Acoustic receptivity and transition modeling of Tollmien-Schlichting disturbances induced by distributed surface roughness

Acoustic receptivity to Tollmien-Schlichting waves in the presence of surface roughness is investigated for a flat plate boundary layer using the time-harmonic incompressible linearized Navier-Stokes equations. It is shown to be an accurate and efficient means of predicting receptivity amplitudes, and therefore to be more suitable for parametric investigations than other approaches with DNS-like accuracy. Comparison with literature provides strong evidence of the correctness of the approach, including the ability to quantify non-parallel flow effects. These effects are found to be small for the efficiency function over a wide range of frequencies and local Reynolds numbers. In the presence of a two-dimensional wavy-wall, non-parallel flow effects are quite significant, producing both wavenumber detuning and an increase in maximum amplitude. However, a smaller influence is observed when considering an oblique Tollmien-Schlichting wave. This is explained by considering the non-parallel effects on receptivity and on linear growth which may, under certain conditions, cancel each other out. Ultimately, we undertake a Monte-Carlo type uncertainty quantification analysis with two-dimensional distributed random roughness. Its power spectral density (PSD) is assumed to follow a power law with an associated uncertainty following a probabilistic Gaussian distribution. The effects of the acoustic frequency over the mean amplitude of the generated two-dimensional Tollmien-Schlichting waves are studied. A strong dependence on the mean PSD shape is observed and discussed according to the basic resonance mechanisms leading to receptivity. The growth of Tollmien-Schlichting waves is predicted with non-linear parabolized stability equations computations to assess the effects of stochasticity in transition location

Magnetism and Electronic Correlations in Quasi-One-Dimensional Compounds

In this contribution on the celebration of the 80th birthday anniversary of Prof. Ricardo Ferreira, we present a brief survey on the magnetism of quasi-one-dimensional compounds. This has been a research area of intense activity particularly since the first experimental announcements of magnetism in organic and organometallic polymers in the mid 80s. We review experimental and theoretical achievements on the field, featuring chain systems of correlated electrons in a special AB2 unit cell structure present in inorganic and organic compounds

Laboratório de Microbiologia.

Laboratório de Microbiologia.info:eu-repo/semantics/publishedVersio

Incerteza e redefinições do trabalho médico : um estudo de caso sobre o aconselhamento genético no cancro hereditário

O presente artigo resulta de um trabalho de investigação sociológica sobre a incerteza médica no contexto do aconselhamento genético na área do cancro hereditário. Tendo como base um estudo de caso que foi desenvolvido no âmbito de uma consulta de risco familiar numa unidade hospitalar especializada em oncologia, procuram-se identificar e analisar as novas dimensões de incerteza que emergem neste contexto clínico específico e evidenciar o modo como as mesmas enquadram e redefinem as práticas de trabalho e as formas de julgamento clínico. A perspetiva de análise que organiza a abordagem sociológica sobre estas novas formas de incerteza desenvolve-se a partir da exploração de dois eixos privilegiados relativos à especificidade do perfil científico desta área de inovação biomédica. A reconfiguração da conceção de doença e de medicina e os paradoxos da sua lógica preditiva

Apreciação ética de projectos de investigação em saúde: uma reflexão situada a propósito da ética de investigação em ciências sociais

Tomando como ponto de partida uma experiência de colaboração numa comissão de ética de saúde, a presente proposta procura constituir-se como um exercício reflexivo sobre o percurso de participação decorrente do vínculo formal a uma estrutura desta natureza. No entanto, mais do que apenas apresentar um testemunho pessoal que ponha em evidência a visão de um sociólogo relativamente à integração e participação num órgão colegial e multidisciplinar orientado para as questões da saúde, ensaio um exercício analítico orientado para a compreensão e discussão das particularidades do papel e da acção desta estrutura em matéria de apreciação e deliberação ética de projectos de investigação.info:eu-repo/semantics/publishedVersio

