,13% of cubic phase. The addition of titanium in zirconia gives 25,85% of tetragonal phase and 37,66% of cubic, and this shows the no stabilizing action of this transition metal. By the other side, the results with ab-initio calculating shows the same tendency resulting in the next values of total energy: pure zirconia - monoclinic -11.316,86ua; tetragonal -8742,09 ua and cubic -8742,80 ua and Zr O 2 Ti O 2 system - monoclinic -9463,02 ua, tetragonal -9459,39 ua and cubic -9459,97 ua (author)

  8. Linearly Refined Session Types

    Directory of Open Access Journals (Sweden)

    Pedro Baltazar

    2012-11-01

    Full Text Available Session types capture precise protocol structure in concurrent programming, but do not specify properties of the exchanged values beyond their basic type. Refinement types are a form of dependent types that can address this limitation, combining types with logical formulae that may refer to program values and can constrain types using arbitrary predicates. We present a pi calculus with assume and assert operations, typed using a session discipline that incorporates refinement formulae written in a fragment of Multiplicative Linear Logic. Our original combination of session and refinement types, together with the well established benefits of linearity, allows very fine-grained specifications of communication protocols in which refinement formulae are treated as logical resources rather than persistent truths.

  9. Refinement by interface instantiation

    DEFF Research Database (Denmark)

    Hallerstede, Stefan; Hoang, Thai Son

    2012-01-01

    be easily refined. Our first contribution hence is a proposal for a new construct called interface that encapsulates the external variables, along with a mechanism for interface instantiation. Using the new construct and mechanism, external variables can be refined consistently. Our second contribution...... is an approach for verifying the correctness of Event-B extensions using the supporting Rodin tool. We illustrate our approach by proving the correctness of interface instantiation....

  10. Relational Demonic Fuzzy Refinement

    OpenAIRE

    Tchier, Fairouz

    2014-01-01

    We use relational algebra to define a refinement fuzzy order called demonic fuzzy refinement and also the associated fuzzy operators which are fuzzy demonic join $({\\bigsqcup }_{\\mathrm{\\text{f}}\\mathrm{\\text{u}}\\mathrm{\\text{z}}})$ , fuzzy demonic meet $({\\sqcap }_{\\mathrm{\\text{f}}\\mathrm{\\text{u}}\\mathrm{\\text{z}}})$ , and fuzzy demonic composition $({\\square }_{\\mathrm{\\text{f}}\\mathrm{\\text{u}}\\mathrm{\\text{z}}})$ . Our definitions and properties are illustrated by some examples using ma...

  11. A posteriori estimator and adaptive mesh refinement for finite volume finite element method for monophasic flow and solute transport in porous media

    International Nuclear Information System (INIS)

    Amor, H.; Bourgeois, M.

    2012-01-01

    using an adaptive mesh refinement strategy was introduced in MELODIE for the simulation of groundwater flow and solute transport in saturated porous media in 2 dimensions. The selected estimator, based on the explicit residual error, is expected to allow local refinements and thus minimization of the discretization error at an optimal computational cost. Test case: a realistic heterogeneous case with fracturing. In addition to theoretical test cases a more complex case was tested. The purpose of this test case was twofold: - to move from pure theoretical work to an illustrative case within a realistic generic context; however parameter values for hydrodynamic characteristics were chosen so as to highlight the investigated phenomena; - to account for large time and space scales, representative for those required for the simulation of radioactive waste repositories. The general shape of the geological media was designed to cover main features representative of sedimentary formations. Three distinct radionuclide source locations were chosen in order to obtain a set of flow and transport configurations. The entire layer sequence was structured into three hydrogeological units intersected by three sub-vertical faults. The vertical 2D cross-section dimensions are 5 km long by 500 m thick. Two source terms are located in a 100 m-thick layer in the right part of the domain and another one is located in a larger layer in the left part. These two 'host rock' layers consist of the same sedimentary unit with a low permeability, though an offset due to the middle fault. Faults are considered as conductive features. Radionuclides are assumed to be instantaneously released from the three source term locations at t = 0. The a posteriori error estimator and the adaptive mesh algorithm were applied to this heterogeneous problem. Preliminary calculations showed that the implemented a posteriori error estimator method is efficient to solve the equations of flow and advective

  12. Optimal algebraic multilevel preconditioning for local refinement along a line

    NARCIS (Netherlands)

    Margenov, S.D.; Maubach, J.M.L.

    1995-01-01

    The application of some recently proposed algebraic multilevel methods for the solution of two-dimensional finite element problems on nonuniform meshes is studied. The locally refined meshes are created by the newest vertex mesh refinement method. After the introduction of this refinement technique

  13. A Method to Increase Current Density in a Mono Element Internal Tin Processed Superconductor Utilizing Zr Oxide to Refine Grain Size; Final Report Phase 2

    International Nuclear Information System (INIS)

    Zeitlin, Bruce A.; Gregory, Eric

    2008-01-01

    The effect of Oxygen on (Nb1Zr)3Sn multifilament conductors manufactured by the Mono Element Internal Tin (MEIT) process was explored to improve the current density by refining the grain size. This followed work first done by General Electric on the Nb3Sn tape process. Techniques to fabricate the more difficult Nb1Zr composites are described and allowed fabrication of long lengths of .254 mm diameter wire from an 88.9 mm diameter billet. Oxygen was incorporated through the use of SnO2 mixed with tin powder and incorporated into the core. These were compared to samples with Ti+Sn and Cu+Sn cores. Heat treatments covered the range of 700 C to 1000 C. Current density vs. H, grain size, and reaction percentages are provided for the materials tested. The Oxygen gave superior results in the temperature range of 815-1000 C. It also stabilized the filament geometry of the array in comparison to the other additions at the higher temperatures. At 815 C a peak in layer Jc yielded values of 2537 A/mm2 at 12 T and 1353 A/mm2 at 15T, 8-22% and 30-73% greater respectively than 700 C values. Results with Oxygen at high temperature show the possibility of high speed continuous reaction of the composite versus the current batch or react in place methods. In general the Ti additions gave superior results at the lower reaction temperature. Future work is suggested to determine if the 815 C reaction temperature can lead to higher current density in high tin (Nb1Zr+Ox)3Sn conductors. A second technique incorporated oxygen directly into the Nb1Zr rods through heat treatment with Nb2O5 at 1100 C for 100 hours in vacuum prior to extrusion. The majority of the filaments reduced properly in the composite but some local variations in hardness led to breakage at smaller diameters.

  14. Bauxite Mining and Alumina Refining

    OpenAIRE

    Donoghue, A. Michael; Frisch, Neale; Olney, David

    2014-01-01

    Objective: To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Methods: Review article. Results: The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust,...

  15. Refining margins: recent trends

    International Nuclear Information System (INIS)

    Baudoin, C.; Favennec, J.P.

    1999-01-01

    Despite a business environment that was globally mediocre due primarily to the Asian crisis and to a mild winter in the northern hemisphere, the signs of improvement noted in the refining activity in 1996 were borne out in 1997. But the situation is not yet satisfactory in this sector: the low return on invested capital and the financing of environmental protection expenditure are giving cause for concern. In 1998, the drop in crude oil prices and the concomitant fall in petroleum product prices was ultimately rather favorable to margins. Two elements tended to put a damper on this relative optimism. First of all, margins continue to be extremely volatile and, secondly, the worsening of the economic and financial crisis observed during the summer made for a sharp decline in margins in all geographic regions, especially Asia. Since the beginning of 1999, refining margins are weak and utilization rates of refining capacities have decreased. (authors)

  16. Refining and petrochemicals

    Energy Technology Data Exchange (ETDEWEB)

    Constancio, Silva

    2006-07-01

    In 2004, refining margins showed a clear improvement that persisted throughout the first three quarters of 2005. This enabled oil companies to post significantly higher earnings for their refining activity in 2004 compared to 2003, with the results of the first half of 2005 confirming this trend. As for petrochemicals, despite a steady rise in the naphtha price, higher cash margins enabled a turnaround in 2004 as well as a clear improvement in oil company financial performance that should continue in 2005, judging by the net income figures reported for the first half-year. Despite this favorable business environment, capital expenditure in refining and petrochemicals remained at a low level, especially investment in new capacity, but a number of projects are being planned for the next five years. (author)

  17. Refining and petrochemicals

    International Nuclear Information System (INIS)

    Constancio, Silva

    2006-01-01

    In 2004, refining margins showed a clear improvement that persisted throughout the first three quarters of 2005. This enabled oil companies to post significantly higher earnings for their refining activity in 2004 compared to 2003, with the results of the first half of 2005 confirming this trend. As for petrochemicals, despite a steady rise in the naphtha price, higher cash margins enabled a turnaround in 2004 as well as a clear improvement in oil company financial performance that should continue in 2005, judging by the net income figures reported for the first half-year. Despite this favorable business environment, capital expenditure in refining and petrochemicals remained at a low level, especially investment in new capacity, but a number of projects are being planned for the next five years. (author)

  18. Indian refining industry

    International Nuclear Information System (INIS)

    Singh, I.J.

    2002-01-01

    The author discusses the history of the Indian refining industry and ongoing developments under the headings: the present state; refinery configuration; Indian capabilities for refinery projects; and reforms in the refining industry. Tables lists India's petroleum refineries giving location and capacity; new refinery projects together with location and capacity; and expansion projects of Indian petroleum refineries. The Indian refinery industry has undergone substantial expansion as well as technological changes over the past years. There has been progressive technology upgrading, energy efficiency, better environmental control and improved capacity utilisation. Major reform processes have been set in motion by the government of India: converting the refining industry from a centrally controlled public sector dominated industry to a delicensed regime in a competitive market economy with the introduction of a liberal exploration policy; dismantling the administered price mechanism; and a 25 year hydrocarbon vision. (UK)

  19. Refining - Panorama 2008

    International Nuclear Information System (INIS)

    2008-01-01

    Investment rallied in 2007, and many distillation and conversion projects likely to reach the industrial stage were announced. With economic growth sustained in 2006 and still pronounced in 2007, oil demand remained strong - especially in emerging countries - and refining margins stayed high. Despite these favorable business conditions, tensions persisted in the refining sector, which has fallen far behind in terms of investing in refinery capacity. It will take renewed efforts over a long period to catch up. Looking at recent events that have affected the economy in many countries (e.g. the sub-prime crisis), prudence remains advisable

  20. A new method of Debye-Scherrer pattern integration on two-dimensional detectors, demonstrated for the new structure powder diffractometer (SPODI) at the FRM-II in Garching

    CERN Document Server

    Elf, F; Artus, G R J; Roth, S

    2002-01-01

    The expected diffraction patterns of the new powder diffractometer SPODI, currently under construction at the FRM-II in Garching, will be smeared Debye-Scherrer rings as depicted by Monte Carlo (MC) simulations. To overcome this disadvantage, a concept based on the combination of MC simulations and empirical approximation methods is developed to reverse the smearing by deconvolution and then summing up along the rings, including corrections for different arc lengths, resulting in conventional one-dimensional diffraction patterns suitable for Rietveld-refinement programs without further processing. (orig.)

  1. Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution: A Rietveld study

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Rishikesh, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2014-07-28

    We present here the results of structural studies on multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The results of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for “B-site cations-oxygen anions” obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.

  2. Panorama 2012 - Refining 2030

    International Nuclear Information System (INIS)

    Marion, Pierre; Saint-Antonin, Valerie

    2011-11-01

    The major uncertainty characterizing the global energy landscape impacts particularly on transport, which remains the virtually-exclusive bastion of the oil industry. The industry must therefore respond to increasing demand for mobility against a background marked by the emergence of alternatives to oil-based fuels and the need to reduce emissions of pollutants and greenhouse gases (GHG). It is in this context that the 'Refining 2030' study conducted by IFP Energies Nouvelles (IFPEN) forecasts what the global supply and demand balance for oil products could be, and highlights the type and geographical location of the refinery investment required. Our study shows that the bulk of the refining investment will be concentrated in the emerging countries (mainly those in Asia), whilst the areas historically strong in refining (Europe and North America) face reductions in capacity. In this context, the drastic reduction in the sulphur specification of bunker oil emerges as a structural issue for European refining, in the same way as increasingly restrictive regulation of refinery CO 2 emissions (quotas/taxation) and the persistent imbalance between gasoline and diesel fuels. (authors)

  3. Electronic structure and magnetic properties of FeWO{sub 4} nanocrystals synthesized by the microwave-hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, M.A.P. [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil); Cavalcante, L.S., E-mail: laeciosc@bol.com.br [INCTMN-Universidade Estadual, Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil); Morilla-Santos, C.; Filho, P.N. Lisboa [MAv-Universidade Estadual, Paulista, P.O. Box 473, 17033-360, Bauru, SP (Brazil); Beltran, A.; Andres, J.; Gracia, L. [Department de Quimica Fisica i Analitica, Universitat Jaume I, E-12071 Castello (Spain); Longo, E. [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil); INCTMN-Universidade Estadual, Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil)

    2012-11-15

    This communication reports that FeWO{sub 4} nanocrystals were successfully synthesized by the microwave-hydrothermal method at 443 K for 1 h. The structure and shape of these nanocrystals were characterized by X-ray diffraction, Rietveld refinement, and transmission electron microscopy. The experimental results and first principles calculations were combined to explain the electronic structure and magnetic properties. Experimental data were obtained by magnetization measurements for different applied magnetic fields. Theoretical calculations revealed that magnetic properties of FeWO{sub 4} nanocrystals can be assigned to two magnetic orderings with parallel or antiparallel spins in adjacent chains. These factors are crucial to understanding of competition between ferro- and antiferromagnetic behavior. Highlights: Black-Right-Pointing-Pointer Monophasic FeWO{sub 4} nanocrystals were synthesized by the microwave-hydrothermal method. Black-Right-Pointing-Pointer Rietveld refinement and clusters model for monoclinic structure Black-Right-Pointing-Pointer Magnetic properties of FeWO{sub 4} nanocrystals at different temperatures.

  4. Rietveld refinement of the langbeinite-type mixed-metal phosphate K2Ni0.5Zr1.5(PO43

    Directory of Open Access Journals (Sweden)

    Igor V. Zatovsky

    2014-07-01

    Full Text Available Dipotassium [nickel(II zirconium(IV] tris(orthophosphate was prepared from a self-flux in the system K2O–P2O5–NiO–K2ZrF6. The title compound belongs to the langbeinite family and is built up from two [MO6] octahedra [M = Ni:Zr with mixed occupancy in ratios of 0.21 (4:0.79 (4 and 0.29 (4:0.71 (4, respectively] and [PO4] tetrahedra interlinked via vertices into a 3∞[M2(PO43] framework. Two independent K+ cations are located in large cavities of the framework, with coordination numbers to O2− anions of nine and twelve. The K, Ni, and Zr sites are located on threefold rotation axes.

  5. US refining reviewed

    International Nuclear Information System (INIS)

    Yamaguchi, N.D.

    1998-01-01

    The paper reviews the history, present position and future prospects of the petroleum industry in the USA. The main focus is on supply and demand, the high quality of the products, refinery capacity and product trade balances. Diagrams show historical trends in output, product demand, demand for transport fuels and oil, refinery capacity, refinery closures, and imports and exports. Some particularly salient points brought out were (i) production of US crude shows a marked downward trend but imports of crude will continue to increase, (ii) product demand will continue to grow even though the levels are already high, (iii) the demand is dominated by those products that typically yield the highest income for the refiner, (i.e. high quality transport fuels for environmental compliance), (iv) refinery capacity has decreased since 1980 and (v) refining will continue to have financial problems but will still be profitable. (UK)

  6. Outlook for Canadian refining

    International Nuclear Information System (INIS)

    Boje, G.

    1998-01-01

    The petroleum supply and demand balance was discussed and a comparison between Canadian and U.S. refineries was provided. The impact of changing product specifications on the petroleum industry was also discussed. The major changes include sulphur reductions in gasoline, benzene and MMT additives. These changes have been made in an effort to satisfy environmental needs. Geographic margin variations in refineries between east and west were reviewed. An overview of findings from the Solomon Refining Study of Canadian and American refineries, which has been very complimentary of the Canadian refining industry, was provided. From this writer's point of view refinery utilization has improved but there is a threat from increasing efficiency of US competitors. Environmental issues will continue to impact upon the industry and while the chances for making economic returns on investment are good for the years ahead, it will be a challenge to maintain profitability

  7. Future of French refining

    International Nuclear Information System (INIS)

    Calvet, B.

    1993-01-01

    Over recent years, the refining industry has had to grapple with a growing burden of environmental and safety regulations concerning not only its plants and other facilities, but also its end products. At the same time, it has had to bear the effects of the reduction of the special status that used to apply to petroleum, and the consequences of economic freedom, to which we should add, as specifically concerns the French market, the impact of energy policy and the pro-nuclear option. The result is a drop in heavy fuel oil from 36 million tonnes per year in 1973 to 6.3 million in 1992, and in home-heating fuel from 37 to 18 million per year. This fast-moving market is highly competitive. The French market in particular is wide open to imports, but the refining companies are still heavy exporters for those products with high added-value, like lubricants, jet fuel, and lead-free gasolines. The competition has led the refining companies to commit themselves to quality, and to publicize their efforts in this direction. This is why the long-term perspectives for petroleum fuels are still wide open. This is supported by the probable expectation that the goal of economic efficiency is likely to soften the effects of the energy policy, which penalizes petroleum products, in that they have now become competitive again. In the European context, with the challenge of environmental protection and the decline in heavy fuel outlets, French refining has to keep on improving the quality of its products and plants, which means major investments. The industry absolutely must return to a more normal level of profitability, in order to sustain this financial effort, and generate the prosperity of its high-performance plants and equipment. 1 fig., 5 tabs

  8. Process for refining hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Risenfeld, E H

    1924-11-26

    A process is disclosed for the refining of hydrocarbons or other mixtures through treatment in vapor form with metal catalysts, characterized by such metals being used as catalysts, which are obtained by reduction of the oxide of minerals containing the iron group, and by the vapors of the hydrocarbons, in the presence of the water vapor, being led over these catalysts at temperatures from 200 to 300/sup 0/C.

  9. Panorama 2009 - refining

    International Nuclear Information System (INIS)

    2008-01-01

    For oil companies to invest in new refining and conversion capacity, favorable conditions over time are required. In other words, refining margins must remain high and demand sustained over a long period. That was the situation prevailing before the onset of the financial crisis in the second half of 2008. The economic conjuncture has taken a substantial turn for the worse since then and the forecasts for 2009 do not look bright. Oil demand is expected to decrease in the OECD countries and to grow much more slowly in the emerging countries. It is anticipated that refining margins will fall in 2009 - in 2008, they slipped significantly in the United States - as a result of increasingly sluggish demand, especially for light products. The next few months will probably be unfavorable to investment. In addition to a gloomy business outlook, there may also be a problem of access to sources of financing. As for investment projects, a mainstream trend has emerged in the last few years: a shift away from the regions that have historically been most active (the OECD countries) towards certain emerging countries, mostly in Asia or the Middle East. The new conjuncture will probably not change this trend

  10. Refining discordant gene trees.

    Science.gov (United States)

    Górecki, Pawel; Eulenstein, Oliver

    2014-01-01

    Evolutionary studies are complicated by discordance between gene trees and the species tree in which they evolved. Dealing with discordant trees often relies on comparison costs between gene and species trees, including the well-established Robinson-Foulds, gene duplication, and deep coalescence costs. While these costs have provided credible results for binary rooted gene trees, corresponding cost definitions for non-binary unrooted gene trees, which are frequently occurring in practice, are challenged by biological realism. We propose a natural extension of the well-established costs for comparing unrooted and non-binary gene trees with rooted binary species trees using a binary refinement model. For the duplication cost we describe an efficient algorithm that is based on a linear time reduction and also computes an optimal rooted binary refinement of the given gene tree. Finally, we show that similar reductions lead to solutions for computing the deep coalescence and the Robinson-Foulds costs. Our binary refinement of Robinson-Foulds, gene duplication, and deep coalescence costs for unrooted and non-binary gene trees together with the linear time reductions provided here for computing these costs significantly extends the range of trees that can be incorporated into approaches dealing with discordance.

  11. Towards automated crystallographic structure refinement with phenix.refine

    OpenAIRE

    Afonine, Pavel V.; Grosse-Kunstleve, Ralf W.; Echols, Nathaniel; Headd, Jeffrey J.; Moriarty, Nigel W.; Mustyakimov, Marat; Terwilliger, Thomas C.; Urzhumtsev, Alexandre; Zwart, Peter H.; Adams, Paul D.

    2012-01-01

    phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. It has several automation features and is also highly flexible. Several hundred parameters enable extensive customizations for complex use cases. Multiple user-defined refinement strategies can be applied to specific parts of the model in a single refinement run. An i...

  12. Refining and petrochemicals

    International Nuclear Information System (INIS)

    Benazzi, E.

    2003-01-01

    Down sharply in 2002, refining margins showed a clear improvement in the first half-year of 2003. As a result, the earnings reported by oil companies for financial year 2002 were significantly lower than in 2001, but the prospects are brighter for 2003. In the petrochemicals sector, slow demand and higher feedstock prices eroded margins in 2002, especially in Europe and the United States. The financial results for the first part of 2003 seem to indicate that sector profitability will not improve before 2004. (author)

  13. Refining and petrochemicals

    International Nuclear Information System (INIS)

    Benazzi, E.; Alario, F.

    2004-01-01

    In 2003, refining margins showed a clear improvement that continued throughout the first three quarters of 2004. Oil companies posted significantly higher earnings in 2003 compared to 2002, with the results of first quarter 2004 confirming this trend. Due to higher feedstock prices, the implementation of new capacity and more intense competition, the petrochemicals industry was not able to boost margins in 2003. In such difficult business conditions, aggravated by soaring crude prices, the petrochemicals industry is not likely to see any improvement in profitability before the second half of 2004. (author)

  14. Refining mineral oils

    Energy Technology Data Exchange (ETDEWEB)

    1946-07-05

    A process is described refining raw oils such as mineral oils, shale oils, tar, their fractions and derivatives, by extraction with a selected solvent or a mixture of solvents containing water, forming a solvent more favorable for the hydrocarbons poor in hydrogen than for hydrocarbons rich in hydrogen, this process is characterized by the addition of an aiding solvent for the water which can be mixed or dissolved in the water and the solvent or in the dissolving mixture and increasing in this way the solubility of the water in the solvent or the dissolving mixture.

  15. Contextual Distance Refining for Image Retrieval

    KAUST Repository

    Islam, Almasri

    2014-01-01

    Recently, a number of methods have been proposed to improve image retrieval accuracy by capturing context information. These methods try to compensate for the fact that a visually less similar image might be more relevant because it depicts the same object. We propose a new quick method for refining any pairwise distance metric, it works by iteratively discovering the object in the image from the most similar images, and then refine the distance metric accordingly. Test show that our technique improves over the state of art in terms of accuracy over the MPEG7 dataset.

  16. Contextual Distance Refining for Image Retrieval

    KAUST Repository

    Islam, Almasri

    2014-09-16

    Recently, a number of methods have been proposed to improve image retrieval accuracy by capturing context information. These methods try to compensate for the fact that a visually less similar image might be more relevant because it depicts the same object. We propose a new quick method for refining any pairwise distance metric, it works by iteratively discovering the object in the image from the most similar images, and then refine the distance metric accordingly. Test show that our technique improves over the state of art in terms of accuracy over the MPEG7 dataset.

  17. Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal SC2O3

    International Nuclear Information System (INIS)

    Qing-Li, Zhang; Kai-Jie, Ning; Jin, Xiao; Li-Hua, Ding; Wen-Long, Zhou; Wen-Peng, Liu; Shao-Tang, Yin; Hai-He, Jiang

    2010-01-01

    A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb 3+ in Sc 2 O 3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  18. Methods of NMR structure refinement: molecular dynamics simulations improve the agreement with measured NMR data of a C-terminal peptide of GCN4-p1

    International Nuclear Information System (INIS)

    Dolenc, Jozica; Missimer, John H.; Steinmetz, Michel O.; Gunsteren, Wilfred F. van

    2010-01-01

    The C-terminal trigger sequence is essential in the coiled-coil formation of GCN4-p1; its conformational properties are thus of importance for understanding this process at the atomic level. A solution NMR model structure of a peptide, GCN4p16-31, encompassing the GCN4-p1 trigger sequence was proposed a few years ago. Derived using a standard single-structure refinement protocol based on 172 nuclear Overhauser effect (NOE) distance restraints, 14 hydrogen-bond and 11 φ torsional-angle restraints, the resulting set of 20 NMR model structures exhibits regular α-helical structure. However, the set slightly violates some measured NOE bounds and does not reproduce all 15 measured 3 J(H N -H Cα )-coupling constants, indicating that different conformers of GCN4p16-31 might be present in solution. With the aim to resolve structures compatible with all NOE upper distance bounds and 3 J-coupling constants, we executed several structure refinement protocols employing unrestrained and restrained molecular dynamics (MD) simulations with two force fields. We find that only configurational ensembles obtained by applying simultaneously time-averaged NOE distance and 3 J-coupling constant restraining with either force field reproduce all the experimental data. Additionally, analyses of the simulated ensembles show that the conformational variability of GCN4p16-31 in solution admitted by the available set of 187 measured NMR data is larger than represented by the set of the NMR model structures. The conformations of GCN4p16-31 in solution differ in the orientation not only of the side-chains but also of the backbone. The inconsistencies between the NMR model structures and the measured NMR data are due to the neglect of averaging effects and the inclusion of hydrogen-bond and torsional-angle restraints that have little basis in the primary, i.e. measured NMR data.

  19. Methods of NMR structure refinement: molecular dynamics simulations improve the agreement with measured NMR data of a C-terminal peptide of GCN4-p1.

    Science.gov (United States)

    Dolenc, Jozica; Missimer, John H; Steinmetz, Michel O; van Gunsteren, Wilfred F

    2010-07-01

    The C-terminal trigger sequence is essential in the coiled-coil formation of GCN4-p1; its conformational properties are thus of importance for understanding this process at the atomic level. A solution NMR model structure of a peptide, GCN4p16-31, encompassing the GCN4-p1 trigger sequence was proposed a few years ago. Derived using a standard single-structure refinement protocol based on 172 nuclear Overhauser effect (NOE) distance restraints, 14 hydrogen-bond and 11 phi torsional-angle restraints, the resulting set of 20 NMR model structures exhibits regular alpha-helical structure. However, the set slightly violates some measured NOE bounds and does not reproduce all 15 measured (3)J(H(N)-H(Calpha))-coupling constants, indicating that different conformers of GCN4p16-31 might be present in solution. With the aim to resolve structures compatible with all NOE upper distance bounds and (3)J-coupling constants, we executed several structure refinement protocols employing unrestrained and restrained molecular dynamics (MD) simulations with two force fields. We find that only configurational ensembles obtained by applying simultaneously time-averaged NOE distance and (3)J-coupling constant restraining with either force field reproduce all the experimental data. Additionally, analyses of the simulated ensembles show that the conformational variability of GCN4p16-31 in solution admitted by the available set of 187 measured NMR data is larger than represented by the set of the NMR model structures. The conformations of GCN4p16-31 in solution differ in the orientation not only of the side-chains but also of the backbone. The inconsistencies between the NMR model structures and the measured NMR data are due to the neglect of averaging effects and the inclusion of hydrogen-bond and torsional-angle restraints that have little basis in the primary, i.e. measured NMR data.

  20. Atlantic Basin refining profitability

    International Nuclear Information System (INIS)

    Jones, R.J.

    1998-01-01

    A review of the profitability margins of oil refining in the Atlantic Basin was presented. Petroleum refiners face the continuous challenge of balancing supply with demand. It would appear that the profitability margins in the Atlantic Basin will increase significantly in the near future because of shrinking supply surpluses. Refinery capacity utilization has reached higher levels than ever before. The American Petroleum Institute reported that in August 1997, U.S. refineries used 99 per cent of their capacity for several weeks in a row. U.S. gasoline inventories have also declined as the industry has focused on reducing capital costs. This is further evidence that supply and demand are tightly balanced. Some of the reasons for tightening supplies were reviewed. It was predicted that U.S. gasoline demand will continue to grow in the near future. Gasoline demand has not declined as expected because new vehicles are not any more fuel efficient today than they were a decade ago. Although federally-mandated fuel efficiency standards were designed to lower gasoline consumption, they may actually have prevented consumption from falling. Atlantic margins were predicted to continue moving up because of the supply and demand evidence: high capacity utilization rates, low operating inventories, limited capacity addition resulting from lower capital spending, continued U.S. gasoline demand growth, and steady total oil demand growth. 11 figs

  1. Petroleum refining industry in China

    International Nuclear Information System (INIS)

    Walls, W.D.

