1,580 research outputs found
Estrutura de sistemas silvipastoris na região nordeste paraense.
Os sistemas silvipastoris (SSPs) são sistemas agroflorestais que associam, na mesma área de cultivo, espécies arbóreas, pastagens e animais. Utilizou-se um questionário para levantamento desses sistemas na região nordeste paraense. Uma análise desses SSPs indica as seguintes características: a) a área média ocupada com os sistemas silvipastoris nas fazendas apresentadas está em torno de 45 ha, ocupando cerca de 20 % da área total, em tipos climáticos Af, Am e Aw; b) em geral, os sistemas silvipastoris têm o componente arbóreo plantado, sendo constituído pelas espécies: Paricá (Schizolobium amazonicum Huber ex Ducke), Teca (Tectona grandis L. f.), Mogno (Swietenia macrophylla King), Mogno-africano (Khaya ivorensis A. Chev.) e Samaúma (Ceiba pentandra (L.) Gaertn.); c) a densidade estimada das árvores é considerada alta, em torno de 480 árvores/ha; d) em termos médios, o componente arbóreo apresenta idade de 7 anos, altura de 9 metros, estando, portanto, em estágios iniciais de desenvolvimento; e) o componente pastagem está, principalmente, representado pelas espécies: Quicuio-da-amazônia (Brachiaria humidicola Schweick.) e Braquiarão (Brachia-ria brizantha Stapf), com pastejo de bovinos ou ovinos. As principais limitações tecnológicas dos SSPs observadas em áreas de produtores e em experimentos realizados são: a) baixa persistência da pastagem no sub-bosque, decorrente da não adaptação às condições de baixa luminosidade, superpastejo e concorrência com invasoras; b) danos às árvores, provocados pelos animais em virtude do pastejo precoce do sistema ou uso de tipo de animal inadequado; c) diminuição da taxa de crescimento das árvores, em decorrência de interferências por competição do estrato herbáceo ou interferências alelopáticas promovidas pelo componente pastagem ou plantas invasoras.bitstream/item/29492/1/BPD64.pdfVersão eletrônica. 1ª impressão: 2009
Sistemas silvipastoris do Nordeste paraense.
Publicado também como folder (FD 00711).bitstream/item/28248/1/ComTec120.pdfDisponível também on-line
New infrared star clusters in the Northern and Equatorial Milky Way with 2MASS
We carried out a survey of infrared star clusters and stellar groups on the
2MASS J, H and K_s all-sky release Atlas in the Northern and Equatorial Milky
Way (350 < l < 360, 0 < l < 230). The search in this zone complements that in
the Southern Milky Way (Dutra et al. 2003a). The method concentrates efforts on
the directions of known optical and radio nebulae. The present study provides
167 new infrared clusters, stellar groups and candidates. Combining the two
studies for the whole Milky Way, 346 infrared clusters, stellar groups and
candidates were discovered, whereas 315 objects were previously known. They
constitute an important new sample for future detailed studies.Comment: Accepted to Astronomy and Astrophysic
Levantamento de sistemas silvipastoris no estado do Pará, Brasil.
Editores: Luis Lamela López, Jesús Suárez Hernández, Nayda Armengol López, Alicia Ojeda González
Position-dependent-mass; Cylindrical coordinates, separability, exact solvability, and PT-symmetry
The kinetic energy operator with position-dependent-mass in cylindrical
coordinates is obtained. The separability of the corresponding Schr\"odinger
equation is discussed within radial cylindrical mass settings. Azimuthal
symmetry is assumed and spectral signatures of various z-dependent interaction
potentials (Hermitian and non-Hermitian PT-symmetric) are reported.Comment: 16 page
Rendimento de carne de pirarucu, Arapaima gigas (Cuvier).
bitstream/item/42268/1/Boletim-Pesquisa-150-CPATU.pd
INFLUENCE OF THERMOPHYSICAL PROPERTIES ON TRANSFER OF HEAT IN MULTI-LAYER DUCTS AND TEMPERATURE CONTROL USING ELECTRIC HEATING
Ensuring oil production flow in offshore systems is a critical aspect of oil exploration operations. Any interruption in the production process, whether partial or complete, can result in significant financial losses and cause solid deposition in the production line. Such deposition is due to the crystallization of paraffin and hydrates, a common problem caused by low temperatures in deep waters. Among various mitigation strategies, the Pipe-in-Pipe (PIP) system with active heating is a technological solution to address this issue. This work aimed to perform a numerical simulation of the PIP system using the Finite Volume Method with an implicit formulation, considering the effect of temperature on fluid properties and the system's dynamic response. A control loop using a PI velocity algorithm was developed to maintain the temperature above the critical point. Such simulation studies were performed using the Python programming language in the Anaconda suite. The results showed that the fluid properties greatly influence the dynamic response. The PI control maintained the temperature in the desired condition, demonstrating its operational effectiveness in preventing solid deposition and delivering stable and low-oscillatory behavior. This research emphasizes the significance of taking temperature's impact on fluid properties into account when simulating offshore oil production systems and demonstrates the effectiveness of implementing feedback control
Relativistic Mean-Field Hadronic Models under Nuclear Matter Constraints
Relativistic mean-field (RMF) models have been widely used in the study of
many hadronic frameworks because of several important aspects not always
present in nonrelativistic models, such as intrinsic Lorentz covariance,
automatic inclusion of spin, appropriate saturation mechanism for nuclear
matter, causality and, therefore, no problems related to superluminal speed of
sound. With the aim of identifying the models which best satisfy well known
properties of nuclear matter, we have analyzed parameterizations of seven
different types of RMF models under three different sets of constraints related
to symmetric nuclear matter, pure neutron matter, symmetry energy, and its
derivatives. One of these (SET1) is formed of the same constraints used in a
recent work [M. Dutra et al., Phys. Rev. C 85, 035201 (2012)] in which we
analyzed Skyrme parameterizations. The results pointed to models
consistent with all constraints. By using another set of constraints, namely,
SET2a, formed by the updated versions of the previous one, we found models
approved simultaneously. Finally, in the third set, named SET2b, in which the
values of the constraints are more restrictive, we found consistent models.
Another interesting feature of our analysis is that the results change
dramatically if we do not consider the constraint regarding the volume part of
the isospin incompressibility (). In this case, we have
approved models in SET2a and in SET2b.Comment: 63 pages, 3 figures and 9 tables. Version accepted for publication in
PR
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