Acoustic-roughness receptivity in subsonic boundary-layer flows over aerofoils

The generation of a viscous–inviscid instability through scattering of an acoustic wave by localised and distributed roughness on the upper surface of a NACA 0012 aerofoil is studied with a time-harmonic compressible adjoint linearised Navier–Stokes approach. This extends previous work by the authors dedicated to flat plate geometries. The key advancement lies in the modelling of the inviscid acoustic field external to the aerofoil boundary layer, requiring a numerical solution of the convected Helmholtz equation in a non-uniform inviscid field to determine the unsteady pressure field on the curved aerofoil surface. This externally imposed acoustic pressure field subsequently drives the acoustic boundary layer, which fundamentally determines the amplitudes of acoustic-roughness receptivity. A study of receptivity in the presence of Gaussian-shaped roughness and sinusoidally distributed roughness at Mach number M∞ = 0.4 and Strouhal numbers S ≈ {46, 69, 115} shows the effects of various parameters, most notably angle of attack, angle of incidence of the externally imposed plane acoustic wave and geometry of surface roughness; the latter is varied from viewpoint of its placement on the aerofoil surface and its wavelength. The parametric study suggests that non-parallel effects are quite substantial and that considerable differences arise when using parallel flow theory to estimate the optimal width of Gaussian-shaped roughness elements to provoke the greatest response. Furthermore, receptivity amplitudes for distributed roughness are observed to be generally higher for lower angles of attack, i.e. for less adverse pressure gradients. It is also shown that the boundary layer is more receptive to upstream-travelling acoustic waves

A simple and easy-to-prepare imidazole-based probe for the selective chromo-fluorogenic Cu(II) detection in aqueous environments

Synthesis and evaluation of the chromo-fluorogenic chemosensor ability of imidazole derivatives in organic solventes and in aqueous media.info:eu-repo/semantics/publishedVersio

Alterations in heterosis of maize populations derived from single-cross hybrids after reciprocal recurrent selection.

One hundred and sixty-nine interpopulational half sib progenies were obtained from maize populations derived from the commercial single-cross hybrids AG9012 (1) and C333 (2) to investigate the efficiency of reciprocal recurrent selection (RRS). Fifteen progenies with highest hulled ear yield were obtained. Two recombination trials were sown with remnant S1 seeds, and the improved CI1 and CI2 populations were simultaneously obtained with their hybrid combination. Yield trials were set up in three sites to assess the efficiency of the RRS. The F1 from single-cross hybrid AG9012 and C333, the double-cross (F1(1)x F1(2) hybrids, the C0 1 and C02 populations, the interpopulational hybrid (C01 x C02), the CI1 and CI2 improved populations, and their hybrid (CI1 x CI2) were compared. A 5.7% progress was obtained in one cycle of RRS for ear yield, mainly attributed to increased heterosis. The yield of the improved hybrid was superior to the F1 from single-cross hybrids AG9012 and C333, demonstrating the potential of the referred hybrid combination. Para verificar a eficiência da seleção recorrente recíproca (SRR) em populações originárias dos híbridos simples comerciais AG9012 (1) e C333 (2) foram obtidas, inicialmente, 169 progênies de meios-irmãos interpopulacionais. As 15 melhores progênies em produção de espigas despalhadas foram identificadas. Utilizando-se sementes S1 remanescentes, semearam-se dois campos de recombinação, sendo simultaneamente obtidas as populações melhoradas C1 1 e C1 2 e a combinação híbrida entre elas. Os experimentos para avaliar a eficiência da SRR foram instalados em três locais. Foram comparados o F1 dos híbridos simples AG9012 e C333, o híbrido duplo F1(1) x F1 (2), entre eles as populações CD1 e CD2, o híbrido interpopulacinal (CD1 e CD2), as populações melhoradas C1 1 e C1 2 e a sua combinação híbrida (C1 1 e C 1 2). O progresso com um ciclo de SRR foi de 5,7% para a produção de espigas e deveu-se , principalmente, ao incremento na heterose. O desempenho do híbrido melhorado superou a geração F1 dos híbridos simples AG9012 e C333, evidenciando o potencial da referida combinação híbrida

a quantitative approach

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