    2010-01-01

    The oil refining industry in China has faced rapid growth in oil imports of increasingly sour grades of crude with which to satisfy growing domestic demand for a slate of lighter and cleaner finished products sold at subsidized prices. At the same time, the world petroleum refining industry has been moving from one that serves primarily local and regional markets to one that serves global markets for finished products, as world refining capacity utilization has increased. Globally, refined product markets are likely to experience continued globalization until refining investments significantly expand capacity in key demand regions. We survey the oil refining industry in China in the context of the world market for heterogeneous crude oils and growing world trade in refined petroleum products. (author)

  2. Methods of NMR structure refinement: molecular dynamics simulations improve the agreement with measured NMR data of a C-terminal peptide of GCN4-p1

    Energy Technology Data Exchange (ETDEWEB)

    Dolenc, Jozica [Swiss Federal Institute of Technology, Laboratory of Physical Chemistry, ETH (Switzerland); Missimer, John H.; Steinmetz, Michel O. [Paul Scherrer Institut, Biomolecular Research (Switzerland); Gunsteren, Wilfred F. van, E-mail: wfvgn@igc.phys.chem.ethz.c [Swiss Federal Institute of Technology, Laboratory of Physical Chemistry, ETH (Switzerland)

    2010-07-15

    The C-terminal trigger sequence is essential in the coiled-coil formation of GCN4-p1; its conformational properties are thus of importance for understanding this process at the atomic level. A solution NMR model structure of a peptide, GCN4p16-31, encompassing the GCN4-p1 trigger sequence was proposed a few years ago. Derived using a standard single-structure refinement protocol based on 172 nuclear Overhauser effect (NOE) distance restraints, 14 hydrogen-bond and 11 {phi} torsional-angle restraints, the resulting set of 20 NMR model structures exhibits regular {alpha}-helical structure. However, the set slightly violates some measured NOE bounds and does not reproduce all 15 measured {sup 3}J(H{sub N}-H{sub C{alpha}})-coupling constants, indicating that different conformers of GCN4p16-31 might be present in solution. With the aim to resolve structures compatible with all NOE upper distance bounds and {sup 3}J-coupling constants, we executed several structure refinement protocols employing unrestrained and restrained molecular dynamics (MD) simulations with two force fields. We find that only configurational ensembles obtained by applying simultaneously time-averaged NOE distance and {sup 3}J-coupling constant restraining with either force field reproduce all the experimental data. Additionally, analyses of the simulated ensembles show that the conformational variability of GCN4p16-31 in solution admitted by the available set of 187 measured NMR data is larger than represented by the set of the NMR model structures. The conformations of GCN4p16-31 in solution differ in the orientation not only of the side-chains but also of the backbone. The inconsistencies between the NMR model structures and the measured NMR data are due to the neglect of averaging effects and the inclusion of hydrogen-bond and torsional-angle restraints that have little basis in the primary, i.e. measured NMR data.

  3. Synthesis and structural characterisation using Rietveld and pair distribution function analysis of layered mixed titanium-zirconium phosphates

    International Nuclear Information System (INIS)

    Burnell, Victoria A.; Readman, Jennifer E.; Tang, Chiu C.; Parker, Julia E.; Thompson, Stephen P.; Hriljac, Joseph A.

    2010-01-01

    Crystalline metal (IV) phosphates with variable zirconium-to-titanium molar ratios of general formula (Ti 1-x Zr x )(HPO 4 ) 2 .H 2 O have been prepared by precipitation of soluble salts of the metals with phosphoric acid and heating the amorphous solids in 12 M H 3 PO 4 in an autoclave. The new materials are structurally characterised by Rietveld analysis of synchrotron X-ray powder diffraction data and pair distribution function (PDF) analysis of high energy synchrotron X-ray total scattering data. A broad range of zirconium-titanium phosphate solid solutions were formed showing isomorphous substitution of titanium by zirconium in the α-titanium phosphate lattice and vice versa for titanium substitution into the α-zirconium phosphate lattice. In both cases the solubility is partial with the coexistence of two substituted phases observed in samples with nominal compositions between the solubility limits. - Graphical abstract: Layered phosphates of general formula (Ti 1-x Zr x )(HPO 4 ).H 2 O have been prepared by the hydrothermal treatment of amorphous gels in phosphoric acid and characterised by Rietveld analysis of high resolution synchrotron X-ray powder diffraction data and pair distribution function analysis of high energy synchrotron X-ray total scattering data.

  4. Structural refinement of Nd[Fe(CN)6].4H2O and study of NdFeO3 obtained by its oxidative thermal decomposition at very low temperatures

    International Nuclear Information System (INIS)

    Navarro, M. Carolina; Pannunzio-Miner, Elisa V.; Pagola, Silvina; Gomez, M. Ines; Carbonio, Raul E.

    2005-01-01

    The crystal structure of Nd[Fe(CN) 6 ].4H 2 O has been refined by Rietveld analysis using high resolution synchrotron powder X-ray diffraction data. It belonged to the orthorhombic crystal system, Cmcm space group, with cell parameters: a=7.473952(1)A, b=12.919104(2)A and c=13.800549(2)A. The change in space group from P6 3 /m which is observed in the pentahydrates (LnFe(CN) 6 .5H 2 O) to Cmcm in the tetrahydrates has been analyzed to be a consequence of the change in 9-fold coordination of Nd 3+ in the pentahydrates to 8-fold coordination in the tetrahydrates, which changes the Nd 3+ environment from tricapped trigonal prism to a distorted tricapped trigonal prism or square antiprism. Its decomposition process in air to produce NdFeO 3 has been followed by thermogravimetric and differential thermal analysis, IR spectroscopy and laboratory powder XRD. We found that it is possible to synthesize crystalline NdFeO 3 at temperatures as low as 380 o C and refine the structure of single phase crystalline NdFeO 3 synthesized by this method at 600 deg. C

  5. Uranium refining process using ion exchange membrane

    International Nuclear Information System (INIS)

    Yamaguchi, Akira

    1977-01-01

    As for the method of refining uranium ore being carried out in Europe and America at present, uranium ore is roughly refined at the mine sites to yellow cake, then this is transported to refineries and refined by dry method. This method has the following faults, namely the number of processes is large, it requires expensive corrosion-resistant materials because of high temperature treatment, and the impurities in uranium tend to increase. On the other hand, in case of EXCER method, treatment is carried out at low temperature, and high purity uranium can be obtained, but the efficiency of electrolytic reduction process is extremely low, and economically infeasible. In the wet refining method called PNC process, uranium tetrafluoride is produced from uranium ore without making yellow cake, therefore the process is rationalized largely, and highly economical. The electrolytic reduction process in this method was developed by Asahi Chemical Industry Co., Ltd. by constructing the pilot plant in Ningyotoge Mine. The ion exchange membrane, the electrodes, and the problems concerning the process and the engineering for commercial plants were investigated. The electrolytic reduction process, the pilot plant, the development of the elements of electrolytic cells, the establishment of analytical process, the measurement of the electrolytic characteristics, the demonstration operation, and the life time of the electrolytic diaphragm are reported. (Kako, I.)

  6. Study of the crystallite size of nitrosylpentacyanoferrate through refinement of structures; Estudio del tamano de cristalita de nitrosilpentacianoferratos mediante refinamiento de estructuras

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez G, J.A.; Yee M, H.T. [ESFM-IPN, 07738 Mexico D.F. (Mexico); Balmaceda E, J. [IIM-UNAM, 04510 Mexico D.F. (Mexico); Reguera R, E. [CICATA-IPN, Av. Legaria 694, 11500 Mexico D.F. (Mexico)

    2006-07-01

    The development reached in the instrumentation and in the computer science of the diffraction of rays X, it has enlarged the reach of the method of powders considerably, in the resolution of crystalline structures of polycrystalline material converting it in a potent tool that, attended by spectroscopic techniques, it allows the fine characterization to atomic scale of having been accustomed to crystalline. In the thesis it is developed an effective methodology of determination of the crystallite size and structural refinement starting from data of diffraction of powders, based on the use of the equation of Sherrer for the estimate of the crystallite size and the method of Rietveld for the structural refinement; supplemented with the employment of the spectroscopic methods (IR and Moessbauer). The combined use of these techniques in the structural study of having been accustomed to crystalline lens of high complexity provides a novel and advanced work. The estimate of the crystallite size, it has been little explored to study accustomed to crystalline such as the pentacyanonitrosyl ferrates. One of the reasons for the which have intended to study the glass size in these structures it is due to that the molecular materials have attracted the attention of the international scientific community for their promissory properties in fields so diverse as: the absorption, desorption and separation of gases among others. Of the entreated information by means of databases and articles of scientific popularization were refined the structures of two compounds (NPCo and NPNi) obtained by powders diffraction; offering the possibility to develop a titled work: 'Physical description of the desorption of the water in nano structured material of nitrosyl penta cyano ferrates' which is carried out in parallel way to this thesis. This tools supplemented with the spectroscopic methods, potent the reach of the methods of diffraction of powders for the structural study of having

  7. Comparing Refinements for Failure and Bisimulation Semantics

    NARCIS (Netherlands)

    Eshuis, H.; Fokkinga, M.M.

    2002-01-01

    Refinement in bisimulation semantics is defined differently from refinement in failure semantics: in bisimulation semantics refinement is based on simulations between labelled transition systems, whereas in failure semantics refinement is based on inclusions between failure systems. There exist

  8. Commercial refining in the Mediterranean

    International Nuclear Information System (INIS)

    Packer, P.

    1999-01-01

    About 9% of the world's oil refining capacity is on the Mediterranean: some of the world's biggest and most advanced refineries are on Sicily and Sardinia. The Mediterranean refineries are important suppliers to southern Europe and N. Africa. The article discusses commercial refining in the Mediterranean under the headings of (i) historic development, (ii) product demand, (iii) refinery configurations, (iv) refined product trade, (v) financial performance and (vi) future outlook. Although some difficulties are foreseen, refining in the Mediterranean is likely to continue to be important well into the 21st century. (UK)

  9. Chinese refining capacity for Canadian heavy oil

    International Nuclear Information System (INIS)

    Bruce, G.W.

    2006-01-01

    This paper discussed China's refining capacity in relation to exports of Canadian heavy oil. Demand for oil is increasing throughout the world, and China is expected to consume 25 per cent of the projected yearly oil supplies. Alberta currently has an estimated 174 billion barrels of recoverable bitumen, and produces 1.06 million barrels per day. Production is expected to increase to 4.5 million barrels per day by the year 2020. Currently bitumen blends are refined and diluted with naphtha and sweet synthetic crude oil. Bitumen is a challenging feedstock for refineries, and requires thermal production methods or gasification processes. Primary conversion into sour synthetic crude is typically followed by hydrocracking and further refining into finished petroleum products. There are currently 50 refineries in China with a 7.4 million barrel per day capacity. Coastal refineries using imported crude oil have a 4 million barrel per day capacity. New facilities are being constructed and existing plants are being upgraded in order to process heavier and more sour crude oils. However, current refining capabilities in Chinese refineries have a limited ability for resid conversion. It was concluded that while China has a refining infrastructure, only refineries on the coast will use oil sands-derived feedstocks. However, there are currently opportunities to design refineries to match future feedstocks. tabs., figs

  10. Zone refining high-purity germanium

    International Nuclear Information System (INIS)

    Hubbard, G.S.; Haller, E.E.; Hansen, W.L.

    1977-10-01

    The effects of various parameters on germanium purification by zone refining have been examined. These parameters include the germanium container and container coatings, ambient gas and other operating conditions. Four methods of refining are presented which reproducibly yield 3.5 kg germanium ingots from which high purity (vertical barN/sub A/ - N/sub D/vertical bar less than or equal to2 x 10 10 cm -3 ) single crystals can be grown. A qualitative model involving binary and ternary complexes of Si, O, B, and Al is shown to account for the behavior of impurities at these low concentrations

  11. Mirror of the refined topological vertex from a matrix model

    CERN Document Server

    Eynard, B

    2011-01-01

    We find an explicit matrix model computing the refined topological vertex, starting from its representation in terms of plane partitions. We then find the spectral curve of that matrix model, and thus the mirror symmetry of the refined vertex. With the same method we also find a matrix model for the strip geometry, and we find its mirror curve. The fact that there is a matrix model shows that the refined topological string amplitudes also satisfy the remodeling the B-model construction.

  12. A refined method for the calculation of the Non-Methane Volatile Organic Compound emission estimate from Domestic Solvent Usage in Ireland from 1992 to 2014 - A case study for Ireland

    Science.gov (United States)

    Barry, Stephen; O'Regan, Bernadette

    2016-08-01

    This study describes a new methodology to calculate Non-Methane Volatile Organic Compounds from Domestic Solvent Use including Fungicides over the period 1992-2014. Improved emissions data compiled at a much more refined level can help policy-makers develop more effective policy's to address environmental issues. However, a number of problems were found when member states attempt to use national statistics for Domestic Solvent Use including Fungicides. For instance, EMEP/EEA (2013) provides no guidance regarding which activity data should be used, resulting in emission estimates being potentially inconsistent and un-comparable. Also, previous methods and emission factors described in the EMEP/EEA (2013) guidebook do not exactly match data collected by state agencies. This makes using national statistics difficult. In addition, EMEP/EEA (2013) use broader categories than necessary (e.g. Cosmetics Aerosol/Non Aerosol) to estimate emissions while activity data is available at a more refined level scale (e.g. Personal Cleaning Products, Hair Products, Cosmetics, Deodorants and Perfumes). This can make identifying the drivers of emissions unclear. This study builds upon Tzanidakis et al. (2012) whereby it provides a method for collecting activity data from state statistics, developed country specific emission factors based on a survey of 177 Irish products and importantly, used a new method to account for the volatility of organic compounds found in commonly available domestic solvent containing products. This is the first study to account for volatility based on the characteristics of organic compounds and therefore is considered a more accurate method of accounting for emissions from this emission source. The results of this study can also be used to provide a simple method for other member parties to account for the volatility of organic compounds using sectorial adjustment factors described here. For comparison purposes, emission estimates were calculated using the

  13. On Modal Refinement and Consistency

    DEFF Research Database (Denmark)

    Nyman, Ulrik; Larsen, Kim Guldstrand; Wasowski, Andrzej

    2007-01-01

    Almost 20 years after the original conception, we revisit several fundamental question about modal transition systems. First, we demonstrate the incompleteness of the standard modal refinement using a counterexample due to Hüttel. Deciding any refinement, complete with respect to the standard...

  14. Crystal structure refinement with SHELXL

    Energy Technology Data Exchange (ETDEWEB)

    Sheldrick, George M., E-mail: gsheldr@shelx.uni-ac.gwdg.de [Department of Structural Chemistry, Georg-August Universität Göttingen, Tammannstraße 4, Göttingen 37077 (Germany)

    2015-01-01

    New features added to the refinement program SHELXL since 2008 are described and explained. The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as ‘a CIF’) containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

  15. 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.

  16. Refinement of the concept of uncertainty.

    Science.gov (United States)

    Penrod, J

    2001-04-01

    To analyse the conceptual maturity of uncertainty; to develop an expanded theoretical definition of uncertainty; to advance the concept using methods of concept refinement; and to analyse congruency with the conceptualization of uncertainty presented in the theory of hope, enduring, and suffering. Uncertainty is of concern in nursing as people experience complex life events surrounding health. In an earlier nursing study that linked the concepts of hope, enduring, and suffering into a single theoretical scheme, a state best described as 'uncertainty' arose. This study was undertaken to explore how this conceptualization fit with the scientific literature on uncertainty and to refine the concept. Initially, a concept analysis using advanced methods described by Morse, Hupcey, Mitcham and colleagues was completed. The concept was determined to be partially mature. A theoretical definition was derived and techniques of concept refinement using the literature as data were applied. The refined concept was found to be congruent with the concept of uncertainty that had emerged in the model of hope, enduring and suffering. Further investigation is needed to explore the extent of probabilistic reasoning and the effects of confidence and control on feelings of uncertainty and certainty.

  17. The new insight into the structure-activity relation of Pd/CeO2-ZrO2-Nd2O3 catalysts by Raman, in situ DRIFTS and XRD Rietveld analysis.

    Science.gov (United States)

    Yang, X; Yang, L; Lin, J; Zhou, R

    2016-01-28

    Pd/CeO2-ZrO2-Nd2O3 (CZN) catalysts with different CeO2/ZrO2 molar ratios were synthesized and have been characterized by multiple techniques, e.g. XRD in combination with Rietveld refinement, UV-Raman, XPS and in situ DRIFTS. The XRD pattern of CZN with CeO2/ZrO2 molar ratios ≥1/2 can be indexed satisfactorily to the fluorite structure with a space group Fm3̄m, while the XRD patterns of CZ12 only display diffraction peaks of the tetragonal phase (S.G. P42/nmc). Nd addition can effectively stabilize the cubic structure of the CZN support and increase the enrichment of defect sites on the surface, which may be related to the better catalytic activity of Pd/CZN12 catalysts compared with Pd/CZ12. The presence of moderate ZrO2 can increase the concentration of O* active species, leading to accelerate the formation of nitrate species and thus enhance the catalytic activity of NOx and HC elimination. The Pd-dispersion decreases with the increasing Zr content, leading to the decreased CO catalytic activity, especially for the aged catalysts. The change regularity of the OSC value is almost the same with the in situ dynamic operational window, demonstrating that the in situ dynamic operational window is basically affected by the OSC value.

  18. The formation and structure of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 6.4}: XRD Rietveld, Mössabuer and XPS analyses

    Energy Technology Data Exchange (ETDEWEB)

    Al-Rawas, A.D., E-mail: arawas@squ.edu.om [Department of Physics, Sultan Qaboos University, P.O. Box 36, 123 Al-Khoud, Muscat (Oman); Widatallah, H.M.; Al-Harthi, S.H. [Department of Physics, Sultan Qaboos University, P.O. Box 36, 123 Al-Khoud, Muscat (Oman); Johnson, C. [Chemistry Department, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Gismelseed, A.M.; Elzain, M.E.; Yousif, A.A. [Department of Physics, Sultan Qaboos University, P.O. Box 36, 123 Al-Khoud, Muscat (Oman)

    2015-05-15

    Highlights: • The formation of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} is investigated. • Pre-milling the reactants substantially lowers the formation temperature. • The core and surface structures were studied. • XRD and {sup 57}Fe Mössbauer spectroscopic analyses indicate the δ-value to be 0.60. • XPS shows a complex surface structure for the mechanosynthesized Sr{sub 3}Fe{sub 2}O{sub 7−δ} nanoparticles. - Abstract: The influence of ball milling and subsequent sintering of a 3:1 molar mixture of SrCO{sub 3} and α-Fe{sub 2}O{sub 3} on the formation of Sr{sub 3}Fe{sub 2}O{sub 7−δ} double perovskite is investigated with different analytical techniques. Milling the mixture for 110 h leads to the formation of SrCO{sub 3}-α-Fe{sub 2}O{sub 3} nanocomposites and the structural deformation of α-Fe{sub 2}O{sub 3} via the incorporation of Sr{sup 2+} ions. Subsequent sintering of the pre-milled reactants’ mixture has led to the partial formation of an SrFeO{sub 3} perovskite-related phase in the temperature range 400–600 °C. This was followed by the progressive development of an Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase that continued to increase with increasing sintering temperature until a single-phased nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase was attained at 950 °C (12 h). This temperature is ∼350 °C lower than the temperature at which the material is prepared conventionally using the ceramic method. The evolution of different structural phases during the reaction process is discussed. Rietveld refinement of the X-ray diffraction data shows a value of 0.60 for the oxygen deficiency δ, in consistency with the Fe{sup 3+}/Fe{sup 4+} ratio derived from the {sup 57}Fe Mössbauer data recorded at both 300 K and 78 K. The Mössbauer data suggests that the Sr{sub 3}Fe{sub 2}O{sub 6.4} nanoparticles are superparamagnetic with blocking temperatures below 78 K. The surfaces of the Sr{sub 3}Fe{sub 2}O{sub 6

  19. Local grid refinement for free-surface flow simulations

    NARCIS (Netherlands)

    van der Plas, Peter

    2017-01-01

    The principal goal of the current study is to explore and investigate the potential of local grid refinement for increasing the numerical efficiency of free-surface flow simulations in a practical context. In this thesis we propose a method for local grid refinement in the free-surface flow model

  20. RBT—A Tool for Building Refined Buneman Trees

    DEFF Research Database (Denmark)

    Besenbacher, Søren; Mailund; Westh-Nielsen, Lasse

    2005-01-01

    We have developed a tool implementing an efficient algorithm for refined Buneman tree reconstruction. The algorithm—which has the same complexity as the neighbour-joining method and the (plain) Buneman tree construction—enables refined Buneman tree reconstruction on large taxa sets....

  1. Refinements of the attending equations for several spectral methods that provide improved quantification of B-carotene and/or lycopene in selected foods

    Science.gov (United States)

    Developing and maintaining maximal levels of carotenoids in fruits and vegetables that contain them is a concern of the produce industry. Toward this end, reliable methods for quantifying lycopene and B-carotene, two of the major health-enhancing carotenoids, are necessary. The goal of this resear...

  2. Microstructural study of Ce1-xGdxO2-δ (x = 0.1 and 0.2) nano crystallized powders synthesized by the polymeric precursor method

    International Nuclear Information System (INIS)

    Cela, B.; Macedo, D.A.; Souza, G.L.; Paskocimas, C.A.; Martinelli, A.E.; Nascimento, R.M.

    2009-01-01

    Gadolinia-doped ceria powders (Ce 1-x Gd x O 2-δ ) were prepared with substitution of 10 and 20% of the dopant element by the polymeric precursor method. This method makes possible the attainment of homogeny powder in molecular level, ideal to application in Solid Oxide Fuel Cell (SOFC) component. In this work, the particulated materials were calcinated in a range from 500 °C to 900 °C and structurally characterized by X-Ray Diffraction (XRD). The sintering behaviors of the compact samples were determined by dilatometric analyses. The results showed the method efficiency to attain monophasic nanopowder with cubic crystalline structure starting at 700 °C. The crystallite average size and crystalline parameter were determined by the Rietveld refinement method. (author)

  3. South Korea - oil refining overview

    International Nuclear Information System (INIS)

    Hayes, D.

    1999-01-01

    Following the economic problems of the 1990s, the petroleum refining industry of South Korea underwent much involuntary restructuring in 1999 with respect to takeovers and mergers and these are discussed. The demand for petroleum has now pretty well recovered. The reasons for fluctuating prices in the 1990s, how the new structure should be cushioned against changes in the future, and the potential for South Korea to export refined petroleum, are all discussed

  4. Adaptive Mesh Refinement in CTH

    International Nuclear Information System (INIS)

    Crawford, David

    1999-01-01

    This paper reports progress on implementing a new capability of adaptive mesh refinement into the Eulerian multimaterial shock- physics code CTH. The adaptivity is block-based with refinement and unrefinement occurring in an isotropic 2:1 manner. The code is designed to run on serial, multiprocessor and massive parallel platforms. An approximate factor of three in memory and performance improvements over comparable resolution non-adaptive calculations has-been demonstrated for a number of problems

  5. Steel refining possibilities in LF

    Science.gov (United States)

    Dumitru, M. G.; Ioana, A.; Constantin, N.; Ciobanu, F.; Pollifroni, M.

    2018-01-01

    This article presents the main possibilities for steel refining in Ladle Furnace (LF). These, are presented: steelmaking stages, steel refining through argon bottom stirring, online control of the bottom stirring, bottom stirring diagram during LF treatment of a heat, porous plug influence over the argon stirring, bottom stirring porous plug, analysis of porous plugs disposal on ladle bottom surface, bottom stirring simulation with ANSYS, bottom stirring simulation with Autodesk CFD.

  6. Computing Refined Buneman Trees in Cubic Time

    DEFF Research Database (Denmark)

    Brodal, G.S.; Fagerberg, R.; Östlin, A.

    2003-01-01

    Reconstructing the evolutionary tree for a set of n species based on pairwise distances between the species is a fundamental problem in bioinformatics. Neighbor joining is a popular distance based tree reconstruction method. It always proposes fully resolved binary trees despite missing evidence...... in the underlying distance data. Distance based methods based on the theory of Buneman trees and refined Buneman trees avoid this problem by only proposing evolutionary trees whose edges satisfy a number of constraints. These trees might not be fully resolved but there is strong combinatorial evidence for each...... proposed edge. The currently best algorithm for computing the refined Buneman tree from a given distance measure has a running time of O(n 5) and a space consumption of O(n 4). In this paper, we present an algorithm with running time O(n 3) and space consumption O(n 2). The improved complexity of our...

  7. Cyclic Steady State Refinement

    DEFF Research Database (Denmark)

    Bocewicz, Grzegorz; Nielsen, Peter; Banaszak, Zbigniew

    2012-01-01

    This paper deals with the problem of finding optimal feeding sequence in a manufacturing cell with feeders fed by a mobile robot with manipulation arm. The performance criterion is to minimize total traveling time of the robot in a given planning horizon. Besides, the robot has to be scheduled...... in order to keep production lines within the cell working without any shortage of parts fed from feeders. A mixed-integer programming (MIP) model is developed to find the optimal solution for the problem. In the MIP formulation, a method based on the (s, Q) inventory system is applied to define time...... windows for multiple-part feeding tasks. A case study is implemented at an impeller production line in a factory to demonstrate the result of the proposed MIP model....

  8. P-Refinement and P-Threads (Preprint)

    National Research Council Canada - National Science Library

    Dong, Steven; Karniadakis, George E

    2002-01-01

    ...]) in d dimensions, which is higher than lower-order methods. In this paper, we demonstrate that by employing multi-threading within MPI processes we manage to counter- balance the cost increase associated with P-refinement...

  9. Crystal structure refinement and microwave dielectric properties of new low dielectric loss AZrNb2O8 (A: Mn, Zn, Mg and Co) ceramics

    International Nuclear Information System (INIS)

    Ramarao, S.D.; Murthy, V.R.K.

    2013-01-01

    Graphical abstract: -- The effects of substituting different cations (Mn, Zn, Mg and Co) at the A-site of AZrNb 2 O 8 compounds on structural parameters such as packing fraction and B-site octahedral distortion were studied using X-ray powder diffraction in conjunction with Rietveld refinement. Variations in the dielectric constant (ε r ) were explained by the ionic polarizability of the compositions. The quality factor (Q × f) and temperature coefficient of resonant frequency (τ f ) were correlated with the packing fraction and B-site octahedral distortions (δ) in these compositions, respectively

  10. Romanian refining industry assesses restructuring

    International Nuclear Information System (INIS)

    Tanasescu, D.G.

    1991-01-01

    The Romanian crude oil refining industry, as all the other economic sectors, faces the problems accompanying the transition from a centrally planned economy to a market economy. At present, all refineries have registered as joint-stock companies and all are coordinated and assisted by Rafirom S.A., from both a legal and a production point of view. Rafirom S.A. is a joint-stock company that holds shares in refineries and other stock companies with activities related to oil refining. Such activities include technological research, development, design, transportation, storage, and domestic and foreign marketing. This article outlines the market forces that are expected to: drive rationalization and restructuring of refining operations and define the targets toward which the reconfigured refineries should strive

  11. Data refinement for true concurrency

    Directory of Open Access Journals (Sweden)

    Brijesh Dongol

    2013-05-01

    Full Text Available The majority of modern systems exhibit sophisticated concurrent behaviour, where several system components modify and observe the system state with fine-grained atomicity. Many systems (e.g., multi-core processors, real-time controllers also exhibit truly concurrent behaviour, where multiple events can occur simultaneously. This paper presents data refinement defined in terms of an interval-based framework, which includes high-level operators that capture non-deterministic expression evaluation. By modifying the type of an interval, our theory may be specialised to cover data refinement of both discrete and continuous systems. We present an interval-based encoding of forward simulation, then prove that our forward simulation rule is sound with respect to our data refinement definition. A number of rules for decomposing forward simulation proofs over both sequential and parallel composition are developed.

