PNEUMATIC HYDROPOWER SYSTEMS

The following thesis investigates the performance and economics of a Pneumatic Water Engine capable of extracting energy from differential heads of water in the two to three metre range. Initial concepts are discussed and a system configuration is physically modelled at a laboratory scale. Outline designs using a variety of materials are developed and these provide a basis for the estimation of a probable capital cost using standard Civil Engineering methods. The proposed system is mathematically modelled using a lumped mass approach to the complex hydrodynamics. The resultant differential equations are solved by means of a variable Runge Kutta numerical analysis. The model includes the thermodynamic aspects of the system's compressible airflow. A computer program has been developed from the mathematical model and Is utilized in a series of parametric studies. An economic assessment based upon both the average power output achieved during the parametric studies and the probable capital cost of the system is presented, together with an estimate of the cost per kilowatt-hour of the electricity produced. This assessment takes into account maintenance costs, expected value of the energy produced and the possible effects of both Water Abstraction Charges and Local Authority Rating. In addition to the parametric studies a final, more rigorous optimization of the system involving a number of the many interacting variables has been undertaken. This optimization is achieved via Cumulative Evolutionary Design techniques involving the use of Genetic Algorithms. An optimal design of the chamber shape is achieved in the same manner.Energy Technology Support Unit (ETSU), Harwel

Elegant object-oriented software design via interactive, evolutionary computation

Design is fundamental to software development but can be demanding to perform. Thus, to assist the software designer, evolutionary computing is being increasingly applied using machine-based, quantitative fitness functions to evolve software designs. However, in nature, elegance and symmetry play a crucial role in the reproductive fitness of various organisms. In addition, subjective evaluation has also been exploited in interactive evolutionary computation (IEC). Therefore, to investigate the role of elegance and symmetry in software design, four novel elegance measures are proposed which are based on the evenness of distribution of design elements. In controlled experiments in a dynamic IEC environment, designers are presented with visualizations of object-oriented software designs, which they rank according to a subjective assessment of elegance. For three out of the four elegance measures proposed, it is found that a significant correlation exists between elegance values and reward elicited. These three elegance measures assess the evenness of distribution of 1) attributes and methods among classes; 2) external couples between classes; and 3) the ratio of attributes to methods. It is concluded that symmetrical elegance is in some way significant in software design, and that this can be exploited in dynamic, multiobjective IEC to produce elegant software designs. © 1998-2012 IEEE

Agent-based Support for Interactive Search in Conceptual Software Engineering Design

While recent attempts to search a conceptual software engineering design search space with multi-objective evolutionary algorithms have yielded promising results, the practical application of such search-based techniques remains to be addressed. This paper reports initial findings of the application of software agents in support of an interactive, user-centered conceptual software design scenario. The supporting role of a number of single responsibility agents is described and results for a case study indicate that the application of such agents to search-based design scenarios provides efficient, high performance and effective support. The notion of interactive, joint human-computer activity appears to map well to conceptual software design scenarios: focus on superior design concepts and thence to useful and interesting designs provides a natural and effective way of narrowing the population based search. In addition, agents and the human designer appear to interact as cooperative “team players”, jointly influencing the evolutionary algorithm based search. Nevertheless, challenges remain, including expanding the scale of implementation of underlying technologies to support distributed, collaborative design. Categories and Subject Descriptors D.2.2. [Software Engineering]: Design tools and techniques