29,057 research outputs found
Isostaticity in two dimensional pile of rigid disks
We study the static structure of piles made of polydisperse disks in the
rigid limit with and without friction using molecular dynamic simulations for
various elasticities of the disks and pile preparation procedures. The
coordination numbers are calculated to examine the isostaticity of the pile
structure. For the frictionless pile, it is demonstrated that the coordination
number converges to 4 in the rigid limit, which implies that the structure of
rigid disk pile is isostatic. On the other hand, for the frictional case with
the infinite friction constant, the coordination number depends on the
preparation procedure of the pile, but we find that the structure becomes very
close to isostatic with the coordination number close to 3 in the rigid limit
when the pile is formed through the process that tends to make a pile of random
configuration.Comment: 3 pages, 3 figures, Submitted to J. Phys. Soc. Jp
Solar irradiance models and measurements: a comparison in the 220 nm to 240 nm wavelength band
Solar irradiance models that assume solar irradiance variations to be due to
changes in the solar surface magnetic flux have been successfully used to
reconstruct total solar irradiance on rotational as well as cyclical and
secular time scales. Modelling spectral solar irradiance is not yet as
advanced, and also suffers from a lack of comparison data, in particular on
solar-cycle time scales. Here we compare solar irradiance in the 220 nm to 240
nm band as modelled with SATIRE-S and measured by different instruments on the
UARS and SORCE satellites.
We find good agreement between the model and measurements on rotational time
scales. The long-term trends, however, show significant differences. Both SORCE
instruments, in particular, show a much steeper gradient over the decaying part
of cycle 23 than the modelled irradiance or that measured by UARS/SUSIM.Comment: 8 pages, 2 figures, conference proceedings to appear in Surveys in
Geophysic
The design and development of transonic multistage compressors
The development of the transonic multistage compressor is reviewed. Changing trends in design and performance parameters are noted. These changes are related to advances in compressor aerodynamics, computational fluid mechanics and other enabling technologies. The parameters normally given to the designer and those that need to be established during the design process are identified. Criteria and procedures used in the selection of these parameters are presented. The selection of tip speed, aerodynamic loading, flowpath geometry, incidence and deviation angles, blade/vane geometry, blade/vane solidity, stage reaction, aerodynamic blockage, inlet flow per unit annulus area, stage/overall velocity ratio, and aerodynamic losses are considered. Trends in these parameters both spanwise and axially through the machine are highlighted. The effects of flow mixing and methods for accounting for the mixing in the design process are discussed
Internal Stress in a Model Elasto-Plastic Fluid
Plastic materials can carry memory of past mechanical treatment in the form
of internal stress. We introduce a natural definition of the vorticity of
internal stress in a simple two-dimensional model of elasto-plastic fluids,
which generates the internal stress. We demonstrate how the internal stress is
induced under external loading, and how the presence of the internal stress
modifies the plastic behavior.Comment: 4 pages, 3 figure
The social geography of childcare: 'making up' the middle class child
Childcare is a condensate of disparate social forces and social processes. It is gendered and classed. It is subject to an excess of policy and political discourse. It is increasingly a focus for commercial exploitation. This is a paper reporting on work in progress in an ESRC funded research project (R000239232) on the choice and provision of pre-school childcare by middle class (service class) families in two contrasting London locations. Drawing on recent work in class analysis the paper examines the relationships between childcare choice, middle class fractions and locality. It suggests that on the evidence of the findings to date, there is some evidence of systematic differences between fractions in terms of values, perspectives and preferences for childcare, but a more powerful case for intra-class similarities, particularly when it comes to putting preferences into practice in the 'making up of a middle class child' through care and education
Heat capacity mapping mission project HCM-051
There are no author-identified significant results in this report
A simple solution of sound transmission through an elastic wall to a rectangular enclosure, including wall damping and air viscosity effects
A simple solution to the problem of the acoustical coupling between a rectangular structure, its air content, and an external noise source is presented. This solution is a mathematical expression for the normalized acoustic pressure inside the structure. Numerical results for the sound-pressure response for a specified set of parameters are also presented
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