Página 6 dos resultados de 15310 itens digitais encontrados em 0.006 segundos

Preservação digital:análise dos periódicos da base BRAPCI.

Dias, Rafael Cobbe
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Relatório
Português
Relevância na Pesquisa
26.232854%
A preservação digital garante a duração dos objetos digitais por um longo período de tempo, sua aplicação deve ser criteriosa e baseada em estratégias confiáveis. O trabalho faz uma reflexão sobre as estratégias de preservação digital que podem ser aplicadas nos periódicos científicos digitais. Foram analisados individualmente os periódicos da área de Ciência da Informação indexados na Base de Dados da BRAPCI, bem como as tecnologias de preservação digital utilizadas, a fim de levantar as estratégias de preservação existentes. Com base na fundamentação teórica de preservação digital foram identificadas as estratégias existentes com o intuito de compará-las com as que são utilizadas nos periódicos selecionados. Essas tecnologias têm funções distintas, o PDF/A pode ser usado como formato padrão de preservação; o uso do DOI ajuda na recuperação dos objetos digitais; o LOCKSS garante a manutenção dos documentos eletrônicos.

Acrobat Pro 9

Adobe
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Software
Português
Relevância na Pesquisa
26.232854%
Software que permite a criação e edição de arquivos PDF.

Pdf´s interactivos

Domingos, Hugo
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Outros
Publicado em 29/01/2009 Português
Relevância na Pesquisa
26.232854%
Este guião de apoio à formação tem como objectivo apoiar docentes na (1) utilização de funcionalidades avançadas do Adobe Acrobat Professional e (2) produção de documentos interactivos com fins educativos.

Desktop document delivery using portable document format (PDF) files and the Web.

Shipman, J P; Gembala, W L; Reeder, J M; Zick, B A; Rainwater, M J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1998 Português
Relevância na Pesquisa
26.232854%
Desktop access to electronic full-text literature was rated one of the most desirable services in a client survey conducted by the University of Washington Libraries. The University of Washington Health Sciences Libraries (UW HSL) conducted a ten-month pilot test from August 1996 to May 1997 to determine the feasibility of delivering electronic journal articles via the Internet to remote faculty. Articles were scanned into Adobe Acrobat Portable Document Format (PDF) files and delivered to individuals using Multipurpose Internet Mail Extensions (MIME) standard e-mail attachments and the Web. Participants retrieved scanned articles and used the Adobe Acrobat Reader software to view and print files. The pilot test required a special programming effort to automate the client notification and file deletion processes. Test participants were satisfied with the pilot test despite some technical difficulties. Desktop delivery is now offered as a routine delivery method from the UW HSL.

Crystallization and preliminary X-ray crystallographic analysis of peptide deformylase (PDF) from Bacillus cereus in ligand-free and actinonin-bound forms

Park, Joon Kyu; Moon, Jin Ho; Kim, Jae-Hong; Kim, Eunice EunKyeong
Fonte: International Union of Crystallography Publicador: International Union of Crystallography
Tipo: Artigo de Revista Científica
Publicado em 24/12/2004 Português
Relevância na Pesquisa
26.232854%
Peptide deformylase (PDF) from B. cereus has been overexpressed, purified and crystallized in ligand-free and actinonin-bound forms. Diffraction data have been collected from these crystals to 1.7 and 2.0 Å resolution, respectively.

Enhanced Techniques for PDF Image Segmentation and Text Extraction

Sasirekha, D.; Chandra, E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/10/2012 Português
Relevância na Pesquisa
26.408977%
Extracting text objects from the PDF images is a challenging problem. The text data present in the PDF images contain certain useful information for automatic annotation, indexing etc. However variations of the text due to differences in text style, font, size, orientation, alignment as well as complex structure make the problem of automatic text extraction extremely difficult and challenging job. This paper presents two techniques under block-based classification. After a brief introduction of the classification methods, two methods were enhanced and results were evaluated. The performance metrics for segmentation and time consumption are tested for both the models.; Comment: 5 pages, 5 figures

PDF Fits at HERA

Cooper-Sarkar, A M
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/12/2011 Português
Relevância na Pesquisa
26.408977%
The HERAPDF1.0 PDF set, which was an NLO QCD analysis based on H1 and ZEUS combined inclusive cross section data from HERA-I, has been updated to HERAPDF1.5 by including preliminary inclusive cross section data from HERA-II running. Studies have also been made by adding various other HERA data sets: combined charm data, combined low energy run data and H1 and ZEUS jet data. These data give information on the treatment of charm and the charm quark mass and on the value of $\alpha_s(M_Z)$. The PDF analysis has also been extended to NNLO. The PDFs give a good description of Tevatron and early LHC data.; Comment: On behalf of ZEUS and H1 collaborations, 6 pages, 6 figures. To appear in the Proceedings of the 2011 Europhysics Conference on High Energy Physics, HEP 2011, July 2011, Grenoble, France