  12. A State Space Model for the Wood Chip Refining Model

    Directory of Open Access Journals (Sweden)

    David Di Ruscio

    1997-07-01

    Full Text Available A detailed dynamic model of the fibre size distribution between the refiner discs, distributed along the refiner radius, is presented. Both one- and two-dimensional descriptions for the fibre or shive geometry are given. It is shown that this model may be simplified and that analytic solutions exist under non-restrictive assumptions. A direct method for the recursive estimation of unknown parameters is presented. This method is applicable to linear or linearized systems which have a triangular structure.

  13. Formal refinement of extended state machines

    Directory of Open Access Journals (Sweden)

    Thomas Fayolle

    2016-06-01

    Full Text Available In a traditional formal development process, e.g. using the B method, the informal user requirements are (manually translated into a global abstract formal specification. This translation is especially difficult to achieve. The Event-B method was developed to incrementally and formally construct such a specification using stepwise refinement. Each increment takes into account new properties and system aspects. In this paper, we propose to couple a graphical notation called Algebraic State-Transition Diagrams (ASTD with an Event-B specification in order to provide a better understanding of the software behaviour. The dynamic behaviour is captured by the ASTD, which is based on automata and process algebra operators, while the data model is described by means of an Event-B specification. We propose a methodology to incrementally refine such specification couplings, taking into account new refinement relations and consistency conditions between the control specification and the data specification. We compare the specifications obtained using each approach for readability and proof complexity. The advantages and drawbacks of the traditional approach and of our methodology are discussed. The whole process is illustrated by a railway CBTC-like case study. Our approach is supported by tools for translating ASTD's into B and Event-B into B.

  14. Multivariate refined composite multiscale entropy analysis

    International Nuclear Information System (INIS)

    Humeau-Heurtier, Anne

    2016-01-01

    Multiscale entropy (MSE) has become a prevailing method to quantify signals complexity. MSE relies on sample entropy. However, MSE may yield imprecise complexity estimation at large scales, because sample entropy does not give precise estimation of entropy when short signals are processed. A refined composite multiscale entropy (RCMSE) has therefore recently been proposed. Nevertheless, RCMSE is for univariate signals only. The simultaneous analysis of multi-channel (multivariate) data often over-performs studies based on univariate signals. We therefore introduce an extension of RCMSE to multivariate data. Applications of multivariate RCMSE to simulated processes reveal its better performances over the standard multivariate MSE. - Highlights: • Multiscale entropy quantifies data complexity but may be inaccurate at large scale. • A refined composite multiscale entropy (RCMSE) has therefore recently been proposed. • Nevertheless, RCMSE is adapted to univariate time series only. • We herein introduce an extension of RCMSE to multivariate data. • It shows better performances than the standard multivariate multiscale entropy.

  15. Biofuels Refining Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Lobban, Lance [Univ. of Oklahoma, Norman, OK (United States)

    2017-03-28

    The goal of this project is the development of novel catalysts and knowledge of reaction pathways and mechanisms for conversion of biomass-based compounds to fuels that are compatible with oil-based fuels and with acceptable or superior fuel properties. The research scope included both catalysts to convert lignocellulosic biomass-based molecules (from pyrolysis) and vegetable oil-based molecules (i.e., triglycerides and fatty acid methyl esters). This project comprised five technical tasks. Each task is briefly introduced below, and major technical accomplishments summarized. Technical accomplishments were described in greater detail in the quarterly progress reports, and in even more detail in the >50 publications acknowledging this DoE project funding (list of publications and presentations included at the end of this report). The results of this research added greatly to the knowledge base necessary for upgrading of pyrolysis oil to hydrocarbon fuels and chemicals, and for conversion of vegetable oils to fungible diesel fuel. Numerous new catalysts and catalytic reaction systems were developed for upgrading particular compounds or compound families found in the biomass-based pyrolysis oils and vegetable oils. Methods to mitigate catalyst deactivation were investigated, including novel reaction/separation systems. Performance and emission characteristics of biofuels in flames and engines were measured. Importantly, the knowledge developed from this project became the basis for a subsequent collaborative proposal led by our research group, involving researchers from the University of Wisconsin, the University of Pittsburg, and the Idaho National Lab, for the DoE Carbon, Hydrogen and Separations Efficiency (CHASE) program, which was subsequently funded (one of only four projects awarded in the CHASE program). The CHASE project examined novel catalytic processes for lignocellulosic biomass conversion as well as technoeconomic analyses for process options for maximum

  16. Refinement of boards' role required.

    Science.gov (United States)

    Umbdenstock, R J

    1987-01-01

    The governing board's role in health care is not changing, but new competitive forces necessitate a refinement of the board's approach to fulfilling its role. In a free-standing, community, not-for-profit hospital, the board functions as though it were the "owner." Although it does not truly own the facility in the legal sense, the board does have legal, fiduciary, and financial responsibilities conferred on it by the state. In a religious-sponsored facility, the board fulfills these same obligations on behalf of the sponsoring institute, subject to the institute's reserved powers. In multi-institutional systems, the hospital board's power and authority depend on the role granted it by the system. Boards in all types of facilities are currently faced with the following challenges: Fulfilling their basic responsibilities, such as legal requirements, financial duties, and obligations for the quality of care. Encouraging management and the board itself to "think strategically" in attacking new competitive market forces while protecting the organization's traditional mission and values. Assessing recommended strategies in light of consequences if constituencies think the organization is abandoning its commitments. Boards can take several steps to match their mode of operation with the challenges of the new environment. Boards must rededicate themselves to the hospital's mission. Trustees must expand their understanding of health care trends and issues and their effect on the organization. Boards must evaluate and help strengthen management's performance, rather than acting as a "watchdog" in an adversarial position. Boards must think strategically, rather than focusing solely on operational details. Boards must evaluate the methods they use for conducting business.

  17. Structure and physical properties of the LaBiFe2O6 Perovskite produced by the modified Pechini method

    International Nuclear Information System (INIS)

    Palacio, Johny Andrés Jaramillo; Bello, Elixir William Barrera; Landínez-Téllez, David A.; Roa-Rojas, Jairo; Cagigas, Julián Andrés Munévar; Arnache, Oscar

    2017-01-01

    In this paper the synthesis of the LaBiFe 2 O 6 material by the modified Pechini method is reported. Structural, morphologic, magnetic and optic experimental studies were performed. Rietveld refinement of x-ray diffraction patterns revealed that LaBiFe 2 O 6 crystallizes in an orthorhombic perovskite structure (space group Pnma, ⧣ 62). Scanning electron microscopy images showed the nanometric feature of grains. X-ray dispersive spectroscopy permitted to infer the obtaining of the LaBiFe 2 O 6 expected stoichiometry. Results of magnetic susceptibility as a function of temperature and field magnetization evidenced mixed ferromagnetism and superparamagnetism behavior at T=300 K. Mössbauer spectroscopy supported the superparamagnetic and ferromagnetic responses as a result of the nanogranular morphology and anisotropy effects. Spectrum of diffuse reflectance suggest that this material behaves as a semiconductor with energy gap E g =2.13 eV. (author)

  18. Process for refining shale bitumen

    Energy Technology Data Exchange (ETDEWEB)

    Plauson, H

    1920-09-19

    A process is disclosed for refining shale bitumen for use as heavy mineral oil, characterized by mixtures of blown hard shale pitch and heavy mineral oil being blown with hot air at temperatures of 120 to 150/sup 0/ with 1 to 3 percent sulfur, and if necessary with 0.5 to 3 percent of an aldehyde.

  19. Panorama 2007: Refining and Petrochemicals

    International Nuclear Information System (INIS)

    Silva, C.

    2007-01-01

    The year 2005 saw a new improvement in refining margins that continued during the first three quarters of 2006. The restoration of margins in the last three years has allowed the refining sector to regain its profitability. In this context, the oil companies reported earnings for fiscal year 2005 that were up significantly compared to 2004, and the figures for the first half-year 2006 confirm this trend. Despite this favorable business environment, investments only saw a minimal increase in 2005 and the improvement expected for 2006 should remain fairly limited. Looking to 2010-2015, it would appear that the planned investment projects with the highest probability of reaching completion will be barely adequate to cover the increase in demand. Refining sector should continue to find itself under pressure. As for petrochemicals, despite a steady up-trend in the naphtha price, the restoration of margins consolidated a comeback that started in 2005. All in all, capital expenditure remained fairly low in both the refining and petrochemicals sectors, but many projects are planned for the next ten years. (author)

  20. Segmental Refinement: A Multigrid Technique for Data Locality

    KAUST Repository

    Adams, Mark F.; Brown, Jed; Knepley, Matt; Samtaney, Ravi

    2016-01-01

    We investigate a domain decomposed multigrid technique, termed segmental refinement, for solving general nonlinear elliptic boundary value problems. We extend the method first proposed in 1994 by analytically and experimentally investigating its complexity. We confirm that communication of traditional parallel multigrid is eliminated on fine grids, with modest amounts of extra work and storage, while maintaining the asymptotic exactness of full multigrid. We observe an accuracy dependence on the segmental refinement subdomain size, which was not considered in the original analysis. We present a communication complexity analysis that quantifies the communication costs ameliorated by segmental refinement and report performance results with up to 64K cores on a Cray XC30.

  1. Segmental Refinement: A Multigrid Technique for Data Locality

    KAUST Repository

    Adams, Mark F.

    2016-08-04

    We investigate a domain decomposed multigrid technique, termed segmental refinement, for solving general nonlinear elliptic boundary value problems. We extend the method first proposed in 1994 by analytically and experimentally investigating its complexity. We confirm that communication of traditional parallel multigrid is eliminated on fine grids, with modest amounts of extra work and storage, while maintaining the asymptotic exactness of full multigrid. We observe an accuracy dependence on the segmental refinement subdomain size, which was not considered in the original analysis. We present a communication complexity analysis that quantifies the communication costs ameliorated by segmental refinement and report performance results with up to 64K cores on a Cray XC30.

  2. Adaptive hybrid mesh refinement for multiphysics applications

    International Nuclear Information System (INIS)

    Khamayseh, Ahmed; Almeida, Valmor de

    2007-01-01

    The accuracy and convergence of computational solutions of mesh-based methods is strongly dependent on the quality of the mesh used. We have developed methods for optimizing meshes that are comprised of elements of arbitrary polygonal and polyhedral type. We present in this research the development of r-h hybrid adaptive meshing technology tailored to application areas relevant to multi-physics modeling and simulation. Solution-based adaptation methods are used to reposition mesh nodes (r-adaptation) or to refine the mesh cells (h-adaptation) to minimize solution error. The numerical methods perform either the r-adaptive mesh optimization or the h-adaptive mesh refinement method on the initial isotropic or anisotropic meshes to equidistribute weighted geometric and/or solution error function. We have successfully introduced r-h adaptivity to a least-squares method with spherical harmonics basis functions for the solution of the spherical shallow atmosphere model used in climate modeling. In addition, application of this technology also covers a wide range of disciplines in computational sciences, most notably, time-dependent multi-physics, multi-scale modeling and simulation

  3. Biomolecular structure refinement using the GROMOS simulation software

    International Nuclear Information System (INIS)

    Schmid, Nathan; Allison, Jane R.; Dolenc, Jožica; Eichenberger, Andreas P.; Kunz, Anna-Pitschna E.; Gunsteren, Wilfred F. van

    2011-01-01

    For the understanding of cellular processes the molecular structure of biomolecules has to be accurately determined. Initial models can be significantly improved by structure refinement techniques. Here, we present the refinement methods and analysis techniques implemented in the GROMOS software for biomolecular simulation. The methodology and some implementation details of the computation of NMR NOE data, 3 J-couplings and residual dipolar couplings, X-ray scattering intensities from crystals and solutions and neutron scattering intensities used in GROMOS is described and refinement strategies and concepts are discussed using example applications. The GROMOS software allows structure refinement combining different types of experimental data with different types of restraining functions, while using a variety of methods to enhance conformational searching and sampling and the thermodynamically calibrated GROMOS force field for biomolecular simulation.

  4. Biomolecular structure refinement using the GROMOS simulation software

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, Nathan; Allison, Jane R.; Dolenc, Jozica; Eichenberger, Andreas P.; Kunz, Anna-Pitschna E.; Gunsteren, Wilfred F. van, E-mail: wfvgn@igc.phys.chem.ethz.ch [Swiss Federal Institute of Technology ETH, Laboratory of Physical Chemistry (Switzerland)

    2011-11-15

    For the understanding of cellular processes the molecular structure of biomolecules has to be accurately determined. Initial models can be significantly improved by structure refinement techniques. Here, we present the refinement methods and analysis techniques implemented in the GROMOS software for biomolecular simulation. The methodology and some implementation details of the computation of NMR NOE data, {sup 3}J-couplings and residual dipolar couplings, X-ray scattering intensities from crystals and solutions and neutron scattering intensities used in GROMOS is described and refinement strategies and concepts are discussed using example applications. The GROMOS software allows structure refinement combining different types of experimental data with different types of restraining functions, while using a variety of methods to enhance conformational searching and sampling and the thermodynamically calibrated GROMOS force field for biomolecular simulation.

  5. Development and validation of a multiresidue method for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection.

    Science.gov (United States)

    Ramasubramanian, Thirumalaiandi; Paramasivam, Mariappan

    2016-06-01

    A multiresidue method has been developed and validated for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection. Limits of quantification of the method varied between 0.007 and 0.01 μg/g. Ethyl acetate based extraction followed by dispersive solid-phase extraction cleanup with primary secondary amine yielded internationally acceptable recoveries of acephate, chlorpyrifos, dichlorvos, monocrotophos, malathion, malaoxon, phorate, phorate-sulfoxide, phorate-oxon, phorate-sulfone, and quinalphos from selected matrices. The recoveries of target analytes from cane juice were 75.55 ± 0.5-102.57 ± 4.2, 77.45 ± 4.7-103.33 ± 3.3, and 80.55 ± 6.6-105.82 ± 9.8% at 0.01, 0.02, and 0.1 μg/g levels of fortification, respectively. The recoveries from cane sugar were 73.24 ± 3.5-104.47 ± 1.9, 75.23 ± 1.5-116.10 ± 3.7, and 70.75 ± 5.7-110.15 ± 2.7%, respectively at 0.01, 0.02, and 0.1 μg/g levels of fortification. Matrix effect and measurement uncertainty were within the permissible limit (less than 20%) as prescribed for pesticide residue analysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. European refining: evolution or revolution?

    International Nuclear Information System (INIS)

    Cuthbert, N.

    1999-01-01

    A recent detailed analysis of the refining business in Europe (by Purvin and Gurtz) was used to highlight some key issues facing the industry. The article was written under five sub-sections: (i) economic environment (assessment of the economic prospects for Europe), (ii) energy efficiency and global warming (lists the four points of the EU car makers' voluntary agreement), (iii) fuel quality and refinery investment (iv) refinery capacity and utilisation and (v) industry structure and development. Diagrams show GDP per capita for East and West, European road fuel demand to 2015 and European net trade and European refinery ownership by crude capacity. It was concluded that the future of refining in Europe is 'exciting and challenging' and there are likely to be more large joint venture refineries. (UK)

  7. On-line scheme for parameter estimation of nonlinear lithium ion battery equivalent circuit models using the simplified refined instrumental variable method for a modified Wiener continuous-time model

    International Nuclear Information System (INIS)

    Allafi, Walid; Uddin, Kotub; Zhang, Cheng; Mazuir Raja Ahsan Sha, Raja; Marco, James

    2017-01-01

    Highlights: •Off-line estimation approach for continuous-time domain for non-invertible function. •Model reformulated to multi-input-single-output; nonlinearity described by sigmoid. •Method directly estimates parameters of nonlinear ECM from the measured-data. •Iterative on-line technique leads to smoother convergence. •The model is validated off-line and on-line using NCA battery. -- Abstract: The accuracy of identifying the parameters of models describing lithium ion batteries (LIBs) in typical battery management system (BMS) applications is critical to the estimation of key states such as the state of charge (SoC) and state of health (SoH). In applications such as electric vehicles (EVs) where LIBs are subjected to highly demanding cycles of operation and varying environmental conditions leading to non-trivial interactions of ageing stress factors, this identification is more challenging. This paper proposes an algorithm that directly estimates the parameters of a nonlinear battery model from measured input and output data in the continuous time-domain. The simplified refined instrumental variable method is extended to estimate the parameters of a Wiener model where there is no requirement for the nonlinear function to be invertible. To account for nonlinear battery dynamics, in this paper, the typical linear equivalent circuit model (ECM) is enhanced by a block-oriented Wiener configuration where the nonlinear memoryless block following the typical ECM is defined to be a sigmoid static nonlinearity. The nonlinear Weiner model is reformulated in the form of a multi-input, single-output linear model. This linear form allows the parameters of the nonlinear model to be estimated using any linear estimator such as the well-established least squares (LS) algorithm. In this paper, the recursive least square (RLS) method is adopted for online parameter estimation. The approach was validated on experimental data measured from an 18650-type Graphite

  8. Uranium refining by solvent extraction

    International Nuclear Information System (INIS)

    Kraikaew, J.

    1996-01-01

    The yellow cake refining was studied in both laboratory and semi-pilot scales. The process units mainly consist of dissolution and filtration, solvent extraction, and precipitation and filtration. Effect of flow ratio (organic flow rate/ aqueous flow rate) on working efficiencies of solvent extraction process was studied. Detailed studies were carried out on extraction, scrubbing and stripping processes. Purity of yellow cake product obtained is high as 90.32% U 3 O 8

  9. Process for refining naphthalene, etc

    Energy Technology Data Exchange (ETDEWEB)

    Petroff, G

    1922-05-13

    A process is described for the refining of naphthalene, its distillates, and mineral oils by the use of dilute sulfuric acid, characterized in that the oils are oxidized with oxygen of the air and thereafter are treated with 65 to 75 percent sulfuric acid to separate the unsaturated hydrocarbons in the form of polymerized products whereby, if necessary, heating and application of usual or higher pressure can take place.

  10. Preparation of refined oils, etc

    Energy Technology Data Exchange (ETDEWEB)

    1931-02-03

    A process is disclosed for the preparation of refined sulfur-containing oils from sulfur-containing crude oils obtained by distillation of bituminous limestone, characterized by this crude oil being first subjected to a purification by distillation with steam in the known way, then treated with lime and chloride of lime and distilled preferably in the presence of zinc powder, whereby in this purification a rectification can be added for the purpose of recovering definite fractions.

  11. The Charfuel coal refining process

    International Nuclear Information System (INIS)

    Meyer, L.G.

    1991-01-01

    The patented Charfuel coal refining process employs fluidized hydrocracking to produce char and liquid products from virtually all types of volatile-containing coals, including low rank coal and lignite. It is not gasification or liquefaction which require the addition of expensive oxygen or hydrogen or the use of extreme heat or pressure. It is not the German pyrolysis process that merely 'cooks' the coal, producing coke and tar-like liquids. Rather, the Charfuel coal refining process involves thermal hydrocracking which results in the rearrangement of hydrogen within the coal molecule to produce a slate of co-products. In the Charfuel process, pulverized coal is rapidly heated in a reducing atmosphere in the presence of internally generated process hydrogen. This hydrogen rearrangement allows refinement of various ranks of coals to produce a pipeline transportable, slurry-type, environmentally clean boiler fuel and a slate of value-added traditional fuel and chemical feedstock co-products. Using coal and oxygen as the only feedstocks, the Charfuel hydrocracking technology economically removes much of the fuel nitrogen, sulfur, and potential air toxics (such as chlorine, mercury, beryllium, etc.) from the coal, resulting in a high heating value, clean burning fuel which can increase power plant efficiency while reducing operating costs. The paper describes the process, its thermal efficiency, its use in power plants, its pipeline transport, co-products, environmental and energy benefits, and economics

  12. A Macdonald refined topological vertex

    Science.gov (United States)

    Foda, Omar; Wu, Jian-Feng

    2017-07-01

    We consider the refined topological vertex of Iqbal et al (2009 J. High Energy Phys. JHEP10(2009)069), as a function of two parameters ≤ft\\lgroup x, y \\right\\rgroup , and deform it by introducing the Macdonald parameters ≤ft\\lgroup q, t \\right\\rgroup , as in the work of Vuletić on plane partitions (Vuletić M 2009 Trans. Am. Math. Soc. 361 2789-804), to obtain ‘a Macdonald refined topological vertex’. In the limit q → t , we recover the refined topological vertex of Iqbal et al and in the limit x → y , we obtain a qt-deformation of the original topological vertex of Aganagic et al (2005 Commun. Math. Phys. 25 425-78). Copies of the vertex can be glued to obtain qt-deformed 5D instanton partition functions that have well-defined 4D limits and, for generic values of ≤ft\\lgroup q, t\\right\\rgroup , contain infinite-towers of poles for every pole present in the limit q → t .

  13. Refining's-clean new jingle

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This paper reports that at a time when profit margins are slim and gasoline demand is down, the U.S. petroleum-refining industry is facing one of its greatest challenges; How to meet new federal and state laws for reformulated gasoline, oxygenated fuels, low-sulfur diesel and other measures to improve the environment. The American Petroleum Institute (API) estimates that industry will spend between $15 and $23 billion by the end of the decade to meet the U.S. Clean Air Act Amendments (CAAA) of 1990, and other legislation. ENSR Consulting and Engineering's capital-spending figure runs to between $70 and 100 billion this decade, including $24 billion to produce reformulated fuels and $10-12 billion to reduce refinery emissions. M.W. Kellogg Co. estimates that refiners may have to spend up to $30 billion this decade to meet the demand for reformulated gasoline. The estimates are wide-ranging because refiners are still studying their options and delaying final decisions as long as they can, to try to ensure they are the best and least-costly decisions. Oxygenated fuels will be required next winter, but federal regulations for reformulated gasoline won't go into effect until 1995, while California's tougher reformulated-fuels law will kick in the following year

  14. Investigation of microstructural and optical properties of La0.8Ca0.2FeO3 nanostructure synthesized via gel combustion method

    Science.gov (United States)

    Naseem, Swaleha; Ali, S. Asad; Khan, Wasi; Khan, Shakeel

    2018-05-01

    Ca substituted LaFeO3 orthoferrite nanostructure perovskite has been synthesized by gel combustion method using citric acid as a fuel. The structural and optical properties were investigated by various tools. The structural analysis through Rietveld refinement of the XRD data revealed single phase of orthorhombic structure in R-3c space group of the sample without presence of any other impurity phase. Scanning electron microscopy (SEM) image exhibits non-uniform distribution of the nanoparticles in agglomerated form. The purity of the sample and stoichiometric ratio of the elements were established through energy dispersive x-ray spectroscopy (EDS). FTIR spectroscopy measurement predicts the presence of various band relation of the chemical species of Ca with LaFeO3. Optical properties were explored through UV-visible absorption spectroscopy that showed absorption edge at 347 nm and energy band gap was estimated as 3.47eV using Tauc's relation.

  15. Synthesis of LiNi0.8Co0.1Mn0.1O2 cathode material by chloride co-precipitation method

    Institute of Scientific and Technical Information of China (English)

    李灵均; 李新海; 王志兴; 伍凌; 郑俊超; 李金辉

    2010-01-01

    LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.

  16. Southeast Asian oil markets and refining

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, N.D. [FACTS, Inc., Honolulu, Hawaii (United States)

    1999-09-01

    An overview of the Southeast Asian oil markets and refining is presented concentrating on Brunei, Malaysia, the Philippines, Singapore and Thailand refiners. Key statistics of the refiners in this region are tabulated. The demand and the quality of Indonesian, Malaysian, Philippine, Singapore and Thai petroleum products are analysed. Crude distillation unit capacity trends in the Southeastern Asian refining industry are discussed along with cracking to distillation ratios, refining in these countries, and the impact of changes in demand and refining on the product trade.

  17. Southeast Asian oil markets and refining

    International Nuclear Information System (INIS)

    Yamaguchi, N.D.

    1999-01-01

    An overview of the Southeast Asian oil markets and refining is presented concentrating on Brunei, Malaysia, the Philippines, Singapore and Thailand refiners. Key statistics of the refiners in this region are tabulated. The demand and the quality of Indonesian, Malaysian, Philippine, Singapore and Thai petroleum products are analysed. Crude distillation unit capacity trends in the Southeastern Asian refining industry are discussed along with cracking to distillation ratios, refining in these countries, and the impact of changes in demand and refining on the product trade

  18. Latin American oil markets and refining

    International Nuclear Information System (INIS)

    Yamaguchi, N.D.; Obadia, C.

    1999-01-01

    This paper provides an overview of the oil markets and refining in Argentina, Brazil, Chile, Colombia, Ecuador, Mexico, Peru and Venezuela, and examines the production of crude oil in these countries. Details are given of Latin American refiners highlighting trends in crude distillation unit capacity, cracking to distillation ratios, and refining in the different countries. Latin American oil trade is discussed, and charts are presented illustrating crude production, oil consumption, crude refining capacity, cracking to distillation ratios, and oil imports and exports

  19. Review of Grain Refinement of Cast Metals Through Inoculation: Theories and Developments

    Science.gov (United States)

    Liu, Zhilin

    2017-10-01

    The inoculation method of grain refinement is widely used in research and industry. Because of its commercial and engineering importance, extensive research on the mechanisms/theories of grain refinement and development of effective grain refiners for diverse cast metals/alloys has been conducted. In 1999, Easton and St. John reviewed the mechanisms of grain refinement of cast Al alloys. Since then, grain refinement in alloys of Al, Mg, Fe, Ti, Cu, and Zn has evolved a lot. However, there is still no full consensus on the mechanisms/theories of grain refinement. Moreover, some new grain refiners developed based on the theories do not ensure efficient grain refinement. Thus, the factors that contribute to grain refinement are still not fully understood. Clarification of the prerequisite issues that occur in grain refinement is required using recent theories. This review covers multiple metals/alloys and developments in grain refinement from the last twenty years. The characteristics of effective grain refiners are considered from four perspectives: effective particle/matrix wetting configuration, sufficiently powerful segregating elements, preferential crystallographic matching, and geometrical features of effective nucleants. Then, recent mechanisms/theories on the grain refinement of cast metals/alloys are reviewed, including the peritectic-related, hypernucleation, inert nucleant, and constitutional supercooling-driven theories. Further, developments of deterministic and probabilistic modeling and nucleation crystallography in the grain refinement of cast metals are reviewed. Finally, the latest progress in the grain refinement of cast Zn and its alloys is described, and future work on grain refinement is summarized.

  20. Grain refinement of aluminum and its alloys

    International Nuclear Information System (INIS)

    Zaid, A.I.O.

    2001-01-01

    Grain refinement of aluminum and its alloys by the binary Al-Ti and Ternary Al-Ti-B master alloys is reviewed and discussed. The importance of grain refining to the cast industry and the parameters affecting it are presented and discussed. These include parameters related to the cast, parameters related to the grain refining alloy and parameters related to the process. The different mechanisms, suggested in the literature for the process of grain refining are presented and discussed, from which it is found that although the mechanism of refining by the binary Al-Ti is well established the mechanism of grain refining by the ternary Al-Ti-B is still a controversial matter and some research work is still needed in this area. The effect of the addition of other alloying elements in the presence of the grain refiner on the grain refining efficiency is also reviewed and discussed. It is found that some elements e.g. V, Mo, C improves the grain refining efficiency, whereas other elements e.g. Cr, Zr, Ta poisons the grain refinement. Based on the parameters affecting the grain refinement and its mechanism, a criterion for selection of the optimum grain refiner is forwarded and discussed. (author)

  1. Neutron Powder Diffraction and Constrained Refinement

    DEFF Research Database (Denmark)

    Pawley, G. S.; Mackenzie, Gordon A.; Dietrich, O. W.

    1977-01-01

    The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement is...

