Guilherme Cunha - Academia.edu (original) (raw)

Papers by Guilherme Cunha

Etic Encontro De Iniciacao Cientifica Issn 21 76 8498, Mar 25, 2015

Veterinaria Noticias, Sep 13, 2012

ABSTRACT The objective of this work was to determine fertilization rates and embryonal recovery a... more ABSTRACT The objective of this work was to determine fertilization rates and embryonal recovery and to evaluate aspects of the early embryonal development. Eleven adult female dogs were used, with no defined breed. After the beginning of the natural estrus, these were mated and subjected to ovariohisterectomy on the 5th, 7th or 9th day postcoitus. Ovaries, tubes and uterine horns were separated. From the ovaries, the number of corpora lutea was determined. Tubes and uterine horns were washed separately in order to collect ovules and embryos, which were identified through the use of a stereomicroscope at 15x magnification. The fertilization rate was 94% and embryonal recovery 68.5%. On the fifth day, postcoitus embryos of up to eight cells were found in uterine tubes. Morulae or blastocysts were observed in uterine horns from the 9th day after recovery. On the basis of these results, it was concluded that the loss of structures can be due to the failure of their uptake by uterine tubes or during the execution of the technique. A high fertilization rate can be achieved even with the use of a single covering. It was also concluded that the embryonal development in uterine tubes had a duration of up to five days postcoitus with a stage of up to eight cells, embryos being found in stages of morulae in uterine horns nine days postcoitus.

Veterinaria Noticias, Feb 27, 2008

Biotemas, 2011

... (Canis familiaris-Linnaeus, 1758) Guilherme Nascimento Cunha* José Octávio Jacomini Marcelo E... more ... (Canis familiaris-Linnaeus, 1758) Guilherme Nascimento Cunha* José Octávio Jacomini Marcelo Emílio Beletti ... Page 13. 167 Desenvolvimento embrionário inicial em fêmeas caninas Tsutsui, T.; Hori, T.; Okazaki, H.; Tanaka, A.; Shiono, M.; Yokosuka, M.; Kawakami, E. 2001. ...

Journal of Catalysis, 2004

2-(2-Pyridyl)phospholes have been evaluated as ligands for the nickel-catalyzed oligomerization o... more 2-(2-Pyridyl)phospholes have been evaluated as ligands for the nickel-catalyzed oligomerization of ethylene. Under mild homogeneous reaction conditions, high catalytic activities (> 15 cycles per second) were recorded. The selectivity depends on the ethylene pressure. At 41 bar, high C 4 fraction contents (until 97%) and high 1-butene selectivities (80% of the C 4 fraction) were reached. This behavior is interpreted as a consequence of the steric hindrance of the intermediate cationic 2-pyridylphosphole nickel hydrides.  2004 Elsevier Inc. All rights reserved.

Communications in Computational Physics, 2016

The present work constitutes a fraction of a more extensive study that is devoted to numerical me... more The present work constitutes a fraction of a more extensive study that is devoted to numerical methods in acoustics. More precisely, we address here the interpolation process, which is more and more frequently used in Computational Acoustics–whether it is for enabling multi-stage hybrid calculations, or for easing the proper handling of complex configurations via advanced techniques such as Chimera grids or Immersed Boundary Conditions. In that regard, we focus on high-order interpolation schemes, so as to analyze their intrinsic features and to assess their effective accuracy. Taking advantage of specific insights that had been previously achieved by the present authors regarding standard high-order interpolation schemes (of centered nature), we here focus on their so-calledspectral-like optimizedcounterparts (of both centered and noncentered nature). The latter spectral-like optimized schemes are analyzed thoroughly thanks to dedicated theoretical developments, which allow highlig...

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference), 2012

The present article aims at highlighting the strengths and weaknesses of the so-called spectral-l... more The present article aims at highlighting the strengths and weaknesses of the so-called spectral-like optimized (explicit central) finite-difference schemes, when the latter are used for numerically approximating spatial derivatives in aeroacoustics evolution problems. With that view, we first remind how differential operators can be approximated using explicit central finite-difference schemes. The possible spectral-like optimization of the latter is then discussed, the advantages and drawbacks of such an optimization being theoretically studied, before they are numerically quantified. For doing so, two popular spectral-like optimized schemes are assessed via a direct comparison against their standard counterparts, such a comparative exercise being conducted for several academic test cases. At the end, general conclusions are drawn, which allows us discussing the way spectral-like optimized schemes shall be preferred (or not) to standard ones, when it comes to simulate real-life aeroacoustics problems.

