Variational approach to the closure problem of turbulence theory

A new method is proposed to solve the closure problem of turbulence theory and to drive the Kolmogorov law in an Eulerian framework. Instead of using complex Fourier components of velocity field as modal parameters, a complete set of independent real parameters and dynamic equations are worked out to describe the dynamic states of a turbulence. Classical statistical mechanics is used to study the statistical behavior of the turbulence. An approximate stationary solution of the Liouville equation is obtained by a perturbation method based on a Langevin-Fokker-Planck (LFP) model. The dynamic damping coefficient eta of the LFP model is treated as an optimum control parameter to minimize the error of the perturbation solution; this leads to a convergent integral equation for eta to replace the divergent response equation of Kraichnan's direct-interaction (DI) approximation, thereby solving the closure problem without appealing to a Lagrangian formulation. The Kolmogorov constant Ko is evaluated numerically, obtaining Ko = 1.2, which is compatible with the experimental data given by Gibson and Schwartz, (1963).

On the non-linear stability theory of spinning solid bodies with liquid-filled cavities and its application to the columbus problem

In this paper, we first present a system of differential-integral equations for the largedisturbance to the general case that any arbitrarily shaped solid body with a cavity contain-ing viscous liquid rotates uniformly around the principal axis of inertia, and then develop aweakly non-linear stability theory by the Lyapunov direct approach. Applying this theoryto the Columbus problem, we have proved the consistency between the theory and Kelvin'sexperiments.

The Stability of the Roommate Problem Revisited

The lack of stability in some matching problems suggests that alternative solution concepts to the core might be applied to find predictable matchings. We propose the absorbing sets as a solution for the class of roommate problems with strict preferences. This solution, which always exists, either gives the matchings in the core or predicts some other matchings when the core is empty. Furthermore, it satisfies an interesting property of outer stability. We also characterize the absorbing sets, determine their number and, in case of multiplicity, we find that they all share a similar structure.

¿Enseñar a leer en la Universidad? Una intervención para mejorar la comprensión de textos complejos al comienzo de la educación superior.

[Es] Leer textos es una actividad frecuente entre los alumnos universitarios y constituye una exigencia habitual de gran parte del profesorado. Sin embargo, se percibe una queja bastante unánime respecto a las deficiencias que se detectan entre los estudiantes que acceden a la universidad en relación con esta destreza básica, que actúa como soporte de los aprendizajes programados.Desde la convicción de que ignorar esta situación no resuelve sino que agrava el problema, este artículo pretende exponer los resultados de una investigación consistente en diseñar, aplicar y evaluar la eficacia de un plan de intervención para mejorar la comprensión de textos escritos complejos en estudiantes universitarios.

Irakurle konpetenteak lortze aldera

[EUS] Irakurriaren ulermenaren eremu ezin zabalagora hurbiltzeko hainbat arlo ukituko ditugu artikulu honetan. Lehenik eta behin, gai honen gaineko garraztasunak arintzeko Wiki bat diseinatu dugu eta bertan hainbat atal ikuskatuko ditugu. Wiki hau, Lehen Hezkuntzako nahiz DBHko hainbat irakasleekin landu da, beti ere, irakurriaren ulermena eskolan zertan hobetu daitekeen ikusteko. Beraz, artikuluarekin batera wikiaren jarraipena egitea gomendatzen da. Hona hemen helbidea: www.letutaletu.wikispaces.com . Artikulu honek lau atal aski diferente izango ditu. Atal hauen helbururik behiena, Lehen Hezkuntzako hirugarren zikloko nahiz DBHko lehenengo zikloko irakasleei zein ikasleei irakurriaren ulermenaren gaineko hainbat lanabes praktiko ematea litzateke. Horretarako, lehen atalean, eskolak irakurriaren ulermenaren gainean diagnosia egin dezan hainbat gogoeta ekarpen gisara planteatuko dira. Bigarrenik, irakasleek klaseetan irakurketa estrategiak lan ditzaten lan eskema bat proposatuko da. Hirugarrenik, azalpen testuek dituzten zailtasunen inguruan hausnartuko da eta zailtasun horiek gainditze aldera irakasleari hainbat erreminta emango zaizkio. Eta azkenik, bibliografiak edota irakurketak errazteko hainbat ekarpen egingo dira.

Irakurriaren ulermenaren zailtasunak bigarren hezkuntzan

(FR)Ce texte reprend la question de la compréhension de lecture et la faible note que nos étudiants du secondaire donnent à ce secteur, d’après PISA. De plus en plus de voix s’élèvent pour réclamer que la compréhension de lecture soit une des tâches de tous les professeurs et plus seulement des professeurs de langue et littérature. Lors de la préparation au métier d’enseignant, de plus en plus de cours sont organisés en rapport avec cette question de plus en plus préoccupante dans ce secteur. Les données sont celles-ci et toutes les tentatives pour résoudre ce problème semblent insuffisantes si on ne reprend pas la question au niveau du Curriculum et si on prépare les professeurs aux stratégies de lecture pour que les élèves parviennent à être des lecteurs compétents.

Analysis of micro-indentation problem of a soft film on a hard substrate

Two stages have been observed in micro-indentation experiment of a soft film on a hard substrate. In the first stage, the hardness of the thin film decreases with increasing depth of indentation when indentation is shallow; and in the second stage, the hardness of the film increases with increasing depth of indentation when the indenter tip approaches the hard substrate. In this paper, the new strain gradient theory is used to analyze the micro-indentation behavior of a soft film on a hard substrate. Meanwhile, the classic plastic theory is also applied to investigating the problem. Comparing two theoretical results with the experiment data, one can find that the strain gradient theory can describe the experiment data at both the shallow and deep indentation depths quite well, while the classic theory can't explain the experiment results.

Technology to support your reading

This guidance supported by a range of partner organisations including the National Union of Students gives you an overview of what you should expect, why you should expect it and organisations that can give further support. TDL

Delivering trans-national education: Reading at Malaysia

Supporting slides as part of the Janet network end to end performance initiative workshop

Precision of age determination of northern offshore spotted dolphins.

We investigated within- and between-reader precision in estimating age for northern offshore spotted dolphins and possible effects on precision from the sex and age-class of specimens. Age was estimated from patterns of growth layer groups i n the dentine and cementum of the dolphins' teeth. Each specimen was aged at least three times by each of two persons. Two data samples were studied. The first comprised 800 of each sex from animals collected during 1973-78. The second included 45 females collected during 1981. There were significant, generally downward trends through time in the estimates from multiple readings of the 1973-78 data. These trends were slight, and age distributions from last readings and mean estimates per specimen appeared to be homogeneous. The largest factor affecting precision in the 1973-78 data set was between-reader variation. In light of the relatively high within-reader precision (trends considered), the consistent between-reader differences suggest a problem of accuracy rather than precision for this series. Within-reader coefficients of variation averaged approximately 7% and 11%. Pooling the data resulted i n an average coefficient of variation near 16%. Within- and between-reader precision were higher for the 1981 sample, and the data homogeneous over both factors. CVs averaged near 5% and 6% for the two readers. These results point to further refinements in reading the 1981 series. Properties of the 1981 sample may be partly responsible for greater precision: by chance there were proportionately fewer older dolphins included, and preparation and selection criteria were probably more stringent. (PDF contains 35 pages.)