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    Wyświetlanie 1-9 z 9
    Tytuł:
    Design, construction and performance of a pressure chamber for water retention curve determination through traditional and nuclear methods
    Autorzy:
    Pires, L.
    Bacchi, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/146181.pdf
    Data publikacji:
    2006
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    soil water potential
    gamma-ray attenuation
    soil water content
    soil physics
    radioisotope application
    Opis:
    We present in this work a detailed design of a small low-pressure chamber outfitted with a ceramic porous plate for evaluating the soil water retention curve (SWRC) in the water potential range from 0 to -100 kPa. The chamber is made of acrylic and permits the use of one unique soil sample each time. The use of this chamber allows quick measurements of soil moisture using nuclear (based on gamma-ray attenuation) and conventional methods and SWRC determinations made with the designed chamber are in agreement with those obtained using a commercial low-pressure chamber. The chamber was designed especially for testing the use of the nuclear method as an auxiliary tool for SWRC determinations but it can be easily adapted for routine investigations and a practical alternative for the conventional SWRC method.
    Źródło:
    Nukleonika; 2006, 51, 4; 225-230
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Time of soil water thermodynamic equilibrium during retention curve establishment using gamma-ray beam attenuation
    Autorzy:
    Pires, L.
    Bacchi, O.
    Reichardt, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/148674.pdf
    Data publikacji:
    2005
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    gamma-ray attenuation
    time of equilibrium
    pressure chamber
    soil water retention curve
    Opis:
    The soil water retention curve (SWRC) represents a fundamental part of the characterization of the soil hydraulic properties. The establishment of SWRC is usually time-consuming and presents several problems such as the difficulty of a correct judgment of the time of equilibrium. This work presents a new methodology that involves gammaray beam attenuation technique associated with the traditional pressure chambers, having as objective the more precise judgment of the time to attain equilibrium. The gamma-ray source used has an activity of 3.7 GBq consisting of 241Am, with peak energy of 59.54 keV. For the determination of retention curves using the gamma-ray attenuation technique, an acrylic pressure chamber was projected and constructed to be positioned between the source and detector with the gamma-ray beam crossing the center of the chamber and the soil sample during water extraction. The proposed technique allowed, through a specifically elaborated software for data acquisition, to evaluate with precision the exact instant of the equilibrium and, consequently, to obtain the right moment to change the chamber pressure to a new desired level, leading to a reduction of the time required for the whole retention curve determination. The results obtained show that the gamma-ray attenuation technique can be very useful as an auxiliary tool to evaluate SWRC, utilizing the Richards chamber.
    Źródło:
    Nukleonika; 2005, 50, 4; 173-177
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    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:
    Gamma-ray beam attenuation to assess the influence of soil texture on structure deformation
    Autorzy:
    Pires, L.
    Bacchi, O.
    Dias, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/147480.pdf
    Data publikacji:
    2006
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    gamma-ray attenuation
    soil physical properties
    soil structure deformation
    soil sampling
    soil porosity
    Opis:
    Gamma-ray beam attenuation is a non-invasive technique that permits analysis of soil porosity without disturbing the region of interest of the core sample. The technique has as additional advantage to allow measurements point by point on a millimetric scale in contrast to other methodologies that are invasive and analyze the soil properties in the bulk sample volume. Soil porosity can be used as an important parameter to quantify soil structural damages, which affect soil aeration, water movement and retention. In this study, porosities of three soils different in texture were measured at various positions in order to analyze the impact of the sampling procedure on the structure of each particular soil texture. The gamma-ray attenuation system consisted of an 241Am radioactive source having an activity of 3.7 GBq, collimated with cylindrical lead collimators of 2 mm diameter. The results obtained show the presence of dense regions near the edges of samples and that different soil textures can suffer distinct deformations at sampling.
    Źródło:
    Nukleonika; 2006, 51, 2; 125-129
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Gamma-ray computed tomography as a tool to evaluate porosity changes along depth for surface crusted soils
    Autorzy:
    Pires, L. F.
    Bacchi, O. O. S.
    Reichardt, K.
    Dias, N. M. P.
    Powiązania:
    https://bibliotekanauki.pl/articles/146838.pdf
    Data publikacji:
    2007
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    gamma-ray attenuation
    soil density
    soil structure
    soil surface sealing
    241 Am
    applied nuclear physics
    gamma tomography
    Opis:
    Assessment of changes in porosity (ö) along depth for soils with surface crusting is difficult because conventional soil physical investigation tools are destructive and usually require a long period of time for preparation and analysis of the samples. Computed tomography (CT) has frequently been used as a method to evaluate soil structure in a nondestructive, sensitive, and rapid manner. CT data can be used for measuring at a millimetric scale changes in ö along depth for soils with surface crusting. The main objective of this work was to investigate the sensibility of the gamma-ray CT to assess soil structural changes along depth in samples presenting structural crust. CT images were taken with a first generation scanner of 1.14 mm resolution along eight different soil layers within the 0 28 mm depth. Porosity increased along depth up to the 14 17.5 mm layer. Through the analysis of the ö distribution of each layer it was possible to show that the sealed surface layer presented ö values of approximately 30%, while the other layers were greater than 30% up to 60% (macropore regions). The sealing crust thickness was estimated to be in the range of 2.3 3.5 mm.