International Journal for Numerical Methods in Fluids, 2015

ABSTRACT The present paper addresses the optimization of finite-difference schemes when these are... more ABSTRACT The present paper addresses the optimization of finite-difference schemes when these are to be used for numerically approximating spatial derivatives in aeroacoustics evolution problems. With that view in mind, finite-difference operators are firstly detailed from a theoretical point of view. Secondly, the way such operators can be optimized in a spectral-like sense is recalled, before the main limitations of such an optimization are highlighted. This leads us to propose an alternative optimization approach of innovative character. Such a novel optimization technique consists of enhancing the scheme’s formal accuracy through a minimization of its leading-order truncation error. This so-called intrinsic optimization procedure is first detailed, before it is thoroughly analyzed, from both a theoretical and a practical point of view. The second part of the paper focuses on two particular intrinsically optimized schemes, which are carefully assessed via a direct comparison against their standard and/or spectral-like optimized counterparts, such a comparative exercise being conducted utilizing several academic test cases of increasing complexity. There, it is shown how intrinsically optimized schemes indeed constitute an advantageous alternative to either the standard or the spectral-like optimized ones, being allotted with both (i) the better scalability of the former scheme with respect to grid convergence effects when the grid density increases and (ii) the higher accuracy of the latter scheme when the discretization level becomes marginal. Thanks to that, such intrinsically optimized schemes offer very good trade-offs in terms of (i) accuracy; (ii) robustness; and (iii) numerical efficiency (CPU cost).

Computational fluid mechanics with finite volume method needs high-quality computational meshes t... more Computational fluid mechanics with finite volume method needs high-quality computational meshes that can be structured or not. When properly constructed, structured meshes provide several advantages over unstructured ones as, for instance, (i) higher metrics quality, (ii) a corresponding matrix of fixed bandwidth and (iii) a straightforward numerical implementation due to a simple and effective variable indexation. However, their lower adaptability to complex geometries can be considered as their main drawback. On the other hand, unstructured meshes are more flexible with respect to geometrical topology, at the expense of some loss regarding the advantages cited above. As a matter of fact, the non-collinearity between the center-to-center vector of adjacent cells and the normal vector of the face that connects these cells makes difficult the approximation of the gradient of a field at the face. A common procedure to overcome this problem uses a non-orthogonality correction. In this ...

19th AIAA/CEAS Aeroacoustics Conference, 2013

ABSTRACT The present work is relevant from the numerical prediction of aircraft noise via aeroaco... more ABSTRACT The present work is relevant from the numerical prediction of aircraft noise via aeroacoustics hybrid methods. It is part of a more extensive effort, which final objective is the development of a robust and accurate CFD-CAA weak coupling methodology. Within this framework, we focus here on the so-called surface coupling approach, a technique that allows conducting weakly coupled CFD-CAA calculations. Such approach (which had been previously developed and validated on simpler cases) is here applied to a ralistic problem of aircraft noise, given by the acoustic emission of a nose landing gear in approach flight (a configuration that was addressed in the Airbus LAGooN program). For doing so, several preliminary tasks are first addressed, which are carefully handled and thoroughly detailed. Two CFD-CAA coupled calculations are then conducted, both being based on i) a same CFD dataset coming from an unsteady aerodynamic calculation (zonal DES), and ii) two distinct CAA calculations of different characteristics ; first, a CFD-CAA calculation is conducted for the so-called 'baseline' configuration (i.e. isolated gear within a free-field flow), so as to validate the coupling procedure, as well as to generate a reference solution for subsequent assessment of the mean flow effects induced by the experimental set-up. The validation of the coupling procedure is conducted via a direct comparison of the CFD-CAA results with either experimental or numerical (CFD, CFD-FWH) outputs obtained in the near-, mid, and/or far-field. With the view of assessing the mean flow effects, an alternative CFD-CAA calculation is then performed, which incorporates the realistic sheared jet flow characterizing the anechoic facility. This allows assessing the (partial) convection and refraction effects induced by such jet mean flow, which helps underscoring better the relevance of the present CFD-CAA hybrid approach when it comes to handle real-life noise problems.

