Rafael Zamorano Ulloa

By Rafael Zamorano Ulloa, Ma. Guadalupe Hernandez Santiago and Veronica L. Villegas Rueda

Electromagnetic radiation, such as microwaves, are all the time reflected, transmitted, and/or absorbed by any kind of matter, glasses, conductors, water, ferrites, and so forth. Magnetic materials absorb greatly microwaves. The more magnetic, the more microwaves are absorbed. The aim of this chapter is to present the fundamental physics of the absorption of microwave power (energy per unit time) by ferrimagnetic and ferromagnetic matter in the nano and micro size scale. The magnetic moments and their collective modes are the basic microscopic absorbers under in-resonance and out-of-resonance conditions. Experimental setups and measurement techniques are described. The profiles of microwave absorption are described and connected to the micromagnetic environment that elicits such absorption. Section by section and the overall microwave power absorption profiles are related to the micromagnetic structures. Emphasis is made on nano- and micromagnets. These interactions of microwaves with nano- and micromagnets serve to infer microscopic magnetic information.

Part of the book: Electromagnetic Fields and Waves

By Rafael Zamorano Ulloa

Superconductivity conforms to a quantum, thermal, and electrodynamic set of physical phenomena of great interest by themselves. They have, also, the potential to be one clean energy source that technology is looking for. Superconductors do not allow static magnetic fields to penetrate them below a critical field, that is, Meissner effect. However, microwave magnetic fields do penetrate them already, and their energy is readily absorbed by the superconductor. High-temperature, perovskite superconductors do absorb microwave energy the most due to the presence of unpaired electron spins, fluxoid dynamics, and quasiparticle motion. We describe the fundamental physics of the interaction of the superconductors with microwaves. Experimental techniques to measure microwave absorption are presented. Experimental setups for absorption of energy are described in terms of the central quantity, Q. The measurements are analyzed in terms of irreversible energy exchange processes. The knowledge gained can inform the design of superconducting devices operating in microwave environments.

Part of the book: On the Properties of Novel Superconductors

By Rafael Zamorano Ulloa

Detailed electrodynamic descriptions of the fundamental workings of microwave heating devices are presented. We stress that all results come from Maxwell equations and the boundary conditions (BC). We analyze one by one the principal components of a microwave heater; the cooking chamber, the waveguide, and the microwave sources, either klystron or magnetron. The boundary conditions at the walls of the resonant cavity and at the interface air/surface of the food are given and show how relevant the BC are to understand how the microwaves penetrate the nonconducting, electric polarizable specimen. We mention the application of microwaving waste plastics to obtain a good H2 quantity that could be used as a clean energy source for other machines. We obtained trapped stationary microwaves in the resonant cavity and traveling waves in the waveguides. We show 3D plots of the mathematical solutions and agree quite well with experimental measurements of hot/cold patterns. Simulations for cylindrical cavities are shown. The radiation processes in klystrons and magnetrons are described with some detail in terms of the accelerated electrons and their trajectories. These fields are sent to the waveguides and feed the cooking chamber. Whence, we understand how a meal or waste plastic, or an industrial sample is microwave heated.

Part of the book: Electromagnetic Wave Propagation for Industry and Biomedical Applications

By Rafael Zamorano Ulloa

In this work, we concentrate on the electric fields produced by any distribution or structure of electric charges in clouds, these quantities are, for the most part, unknowns, and still we extract valuable information from their vectorial properties and working within close distances, especially on the structures that produce pronounced sinks/sources with large divergences of E → and focusing on observation points close to them. We introduce the concept of “at the verge of discharge electric field,” Ę → produced by two specific charge configurations. We detail the role the dielectric character of the cloud plays in allowing/not allowing discharge. We profile the conditions to be met by Ę → to appear and to be sustained for at least a few milliseconds. One objective of this work is to calculate some relevant quantities for a typical thundercloud modeled just at the verge of discharging. A simple electrified cloud model containing many of the features widely reported in the literature is constructed and described with some detail. The charge structures possible are delineated and the electric fields produced described. A few basic calculations are carried out for a thought experiment, moving charges around, we calculate some velocities and accelerations and analyze what we learn from it.

Part of the book: Electromagnetic Field in Advancing Science and Technology