  2. Refining Automatically Extracted Knowledge Bases Using Crowdsourcing

    Directory of Open Access Journals (Sweden)

    Chunhua Li

    2017-01-01

    Full Text Available Machine-constructed knowledge bases often contain noisy and inaccurate facts. There exists significant work in developing automated algorithms for knowledge base refinement. Automated approaches improve the quality of knowledge bases but are far from perfect. In this paper, we leverage crowdsourcing to improve the quality of automatically extracted knowledge bases. As human labelling is costly, an important research challenge is how we can use limited human resources to maximize the quality improvement for a knowledge base. To address this problem, we first introduce a concept of semantic constraints that can be used to detect potential errors and do inference among candidate facts. Then, based on semantic constraints, we propose rank-based and graph-based algorithms for crowdsourced knowledge refining, which judiciously select the most beneficial candidate facts to conduct crowdsourcing and prune unnecessary questions. Our experiments show that our method improves the quality of knowledge bases significantly and outperforms state-of-the-art automatic methods under a reasonable crowdsourcing cost.

  3. Adaptive temporal refinement in injection molding

    Science.gov (United States)

    Karyofylli, Violeta; Schmitz, Mauritius; Hopmann, Christian; Behr, Marek

    2018-05-01

    Mold filling is an injection molding stage of great significance, because many defects of the plastic components (e.g. weld lines, burrs or insufficient filling) can occur during this process step. Therefore, it plays an important role in determining the quality of the produced parts. Our goal is the temporal refinement in the vicinity of the evolving melt front, in the context of 4D simplex-type space-time grids [1, 2]. This novel discretization method has an inherent flexibility to employ completely unstructured meshes with varying levels of resolution both in spatial dimensions and in the time dimension, thus allowing the use of local time-stepping during the simulations. This can lead to a higher simulation precision, while preserving calculation efficiency. A 3D benchmark case, which concerns the filling of a plate-shaped geometry, is used for verifying our numerical approach [3]. The simulation results obtained with the fully unstructured space-time discretization are compared to those obtained with the standard space-time method and to Moldflow simulation results. This example also serves for providing reliable timing measurements and the efficiency aspects of the filling simulation of complex 3D molds while applying adaptive temporal refinement.

  4. Refining Automatically Extracted Knowledge Bases Using Crowdsourcing.

    Science.gov (United States)

    Li, Chunhua; Zhao, Pengpeng; Sheng, Victor S; Xian, Xuefeng; Wu, Jian; Cui, Zhiming

    2017-01-01

    Machine-constructed knowledge bases often contain noisy and inaccurate facts. There exists significant work in developing automated algorithms for knowledge base refinement. Automated approaches improve the quality of knowledge bases but are far from perfect. In this paper, we leverage crowdsourcing to improve the quality of automatically extracted knowledge bases. As human labelling is costly, an important research challenge is how we can use limited human resources to maximize the quality improvement for a knowledge base. To address this problem, we first introduce a concept of semantic constraints that can be used to detect potential errors and do inference among candidate facts. Then, based on semantic constraints, we propose rank-based and graph-based algorithms for crowdsourced knowledge refining, which judiciously select the most beneficial candidate facts to conduct crowdsourcing and prune unnecessary questions. Our experiments show that our method improves the quality of knowledge bases significantly and outperforms state-of-the-art automatic methods under a reasonable crowdsourcing cost.

  5. On macromolecular refinement at subatomic resolution with interatomic scatterers

    Energy Technology Data Exchange (ETDEWEB)

    Afonine, Pavel V., E-mail: pafonine@lbl.gov; Grosse-Kunstleve, Ralf W.; Adams, Paul D. [Lawrence Berkeley National Laboratory, One Cyclotron Road, BLDG 64R0121, Berkeley, CA 94720 (United States); Lunin, Vladimir Y. [Institute of Mathematical Problems of Biology, Russian Academy of Sciences, Pushchino 142290 (Russian Federation); Urzhumtsev, Alexandre [IGMBC, 1 Rue L. Fries, 67404 Illkirch and IBMC, 15 Rue R. Descartes, 67084 Strasbourg (France); Faculty of Sciences, Nancy University, 54506 Vandoeuvre-lès-Nancy (France); Lawrence Berkeley National Laboratory, One Cyclotron Road, BLDG 64R0121, Berkeley, CA 94720 (United States)

    2007-11-01

    Modelling deformation electron density using interatomic scatters is simpler than multipolar methods, produces comparable results at subatomic resolution and can easily be applied to macromolecules. A study of the accurate electron-density distribution in molecular crystals at subatomic resolution (better than ∼1.0 Å) requires more detailed models than those based on independent spherical atoms. A tool that is conventionally used in small-molecule crystallography is the multipolar model. Even at upper resolution limits of 0.8–1.0 Å, the number of experimental data is insufficient for full multipolar model refinement. As an alternative, a simpler model composed of conventional independent spherical atoms augmented by additional scatterers to model bonding effects has been proposed. Refinement of these mixed models for several benchmark data sets gave results that were comparable in quality with the results of multipolar refinement and superior to those for conventional models. Applications to several data sets of both small molecules and macromolecules are shown. These refinements were performed using the general-purpose macromolecular refinement module phenix.refine of the PHENIX package.

  6. Niobium-base grain refiner for aluminium

    International Nuclear Information System (INIS)

    Silva Pontes, P. da; Robert, M.H.; Cupini, N.L.

    1980-01-01

    A new chemical grain refiner for aluminium has been developed, using inoculation of a niobium-base compound. When a bath of molten aluminium is inoculated whith this refiner, an intermetallic aluminium-niobium compound is formed which acts as a powerful nucleant, producing extremely fine structure comparable to those obtained by means of the traditional grain refiner based on titanium and boron. It was found that the refinement of the structure depends upon the weight percentage of the new refiner inoculated as well as the time of holding the bath after inoculation and before pouring, but mainly on the inoculating temperature. (Author) [pt

  7. Structural and electrochemical characterization of calcium cobaltites (Ca{sub 3}Co{sub 4}O{sub 9}) obtained by the modified Pechini Method; Caracterizacao estrutural e eletroquimica de cobaltita de calcio (Ca{sub 3}Co{sub 4}O{sub 9}) obtida pelo Metodo Pechini modificado

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.M.; Aquino, F. de M.; Macedo, D. A. de, E-mail: rinaldo_mendesa@hotmail.com [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil)

    2016-07-01

    This work deals with the synthesis and characterization of calcium cobaltite (Ca{sub 3}Co{sub 4}O{sub 9}, C349), a p-type semiconductor with high Seebeck coefficient (S), high electrical conductivity and low thermal conductivity that has emerged as thermoelectric material. The synthesis method used to obtain the compound C349 uses commercial gelatin as complexing and polymerizing agent. The obtained material was characterized by X-ray diffraction with Rietveld refinement of the diffraction data. The results indicated that the modified Pechini method using gelatin allows to obtain powders of calcium cobaltite (with monoclinic structure) associated with a small content (2% by volume) of Co{sub 3}O{sub 4} with cubic structure. Impedance spectroscopy measurements in air indicated that the composite C349/Co{sub 3}O{sub 4} is a promising material for use as solid oxide fuel cell cathode.(author)

  8. On mesh refinement and accuracy of numerical solutions

    NARCIS (Netherlands)

    Zhou, Hong; Peters, Maria; van Oosterom, Adriaan

    1993-01-01

    This paper investigates mesh refinement and its relation with the accuracy of the boundary element method (BEM) and the finite element method (FEM). TO this end an isotropic homogeneous spherical volume conductor, for which the analytical solution is available, wag used. The numerical results

  9. Action Relations. Basic Design Concepts for Behaviour Modelling and Refinement.

    NARCIS (Netherlands)

    Quartel, Dick

    This thesis presents basic design concepts, design methods and a basic design language for distributed system behaviours. This language is based on two basic concepts: the action concept and the causality relation concept. Our methods focus on behaviour refinement, which consists of replacing an

  10. COSMOLOGICAL ADAPTIVE MESH REFINEMENT MAGNETOHYDRODYNAMICS WITH ENZO

    International Nuclear Information System (INIS)

    Collins, David C.; Xu Hao; Norman, Michael L.; Li Hui; Li Shengtai

    2010-01-01

    In this work, we present EnzoMHD, the extension of the cosmological code Enzo to include the effects of magnetic fields through the ideal magnetohydrodynamics approximation. We use a higher order Godunov method for the computation of interface fluxes. We use two constrained transport methods to compute the electric field from those interface fluxes, which simultaneously advances the induction equation and maintains the divergence of the magnetic field. A second-order divergence-free reconstruction technique is used to interpolate the magnetic fields in the block-structured adaptive mesh refinement framework already extant in Enzo. This reconstruction also preserves the divergence of the magnetic field to machine precision. We use operator splitting to include gravity and cosmological expansion. We then present a series of cosmological and non-cosmological test problems to demonstrate the quality of solution resulting from this combination of solvers.

  11. Materials refining on the Moon

    Science.gov (United States)

    Landis, Geoffrey A.

    2007-05-01

    Oxygen, metals, silicon, and glass are raw materials that will be required for long-term habitation and production of structural materials and solar arrays on the Moon. A process sequence is proposed for refining these materials from lunar regolith, consisting of separating the required materials from lunar rock with fluorine. The fluorine is brought to the Moon in the form of potassium fluoride, and is liberated from the salt by electrolysis in a eutectic salt melt. Tetrafluorosilane produced by this process is reduced to silicon by a plasma reduction stage; the fluorine salts are reduced to metals by reaction with metallic potassium. Fluorine is recovered from residual MgF and CaF2 by reaction with K2O.

  12. Adaptive mesh refinement in titanium

    Energy Technology Data Exchange (ETDEWEB)

    Colella, Phillip; Wen, Tong

    2005-01-21

    In this paper, we evaluate Titanium's usability as a high-level parallel programming language through a case study, where we implement a subset of Chombo's functionality in Titanium. Chombo is a software package applying the Adaptive Mesh Refinement methodology to numerical Partial Differential Equations at the production level. In Chombo, the library approach is used to parallel programming (C++ and Fortran, with MPI), whereas Titanium is a Java dialect designed for high-performance scientific computing. The performance of our implementation is studied and compared with that of Chombo in solving Poisson's equation based on two grid configurations from a real application. Also provided are the counts of lines of code from both sides.

  13. Refining shale-oil distillates

    Energy Technology Data Exchange (ETDEWEB)

    Altpeter, J

    1952-03-17

    A process is described for refining distillates from shale oil, brown coal, tar, and other tar products by extraction with selective solvents, such as lower alcohols, halogen-hydrins, dichlorodiethyl ether, liquid sulfur dioxide, and so forth, as well as treating with alkali solution, characterized in that the distillate is first treated with completely or almost completely recovered phenol or cresotate solution, the oil is separated from the phenolate with solvent, for example concentrated or adjusted to a determined water content of lower alcohol, furfural, halogen-hydrin, dichlorodiethyl ether, liquid sulfur dioxide, or the like, extracted, and the raffinate separated from the extract layer, if necessary after distillation or washing out of solvent, and freeing with alkali solution from residual phenol or creosol.

  14. Bayesian ensemble refinement by replica simulations and reweighting

    Science.gov (United States)

    Hummer, Gerhard; Köfinger, Jürgen

    2015-12-01

    We describe different Bayesian ensemble refinement methods, examine their interrelation, and discuss their practical application. With ensemble refinement, the properties of dynamic and partially disordered (bio)molecular structures can be characterized by integrating a wide range of experimental data, including measurements of ensemble-averaged observables. We start from a Bayesian formulation in which the posterior is a functional that ranks different configuration space distributions. By maximizing this posterior, we derive an optimal Bayesian ensemble distribution. For discrete configurations, this optimal distribution is identical to that obtained by the maximum entropy "ensemble refinement of SAXS" (EROS) formulation. Bayesian replica ensemble refinement enhances the sampling of relevant configurations by imposing restraints on averages of observables in coupled replica molecular dynamics simulations. We show that the strength of the restraints should scale linearly with the number of replicas to ensure convergence to the optimal Bayesian result in the limit of infinitely many replicas. In the "Bayesian inference of ensembles" method, we combine the replica and EROS approaches to accelerate the convergence. An adaptive algorithm can be used to sample directly from the optimal ensemble, without replicas. We discuss the incorporation of single-molecule measurements and dynamic observables such as relaxation parameters. The theoretical analysis of different Bayesian ensemble refinement approaches provides a basis for practical applications and a starting point for further investigations.

  15. Refining Grasp Affordance Models by Experience

    DEFF Research Database (Denmark)

    Detry, Renaud; Kraft, Dirk; Buch, Anders Glent

    2010-01-01

    We present a method for learning object grasp affordance models in 3D from experience, and demonstrate its applicability through extensive testing and evaluation on a realistic and largely autonomous platform. Grasp affordance refers here to relative object-gripper configurations that yield stable...... with a visual model of the object they characterize. We explore a batch-oriented, experience-based learning paradigm where grasps sampled randomly from a density are performed, and an importance-sampling algorithm learns a refined density from the outcomes of these experiences. The first such learning cycle...... is bootstrapped with a grasp density formed from visual cues. We show that the robot effectively applies its experience by downweighting poor grasp solutions, which results in increased success rates at subsequent learning cycles. We also present success rates in a practical scenario where a robot needs...

  16. Grain refinement of AZ31 by (SiC)P: Theoretical calculation and experiment

    International Nuclear Information System (INIS)

    Guenther, R.; Hartig, Ch.; Bormann, R.

    2006-01-01

    Grain refinement of gravity die-cast Mg-alloys can be achieved via two methods: in situ refinement by primary precipitated metallic or intermetallic phases, and inoculation of the melt via ceramic particles that remain stable in the melt due to their high thermodynamic stability. In order to clarify grain refinement mechanisms and optimize possible potent refiners in Mg-alloys, a simulation method for heterogeneous nucleation based on a free growth model has been developed. It allows the prediction of the grain size as a function of the particle size distribution, the volumetric content of ceramic inoculants, the cooling rate and the alloy constitution. The model assumptions were examined experimentally by a study of the grain refinement of (SiC) P in AZ31. Additions of (SiC) P result in significant grain refinement, if appropriate parameters for ceramic particles are chosen. The model makes quantitatively correct predictions for the grain size and its variation with cooling rate

  17. Refined geometric transition and qq-characters

    Science.gov (United States)

    Kimura, Taro; Mori, Hironori; Sugimoto, Yuji

    2018-01-01

    We show the refinement of the prescription for the geometric transition in the refined topological string theory and, as its application, discuss a possibility to describe qq-characters from the string theory point of view. Though the suggested way to operate the refined geometric transition has passed through several checks, it is additionally found in this paper that the presence of the preferred direction brings a nontrivial effect. We provide the modified formula involving this point. We then apply our prescription of the refined geometric transition to proposing the stringy description of doubly quantized Seiberg-Witten curves called qq-characters in certain cases.

  18. 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

  19. Automated knowledge-base refinement

    Science.gov (United States)

    Mooney, Raymond J.

    1994-01-01

    Over the last several years, we have developed several systems for automatically refining incomplete and incorrect knowledge bases. These systems are given an imperfect rule base and a set of training examples and minimally modify the knowledge base to make it consistent with the examples. One of our most recent systems, FORTE, revises first-order Horn-clause knowledge bases. This system can be viewed as automatically debugging Prolog programs based on examples of correct and incorrect I/O pairs. In fact, we have already used the system to debug simple Prolog programs written by students in a programming language course. FORTE has also been used to automatically induce and revise qualitative models of several continuous dynamic devices from qualitative behavior traces. For example, it has been used to induce and revise a qualitative model of a portion of the Reaction Control System (RCS) of the NASA Space Shuttle. By fitting a correct model of this portion of the RCS to simulated qualitative data from a faulty system, FORTE was also able to correctly diagnose simple faults in this system.

  20. 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)

  1. Numerical solution of plasma fluid equations using locally refined grids

    International Nuclear Information System (INIS)

    Colella, P.

    1997-01-01

    This paper describes a numerical method for the solution of plasma fluid equations on block-structured, locally refined grids. The plasma under consideration is typical of those used for the processing of semiconductors. The governing equations consist of a drift-diffusion model of the electrons and an isothermal model of the ions coupled by Poisson's equation. A discretization of the equations is given for a uniform spatial grid, and a time-split integration scheme is developed. The algorithm is then extended to accommodate locally refined grids. This extension involves the advancement of the discrete system on a hierarchy of levels, each of which represents a degree of refinement, together with synchronization steps to ensure consistency across levels. A brief discussion of a software implementation is followed by a presentation of numerical results

  2. Investigation of the influence of Ceratophyllum demersum to refine ...

    African Journals Online (AJOL)

    Water pollution has always been a major problem in the environment. Polluted water is harming for human health and need to clean water from pollution factors. One of the economic and rapid methods for elements removal is displacement metals by biosorption. The purpose of this study was refining diluted compost latex ...

  3. Refined functional relations for the elliptic SOS model

    Energy Technology Data Exchange (ETDEWEB)

    Galleas, W., E-mail: w.galleas@uu.nl [ARC Centre of Excellence for the Mathematics and Statistics of Complex Systems, University of Melbourne, VIC 3010 (Australia)

    2013-02-21

    In this work we refine the method presented in Galleas (2012) [1] and obtain a novel kind of functional equation determining the partition function of the elliptic SOS model with domain wall boundaries. This functional relation arises from the dynamical Yang-Baxter relation and its solution is given in terms of multiple contour integrals.

  4. Applicability of refined Born approximation to non-linear equations

    International Nuclear Information System (INIS)

    Rayski, J.

    1990-01-01

    A computational method called ''Refined Born Approximation'', formerly applied exclusively to linear problems, is shown to be successfully applicable also to non-linear problems enabling me to compute bifurcations and other irregular solutions which cannot be obtained by the standard perturbation procedures. (author)

  5. An approach of requirements tracing in formal refinement

    DEFF Research Database (Denmark)

    Jastram, Michael; Hallerstede, Stefan; Leuschel, Michael

    2010-01-01

    Formal modeling of computing systems yields models that are intended to be correct with respect to the requirements that have been formalized. The complexity of typical computing systems can be addressed by formal refinement introducing all the necessary details piecemeal. We report on preliminar...... changes, making use of corresponding techniques already built into the Event-B method....

  6. Refined functional relations for the elliptic SOS model

    International Nuclear Information System (INIS)

    Galleas, W.

    2013-01-01

    In this work we refine the method presented in Galleas (2012) [1] and obtain a novel kind of functional equation determining the partition function of the elliptic SOS model with domain wall boundaries. This functional relation arises from the dynamical Yang–Baxter relation and its solution is given in terms of multiple contour integrals.

  7. Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

    International Nuclear Information System (INIS)

    Conconi, M.S.; Gauna, M.R.; Serra, M.F.; Suarez, G.; Aglietti, E.F.; Rendtorff, N.M.

    2014-01-01

    The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

  8. Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

    Energy Technology Data Exchange (ETDEWEB)

    Conconi, M.S.; Gauna, M.R.; Serra, M.F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC), Buenos Aires (Argentina); Suarez, G.; Aglietti, E.F.; Rendtorff, N.M., E-mail: rendtorff@cetmic.unlp.edu.ar [Universidad Nacional de La Plata (UNLP), Buenos Aires (Argentina). Fac. de Ciencias Exactas. Dept. de Quimica

    2014-10-15

    The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

  9. Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

    Directory of Open Access Journals (Sweden)

    M. S. Conconi

    2014-12-01

    Full Text Available The firing transformations of traditional (clay based ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite, the low crystalline (metakaolinite and/or spinel type pre-mullite and glassy phases evolution of a triaxial (clay-quartz-feldspar ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and

  10. Refinement Checking on Parametric Modal Transition Systems

    DEFF Research Database (Denmark)

    Benes, Nikola; Kretínsky, Jan; Larsen, Kim Guldstrand

    2015-01-01

    Modal transition systems (MTS) is a well-studied specification formalism of reactive systems supporting a step-wise refinement methodology. Despite its many advantages, the formalism as well as its currently known extensions are incapable of expressing some practically needed aspects in the refin...

  11. Comparing Syntactic and Semantics Action Refinement

    NARCIS (Netherlands)

    Goltz, Ursula; Gorrieri, Roberto; Rensink, Arend

    The semantic definition of action refinement on labelled configuration structures is compared with the notion of syntactic substitution, which can be used as another notion of action refinement in a process algebraic setting. The comparison is done by studying a process algebra equipped with

  12. On Syntactic and Semantic Action Refinement

    NARCIS (Netherlands)

    Hagiya, M.; Goltz, U.; Mitchell, J.C.; Gorrieri, R.; Rensink, Arend

    1994-01-01

    The semantic definition of action refinement on labelled event structures is compared with the notion of syntactic substitution, which can be used as another notion of action refinement in a process algebraic setting. This is done by studying a process algebra equipped with the ACP sequential

  13. Anomalies in the refinement of isoleucine

    Energy Technology Data Exchange (ETDEWEB)

    Berntsen, Karen R. M.; Vriend, Gert, E-mail: gerrit.vriend@radboudumc.nl [Radboud University Medical Center, Geert Grooteplein 26-28, 6525 GA Nijmegen (Netherlands)

    2014-04-01

    The side-chain torsion angles of isoleucines in X-ray protein structures are a function of resolution, secondary structure and refinement software. Detailing the standard torsion angles used in refinement software can improve protein structure refinement. A study of isoleucines in protein structures solved using X-ray crystallography revealed a series of systematic trends for the two side-chain torsion angles χ{sub 1} and χ{sub 2} dependent on the resolution, secondary structure and refinement software used. The average torsion angles for the nine rotamers were similar in high-resolution structures solved using either the REFMAC, CNS or PHENIX software. However, at low resolution these programs often refine towards somewhat different χ{sub 1} and χ{sub 2} values. Small systematic differences can be observed between refinement software that uses molecular dynamics-type energy terms (for example CNS) and software that does not use these terms (for example REFMAC). Detailing the standard torsion angles used in refinement software can improve the refinement of protein structures. The target values in the molecular dynamics-type energy functions can also be improved.

  14. Refined large N duality for knots

    DEFF Research Database (Denmark)

    Kameyama, Masaya; Nawata, Satoshi

    We formulate large N duality of U(N) refined Chern-Simons theory with a torus knot/link in S³. By studying refined BPS states in M-theory, we provide the explicit form of low-energy effective actions of Type IIA string theory with D4-branes on the Ω-background. This form enables us to relate...

  15. Anomalies in the refinement of isoleucine

    International Nuclear Information System (INIS)

    Berntsen, Karen R. M.; Vriend, Gert

    2014-01-01

    The side-chain torsion angles of isoleucines in X-ray protein structures are a function of resolution, secondary structure and refinement software. Detailing the standard torsion angles used in refinement software can improve protein structure refinement. A study of isoleucines in protein structures solved using X-ray crystallography revealed a series of systematic trends for the two side-chain torsion angles χ 1 and χ 2 dependent on the resolution, secondary structure and refinement software used. The average torsion angles for the nine rotamers were similar in high-resolution structures solved using either the REFMAC, CNS or PHENIX software. However, at low resolution these programs often refine towards somewhat different χ 1 and χ 2 values. Small systematic differences can be observed between refinement software that uses molecular dynamics-type energy terms (for example CNS) and software that does not use these terms (for example REFMAC). Detailing the standard torsion angles used in refinement software can improve the refinement of protein structures. The target values in the molecular dynamics-type energy functions can also be improved

  16. Grain refinement of zinc-aluminium alloys

    International Nuclear Information System (INIS)

    Zaid, A.I.O.

    2006-01-01

    It is now well-established that the structure of the zinc-aluminum die casting alloys can be modified by the binary Al-Ti or the ternary Al-Ti-B master alloys. in this paper, grain refinement of zinc-aluminum alloys by rare earth materials is reviewed and discussed. The importance of grain refining of these alloys and parameters affecting it are presented and discussed. These include parameters related to the Zn-Al alloys cast, parameters related to the grain refining elements or alloys and parameters related to the process. The effect of addition of other alloying elements e.g. Zr either alone or in the presence of the main grain refiners Ti or Ti + B on the grain refining efficiency is also reviewed and discussed. Furthermore, based on the grain refinement and the parameters affecting it, a criterion for selection of the optimum grain refiner is suggested. Finally, the recent research work on the effect of grain refiners on the mechanical behaviour, impact strength, wear resistance, and fatigue life of these alloys are presented and discussed. (author)

  17. Refined Phenotyping of Modic Changes

    Science.gov (United States)

    Määttä, Juhani H.; Karppinen, Jaro; Paananen, Markus; Bow, Cora; Luk, Keith D.K.; Cheung, Kenneth M.C.; Samartzis, Dino

    2016-01-01

    Abstract Low back pain (LBP) is the world's most disabling condition. Modic changes (MC) are vertebral bone marrow changes adjacent to the endplates as noted on magnetic resonance imaging. The associations of specific MC types and patterns with prolonged, severe LBP and disability remain speculative. This study assessed the relationship of prolonged, severe LBP and back-related disability, with the presence and morphology of lumbar MC in a large cross-sectional population-based study of Southern Chinese. We addressed the topographical and morphological dimensions of MC along with other magnetic resonance imaging phenotypes (eg, disc degeneration and displacement) on the basis of axial T1 and sagittal T2-weighted imaging of L1-S1. Prolonged severe LBP was defined as LBP lasting ≥30 days during the past year, and a visual analog scale severest pain intensity of at least 6/10. An Oswestry Disability Index score of 15% was regarded as significant disability. We also assessed subject demographics, occupation, and lifestyle factors. In total, 1142 subjects (63% females, mean age 53 years) were assessed. Of these, 282 (24.7%) had MC (7.1% type I, 17.6% type II). MC subjects were older (P = 0.003), had more frequent disc displacements (P disability. The strength of the associations increased with the number of MC. This large-scale study is the first to definitively note MC types and specific morphologies to be independently associated with prolonged severe LBP and back-related disability. This proposed refined MC phenotype may have direct implications in clinical decision-making as to the development and management of LBP. Understanding of these imaging biomarkers can lead to new preventative and personalized therapeutics related to LBP. PMID:27258491

  18. North Dakota Refining Capacity Study

    Energy Technology Data Exchange (ETDEWEB)

    Dennis Hill; Kurt Swenson; Carl Tuura; Jim Simon; Robert Vermette; Gilberto Marcha; Steve Kelly; David Wells; Ed Palmer; Kuo Yu; Tram Nguyen; Juliam Migliavacca

    2011-01-05

    According to a 2008 report issued by the United States Geological Survey, North Dakota and Montana have an estimated 3.0 to 4.3 billion barrels of undiscovered, technically recoverable oil in an area known as the Bakken Formation. With the size and remoteness of the discovery, the question became 'can a business case be made for increasing refining capacity in North Dakota?' And, if so what is the impact to existing players in the region. To answer the question, a study committee comprised of leaders in the region's petroleum industry were brought together to define the scope of the study, hire a consulting firm and oversee the study. The study committee met frequently to provide input on the findings and modify the course of the study, as needed. The study concluded that the Petroleum Area Defense District II (PADD II) has an oversupply of gasoline. With that in mind, a niche market, naphtha, was identified. Naphtha is used as a diluent used for pipelining the bitumen (heavy crude) from Canada to crude markets. The study predicted there will continue to be an increase in the demand for naphtha through 2030. The study estimated the optimal configuration for the refinery at 34,000 barrels per day (BPD) producing 15,000 BPD of naphtha and a 52 percent refinery charge for jet and diesel yield. The financial modeling assumed the sponsor of a refinery would invest its own capital to pay for construction costs. With this assumption, the internal rate of return is 9.2 percent which is not sufficient to attract traditional investment given the risk factor of the project. With that in mind, those interested in pursuing this niche market will need to identify incentives to improve the rate of return.

  19. Uranium refining by solvent extraction

    International Nuclear Information System (INIS)

    Kraikaew, J.; Srinuttrakul, W.

