947 resultados para Cr^3
Resumo:
X-ray fluorescence (XRF) core-scanning is a fast and nondestructive technique to assess elemental variations of unprocessed sediments. However, although the exposure time of XRF-scanning directly affects the scanning counts and total measurement time, only a few studies have considered the influence of exposure time during the scan. How to select an optimal exposure time to achieve reliable results and reduce the total measurement time is an important issue. To address this question, six geological reference materials from the Geological Survey of Japan (JLK-1, JMS-1, JMS-2, JSD-1, JSD-2, and JSD-3) were scanned by the Itrax-XRF core scanner using the Mo- and the Cr-tube with different exposure times to allow a comparison of scanning counts with absolute concentrations. The regression lines and correlation coefficients of elements that are generally used in paleoenvironmental studies were examined for the different exposure times and X-ray tubes. The results show that for those elements with relatively high concentrations or high detectability, the correlation coefficients are higher than 0.90 for all exposure times. In contrast, for the low detectability or low concentration elements, the correlation coefficients are relatively low, and improve little with increased exposure time. Therefore, we suggest that the influence of different exposure times is insignificant for the accuracy of the measurements. Thus, caution must be taken when interpreting the results of elements with low detectability, even when the exposure times are long and scanning counts are reasonably high.
Resumo:
<p>We report calculations of energy levels and radiative rates (A-values) for transitions in Cr-like Co IV and Ni V. The quasi-relativistic Hartree-Fock (QRHF) code is adopted for calculating the data although grasp (general-purpose relativistic atomic structure package) and flexible atomic code (fac) have also been employed for comparison purposes. No radiative rates are available in the literature to compare with our results, but our calculated energies are in close agreement with those compiled by NIST for a majority of the levels. However, there are discrepancies for a few levels of up to 3%. The A-values are listed for all significantly contributing E1, E2 and M1 transitions, and the corresponding lifetimes reported, although unfortunately no previous theoretical or experimental results exist to compare with our data.</p>
Resumo:
La normalizacin facilita la comunicacin y permite el intercambio de informacin con cualquier institucin nacional o internacional. Este objetivo es posible a travs de los formatos de comunicacin para intercambio de informacin automatizada como CEPAL, MARC., FCC.La Escuela de Bibliotecologa, Documentacin e Informacin de la Universidad Nacional utiliza el software MICROISIS en red para la enseanza. Las bases de datos que se disean utilizan el formato MARC y para la descripcin bibliogrfica las RCAA2.Se presenta la experiencia con la base de datos I&D sobre desarrollo rural, presentando la Tabla de Definicin de Campos, la hoja de trabajo, el formato de despliegue y Tabla de seleccin de Campos.
Resumo:
En el campo bibliotecolgico para desarrollar instrumentos de trabajo que nos permitan comunicarnos con las dems unidades y clientes de informacin, debemos pensar en normalizar nuestros procesos.Normalizar, en el sentido ms amplio, significa seguir reglas que hagan un registro uniforme en cualquier lugar del mundo. Esto se logra mediante la aplicacin de cdigos y normas que han sido aceptadas internacionalmente por los organismos creados para este fin.El valor de la normalizacin estriba en evitar la duplicacin de los esfuerzos de la catalogacin en las diferentes unidades de informacin documental y facilitar el intercambio de datos bibliogrficos tan pronto como sea posible. Tambin, cosiste en darle al cliente la posibilidad de localizar la informacin en un a forma homognea que obvie las barreras idiomticas.
Resumo:
The physicochemical characteristics of three Brazilian pears were investigated using elemental analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD) and studies of Cr(III) biosorption based on adsorption isotherms. Adsorption of Cr(III) by in natura peat from Santo Amaro das Brotas (Sergipe State) was much greater than by peats from either Ribeirao Preto (So Paulo State) or Itabaiana (Sergipe State), with adsorption capacities (q) of 4.90 +/- 0.01, 1.70 +/- 0.01 and 1.40 +/- 0.01 mgg (1), respectively. Pre-treatments with HCl and NaOH + HCl reduced adsorption by the Santo Amaro clas Brotas peat, showing that adsorption efficiency was associated with the amount of organic matter present. Conversely, increase in the mineral content following pre-treatment increased adsorption of Cr(III) by the Ribeirao Preto and Itabaiana peats. Highest adsorption (retention >95.0%) was achieved at equilibrium pH 4.0 using the Santo Amaro das Brotas peat. Experimental data for the adsorption of Cr(III) from aqueous solution onto this peat were fitted to the Langmuir equation, from which an equilibrium adsorption capacity, q(max), of 5.60 mgg(-1) was obtained, which was close to the experimentally determined value. (c) 2008 Elsevier B.V. All rights reserved.
Resumo:
257 p.
Resumo:
Presentamos el clculo de las funciones seno y coseno para los ngulos mltiplos de 3 medidos en grados. Se hace uso de las propiedades que presentan los tringulos respectivos. Al final del trabajo se resumen las frmulas obtenidas.
