Design strategies for the creation of aperiodic nonchaotic attractors

Parametric modulation in nonlinear dynamical systems can give rise to attractors on which the dynamics is aperiodic and nonchaotic, namely with largest Lyapunov exponent being nonpositive. We describe a procedure for creating such attractors by using random modulation or pseudo-random binary sequences with arbitrarily long recurrence times. As a consequence the attractors are geometrically fractal and the motion is aperiodic on experimentally accessible timescales. A practical realization of such attractors is demonstrated in an experiment using electronic circuits.Comment: 9 pages. CHAOS, In Press, (2009

Mobile Data Management

The management of data in the mobile computing environment offers new challenging problems. Existing software needs to be upgraded to accommodate this environment. To do so, the critical parameters need to be understood and defined. We have surveyed some problems and existing solution

Controlling Web Query Execution in a Web Warehouse

Most of the contemporary Web query systems have limited capabilities in controlling Web query execution. Such query facility is important as it gives us an opportunity to optimize the evaluation of a Web query. We address this issue in the context of our Web warehousing system called WHOWEDA (Warehouse Of Web Data). Specifically, we investigate different types of constraints (related to query execution) which may be imposed on a Web query such as number of query results, time of execution, restrict the evaluation of a query to specified set of Web sites, etc. An important feature of our approach is that it attempts to address the query evaluation issues which may arise due to the existence of broken links and forms in the Web

ARENA: Towards Informative Alternative Query Plan Selection for Database Education

A key learning goal of learners taking database systems course is to understand how SQL queries are processed in an RDBMS in practice. To this end, comprehension of the cost-based comparison of different plan choices to select the query execution plan (QEP) of a query is paramount. Unfortunately, off-the-shelf RDBMS typically only expose the selected QEP to users without revealing information about representative alternative query plans considered during QEP selection in a learner-friendly manner, hindering the learning process. In this paper, we present a novel end-to-end and generic framework called ARENA that facilitates exploration of informative alternative query plans of a given SQL query to aid the comprehension of QEP selection. Under the hood, ARENA addresses a novel problem called alternative plan selection problem (TIPS) which aims to discover a set of k alternative plans from the underlying plan space so that the plan interestingness of the set is maximized. Specifically, we explore two variants of the problem, namely batch TIPS and incremental TIPS, to cater to diverse set of learners. Due to the computational hardness of the problem, we present a 2 approximation algorithm to address it efficiently. Exhaustive experimental study with real-world learners demonstrates the effectiveness of arena in enhancing learners' understanding of the alternative plan choices considered during QEP selection.Comment: Add a link to access our ARENA system on the third pag

Lag synchronization and scaling of chaotic attractor in coupled system

We report a design of delay coupling for lag synchronization in two unidirectionally coupled chaotic oscillators. A delay term is introduced in the definition of the coupling to target any desired lag between the driver and the response. The stability of the lag synchronization is ensured by using the Hurwitz matrix stability. We are able to scale up or down the size of a driver attractor at a response system in presence of a lag. This allows compensating the attenuation of the amplitude of a signal during transmission through a delay line. The delay coupling is illustrated with numerical examples of 3D systems, the Hindmarsh-Rose neuron model, the R\"ossler system and a Sprott system and, a 4D system. We implemented the coupling in electronic circuit to realize any desired lag synchronization in chaotic oscillators and scaling of attractors.Comment: 10 pages, 7 figure