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Wyświetlanie 1-15 z 15
Tytuł:
Presenting a technique for registering images and range data using a topological representation of a path within an environment
Autorzy:
Ferreira, F.
Davim, L.
Rocha, R.
Dias, J.
Santos, V.
Powiązania:
https://bibliotekanauki.pl/articles/385035.pdf
Data publikacji:
2007
Wydawca:
Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów
Tematy:
sensor feature integration
binary data
Bernoulli mixture model
dimensionality reduction
robot localisation
change detection
Opis:
This article presents a novel method to the utilize topological representation of a path, thatpath that is created from sequences of images from digital cameras and sensor data from range sensors. A topological representation of the environment is created by leading the robot around the environment during a familiarisation phaseLeading the robot around the environment during a familiarisation phase creates a topological representation of the environment. While moving down the same path, the robot is able to localise itself within the topological representation that is has been previously created. The principal contribution to the state of the art is that, by using a topological representation of the environment, individual 3D data sets acquired from a set of range sensors need not be registered in a single, [Global] Coordinate Reference System. Instead, 3D point clouds for small sections of the environment are indexed to a sequence of multi-sensor views, of images and range data. Such a registration procedure can be useful in the construction of 3D representations of large environments and in the detection of changes that might occur within these environments.
Źródło:
Journal of Automation Mobile Robotics and Intelligent Systems; 2007, 1, 3; 47-56
1897-8649
2080-2145
Pojawia się w:
Journal of Automation Mobile Robotics and Intelligent Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gelatin as a versatile hydrogel building block: one polymer, many applications
Autorzy:
Musial, O.
Vlierberghe, S. van
Billiet, T.
Ferreira, F.
Venderleyden, E.
Cornelissen, R.
Declercq, H.
Schrooten, J.
Unger, R.
Kirkpatrick, J.
Dubruel, P.
Powiązania:
https://bibliotekanauki.pl/articles/285615.pdf
Data publikacji:
2012
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
Tematy:
hydrogels
gelatin
polymers
Źródło:
Engineering of Biomaterials; 2012, 15, no. 116-117 spec. iss.; 125-126
1429-7248
Pojawia się w:
Engineering of Biomaterials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Soil porosity distribution representative elementary area analyzed through gamma-ray computed tomography
Autorzy:
Ferreira, T.R.
Pires, L.F.
Powiązania:
https://bibliotekanauki.pl/articles/25444.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Opis:
This study aims to use γ-ray computed tomography images to define the representative elementary area of the soil porosity distribution. Different textured soils from Southeast Brazil and different schemes of areas were analyzed. The image acquisition was performed in 2006 using a first generation γ-ray computed tomography system equipped with 241Am radioactive source. Consecutive increasing areas located at the center (scheme 1), the inferior (scheme 2) and superior (scheme 3) borders of the sample computed tomography image, with size areas ranging from 1.2 to 678.8 mm², were selected. The full width at a half maximum parameter was used to describe the samples soil porosity distribution and mathematical analysis concepts were adopted to define the representative elementary area. The representative elementary areas found for the sandy soil (Geric Ferralsol) and clayey soils (Rhodic Ferralsol and Eutric Nitosol) were respectively: 514.3, 514.3 and 555.4 mm² (scheme 1); 279.5, 393.3 and 457.4 mm² (scheme 2); and 457.4, 457.4 and 457.4 mm² (scheme 3). The results confirmed that the representative elementary area were influenced by the soil texture and management. Different schemes were noticed to provide different representative elementary areas for the same soil, which suggests that this procedure was efficient to detect the heterogeneity inside the soil samples.
Źródło:
International Agrophysics; 2016, 30, 4
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
Tytuł:
Linear matrix inequalities control driven for non-ideal power source energy harvesting
Autorzy:
Ferreira, D. C.
Chavarette, F. R.
Peruzzi, N. J.
Powiązania:
https://bibliotekanauki.pl/articles/281518.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
energy harvesting
efficiency
control
non-ideal excitation
Opis:
The dynamic model of a linear energy harvester excited by a non-ideal power source is coupled to a controller to maximum vibration adjustment. Numerical analysis is taken to evaluate the energy harvested keeping the vibration optimized for the maximum interaction to the energy source using linear matrix inequalities for control driven. The dimensionless power output, actuation power and net output power is determined. As a result, it is possible to verify that the total energy harvested via exogenous vibration using the proposed controller is increased up to 65 times when in comparison to the open loop system.
Źródło:
Journal of Theoretical and Applied Mechanics; 2015, 53, 3; 605-616
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Navigation Simulator: professional and academic learning tool for the students of the Portuguese Naval Academy
Autorzy:
Lopes-Ferreira, A.
Bué, I.M.
Lopes, C.F.