Resumo:
Este documento presenta datos, informacin y anlisis propios de un diagnstico que se elabora para disear un plan regulador cantonal de Corredores, Costa Rica. Tambin presenta los retos inmediatos y estratgicos que enfrentan los pobladores de la isla individual y colectivamente. Incluye mltiples partes: un diagnstico biofsico que incluye mapas de uso del suelo. Una evaluacin de los recursos biolgicos, amenazas naturales, la orografa y topografa, la geologa, capacidad de uso del suelo y sus potencialidades y vulnerabilidades. Tambin incluye un diagnstico socio-econmico (poblacin, vivienda, empleo, actividad productiva y transporte) e historia de la ocupacin del cantn.
Resumo:
TiSiC-Cr coatings, with Cr and Si as additional elements, were deposited on Si, C 45 and 316 L steel substrates via cathodic arc evaporation. Two series of coatings with thicknesses in the range of 3.63.9 m were produced, using either CH4 or C2H2 as carbon containing gas. For each series, different coatings were prepared by varying the carbon rich gas flow rate between 90 and 130 sccm, while maintaining constant cathode currents (110 and 100 A at TiSi and Cr cathodes, respectively), substrate bias (200 V) and substrate temperature (320 C). The coatings were analyzed for their mechanical characteristics (hardness, adhesion) and tribological performance (friction, wear), along with their elemental and phase composition, chemical bonds, crystalline structure and cross-sectional morphology. The coatings were found to be formed with nano-scale composite structures consisting of carbide crystallites (grain size of 3.18.2 nm) and amorphous hydrogenated carbon. The experimental results showed significant differences between the two coating series, where the films formed from C2H2 exhibited markedly superior characteristics in terms of microstructure, morphology, hardness, friction behaviour and wear resistance. For the coatings prepared using CH4, the measured values of crystallite size, hardness, friction coefficient and wear rate were in the ranges of 7.28.2 nm, 2630 GPa, 0.30.4 and 2.14.8 106 mm3 N1 m1, respectively, while for the coatings grown in C2H2, the values of these characteristics were found to be in the ranges of 3.13.7 nm, 4145 GPa, 0.10.2 and 1.43.0 106 mm3 N1 m1, respectively. Among the investigated coatings, the one produced using C2H2 at the highest flow rate (130 sccm) exhibited the highest hardness (45.1 GPa), the lowest friction coefficient (0.10) and the best wear resistance (wear rate of 1.4 106 mm3 N1 m1).
Resumo:
Abstract. The study developed builds a curriculum proposal based on adaptive skills for early stimulation of children from 0 to 3 years with cognitive disabilities as a final requirement for graduation from the Masters in Education with Emphasis on Development The proposal intends to improve the coherence, relevance and effectiveness of special education offered to students with special educational needs, specifically with cognitive impairment conditions, from early stimulation with a population of 0 to 3 years. The main objective of the study rises from the working context of the study: the individual needs of special education teachers and their students.
Resumo:
No Brasil por muitos anos o ensino de Geografia se mostrou tradicional, e apesar da evoluo de ferramentas educacionais e de tecnologias na rea do ensino nas ltimas dcadas, ainda notrio que em muitas escolas, principalmente nas pblicas, as prticas e metodologias que no esto adequadas s necessidades vigentes diante da globalizao e do sistema. O C.E. Maria Helena Rocha uma escola da rede pblica estadual localizada na cidade de So Lus MA. Este trabalho fruto das atividades exercidas na referida escola com a turma 303 do 3 ano do ensino mdio atravs do Programa Institucional de Bolsas de Iniciao a Docncia PIBID em Geografia, e busca atravs dos fenmenos observar as prticas e metodologias de ensino visando criar alternativas para dar suporte ao ensino e a aprendizagem da Geografia. Durante os perodos de observao foi possvel identificar que a metodologia se pauta na e utilizao do livro didtico e elaborao de resumos de textos do mesmo. De acordo com a professora falta, de alguma forma, motivao nos discentes, pois a turma no acompanha a contento o planejamento das aulas pela docente. A escola no dispe de recursos necessrios e isso inviabiliza, segundo a professora, o desenvolvimento de atividades diferentes, tendo como agravante a inexistncia de equipamentos/recursos didticos ou so de uso restrito.
Resumo:
A low temperature synthesis method based on the decomposition of urea at 90C in water has been developed to synthesise fraipontite. This material is characterised by a basal reflection 001 at 7.44 . The trioctahedral nature of the fraipontite is shown by the presence of a 06l band around 1.54 , while a minor band around 1.51 indicates some cation ordering between Zn and Al resulting in Al-rich areas with a more dioctahedral nature. TEM and IR indicate that no separate kaolinite phase is present. An increase in the Al content however, did result in the formation of some SiO2 in the form of quartz. Minor impurities of carbonate salts were observed during the synthesis caused by to the formation of CO32- during the decomposition of urea.
