Abstract
Automatic image registration is a process related to various application fields such as remote sensing, medicine, computer vision, among others. Particularly in remote sensing, the ever increasing number of available satellite images asks for automatic image registration methods, capable of correctly align a new image. An automatic image registration method is proposed, based on the identification of a thin line through the Hough transform, from the diagonal brighter strip visible on the correlation images. This procedure is applied for both directions. Dividing an image into tiles and taking the center of each tile as a point, a geometric correction at the subpixel level may be achieved. Measures for an objective assessment of the geometric correction quality are also proposed, as a complement to the traditional RMS of the errors and visual inspection. An orthorectified Landsat image and an ASTER image with an approximate geometric correction were used. The images were superimposed and resampled. An image registration with subpixel accuracy was achieved. The proposed methodology has showed to be able to correctly align two images, having a priori a "gold standard" image covering a considerable part of the image to be registered. © 2008 SPIE.

Abstract
High frequency synthetic aperture sonar systems require demanding tolerances in motion errors and medium phase stability. This article proposes a new method that mitigates the problems associated with small wavelength related errors. By dividing the received signal bandwidths in to several smaller ones and conjugate complex multiplying them, a new signal is obtained with longer effective wavelength, thus reducing the impact of motion errors and medium phase fluctuations.

Abstract
We present a potential sensor head for the simultaneous measurement of temperature and strain based on the concatenation of two long-period fiber gratings arc-induced in different fibers. Despite being the temperature and strain sensitivities of the individual gratings well defined, we demonstrate that the sensor cannot perform the simultaneous measurement of those physical parameters. This fact, results from the uncertainty in finding the determinant of the inverse matrix. (C) 2008 Wiley Periodicals, Inc.

Abstract
Learning and understanding a framework is usually a major obstacle to its effective reuse. Before being able to use a framework successfully, users often go through a steep learning curve by spending a lot of effort understanding its underlying architecture and design principles. This is mainly due to users having to understand not only single isolated classes, but also complex designs of several classes whose instances collaborate for many different purposes, and using many different mechanisms. In addition, frameworks are also full of delocalized plans, and use inheritance and delegation intensively, which makes their design more difficult to grasp. How to obtain the necessary information from the framework itself and its accompanying documentation is the main problem with framework understanding. Considering its importance, this paper presents an initial attempt to capture, in the pattern form, a set of proven solutions to recurrent problems of understanding frameworks. The fundamental objective of this work is to help non-experts on being more effective when trying to learn and understand object-oriented frameworks. © 2008 is held by the author(s).

Abstract
A fiber optic sensor for liquid refractive index measurement based on a Fabry-Perot interferometer is described. The interferometer is achieved between the reflection of a short fiber Bragg grating and the Fresnel reflection from the cleaved fiber end. This fiber end is then in contact with the liquid sample to provide refractive index measurements. The sensor is characterized by immersing the fiber tip in distilled water with different concentrations of ethylene glycol. A linear relation of the interferometer fringe visibility with refractive index variation is observed, and a resolution of similar to 10(-3) is obtained. It is also shown that the sensor operation is independent of temperature effects, other than the one related to temperature-induced change of the liquid refractive index. (c) 2008 Society of Photo-Optical Instrumentation Engineers.

Abstract