20th AIAA/CEAS Aeroacoustics Conference, 2014

ABSTRACT In regard to the mitigation of noise annoyance by aircraft, the present work addresses a... more ABSTRACT In regard to the mitigation of noise annoyance by aircraft, the present work addresses acoustic hybrid approaches, which allow simulating a given noise problem via successive weakly-coupled computations. Within that context, over the past four years, several R&D works were conducted at Onera so as to improve and optimize an already existing high fidelity acoustic hybrid approach, which noise propagation stage relies on a Computational Aeroacoustics (CAA) method. Consisting in dedicated theoretical studies, algorithmic developments and numerical simulations, these R&D works resulted in fundamental insights and methodological innovations. The latter were all validated against various test cases of increasing complexity, which were mostly derived from test cases proposed within the Benchmark for Airframe Noise Computations (BANC) initiative supported by NASA. This shows how international benchmark efforts such as the ones promoted through BANC initiative constitute a key means for improving numerical methods in acoustics, whether it is by offering to consolidate further already existing approaches, or by helping in making novel techniques emerge.

17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), 2011

ABSTRACT The present work constitutes a fraction of a more extensive study that is dedicated to t... more ABSTRACT The present work constitutes a fraction of a more extensive study that is dedicated to the improvement of hybrid methods for aeroacoustics. More precisely, we address here the interpolation step that is to be achieved between their CFD and CAA stages, when the latter are weakly coupled. First, thanks to theoretical investigations, we analyze the interpolation process and the mechanisms underlying its two main issues, which are the spurious modes generation and the signal degradation. The former is then more particularly studied, before an innovative interpolation technique is proposed for minimizing its eects. This innovative procedure is then assessed/validated against several test cases of increasing complexity. Finally, the way such procedure can help in improving and/or lightening hybrid methods processes is discussed.

The beef cattle chain in the State of Rio Grande do Sul has competitive difficulties. However, th... more The beef cattle chain in the State of Rio Grande do Sul has competitive difficulties. However, the state has territorial strategical reso urces that can help for the change in the unfavorable current scene. With the objective to ad d value to the produced meat in the region of the Campanha of the RS was created the In dication of Origin. This study aims to identify the motivations of the stakeholders to cre ate a quality convention. It had been made in-depth interviews with the integrant of the association. The results had shown that the economic motivation was the main factor for the creation of the convention of quality around the Indication of Origin of the Meat of Pamp as Gaucho.

Memórias do Instituto Oswaldo Cruz, 2009

Roraima is the northernmost state of Brazil, bordering both Venezuela and Guyana. Appropriate cli... more Roraima is the northernmost state of Brazil, bordering both Venezuela and Guyana. Appropriate climate and vector conditions for dengue transmission together with its proximity to countries where all four dengue serotypes circulate make this state, particularly the capital Boa Vista, strategically important for dengue surveillance in Brazil. Nonetheless, few studies have addressed the population dynamics of Aedes aegypti in Boa Vista. In this study, we report temporal and spatial variations in Ae. aegypti population density using ovitraps in two highly populated neighbourhoods; Centro and Tancredo Neves. In three out of six surveys, Ae. aegypti was present in more than 80% of the sites visited. High presence levels of this mosquito suggest ubiquitous human exposure to the vector, at least during part of the year. The highest infestation rates occurred during the peak of the rainy seasons, but a large presence was also observed during the early dry season (although with more variation among years). Spatial distribution of positive houses changed from a sparse and local pattern to a very dense pattern during the dry-wet season transition. These results suggest that the risk of dengue transmission and the potential for the new serotype invasions are high for most of the year.

Journal of Computational Physics, 2014

ABSTRACT The present article aims at highlighting the strengths and weaknesses of the so-called s... more ABSTRACT The present article aims at highlighting the strengths and weaknesses of the so-called spectral-like optimized (explicit central) finite-difference schemes, when the latter are used for numerically approximating spatial derivatives in aeroacoustics evolution problems. With that view, we first remind how differential operators can be approximated using explicit central finite-difference schemes. The possible spectral-like optimization of the latter is then discussed, the advantages and drawbacks of such an optimization being theoretically studied, before they are numerically quantified. For doing so, two popular spectral-like optimized schemes are assessed via a direct comparison against their standard counterparts, such a comparative exercise being conducted for several academic test cases. At the end, general conclusions are drawn, which allows us discussing the way spectral-like optimized schemes shall be preferred (or not) to standard ones, when it comes to simulate real-life aeroacoustics problems.