Two cheers for the urban white paper

In November 2000, the government finally published its Urban White Paper. Our Towns and Cities: The Future appeared over a year after the Rogers’ Urban Task Force report, to which it provided an indirect official response, and no less than 23 years after the last such statement of government urban policy

Evaluating two methods for Treebank grammar compaction

Treebanks, such as the Penn Treebank, provide a basis for the automatic creation of broad coverage grammars. In the simplest case, rules can simply be ‘read off’ the parse-annotations of the corpus, producing either a simple or probabilistic context-free grammar. Such grammars, however, can be very large, presenting problems for the subsequent computational costs of parsing under the grammar. In this paper, we explore ways by which a treebank grammar can be reduced in size or ‘compacted’, which involve the use of two kinds of technique: (i) thresholding of rules by their number of occurrences; and (ii) a method of rule-parsing, which has both probabilistic and non-probabilistic variants. Our results show that by a combined use of these two techniques, a probabilistic context-free grammar can be reduced in size by 62% without any loss in parsing performance, and by 71% to give a gain in recall, but some loss in precision

The crash involvement of interstate drivers in Queensland

Previous research has suggested that driving interstate is more hazardous than driving in one’s home state. However, the increased risk does not appear to be due to greater risk-taking by these drivers, but due to the greater distances they travel, particularly on rural roads, and associated problems such as fatigue. To further examine this issue, an analysis was undertaken of all reported crashes involving interstate drivers that occurred in Queensland between 1993 and 1998. During this period, interstate drivers represented 5% of all drivers involved in fatal and serious injury crashes in Queensland. The analysis indicated that the crashes involving interstate drivers were no more likely to involve factors such as alcohol, speeding, inattention/negligence or inexperience. Rather, the crash involvement patterns of interstate drivers appear to relate more to the type and location of their driving. For example, in Queensland interstate drivers are over-represented in crashes involving: open road driving; driver fatigue; the overturning and sideswiping of vehicles; and weekend travel. Interstate drivers were also more likely to be considered at fault for the crashes they were involved in, compared with local drivers

Mass flow through solid 4He induced by the fountain effect

Using an apparatus that allows superfluid liquid 4He to be in contact with hcp solid \4he at pressures greater than the bulk melting pressure of the solid, we have performed experiments that show evidence for 4He mass flux through the solid and the likely presence of superfluid inside the solid. We present results that show that a thermomechanical equilibrium in quantitative agreement with the fountain effect exists between two liquid reservoirs connected to each other through two superfluid-filled Vycor rods in series with a chamber filled with solid 4He. We use the thermomechanical effect to induce flow through the solid and measure the flow rate. On cooling, mass flux appears near T = 600 mK and rises smoothly as the temperature is lowered. Near T = 75 mK a sharp drop in the flux is present. The flux increases as the temperature is reduced below 75 mK. We comment on possible causes of this flux minimum.Comment: 20 pages, 22 figures, 7 table

The overlap parameter across an inverse first order phase transition in a 3D spin-glass

We investigate the thermodynamic phase transition taking place in the Blume-Capel model in presence of quenched disorder in three dimensions (3D). In particular, performing Exchange Montecarlo simulations, we study the behavior of the order parameters accross the first order phase transition and its related coexistence region. This transition is an Inverse Freezing.Comment: 9 pages, 6 figures, Contribution to the XII International Workshop on Complex System

A Degenerate Bose-Fermi Mixture of Metastable Atoms

We report the observation of simultaneous quantum degeneracy in a dilute gaseous Bose-Fermi mixture of metastable atoms. Sympathetic cooling of helium-3 (fermion) by helium-4 (boson), both in the lowest triplet state, allows us to produce ensembles containing more than 10^6 atoms of each isotope at temperatures below 1 micro-Kelvin, and achieve a fermionic degeneracy parameter of T/Tf=0.45. Due to their high internal energy, the detection of individual metastable atoms with sub-nanosecond time resolution is possible, permitting the study of bosonic and fermionic quantum gases with unprecedented precision. This may lead to metastable helium becoming the mainstay of quantum atom optics.Comment: 4 pages, 3 figures submitted to PR

Focusing of Intense Subpicosecond Laser Pulses in Wedge Targets

Two dimensional particle-in-cell simulations characterizing the interaction of ultraintense short pulse lasers in the range 10^{18} \leq I \leq 10^{20} W/cm^{2} with converging target geometries are presented. Seeking to examine intensity amplification in high-power laser systems, where focal spots are typically non-diffraction limited, we describe key dynamical features as the injected laser intensity and convergence angle of the target are systematically varied. We find that laser pulses are focused down to a wavelength with the peak intensity amplified by an order of magnitude beyond its vacuum value, and develop a simple model for how the peak location moves back towards the injection plane over time. This performance is sustained over hundreds of femtoseconds and scales to laser intensities beyond 10^{20} W/cm^{2} at 1 \mu m wavelength.Comment: 5 pages, 6 figures, accepted for publication in Physics of Plasma

Tales at the Outspan, or Adventures in the Wild Regions of Southern Africa

https://commons.und.edu/settler-literature/1191/thumbnail.jp

Knowledge Representation with Ontologies: The Present and Future

Recently, we have seen an explosion of interest in ontologies as artifacts to represent human knowledge and as critical components in knowledge management, the semantic Web, business-to-business applications, and several other application areas. Various research communities commonly assume that ontologies are the appropriate modeling structure for representing knowledge. However, little discussion has occurred regarding the actual range of knowledge an ontology can successfully represent