Autor: Ferreira, L. A. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Time-of-Flight Positron Emission Tomography with Resistive Plate Chamber Detectors: An Unlikely but Promising Approach
Autorzy:: Couceiro, M.
Crespo, P.
Blanco, A.
Ferreira, N.
Mendes, L.
Ferreira Marques, R.
Fonte, P.
Powiązania:: https://bibliotekanauki.pl/articles/1402607.pdf
Data publikacji:: 2015-05
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 87.57.uk
29.40.Cs
87.57.cf
87.57.cm
Opis:: The cost-effectiveness of resistive plate chamber detectors and their very good timing characteristics, open the possibility to build affordable time-of-flight positron emission tomography systems with a large axial field-of-view. Simulations suggest that, under reasonable assumptions, the absolute 3D true sensitivity, spatial resolution, and noise equivalent count rate of such systems for human whole-body screening, may exceed that of present crystal-based PET technology. However, due to the lack of energy resolution, although having energy sensitivity, the scatter fraction is expected to be considerably higher than that presented by crystal-based PET scanners. In the present paper, the simulation work done so far to access the expected performance of a resistive plate chamber time-of-flight-PET system with 2400 mm length axial field-of-view, a time resolution of 300 ps full width at half maximum for photons pairs, and depth-of-interaction information, will be revised.
Źródło:: Acta Physica Polonica A; 2015, 127, 5; 1453-1461
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: The Effect of the Cavity Damping on Vehicular Evaluation using the Finite Element Method
Autorzy:: Ferreira, T. S.
Magalhães, P. A.
Moura, F. L.
Powiązania:: https://bibliotekanauki.pl/articles/176986.pdf
Data publikacji:: 2016
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: finite element method
acoustic control
trimmed body
numerical experimental correlation
modal damping
Opis:: This work focuses on finding a numerical solution for vehicle acoustic studies and improving the usefulness of the numerical experimental parameters for the development stage of a new automotive project. Specifically, this research addresses the importance of modal cavity damping for vehicle exerts during numerical studies. It then seeks to suggest standardized parameter values of modal cavity damping in vehicular acoustic studies. The standardized value of modal cavity damping is of great importance for the study of vehicular acoustics in the automotive industry because it would allow the industry to begin studies of the acoustic performance of a new vehicle early in the conception phase with a reliable estimation that would be close to the final value measured in the design phase. It is common for the automotive industry to achieve good levels of numerical-experimental correlation in acoustic studies after the prototyping phase because this phase can be studied with feedback from the simulation and experimental modal parameters. Thus, this research suggests values for modal cavity damping, which are divided into two parts due to their behaviour: ξ(x) = −0.0126(x − 100) + 6.15 as a variable function to analyse up to 100 Hz and 6.15% of modal cavity damping constant for studies between 30 Hz and 100 Hz. The sequence of this study shows how we arrived at these values.
Źródło:: Archives of Acoustics; 2016, 41, 1; 87-97
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Synthesis, characterization and catalytic properties of SAPO-11 molecular sieve synthesized in hydrothermal media using di-isopropylamine as template
Autorzy:: Chellappa, T.
Costa, M. J. F.
Nascimento, W. A.
Ferreira De Lima, L.
Bassan, I. A.
Tavares, M.
Fernandes, V. J.
Menezes, A.
Guilherme Meira, L.
Telesforo Nóbrega De Medeiros, J.
Maribondo Do Nascimento, R.
Powiązania:: https://bibliotekanauki.pl/articles/200372.pdf
Data publikacji:: 2014
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: microporous materials
SAPO-11
characterization
catalytic activity
molecular sieves
Opis:: A microporous SAPO-11 Molecular sieve was successfully synthesized by the hydrothermal method, using a single agent, as an organic template: di-isopropylamine (DIPA). The obtained solid was calcined at 550^◦C for three hours, after which the flow of nitrogen was exchanged for that of synthetic air and submitted for another ten hours of calcination, so as to remove the single agent: di-isopropylamine, which after the removal of the template could be observed by the high crystallization of the sample. Furthermore, the molecular sieve was characterized by XRD, SEM, TG-DTG and N2 adsorption desorption (BET analysis). The obtained catalyst proved to have a high potential catalytic activity and selectivity, through the obtained characterization results, exhibiting good hydrothermal stability. The catalytic performance of SAPO-11 was tested by the deactivation/regenerability of the coked sample, furthered by cracking of n-hexane reaction and high olefins selectivity was obtained.