Powiązania:
https://bibliotekanauki.pl/articles/115983.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
Maritime Education and Training (MET)
Navigation Simulator
academic learning
Portuguese Naval Academy
MET System in Portugal
NAVSIM
training model
competences
Opis:
The Portuguese Naval Academy is a military school with an university status and is equipped with one modern navigation and maneuvering simulator. The Navigation Simulator (NAVSIM) plays an essential role in the academic training for the Naval Academy and for its cadets, that are using this capacity since their first academic year as a learning tool. Identifying the non-technical skills that could be trained and focusing on the specific training of the technical skills is paramount, in order to maximize the training sessions for each cadet’s year. The assessment of statistical data referring to the last 6 years is important to identify where there are gaps in the exercises, as well as how the midshipman are prepared to perform functions of watch keeping on the ships fleet.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2017, 11, 1; 141-148
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electric motors maintenance planning from its operating variables
Planowanie utrzymania ruchu silników elektrycznych i ich zmiennych operacyjnych
Autorzy:
Rodrigues, F.
Fonseca, I.
Farinha, J. T.
Ferreira, L.
Galar, D.
Powiązania:
https://bibliotekanauki.pl/articles/409876.pdf
Data publikacji:
2017
Wydawca:
STE GROUP
Tematy:
maintenance
planned maintenance
electric machines
HMI/SCADA
utrzymanie ruchu
planowane utrzymanie ruchu
maszyny/urządzenia elektryczne
Opis:
The maintenance planning corresponds to an approach that seeks to maximize the availability of equipment and, consequently, increase the levels of competitiveness of companies by increasing production times. This paper presents a maintenance planning based on operating variables (number of hours worked, duty cycles, number of revolutions) to maximizing the availability of operation of electrical motors. The reading of the operating variables and its sampling is done based on predetermined sampling cycles and subsequently is made the data analysis through time series algorithms aiming to launch work orders before reaching the variables limit values. This approach is supported by tools and technologies such as logical applications that enable a graphical user interface for access to relevant information about their Physical Asset HMI (Human Machine Interface), including the control and supervision by acquisition through SCADA (Supervisory Control And data acquisition) data, also including the communication protocols among different logical applications.
Planowanie utrzymania ruchu odpowiada podejściu, które ma na celu maksymalizację dostępności wyposażenia, a w konsekwencji zwiększenie poziomu konkurencyjności przedsiębiorstw przez zwiększenie czasów produkcji. W artykule przedstawiono planowanie utrzymania ruchu w oparciu o zmienne operacyjne (liczba przepracowanych godzin, cykle robocze, liczba obrotów) w celu maksymalizacji dostępności pracy silników elektrycznych. Odczytywanie zmiennych operacyjnych i pobieranie próbek odbywa się na podstawie ustalonych z góry cykli próbkowania, następnie dokonuje się analizy danych za pomocą algorytmów szeregowania czasowego mających na celu uruchomienie zleceń roboczych przed osiągnięciem zmiennych wartości dopuszczalnych. Podejście to jest wspierane przez narzędzia i technologie, takie jak aplikacje logiczne, które umożliwiają wykorzystanie graficznego interfejsu użytkownika w celu uzyskania dostępu do istotnych informacji o ich zasobach fizycznych HMI (Human Machine Interface), w tym kontroli i nadzoru przez pozyskanie z wykorzystaniem SCADA (Supervisory Control And Data Acquisition) danych, w tym również protokołów komunikacyjnych pomiędzy różnymi aplikacjami logicznymi.
Źródło:
Management Systems in Production Engineering; 2017, 3 (25); 205-216
2299-0461
Pojawia się w:
Management Systems in Production Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water-based poly(urethane-urea) dispersions —meeting the European Union legislation
Dyspersje wodne poli(uretanowo-mocznikowe) w świetle wymagań prawodawstwa Unii Europejskiej
Autorzy:
Fernandes, I. P.
Costa, M. R.
Ferreira, M. J.
Barreiro, M. F.
Powiązania:
https://bibliotekanauki.pl/articles/947121.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
Tematy:
poly(urethane-urea)
water-based dispersion
European Union legislation
N-methyl-pyrrolidone free products
poli(uretano-mocznik)
dyspersja wodna
prawodawstwo Unii Europejskiej
produkty wolne od N-metylo-pirolidonu
Opis:
This article discusses the synthesis methods of water-based poly(urethane-urea) dispersions (PUD), which over the past few decades have developed a solid reputation for high performance applications, particularly in the field of adhesives and coatings. PUDs are mostly environmentally compatible products since they do not contain or contain only low amounts of volatile organic compounds (VOC). This is an important feature in view of the present environmental policies, where governments and internal agencies are placing emphasis on developing sustainable processes, improving work conditions and reducing emissions of toxic and polluting substances into the atmosphere. In this context, this paper will discuss the main approaches applied to PUD synthesis in order to meet severe environmental restrictions resulting from the EU legislation.
