A taxonomy of maximally elastic buffers

In most producer-consumer (sender-receiver) systems buffers are used for traffic smoothing. To perform that task optimally it is required that these buffers can maintain a high throughput for a wide range of occu-pancies, a property called elasticity. The maximal elasticity obtainable is a function of two design parameters of the buffer, viz. its storage ca-pacity and its average i/o-distance. Whether maximal elasticity is indeed obtained by a particular buffer design depends, however, on the detailed structure of the buffer. In this paper we investigate for which parameters optimally elastic buffers exist and what the structural complexity of those buffers is. To address the latter issue we adopt a compositional approach in which buffers are constructed according to prescribed rules from fixed sets of basic building blocks. By variation of the construction methods and the base sets a taxonomy of buffer classes is obtained that guides the search for maximally elastic buffers of a certain complexity.

Resource-aware life cycle models for service-oriented applications managed by a component framework

In this report we present a series of formal models that describe dynamically reconfigurable applications at various stages of their life cycle. It is our intention that these models capture the essential concepts of such applications and the platforms on which they are deployed, and that they indicate the essential activities required to accomplish an application’s transition from one stage of its life cycle to the next. These models aim to support a life cycle in which applications are designed as a combination of services and realized by predefined components that are deployed in a framework specially tailored to the resource management needs of these applications

Dynamically reconfigurable resource-aware component framework: architecture and concepts

Applications executed on a shared distributed platform compete for resources provided by the platform. In case these applications have highly fluctuating resource demands, a software architecture is required that provides support for runtime resource management. In position paper [1], we have proposed such architecture and have introduced its key concepts and entities. In this paper, we introduce a metamodel that captures the key concepts and we identify lifecycle models for both applications and individual components. A set of dynamic reconfiguration strategies is introduced and their relationship to the stages of the application lifecycle is given. Keywords: Component framework – networked services – resource management – dynamic reconfiguration – application lifecycle – component lifecycl

A rotating three component perfect fluid source and its junction with empty space-time

The Kerr solution for empty space-time is presented in an ellipsoidally symmetric coordinate system and it is used to produce generalised ellipsoidal metrics appropriate for the generation of rotating interior solutions of Einstein's equations. It is shown that these solutions are the familiar static perfect fluid cases commonly derived in curvature coordinates but now endowed with rotation. The resulting solutions are also discussed in the context of T-solutions of Einstein's equations and the vacuum T-solution outside a rotating source is presented. The interior source for these solutions is shown not to be a perfect fluid but rather an anisotropic three component perfect fluid for which the energy momentum tensor is derived. The Schwarzschild interior solution is given as an example of the approach.Comment: 14 page

A Predictive Model of Postnatal Surgical Intervention in Children With Prenatally Detected Congenital Anomalies of the Kidney and Urinary Tract

The aim of this study was to identify predictive factors and develop a model to assess individualized risk of postnatal surgical intervention in patients with antenatal hydronephrosis. This is a retrospective cohort study of 694 infants with prenatally detected congenital anomalies of kidney and urinary tract with a median follow-up time of 37 months. The main event of interest was postnatal surgical intervention. A predictive model was developed using Cox model with internal validation by bootstrap technique. Of 694 patients, 164 (24%) infants underwent surgical intervention in a median age of 7.8 months. Predictors of the surgical intervention in the model were: baseline glomerular filtration rate, associated hydronephrosis, presence of renal damage and the severity of renal pelvic dilatation. The optimism corrected c statistic for the model was 0.84 (95%CI, 0.82–0.87). The predictive model may contribute to identify infants at high risk for surgical intervention. Further studies are necessary to validate the model in patients from other settings