    Źródło:
    Nukleonika; 2007, 52, 3; 125-131
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Calculation of grounding grids parameter at arbitrary geometry
    Autorzy:
    Silva, C. L. B.
    Pires, T. G.
    Calixto, W. P.
    Oliveira, D. N.
    Souza, L. A. P.
    Filho, A. M. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/136173.pdf
    Data publikacji:
    2017
    Wydawca:
    EEEIC International Barbara Leonowicz Szabłowska
    Tematy:
    grounding grids parameters
    Heppe
    soil stratified in two layers
    Opis:
    This paper deals with the computation of ground resistance, surface voltage, touch voltage and step voltage, to mesh with horizontal wires arranged in different angles. The computer program implemented used in the mathematical modeling is based on the method proposed by Heppe, which allows obtaining the grounding parameters for homogeneous soil and soil stratified in two layers. The results obtained with the proposed method will be compared with other methods in literature. Also will be presented the results of a grounding grid using wires at various angles.
    Źródło:
    Transactions on Environment and Electrical Engineering; 2017, 2, 2; 11-17
    2450-5730
    Pojawia się w:
    Transactions on Environment and Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Voltage-tunable dual-colour quantum Bragg mirror detector (QBMD)
    Autorzy:
    Penello, Germano M.
    Pereira, Pedro H.
    Sousa, Vitor B.
    Kawabata, Rudy M. S.
    Pires, Mauricio P.
    Souza, Patricia L.
    Powiązania:
    https://bibliotekanauki.pl/articles/2204218.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    bound states in the continuum
    intersubband transition
    infrared detector
    quantum Bragg mirror and dual-colour detection
    Opis:
    The electronic quasi-bound state in the continuum concept is explored in an InGaAs/InAlAs heterostructure to create a voltage-tunable dual-colour quantum Bragg mirror detector. This heterostructure is based on one main quantum well embedded between two different superlattices. By bandgap engineering, each superlattice gives rise to quasi-bound states in the continuum with a preferential direction for electron extraction. Due to these states, the photovoltaic photocurrent presents a dual-colour response, one in a positive direction at 340 meV (3.6 µm), and one in a negative direction at 430 meV (2.9 µm). The simultaneous dual-colour detection can be switched to a single-colour detection (340 meV or 430 meV) by applying a bias voltage. At 77 K, the specific detectivity for simultaneous dual-colour is 2.5·10⁸ Jones, while the single-colour detectivities are 2.6·10⁹ Jones at +2.0 V and 7.7·10⁸ Jones at -1.6 V for 340 meV and 430 meV, respectively.
    Źródło:
    Opto-Electronics Review; 2023, 31, Special Issue; art. no. e144559
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geoelectric method applied in correlation between physical characteristics and electrical properties of the soil
    Autorzy:
    Filho, A. M. S.
    Silva, C. L. B.
    Oliveira, M. A. A.
    Pires, T. G.
    Alves, A. J.
    Calixto, W. P.
    Narciso, M. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/136150.pdf
    Data publikacji:
    2017
    Wydawca:
    EEEIC International Barbara Leonowicz Szabłowska
    Tematy:
    geoelectrical prospecting
    apparent
    electrical resistivity
    soil compaction
    moisture content
    Opis:
    This paper presents the study of the relationship between electrical properties and physical characteristics of the soil. Measures of apparent electrical resistivity of the soil were made for different types of soil, varying moisture content gradually while maintaining a constant compaction, and then varying the compaction and relating it to a constant humidity. Development of a correlation surface is proposed in order to identify granulometry of the soil from moisture and compaction measurements. For the study of spatial variability, two areas were chosen to allow the change of moisture content and compaction in order to verify the measurement capacity of apparent electrical resistivity of the soil as methodology to identify change in soil dynamics. Results obtained show correlations among apparent electrical resistivity of the soil, moisture, soil compaction and clay content.
    Źródło:
    Transactions on Environment and Electrical Engineering; 2017, 2, 2; 37-44
    2450-5730
    Pojawia się w:
    Transactions on Environment and Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impact of residual doping on surface current of InGaAs/InP photodiode passivated with regrown InP
    Autorzy:
    Braga, Osvaldo M.
    Delfino, Cristian A.
    Kawabata, Rudy M. S.
    Pinto, Luciana D.
    Vieira, Gustavo S.
    Pires, Mauricio P.
    Souza, Patricia L.
    Marega, Euclydes
    Carlin, John A.
    Krishna, Sanjay
    Powiązania:
    https://bibliotekanauki.pl/articles/2204208.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    simulation
    residual doping
    recombination velocity
    surface passivation
    regrowth
    Opis:
    The viability of epitaxial regrowth of non-intentionally doped InP to passivate lateral mesa surfaces of InGaAs photodiodes lattice-matched to InP is investigated, evaluating whether the residual doping of the regrown layer can be responsible for un unexpected increase of the surface current. The effect of residual doping is evaluated via numerical calculations of dark current, considering the range of doping concentrations expected for non-intentionally doped InP. The calculations show that the increase in dark current due to the residual doping of the regrown InP layer is not enough to justify the observed increase in surface current. On the other hand, the technique is still valid as a passivation method if the photodetector pixel is isolated by etching only the top contact layer.
    Źródło:
    Opto-Electronics Review; 2023, 31, Special Issue; art. no. e144562
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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