Omówiono metody syntezy dyspersji wodnych poli(uretanowo-mocznikowych) (PUD), które znajdują coraz szersze zastosowanie, szczególnie w produkcji klejów i powłok. PUD są na ogół produktami bezpiecznymi dla środowiska, ze względu na brak lub małą zawartość lotnych związków organicznych (VOC), co jest ważne w świetle obecnej polityki ochrony środowiska. Przedstawione w pracy metody syntezy PUD uwzględniają wymagania wynikające z prawodawstwa Unii Europejskiej w zakresie spełniania surowych ograniczeń środowiskowych.
Źródło:
Polimery; 2015, 60, 9; 536-540
0032-2725
Pojawia się w:
Polimery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical study of Hough technique in surgery of otosclerosis, using the finite element method
Autorzy:
Gentil, F.
Parente, M.
Martins, P.
Santos, C.
Almeida, E.
Ferreira, A.
Natali, R.
Powiązania:
https://bibliotekanauki.pl/articles/307201.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
metoda elementów skończonych
otoskleroza
wycięcie strzemiączka
strzemiączko
finite element method
otosclerosis
stapedectomy
stapedotomy
stapes
Opis:
Purpose: Otosclerosis is a metabolic bone disease of the otic capsule that can cause the stapes fixation, resulting in conductive hearing loss or, in a profound sensorineural deafness threshold. Surgery is one of the possible treatments for the otosclerosis. To repair small focus of otosclerosis in the anterior crus of the stapes, in 1960, Hough suggested the implementation of a technique in which part of the anterior crus is fractured and the stapes turned. As a result, the posterior crus of the stapes is the only connection with the inner ear. In this work, the outcome of Hough’s surgical technique was simulated. Methods: Based on computerized images, a finite element model of middle ear ossicles and tympanic membrane was created, as well as a model where the stapes has changed. The discretization of the tridimensional solid model was made using the ABAQUS software. The mechanical properties used were taken from the literature and adequate boundary conditions were applied. Results: The results obtained with the Hough technique simulation were compared with a representative model of the normal ear, taking into account the displacements obtained on the central part of the stapes footplate and the maximum principal stress in the stapes crus. Conclusions: The results obtained are closer to the normal ear model, therefore Hough technique stands out as a good option to correct small focus of otosclerosis.
Źródło:
Acta of Bioengineering and Biomechanics; 2015, 17, 4; 149-153
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
Tytuł:
A Step Forward Towards Exploring Nutritional and Biological Potential of Mushrooms: A Case Study of Calocybe gambosa (Fr.) Donk Wild Growing in Serbia
Autorzy:
Petrović, Joavana
Fernandes, Angela
Stojković, Dejan
Soković, Marina
Barros, Liliana
Ferreira, Isabel C.F.R.
Shekhar, Aditya
Glamoclija, Jasmina
Powiązania:
https://bibliotekanauki.pl/articles/2019468.pdf
Data publikacji:
2022-03-01
Wydawca:
Instytut Rozrodu Zwierząt i Badań Żywności Polskiej Akademii Nauk w Olsztynie
Tematy:
C. gambosa
nutritional value
biological activity
chemical characterization
food ingredient
Opis:
Edible mushrooms have been appreciated globally for their organoleptic, nutritional and chemical properties. In the present study, fruiting body of Calocybe gambosa, wild growing in Serbia, has been chemically characterized (content of macronutrients, soluble sugars, tocopherols, fatty and organic acids) and its bioactive (antimicrobial and antioxidant) properties were evaluated. The results obtained suggest that this mushroom is a source of carbohydrates and proteins (72 g/100 g dry weight (dw) and 16 g/100 g dw, respectively), with a low fat content (1.5 g/100 g dw). Sugar analysis revealed the presence of trehalose (3.82 g/100 g dw) and mannitol (0.22 g/100 g dw). Tocopherol composition revealed the presence of α-tocopherol (7.8 μg/100 g dw), while fatty acid analysis revealed the presence of 24 fatty acids with the prevalence of polyunsaturated fatty acids. Amongst organic acids, oxalic, quinic, malic, citric and fumaric acid were detected (2.8 g/100 g dw, 1.45 g/100 g dw, 11.3 g/100 g dw, 1.3 g/100 g dw, 0.08 g/100 g dw, respectively). Comprehensive antioxidant activity analysis (reducing power, DPPH radical scavenging activity, β-carotene/linoleate and TBARS assays) indicate that the mushroom is a perspective antioxidant source, whereas its antimicrobial potential turned out to be moderate. Nevertheless, at a sub-inhibitory level, the methanolic extract disrupted cell-to-cell communication using Pseudomonas aeruginosa PAO1 as a model system. Finally, enrichment of oatmeal cookies with C. gambosa flakes not only improved their nutritional value, but was praised among the participants in sensory evaluation test, indicating that along with results of chemical composition and biological activity, this mushroom has a potential to be regarded as functional food.
