The development of rhythm in young children aged one to four years

The aim of this study was to assess how young children between the ages of one and four years develop rhythm skills. The project was a pilot study conducted at 11 preschools and day care centers in Stockton, California, and included 60 children. Thirty behaviors comprised the test of various aspects of rhythmic performance. The children were video-taped and the tapes were then analyzed. By examining how many children in a particular age group could perform a particular task, a sequence became apparent. This body of research can now be used as a basis for further studies with the aim of establishing a standardized assessment scale of rhythm development and other musical skills

Discussions on Driven Cavity Flow

The widely studied benchmark problem, 2-D driven cavity flow problem is discussed in details in terms of physical and mathematical and also numerical aspects. A very brief literature survey on studies on the driven cavity flow is given. Based on the several numerical and experimental studies, the fact of the matter is, above moderate Reynolds numbers physically the flow in a driven cavity is not two-dimensional. However there exist numerical solutions for 2-D driven cavity flow at high Reynolds numbers

Low order physical models of vertical axis wind turbines

In order to examine the ability of low-order physical models of vertical axis wind turbines to accurately reproduce key flow characteristics, experimental data are presented for the mean flow patterns and turbulence spectra associated with pairs of rotating turbines, rotating solid cylinders, and stationary porous flat plates (of both uniform and non-uniform porosities). The experiments were conducted at a nominal model-diameter Reynolds number of 600 and rotation tip speed ratios between 0 and 6. By comparing the induced flow fields of the different models both qualitatively and quantitatively, it was concluded that the two dimensional horizontal mean flow fields induced by the porous flat plates were quantitatively similar to those induced by slowly rotating turbine models. However, over the range of the experimental parameters examined, the porous flat plates were unable to produce vertical flows similar to those associated with the slowly rotating turbine models. Conversely, the moderately rotating cylinders induced three dimensional mean flow fields quantitatively similar to those induced by rapidly rotating turbine models. These findings have implications for both laboratory experiments and numerical simulations, which have previously used analogous low order models in order to reduce experimental/computational costs. Specifically, over the range of parameters examined, the comparison between induced flow fields of the different model fidelities allows identification of the lowest cost model for which the specific goals of a study can be obtained, to within the desired accuracy. And if a lower fidelity model is used, it is possible to incorporate into the analysis of the collected data an understanding of how the results would be expected to vary from a higher fidelity case

Application of a dynamic subgrid-scale model to turbulent recirculating flows

The dynamic subgrid-scale model of Germano et al. is implemented in a finite volume formulation and applied to the simulation of turbulent flow in a three-dimensional lid-driven cavity at Reynolds number of 7500. The filtering operation is carried out in physical space, and the model coefficient is calculated locally. The computed mean and rms velocities as well as the Reynolds stress are compared with experimental data. It is shown that backscatter from small to large scales is necessary to sustain turbulent fluctuations. The model is being applied to the simulation of turbulent flows in a stratified and rotating environment in complex geometries

Flow Kinematics in Variable-Height Rotating Cylinder Arrays

Experimental data are presented for large arrays of rotating, variable-height cylinders in order to study the dependence of the three-dimensional mean flows on the height heterogeneity of the array. Elements in the examined arrays were spatially arranged in the same staggered paired configuration, and the heights of each element pair varied up to ±37.5% from the mean height (kept constant across all arrays), such that the arrays were vertically structured. Four vertical structuring configurations were examined at a nominal Reynolds number (based on freestream velocity and cylinder diameter) of 600 and nominal tip-speed ratios of 0, 2, and 4. It was found that the vertical structuring of the array could significantly alter the mean flow patterns. Most notably, a net vertical flow into the array from above was observed, which was augmented by the arrays' vertical structuring, showing a 75% increase from the lowest to highest vertical flows (as evaluated at the maximum element height, at a single rotation rate). This vertical flow into the arrays is of particular interest as it represents an additional mechanism by which high streamwise momentum can be transported from above the array down into the array. An evaluation of the streamwise momentum resource within the array indicates up to a 56% increase in the incoming streamwise velocity to the elements (from the lowest to highest ranking arrays, at a single rotation rate). These arrays of rotating cylinders may provide insight into the flow kinematics of arrays of vertical axis wind turbines (VAWTs). In a physical VAWT array, an increase in incoming streamwise flow velocity to a turbine corresponds to a (cubic) increase in the power output of the turbine. Thus, these results suggest a promising approach to increasing the power output of a VAWT array

Structure of mass and momentum fields over a model aggregation of benthic filter feeders

International audienceThe structure of momentum and concentration boundary layers developing over a bed of Potamocorbula amurensis clam mimics was studied. Laser Doppler velocimetry (LDV) and laser-induced fluorescence (LIF) probes were used to quantify velocity and concentration profiles in a laboratory flume containing 3969 model clams. Model clams incorporated passive roughness, active siphon pumping, and the ability to filter a phytoplankton surrogate from the flow. Measurements were made for two crossflow velocities, four clam pumping rates, and two siphon heights. Simultaneous use of LDV and LIF probes permited direct calculation of scalar flux of phytoplankton to the bed. Results show that clam pumping rates have a pronounced effect on a wide range of turbulent quantities in the boundary layer. In particular, the vertical turbulent flux of scalar mass to the bed was approximately proportional to the rate of clam pumping