    2014-01-01

    The solvent extraction process to produce higher purity uranium from yellowcake was studied in laboratory scale. Yellowcake, which the uranium purity is around 70% and the main impurity is thorium, was obtained from monazite processing pilot plant of Rare Earth Research and Development Center in Thailand. For uranium re-extraction process, the extractant chosen was Tributylphosphate (TBP) in kerosene. It was found that the optimum concentration of TBP was 10% in kerosene and the optimum nitric acid concentration in uranyl nitrate feed solution was 4 N. An increase in concentrations of uranium and thorium in feed solution resulted in a decrease in the distribution of both components in the extractant. However, the distribution of uranium into the extractant was found to be more than that of thorium. The equilibration study of the extraction system, UO_2(NO_3)/4N HNO_3 – 10%TBP/Kerosene, was also investigated. Two extraction stages were calculated graphically from 100,000 ppm uranium concentration in feed solution input with 90% extraction efficiency and the flow ratio of aqueous phase to organic phase was adjusted to 1.0. For thorium impurity scrubbing process, 10% TBP in kerosene was loaded with uranium and minor thorium from uranyl nitrate solution prepared from yellowcake and was scrubbed with different low concentration nitric acid. The results showed that at nitric acid normality was lower than 1 N, uranium distributed well to aqueous phase. As conclusion, optimum nitric acid concentration for scrubbing process should not less than 1 N and diluted nitric acid or de-ionized water should be applied to strip uranium from organic phase in the final refining process. (author)

  20. Production of Al-Ti-C grain refiners with the addition of elemental carbon

    International Nuclear Information System (INIS)

    Gezer, Berke Turgay; Toptan, Fatih; Daglilar, Sibel; Kerti, Isil

    2010-01-01

    Grain refining process used in aluminium alloys, has an important role for preventing columnar, coarse grains and encouraging fine, equiaxed grain formation. Al-Ti-B grain refiners are widely used as aluminium grain refiners despite the problems in application Al-Ti-C refiners have an increasing demand in recent years. In the present work, Al-Ti-C grain refiners with different Ti:C ratios were produced by insitu method with the addition of elemental carbon. Microstructures were characterised by optic microscope and scanning electron microscope equipped with energy dispersive spectroscopy. The effects of temperature, holding time and Ti:C ratio on the grain refinement process were investigated and optimum conditions were determined.

  1. Linear Prediction Using Refined Autocorrelation Function

    Directory of Open Access Journals (Sweden)

    M. Shahidur Rahman

    2007-07-01

    Full Text Available This paper proposes a new technique for improving the performance of linear prediction analysis by utilizing a refined version of the autocorrelation function. Problems in analyzing voiced speech using linear prediction occur often due to the harmonic structure of the excitation source, which causes the autocorrelation function to be an aliased version of that of the vocal tract impulse response. To estimate the vocal tract characteristics accurately, however, the effect of aliasing must be eliminated. In this paper, we employ homomorphic deconvolution technique in the autocorrelation domain to eliminate the aliasing effect occurred due to periodicity. The resulted autocorrelation function of the vocal tract impulse response is found to produce significant improvement in estimating formant frequencies. The accuracy of formant estimation is verified on synthetic vowels for a wide range of pitch frequencies typical for male and female speakers. The validity of the proposed method is also illustrated by inspecting the spectral envelopes of natural speech spoken by high-pitched female speaker. The synthesis filter obtained by the current method is guaranteed to be stable, which makes the method superior to many of its alternatives.

  2. The use of Fourier reverse transforms in crystallographic phase refinement

    Energy Technology Data Exchange (ETDEWEB)

    Ringrose, Sharon [Iowa State Univ., Ames, IA (United States)

    1997-10-08

    Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.

  3. Segmental Refinement: A Multigrid Technique for Data Locality

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Mark [Columbia Univ., New York, NY (United States). Applied Physics and Applied Mathematics Dept.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2014-10-27

    We investigate a technique - segmental refinement (SR) - proposed by Brandt in the 1970s as a low memory multigrid method. The technique is attractive for modern computer architectures because it provides high data locality, minimizes network communication, is amenable to loop fusion, and is naturally highly parallel and asynchronous. The network communication minimization property was recognized by Brandt and Diskin in 1994; we continue this work by developing a segmental refinement method for a finite volume discretization of the 3D Laplacian on massively parallel computers. An understanding of the asymptotic complexities, required to maintain textbook multigrid efficiency, are explored experimentally with a simple SR method. A two-level memory model is developed to compare the asymptotic communication complexity of a proposed SR method with traditional parallel multigrid. Performance and scalability are evaluated with a Cray XC30 with up to 64K cores. We achieve modest improvement in scalability from traditional parallel multigrid with a simple SR implementation.

  4. Mesh Generation via Local Bisection Refinement of Triangulated Grids

    Science.gov (United States)

    2015-06-01

    Science and Technology Organisation DSTO–TR–3095 ABSTRACT This report provides a comprehensive implementation of an unstructured mesh generation method...and Technology Organisation 506 Lorimer St, Fishermans Bend, Victoria 3207, Australia Telephone: 1300 333 362 Facsimile: (03) 9626 7999 c© Commonwealth...their behaviour is critically linked to Maubach’s method and the data structures N and T . The top- level mesh refinement algorithm is also presented

  5. Action Relations. Basic Design Concepts for Behaviour Modelling and Refinement.

    OpenAIRE

    Quartel, Dick

    1998-01-01

    This thesis presents basic design concepts, design methods and a basic design language for distributed system behaviours. This language is based on two basic concepts: the action concept and the causality relation concept. Our methods focus on behaviour refinement, which consists of replacing an abstract behaviour by a more concrete behaviour, such that the concrete behaviour conforms to the abstract behaviour. An important idea underlying this thesis is that an effective design methodology s...

  6. Optimizing refiner operation with statistical modelling

    Energy Technology Data Exchange (ETDEWEB)

    Broderick, G [Noranda Research Centre, Pointe Claire, PQ (Canada)

    1997-02-01

    The impact of refining conditions on the energy efficiency of the process and on the handsheet quality of a chemi-mechanical pulp was studied as part of a series of pilot scale refining trials. Statistical models of refiner performance were constructed from these results and non-linear optimization of process conditions were conducted. Optimization results indicated that increasing the ratio of specific energy applied in the first stage led to a reduction of some 15 per cent in the total energy requirement. The strategy can also be used to obtain significant increases in pulp quality for a given energy input. 20 refs., 6 tabs.

  7. Refinement Types for TypeScript

    OpenAIRE

    Vekris, Panagiotis; Cosman, Benjamin; Jhala, Ranjit

    2016-01-01

    We present Refined TypeScript (RSC), a lightweight refinement type system for TypeScript, that enables static verification of higher-order, imperative programs. We develop a formal core of RSC that delineates the interaction between refinement types and mutability. Next, we extend the core to account for the imperative and dynamic features of TypeScript. Finally, we evaluate RSC on a set of real world benchmarks, including parts of the Octane benchmarks, D3, Transducers, and the TypeScript co...

  8. Price implications for Russia's oil refining

    International Nuclear Information System (INIS)

    Khartukov, Eugene M.

    1998-01-01

    Over the past several years, Russia's oil industry has undergone its radical transformation from a wholly state-run and generously subsidized oil distribution system toward a substantially privatized, cash-strapped, and quasi-market ''petropreneurship''. This fully applies to the industry's downstream sector. Still unlike more dynamic E and C operations, the country's refining has turned out better fenced off competitive market forces and is less capable to respond to market imperatives. Consequently, jammed between depressed product prices and persistent feedstock costs, Russian refiners were badly hit by the world oil glut - which has made a radical modernization of the obsolete refining sector clearly a must. (author)

  9. (Na,□)5[MnO2]13 nanorods: a new tunnel structure for electrode materials determined ab initio and refined through a combination of electron and synchrotron diffraction data

    Science.gov (United States)

    Mugnaioli, Enrico; Gemmi, Mauro; Merlini, Marco; Gregorkiewitz, Michele

    2016-01-01

    (Nax□1 − x)5[MnO2]13 has been synthesized with x = 0.80 (4), corresponding to Na0.31[MnO2]. This well known material is usually cited as Na0.4[MnO2] and is believed to have a romanèchite-like framework. Here, its true structure is determined, ab initio, by single-crystal electron diffraction tomography (EDT) and refined both by EDT data applying dynamical scattering theory and by the Rietveld method based on synchrotron powder diffraction data (χ2 = 0.690, R wp = 0.051, R p = 0.037, R F2 = 0.035). The unit cell is monoclinic C2/m, a = 22.5199 (6), b = 2.83987 (6), c = 14.8815 (4) Å, β = 105.0925 (16)°, V = 918.90 (4) Å3, Z = 2. A hitherto unknown [MnO2] framework is found, which is mainly based on edge- and corner-sharing octahedra and comprises three types of tunnels: per unit cell, two are defined by S-shaped 10-rings, four by egg-shaped 8-rings, and two by slightly oval 6-rings of Mn polyhedra. Na occupies all tunnels. The so-determined structure excellently explains previous reports on the electrochemistry of (Na,□)5[MnO2]13. The trivalent Mn3+ ions concentrate at two of the seven Mn sites where larger Mn—O distances and Jahn–Teller distortion are observed. One of the Mn3+ sites is five-coordinated in a square pyramid which, on oxidation to Mn4+, may easily undergo topotactic transformation to an octahedron suggesting a possible pathway for the transition among different tunnel structures. PMID:27910840

  10. Refinement for Transition Systems with Responses

    Directory of Open Access Journals (Sweden)

    Marco Carbone

    2012-07-01

    Full Text Available Motivated by the response pattern for property specifications and applications within flexible workflow management systems, we report upon an initial study of modal and mixed transition systems in which the must transitions are interpreted as must eventually, and in which implementations can contain may behaviors that are resolved at run-time. We propose Transition Systems with Responses (TSRs as a suitable model for this study. We prove that TSRs correspond to a restricted class of mixed transition systems, which we refer to as the action-deterministic mixed transition systems. We show that TSRs allow for a natural definition of deadlocked and accepting states. We then transfer the standard definition of refinement for mixed transition systems to TSRs and prove that refinement does not preserve deadlock freedom. This leads to the proposal of safe refinements, which are those that preserve deadlock freedom. We exemplify the use of TSRs and (safe refinements on a small medication workflow.

  11. Taiwan: refined need for consuming population

    International Nuclear Information System (INIS)

    Hayes, David.

    1995-01-01

    A brief discussion is given of the oil and gas industry in Taiwan. Topics covered include the possibility of privatization, refineries and refining contracts overseas, plans for a new petrochemical complex and an offshore submarine transmission pipeline. (UK)

  12. 1991 worldwide refining and gas processing directory

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    This book ia an authority for immediate information on the industry. You can use it to find new business, analyze market trends, and to stay in touch with existing contacts while making new ones. The possibilities for business applications are numerous. Arranged by country, all listings in the directory include address, phone, fax and telex numbers, a description of the company's activities, names of key personnel and their titles, corporate headquarters, branch offices and plant sites. This newly revised edition lists more than 2000 companies and nearly 3000 branch offices and plant locations. This east-to-use reference also includes several of the most vital and informative surveys of the industry, including the U.S. Refining Survey, the Worldwide Construction Survey in Refining, Sulfur, Gas Processing and Related Fuels, the Worldwide Refining and Gas Processing Survey, the Worldwide Catalyst Report, and the U.S. and Canadian Lube and Wax Capacities Report from the National Petroleum Refiner's Association

  13. Development of a Refined Staff Group Trainer

    National Research Council Canada - National Science Library

    Quensel, Susan

    1999-01-01

    .... As a follow-on effort to the previous SGT project, the goal was to refine a brigade-level staff training program to more effectively and efficiently coordinate the activities within and between the...

  14. Refining borders of genome-rearrangements including repetitions

    Directory of Open Access Journals (Sweden)

    JA Arjona-Medina

    2016-10-01

    Full Text Available Abstract Background DNA rearrangement events have been widely studied in comparative genomic for many years. The importance of these events resides not only in the study about relatedness among different species, but also to determine the mechanisms behind evolution. Although there are many methods to identify genome-rearrangements (GR, the refinement of their borders has become a huge challenge. Until now no accepted method exists to achieve accurate fine-tuning: i.e. the notion of breakpoint (BP is still an open issue, and despite repeated regions are vital to understand evolution they are not taken into account in most of the GR detection and refinement methods. Methods and results We propose a method to refine the borders of GR including repeated regions. Instead of removing these repetitions to facilitate computation, we take advantage of them using a consensus alignment sequence of the repeated region in between two blocks. Using the concept of identity vectors for Synteny Blocks (SB and repetitions, a Finite State Machine is designed to detect transition points in the difference between such vectors. The method does not force the BP to be a region or a point but depends on the alignment transitions within the SBs and repetitions. Conclusion The accurate definition of the borders of SB and repeated genomic regions and consequently the detection of BP might help to understand the evolutionary model of species. In this manuscript we present a new proposal for such a refinement. Features of the SBs borders and BPs are different and fit with what is expected. SBs with more diversity in annotations and BPs short and richer in DNA replication and stress response, which are strongly linked with rearrangements.

  15. Macromolecular refinement by model morphing using non-atomic parameterizations.

    Science.gov (United States)

    Cowtan, Kevin; Agirre, Jon

    2018-02-01

    Refinement is a critical step in the determination of a model which explains the crystallographic observations and thus best accounts for the missing phase components. The scattering density is usually described in terms of atomic parameters; however, in macromolecular crystallography the resolution of the data is generally insufficient to determine the values of these parameters for individual atoms. Stereochemical and geometric restraints are used to provide additional information, but produce interrelationships between parameters which slow convergence, resulting in longer refinement times. An alternative approach is proposed in which parameters are not attached to atoms, but to regions of the electron-density map. These parameters can move the density or change the local temperature factor to better explain the structure factors. Varying the size of the region which determines the parameters at a particular position in the map allows the method to be applied at different resolutions without the use of restraints. Potential applications include initial refinement of molecular-replacement models with domain motions, and potentially the use of electron density from other sources such as electron cryo-microscopy (cryo-EM) as the refinement model.

  16. Synthesis of hydroxyapatite and structural refinement by X-ray diffraction

    International Nuclear Information System (INIS)

    Araujo, Jorge Correa de

    2007-01-01

    A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effects with an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals. (author)

  17. Discontinuous Galerkin discretization and hp-refinement for the resolution of the neutron transport equation

    International Nuclear Information System (INIS)

    Fournier, Damien; Le-Tellier, Romain; Herbin, Raphaele

    2013-01-01

    This paper presents an hp-refinement method for a first order scalar transport reaction equation discretized by a discontinuous Galerkin method. First, the theoretical rates of convergence of h- and p-refinement are recalled and numerically tested. Then, in order to design some meshes, we propose two different estimators of the local error on the spatial domain. These quantities are analyzed and compared depending on the regularity of the solution so as to find the best way to lead the refinement process and the best strategy to choose between h- and p-refinement. Finally, the different possible refinement strategies are compared first on analytical examples and then on realistic applications for neutron transport in a nuclear reactor core. (authors)

  18. Oil refining in South Asia and Australasia

    International Nuclear Information System (INIS)

    Yamaguchi, N.D.

    2000-01-01

    An overview of the oil markets of Southeast Asia and Australasia is presented focussing on oil refining. Key statistics of both areas are tabulated, and figures providing information on GDP/capita, crude production, comparison of demand barrels, and product demand are provided. Crude oil production and supply, oil product demand, and the refining industries are examined with details given of evolution of capacity and cracking to distillation ratios

  19. The present state of refining in France

    International Nuclear Information System (INIS)

    1996-01-01

    The european refining industry suffers from a production over-capacity and closures are inevitable; the situation is even worse in France due to the imbalance between gas oil and gasoline prices and the weak margin for distributors. The French refining industry is however an important and essential link for its strategic fuel and petroleum product supply, and represent 17000 jobs. Several measures are introduced by the French Industry department towards restructuring, capacity reduction and fuel price harmonization

  20. Iron insertion and hematite segregation on Fe-doped TiO2 nanoparticles obtained from sol-gel and hydrothermal methods.

    Science.gov (United States)

    Santos, Reginaldo da S; Faria, Guilherme A; Giles, Carlos; Leite, Carlos A P; Barbosa, Herbert de S; Arruda, Marco A Z; Longo, Claudia

    2012-10-24

    Iron-doped TiO(2) (Fe:TiO(2)) nanoparticles were synthesized by the sol-gel method (with Fe/Ti molar ratio corresponding to 1, 3, and 5%), followed by hydrothermal treatment, drying, and annealing. A similar methodology was used to synthesize TiO(2) and α-Fe(2)O(3) nanoparticles. For comparison, a mixture hematite/titania, with Fe/Ti = 4% was also investigated. Characterization of the samples using Rietveld refinement of X-ray diffraction data revealed that TiO(2) consisted of 82% anatase and 18% brookite; for Fe:TiO(2), brookite increased to 30% and hematite was also identified (0.5, 1.0, and 1.2 wt % for samples prepared with 1, 3, and 5% of Fe/Ti). For hematite/titania mixture, Fe/Ti was estimated as 4.4%, indicating the Rietveld method reliability for estimation of phase composition. Because the band gap energy, estimated as 3.2 eV for TiO(2), gradually ranged from 3.0 to 2.7 eV with increasing Fe content at Fe:TiO(2), it can be assumed that a Fe fraction was also inserted as dopant in the TiO(2) lattice. Extended X-ray absorption fine structure spectra obtained for the Ti K-edge and Fe K-edge indicated that absorbing Fe occupied a Ti site in the TiO(2) lattice, but hematite features were not observed. Hematite particles also could not be identified in the images obtained by transmission electron microscopy, in spite of iron identification by elemental mapping, suggesting that hematite can be segregated at the grain boundaries of Fe:TiO(2).

  1. Design of Grain Refiners for Aluminium Alloys

    Science.gov (United States)

    Tronche, A.; Greer, A. L.

    The efficiency of a grain refiner can be quantified as the number of grains per nucleant particle in the solidified product. Even for effective refiners in aluminium, such as Al-5Ti-1B, it is known from experiments that efficiencies are very low, at best 10-3 to 102. It is of interest to explore the reasons for such low values, and to assess the prospects for increased efficiency though design of refiners. Recently it has been shown [1] that a simple recalescence-based model can make quantitative predictions of grain size as a function of refiner addition level, cooling rate and solute content. In the model, the initiation of grains is limited by the free growth from nucleant particles, the size distribution of which is very important. The present work uses this model as the basis for discussing the effect of particle size distribution on grain refiner performance. Larger particles (of TiB2 in the case of present interest) promote greater efficiency, as do narrower size distributions. It is shown that even if the size distribution could be exactly specified, compromises would have to be made to balance efficiency (defined as above) with other desirable characteristics of a refiner.

  2. Petroleum refining and air quality

    International Nuclear Information System (INIS)

    Raimbault, C.

    1992-01-01

    This paper studies the methods which may be developed in petroleum refineries or during petroleum products using for air pollution abatement: petroleum products desulfurization, lead elimination in gasoline and catalytic converters to reduce sulfur dioxide and nitrogen oxides in exhaust gases. Investments and costs estimation to adapt petroleum refineries for environment protection is also given. 1 ref., 6 figs., 6 tabs

  3. Unit-cell refinement from powder diffraction scans

    International Nuclear Information System (INIS)

    Pawley, G.S.

    1981-01-01

    A procedure for the refinement of the crystal unit cell from a powder diffraction scan is presented. In this procedure knowledge of the crystal structure is not required, and at the end of the refinement a list of indexed intensities is produced. This list may well be usable as the starting point for the application of direct methods. The problems of least-squares ill-conditioning due to overlapping reflections are overcome by constraints. An example using decafluorocyclohexene, C 6 F 10 , shows the quality of fit obtained in a case which may even be a false minimum. The method should become more relevant as powder scans of improved resolution become available, through the use of pulsed neutron sources. (Auth.)

  4. Hirshfeld atom refinement for modelling strong hydrogen bonds.

    Science.gov (United States)

    Woińska, Magdalena; Jayatilaka, Dylan; Spackman, Mark A; Edwards, Alison J; Dominiak, Paulina M; Woźniak, Krzysztof; Nishibori, Eiji; Sugimoto, Kunihisa; Grabowsky, Simon

    2014-09-01

    High-resolution low-temperature synchrotron X-ray diffraction data of the salt L-phenylalaninium hydrogen maleate are used to test the new automated iterative Hirshfeld atom refinement (HAR) procedure for the modelling of strong hydrogen bonds. The HAR models used present the first examples of Z' > 1 treatments in the framework of wavefunction-based refinement methods. L-Phenylalaninium hydrogen maleate exhibits several hydrogen bonds in its crystal structure, of which the shortest and the most challenging to model is the O-H...O intramolecular hydrogen bond present in the hydrogen maleate anion (O...O distance is about 2.41 Å). In particular, the reconstruction of the electron density in the hydrogen maleate moiety and the determination of hydrogen-atom properties [positions, bond distances and anisotropic displacement parameters (ADPs)] are the focus of the study. For comparison to the HAR results, different spherical (independent atom model, IAM) and aspherical (free multipole model, MM; transferable aspherical atom model, TAAM) X-ray refinement techniques as well as results from a low-temperature neutron-diffraction experiment are employed. Hydrogen-atom ADPs are furthermore compared to those derived from a TLS/rigid-body (SHADE) treatment of the X-ray structures. The reference neutron-diffraction experiment reveals a truly symmetric hydrogen bond in the hydrogen maleate anion. Only with HAR is it possible to freely refine hydrogen-atom positions and ADPs from the X-ray data, which leads to the best electron-density model and the closest agreement with the structural parameters derived from the neutron-diffraction experiment, e.g. the symmetric hydrogen position can be reproduced. The multipole-based refinement techniques (MM and TAAM) yield slightly asymmetric positions, whereas the IAM yields a significantly asymmetric position.

  5. Protein Structure Refinement by Optimization

    DEFF Research Database (Denmark)

    Carlsen, Martin

    on whether the three-dimensional structure of a homologous sequence is known. Whether or not a protein model can be used for industrial purposes depends on the quality of the predicted structure. A model can be used to design a drug when the quality is high. The overall goal of this project is to assess...... that correlates maximally to a native-decoy distance. The main contribution of this thesis is methods developed for analyzing the performance of metrically trained knowledge-based potentials and for optimizing their performance while making them less dependent on the decoy set used to define them. We focus...... being at-least a local minimum of the potential. To address how far the current functional form of the potential is from an ideal potential we present two methods for finding the optimal metrically trained potential that simultaneous has a number of native structures as a local minimum. Our results...

  6. Aplicación de tratamiento electroquímico a baja intensidad de corriente para la extracción de cloruros en objetos arqueológicos de hierro de procedencia subacuática. Observación de la evolución de fases mineralógicas mediante XRD-Rietveld

    Directory of Open Access Journals (Sweden)

    Bethencourt, M.

    2004-12-01

    Full Text Available With the purpose of optimising a suitable methodology for the conservation of an archaeological object of iron, a low current intensities electrolytic treatment has been applied, to a piece of cast iron, proving to be effective in the extraction of chloride ions from the structure of akaganeite, principal corrosion product of iron in the marine medium. The monitoring of the electrolytic treatment has been proven by applying the "Rietveld" method to the patterns XRD of samples extracted from the corroded surface before and after the treatment. This method has permitted the unequivocal determination of the akaganeite and its chemical composition. This identification has been corroborated by means of SEM and EDS. After the electrolytic treatment, akaganeite was not present in the sample.

    Con objeto de optimizar una metodología adecuada para la conservación de una pieza de hierro arqueológico de fundición, se ha aplicado un tratamiento electrolítico a bajas intensidades de corriente, demostrando su efectividad en la extracción de iones cloruro de la estructura de akaganeita, principal producto de corrosión del hierro en medio marino. La monitorización del proceso se ha comprobado aplicando el método Rietveld a los patrones XRD de muestras extraídas de la superficie corroída antes y después del tratamiento. Este método ha permitido la determinación inequívoca de la akaganeita y la composición química de este oxihidróxido de hierro no estequiométrico. Dicha identificación se corrobora mediante SEM y EDS. Después del tratamiento electrolítico la akaganeita no está presente en la muestra.

  7. Nonobtuse local tetrahedral refinements towards a polygonal face/interface

    Czech Academy of Sciences Publication Activity Database

    Korotov, S.; Křížek, Michal

    2011-01-01

    Roč. 24, č. 6 (2011), s. 817-821 ISSN 0893-9659 R&D Projects: GA AV ČR(CZ) IAA100190803 Institutional research plan: CEZ:AV0Z10190503 Keywords : finite element method * nonobtuse tetrahedron * local refinement * discrete maximum principle * boundary and interior layers * interface problem Subject RIV: BA - General Mathematics Impact factor: 1.371, year: 2011 http://www.sciencedirect.com/science/article/pii/S0893965910004726

  8. Refining of yellow cake by solvent extraction. Pakistan status report

    International Nuclear Information System (INIS)

    Yunus, M.; Muzaffar, A.; Qureshi, M.T.; Qazi, N.K.; Khan, J.R.; Chughtai, N.A.; Zaidi, S.M.H.

    1980-01-01

    The paper describes the pilot-plant studies made at the Pakistan Institute of Nuclear Science and Technology, Rawalpindi, on refining yellow cake. The process units mainly consist of digestion and filtration, solvent extraction, precipitation and filtration, and calcining and reduction. Extraction parameters, such as free acidity in terms of nitrate ion concentration, throughputs and AF index, have been studied in some detail. Product of satisfactory chemical purity, as confirmed by spectrochemical analysis, was produced by this method. (author)

  9. Dynamic grid refinement for partial differential equations on parallel computers

    International Nuclear Information System (INIS)

    Mccormick, S.; Quinlan, D.

    1989-01-01

    The fast adaptive composite grid method (FAC) is an algorithm that uses various levels of uniform grids to provide adaptive resolution and fast solution of PDEs. An asynchronous version of FAC, called AFAC, that completely eliminates the bottleneck to parallelism is presented. This paper describes the advantage that this algorithm has in adaptive refinement for moving singularities on multiprocessor computers. This work is applicable to the parallel solution of two- and three-dimensional shock tracking problems. 6 refs

  10. Refining a brief decision aid in stable CAD: cognitive interviews

    OpenAIRE

    Kelly-Blake, Karen; Clark, Stacie; Dontje, Katherine; Olomu, Adesuwa; Henry, Rebecca C; Rovner, David R; Rothert, Marilyn L; Holmes-Rovner, Margaret

    2014-01-01

    Background We describe the results of cognitive interviews to refine the “Making Choices©” Decision Aid (DA) for shared decision-making (SDM) about stress testing in patients with stable coronary artery disease (CAD). Methods We conducted a systematic development process to design a DA consistent with International Patient Decision Aid Standards (IPDAS) focused on Alpha testing criteria. Cognitive interviews were conducted with ten stable CAD patients using the “think aloud” interview techniq...

  11. Accurate macromolecular crystallographic refinement: incorporation of the linear scaling, semiempirical quantum-mechanics program DivCon into the PHENIX refinement package

    Energy Technology Data Exchange (ETDEWEB)

    Borbulevych, Oleg Y.; Plumley, Joshua A.; Martin, Roger I. [QuantumBio Inc., 2790 West College Avenue, State College, PA 16801 (United States); Merz, Kenneth M. Jr [University of Florida, Gainesville, Florida (United States); Westerhoff, Lance M., E-mail: lance@quantumbioinc.com [QuantumBio Inc., 2790 West College Avenue, State College, PA 16801 (United States)

    2014-05-01

    Semiempirical quantum-chemical X-ray macromolecular refinement using the program DivCon integrated with PHENIX is described. Macromolecular crystallographic refinement relies on sometimes dubious stereochemical restraints and rudimentary energy functionals to ensure the correct geometry of the model of the macromolecule and any covalently bound ligand(s). The ligand stereochemical restraint file (CIF) requires a priori understanding of the ligand geometry within the active site, and creation of the CIF is often an error-prone process owing to the great variety of potential ligand chemistry and structure. Stereochemical restraints have been replaced with more robust functionals through the integration of the linear-scaling, semiempirical quantum-mechanics (SE-QM) program DivCon with the PHENIX X-ray refinement engine. The PHENIX/DivCon package has been thoroughly validated on a population of 50 protein–ligand Protein Data Bank (PDB) structures with a range of resolutions and chemistry. The PDB structures used for the validation were originally refined utilizing various refinement packages and were published within the past five years. PHENIX/DivCon does not utilize CIF(s), link restraints and other parameters for refinement and hence it does not make as many a priori assumptions about the model. Across the entire population, the method results in reasonable ligand geometries and low ligand strains, even when the original refinement exhibited difficulties, indicating that PHENIX/DivCon is applicable to both single-structure and high-throughput crystallography.