Źródło:
Polish Journal of Food and Nutrition Sciences; 2022, 72, 1; 17-26
1230-0322
2083-6007
Pojawia się w:
Polish Journal of Food and Nutrition Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Peanut allergy as a tigger for the deterioration of atopic dermatitis and precursor of staphylococcal and herpetic associated infections - case report
Autorzy:
de Carvalho Ferreira, D.
Abad, E.D.
Cavalcante, F.S.
dos Santos, F.M.
Saintive, S.
Goudoris, E.
do Prado, E.A.
Ribeiro, M.
Rosado, A.S.
van Elsas, J.D.
dos Santos, K.R.N.
Powiązania:
https://bibliotekanauki.pl/articles/51908.pdf
Data publikacji:
2015
Wydawca:
Instytut Medycyny Wsi
Źródło:
Annals of Agricultural and Environmental Medicine; 2015, 22, 3
1232-1966
Pojawia się w:
Annals of Agricultural and Environmental Medicine
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Seroprevalence of SARS-CoV-2 and assessment of epidemiologic determinants in Portuguese municipal workers
Autorzy:
Barros Ferreira, Nuno
Pereira, Helena
Pereira, Ana M.
Azevedo, Luís F.
Santos, Mariana
Maranhão, Priscila
Correia, Ricardo
Fonseca, João A.
Canedo, Paulo
da Costa Pereira, Altamiro
Sousa-Pinto, Bernardo
Powiązania:
https://bibliotekanauki.pl/articles/2084912.pdf
Data publikacji:
2022-06-08
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
SARS-CoV-2 infection
COVID-19 pandemic
COVID-19 virus
COVID-19 serodiagnosis
COVID-19 antibody testing
SARS-CoV-2 infection serological testing
Opis:
ObjectivesTo assess the seroprevalence of SARS-CoV-2 antibodies in municipal employees of Northern Portugal during the first pandemic wave (May–June 2020) and its association with potentially related risk factors for infection.Material and MethodsThe authors assessed municipal employees of 2 cities in Northern Portugal, in whom serological tests to SARS-CoV-2 and an epidemiological survey were applied. The authors assessed the proportion of individuals presenting IgM and/or IgG antibodies to SARS-CoV-2, and evaluated the association between having positive serological test results, epidemiologic variables and clinical presentations. Reported symptoms were evaluated on their sensitivity, specificity, and predictive values.ResultsThe authors assessed 1696 employees, of whom 22.0% were firefighters, 10.4% were police officers, 10.3% were maintenance workers, and 8.1% were administrative assistants. The seroprevalence of SARS-CoV-2 infection was 2.9% (95% CI: 2.1–3.7%). Administrative assistants comprised the professional group with highest seroprevalence of SARS-CoV-2 (OR = 1.9 in the comparison with other occupational groups, 95% CI: 0.8–4.3, p = 0.126). The seroprevalence of SARS-CoV-2 infection among those who were in direct contact with COVID-19 patients in their professional activity was 3.9%, compared to 2.7% among those who were not in direct contact with such patients (OR = 1.5, 95% CI: 0.8–2.8, p = 0.222). The highest risk of infection was associated with the presence of a confirmed SARS-CoV-2 infection in the household (OR = 17.4, 95% CI: 8.3–36.8, p < 0.001). Living with a healthcare professional was not associated with a higher risk of infection (OR = 1.0, 95% CI: 0.4–2.5, p = 0.934). Anosmia/dysgeusia was the symptom with the highest positive predictive value (52.2%, 95% CI: 31.8–72.6, p < 0.001) and specificity (99.3%, 95% CI: 98.9–99.7, p < 0.001), while cough was the most prevalent symptom among SARS-CoV-2 seropositive participants (36%).ConclusionsThe authors observed a SARS-CoV-2 seroprevalence of 2.9% among assessed municipal employees. Anosmia/dysgeusia was the COVID-19 symptom which displayed the highest positive predictive value and specificity.
Źródło:
International Journal of Occupational Medicine and Environmental Health; 2022, 35, 3; 297-307
1232-1087
1896-494X
Pojawia się w:
International Journal of Occupational Medicine and Environmental Health
Dostawca treści:
Biblioteka Nauki
Artykuł
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 550C 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
Artykuł
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
Artykuł
    Wyświetlanie 1-15 z 15

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