Three-dimensional flow instability in a lid-driven isosceles triangular cavity

Linear three-dimensional modal instability of steady laminar two-dimensional states developing in a lid-driven cavity of isosceles triangular cross-section is investigated theoretically and experimentally for the case in which the equal sides form a rectangular corner. An asymmetric steady two-dimensional motion is driven by the steady motion of one of the equal sides. If the side moves away from the rectangular corner, a stationary three-dimensional instability is found. If the motion is directed towards the corner, the instability is oscillatory. The respective critical Reynolds numbers are identified both theoretically and experimentally. The neutral curves pertinent to the two configurations and the properties of the respective leading eigenmodes are documented and analogies to instabilities in rectangular lid-driven cavities are discussed

The individual and the social order in Mill and Hegel : seeking common principles in liberal and communitarian ancestry

This thesis seeks to establish a significant commonality and compatibility between the principles underpinning the political and social philosophies of GWF Hegel and John Stuart Mill. The role of the individual and the social order in both their theories is discussed and assessed separately and in turn in reference to their respective seminal works on the proper structure, principles and function of modern political infrastructure. Through an interpretation of the fundamental tenets and goals of their theories of the social order I argue for a coherent modern reconstruction of their doctrines, within which I locate parallels and contrasts as they apply. Both theorists as ultimately put forward similar arguments for freedom as an intersubjectively·developed capacity, the ideal social order as rational framework for the management of ethical and political engagement, linked to a social holism that ties individual and social progress inextricably. A respect for individual particularity of perspective and practice is integral both of their social frameworks, but that such a space must be harmonised within a rational political community worthy of individual obligation. Finally their social and political theories can be understood as complementary, each providing insights which the other lacks. Mill suffers from an insufficient regard for the social basis of identity and interconnected nature of the modern institutional framework, while Hegel displays an insufficient regard for Mill's caveats concerning the repressive potential of institutional structures and the dangers of overly empowered bureaucracies. In conclusion key elements of the two theorists' projects stand as separate but not in any way fundamentally opposed to each other. This points to the possibility of a via media between a politics of individualism and a politics of community, suggesting strong potential for reconciliation between liberal and communitarian perspectives

A new approach to wind energy: Opportunities and challenges

Despite common characterizations of modern wind energy technology as mature, there remains a persistent disconnect between the vast global wind energy resource—which is 20 times greater than total global power consumption—and the limited penetration of existing wind energy technologies as a means for electricity generation worldwide. We describe an approach to wind energy harvesting that has the potential to resolve this disconnect by geographically distributing wind power generators in a manner that more closely mirrors the physical resource itself. To this end, technology development is focused on large arrays of small wind turbines that can harvest wind energy at low altitudes by using new concepts of biology-inspired engineering. This approach dramatically extends the reach of wind energy, as smaller wind turbines can be installed in many places that larger systems cannot, especially in built environments. Moreover, they have lower visual, acoustic, and radar signatures, and they may pose significantly less risk to birds and bats. These features can be leveraged to attain cultural acceptance and rapid adoption of this new technology, thereby enabling significantly faster achievement of state and national renewable energy targets than with existing technology alone. Favorable economics stem from an orders-of-magnitude reduction in the number of components in a new generation of simple, mass-manufacturable (even 3D-printable), vertical-axis wind turbines. However, this vision can only be achieved by overcoming significant scientific challenges that have limited progress over the past three decades. The following essay summarizes our approach as well as the opportunities and challenges associated with it, with the aim of motivating a concerted effort in basic and applied research in this area

Mixing Efficiency in the Presence of Stratification: When Is It Constant?

The efficiency of the conversion of mechanical to potential energy, often expressed as the flux Richardson number, Rif, is an important determinant of vertical mixing in the ocean. To examine the dependence of Rif on the buoyancy Reynolds number, ReB, we analyze three sets of data: microstructure profiler data for which mixing is inferred from rates of dissipation of turbulent kinetic energy (ε) and temperature variance (χ) measured in the open ocean, time series of spectrally fit values of ε and covariance-derived buoyancy fluxes measured in nearshore internal waves, and time series of spectrally fit values of ε and χ measured in an energetic estuarine flow. While profiler data are well represented by Rif ≈ 0.2 for 1 < ReB < 1,000, the covariance data have much larger values of ReB and, consistent with direct numerical simulation results, show that Rif ~ ReB −0.5. The estuarine data have values of ReB that fall between those of the other two data sets but also shows Rif ≈ 0.2 for ReB < 5000. Overall, these data suggest that Rif is in general not constant and may be substantially less than 0.2 when ReB is large, although the value at which the transition from constant to ReB-dependent mixing may depend on additional parameters that are yet to be determined. Nonetheless, for much of the ocean, ReB < 100 and so Rif is constant there