An analytical study of transport, mixing and chaos in an unsteady vortical flow

We examine the transport properties of a particular two-dimensional, inviscid incompressible flow using dynamical systems techniques. The velocity field is time periodic and consists of the field induced by a vortex pair plus an oscillating strainrate field. In the absence of the strain-rate field the vortex pair moves with a constant velocity and carries with it a constant body of fluid. When the strain-rate field is added the picture changes dramatically; fluid is entrained and detrained from the neighbourhood of the vortices and chaotic particle motion occurs. We investigate the mechanism for this phenomenon and study the transport and mixing of fluid in this flow. Our work consists of both numerical and analytical studies. The analytical studies include the interpretation of the invariant manifolds as the underlying structure which govern the transport. For small values of strain-rate amplitude we use Melnikov's technique to investigate the behaviour of the manifolds as the parameters of the problem change and to prove the existence of a horseshoe map and thus the existence of chaotic particle paths in the flow. Using the Melnikov technique once more we develop an analytical estimate of the flux rate into and out of the vortex neighbourhood. We then develop a technique for determining the residence time distribution for fluid particles near the vortices that is valid for arbitrary strainrate amplitudes. The technique involves an understanding of the geometry of the tangling of the stable and unstable manifolds and results in a dramatic reduction in computational effort required for the determination of the residence time distributions. Additionally, we investigate the total stretch of material elements while they are in the vicinity of the vortex pair, using this quantity as a measure of the effect of the horseshoes on trajectories passing through this region. The numerical work verifies the analytical predictions regarding the structure of the invariant manifolds, the mechanism for entrainment and detrainment and the flux rate

Laser propulsion

The use of an earth-based high-power laser beam to provide energy for earth-launched rocket vehicle is investigated. The laser beam energy is absorbed in an opaque propellant gas and is converted to high-specific-impulse thrust by expanding the heated propellant to space by means of a nozzle. This laser propulsion scheme can produce specific impulses of several thousand seconds. Payload to gross-weight fractions about an order of magnitude higher than those for conventional chemical earth-launched vehicles appear possible. There is a potential for a significant reduction in cost per payload mass in earth orbit

Evaluation of cover crops in high tunnel vegetable rotation

Organic vegetable production within high tunnels allows for an extended growing season, crop protection, and environmental control. The USDA National Organic Program (NOP) standards mandate evidence that the soil has been maintained and improved over the course of production. Previous studies have indicated the potential of cover crops for reducing competitive vegetation, and improving soil quality, thus resulting in greater plant growth, nutrient uptake, and yield. However, there has been limited work in the confines of high tunnels as part of a tunnel-system rotation. Ten nitrogen-fixing and ten non-legume cover crops were established under a high tunnel and evaluated for their effects on the yield of ‘De Cicco’ broccoli (Brassica oleracea L. var. italica) and ‘Champion’ collards (Brassica oleracea L. var. acephala), aboveground biomass, and plant C and N contents. All treatments received recommended levels of appropriate certified organic fertilizers, water status was maintained, and vegetables received standard organic maintenance for insects and disease. The cover crops hairy indigo (Indigofera hirsuta L.), Catjang cowpea (Viana unguicalata L.), and Sunn hemp (Crotalaria juncea L.) consistently produced higher yields than Tifleaf III hybrid pearl millet (Pennisetum glaucum L.), Dairymaster brown midrib (BMR) hybrid grain sorghum (Sorghum spp.), and Wild Game Food sorghum (Sorghum bicolor L.). Nitrogenfixing legumes produced horticulturally significantly higher yields than the non-nitrogen-fixing grass species. This experiment demonstrated that not all cover crops are equal; they created variation in response. Cover crops provide a viable option for organic producers to maintain or improve soil quality over the course of production

Self-assessment of word knowledge with graded readers: A preliminary study

The study investigated how second language (L2) learners self-assessed word knowledge on a page of text taken from a graded reader. The case study subjects were five Thai high school learners of English. They were asked to assess their word knowledge using a page of continuous text. Data gained through observation, interviews, self-assessment and a translation test showed that such self-assessment of word knowledge resulted in learners using various reading techniques from simple translation to more complicated guessing from context. The results provide some insight into how self-assessment of word knowledge with graded readers is carried out and provides evidence to support the value of self-assessment as an easy procedure to direct learners to an appropriate reading level as suggested by the scholars in the field (Bamford & Day, 2004; Day & Bamford, 1998; Waring, 1997). Suggestions for pedagogical practice are given