  12. i3Drefine software for protein 3D structure refinement and its assessment in CASP10.

    Science.gov (United States)

    Bhattacharya, Debswapna; Cheng, Jianlin

    2013-01-01

    Protein structure refinement refers to the process of improving the qualities of protein structures during structure modeling processes to bring them closer to their native states. Structure refinement has been drawing increasing attention in the community-wide Critical Assessment of techniques for Protein Structure prediction (CASP) experiments since its addition in 8(th) CASP experiment. During the 9(th) and recently concluded 10(th) CASP experiments, a consistent growth in number of refinement targets and participating groups has been witnessed. Yet, protein structure refinement still remains a largely unsolved problem with majority of participating groups in CASP refinement category failed to consistently improve the quality of structures issued for refinement. In order to alleviate this need, we developed a completely automated and computationally efficient protein 3D structure refinement method, i3Drefine, based on an iterative and highly convergent energy minimization algorithm with a powerful all-atom composite physics and knowledge-based force fields and hydrogen bonding (HB) network optimization technique. In the recent community-wide blind experiment, CASP10, i3Drefine (as 'MULTICOM-CONSTRUCT') was ranked as the best method in the server section as per the official assessment of CASP10 experiment. Here we provide the community with free access to i3Drefine software and systematically analyse the performance of i3Drefine in strict blind mode on the refinement targets issued in CASP10 refinement category and compare with other state-of-the-art refinement methods participating in CASP10. Our analysis demonstrates that i3Drefine is only fully-automated server participating in CASP10 exhibiting consistent improvement over the initial structures in both global and local structural quality metrics. Executable version of i3Drefine is freely available at http://protein.rnet.missouri.edu/i3drefine/.

  13. i3Drefine Software for Protein 3D Structure Refinement and Its Assessment in CASP10

    Science.gov (United States)

    Bhattacharya, Debswapna; Cheng, Jianlin

    2013-01-01

    Protein structure refinement refers to the process of improving the qualities of protein structures during structure modeling processes to bring them closer to their native states. Structure refinement has been drawing increasing attention in the community-wide Critical Assessment of techniques for Protein Structure prediction (CASP) experiments since its addition in 8th CASP experiment. During the 9th and recently concluded 10th CASP experiments, a consistent growth in number of refinement targets and participating groups has been witnessed. Yet, protein structure refinement still remains a largely unsolved problem with majority of participating groups in CASP refinement category failed to consistently improve the quality of structures issued for refinement. In order to alleviate this need, we developed a completely automated and computationally efficient protein 3D structure refinement method, i3Drefine, based on an iterative and highly convergent energy minimization algorithm with a powerful all-atom composite physics and knowledge-based force fields and hydrogen bonding (HB) network optimization technique. In the recent community-wide blind experiment, CASP10, i3Drefine (as ‘MULTICOM-CONSTRUCT’) was ranked as the best method in the server section as per the official assessment of CASP10 experiment. Here we provide the community with free access to i3Drefine software and systematically analyse the performance of i3Drefine in strict blind mode on the refinement targets issued in CASP10 refinement category and compare with other state-of-the-art refinement methods participating in CASP10. Our analysis demonstrates that i3Drefine is only fully-automated server participating in CASP10 exhibiting consistent improvement over the initial structures in both global and local structural quality metrics. Executable version of i3Drefine is freely available at http://protein.rnet.missouri.edu/i3drefine/. PMID:23894517

  14. Verifying large modular systems using iterative abstraction refinement

    International Nuclear Information System (INIS)

    Lahtinen, Jussi; Kuismin, Tuomas; Heljanko, Keijo

    2015-01-01

    Digital instrumentation and control (I&C) systems are increasingly used in the nuclear engineering domain. The exhaustive verification of these systems is challenging, and the usual verification methods such as testing and simulation are typically insufficient. Model checking is a formal method that is able to exhaustively analyse the behaviour of a model against a formally written specification. If the model checking tool detects a violation of the specification, it will give out a counter-example that demonstrates how the specification is violated in the system. Unfortunately, sometimes real life system designs are too big to be directly analysed by traditional model checking techniques. We have developed an iterative technique for model checking large modular systems. The technique uses abstraction based over-approximations of the model behaviour, combined with iterative refinement. The main contribution of the work is the concrete abstraction refinement technique based on the modular structure of the model, the dependency graph of the model, and a refinement sampling heuristic similar to delta debugging. The technique is geared towards proving properties, and outperforms BDD-based model checking, the k-induction technique, and the property directed reachability algorithm (PDR) in our experiments. - Highlights: • We have developed an iterative technique for model checking large modular systems. • The technique uses BDD-based model checking, k-induction, and PDR in parallel. • We have tested our algorithm by verifying two models with it. • The technique outperforms classical model checking methods in our experiments

  15. The evolution of oil refining in Europe

    Energy Technology Data Exchange (ETDEWEB)

    Reid, A. [CONCAWE, Brussels (Belgium)

    2013-04-01

    Back in 1963 when CONCAWE was founded, the world looked very different from what it is today, and so did the global and European refining industry. Oil product markets were expanding fast and new refineries were being built at a steady rate. The oil crisis of the 1970s brought an abrupt end to this, heralding a long era of consolidation and stepwise adaptation. At the same time the nature of the global oil business shifted from fully integrated companies producing, transporting and refining their own oil to a much more diversified situation where oil production ('upstream') and refining/distribution ('downstream') gradually became two essentially separate businesses. From being purely a 'cost centre' in an integrated chain, refining has become a separate activity in its own right, operating as a 'profit centre' between two global markets - crude oil and products - which, although not entirely independent, have their own dynamics and influences. In addition demand gradually shifted towards lighter products while the quality requirements on all products were considerably tightened. This article explores the new challenges that these changes have imposed on EU refiners, and describes CONCAWE's contributions to understanding their impact on refinery production and investments.

  16. Grain refinement mechanism in A3003 alloy

    International Nuclear Information System (INIS)

    Cho, Hoon; Shin, Je-Sik; Lee, Byoung-Soo; Jo, Hyung-Ho

    2009-01-01

    In the present study, in order to find out an grain refinement mechanism, 0.1wt.% Al-10wt.%Ti master alloy was added into A3003 alloy melt contained in graphite crucible and in alumina crucible, and then the melt holding time at 750 deg. C was systematically changed from 1 min up to 120 min. It is interesting to note that the grain refinement and fading phenomena remarkably depend on the crucible material. The fading effect in the specimens using alumina crucible can be explained as the result of TiAl 3 phase dissolution into molten aluminium matrix. In the specimens using graphite crucible, the grain refinement was occurred gradually with increasing holding time. It was suggest that the continuous grain refinement is due to transition of refinement mechanism from TiAl 3 phase to TiC phase. It can be mentioned that the TiC formed from titanium and carbon solute in the aluminium melt, which came from the Al-10Ti alloy and the graphite crucible.

  17. Decadal climate prediction with a refined anomaly initialisation approach

    Science.gov (United States)

    Volpi, Danila; Guemas, Virginie; Doblas-Reyes, Francisco J.; Hawkins, Ed; Nichols, Nancy K.

    2017-03-01

    In decadal prediction, the objective is to exploit both the sources of predictability from the external radiative forcings and from the internal variability to provide the best possible climate information for the next decade. Predicting the climate system internal variability relies on initialising the climate model from observational estimates. We present a refined method of anomaly initialisation (AI) applied to the ocean and sea ice components of the global climate forecast model EC-Earth, with the following key innovations: (1) the use of a weight applied to the observed anomalies, in order to avoid the risk of introducing anomalies recorded in the observed climate, whose amplitude does not fit in the range of the internal variability generated by the model; (2) the AI of the ocean density, instead of calculating it from the anomaly initialised state of temperature and salinity. An experiment initialised with this refined AI method has been compared with a full field and standard AI experiment. Results show that the use of such refinements enhances the surface temperature skill over part of the North and South Atlantic, part of the South Pacific and the Mediterranean Sea for the first forecast year. However, part of such improvement is lost in the following forecast years. For the tropical Pacific surface temperature, the full field initialised experiment performs the best. The prediction of the Arctic sea-ice volume is improved by the refined AI method for the first three forecast years and the skill of the Atlantic multidecadal oscillation is significantly increased compared to a non-initialised forecast, along the whole forecast time.

  18. Effect of grain refinement on the fluidity of two commercial Al-Si foundry alloys

    Science.gov (United States)

    Dahle, A. K.; Tøndel, P. A.; Paradies, C. J.; Arnberg, L.

    1996-08-01

    The effect of grain refinement on the fluidity of AlSi7Mg and AlSi11Mg has been investigated by spiral tests. Two different types of grain refiners have been evaluated. An AlTi5Bl master alloy was added to different Ti contents. Since the commercial alloys had a high initial content of titanium, model alloys were made to investigate the fluidity at low grain refiner additions. Commercial alloys grain refined only by boron additions have also been investigated. The results from the fluidity measurements have been verified by measuring the dendrite coherency point of the different cast alloys. Although different, the two methods show similar trends. The spirals from each fraction grain refiner cast were subsequently investigated metallographically at the tip of the spirals and at a reference point a distance behind, but no obvious difference in structure was observed. For both alloys, an increase in fluidity is observed as the content of grain refiner increases above 0.12 pct Ti, while the fluidity is impaired with increased grain refinement below 0.12 pct Ti. The alloys grain refined with ~0.015 pct B show the highest fraction solid at dendrite coherency, the smallest grain size, and the best fluidity.

  19. ESTUDIO DE LAS FASES MINERALÓGICAS DEL CLÍNKER EN UNA CEMENTERA ESPAÑOLA, UTILIZANDO EL MÉTODO DE RIETVELD

    Directory of Open Access Journals (Sweden)

    ANA M. CASTAÑÓN

    2012-01-01

    Full Text Available Con el objetivo de implantar un método de control de calidad de forma continua en una fábrica de cementos española, para mejorar las características del producto final, se están desarrollando nuevas metodologías de caracterización. El método de Rietveld [1] se ha utilizado con éxito para analizar la composición de las fases principales del clínker. Utilizando esta metodología, se ha llevado a cabo un estudio para cuantificar adecuadamente la fase minoritaria de Cal Libre, de gran importancia en la calidad del clínker. El método ha permitido obtener unos resultados satisfactorios en muestras cuyos contenidos superan el 3% de CaO. Estos resultados son posibles combinando adecuadamente las técnicas de difracción y fluorescencia de rayos-X, así como los resultados del análisis por vía química.

  20. India's refining prospects linked to economic growth

    International Nuclear Information System (INIS)

    Lewis, E.

    1996-01-01

    International investors assess refining ventures in India the same way they do comparable projects elsewhere in the world: according to their expectations about investment returns. By that standard, India's appeal is mixed, although its need for some measure of additional refining capacity seems certain. The success of future refinery investments will depend heavily on the government's commitment to policies allowing the economy to grow faster than the population. Unless accompanied by economic growth, expected increases in the population will not automatically raise demand for petroleum products. Decisions about investments in India's refining sector, therefore, must carefully weigh market fundamentals, the business environment, and likely investment performance. This paper reviews the market for the various products and predicts new economic trends

  1. Refining processes of selected copper alloys

    Directory of Open Access Journals (Sweden)

    S. Rzadkosz

    2009-04-01

    Full Text Available The analysis of the refining effectiveness of the liquid copper and selected copper alloys by various micro additions and special refiningsubstances – was performed. Examinations of an influence of purifying, modifying and deoxidation operations performed in a metal bath on the properties of certain selected alloys based on copper matrix - were made. Refining substances, protecting-purifying slag, deoxidation and modifying substances containing micro additions of such elements as: zirconium, boron, phosphor, sodium, lithium, or their compounds introduced in order to change micro structures and properties of alloys, were applied in examinations. A special attention was directed to macro and micro structures of alloys, their tensile and elongation strength and hot-cracks sensitivity. Refining effects were estimated by comparing the effectiveness of micro structure changes with property changes of copper and its selected alloys from the group of tin bronzes.

  2. CONSTRAINED-TRANSPORT MAGNETOHYDRODYNAMICS WITH ADAPTIVE MESH REFINEMENT IN CHARM

    International Nuclear Information System (INIS)

    Miniati, Francesco; Martin, Daniel F.

    2011-01-01

    We present the implementation of a three-dimensional, second-order accurate Godunov-type algorithm for magnetohydrodynamics (MHD) in the adaptive-mesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit corner-transport-upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the piecewise-parabolic method (PPM), while the magnetic field variables are face-centered and are evolved through application of the Stokes theorem on cell edges via a constrained-transport (CT) method. The so-called multidimensional MHD source terms required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracy or robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These include face-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. The code is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests, a three-dimensional shock-cloud interaction problem, and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence is shown to remain negligible throughout.

  3. Decontamination of steel by melt refining: A literature review

    International Nuclear Information System (INIS)

    Ozturk, B.; Fruehan, R.J.

    1994-01-01

    It has been reported that a large amount of metal waste is produced annually by nuclear fuel processing and nuclear power plants. These metal wastes are contaminated with radioactive elements, such as uranium and plutonium. Current Department of Energy guidelines require retrievable storage of all metallic wastes containing transuranic elements above a certain level. Because of high cost, it is important to develop an effective decontamination and volume reduction method for low level contaminated metals. It has been shown by some investigators that a melt refining technique can be used for the processing of the contaminated metal wastes. In this process, contaminated metal is melted wit a suitable flux. The radioactive elements are oxidized and transferred to a slag phase. In order to develop a commercial process it is important to have information on the thermodynamics and kinetics of the removal. Therefore, a literature search was carried out to evaluate the available information on the decontamination uranium and transuranic-contaminated plain steel, copper and stainless steel by melt a refining technique. Emphasis was given to the thermodynamics and kinetics of the removal. Data published in the literature indicate that it is possible to reduce the concentration of radioactive elements to a very low level by the melt refining method. 20 refs

  4. Adaptive mesh refinement for storm surge

    KAUST Repository

    Mandli, Kyle T.; Dawson, Clint N.

    2014-01-01

    An approach to utilizing adaptive mesh refinement algorithms for storm surge modeling is proposed. Currently numerical models exist that can resolve the details of coastal regions but are often too costly to be run in an ensemble forecasting framework without significant computing resources. The application of adaptive mesh refinement algorithms substantially lowers the computational cost of a storm surge model run while retaining much of the desired coastal resolution. The approach presented is implemented in the GeoClaw framework and compared to ADCIRC for Hurricane Ike along with observed tide gauge data and the computational cost of each model run. © 2014 Elsevier Ltd.

  5. Refining - Panorama 2008; Raffinage - Panorama 2008

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-07-01

    Investment rallied in 2007, and many distillation and conversion projects likely to reach the industrial stage were announced. With economic growth sustained in 2006 and still pronounced in 2007, oil demand remained strong - especially in emerging countries - and refining margins stayed high. Despite these favorable business conditions, tensions persisted in the refining sector, which has fallen far behind in terms of investing in refinery capacity. It will take renewed efforts over a long period to catch up. Looking at recent events that have affected the economy in many countries (e.g. the sub-prime crisis), prudence remains advisable.

  6. India beckons participants in burgeoning refining sector

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This paper reports that India has opened its refining sector to full private investment for the first time in more than 2 decades. The government again gave a green light to construction of three 120,000 b/d grassroots refineries in East, West, and Central India. The projects had won various governmental approvals in the past few years, but never moved off high center for a variety of economic and regulatory reasons. The difference this time is that the government is offering interests in the projects to private foreign and domestic investors. It's part of India's push to boost overall refining capacity by more than 80% this century

  7. Adaptive mesh refinement for storm surge

    KAUST Repository

    Mandli, Kyle T.

    2014-03-01

    An approach to utilizing adaptive mesh refinement algorithms for storm surge modeling is proposed. Currently numerical models exist that can resolve the details of coastal regions but are often too costly to be run in an ensemble forecasting framework without significant computing resources. The application of adaptive mesh refinement algorithms substantially lowers the computational cost of a storm surge model run while retaining much of the desired coastal resolution. The approach presented is implemented in the GeoClaw framework and compared to ADCIRC for Hurricane Ike along with observed tide gauge data and the computational cost of each model run. © 2014 Elsevier Ltd.

  8. Russian refining - an industry in transition

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, E [CentreInvest, Moscow (Russian Federation)

    1999-02-01

    In the old Soviet Union (now called the CIS), the refining industry is undergoing much modernisation, although the process is far from complete. Eventually, the CIS is expected to have a market-responsive competitive refining business. The expected transformation is discussed according to a five-stage plan. The stages are (i) the change from horizontally integrated entity to vertically integrated global concerns, (ii) the change from over-manned dinosaurs to modern efficient businesses, (iii) the move towards smaller, more advanced market-orientated processes, (iv) improving the transport and storage infrastructures and (v) improving accountability and profitability. The predictions for 2005 onwards are for sustained profitability. (UK)

  9. Creativity: a refinement of the concept for nursing practice.

    Science.gov (United States)

    Fasnacht, Patsy H

    2003-01-01

    This paper seeks to remove some of the ambiguity surrounding the conceptual meaning of creativity using techniques of concept refinement to advance the concept. Creativity is an essential component of nursing practice that occurs daily in nurse's interactions with clients, families and other nurses. Failure to acknowledge and encourage creativity in beginning nurses may hinder future development and innovations in nursing practice and in nursing science. In order to promote the development of creativity it is first necessary to clarify and refine the concept as it applies to nursing. A comprehensive review of a variety of computer and online databases resulted in thousands of articles on creativity between the years 1966 and 1999. The final sample (n = 48) was obtained using both stratified random and purposive sampling techniques. A content analysis of the literature was conducted using methods identified by Morse and illustrated in the work of Hupcey et al. Having determined the concept to be partially mature, the concept was advanced using techniques of concept refinement. Content analysis of the literature yielded three differing definitions for creativity: revelation, birth and reincarnation. Creativity occurs in the presence of intrinsic motivation and a nurturing environment. While value is often used to identify whether a product is creative, the value of the product cannot determine whether the process has occurred. The product produced determines evidence of the process of creativity. Limitations of this investigation are the use of secondary sources and the relatively small sample size (n = 48). Refinement of the concept of creativity indicates that it is a process that may be developed and influenced by the environment and is recognized by the product produced. Further investigation is needed to explore methods and techniques for developing creativity in nursing.

  10. Pilot scale refinning of crude soybean oil | Mensah | Journal of ...

    African Journals Online (AJOL)

    Pilot scale refinning of crude soybean oil. ... Abstract. A laboratory process for refining soybean has been scaled up to a 145 tonne per annum pilot plant to refine crude soybean oil. ... The quality of the refined oil was found to be within national and codex standard specifications for edible oil from vegetable sources.

  11. Refining intra-protein contact prediction by graph analysis

    Directory of Open Access Journals (Sweden)

    Eyal Eran

    2007-05-01

    Full Text Available Abstract Background Accurate prediction of intra-protein residue contacts from sequence information will allow the prediction of protein structures. Basic predictions of such specific contacts can be further refined by jointly analyzing predicted contacts, and by adding information on the relative positions of contacts in the protein primary sequence. Results We introduce a method for graph analysis refinement of intra-protein contacts, termed GARP. Our previously presented intra-contact prediction method by means of pair-to-pair substitution matrix (P2PConPred was used to test the GARP method. In our approach, the top contact predictions obtained by a basic prediction method were used as edges to create a weighted graph. The edges were scored by a mutual clustering coefficient that identifies highly connected graph regions, and by the density of edges between the sequence regions of the edge nodes. A test set of 57 proteins with known structures was used to determine contacts. GARP improves the accuracy of the P2PConPred basic prediction method in whole proteins from 12% to 18%. Conclusion Using a simple approach we increased the contact prediction accuracy of a basic method by 1.5 times. Our graph approach is simple to implement, can be used with various basic prediction methods, and can provide input for further downstream analyses.

  12. The structure of denisovite, a fibrous nanocrystalline polytypic disordered `very complex' silicate, studied by a synergistic multi-disciplinary approach employing methods of electron crystallography and X-ray powder diffraction

    Directory of Open Access Journals (Sweden)

    Ira V. Rozhdestvenskaya

    2017-05-01

    Full Text Available Denisovite is a rare mineral occurring as aggregates of fibres typically 200–500 nm diameter. It was confirmed as a new mineral in 1984, but important facts about its chemical formula, lattice parameters, symmetry and structure have remained incompletely known since then. Recently obtained results from studies using microprobe analysis, X-ray powder diffraction (XRPD, electron crystallography, modelling and Rietveld refinement will be reported. The electron crystallography methods include transmission electron microscopy (TEM, selected-area electron diffraction (SAED, high-angle annular dark-field imaging (HAADF, high-resolution transmission electron microscopy (HRTEM, precession electron diffraction (PED and electron diffraction tomography (EDT. A structural model of denisovite was developed from HAADF images and later completed on the basis of quasi-kinematic EDT data by ab initio structure solution using direct methods and least-squares refinement. The model was confirmed by Rietveld refinement. The lattice parameters are a = 31.024 (1, b = 19.554 (1 and c = 7.1441 (5 Å, β = 95.99 (3°, V = 4310.1 (5 Å3 and space group P12/a1. The structure consists of three topologically distinct dreier silicate chains, viz. two xonotlite-like dreier double chains, [Si6O17]10−, and a tubular loop-branched dreier triple chain, [Si12O30]12−. The silicate chains occur between three walls of edge-sharing (Ca,Na octahedra. The chains of silicate tetrahedra and the octahedra walls extend parallel to the z axis and form a layer parallel to (100. Water molecules and K+ cations are located at the centre of the tubular silicate chain. The latter also occupy positions close to the centres of eight-membered rings in the silicate chains. The silicate chains are geometrically constrained by neighbouring octahedra walls and present an ambiguity with respect to their z position along these walls, with displacements between neighbouring layers being

  13. Development and applications of the reverse neutron time-of-flight method with Fourier-type beam chopper

    International Nuclear Information System (INIS)

    Antson, O.

    1991-09-01

    The neutron powder diffraction method has been applied to the crystal structure analysis of high-temperature superconductors such as La 0 .8Sr 0 .2CuO 4 - y , YBa 2 Cu 3 O 7 - y and Bi 2 Sr 2 CaCu 2 O 8 + y optically active yttriumformate Y(HCOO) 3 , and β phase of deuterated acetonitrile, CD 3 CN. The structural information, containing symmetry, positional and thermal parameters, occupation factors and the order parameter, was obtained by measuring the coherent elastic scattering cross-section. The Rietveld profile refinement method was used for the extraction of structural parameters from experimental data. The diffraction spectra were obtained by measuring the time-of-flight distribution of neutrons with a Fourier-type beam chopper. The neutron diffraction spectrum is created by the on-line synthesis of the cross-correlation function between the beam modulation function and the detector intensity. Such an operational mode, called the reverse time-of-flight method, has many unique properties. The possibility of filtering out a low-frequency part of a diffraction spectrum, eg. incoherent background, by a properly selected band-pass filter has been studied. One of the practical applications of the reverse time-of-flight method, the Mini-Sfinks facility, is described with technical details, and its operational characteristics are compared with other high-resolution instruments

  14. Refining the Eye: Dermatology and Visual Literacy

    Science.gov (United States)

    Zimmermann, Corinne; Huang, Jennifer T.; Buzney, Elizabeth A.

    2016-01-01

    In 2014 the Museum of Fine Arts Boston and Harvard Medical School began a partnership focused on building visual literacy skills for dermatology residents in the Harvard Combined Dermatology Residency Program. "Refining the Eye: Art and Dermatology", a four session workshop, took place in the museum's galleries and utilized the Visual…

  15. Structural refinement and coarsening in deformed metals

    DEFF Research Database (Denmark)

    Hansen, N.; Huang, X.; Xing, Q.

    2005-01-01

    The microstructural refinement by plastic deformation is analysed in terms of key parameters, the spacing between and the misorientation angle across the boundaries subdividing the structure. Coarsening of such structures by annealing is also characterised. For both deformed and annealed structur...

  16. Structure refinement of polycrystalline orthorhombic yttrium ...

    Indian Academy of Sciences (India)

    The perovskite ceramic phases with composition Ca1−YTiO3+ (where = 0.1, 0.2 and 0.3; hereafter CYT-10, CYT-20 and CYT-30) have been synthesized by solid state reaction at 1050°C. The structure refinement using general structure analysis system (GSAS) software converges to satisfactory profile indicators ...

  17. Oil refining expansion criteria for Brazil

    International Nuclear Information System (INIS)

    Tavares, M.E.E.; Szklo, A.S.; Machado, G.V.; Schaeffer, R.; Mariano, J.B.; Sala, J.F.

    2006-01-01

    This paper assesses different strategies for the expansion of Brazil's oil refining segment, using criteria that range from energy security (reducing imports and vulnerability for key products) through to maximizing the profitability of this sector (boosting the output of higher value oil products) and adding value to Brazil's oil production (reducing exports of heavy acid oil). The development prospects are analyzed for conventional fuel production technology routes, sketching out three possible refining schemes for Brazilian oil and a GTL plant for producing gasoil from natural gas. Market scenario simulations indicate that investments will be required in Brazil's oil refining segment over and above those allocated to planned modifications in its current facilities, reducing the nation's vulnerability in terms of gasoil and petrochemical naphtha imports. Although not economically attractive, oil refining is a key activity that is crucial to oil company strategies. The decision to invest in this segment depends on local infrastructure conditions, environmental constraints and fuel specifications, in addition to oil company strategies, steady growth in demand and the definition of a government policy that eases institutional risks. (author)

  18. Oil refining expansion criteria for Brazil

    International Nuclear Information System (INIS)

    Tavares, Marina Elisabete Espinho; Szklo, Alexandre Salem; Machado, Giovani Vitoria; Schaeffer, Roberto; Mariano, Jacqueline Barboza; Sala, Janaina Francisco

    2006-01-01

    This paper assesses different strategies for the expansion of Brazil's oil refining segment, using criteria that range from energy security (reducing imports and vulnerability for key products) through to maximizing the profitability of this sector (boosting the output of higher value oil products) and adding value to Brazil's oil production (reducing exports of heavy acid oil). The development prospects are analyzed for conventional fuel production technology routes, sketching out three possible refining schemes for Brazilian oil and a GTL plant for producing gasoil from natural gas. Market scenario simulations indicate that investments will be required in Brazil's oil refining segment over and above those allocated to planned modifications in its current facilities, reducing the nation's vulnerability in terms of gasoil and petrochemical naphtha imports. Although not economically attractive, oil refining is a key activity that is crucial to oil company strategies. The decision to invest in this segment depends on local infrastructure conditions, environmental constraints and fuel specifications, in addition to oil company strategies, steady growth in demand and the definition of a government policy that eases institutional risks

  19. On Syntactic and Semantic Action Refinement

    NARCIS (Netherlands)

    Goltz, Ursula; Gorrieri, Roberto; Rensink, Arend

    1992-01-01

    The semantic definition of action refinement on labelled event structures is compared with the notion of syntactic substitution,which can be used as another notion of action refiment in a process algebraic setting. This is done by studying a process algebra equipped with the ACP sequential

  20. Anomalies in the refinement of isoleucine

    NARCIS (Netherlands)

    Berntsen, K.R.M.; Vriend, G.

    2014-01-01

    A study of isoleucines in protein structures solved using X-ray crystallography revealed a series of systematic trends for the two side-chain torsion angles chi1 and chi2 dependent on the resolution, secondary structure and refinement software used. The average torsion angles for the nine rotamers

  1. Refining crude oils and gasolines, etc

    Energy Technology Data Exchange (ETDEWEB)

    1931-11-23

    A process of refining crude oils and gasolines distilled from shale and the like is described, consisting of submitting them to a prewash with soda, an oxidation preferably with hypochlorite solution, a hydrogenation with nascent hydrogen, and finally rectification and neutralization.

  2. Refinement from a control problem to program

    DEFF Research Database (Denmark)

    Schenke, Michael; Ravn, Anders P.

