Two new techniques for the compression of 2D and 3 D medical images are proposed in the paper. Both algorithms are based on DCT transforms and the aim is to ensure a nearly lossless image transmission and storage with a compression rate able to reduce significantly the amount ofdata. The first technique, used for the storage of2D medical images (microscope, radiographic, X-ray images, ultrasonic images, computer tomograph sections) is based on the extraction of a 'region of interest' in the original image. In fact, in most situations, only a limited region of the medical image is interesting for diagnosis. For compression, a direct DCT is applied on the original image, preserving a different number of coefficients inside and outside the region of interest (must higher inside the region). The compression ratio obtained with this method depends on the size ofthe selected region and on the number ofDCT coefficients preserved, ranging from 4 to 20. The second technique is based on the correlation existing between contiguous axial sections obtained from the CT. The 3D volume data is compressed using an original axial section and the difference images between successive sections. The advantage of this method consists in reducing the number of DCT coefficients necessary for a nearly lossless compression ofthe difference images. The compression ratio obtained ranges between 6 and 10, without significant losses in the image quality.
A dc-dc buck converter controlled by naturally sampled, constant-kequency pulse width modulation in continuous conduction mode gives rise to a g r c a~ variety of bchaviors, dcpcnding on the values of the par;imeters or the circuit. This paper rcexamines the buck converter studied by Fossas and Olivar (I 11) and analyzcs a method of controlling chaos, that is to convert chaotic oscillations into oncs with a pcriodic timc dependence.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.