Single-pixel imaging is a technique that can reconstruct an image of a scene by projecting a series of spatial patterns on an object and capturing the reflected light by a single photodetector. Since the introduction of the compressed sensing method, it has been possible to use random spatial patterns and reduce its number below the Nyquist-Shannon limit to form a good quality image but with lower spatial resolution. On the other hand, Hadamard pattern based methods can reconstruct large images by increasing the acquisition measurement time. Here, we propose an efficient strategy to order the Hadamard basis patterns from higher to lower relevance, and then to reconstruct an image at very low sampling rates of at least 8%. Our proposal is based on the construction of generalized basis vectors in two dimensions and then ordering in zigzag fashion. Simulation and experimental results show that the sampling rate, image quality and computational complexity of our method are competitive to the state of the art methods.

The entropy concept is studied from the perspective of several formalisms. It is reviewed the origins of this in the classical thermodynamics. It also is developed a step-by-step-clearly demonstration about it. After that, it is connected this formula with the entropy of Shannon. Elementary concepts of the quantum mechanics are explained to demonstrate the von Neumann entropy formula. It is proposed the entropy concept as a measure of the variability into the distribution of the states of a system given a set of rules that operate inside it for a while. From the perspective of the information theory, a language reaches a configuration to be optimal for communications. In this way, systems and languages can be studied using the same concept of entropy. It is stressed the importance of the teaching of the entropy because this is useful in the development of new technologies, for example the quantum communications.

Due to the absolute safety needed when sensitive information via the Internet is used, complex algorithms and cryptographic protocols such as SSL/TLS are required. This paper presents a comparison of the Triple DES cipher system that is part of the suite of encryption SSL/TLS and the cryptographic system Triple DES-96 having the following differences: Triple DES-96 begins with an information block of 96 bits, and Triple DES with a 64 block bits, besides, Triple DES-96 takes a variable permutation P V from the Triple DES keys and the number e is calculated. Furthermore, the expansion table E moves to the output 948 P. D. Filio-Aguilar et al. of S Boxes making it possible to combine with the permutation P and perform in a single instruction at run time.