There Is No Special Problem About Scientific Representation

In recent years, philosophers of science have devoted considerable attention to questions about scientific models, and particularly to the issue of how models can represent the world. We propose that scientific representation is best understood as a special case of a more general notion of representation, and that the relatively well worked-out and plausible philosophical theories of the latter are directly applicable to the scientific special case. Construing scientific representation in this way makes the so-called ``problem of scientific representation'' look much less interesting than it has seemed to many, and also suggests that some of the (hotly contested) debates in the literature are concerned with non-issues

Security Through Stochasticity - Toward Adversarial Defense using Energy-based Models

This paper serves as an investigation in the use of energy-based models for adversarial defense via purification and training. Convergent and non-convergent energy-based models are tasked to remove white-box adversarial signals embedded into images from the CIFAR-10 dataset so that they may be classified correctly. This work presents an analysis behind the stochastic behavior of MCMC sampling for adversarial noise reduction in meta-stable energy basins and the benefits and challenges associated with different regimes of energy-based learning for this task

Scaling Relationships of Gaussian Processes

Asset returns conforming to a Gaussian random walk are characterised by the temporal independence of the moments of the distribution. Employing currency returns, this note demonstrates the conditions that are necessary for risk to be estimated in this manner.Scaling; Volatility; Currency Returns

Screw pile design optimisation under tension in sand

Many applications in offshore engineering, such as floating or jacket-founded wind turbines or wave energy converters, require a significant uplift capacity of their foundations to be kept in place. Straight-shafted or suction piles in sands have a limited uplift capacity as they resist by friction only. In contrast, screw piles or screw anchors are a promising solution which provides a similar capacity to plate anchors and does not generate disturbance for marine mammals (e.g. from pile driving operations). The optimisation of the screw pile design does not rely only on the geotechnical assessment of the uplift capacity based on soil strength, but also on operational (installation requirements) and structural (helix bending, core section stress, limiting steel plate thick-ness) constraints. This paper develops a methodology for the design optimisation of screw piles under pure ten-sion in sand, incorporating all of these constraints, based on simplified analytical or semi-analytical approaches. The results show that the uplift capacity provided by an optimised screw pile is able to meet the needs of the offshore industry, across a range of soil densities and different applications (jacket foundation pile or tension leg platform anchor), providing that adequate installation plant could be dev

High Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc

We have obtained high resolution (<1") deep x-ray images of the globular cluster 47Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70 kilosec exposure of the cluster reveals a centrally concentrated population of faint (Lx ~10^{30-33} erg/s) x-ray sources, with at least 108 located within the central 2arcmin X 2.5arcmin and at least half with Lx <10^{30.5} erg/s. All 15 millisecond pulsars (MSPs) recently located precisely by radio observations are identified, though two are unresolved by Chandra. The x-ray spectral and temporal characteristics, as well as initial optical identifications with the Hubble Space Telescope, suggest that >~50% are millisecond pulsars, ~30% are accreting white dwarfs, ~15% are main sequence binaries in flare outbursts and only 2 to 3 are quiescent low mass x-ray binaries containing neutron stars, the conventional progenitors of MSPs. An approximate upper limit of ~470Msun for the mass of an accreting central black hole in the cluster is derived. These observations provide the first x-ray "color-magnitude" diagram for a globular cluster and census of its compact object and binary population.Comment: 19 pages, 7 figures, 1 table (as supplementary file). Published online in Science Express on May 17, 2001 (reference: 10.1126/science.1061135). To appear in Science (print version) in late June, 200