Scaling of mixed structure functions in turbulent boundary layers

We address the issue of the scaling of the anisotropic components of the hierarchy of correlation tensors in the logarithmic region of a turbulent boundary layer over a flat plate, at Re?15000. We isolate the anisotropic observables by means of decomposition tools based on the SO(3) symmetry group of rotations. By employing a dataset made of velocity signals detected by two X probes, we demonstrate that the behavior of the anisotropic fluctuations throughout the boundary layer may be understood in terms of the superposition of two distinct regimes. The transition is controlled by the magnitude of the mean shear and occurs in correspondence with the shear scale. Below the shear scale, an isotropy-recovering behavior occurs, which is characterized by a set of universal exponents which roughly match dimensional predictions based on Lumley's argument [J. L. Lumley, Phys. Fluids 8, 1056 (1965)]. Above the shear scale, the competition between energy production and transfer mechanisms gives rise to a completely different scenario with strong alterations of the observed scaling laws. This aspect has significant implications for the correct parametrization of the anisotropy behavior in the near wall region since, approaching the wall, an increasingly larger fraction of the scaling interval tends to conform to the shear-dominated power laws

Probability density function of turbulent velocity fluctuations in rough-wall boundary layer

The probability density function of single-point velocity fluctuations in turbulence is studied systematically using Fourier coefficients in the energy-containing range. In ideal turbulence where energy-containing motions are random and independent, the Fourier coefficients tend to Gaussian and independent of each other. Velocity fluctuations accordingly tend to Gaussian. However, if energy-containing motions are intermittent or contaminated with bounded-amplitude motions such as wavy wakes, the Fourier coefficients tend to non-Gaussian and dependent of each other. Velocity fluctuations accordingly tend to non-Gaussian. These situations are found in our experiment of a rough-wall boundary layer.Comment: 6 pages, to appear in Physical Review

TEACHERS' OPINIONS RELATED TO THE EXTENT OF CRITICAL MANAGEMENT SKILLS FOR PRINCIPALS

Günümüz değişen okul yönetimi bağlamında, müdürlerin yönetimi becerileri önem kazanmaktadır. Bu çalışma çeşitli yönetim becerilerinin okul müdürleri için önem derecelerini öğretmen görüşleriyle belirleyebilmeyi amaçlamıştır. Çalışma kapsamında öğretmen görüşlerinin kişisel özelliklere göre farklılarına bakılmıştır. Sonuçlar öğretmenlerin, okul müdürlerinin yönetim becerilerini "yüksek" düzeyde önemli gördüklerini ortaya koymuştur. Ayrıca bireysel farkındalık becerileri alt boyutunda kadın ve erkek öğretmenlerin görüşleri arasında farklılık olduğu ve bu farklılığın kadın öğretmenlerin lehine olduğu gözlenmiştir. Aynı alt boyutta, okul müdürü olmak isteyen öğretmenler ile okul müdürü olmak istemeyen öğretmenlerin görüşleri arasında müdür olmak isteyenler lehine farklılık olduğu görülmüştür. Kıdem değişkenine göre de katılımcı görüşleri arasında farklılıklar bulunmuştur. En önemli yönetim becerileri olarak ise birinci sırada"Personelin nasıl değerlendirileceği"; ikinci sırada "Eğitim sistemi içinde bulunan herkesin (aile, çevre vb.) eğitim-öğretim sürecine katılımını cesaretlendirmek"; üçüncü sırada ise "Öğrenciler üzerinde katkı sağlayıcı farklılıklar yaratabilme arzusunu göstermek" olarak sıralanmıştır. The changing context of school management in our age makes principals' management skills important. This study aimed to reveal teachers' opinions related to the extent of critical management skills for principals. It also aimed to explore if there were any differences in teachers' opinions with regard to their demographic variables. Results showed that teachers think that the extents of management skills for principals were critical on a high degree. In addition the results showed that female teachers were more concerned about those critical skills in self-awareness dimension. In the same dimension, there was a statistically significant difference between teachers who planned to be a principal and teachers who did not. According to teachers' opinions, the item "how to assess staff" was the most important skill for principals, the second was "ability to encourage involvement by all parties in the educational system", and the third was "demonstrating a desire to make a significant difference in the lives of students.

