The (In)Difference engine: explaining the disappearance of diversity in the design of the personal computer

At the time of writing there is a clear perception of all office computers as being more or less identical. Discussion with users entails repetitive rhetoric as they describe a landscape of boring beige boxes. The office PC is indeed a ‘clone’ - an identical, characterless copy of a bland original. Through the exploration of an archive of computer manufacturer’s catalogues, this article shows how previous, innovative forms of the computer informed by cultural references as diverse as science fiction, accepted gender roles and the discourse of status as displayed through objects, have been systematically replaced by the adoption of a ‘universal’ design informed only by the nondescript, self-referential world of office equipment. The acceptance of this lack of innovation in the design of such a truly global, mass-produced, multi-purpose technological artefact has had an enormous effect on the conception, perception and consumption of the computer, and possibly of information technology itself. The very anonymity of the PC has created an attitude of indifference at odds with its potential.</p

The brittleness index in hydraulic fracturing

We present a new definition of a brittleness index which is used as a criterion for candidate selection of rock intervals for hydraulic fracturing. The new index is a combination of material strength parameters and insitu stresses. It was derived from an analytical model of hydraulic fracturing in weak formations of varying ductility. The model is based on Mohr-Coulomb dislocations that are placed in the effective centres of the complete slip process that is distributed around the crack tip. The new brittleness index varies between 0 and 1 with the one limit to correspond to brittle propagation and the other limit to a fracture that requires infinite energy release per unit advance. The values between 0 and 1 correspond to fracture propagation of increasing ductility from brittle to small scale and finally to large scale yielding. The results are particularly interesting for predicting the propagation of axial fractures in the horizontal direction and their confinement in the vertical direction

A case study of MMO2's Madic: A framework for creating mobile internet systems

Mobile Internet applications on ubiquitous mobile networks allows real-time, anywhere, anytime connectivity to services. Due to its scalability and potential cost savings, mobile communication is being increasingly applied in the business and consumer communities to create innovative data and voice application, which run over the Internet infrastructure. This paper reports on a case study at an organisation that created an innovative approach to developing mobile applications developed by third party independent developers. A conceptual wireless reference model is presented that was used to define the various system components required to create effective mobile applications

Quantum interference in nested d-wave superconductors: a real-space perspective

We study the local density of states around potential scatterers in d-wave superconductors, and show that quantum interference between impurity states is not negligible for experimentally relevant impurity concentrations. The two impurity model is used as a paradigm to understand these effects analytically and in interpreting numerical solutions of the Bogoliubov-de Gennes equations on fully disordered systems. We focus primarily on the globally particle-hole symmetric model which has been the subject of considerable controversy, and give evidence that a zero-energy delta function exists in the DOS. The anomalous spectral weight at zero energy is seen to arise from resonant impurity states belonging to a particular sublattice, exactly as in the 2-impurity version of this model. We discuss the implications of these findings for realistic models of the cuprates.Comment: 12 pages, 10 figs, submitted to Phys. Rev.

Superfluid Suppression in d-Wave Superconductors due to Disordered Magnetism

The influence of static magnetic correlations on the temperature-dependent superfluid density \rho_s(T) is calculated for d-wave superconductors. In self-consistent calculations, itinerant holes form incommensurate spin density waves (SDW) which coexist with superconductivity. In the clean limit, the density of states is gapped, and \rho_s(T << T_c) is exponentially activated. In inhomogeneously-doped cases, the SDW are disordered and both the density of states and \rho_s(T) obtain forms indistinguishable from those in dirty but pure d-wave superconductors, in accordance with experiments. We conclude that the observed collapse of \rho_s at x\approx 0.35 in underdoped YBCO may plausibly be attributed to the coexistence of SDW and superconductivity.Comment: 6 pages, 5 figures. Expanded discussio