Symmetry breaking perturbations and strange attractors

The asymmetrically forced, damped Duffing oscillator is introduced as a prototype model for analyzing the homoclinic tangle of symmetric dissipative systems with \textit{symmetry breaking} disturbances. Even a slight fixed asymmetry in the perturbation may cause a substantial change in the asymptotic behavior of the system, e.g. transitions from two sided to one sided strange attractors as the other parameters are varied. Moreover, slight asymmetries may cause substantial asymmetries in the relative size of the basins of attraction of the unforced nearly symmetric attracting regions. These changes seems to be associated with homoclinic bifurcations. Numerical evidence indicates that \textit{strange attractors} appear near curves corresponding to specific secondary homoclinic bifurcations. These curves are found using analytical perturbational tools

Workers' Compensation

Apresentação do tema em debate sobre a "qualidade da vida"

El valor de los paradigmas de la historia del arte en la práctica del diseño gráfico

La historia del arte, en su camino para erigirse como una ciencia, ha ido adoptando y adaptando distintas metodologías de trabajo dependientes de los conocimientos y la cultura de cada época. En otras palabras, ha ido añadiendo prismas bajo los que observar su objeto de estudio, -la obra de arte-, que han dotado a la teoría del arte de una riqueza de interpretaciones y formas de acercarse a las imágenes de las que la teoría del diseño carece o bien aplica de forma más bien intuitiva y sin fundamentación teórica. Sin embargo, resulta algo evidente que las imágenes, sus formas, sus significados, así como lo que comunican son una parte consustancial del diseño gráfico. En este trabajo tratamos de descubrir si el conocimiento de la historia del arte resulta útil a los diseñadores. Creemos interesante saber si la investigación que proponemos armoniza con las necesidades profesionales del diseño y para observar si los métodos de análisis de la obra de arte son aplicables al diseño gráfico pretendemos conocer la opinión de los diseñadores sobre la utilidad de los diferentes paradigmas metodológicos del estudio del arte en relación a su actividad profesional. Por tanto, realizamos un cuestionario online a 274 diseñadores gráficos repartidos principalmente en Catalunya, Madrid, País Vasco, Valencia y Andalucía que nos ha permitido descubrir que los diseñadores gráficos se interesan especialmente por aquellos métodos que contribuyen a aportar conocimientos críticos sobre la realización formal de las piezas -ya sean pinturas o infografías- y sobre sus contenidos y significados.Art history, on its way to establish itself as a science, has been adopting and adapting different methods of work dependent knowledge and culture of each era. In other words, it has been adding prisms under which observe its subject, -the work of art, which have endowed art theory of a wealth of interpretations and ways of approaching the images that theory no design or applied rather intuitively and without theoretical foundation. However, it is evident that the images, forms, their meanings and what they communicate is an essential part of graphic design.In this paper we try to discover if knowledge of art history is useful to designers. We believe interesting to know whether the research we propose harmonizes with professional design needs and to see if the methods of analysis of the artwork are applicable to graphic design pretend to know the opinion of the designers on the usefulness of the different methodological paradigms of the study art in relation to their professional activity. Therefore, we conducted an online questionnaire to 274 graphic designers spread mainly in Catalonia, Madrid, Basque Country, Valecia and Andalusia that has allowed us to discover that graphic designers are especially interested in methods that help provide critical knowledge of the formal aspects of the pieces are paintings or-and infografías- and their content and meaning

Digging Deeper: Art Museums in Las Vegas?

[Excerpt] Las Vegas has been called the “city of reinvention” (Douglass and Raento 2003). Part of its more recent reinvention efforts has included the opening of five fine-art venues. However, one of the art museums––the Las Vegas Guggenheim––was shut down in its first year due to low attendance; another, the Bellagio Fine Art Gallery, has seen attendance dwindle (Schemeligian 2004). The question addressed here is whether the museums are bringing the intended intangible benefits to the host resort, or whether the sales and attendance figures represent overall disinterest. More broadly one considers the potential “fit” between sin-city and the high-art cultural world. The difficulty in addressing these issues is that tourists might not consciously recognize the value they feel about having a worldclass art museum onsite. Within nonprofit research there has been a call for ‘‘deeper understanding’’ of tourists (Thyne 2001) as reflected within the greater interest in new qualitative methodologies (Riley and Love 2000). The Zaltman metaphor elicitation technique, a patented research method, was chosen to investigate this research issue. Many of the world’s largest companies (such as Procter & Gamble) have utilized this method for insight on brand meaning and competitive positioning