    1996-01-01

    The distinguishing feature of the presented refinement approach is that it links formalisms from a top level requirements notation down to programs together in a mathematically coherent development trajectory. The approach uses Duration Calculus, a real-time interval logic, to specifyrequirements...

  3. Robust Refinement as Implemented in TOPAS

    Energy Technology Data Exchange (ETDEWEB)

    Stone, K.; Stephens, P

    2010-01-01

    A robust refinement procedure is implemented in the program TOPAS through an iterative reweighting of the data. Examples are given of the procedure as applied to fitting partially overlapped peaks by full and partial models and also of the structures of ibuprofen and acetaminophen in the presence of unmodeled impurity contributions

  4. Quantum Geometry of Refined Topological Strings

    NARCIS (Netherlands)

    Aganagic, M.; Cheng, M.C.N.; Dijkgraaf, R.; Kreft, D.; Vafa, C.

    2012-01-01

    We consider branes in refined topological strings. We argue that their wavefunctions satisfy a Schrödinger equation depending on multiple times and prove this in the case where the topological string has a dual matrix model description. Furthermore, in the limit where one of the equivariant

  5. Red refinements of simplices into congruent subsimplices

    Czech Academy of Sciences Publication Activity Database

    Korotov, S.; Křížek, Michal

    2014-01-01

    Roč. 67, č. 12 (2014), s. 2199-2204 ISSN 0898-1221 R&D Projects: GA ČR GA14-02067S Institutional support: RVO:67985840 Keywords : sommerville tetrahedron * red refinement * higher-dimensional simplex Subject RIV: BA - General Mathematics Impact factor: 1.697, year: 2014 http://www.sciencedirect.com/science/article/pii/S0898122114000662

  6. Interactive visual exploration and refinement of cluster assignments.

    Science.gov (United States)

    Kern, Michael; Lex, Alexander; Gehlenborg, Nils; Johnson, Chris R

    2017-09-12

    With ever-increasing amounts of data produced in biology research, scientists are in need of efficient data analysis methods. Cluster analysis, combined with visualization of the results, is one such method that can be used to make sense of large data volumes. At the same time, cluster analysis is known to be imperfect and depends on the choice of algorithms, parameters, and distance measures. Most clustering algorithms don't properly account for ambiguity in the source data, as records are often assigned to discrete clusters, even if an assignment is unclear. While there are metrics and visualization techniques that allow analysts to compare clusterings or to judge cluster quality, there is no comprehensive method that allows analysts to evaluate, compare, and refine cluster assignments based on the source data, derived scores, and contextual data. In this paper, we introduce a method that explicitly visualizes the quality of cluster assignments, allows comparisons of clustering results and enables analysts to manually curate and refine cluster assignments. Our methods are applicable to matrix data clustered with partitional, hierarchical, and fuzzy clustering algorithms. Furthermore, we enable analysts to explore clustering results in context of other data, for example, to observe whether a clustering of genomic data results in a meaningful differentiation in phenotypes. Our methods are integrated into Caleydo StratomeX, a popular, web-based, disease subtype analysis tool. We show in a usage scenario that our approach can reveal ambiguities in cluster assignments and produce improved clusterings that better differentiate genotypes and phenotypes.

  7. The state of animal welfare in the context of refinement.

    Science.gov (United States)

    Zurlo, Joanne; Hutchinson, Eric

    2014-01-01

    The ultimate goal of the Three Rs is the full replacement of animals used in biomedical research and testing. However, replacement is unlikely to occur in the near future; therefore the scientific community as a whole must continue to devote considerable effort to ensure optimal animal welfare for the benefit of the science and the animals, i.e., the R of refinement. Laws governing the care and use of laboratory animals have recently been revised in Europe and the US and these place greater emphasis on promoting the well-being of the animals in addition to minimizing pain and distress. Social housing for social species is now the default condition, which can present a challenge in certain experimental settings and for certain species. The practice of positive reinforcement training of laboratory animals, particularly non-human primates, is gathering momentum but is not yet universally employed. Enhanced consideration of refinement extends to rodents, particularly mice, whose use is still increasing as more genetically modified models are generated. The wastage of extraneous mice and the method of their euthanasia are refinement issues that still need to be addressed. An international, concerted effort into defining the needs of laboratory animals is still necessary to improve the quality of the animal models used as well as their welfare.

  8. Morse Set Classification and Hierarchical Refinement Using Conley Index

    KAUST Repository

    Guoning Chen,; Qingqing Deng,; Szymczak, A.; Laramee, R. S.; Zhang, E.

    2012-01-01

    Morse decomposition provides a numerically stable topological representation of vector fields that is crucial for their rigorous interpretation. However, Morse decomposition is not unique, and its granularity directly impacts its computational cost. In this paper, we propose an automatic refinement scheme to construct the Morse Connection Graph (MCG) of a given vector field in a hierarchical fashion. Our framework allows a Morse set to be refined through a local update of the flow combinatorialization graph, as well as the connection regions between Morse sets. The computation is fast because the most expensive computation is concentrated on a small portion of the domain. Furthermore, the present work allows the generation of a topologically consistent hierarchy of MCGs, which cannot be obtained using a global method. The classification of the extracted Morse sets is a crucial step for the construction of the MCG, for which the Poincar index is inadequate. We make use of an upper bound for the Conley index, provided by the Betti numbers of an index pair for a translation along the flow, to classify the Morse sets. This upper bound is sufficiently accurate for Morse set classification and provides supportive information for the automatic refinement process. An improved visualization technique for MCG is developed to incorporate the Conley indices. Finally, we apply the proposed techniques to a number of synthetic and real-world simulation data to demonstrate their utility. © 2006 IEEE.

  9. Morse Set Classification and Hierarchical Refinement Using Conley Index

    KAUST Repository

    Guoning Chen,

    2012-05-01

    Morse decomposition provides a numerically stable topological representation of vector fields that is crucial for their rigorous interpretation. However, Morse decomposition is not unique, and its granularity directly impacts its computational cost. In this paper, we propose an automatic refinement scheme to construct the Morse Connection Graph (MCG) of a given vector field in a hierarchical fashion. Our framework allows a Morse set to be refined through a local update of the flow combinatorialization graph, as well as the connection regions between Morse sets. The computation is fast because the most expensive computation is concentrated on a small portion of the domain. Furthermore, the present work allows the generation of a topologically consistent hierarchy of MCGs, which cannot be obtained using a global method. The classification of the extracted Morse sets is a crucial step for the construction of the MCG, for which the Poincar index is inadequate. We make use of an upper bound for the Conley index, provided by the Betti numbers of an index pair for a translation along the flow, to classify the Morse sets. This upper bound is sufficiently accurate for Morse set classification and provides supportive information for the automatic refinement process. An improved visualization technique for MCG is developed to incorporate the Conley indices. Finally, we apply the proposed techniques to a number of synthetic and real-world simulation data to demonstrate their utility. © 2006 IEEE.

  10. Mesh refinement for uncertainty quantification through model reduction

    International Nuclear Information System (INIS)

    Li, Jing; Stinis, Panos

    2015-01-01

    We present a novel way of deciding when and where to refine a mesh in probability space in order to facilitate uncertainty quantification in the presence of discontinuities in random space. A discontinuity in random space makes the application of generalized polynomial chaos expansion techniques prohibitively expensive. The reason is that for discontinuous problems, the expansion converges very slowly. An alternative to using higher terms in the expansion is to divide the random space in smaller elements where a lower degree polynomial is adequate to describe the randomness. In general, the partition of the random space is a dynamic process since some areas of the random space, particularly around the discontinuity, need more refinement than others as time evolves. In the current work we propose a way to decide when and where to refine the random space mesh based on the use of a reduced model. The idea is that a good reduced model can monitor accurately, within a random space element, the cascade of activity to higher degree terms in the chaos expansion. In turn, this facilitates the efficient allocation of computational sources to the areas of random space where they are more needed. For the Kraichnan–Orszag system, the prototypical system to study discontinuities in random space, we present theoretical results which show why the proposed method is sound and numerical results which corroborate the theory

  11. Validating neural-network refinements of nuclear mass models

    Science.gov (United States)

    Utama, R.; Piekarewicz, J.

    2018-01-01

    Background: Nuclear astrophysics centers on the role of nuclear physics in the cosmos. In particular, nuclear masses at the limits of stability are critical in the development of stellar structure and the origin of the elements. Purpose: We aim to test and validate the predictions of recently refined nuclear mass models against the newly published AME2016 compilation. Methods: The basic paradigm underlining the recently refined nuclear mass models is based on existing state-of-the-art models that are subsequently refined through the training of an artificial neural network. Bayesian inference is used to determine the parameters of the neural network so that statistical uncertainties are provided for all model predictions. Results: We observe a significant improvement in the Bayesian neural network (BNN) predictions relative to the corresponding "bare" models when compared to the nearly 50 new masses reported in the AME2016 compilation. Further, AME2016 estimates for the handful of impactful isotopes in the determination of r -process abundances are found to be in fairly good agreement with our theoretical predictions. Indeed, the BNN-improved Duflo-Zuker model predicts a root-mean-square deviation relative to experiment of σrms≃400 keV. Conclusions: Given the excellent performance of the BNN refinement in confronting the recently published AME2016 compilation, we are confident of its critical role in our quest for mass models of the highest quality. Moreover, as uncertainty quantification is at the core of the BNN approach, the improved mass models are in a unique position to identify those nuclei that will have the strongest impact in resolving some of the outstanding questions in nuclear astrophysics.

  12. Thermal-chemical Mantle Convection Models With Adaptive Mesh Refinement

    Science.gov (United States)

    Leng, W.; Zhong, S.

    2008-12-01

    In numerical modeling of mantle convection, resolution is often crucial for resolving small-scale features. New techniques, adaptive mesh refinement (AMR), allow local mesh refinement wherever high resolution is needed, while leaving other regions with relatively low resolution. Both computational efficiency for large- scale simulation and accuracy for small-scale features can thus be achieved with AMR. Based on the octree data structure [Tu et al. 2005], we implement the AMR techniques into the 2-D mantle convection models. For pure thermal convection models, benchmark tests show that our code can achieve high accuracy with relatively small number of elements both for isoviscous cases (i.e. 7492 AMR elements v.s. 65536 uniform elements) and for temperature-dependent viscosity cases (i.e. 14620 AMR elements v.s. 65536 uniform elements). We further implement tracer-method into the models for simulating thermal-chemical convection. By appropriately adding and removing tracers according to the refinement of the meshes, our code successfully reproduces the benchmark results in van Keken et al. [1997] with much fewer elements and tracers compared with uniform-mesh models (i.e. 7552 AMR elements v.s. 16384 uniform elements, and ~83000 tracers v.s. ~410000 tracers). The boundaries of the chemical piles in our AMR code can be easily refined to the scales of a few kilometers for the Earth's mantle and the tracers are concentrated near the chemical boundaries to precisely trace the evolvement of the boundaries. It is thus very suitable for our AMR code to study the thermal-chemical convection problems which need high resolution to resolve the evolvement of chemical boundaries, such as the entrainment problems [Sleep, 1988].

  13. The relationship between viscosity and refinement efficiency of pure aluminum by Al-Ti-B refiner

    Energy Technology Data Exchange (ETDEWEB)

    Yu Lina [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Liu Xiangfa [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China)]. E-mail: xfliu@sdu.edu.cn

    2006-11-30

    The relationship between viscosity and refinement efficiency of pure aluminum with the addition of Al-Ti-B master alloy was studied in this paper. The experimental results show that when the grain size of solidified sample is finer the viscosity of the melt is higher after the addition of different Al-Ti-B master alloys. This indicates that viscosity can be used to approximately estimate the refinement efficiency of Al-Ti-B refiners in production to a certain extent. The main reason was also discussed in this paper by using transmission electron microscopy (TEM) analysis and differential scanning calorimetry (DSC) experiment.

  14. Accurate macromolecular crystallographic refinement: incorporation of the linear scaling, semiempirical quantum-mechanics program DivCon into the PHENIX refinement package.

    Science.gov (United States)

    Borbulevych, Oleg Y; Plumley, Joshua A; Martin, Roger I; Merz, Kenneth M; Westerhoff, Lance M

    2014-05-01

    Macromolecular crystallographic refinement relies on sometimes dubious stereochemical restraints and rudimentary energy functionals to ensure the correct geometry of the model of the macromolecule and any covalently bound ligand(s). The ligand stereochemical restraint file (CIF) requires a priori understanding of the ligand geometry within the active site, and creation of the CIF is often an error-prone process owing to the great variety of potential ligand chemistry and structure. Stereochemical restraints have been replaced with more robust functionals through the integration of the linear-scaling, semiempirical quantum-mechanics (SE-QM) program DivCon with the PHENIX X-ray refinement engine. The PHENIX/DivCon package has been thoroughly validated on a population of 50 protein-ligand Protein Data Bank (PDB) structures with a range of resolutions and chemistry. The PDB structures used for the validation were originally refined utilizing various refinement packages and were published within the past five years. PHENIX/DivCon does not utilize CIF(s), link restraints and other parameters for refinement and hence it does not make as many a priori assumptions about the model. Across the entire population, the method results in reasonable ligand geometries and low ligand strains, even when the original refinement exhibited difficulties, indicating that PHENIX/DivCon is applicable to both single-structure and high-throughput crystallography.

  15. Application of powder X-ray diffraction and the Rietveld method to the analysis of oxidation processes and products in sulphidic mine tailings

    DEFF Research Database (Denmark)

    Balic Zunic, Tonci; Katerinopoulou, Anna; Edsberg, Anders

    2011-01-01

    silica were applied as proper models. The procedures developed on test mixtures result in estimated errors of determination typically lower than 2 wt%. The approach was applied to the analysis of the complex problem of estimating mass balance in oxidized mine tailings from the Nanisivik Mine, Nunavut......, Canada revealing an oxidized proportion of 9 % of total pyrite content in the well drained tailings during a period of 8 years and a negligible oxidation in the water-covered tailings....

  16. Development and application of a parallel finite volume method for flow simulation on unstructured grids with local refinement; Entwicklung und Anwendung eines parallelen Finite-Volumen-Verfahrens zur Stroemungssimulation auf unstrukturierten Gittern mit lokaler Verfeinerung

    Energy Technology Data Exchange (ETDEWEB)

    Seidl, V.

    1997-11-01

    A finite vomume method for calculation of steady and unsteady flow on unstructured grids is parallelized by local spatial and time decomposition. In the first case, a parallel variant of the conjugated gradient method with multiple local preconditioning is formulated and analyzed. The method is tested for simple applications (e.g. flow around a cylinder). The second part of the publication describes a direct numerical simulation of turbulent flow around a sphere at a Reynolds number of 5000 (based on flow velocity and sphere diameter). Current and Reynolds-averaged flow fields are discussed. Particular emphasis is placed on coordinate-independent representation of the anisotropy ratios of the Reynolds tensor and dissipation tensor. (orig.) [Deutsch] Ein Finite-Volumen-Verfahren fuer die Berechnung stationaerer und instationaerer Stroemungen auf unstrukturierten Netzen wird durch Gebietszerlegung im Raum und Zeit parallelisiert. Fuer die raeumliche Zerlegung wird eine parallele Variante der konjugierten Gradienten Methode mit mehrfacher, lokaler Vorkonditionierung formuliert und analysiert. Anhand einfacher Anwendungsbeispiele (Zylinderumstroemung, deckelgetriebene Nischenstroemung) wird das entwickelte Gesamtverfahren getestet und seine Effizienz bestimmt. Der zweite Teil der Arbeit beschreibt eine direkte numerische Simulation der turbulenten Kugelumstroemung bei einer Reynolds-Zahl von 5 000 (basierend auf Anstroemgeschwindigkeit und Kugeldurchmesser). In der Ergebnisauswertung werden augenblickliche und Reynolds-gemittelte Stroemungsfelder diskutiert und besonderer Wert auf eine koordinatenunabhaengige Darstellung der Anisotropieverhaeltnisse des Reynolds-Tensors und des Dissipationstensors gelegt. (orig.)

  17. Note: Additionally refined new possibilities of plasma probe diagnostics

    Science.gov (United States)

    Riaby, V. A.; Savinov, V. P.; Masherov, P. E.; Yakunin, V. G.

    2018-03-01

    In two previous Notes published in this journal, a method of measuring probe sheath thickness and ion mass was described using Langmuir probe diagnostics in low pressure xenon plasma close to Maxwellian substance. According to the first Note, this method includes two stages: (i) in a special experiment with known ion mass, the Bohm and Child-Langmuir-Boguslavsky (CLB) equations for cylindrical Langmuir probes used in this xenon plasma were solved jointly to determine the probe sheath thicknesses and Bohm coefficient CBCyl ≈ 1.13; and (ii) in a general experiment, with known CBCyl, the same equations could be solved to obtain the probe sheath thicknesses and the mean ion mass. In the second Note, the (i) stage of this method was refined: the results of the CLB probe sheath model application, which were termed "evaluations," were corrected using the step-front probe sheath model, which was closer to reality in the special experiment with the xenon plasma. This process resulted in a Bohm coefficient of CBCyl ≈ 1.23 for the cylindrical probe. In the present Note, corrected xenon plasma parameters without the influence of the bare probe protective shield were used for the (i) stage of this diagnostic method. This action also refined the Bohm coefficient, lowering it to CBCyl ≈ 0.745 for cylindrical probes. This advance makes the new diagnostics method more objective and reliable.

  18. R and D status of oxide electro-refining reprocessing technology

    International Nuclear Information System (INIS)

    Myochin, Munetaka

    2005-01-01

    The oxide electro-refining pyrochemical reprocessing is excellent in the resistivity against nuclear material diversion and in the suitability for oxide fuel cycle and has an excellent affinity for the technology of fuel production using the vibropac method. The oxide electro-refining pyrochemical reprocessing system has therefore been examined as a part of studies of commercialization of FBR cycle. This report outlines the examination results of fundamental data acquired for the system design. (M.H.)

  19. Processing (refining) of petroleum and natural gases. Pererabotka neftyanykh i prirodnykh gazov

    Energy Technology Data Exchange (ETDEWEB)

    Berlin, M A; Gorechenkov, V G; Volkov, N P

    1981-01-01

    A discussion is made of the theoretical principles underlying the processes involved in the processing of natural and petroleum gases and gas condensate. Information is given on apparatus, engineering systems, and machine methods for the designing of gas refining plants. The book is intended for engineers and operation personnel of gas refining plants, and might also be useful to senior undergraduates at chemistry and petroleum institutes of higher learning. 278 references, 54 tables.

  20. Measuring sensitivity in pharmacoeconomic studies. Refining point sensitivity and range sensitivity by incorporating probability distributions.

    Science.gov (United States)

    Nuijten, M J

    1999-07-01

    The aim of the present study is to describe a refinement of a previously presented method, based on the concept of point sensitivity, to deal with uncertainty in economic studies. The original method was refined by the incorporation of probability distributions which allow a more accurate assessment of the level of uncertainty in the model. In addition, a bootstrap method was used to create a probability distribution for a fixed input variable based on a limited number of data points. The original method was limited in that the sensitivity measurement was based on a uniform distribution of the variables and that the overall sensitivity measure was based on a subjectively chosen range which excludes the impact of values outside the range on the overall sensitivity. The concepts of the refined method were illustrated using a Markov model of depression. The application of the refined method substantially changed the ranking of the most sensitive variables compared with the original method. The response rate became the most sensitive variable instead of the 'per diem' for hospitalisation. The refinement of the original method yields sensitivity outcomes, which greater reflect the real uncertainty in economic studies.

  1. Automata Learning through Counterexample Guided Abstraction Refinement

    DEFF Research Database (Denmark)

    Aarts, Fides; Heidarian, Faranak; Kuppens, Harco

    2012-01-01

    to a small set of abstract events that can be handled by automata learning tools. In this article, we show how such abstractions can be constructed fully automatically for a restricted class of extended finite state machines in which one can test for equality of data parameters, but no operations on data...... are allowed. Our approach uses counterexample-guided abstraction refinement: whenever the current abstraction is too coarse and induces nondeterministic behavior, the abstraction is refined automatically. Using Tomte, a prototype tool implementing our algorithm, we have succeeded to learn – fully......Abstraction is the key when learning behavioral models of realistic systems. Hence, in most practical applications where automata learning is used to construct models of software components, researchers manually define abstractions which, depending on the history, map a large set of concrete events...

  2. Refined reservoir description to maximize oil recovery

    International Nuclear Information System (INIS)

    Flewitt, W.E.

    1975-01-01

    To assure maximized oil recovery from older pools, reservoir description has been advanced by fully integrating original open-hole logs and the recently introduced interpretive techniques made available through cased-hole wireline saturation logs. A refined reservoir description utilizing normalized original wireline porosity logs has been completed in the Judy Creek Beaverhill Lake ''A'' Pool, a reefal carbonate pool with current potential productivity of 100,000 BOPD and 188 active wells. Continuous porosity was documented within a reef rim and cap while discontinuous porous lenses characterized an interior lagoon. With the use of pulsed neutron logs and production data a separate water front and pressure response was recognized within discrete environmental units. The refined reservoir description aided in reservoir simulation model studies and quantifying pool performance. A pattern water flood has now replaced the original peripheral bottom water drive to maximize oil recovery

  3. Cleaning Data with OpenRefine

    Directory of Open Access Journals (Sweden)

    Seth van Hooland

    2013-08-01

    Full Text Available Duplicate records, empty values and inconsistent formats are phenomena we should be prepared to deal with when using historical data sets. This lesson will teach you how to discover inconsistencies in data contained within a spreadsheet or a database. As we increasingly share, aggregate and reuse data on the web, historians will need to respond to data quality issues which inevitably pop up. Using a program called OpenRefine, you will be able to easily identify systematic errors such as blank cells, duplicates, spelling inconsistencies, etc. OpenRefine not only allows you to quickly diagnose the accuracy of your data, but also to act upon certain errors in an automated manner.

  4. Refined 3d-3d correspondence

    Energy Technology Data Exchange (ETDEWEB)

    Alday, Luis F.; Genolini, Pietro Benetti; Bullimore, Mathew; Loon, Mark van [Mathematical Institute, University of Oxford, Andrew Wiles Building,Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG (United Kingdom)

    2017-04-28

    We explore aspects of the correspondence between Seifert 3-manifolds and 3d N=2 supersymmetric theories with a distinguished abelian flavour symmetry. We give a prescription for computing the squashed three-sphere partition functions of such 3d N=2 theories constructed from boundary conditions and interfaces in a 4d N=2{sup ∗} theory, mirroring the construction of Seifert manifold invariants via Dehn surgery. This is extended to include links in the Seifert manifold by the insertion of supersymmetric Wilson-’t Hooft loops in the 4d N=2{sup ∗} theory. In the presence of a mass parameter for the distinguished flavour symmetry, we recover aspects of refined Chern-Simons theory with complex gauge group, and in particular construct an analytic continuation of the S-matrix of refined Chern-Simons theory.

  5. Government will shape China's refining boom

    International Nuclear Information System (INIS)

    Wang, H.

    1995-01-01

    China's refining system is undergoing a major overhaul. New refineries are being built as existing ones are upgraded and expanded. The success of refineries funded completely or partially by non-chinese companies will depend in part on Chinese government policy. There will be demand for products from third-party processing facilities, but hard current is necessary for the investors to repatriate profits and for china Petrochemical Corp. (Sinopec) to bid on the products from such facilities. The limited convertibility of chinese current constitutes a major central control over the country's entire economy. This control can be affected by limiting product exchange participants and the volumes to be traded. Such a limitation, however, will reduce access of non-Chinese companies to China's markets, and is not likely to occur in the next 10 years. The paper discusses the current situation in capacity and in refining, capacity, expansion, refinery planning, construction projects, third-party processing, and the prospects for change

  6. Panorama 2016 - Refining outlook for 2035

    International Nuclear Information System (INIS)

    Marion, Pierre; Saint-Antonin, Valerie

    2015-12-01

    The rising influence of objectives intended to address the energy transition in global industry helps to perpetuate a high degree of uncertainty about changes in the transportation sector, currently a bastion of the oil industry. How can the growing need for individual mobility be met while reducing Greenhouse Gas (GHG) emissions in a world of open international competition? The refining sector is gaining strength in Asia and the Middle East to the detriment of Europe and North America, reflecting demand and the intrinsic competitiveness of various geographic regions. The 2025 worldwide roll-out (2020 in Europe) of a bunker fuel grade below 0.5 wt% (percentage by weight) in sulphur could experience delays, given the number of installations to be completed. Finally, the reversal of the 'all diesel' trend in the European transport market is a positive change for the European refining industry. (authors)

  7. The big shedding of the European refining

    International Nuclear Information System (INIS)

    Lepetit, V.

    2007-01-01

    Everywhere in Europe the oil companies are selling their refineries. Even if they work at full capacity, the interest of the European market is far below the one of Asia where demand is in full expansion and Middle-East where the raw matter is abundant. The world refining capacity is of 86 million barrel per day and should reach 106 million barrel per day in 2020. (J.S.)

  8. Refining Automatically Extracted Knowledge Bases Using Crowdsourcing

    OpenAIRE

    Li, Chunhua; Zhao, Pengpeng; Sheng, Victor S.; Xian, Xuefeng; Wu, Jian; Cui, Zhiming

    2017-01-01

    Machine-constructed knowledge bases often contain noisy and inaccurate facts. There exists significant work in developing automated algorithms for knowledge base refinement. Automated approaches improve the quality of knowledge bases but are far from perfect. In this paper, we leverage crowdsourcing to improve the quality of automatically extracted knowledge bases. As human labelling is costly, an important research challenge is how we can use limited human resources to maximize the quality i...

  9. Cleaning Data with OpenRefine

    OpenAIRE

    Seth van Hooland; Ruben Verborgh; Max De Wilde

    2013-01-01

    Duplicate records, empty values and inconsistent formats are phenomena we should be prepared to deal with when using historical data sets. This lesson will teach you how to discover inconsistencies in data contained within a spreadsheet or a database. As we increasingly share, aggregate and reuse data on the web, historians will need to respond to data quality issues which inevitably pop up. Using a program called OpenRefine, you will be able to easily identify systematic errors such as blank...

  10. Refining of biodiesel by ceramic membrane separation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yong; Ou, Shiyi; Tan, Yanlai; Tang, Shuze [Department of Food Science and Engineering, Jinan University, Guangzhou 510632 (China); Wang, Xingguo; Liu, Yuanfa [School of Food Science and Technology, Jiangnan University, Wuxi 214112 (China)

    2009-03-15

    A ceramic membrane separation process for biodiesel refining was developed to reduce the considerable usage of water needed in the conventional water washing process. Crude biodiesel produced by refined palm oil was micro-filtered by ceramic membranes of the pore size of 0.6, 0.2 and 0.1 {mu}m to remove the residual soap and free glycerol, at the transmembrane pressure of 0.15 MPa and temperature of 60 C. The flux through membrane maintained at 300 L m{sup -} {sup 2} h{sup -} {sup 1} when the volumetric concentrated ratio reached 4. The content of potassium, sodium, calcium and magnesium in the whole permeate was 1.40, 1.78, 0.81 and 0.20 mg/kg respectively, as determined by inductively coupled plasma-atomic emission spectroscopy. These values are lower than the EN 14538 specifications. The residual free glycerol in the permeate was estimated by water extraction, its value was 0.0108 wt.%. This ceramic membrane technology was a potential environmental process for the refining of biodiesel. (author)

  11. A Canadian refiner's perspective of synthetic crudes

    International Nuclear Information System (INIS)

    Halford, T.L.; McIntosh, A.P.; Rasmussen

    1997-01-01

    Some of the factors affecting a refiner's choice of crude oil include refinery hardware, particularly gas oil crackers, products slate and product specifications, crude availability, relative crude price and crude quality. An overview of synthetic crude, the use of synthetic crude combined with other crudes and a comparison of synthetic crude with conventional crude oil was given. The two main users of synthetic crude are basically two groups of refiners, those large groups who use synthetic crude combined with other crudes, and a smaller group who run synthetic crude on specially designed units as a sole feed. The effects of changes in fuel legislation were reviewed. It was predicted that the changes will have a mixed impact on the value of synthetic crude, but low sulphur diesel regulations and gasoline sulphur regulations will make current synthetic crudes attractive. The big future change with a negative impact will be diesel cetane increases to reduce engine emissions. This will reduce synthetic crude attractiveness due to distillate yields and quality and high gas oil yields. Similarly, any legislation limiting aromatics in diesel fuel will also make synthetic crudes less attractive. Problems experienced by refiners with hardware dedicated to synthetic crude (salt, naphthenic acid, fouling, quality variations) were also reviewed. 3 tabs

  12. Oil price scenarios and refining profitability

    International Nuclear Information System (INIS)

    Sweeney, B.

