5,151 research outputs found
Virtual Consumption, Sustainability & Human Well-Being
There is widespread consensus that present patterns of consumption could lead to the permanent impossibility of maintaining those patterns and, perhaps, the existence of the human race. While many patterns of consumption qualify as ‘sustainable’ there is one in particular that deserves greater attention: virtual consumption. We argue that virtual consumption — the experience of authentic consumptive experiences replicated by alternative means — has the potential to reduce the deleterious consequences of real consumption by redirecting some consumptive behavior from shifting material states to shifting information states
Design, Fabrication and Test of Multi-Fiber Laminates
Unidirectional and angleply multifiber laminates were tested for improved impact strength and other mechanical properties. The effects of several variables on the mechanical properties of epoxy matrix materials were described. These include fiber type (HMS and AS graphites, glass, and Kevlar 49), ratio of primary to hybridizing fiber and hybrid configuration. It is demonstrated that AS graphite/S glass in an intraply configuration results in the best combination of static and Charpy impact properties as well as superior ballistic impact resistance. Pendulum impact tests which were conducted on thin specimens are shown to produce different ranking of materials than tests conducted on standard thickness Charpy specimens. It is shown that the thin specimen results are in better agreement with the ballistic impact data. Additional static test data are reported as a function of temperature for the seven best hybrid configurations having epoxy, polyimide (PMR-15) and polyphenylquinoxaline resins as the matrix
Experimental verification of the non-equilibrium model for predicting behavior in the char zone of a charring ablator Status report
Experimental simulation to establish accuracy of nonequilibrium flow model with system simulating charring during ablatio
Solution of the Frozen Flow Momentum Equation Status Report
Momentum equation solved for frozen flow in char zone of charring ablato
Hysteresis loops of Co-Pt perpendicular magnetic multilayers
We develop a phenomenological model to study magnetic hysteresis in two
samples designed as possible perpendicular recording media. A stochastic
cellular automata model captures cooperative behavior in the nucleation of
magnetic domains. We show how this simple model turns broad hysteresis loops
into loops with sharp drops like those observed in these samples, and explains
their unusual features. We also present, and experimentally verify, predictions
of this model, and suggest how insights from this model may apply more
generally.Comment: 4.5 pages, 5 figure
Comparison of Methods for Determining the Composition of Pyrolysis Products from the Degradation of Ablative Composites. Status report.
Determining composition of pyrolysis products from degradation of ablative material
Reversal-field memory in magnetic hysteresis
We report results demonstrating a singularity in the hysteresis of magnetic
materials, the reversal-field memory effect. This effect creates a
nonanalyticity in the magnetization curves at a particular point related to the
history of the sample. The microscopic origin of the effect is associated with
a local spin-reversal symmetry of the underlying Hamiltonian. We show that the
presence or absence of reversal-field memory distinguishes two widely studied
models of spin glasses (random magnets).Comment: 3 pages, 5 figures. Proceedings of "2002 MMM Conferece", Tampa, F
Further studies of space-time clustering of Burkitt's lymphoma in Uganda.
All hospital-treated cases of Burkitt's lymphoma (BL), with onset of symptoms in the period 1963-68 and resident in the Lango and Acholi districts of Uganda, were identified. The average annual incidence of BL in the 6-year period was 1-87 X 10(-5), similar to that in the adjacent West Nile district. Contrary to findings in other areas of Uganda, there was no evidence of seasonal variation in the onset of cases, nor of space-time clustering, nor of a decline in the incidence of BL in the study period. An inverse relationship was noted between the median age at onset of BL and the incidence of the disease in different areas of Uganda, a finding consistent with intense malarial infection being a precipitating factor for BL. The variable observations with respect to space-time clustering of BL and seasonal variation in incidence in different areas remains unexplained, but it is suggested that a closer study of the patterns of malarial infection in these areas may help to account for the findings
Playing with nonuniform grids
Numerical experiments with discretization methods on nonuniform grids are presented for the convection-diffusion equation. These show that the accuracy of the discrete solution is not very well predicted by the local truncation error. The diagonal entries in the discrete coefficient matrix give a better clue: the convective term should not reduce the diagonal. Also, iterative solution of the discrete set of equations is discussed. The same criterion appears to be favourable.
Reversal-Field Memory in the Hysteresis of Spin Glasses
We report a novel singularity in the hysteresis of spin glasses, the
reversal-field memory effect, which creates a non-analyticity in the
magnetization curves at a particular point related to the history of the
sample. The origin of the effect is due to the existence of a macroscopic
number of "symmetric clusters" of spins associated with a local spin-reversal
symmetry of the Hamiltonian. We use First Order Reversal Curve (FORC) diagrams
to characterize the effect and compare to experimental results on thin magnetic
films. We contrast our results on spin glasses to random magnets and show that
the FORC technique is an effective "magnetic fingerprinting" tool.Comment: 4 pages, 6 figure
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