9,315 research outputs found
Connectionism Reconsidered: Minds, Machines and Models
In this paper the issue of drawing inferences about biological cognitive systems on the basis of connectionist simulations is addressed. In particular, the justification of inferences based on connectionist models trained using the backpropagation learning algorithm is examined. First it is noted that a justification commonly found in the philosophical literature is inapplicable. Then some general issues are raised about the relationships between models and biological systems. A way of conceiving the role of hidden units in connectionist networks is then introduced. This, in combination with an assumption about the way evolution goes about solving problems, is then used to suggest a means of justifying inferences about biological systems based on connectionist research
Measures of Economic Status - Combining Income and Wealth into a Single Measure of the Potential Command Over Goods and Services
The purpose of this paper is to stimulate discussion on the way that economists, statisticians and analysts treat the wealth of agricultural households and changes in that wealth not arising from production. The concept of "economic status" is revisited and the implications of using it when making comparisons of agricultural households with other groups in society is reviewed. A more explicit treatment of capital and wealth is proposed.Consumer/Household Economics,
Policy Requirements in the EU and the Existing Array of Indicators Problem Definition, Policy Performance and the Implications of Reform
Policies involving agriculture require information about production of commodities and about the firms that produce them. Understanding the behaviour of the family-firm is central to many issues and increasingly relevant as objectives evolve and the pluriactive nature of farm households is recognised. Policy reform is likely to concentrate interest on the welfare of the agricultural household and the various sources of income that accrue to it. However, statistics that have the household-firm at their centre are poorly developed compared with those on agricultural activity. Reasons are explored and opportunities identified to correct this imbalance.Agricultural and Food Policy,
Rural Development Policies and Agricultural Adjustment
Agricultural and Food Policy, Community/Rural/Urban Development,
Impact of the commercial fishery on the population of bait shrimp (Penaeus spp.) in Biscayne Bay, 1986
Monthly population size of bait shrimp in the Bay was estimated from December 1984 to July 1985. Growth rates for male and female P. duorarum showed that pink shrimp
exhibit a mean residence time in the nursery area (Biscayne Bay) of approximately 21 weeks. Monthly mortality rates were determined for each sex of pink shrimp. It was
estimated that 23% and 26% of the male and female monthly population size, respectively, was absorbed by both the fishery and ecosystem monthly. Monthly proportion of the standing stock expected to die exclusively through fishing was 6.5% and 6.0% for males and females respectively. Estimates of emigration rates showed that approximately 4.0% of the population was lost from the Bay system each month. This surplus production was about 50% of the average monthly catch by the fleet. Fishing mortality represents only 8 - 9% of the losses to the shrimp population. The
biggest source of loss is emigration, suggesting that most shrimp beyond the size at recruitment (to the fishery) are not utilized for food while in the Bay. Thus, it appears
that the direct impact of the fishery on the bait shrimp population is relatively small. (PDF contains 46 pages
Performance of the CDF Calorimeter Simulation in Tevatron Run II
The CDF experiment is successfully collecting data from ppbar collisions at
the Tevatron in Run II. As the data samples are getting larger, systematic
uncertainties due to the measurement of the jet energy scale assessed using the
calorimeter simulation have become increasingly important. In many years of
operation, the collaboration has gained experience with GFLASH, a fast
parametrization of electromagnetic and hadronic showers used for the
calorimeter simulation. We present the performance of the calorimeter
simulation and report on recent improvements based on a refined in situ tuning
technique. The central calorimeter response is reproduced with a precision of
1-2%.Comment: 8 pages, 4 figures; LaTeX2e, 10 .eps files, uses aipproc.cls,
aipxfm.sty and aip-6s.clo (included). Contribution to the Proceedings of the
12th International Conference on Calorimetry in High Energy Physics
(CALOR06), June 5-9, 2006, Chicago (IL), USA. To be published by American
Institute of Physics (AIP
Enumeration of the Fungi of Ceylon : part II., containing the remainder of the Hymenomycetes, with the remaining established tribes of Fungi
The distribution of pairwise peculiar velocities in the nonlinear regime
The distribution of pairwise, relative peculiar velocities, , on
small nonlinear scales, , is derived from the Press--Schechter approach.
This derivation assumes that Press--Schechter clumps are virialized and
isothermal. The virialized assumption requires that the circular velocity, , where denotes the mass of the clump. The isothermal
assumption means that the circular velocity is independent of radius. Further,
it is assumed that the velocity distribution within a clump is Maxwellian, that
the pairwise relative velocity distribution is isotropic, and that on nonlinear
scales clump-clump motions are unimportant when calculating the distribution of
velocity differences. Comparison with -body simulations shows that, on small
nonlinear scales, all these assumptions are accurate. For most power spectra of
interest, the resulting line of sight, pairwise, relative velocity
distribution, , is well approximated by an exponential, rather
than a Gaussian distribution. This simple Press--Schechter model is also able
to provide a natural explanation for the observed, non-Maxwellian shape of
, the distribution of peculiar velocities.Comment: (MNRAS, in press) 16 pages, uuencode
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