Hessian PDF reweighting meets the Bayesian methods

Paukkunen, Hannu; Zurita, Pia
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/08/2014 Português
Relevância na Pesquisa
26.408977%
We discuss the Hessian PDF reweighting - a technique intended to estimate the effects that new measurements have on a set of PDFs. The method stems straightforwardly from considering new data in a usual $\chi^2$-fit and it naturally incorporates also non-zero values for the tolerance, $\Delta\chi^2>1$. In comparison to the contemporary Bayesian reweighting techniques, there is no need to generate large ensembles of PDF Monte-Carlo replicas, and the observables need to be evaluated only with the central and the error sets of the original PDFs. In spite of the apparently rather different methodologies, we find that the Hessian and the Bayesian techniques are actually equivalent if the $\Delta\chi^2$ criterion is properly included to the Bayesian likelihood function that is a simple exponential.; Comment: Transcription of the talk given in DIS2014 conference

Lagrangian Investigation of Auto-ignition in a Hydrogen Jet Flame in a Vitiated Co-flow: Animations of Particle Trajectories in Composition Space from PDF Model Calculations

Wang, Haifeng; Pope, Stephen B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/09/2007 Português
Relevância na Pesquisa
26.408977%
PDF model calculations have been performed of the Cabra lifted hydrogen flame in a vitiated co-flow. Particle trajectories are extracted from the Lagrangian particle method used to solve the modeled PDF equation. The particle trajectories in the mixture fraction-temperature plane reveal (at successive downstream locations): essentially inert mixing between the cold fuel jet and the hot co-flow; the auto-ignition of very lean particles; and, subsequent mixing and reaction, leading to near-equilibrium compositions. The purpose of this paper is to present animations of the particle trajectories obtained using different turbulent mixing models.; Comment: 5 pages, 3 figures. Video 1 (EMST) http://ecommons.library.cornell.edu/bitstream/1813/8237/2/LIFTED_H2_EMST_FUEL.mpg Video 2 (IEM) http://ecommons.library.cornell.edu/bitstream/1813/8237/4/LIFTED_H2_IEM_FUEL.mpg

Measuring the History of Cosmic Reionization using the 21-cm Difference PDF

Pan, Tony; Barkana, Rennan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/09/2012 Português
Relevância na Pesquisa
26.408977%
During cosmic reionization, the 21-cm brightness fluctuations were highly non-Gaussian, and complementary statistics can be extracted from the distribution of pixel brightness temperatures that are not derivable from the 21-cm power spectrum. One such statistic is the 21-cm difference PDF, the probability distribution function of the difference in the 21-cm brightness temperatures between two points, as a function of the distance between the points. Guided by 21-cm difference PDFs extracted from simulations, we perform a maximum likelihood analysis on mock observational data, and analyze the ability of present and future low-frequency radio array experiments to estimate the shape of the 21-cm difference PDF, and measure the history of cosmic reionization. We find that one-year data with an experiment such as the Murchison Wide-field Array should suffice for probing large scales during the mid-to-late stages of reionization, while a second-generation experiment should yield detailed measurements over a wide range of scales during most of the reionization era.; Comment: 11 pages, 17 figures. Submitted to MNRAS

Theoretical issues in PDF determination and associated uncertainties

The NNPDF Collaboration; Ball, Richard D.; Bertone, Valerio; Del Debbio, Luigi; Forte, Stefano; Guffanti, Alberto; Rojo, Juan; Ubiali, Maria
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.408977%
We study several sources of theoretical uncertainty in the determination of parton distributions (PDFs) which may affect current PDF sets used for precision physics at the Large Hadron Collider, and explain discrepancies between them. We consider in particular the use of fixed-flavor versus variable-flavor number renormalization schemes, higher twist corrections, and nuclear corrections. We perform our study in the framework of the NNPDF2.3 global PDF determination, by quantifying in each case the impact of different theoretical assumptions on the output PDFs. We also study in each case the implications for benchmark cross sections at the LHC. We find that the impact in a global fit of a fixed-flavor number scheme is substantial, the impact of higher twists is negligible, and the impact of nuclear corrections is moderate and circumscribed.; Comment: 18 pages, 13 figures. Final version, to be published in Phys. Lett. B. Tab. 2 added and Fig 13 updated. Several small improvements, including revised discussion of Ref.[24]

PDF uncertainties on the W boson mass measurement from the lepton transverse momentum distribution