Obtaining accurate mean velocity measurements in high Reynolds number turbulent boundary layers using Pitot tubes

This article reports on one component of a larger study on measurement of the zero-pressure-gradient turbulent flat plate boundary layer, in which a detailed investigation was conducted of the suite of corrections required for mean velocity measurements performed using Pitot tubes. In particular, the corrections for velocity shear across the tube and for blockage effects which occur when the tube is in close proximity to the wall were investigated using measurements from Pitot tubes of five different diameters, in two different facilities, and at five different Reynolds numbers ranging from Re_θ = 11 100 to 67 000. Only small differences were found amongst commonly used corrections for velocity shear, but improvements were found for existing near-wall proximity corrections. Corrections for the nonlinear averaging of the velocity fluctuations were also investigated, and the results compared to hot-wire data taken as part of the same measurement campaign. The streamwise turbulence-intensity correction was found to be of comparable magnitude to that of the shear correction, and found to bring the hot-wire and Pitot results into closer agreement when applied to the data, along with the other corrections discussed and refined here

Elastic and vibrational properties of alpha and beta-PbO

The structure, electronic and dynamic properties of the two layered alpha (litharge) and beta (massicot) phases of PbO have been studied by density functional methods. The role of London dispersion interactions as leading component of the total interaction energy between layers has been addressed by using the Grimme's approach, in which new parameters for Pb and O atoms have been developed. Both gradient corrected and hybrid functionals have been adopted using Gaussian-type basis sets of polarized triple zeta quality for O atoms and small core pseudo-potential for the Pb atoms. Basis set superposition error (BSSE) has been accounted for by the Boys-Bernardi correction to compute the interlayer separation. Cross check with calculations adopting plane waves that are BSSE free have also been performed for both structures and vibrational frequencies. With the new set of proposed Grimme's type parameters structures and dynamical parameters for both PbO phases are in good agreement with experimental data.Comment: 8 pages, 5 figure

Significant locus and metabolic genetic correlations revealed in genome-wide association study of anorexia nervosa

OBJECTIVE: The authors conducted a genome-wide association study of anorexia nervosa and calculated genetic correlations with a series of psychiatric, educational, and metabolic phenotypes. METHOD: Following uniform quality control and imputation procedures using the 1000 Genomes Project (phase 3) in 12 case-control cohorts comprising 3,495 anorexia nervosa cases and 10,982 controls, the authors performed standard association analysis followed by a meta-analysis across cohorts. Linkage disequilibrium score regression was used to calculate genome-wide common variant heritability (single-nucleotide polymorphism [SNP]-based heritability [h2SNP]), partitioned heritability, and genetic correlations (rg) between anorexia nervosa and 159 other phenotypes. RESULTS: Results were obtained for 10,641,224 SNPs and insertion-deletion variants with minor allele frequencies >1% and imputation quality scores >0.6. The h2SNP of anorexia nervosa was 0.20 (SE=0.02), suggesting that a substantial fraction of the twin-based heritability arises from common genetic variation. The authors identified one genome-wide significant locus on chromosome 12 (rs4622308) in a region harboring a previously reported type 1 diabetes and autoimmune disorder locus. Significant positive genetic correlations were observed between anorexia nervosa and schizophrenia, neuroticism, educational attainment, and high-density lipoprotein cholesterol, and significant negative genetic correlations were observed between anorexia nervosa and body mass index, insulin, glucose, and lipid phenotypes. CONCLUSIONS: Anorexia nervosa is a complex heritable phenotype for which this study has uncovered the first genome-wide significant locus. Anorexia nervosa also has large and significant genetic correlations with both psychiatric phenotypes and metabolic traits. The study results encourage a reconceptualization of this frequently lethal disorder as one with both psychiatric and metabolic etiology

Job strain and the risk of severe asthma exacerbations : a meta-analysis of individual-participant data from 100 000 European men and women

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