    1993-01-01

    Currently refining profitability is low because there has been an overbuilding of conversion capacity in Western Europe in the last round. Oil marketing, the chemicals business and the fundamental economy itself are at low points in their cycles which have not coincided, at least in the UK, since 1975. Against that gloomy background, it is predicted that downstream profitability will recover in the mid-1990s. Crude oil prices will remain low until the call on OPEC crude increases again and takes up the capacity which has been brought on stream in response to the Gulf War. When this happens, it is likely to trigger another price spike and another round of investment in production capacity. Environmentally driven investments in desulphurisation or emissions reduction will be poorly remunerated all the way through the value chain. Refining margins will recover when white oil demand growth tightens up the need for conversion capacity. Marketing will need to reduce the retail network overcapacity in the mature markets if it is to improve its profitability. In this period of low profitability, even with the light at the end of the tunnel for refiners in the middle of the decade, the industry structure is under threat. There is a strong argument for new modes of competitive behaviour which are backed by strong elements of cooperation. (author)

  13. Problems persist for French refining sector

    International Nuclear Information System (INIS)

    Beck, R.J.

    1992-01-01

    This paper reports that France's refiners face a continuing shortfall of middle distillate capacity and a persistent surplus of heavy fuel oil. That's the main conclusion of the official Hydrocarbon Directorate's report on how France's refining sector performed in 1991. Imports up---The directorate noted that although net production of refined products in French refineries rose to 1.534 million b/d in 1991 from 1.48 million b/d in 1990, products imports jumped 9.7% to 602,000 b/d in the period. The glut of heavy fuel oil eased to some extent last year because French nuclear power capacity, heavily dependent on ample water supplies, was crimped by drought. That spawned fuel switching. The most note worthy increase in imports was for motor diesel, climbing to 176,000 b/d from 148,000 b/d in 1990. Tax credits are spurring French consumption of that fuel. For the first time, consumption of motor diesel in 1991 outstripped that of gasoline at 374,000 b/d and 356,000 b/d respectively

  14. Refining glass structure in two dimensions

    Science.gov (United States)

    Sadjadi, Mahdi; Bhattarai, Bishal; Drabold, D. A.; Thorpe, M. F.; Wilson, Mark

    2017-11-01

    Recently determined atomistic scale structures of near-two dimensional bilayers of vitreous silica (using scanning probe and electron microscopy) allow us to refine the experimentally determined coordinates to incorporate the known local chemistry more precisely. Further refinement is achieved by using classical potentials of varying complexity: one using harmonic potentials and the second employing an electrostatic description incorporating polarization effects. These are benchmarked against density functional calculations. Our main findings are that (a) there is a symmetry plane between the two disordered layers, a nice example of an emergent phenomena, (b) the layers are slightly tilted so that the Si-O-Si angle between the two layers is not 180∘ as originally thought but rather 175 ±2∘ , and (c) while interior areas that are not completely imagined can be reliably reconstructed, surface areas are more problematic. It is shown that small crystallites that appear are just as expected statistically in a continuous random network. This provides a good example of the value that can be added to disordered structures imaged at the atomic level by implementing computer refinement.

  15. Galaxy Tagging: photometric redshift refinement and group richness enhancement

    Science.gov (United States)

    Kafle, P. R.; Robotham, A. S. G.; Driver, S. P.; Deeley, S.; Norberg, P.; Drinkwater, M. J.; Davies, L. J.

    2018-06-01

    We present a new scheme, galtag, for refining the photometric redshift measurements of faint galaxies by probabilistically tagging them to observed galaxy groups constructed from a brighter, magnitude-limited spectroscopy survey. First, this method is tested on the DESI light-cone data constructed on the GALFORM galaxy formation model to tests its validity. We then apply it to the photometric observations of galaxies in the Kilo-Degree Imaging Survey (KiDS) over a 1 deg2 region centred at 15h. This region contains Galaxy and Mass Assembly (GAMA) deep spectroscopic observations (i-bandhttps://github.com/pkaf/galtag.git.

  16. Synthesis and characterization of Cr2O3 nanoparticles through sol-gel proteic method

    International Nuclear Information System (INIS)

    Medeiros, Angela Maria de Lemos

    2007-01-01

    In the last years, nanoparticles have becoming important to several researchers. This research reside in the fact that new and uncommon physical and chemical properties, absent in the same material in macro and microscopic size, are observed in this new scale. The subject of this study is obtaining chromium oxide nanoparticles (Cr 2 O 3 ) by sol–gel proteic process using gelatin as an organic precursor. This process appears as a new alternative for the synthesis of oxides for great applications with high efficiency and low cost. The interest in that material is due to the several applications such as green pigments, coverings of materials for thermal protection and mainly as catalyst of countless products originating from of the industry of the petroleum, among others. This new route, using chromium salt as chromium source, produces nanoparticles with average particle size between 20 and 60nm. These values were obtained for different crystallographic direction by means of X-Ray Diffraction (XRD) technique and the structure refinement by Rietveld method were applied in several samples prepared at different temperatures. Other techniques have been used in order to complement the XRD results. (author)

  17. Low-temperature synthesis and characterization of anatase TiO2 nanoparticles by an acid assisted sol–gel method

    International Nuclear Information System (INIS)

    Leyva-Porras, C.; Toxqui-Teran, A.; Vega-Becerra, O.; Miki-Yoshida, M.; Rojas-Villalobos, M.; García-Guaderrama, M.

    2015-01-01

    The synthesis of anatase TiO 2 nanoparticles by an acid-assisted sol–gel method at 25 and 80 °C is described. Specifically, acetic acid (AA) was used and the evolution of the anatase phase with the amount of AA was observed. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) both showed that a pure anatase phase was obtained with particle size smaller than 5 nm. Structural refinements and quantitative determination of phase composition was achieved by using the Rietveld method. The particle size distribution became slightly narrower as the amount of AA was increased. Raman spectroscopy showed that when the amount of AA was increased a small amount of brookite was present at the contamination level. The anatase phase was studied by differential thermal analysis (DTA), providing phase stability up to 600 °C. These and other results were discussed in terms of particle size and structure. Likewise, the formation of the anatase phase under these synthesis conditions was explained. - Highlights: • Synthesis of anatase TiO 2 nanoparticles by an acid assisted sol–gel method at mild conditions. • Microstructure characterization by XRD, TEM and Raman spectroscopy. • Observation of the formation and evolution of the anatase phase as acetic acid was increased. • Anatase thermal stability up to 600 °C and band gap range between 3.2 and 3.5 eV. • A simplified method which can be considered as a green chemistry process

  18. Refinement of La1.5Ba1.5Cu3O7-x from a Twinned Crystal

    DEFF Research Database (Denmark)

    Hjorth, Michael

    1996-01-01

    The structure of the title compound (barium copper lanthanum oxide, Ba1.50Cu3La1.50O6.66) has been refined from a twinned crystal using single-crystal methods. The results of the present investigation show lower standard deviations than the results of earlier powder diffraction refinements...

  19. Marine sediment pore-water profiles of phosphate d18O using a refined micro-extraction

    DEFF Research Database (Denmark)

    Goldhammer, Tobias; Max, Thomas; Brunner, Benjamin

    2011-01-01

    and small amounts of marine porewaters available for analysis. We obtained porewater profiles of Pi oxygen isotopes using a refined protocol based on the original micro-extraction designed by Colman (2002). This refined and customized method allows the conversion of ultra-low quantities (0.5 – 1 μmol...

  20. Stable grid refinement and singular source discretization for seismic wave simulations

    Energy Technology Data Exchange (ETDEWEB)

    Petersson, N A; Sjogreen, B

    2009-10-30

    An energy conserving discretization of the elastic wave equation in second order formulation is developed for a composite grid, consisting of a set of structured rectangular component grids with hanging nodes on the grid refinement interface. Previously developed summation-by-parts properties are generalized to devise a stable second order accurate coupling of the solution across mesh refinement interfaces. The discretization of singular source terms of point force and point moment tensor type are also studied. Based on enforcing discrete moment conditions that mimic properties of the Dirac distribution and its gradient, previous single grid formulas are generalized to work in the vicinity of grid refinement interfaces. These source discretization formulas are shown to give second order accuracy in the solution, with the error being essentially independent of the distance between the source and the grid refinement boundary. Several numerical examples are given to illustrate the properties of the proposed method.

  1. Application of a dynamic-nanoindentation method to analyze the local structure of an Fe-18 at.% Gd cast alloy

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong; Baik, Youl [Dept. of Materials Science and Technology, Dankook University, Cheonan(Korea, Republic of); Moon, Byung M. [Liquid Processing and Casting Technology R and D Group, KITECH, Incheon (Korea, Republic of); Sohn, Dong Seong [Nuclear Engineering Department, UNIST, Ulsan (Korea, Republic of)

    2017-04-15

    A dynamic nanoindentation method was applied to study an Fe-18 at.% Gd alloy as a neutron-absorbing material prepared by vacuum arc-melting and cast in a mold. The Fe-18 at.% Gd cast alloy had a microstructure with matrix phases and an Fe-rich primary dendrite of Fe9Gd. Rietveld refinement of the X-ray spectra showed that the Fe-18 at.% Gd cast alloy consisted of 35.84 at.% Fe3Gd, 6.58 at.% Fe5Gd, 16.22 at.% Fe9Gd, 1.87 at.% Fe2Gd, and 39.49 at.% β-Fe17Gd2. The average nanohardness of the primary dendrite phase and the matrix phases were 8.7 GPa and 9.3 GPa, respectively. The fatigue limit of the matrix phase was approximately 37% higher than that of the primary dendrite phase. The dynamic nanoindentation method is useful for identifying local phases and for analyzing local mechanical properties.

  2. Region-of-interest volumetric visual hull refinement

    KAUST Repository

    Knoblauch, Daniel; Kuester, Falko

    2010-01-01

    This paper introduces a region-of-interest visual hull refinement technique, based on flexible voxel grids for volumetric visual hull reconstructions. Region-of-interest refinement is based on a multipass process, beginning with a focussed visual

  3. Grain Refinement of Permanent Mold Cast Copper Base Alloys

    Energy Technology Data Exchange (ETDEWEB)

    M.Sadayappan; J.P.Thomson; M.Elboujdaini; G.Ping Gu; M. Sahoo

    2005-04-01

    Grain refinement is a well established process for many cast and wrought alloys. The mechanical properties of various alloys could be enhanced by reducing the grain size. Refinement is also known to improve casting characteristics such as fluidity and hot tearing. Grain refinement of copper-base alloys is not widely used, especially in sand casting process. However, in permanent mold casting of copper alloys it is now common to use grain refinement to counteract the problem of severe hot tearing which also improves the pressure tightness of plumbing components. The mechanism of grain refinement in copper-base alloys is not well understood. The issues to be studied include the effect of minor alloy additions on the microstructure, their interaction with the grain refiner, effect of cooling rate, and loss of grain refinement (fading). In this investigation, efforts were made to explore and understand grain refinement of copper alloys, especially in permanent mold casting conditions.

  4. Grain refinement of AZ31 magnesium alloy by electromagnetic ...

    Indian Academy of Sciences (India)

    Low-frequency electromagnetic field; AZ31 magnesium alloy; Al4C3; grain refinement. Abstract. The effects of electromagnetic stirring and Al4C3 grain refiner on the grain refinement of semicontinuously cast AZ31 magnesium alloy were discussed in this investigation. The results indicate that electromagnetic stirring has an ...

  5. Neutrosophic Refined Similarity Measure Based on Cosine Function

    Directory of Open Access Journals (Sweden)

    Said Broumi

    2014-12-01

    Full Text Available In this paper, the cosine similarity measure of neutrosophic refined (multi- sets is proposed and its properties are studied. The concept of this cosine similarity measure of neutrosophic refined sets is the extension of improved cosine similarity measure of single valued neutrosophic. Finally, using this cosine similarity measure of neutrosophic refined set, the application of medical diagnosis is presented.

  6. Local mesh refinement for incompressible fluid flow with free surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Terasaka, H.; Kajiwara, H.; Ogura, K. [Tokyo Electric Power Company (Japan)] [and others

    1995-09-01

    A new local mesh refinement (LMR) technique has been developed and applied to incompressible fluid flows with free surface boundaries. The LMR method embeds patches of fine grid in arbitrary regions of interest. Hence, more accurate solutions can be obtained with a lower number of computational cells. This method is very suitable for the simulation of free surface movements because free surface flow problems generally require a finer computational grid to obtain adequate results. By using this technique, one can place finer grids only near the surfaces, and therefore greatly reduce the total number of cells and computational costs. This paper introduces LMR3D, a three-dimensional incompressible flow analysis code. Numerical examples calculated with the code demonstrate well the advantages of the LMR method.

  7. MICROARRAY IMAGE GRIDDING USING GRID LINE REFINEMENT TECHNIQUE

    Directory of Open Access Journals (Sweden)

    V.G. Biju

    2015-05-01

    Full Text Available An important stage in microarray image analysis is gridding. Microarray image gridding is done to locate sub arrays in a microarray image and find co-ordinates of spots within each sub array. For accurate identification of spots, most of the proposed gridding methods require human intervention. In this paper a fully automatic gridding method which enhances spot intensity in the preprocessing step as per a histogram based threshold method is used. The gridding step finds co-ordinates of spots from horizontal and vertical profile of the image. To correct errors due to the grid line placement, a grid line refinement technique is proposed. The algorithm is applied on different image databases and results are compared based on spot detection accuracy and time. An average spot detection accuracy of 95.06% depicts the proposed method’s flexibility and accuracy in finding the spot co-ordinates for different database images.

  8. Protein homology model refinement by large-scale energy optimization.

    Science.gov (United States)

    Park, Hahnbeom; Ovchinnikov, Sergey; Kim, David E; DiMaio, Frank; Baker, David

    2018-03-20

    Proteins fold to their lowest free-energy structures, and hence the most straightforward way to increase the accuracy of a partially incorrect protein structure model is to search for the lowest-energy nearby structure. This direct approach has met with little success for two reasons: first, energy function inaccuracies can lead to false energy minima, resulting in model degradation rather than improvement; and second, even with an accurate energy function, the search problem is formidable because the energy only drops considerably in the immediate vicinity of the global minimum, and there are a very large number of degrees of freedom. Here we describe a large-scale energy optimization-based refinement method that incorporates advances in both search and energy function accuracy that can substantially improve the accuracy of low-resolution homology models. The method refined low-resolution homology models into correct folds for 50 of 84 diverse protein families and generated improved models in recent blind structure prediction experiments. Analyses of the basis for these improvements reveal contributions from both the improvements in conformational sampling techniques and the energy function.

  9. Formal language theory: refining the Chomsky hierarchy.

    Science.gov (United States)

    Jäger, Gerhard; Rogers, James

    2012-07-19

    The first part of this article gives a brief overview of the four levels of the Chomsky hierarchy, with a special emphasis on context-free and regular languages. It then recapitulates the arguments why neither regular nor context-free grammar is sufficiently expressive to capture all phenomena in the natural language syntax. In the second part, two refinements of the Chomsky hierarchy are reviewed, which are both relevant to the extant research in cognitive science: the mildly context-sensitive languages (which are located between context-free and context-sensitive languages), and the sub-regular hierarchy (which distinguishes several levels of complexity within the class of regular languages).

  10. Local adaptive mesh refinement for shock hydrodynamics

    International Nuclear Information System (INIS)

    Berger, M.J.; Colella, P.; Lawrence Livermore Laboratory, Livermore, 94550 California)

    1989-01-01

    The aim of this work is the development of an automatic, adaptive mesh refinement strategy for solving hyperbolic conservation laws in two dimensions. There are two main difficulties in doing this. The first problem is due to the presence of discontinuities in the solution and the effect on them of discontinuities in the mesh. The second problem is how to organize the algorithm to minimize memory and CPU overhead. This is an important consideration and will continue to be important as more sophisticated algorithms that use data structures other than arrays are developed for use on vector and parallel computers. copyright 1989 Academic Press, Inc

  11. A refined index of model performance: a rejoinder

    Science.gov (United States)

    Legates, David R.; McCabe, Gregory J.

    2013-01-01

    Willmott et al. [Willmott CJ, Robeson SM, Matsuura K. 2012. A refined index of model performance. International Journal of Climatology, forthcoming. DOI:10.1002/joc.2419.] recently suggest a refined index of model performance (dr) that they purport to be superior to other methods. Their refined index ranges from − 1.0 to 1.0 to resemble a correlation coefficient, but it is merely a linear rescaling of our modified coefficient of efficiency (E1) over the positive portion of the domain of dr. We disagree with Willmott et al. (2012) that dr provides a better interpretation; rather, E1 is more easily interpreted such that a value of E1 = 1.0 indicates a perfect model (no errors) while E1 = 0.0 indicates a model that is no better than the baseline comparison (usually the observed mean). Negative values of E1 (and, for that matter, dr McCabe [Legates DR, McCabe GJ. 1999. Evaluating the use of “goodness-of-fit” measures in hydrologic and hydroclimatic model validation. Water Resources Research 35(1): 233-241.] and Schaefli and Gupta [Schaefli B, Gupta HV. 2007. Do Nash values have value? Hydrological Processes 21: 2075-2080. DOI: 10.1002/hyp.6825.]. This important discussion focuses on the appropriate baseline comparison to use, and why the observed mean often may be an inadequate choice for model evaluation and development. 

  12. An adaptive grid refinement strategy for the simulation of negative streamers

    International Nuclear Information System (INIS)

    Montijn, C.; Hundsdorfer, W.; Ebert, U.

    2006-01-01

    The evolution of negative streamers during electric breakdown of a non-attaching gas can be described by a two-fluid model for electrons and positive ions. It consists of continuity equations for the charged particles including drift, diffusion and reaction in the local electric field, coupled to the Poisson equation for the electric potential. The model generates field enhancement and steep propagating ionization fronts at the tip of growing ionized filaments. An adaptive grid refinement method for the simulation of these structures is presented. It uses finite volume spatial discretizations and explicit time stepping, which allows the decoupling of the grids for the continuity equations from those for the Poisson equation. Standard refinement methods in which the refinement criterion is based on local error monitors fail due to the pulled character of the streamer front that propagates into a linearly unstable state. We present a refinement method which deals with all these features. Tests on one-dimensional streamer fronts as well as on three-dimensional streamers with cylindrical symmetry (hence effectively 2D for numerical purposes) are carried out successfully. Results on fine grids are presented, they show that such an adaptive grid method is needed to capture the streamer characteristics well. This refinement strategy enables us to adequately compute negative streamers in pure gases in the parameter regime where a physical instability appears: branching streamers

  13. Control of electrolytic refinement of silver by atomic absorption method

    International Nuclear Information System (INIS)

    Kulish, N.G.; Burylev, B.P.

    1983-01-01

    Results of atomic absorption determination of 18 elements: Fe, Cu, Zn, Cd, Bi, Ga, In, Ca, Mg, K, Na, Sb, Te, Ni, Co, Cr, Mn, Pb in silver and electrolytes are presented. When determining impurities in silver the basis has been separated by the extraction of O-isopropyl-N-ethyl thiocarbamate in the 1M HN0 3 medium. Optimum measuring conditions and the range of linear dependence between concentration and atomic absorption value are given

  14. SFESA: a web server for pairwise alignment refinement by secondary structure shifts.

    Science.gov (United States)

    Tong, Jing; Pei, Jimin; Grishin, Nick V

    2015-09-03

    Protein sequence alignment is essential for a variety of tasks such as homology modeling and active site prediction. Alignment errors remain the main cause of low-quality structure models. A bioinformatics tool to refine alignments is needed to make protein alignments more accurate. We developed the SFESA web server to refine pairwise protein sequence alignments. Compared to the previous version of SFESA, which required a set of 3D coordinates for a protein, the new server will search a sequence database for the closest homolog with an available 3D structure to be used as a template. For each alignment block defined by secondary structure elements in the template, SFESA evaluates alignment variants generated by local shifts and selects the best-scoring alignment variant. A scoring function that combines the sequence score of profile-profile comparison and the structure score of template-derived contact energy is used for evaluation of alignments. PROMALS pairwise alignments refined by SFESA are more accurate than those produced by current advanced alignment methods such as HHpred and CNFpred. In addition, SFESA also improves alignments generated by other software. SFESA is a web-based tool for alignment refinement, designed for researchers to compute, refine, and evaluate pairwise alignments with a combined sequence and structure scoring of alignment blocks. To our knowledge, the SFESA web server is the only tool that refines alignments by evaluating local shifts of secondary structure elements. The SFESA web server is available at http://prodata.swmed.edu/sfesa.

  15. Grain refinement of an AZ63B magnesium alloy by an Al-1C master alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yichuan Pan; Xiangfa Liu; Hua Yang [The Key Lab. of Liquid Structure and Heredity of Materials, Shandong Univ., Jinan (China)

    2005-12-01

    In order to develop a refiner of Mg-Al alloys, an Al-1C (in wt.%) master alloy was synthesized using a casting method. The microstructure and grain-refining performance of the Al-1C master alloy were investigated using X-ray diffraction (XRD), electron probe microanalysis (EPMA) and a grain-refining test. The microstructure of the Al-1C master alloy is composed of {alpha}-Al solid solution, Al{sub 4}C{sub 3} particles, and graphite phases. After grain refinement of AZ63B alloy by the Al-1C master alloy, the mean grain size reached a limit when 2 wt.% Al-C master alloy was added at 800 C and held for 20 min in the melt before casting. The minimum mean grain size is approximately 48 {mu}m at the one-half radius of the ingot and is about 17% of that of the unrefined alloy. The Al-1C master alloy results in better grain refinement than C{sub 2}Cl{sub 6} and MgCO{sub 3} carbon-containing refiners. (orig.)

  16. Preparation of Al-Ti-B grain refiner by SHS technology

    International Nuclear Information System (INIS)

    Nikitin, V.I.; Wanqi, J.I.E.; Kandalova, E.G.; Makarenko, A.G.; Yong, L.

    2000-01-01

    Since the discovery of the grain refinement effect of aluminum by titanium, especially with the existence of B or C in 1950, grain refiners are widely accepted in industry for microstructure control of aluminum alloys. Research on this topic is to obtain the highest grain refinement efficiency with the lowest possible addition of master alloy. It is widely accepted that the morphology and size of TiAl 3 particles, which are known as heterogeneous nucleation centers, are important factors deterring the grain refinement efficiency. Fine TiAl 3 particles are favorable. The grain refinement process shows a heredity phenomenon, which means that structural information from initial materials transfers through a melt to the final product. It is important to find the connection between microstructural parameters of the master alloy and the final product. To improve the quality of Al-Ti-B master alloys for the use as a grain refiner, a new method based on SHS (self-propagating high-temperature synthesis) technology has been developed in Samara State Technical University to produce the master alloys. SHS, as a new method for preparation of materials, was first utilized by Merzhanov in 1967. This method uses the energy from highly exothermic reactions to sustain the chemical reaction in a combustion wave. The advantages of SHS include simplicity, low energy requirement, and higher product purity. Because SHS reactions can take place between elemental reactants, it is easy to control product composition. The purposes of this investigation were to fabricate an SHS Al-5%Ti-1%B master alloy, to analyze its structure and to test its grain refining performance

  17. Pacific Basin Heavy Oil Refining Capacity

    Directory of Open Access Journals (Sweden)

    David Hackett

    2013-02-01

    Full Text Available The United States today is Canada’s largest customer for oil and refined oil products. However, this relationship may be strained due to physical, economic and political influences. Pipeline capacity is approaching its limits; Canadian oil is selling at substantive discounts to world market prices; and U.S. demand for crude oil and finished products (such as gasoline, has begun to flatten significantly relative to historical rates. Lower demand, combined with increased shale oil production, means U.S. demand for Canadian oil is expected to continue to decline. Under these circumstances, gaining access to new markets such as those in the Asia-Pacific region is becoming more and more important for the Canadian economy. However, expanding pipeline capacity to the Pacific via the proposed Northern Gateway pipeline and the planned Trans Mountain pipeline expansion is only feasible when there is sufficient demand and processing capacity to support Canadian crude blends. Canadian heavy oil requires more refining and produces less valuable end products than other lighter and sweeter blends. Canadian producers must compete with lighter, sweeter oils from the Middle East, and elsewhere, for a place in the Pacific Basin refineries built to handle heavy crude blends. Canadian oil sands producers are currently expanding production capacity. Once complete, the Northern Gateway pipeline and the Trans Mountain expansion are expected to deliver an additional 500,000 to 1.1 million barrels a day to tankers on the Pacific coast. Through this survey of the capacity of Pacific Basin refineries, including existing and proposed facilities, we have concluded that there is sufficient technical capacity in the Pacific Basin to refine the additional Canadian volume; however, there may be some modifications required to certain refineries to allow them to process Western Canadian crude. Any additional capacity for Canadian oil would require refinery modifications or

  18. The European refining and distribution industry at the 2010 vista

    International Nuclear Information System (INIS)

    Lacour, J.J.; Tessmer, G.; Ward, I.

    1998-01-01

    Oil company chairmen belonging to the AFTP, DGMK and IP associations met together to debate about the future of the European refining industry. The following topics were discussed: is it the end of the refining crisis? Which uncertainties will have to be met? What is the situation of petroleum products supply and demand? What are the consumers' expectations? How to face the environmental constraints? Which future for the refining activities in Europe? Seven round-tables took place with the following themes: the factors of uncertainty in the future of refining activities, the petroleum products supply and demand (automotive fuels, fuel oils, lubricants), the refining activities and the supply of consumers (service stations and supermarkets), the situation of the European petroleum policy, the European refining industry and the public regulations (development of more efficient environmental approaches), the impact of environmental constraints and the technical solutions, and the future of the refining industry. (J.S.)

  19. Technological studies on uranium refining at nuclear materials authority, Egypt

    International Nuclear Information System (INIS)

    Mohammed, H.S.

    1997-01-01

    In 1992 nuclear materials authority (NMA) took a decision to establish yellow cake refining. Unit so as to study refining of El-Atshan yellow cake which recently produced by ion-exchange pilot plant, production sector. The research studies followed the conventional refining rout to produce nuclear grade UO 3 . This implies investigations on some common solvents to refine the cake viz. tri alkyl phosphates, tri alkyl phosphine oxides, dialkyl phosphoric acid as well as high-molecular weight long-chain tertiary amines. Moreover, non-conventional refining process has also been presented depending on the selectivity of uranyl ion to be dissolved by carbonate and to be precipitated by hydrogen peroxide. Most of the proposed processes were found feasible to refine El-Atshan yellow cake. however, the non- conventional refining process appears to be the most promising, owing to its superior performance and economy

  20. Zeta potential study of Sb2S3 nanoparticles synthesized by a facile polyol method in various surfactants

    Science.gov (United States)

    Saxena, Monika; Okram, Gunadhor Singh

    2018-05-01

    In the present work, we report the successful synthesis of stibnite Sb2S3 nanoparticles (NPs) by a facile polyol method using various surfactant. The structural and optical properties were investigated by X-ray diffraction (XRD), Raman spectroscopy and Zeta potential. Rietveld refinement of XRD data confirms the single phase orthorhombic crystal structure of stibnite Sb2S3. Presence of six obvious Raman modes further confirmed their stoichiometric formation. Effect of different surfactants on the surface charge of Sb2S3 NPs was studied using Zeta potential measurement in deionized water at different pH values. They reveal that these NPs are more stable when it was synthesized in presence of EDTA than that of CTAB or without surfactant samples with high zeta potential. The isoelectronic point was found at pH = 6.4 for pure sample, 3.5 and 7.2 for CTAB and not found for EDTA Sb2S3 samples. This information can be useful for many industrial applications like pharmaceuticals, ceramics, waste water treatment and medicines.