Źródło:: Bulletin of the Polish Academy of Sciences. Technical Sciences; 2014, 62, 3; 481-488
0239-7528
Pojawia się w:: Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Positronium Trapping in Porous Solids: Means and Limitations for Structural Studies
Autorzy:: Kajcsos, Zs.
Liszkay, L.
Duplâtre, G.
Varga, L.
Lohonyai, L.
Pászti, F.
Szilágyi, E.
Lázár, K.
Kótai, E.
Pál-Borbély, G.
Beyer, H. K.
Caullet, P.
Patarin, J.
Azenha, M. E.
Gordo, P. M.
Lopes Gil, C.
de Lima, A. P.
Ferreira Marques, M.
Powiązania:: https://bibliotekanauki.pl/articles/2042216.pdf
Data publikacji:: 2005-05
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 36.10.Dr
78.70.Bj
61.43.Gt
Opis:: Positron annihilation techniques are used for the structural investigation of solids but the interpretation of results in grainy and porous media is still unclear. A unique picture can be obtained assuming that the dominant process is Ps trapping in competing "extended free volume" sites. In samples with a large amount of free volumes near-saturation Ps trapping will rule the lifetime pattern, and very long lifetimes of over 100 ns might arise from o-Ps trapped in mesopores. It is shown that lifetime parameters must be corrected for the 3γ/2γ counting efficiency ratio. The results demonstrate the high sensitivity of Ps to mesopores in zeolites but also that Ps-trapping poses limitations on the applicability of lifetime to structural investigation in porous systems. The evolution of the lifetime spectra upon changes in the sample and measuring conditions should be considered in a complex way, observing not only changes in some selected components but in the whole lifetime pattern simultaneously.
Źródło:: Acta Physica Polonica A; 2005, 107, 5; 729-737
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Parameter estimation for Weibull distribution with right censored data using EM algorithm
Zastosowanie algorytmu maksymalizacji wartości oczekiwanej do estymacji parametrów rozkładu Weibulla w przypadku danych obciętych prawostronnie
Autorzy:: Ferreira, L. A.
Silva, J. L.
Powiązania:: https://bibliotekanauki.pl/articles/301264.pdf
Data publikacji:: 2017
Wydawca:: Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:: algorytm EM
estymacja parametrów
estymator największej wiarygodności
niezawodność
EM algorithm
parameter estimation
maximum likelihood estimate
reliability
Opis:: Metoda największej wiarygodności (MLE) służy do estymacji parametrów modelu statystycznego dla zadanych danych. Metoda ta pozwala na estymację nieznanych parametrów modelu statystycznego. Parametry te otrzymuje się poprzez maksymalizację funkcji wiarygodności rozważanego modelu. Często w praktyce metoda ta może jednak nastręczać trudności związane z wielomodalnością funkcji wiarygodności oraz niemożnością uzyskania jawnych analitycznych rozwiązań równań wiarygodności. Równania takie można jedynie rozwiązywać za pomocą metod numerycznych. Trudności te dobrze ilustruje estymacja parametrów rozkładu Weibulla z wykorzystaniem metody największej wiarygodności wykonywana w oparciu o prawostronnie cenzurowane dane z eksploatacji. Rozwiązanie przedstawione w niniejszej pracy opiera się na zastosowaniu algorytmu maksymalizacji wartości oczekiwanej (EM). Możliwości aplikacyjne proponowanej metodyki badano na przykładzie danych eksploatacyjnych uzyskanych z przedsiębiorstwa petrochemicznego, dotyczących awarii pięciu pomp odśrodkowych.
The maximum-likelihood estimation (MLE) is a method of estimating the parameters of a statistical model for given data. This method allows us to estimate the unknown parameters of a statistical model. These parameters are obtained by maximizing the likelihood function of the model in question. In many practical situations the likelihood function is associated with complex models and the likelihood equation has no explicit analytical solution, it is only possible to have its resolution through numerical methods. The estimation of the parameters of the Weibull distribution by maximum-likelihood method based on information from a historical record with right censored data shows this difficulty. The solution presented in this article entails using the Expectation-Maximization (EM) algorithm. Actual data from the historical record of 5 centrifugal pumps failures of a petrochemical company were analyzed for application of the methodology.