Bozzi, Giuseppe; Citelli, Luca; Vicini, Alessandro
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.408977%
We study the charged current Drell-Yan process and we evaluate the proton parton densities uncertainties on the lepton transverse momentum distribution and their impact on the determination of the W-boson mass. We consider the global PDF sets CT10, MSTW2008CPdeut, NNPDF2.3, NNPDF3.0, MMHT2014, and apply the PDF4LHC recipe to combine the individual results, obtaining an uncertainty on MW that ranges between +-18 and +-24 MeV, depending on the final state, collider energy and kind. We discuss the dependence of the uncertainty on the acceptance cuts and the role of the individual parton densities in the final result. We remark that some PDF sets predict an uncertainty on MW of O(10 MeV); this encouraging result is spoiled, in the combined analysis of the different sets, by an important spread of the central values predicted by each group.; Comment: version accepted for publication on Phys.Rev.D, one figure and two references added

Multi-variate joint PDF for non-Gaussianities: exact formulation and generic approximations

Verde, Licia; Jimenez, Raul; Alvarez-Gaume, Luis; Heavens, Alan F.; Matarrese, Sabino
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.408977%
We provide an exact expression for the multi-variate joint probability distribution function of non-Gaussian fields primordially arising from local transformations of a Gaussian field. This kind of non-Gaussianity is generated in many models of inflation. We apply our expression to the non- Gaussianity estimation from Cosmic Microwave Background maps and the halo mass function where we obtain analytical expressions. We also provide analytic approximations and their range of validity. For the Cosmic Microwave Background we give a fast way to compute the PDF which is valid up to 7{\sigma} for fNL values (both true and sampled) not ruled out by current observations, which consists of expressing the PDF as a combination of bispectrum and trispectrum of the temperature maps. The resulting expression is valid for any kind of non-Gaussianity and is not limited to the local type. The above results may serve as the basis for a fully Bayesian analysis of the non-Gaussianity parameter.; Comment: Matches accepted verion to JCAP; conclusions unchaged, extra references added

Uncertainties on alpha_S in global PDF analyses and implications for predicted hadronic cross sections

Martin, A. D.; Stirling, W. J.; Thorne, R. S.; Watt, G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.408977%
We determine the uncertainty on the strong coupling alpha_S due to the experimental errors on the data fitted in global analysis of hard-scattering data, within the standard framework of leading-twist fixed-order collinear factorisation in the MSbar scheme, finding that alpha_S(M_Z^2) = 0.1202^{+0.0012}_{-0.0015} at next-to-leading order (NLO) and alpha_S(M_Z^2) = 0.1171^{+0.0014}_{-0.0014} at next-to-next-to-leading order (NNLO). We do not address in detail the issue of the additional theory uncertainty on alpha_S(M_Z^2), but an estimate is +/-0.003 at NLO and at most +/-0.002 at NNLO. We investigate the interplay between uncertainties on alpha_S and uncertainties on parton distribution functions (PDFs). We show, for the first time, how both these sources of uncertainty can be accounted for simultaneously in calculations of cross sections, and we provide eigenvector PDF sets with different fixed alpha_S values to allow further studies by the general user. We illustrate the application of these PDF sets by calculating cross sections for W, Z, Higgs boson and inclusive jet production at the Tevatron and LHC.; Comment: 45 pages, 17 figures. Grids can be found at http://projects.hepforge.org/mstwpdf/ and in LHAPDF V5.7.1. v2: version to appear in EPJC

PDF uncertainties in WH production at Tevatron

Nadolsky, P. M.; Sullivan, Z.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.408977%
We apply a method proposed by members of CTEQ Collaboration to estimate the uncertainty in associated $W$-Higgs boson production at Run II of the Tevatron due to our imprecise knowledge of parton distribution functions. We find that the PDF uncertainties for the signal and background rates are of the order 3%. The PDF uncertainties for the important statistical quantities (significance of the Higgs boson discovery, accuracy of the measurement of the (WH) cross section) are smaller (1.5%) due to the strong correlation of the signal and background.; Comment: A typo in Eq. (4) corrected

PDF fit in the fixed-flavor-number scheme

Alekhin, S.; Bluemlein, J.; Moch, S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/02/2012 Português
Relevância na Pesquisa
26.408977%
We discuss the heavy-quark contribution to deep inelastic scattering in the scheme with $n_f=3,4,5$ fixed flavors. Based on the recent ABM11 PDF analysis of world data for deep-inelastic scattering and fixed-target data for the Drell-Yan process with the running-mass definition for heavy quarks we show that fixed flavor number scheme is sufficient for describing the deep-inelastic-scattering data in the entire kinematic range. We compare with other PDF sets and comment on the implications for measuring the strong coupling constant $\alpha_s(M_Z)$.; Comment: 11 pages with 10 figures, to appear in the proceedings of the "Ringberg Workshop: New Trends in HERA Physics 2011", Ringberg Castle, Germany, 25-28 September, 2011

Uncertainties on alpha(S) in global PDF analyses and implications for predicted hadronic cross sections.

