184,077 research outputs found
On the structure and origin of pressure fluctuations in wall turbulence: predictions based on the resolvent analysis
Get PDFWe generate predictions for the fluctuating pressure field in turbulent pipe flow by re-formulating the resolvent analysis of McKeon & Sharma (2010) in terms of the so-called primitive variables. Under this analysis, the nonlinear convective terms in the Fourier-transformed Navier-Stokes equations are treated as a forcing that is mapped to a velocity and pressure response by the resolvent of the linearized Navier-Stokes operator. At each wavenumber-frequency combination, the turbulent velocity and pressure field are represented by the most-amplified (rank-1) response modes, identified via a singular value decomposition of the resolvent. We show that these rank-1 response modes reconcile many of the key relationships between the velocity field, coherent structure (i.e., hairpin vortices), and the high-amplitude wall-pressure events observed in previous experiment and DNS. A Green’s function representation shows that the pressure fields obtained under this analysis correspond primarily to the fast pressure contribution arising from the linear interaction between the mean shear and the turbulent wall-normal velocity. Recovering the slow pressure requires an explicit treatment of the nonlinear interactions between the Fourier response modes. By considering the velocity and pressure fields associated with the triadically-consistent mode combination studied by Sharma & McKeon (2013), we identify the possibility of an apparent amplitude modulation effect in the pressure field, similar to that observed for the streamwise velocity field. However, unlike the streamwise velocity, for which the large scales of the flow are in phase with the envelope of the small-scale activity close to the wall, we expect there to be a ?/2 phase difference between the large scale wall-pressure and the envelope of the small-scale activity. Finally, we generate spectral predictions based on a rank-1 model assuming broadband forcing across all wavenumber-frequency combinations. Despite the significant simplifying assumptions, this approach reproduces trends observed in previous DNS for the wavenumber spectra of velocity and pressure, and for the scale-dependence of wall-pressure propagation speed
Resistência de cultivares de trigo ao nematóide formador de galhas Meloidogyne javanica.
No full textA cultura do trigo (Triticum aestivum L.) é uma cultura importante para a região do Sul do Brasil, mostrando boa adaptação para a região dos Cerrados e é cultivado em pequenas áreas do Estado de Goiás, Bahia, Minas Gerais, Mato Grosso do Sul e Distrito Federal. As informações sobre perdas causadas por nematoides das regiões de cerrados são deficientes. SHARMA (1979) pela primeira vez registrou ocorrência de nematoides fitoparasitos na cultura de trigo nos Cerrados do Distrito Federal. O nematoide formador de galhas, Meloidogyne javanica Treub,1885) Chitwood,1949, foi encontrado causando sérios danos à cultura do trigo. Posteriormente, o autor verificou a patogenicidade do referido nemat6ide em condições de casa-de-vegetação e simultaneamente foram feitas avaliações de resistência de 21 cultivares de trigo ao mesmo nematoide
Critical theories in dark tourism: Over the years and beyond.
