We demonstrate that the tuning of the optical properties of a photonic crystal infiltrated with liquid crystal can be calculate using the Von-Laue diffraction condition. We present a simple formula to predict the shift of the stop band for all the diffraction orders using an effective index of the composite structure. We consider that our formula is useful to determine in a simple manner the shift of the optical properties of tunable photonic crystals. We compare the accuracy of our method with calculations obtained with the Plane Wave Method.

From the Publisher:"This book is a follow-up to the IChemE symposium on "Neural Networks and Other Learning Technologies", held at Imperial College, UK, in May 1999. The interest shown by the participants, especially those from the industry, has been instrumental in producing the book. The papers have been written by contributors of the symposium and experts in this field from around the world. They present all the important aspects of neural network utilisation as well as show the versatility of neural networks in various aspects of process engineering problems - modelling, estimation, control, optimisation and industrial applications."--BOOK JACKET.

The so-called "electronic documents" are becoming prevalent in Design process. Nevertheless, design documents on paper are still necessary to maintain those products that are now in the market, as well as they are the basis for the design and development of the next generation of products, because they contain the "know-how" on products and processes. Hence, the necessary use of documents on paper reduces the efficiency that could be achieved in this key aspect of design process by simply transferring information contained in paper documents to electronic ones. In order to solve this problem some transfer methods have been developed. The most widely used method for transferring documents to electronic formats is scanning, which produces "raster images". The document is broken down into a matrix of pixels. As a result, we may obtain a high quality electronic image of the document (depending on size and density of pixel). But the semantic information contained in the document is not transferred to the electronic file, i.e. the meaning of the symbols is not interpreted. Therefore, a second step in the process known as "vectorization" is needed, by means of which the information necessary to define geometrical entities (such as straight lines, arcs, etc.) and symbols (such as letters) is obtained from a raster image. Then, this information is stored on an electronic file following the common methods used in CAD files. The current work presents the state of the art of vectorization. Different vectorization methods are compared and the importance of advancing on different levels of intelligence (capacity of discrimination) is stated. Finally the paper presents the process of vectorization the authors are working on.