Martin, A. D.; Stirling, W. James; Thorne, Robert S.; Watt, G.
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Article; not applicable
Português
Relevância na Pesquisa
26.408977%
We determine the uncertainty on the strong coupling S due to the experimental errors on the data fitted in global analysis of hard-scattering data, within the standard framework of leading-twist fixed-order collinear factorisation in the MS scheme, finding that S(M2Z) = 0.1202+0.0012-0.0015 at next-to-leading order (NLO) and S(M2Z) = 0.1171+0.0014?0.0014 at next-to-next-to-leading order (NNLO). We do not address in detail the issue of the additional theory uncertainty on S(M2Z), but an estimate is ?0.003 at NLO and at most ?0.002 at NNLO. We investigate the interplay between uncertainties on S and uncertainties on parton distribution functions (PDFs). We show, for the first time, how both these sources of uncertainty can be accounted for simultaneously in calculations of cross sections, and we provide eigenvector PDF sets with different fixed S values to allow further studies by the general user. We illustrate the application of these PDF sets by calculating cross sections for W, Z, Higgs boson and inclusive jet production at the Tevatron and LHC.

Simulation of turbulent lifted methane jet flames: effects of air-dilution and transient flame propagation

Chen, Z.; Ruan, S.; Swaminathan, N.
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; accepted version
Português
Relevância na Pesquisa
26.408977%
This is the accepted manuscript. The final version will be available from Elsevier at: http://www.sciencedirect.com/science/article/pii/S001021801400279X.; Turbulent lifted methane jet flames with various air-dilution levels and a range of inlet velocities are simulated. A partially premixed combustion model based on premixed flamelets with presumed joint Probability Density Function (PDF) is used. The joint PDF is obtained using a copula to include the statistical correlation between mixture fraction, Z, and progress variable, c. The non-premixed combustion effect is included using a simple algebraic model. Both steady and unsteady RANS simulations are performed. The steady simulations show that the computed lift-off heights agree well with measured values for a wide range of jet velocities and air-dilution level. Both of the Z-c correlation and non-premixed combustion effects are found to be important to get the correct lift-off height. Their individual and combined effects are analysed systematically. The unsteady RANS results indicate that multi-stage flame development, namely the initial expansion, flame brush development, its propagation and final stabilisation, is captured reasonably well in simulations. The various stages of temporal evolution of the flame brush edge is captured well and the agreement with experimental measurements is good.; The supports of Cambridge Overseas Trust and China Scholarship Council are acknowledged by ZC. SR and NS acknowledge the support of MHI...

Modelling paradigms for MILD combustion

Minamoto, Y.; Swaminathan, N.
Fonte: Springer Publicador: Springer
Tipo: Article; accepted version
Português
Relevância na Pesquisa
26.408977%
This is the accepted manuscript. The final version is available from Springer at http://link.springer.com/article/10.1007%2Fs12572-014-0106-x.; Three-dimensional Direct Numerical Simulation (DNS) data of methane-air MILD combustion is analysed to study the behaviour of MILD reaction zones and to identify a suitable modelling paradigm for MILD combustion. The combustion kinetics in the DNS was modelled using a skeletal mechanism including non-unity Lewis number effects. The reaction zones under MILD conditions are highly convoluted and contorted resulting in their frequent interactions. This leads to combustion occurring over a large portion of the computational volume and giving an appearance of distributed combustion. Three paradigms, standard flamelets, mild flame elements (MIFEs) and PSR, along with a presumed PDF model are explored to estimate the mean and filtered reaction rate in MILD combustion. A beta function is used to estimate the presumed PDF shape. The variations of species mass fractions and reaction rate with temperature computed using thesemodels are compared to the DNS results. The PSR-based model is found to be appropriate, since the conditional averages obtained from the DNS agree well with those obtained using the PSR model. The flamelets model with MIFEs gives only a qualitative agreement because it does not include the effects of reaction zone interactions.; YM acknowledges the financial support of Nippon Keidanren and Cambridge Overseas Trust. EPSRC support is acknowledged by NS. This work made use of the facilities of HECToR...

Discrete pdf estimation in the presence of noise

Yoon, Byung-Jun; Vaidyanathan, P. P.
Fonte: IEEE Publicador: IEEE
Tipo: Book Section; PeerReviewed Formato: application/pdf
Publicado em 03/09/2004 Português
Relevância na Pesquisa
26.408977%
The problem of estimating a pdf from measurements has been widely studied by many researchers. However, most of the work was focused on estimating a probability density function of continuous random variables, especially in the absence of noise. In this paper, we consider a model for representing discrete probability density functions based on multirate dsp models. Using this model, we propose an efficient and stable scheme for pdf estimation when the measurements are corrupted by independent additive noise. This approach makes use of well-known results from multirate dsp theory, especially that of biorthogonal partners. Simulation results are given, which clearly show the advantage of the proposed method.