Fast-slow bursters in the unfolding of a high codimension singularity and the ultra-slow transitions of classes

Bursting is a phenomenon found in a variety of physical and biological systems. For example, in neuroscience, bursting is believed to play a key role in the way information is transferred in the nervous system. In this work, we propose a model that, appropriately tuned, can display several types of bursting behaviors. The model contains two subsystems acting at different timescales. For the fast subsystem we use the planar unfolding of a high codimension singularity. In its bifurcation diagram, we locate paths that underly the right sequence of bifurcations necessary for bursting. The slow subsystem steers the fast one back and forth along these paths leading to bursting behavior. The model is able to produce almost all the classes of bursting predicted for systems with a planar fast subsystems. Transitions between classes can be obtained through an ultra-slow modulation of the model's parameters. A detailed exploration of the parameter space allows predicting possible transitions. This provides a single framework to understand the coexistence of diverse bursting patterns in physical and biological systems or in models.Comment: 22 pages, 15 figure

Variations of Solar Non-axisymmetric Activity

The temporal behaviour of solar active longitudes has been examined by using two sunspot catalogues, the Greenwich Photoheliographic Results (GPR) and the Debrecen Photoheliographic Data (DPD). The time-longitude diagrams of the activity distribution reveal the preferred longitudinal zones and their migration with respect to the Carrington frame. The migration paths outline a set of patterns in which the activity zone has alternating prograde/retrograde angular velocities with respect to the Carrington rotation rate. The time profiles of these variations can be described by a set of successive parabolae. Two similar migration paths have been selected from these datasets, one northern path during cycles 21 - 22 and one southern path during cycles 13 - 14, for closer examination and comparison of their dynamical behaviours. The rates of sunspot emergence exhibited in both migration paths similar periodicities, close to 1.3 years. This behaviour may imply that the active longitude is connected to the bottom of convection zone

Approach to Identify Internal Best Practices in a Software Organization.

Current approaches to software process improvements (SPI) in software organizations is based on identifying gaps by comparing the way organizations work with respect to practices contained in the reference models. Later, these gaps will be targeted for establishing software process improvements. This paper presents an approach for identifying best practices within the organization. This is considered a key element in order to compare the way software organizations work with the reference models. After that, these practices will be complemented with practices contained in these models depending on the organization's business goals

Practical Application Of Uml Activity Diagrams For The Generation Of Test Cases

Software testing and debugging represents around one third of total effort in development projects. Different factors which have influence on poor practices of testing have been identified through specific surveys. Amongst several, one of the most important is the lack of efficient methods to exploit development models for generating test cases. This paper presents a new method for automatically generating a complete set of functional test cases from UML activity diagrams complementing specification of use cases. Test cases are prioritized according to software risk information. Results from experiences with more than 70 software professionals/experts validate benefits of the method. Participants also confirm its interest and effectiveness for testing needs of industry

A hybrid approach to workflow modelling

The increase in Business Process Management projects in the past decade has seen an increase in demand for business process modelling techniques. A rapidly growing aspect of BPM is the use of workflow management systems to automate routine and sequential processes. Workflows tend to move away from traditional definitions of business processes can often be forced to fit a model which does not suit its nature. Existing process modelling tools tend to be biased to either the informational, behavioural or object oriented aspect of the workflow. Because of this, models can often miss important aspects of a workflow. As well as managing the relationship between the types of model it is important to consider who will be using it as process models are useful in various ways. This paper reports on a case study in a manufacturing company where users were surveyed to see which are the notation that are most common in modelling based on two main categories (behavioural and informational). Research outcomes showed that there is no prevailing set of standards used for either of these categories, whilst most user feel the need to use more than one approach to model their system at any given time