No full textThe chapters in this volume have highlighted different issues of contemporary relevance in dark tourism studies and theoretical perspectives related to affect and emotions, critical animal studies, critical memory studies, identity, power, and ideology. In doing so, they draw attention to pertinent issues in dark tourism that are often overlooked such as climate change, misogyny, emotional labor, refugees and migration, animal ethics, colonial legacies, and power hierarchies. In the future, we anticipate more studies on dark tourism from across the globe that contribute to theoretical progress, methodological advancements, and pragmatic solutions, and we hope this edited volume can be a starting point for future reflections. The Introduction chapter provides a broad compilation of critical theories that have been used to examine dark tourism and lays the foundation for future theoretical advancements. This final chapter reflects on some of the key underlying themes that have emerged from the current chapters that shed light on how the theoretical foundations of dark tourism have shifted and are likely to change in the coming years
Opposition control within the resolvent analysis framework
Get PDFThis paper extends the resolvent analysis of McKeon & Sharma (2010) to consider flow control techniques that employ linear control laws, focusing on opposition control (Choi et al. 1994) as an example. Under this formulation, the velocity field for turbulent pipe flow is decomposed into a series of highly amplified (rank-1) response modes, identified from a gain analysis of the Fourier-transformed Navier-Stokes equations. These rank-1 velocity responses represent propagating structures of given streamwise/spanwise wavelength and temporal frequency, whose wall-normal footprint depends on the phase speed of the mode. Opposition control, introduced via the boundary condition on wall-normal velocity, affects the amplification characteristics (and wall-normal structure) of these response modes; a decrease in gain indicates mode suppression, which leads to a decrease in the drag contribution from that mode. With basic assumptions, this rank-1 model reproduces trends observed in previous DNS and LES, without requiring high-performance computing facilities. Further, a wavenumber-frequency breakdown of control explains the deterioration of opposition control performance with increasing sensor elevation and Reynolds number. It is shown that slower-moving modes localized near the wall (i.e. attached modes) are suppressed by opposition control. Faster-moving detached modes, which are more energetic at higher Reynolds number and more likely to be detected by sensors far from the wall, are further amplified. These faster-moving modes require a phase lag between sensor and actuator velocity for suppression. Thus, the effectiveness of opposition control is determined by a trade-off between the modes detected by the sensor. However, it may be possible to develop control strategies optimized for individual modes. A brief exploration of such mode-optimized control suggests the potential for significant performance improvement
Harmonic Algorithms for Packing d-Dimensional Cuboids into Bins
Get PDFWe explore approximation algorithms for the d-dimensional geometric bin packing problem (dBP). Caprara [Caprara, 2008] gave a harmonic-based algorithm for dBP having an asymptotic approximation ratio (AAR) of (T_∞)^{d-1} (where T_∞ ≈ 1.691). However, their algorithm doesn't allow items to be rotated. This is in contrast to some common applications of dBP, like packing boxes into shipping containers. We give approximation algorithms for dBP when items can be orthogonally rotated about all or a subset of axes. We first give a fast and simple harmonic-based algorithm having AAR T_∞^d. We next give a more sophisticated harmonic-based algorithm, which we call HGaP_k, having AAR (T_∞)^{d-1}(1+ε). This gives an AAR of roughly 2.860 + ε for 3BP with rotations, which improves upon the best-known AAR of 4.5. In addition, we study the multiple-choice bin packing problem that generalizes the rotational case. Here we are given n sets of d-dimensional cuboidal items and we have to choose exactly one item from each set and then pack the chosen items. Our algorithms also work for the multiple-choice bin packing problem. We also give fast and simple approximation algorithms for the multiple-choice versions of dD strip packing and dD geometric knapsack
Vitamin D Intoxication in An Elderly: A Case Report
Get PDFVitamin D is a very common prescribed drug for numerous indications. Due to scarce knowledge and poor awareness of the various formulations, preparations and dosages of Vitamin D, there are many chances of prescription errors, medication errors, product use issue and undesirable adverse drug reactions. We hereby detail case of 70-year-old ex-army gentleman reported to us with a history of lethargy, confusion, reduced appetite and gait imbalance since few days with a history of knee replacement surgery 2 years back. Medical history was not of much relevance before it was revealed that he was getting cholecalciferol injection with a strength of 600000 IU once a week for few months. He was detected to have very high serum vitamin D level and hypercalcemia. He was started on intravenous fluids, diuretics and glucocorticoids. In a few days, after effective treatment, the patient was discharged in a recovering stage and advised to stop intake calcium and vitamin D in any form. At his last follow up, after a few months of discharge, he had totally recovered
MeSH term explosion and author rank improve expert recommendations
Get PDFInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Sharma et sa région
No full textInternational audienceResults of the survey in the surrounding of Sharma (Hadramawt, Yemen
Sharma et sa région
No full textInternational audienceResults of the survey in the surrounding of Sharma (Hadramawt, Yemen
Guptioxylon endocentrica sp. nov. du Jurassique d'Amarjola dans les Rajmahal Hills (Inde)
No full textSharma B. D. Guptioxylon endocentrica sp. nov. du Jurassique d'Amarjola dans les Rajmahal Hills (Inde). In: Bulletin mensuel de la Société linnéenne de Lyon, 41ᵉ année, n°6, juin 1972. pp. 114-120
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