Źródło:: Eksploatacja i Niezawodność; 2017, 19, 2; 310-315
1507-2711
Pojawia się w:: Eksploatacja i Niezawodność
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Observed and modelled solar radiation components in sugarcane crop grown under tropical conditions
Autorzy:: A. dos Santos, Marcos
L. de Souza, José
B. Lyra, Gustavo
Teodoro, Iêdo
A. Ferreira Junior, Ricardo
C. dos Santos Almeida, Alexsandro
B. Lyra, Guilherme
C. de Souza, Renan
A. Maringolo Lemes, Marco
Powiązania:: https://bibliotekanauki.pl/articles/972744.pdf
Data publikacji:: 2017
Wydawca:: Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:: sugarcane
albedo
net radiation
Opis:: The net radiation over vegetated surfaces is one of the major input variables in many models of soil evaporation, evapotranspiration as well as leaf wetness duration. In the literature there are relatively few studies on net radiation over sugarcane crop in tropical climates. The main objective of the present study was to assess the solar radiation components measured and modelled for two crop stages of a sugarcane crop in the region of Rio Largo, Alagoas, North-eastern Brazil. The measurements of the radiation components were made with a net radiometer during the dry and rainy seasons and two models were used to estimate net radiation: the Ortega-Farias model and the Monteith and Unsworth model. The highest values of net radiation were observed at the crop development stage, due mainly to the high indices of incoming solar radiation. The daily average albedos of sugarcane at the crop development and mid-season stages were 0.16 and 0.20, respectively. Both models showed a better fit for the crop development stage than for the mid-season stage. When they were inter-compared, Monteith and Unsworth model was more efficient than Ortega-Farias model, despite the dispersion of their simulated radiation components which was similar.
Źródło:: International Agrophysics; 2017, 31, 2
0236-8722
Pojawia się w:: International Agrophysics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Lipid peroxidation and photosynthetic apparatus oxidative damage in two varieties of grapevine growing in Mediterranean climate
Autorzy:: Dinis, L.
Malheiro, A.
Santos, D.
Ferreira, H.
Bacelar, E.
Goncalves, B.
Moutinho-Pereira, J.
Correia, C.
Powiązania:: https://bibliotekanauki.pl/articles/80493.pdf
Data publikacji:: 2013
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: conference
lipid peroxidation
photosynthetic apparatus
oxidative damage
grapevine
Mediterranean climate
high light stress
high temperature
Portugal
Źródło:: BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology; 2013, 94, 2
0860-7796
Pojawia się w:: BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Hypertonic saline solution (NaCl 7.2%) enhances renal excretion of acids in cattle with acute ruminal lactic acidosis
Autorzy:: Rodrigues, F.A.M.L.
Minervino, A.H.H.
Barrêto Júnior, R.A.
Reis, L.F.
Ferreira, R.N.F.
Mori, C.S.
Oliveira, F.L.C.
Sousa, R.S.
Powiązania:: https://bibliotekanauki.pl/articles/2087583.pdf
Data publikacji:: 2019
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: steers
ruminal lactic acidosis
hypertonic saline solution
Źródło:: Polish Journal of Veterinary Sciences; 2019, 1; 37-42
1505-1773
Pojawia się w:: Polish Journal of Veterinary Sciences
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: 4-amine-2-mercaptopyrimidine modified silica gel applied in Cd(II) and Pb(II) extraction from an aqueous medium
Autorzy:: Pereira, A.S.
Ferreira, G.
Caetano, L.
Castro, R.S.D.
dos Santos, A.
Padilha, P.M.
Castro, G.R.
Powiązania:: https://bibliotekanauki.pl/articles/778413.pdf
Data publikacji:: 2010
Wydawca:: Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:: 4-amino-2-merkaptopirymidyna
krzemionka
ekstrakcja metali
środowisko wodne
4-amine-2-mercaptopyrimidine
silica
metal extraction
aqueous medium
Opis:: This paper discusses silica surface modification by a process involving a two-step reaction: anchoring of a silylating agent, followed by an attachment of a 4-amino-2-mercaptopyrimidine molecule. The modified material (Si-BP) was successfully characterized by the FTIR spectra, which revealed amine absorption bands, and through 13C and 29Si NMR spectra, which confirm the proposed structure of the modified silica (Si-BP). Si-BP was used to extract cadmium and lead from an aqueous medium at 298 K. The Si-BP kinetics towards metal ions was very fast, i.e., about 10 minutes, although extraction was significantly impaired at pH 3. The series of adsorption isotherms were adjusted to a modified Langmuir equation and the maximum extraction capacity was 0.193 and 0.387 mmol g-1 for Cd(II) and Pb(II), respectively. An analysis of the Ř values lead to the inference that the resulting metal ligand complex was type 1:1.
Źródło:: Polish Journal of Chemical Technology; 2010, 12, 1; 7-11
1509-8117
1899-4741
Pojawia się w:: Polish Journal of Chemical Technology
Dostawca treści:: Biblioteka Nauki

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