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 Parametric Framework for the Comparison of Methods of Very Robust Regression

There are several methods for obtaining very robust estimates of regression parameters that asymptotically resist 50% of outliers in the data. Differences in the behaviour of these algorithms depend on the distance between the regression data and the outliers. We introduce a parameter $\lambda$ that defines a parametric path in the space of models and enables us to study, in a systematic way, the properties of estimators as the groups of data move from being far apart to close together. We examine, as a function of $\lambda$, the variance and squared bias of five estimators and we also consider their power when used in the detection of outliers. This systematic approach provides tools for gaining knowledge and better understanding of the properties of robust estimators.Comment: Published in at http://dx.doi.org/10.1214/13-STS437 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Weighing Aims in Doxastic Deliberation

In this paper, I defend teleological theories of belief against the exclusivity objection. I argue that despite the exclusive influence of truth in doxastic deliberation, multiple epistemic aims interact when we consider what to believe. This is apparent when we focus on the processes involved in specific instances (or concrete cases) of doxastic deliberation, such that the propositions under consideration are specified. First, I out- line a general schema for weighing aims. Second, I discuss recent attempts to defend the teleological position in relation to this schema. And third, I develop and defend my proposal that multiple epistemic aims interact in doxastic deliberation—a possibility which, as of yet, has received no serious attention in the literature

Some speculations on storage and retrieval processes in long term memory

Speculations on storage and retrieval processes in long term memor

Machines and machinations: The integrated care record service in the UK national health service

This paper examines the use of Actor Network Theory (ANT) as a lens to get a better understanding of the implementation of the Integrated Care Record Service (ICRS) in the UK National Health Service (NHS). Actor Network Theory has been deployed in various environments to achieve a better understanding of the roles of not only the humans but also the artifacts that constitute, in this case, healthcare networks of services and organisations. The theory is used as a means of supporting real world interventions, providing a richer understanding of complexities involved and thereby helps management to make better decisions. This study also explores Latour’s concept of machines as machinations, whose role is to translate other actors into the network. We propose ICRS as a fruitful empirical context for the use of ANT to support decision making for actors in health care provision. Actor Network Theory (ANT) is well-suited for use in the socio-technical evaluation of IS into the ICRS project because this approach treats human and non-human actors symmetrically. This approach facilitates a more thorough examination of the ways in which information technology is enabled or restricted in social processes

Extension the Noether's theorem to Lagrangian formulation with nonlocality

A Lagrangian formulation with nonlocality is investigated in this paper. The nonlocality of the Lagrangian is introduced by a new nonlocal argument that is defined as a nonlocal residual satisfying the zero mean condition. The nonlocal Euler-Lagrangian equation is derived from the Hamilton's principle. The Noether's theorem is extended to this Lagrangian formulation with nonlocality. With the help of the extended Noether's theorem, the conservation laws relevant to energy, linear momentum, angular momentum and the Eshelby tensor are determined in the nonlocal elasticity associated with the mechanically based constitutive model. The results show that the conservation laws exist only in the form of the integral over the whole domain occupied by body. The localization of the conservation laws is discussed in detail. We demonstrate that not every conservation law corresponds to a local equilibrium equation. Only when the nonlocal residual of conservation current exists, can a conservation law be transformed into a local equilibrium equation by localization.Comment: 13 page

Some two-process models for memory

Two-process models for memory and learnin