Data-driven discovery of coordinates and governing equations

The discovery of governing equations from scientific data has the potential to transform data-rich fields that lack well-characterized quantitative descriptions. Advances in sparse regression are currently enabling the tractable identification of both the structure and parameters of a nonlinear dynamical system from data. The resulting models have the fewest terms necessary to describe the dynamics, balancing model complexity with descriptive ability, and thus promoting interpretability and generalizability. This provides an algorithmic approach to Occam's razor for model discovery. However, this approach fundamentally relies on an effective coordinate system in which the dynamics have a simple representation. In this work, we design a custom autoencoder to discover a coordinate transformation into a reduced space where the dynamics may be sparsely represented. Thus, we simultaneously learn the governing equations and the associated coordinate system. We demonstrate this approach on several example high-dimensional dynamical systems with low-dimensional behavior. The resulting modeling framework combines the strengths of deep neural networks for flexible representation and sparse identification of nonlinear dynamics (SINDy) for parsimonious models. It is the first method of its kind to place the discovery of coordinates and models on an equal footing.Comment: 25 pages, 6 figures; added acknowledgment

The Monge problem in Wiener Space

We address the Monge problem in the abstract Wiener space and we give an existence result provided both marginal measures are absolutely continuous with respect to the infinite dimensional Gaussian measure {\gamma}

An holistic approach to understanding the changing nature of organisational structure

Purpose: The purpose of this paper is to report on an exploratory study to revisit and critically reappraise the impact of IT upon organisational structure, by exploring how the deployment of ERP, when accompanied by a specific strategic orientation, impacted upon the host organisation's structural design. Design/methodology/approach: The study was initially enacted through a postal questionnaire survey of IT managers within a sample of China's largest manufacturing organisations. Follow‐up interviews were then conducted with senior managers, who had first‐hand experience of working on ERP implementations, to help to more fully understand the impact of ERP upon organisational structure. Findings: The study found that the implementation of ERP technology and the strategic orientation of the host organisation are both likely to modify the structural design of Chinese manufacturing organisations. Moreover, it has been found that the success of an ERP deployment is a stronger predictor of organisational form than the scale of the deployment. The results of the study would also suggest that ERP is more likely to affect structural changes, when deployed in the presence of a complementary “prospector” corporate strategy. Practical implications: The study provides clear new evidence that ERP is likely to have a significant impact upon organisational structure, but, because of the complexity of the technology and the uniqueness of every organisational context, the authors offer no simple prescriptions or panaceas as to how it should be managed. However, managers should be aware that an ERP implementation will almost certainly affect organisational structure, and then take steps to ensure that such changes are carefully and proactively managed. Originality/value: There is already a rich and established literature with regard to the impact of IT upon organisational structure. However, it could be argued that by focussing upon ERP, by explicitly modelling the effect of strategy and by taking a holistic view of organisational structure, the paper is able to offer a far more subtle view of the complexities of the relationship between IT and organisational structure than prior studies

Windé Koroji Ouest (Mali, Second and Third Millennia BCE): The Environmental and Subsistence Evidence

Windé Koroji Ouest is an early agro-pastoral site situated at the eastern periphery of the Inland Niger Delta of Mali, north of the Gandamia and Bandiagara escarpments. This chapter is the first publication of all subsistence and environmental information available concerning this site which was excavated by the senior author in 1992/1993. The presence of domestic millet ca. 2100-1900 BCE is confirmed, as well as sheep during this same period, with cattle attested subsequently (post 1600 BCE). The role of the environment and potential environmental change in the economy of this site is reviewed. It is argued that Windé Koroji Ouest existed within wider, seasonally mobile settlement networks exhibiting a range of flexible subsistence adaptations

Infection urinaire à Haemophilus influenzae chez 3 enfants ayant une malformation de l’arbre urinaire

La pyélonéphrite aigue (PNA) est une des infections les plus fréquentes de l’enfant, dans laquelle le genre Haemophilus est très rarement impliqué. De janvier 2010 à octobre 2011, seulement 3 enfants âgés de moins de 15 ans ont été hospitalisés dans notre établissement pour une infection urinaire à Haemophilus influenzae. Les 3 enfants présentaient des tableaux typiques de PNA : fièvre, signes fonctionnels urinaires ou douleurs abdominales. L’examen cytobactériologique des urines (ECBU) montrait à l’examen direct une leucocyturie significative et de nombreux bacilles Gram négatifs. La culture bactériologique standard des urines des 3 patients était négative. H. influenzae a été mis en évidence secondairement après réensemencement des urines sur milieu enrichi. Les 3 enfants présentaient une uropathie : 2 syndromes de la jonction pyélo-urétérale droit et une duplicité urétérale bilatérale avec reflux de haut grade. Pendant la période étudiée, la prévalence des PNA à Haemophilus dans notre établissement a été de 0,02 % dans les infections urinaires de l’enfant. Dans la littérature, les PNA à Haemophilus sont rares (moins de 1 % chez l’enfant), fréquemment associées à une malformation de l’arbre urinaire et difficiles à mettre en évidence. Lorsque l’ECBU montre des bacilles Gram négatifs à l’examen direct non retrouvés à la culture, il faut réensemencer les urines sur gélose au sang cuit, notamment si le patient est porteur d’une uropathie

Asymptotic Iteration method for singular potentials

The asymptotic iteration method (AIM) is applied to obtain highly accurate eigenvalues of the radial Schroedinger equation with the singular potential V(r)=r^2+\lambda/r^\alpha (\alpha,\lambda> 0) in arbitrary dimensions. Certain fundamental conditions for the application of AIM, such as a suitable asymptotic form for the wave function, and the termination condition for the iteration process, are discussed. Several suggestions are introduced to improve the rate of convergence and to stabilize the computation. AIM offers a simple, accurate, and efficient method for the treatment of singular potentials such as V(r) valid for all ranges of coupling \lambda.Comment: 9 page

Migration and longer distance commuting in rural England

This paper examines whether recent in-migrants to rural settlements in England commute further to work than the longer-term residents of these places and whether commuting distance differs according to the type of move and the geographical context of their home. The study is based on data from the Controlled Access Microdata Sample (CAMS) of the 2001 Census of Population. It is found that recent in-migrants are much more likely to commute at least 20km than are the longer-term residents. Using binary logistic regression so as to allow for socio-demographic differences between people, it is shown that the likelihood of longer distance commuting was highest for people who had moved home by between 15 and 99km and for people moving from the largest cities

Measuring Productivity: Issues Arising From Outsourcing And Merger Activities

The paper discusses productivity measurement issues as companies engage in outsourcing and merger activities, and links productivity measures to competitiveness. Need for new productivity approaches is presented