The development of a device for generating ac magnetic fields based on a resonant inverter is presented, which has been specially designed to carry out experiments of magnetic hyperthermia. By determining the electric current in the LC resonant circuit, a maximum intensity of magnetic field around of 15 mT is calculated, with a frequency around of 206 kHz. This ac magnetic field is able to heat powdered magnetic materials embedded in biological systems to be used in biomedical applications. Indeed, in order to evaluate the sensitivity of the device we also present the measurements of the specific absorption rate in phantoms performed with commercially prepared Fe₃O₄ and distilled water at different concentrations.

A scanning system for specific absorption rate of ferrofluids with superparamagnetic nanoparticles is presented in this study. The system contains an induction heating device designed and built with a resonant inverter in order to generate magnetic field amplitudes up to 38 mT, over the frequency band 180-525 kHz. Its resonant circuit involves a variable capacitor with 1 nF of capacitance steps to easily select the desired frequency, reaching from 0.3 kHz/nF up to 5 kHz/nF of resolution. The device performance is characterized in order to compare with the theoretical predictions of frequency and amplitude, showing a good agreement with the resonant inverters theory. Additionally, the setup is tested using a synthetic iron oxide with 10 ± 1 nm diameter suspended in liquid glycerol, with concentrations at 1%. Meanwhile, the temperature rise is measured to determine the specific absorption rate and calculate the dissipated power density for each f. This device is a suitable alternative to studying ferrofluids and analyzes the dependence of the power absorption density with the magnetic field intensity and frequency.

Este artículo presenta una alternativa para resolver la vulnerabilidad existente en los sistemas que implementan el enmascaramiento mediante la sincronización caótica, este sistema evita que los parámetros utilizados como clave de cifrado puedan ser detectados por un atacante al implementar el modelo matemático caótico del oscilador de Rössler para codificar y establecer la sincronización entre los dispositivos transmisor-receptor; además usa dos llaves de cifrado: la primera con una longitud recomendable de 2048 caracteres y la segunda se utiliza como un valor inicial. Ambas llaves se emplean para modificar continuamente uno de los parámetros del oscilador, esto fortalece la seguridad del sistema y evita que un atacante obtenga los valores del parámetro del oscilador calculando el error de sincronización promedio menor. El uso del sistema desarrollado proporciona un cifrado resistente a ataques estadísticos, además valida datos del dispositivo transmisor (nombre de usuario, password, etc.) para autorizar la transmisión hacia el destino.

The antilock braking system (ABS) is a mechatronic system that helps a driver maintain the maneuverability of a vehicle while braking by preventing wheel lock-ups. However, the design of high-performance controllers for this type of system is complicated because of its highly nonlinear dynamics. The problem becomes even more difficult to resolve when uncertainties in the parameters appear in its dynamics. In this paper, an ABS laboratory setup mimicking a quarter car model is considered. A modified high-order sliding mode (HOSM) controller using a proportional-integral-differential (PID) control as a sliding surface was designed. This controller provides a reference value of a tire slip. The proposed controller uses a tracking error to define the slip surface through the PID controller structure, and the modified HOSM controller holds the system on the previously designed slip surface. The closed-loop system stability has been proven in the sense of Lyapunov. Finally, the ABS laboratory setup allows for experimentally checking the performance of the modified HOSM controller using a PID-sliding surface, showing a considerable increase in the efficiency of the control system compared with a PID-like controller.

In this paper, the prototype of a gas detector based on the electrical response of MgSb₂O₆ oxide at 400 °C and with a concentration of 560 ppm was designed, simulated, and fabricated. This design considers a PIC18F4550 microcontroller and a response time of 3 s for the sensor. It is worth noting that the response system can be reduced in concordance with the mathematical model of the sensor’s electrical response. The proposed device is capable of detecting one to three gases: O₂, C₃H₈, and CO₂. The configuration is achieved through three switches. In programming the prototype, factors such as the gas sensor signals, device configuration, corrective gas signals, and indicator signals were carefully considered. The characteristic of the gas detector is an operational temperature of 400 °C, which is ideal for industrial processing. This can be configured to detect a single gas or all three of them $\left({\mathrm{O}}_2,{\mathrm{C}}_3{\mathrm{H}}_8,\mathrm{a}\mathrm{n}\mathrm{d} {\mathrm{C}\mathrm{O}}_2\right)$. Each gas type has its corresponding corrective signal and an indicator-led diode. The operation concentration is 560 ppm, the device is scalable, and its programming can be extended to cover industrial networks.

A system for imaging magnetic surfaces using a magnetoresistive sensor array is developed. The experimental setup is composed of a linear array of 12 sensors uniformly spaced, with sensitivity of 150 pT*Hz−1/2 at 1 Hz, and it is able to scan an area of (16 × 18) cm2 from a separation of 0.8 cm of the sources with a resolution of 0.3 cm. Moreover, the point spread function of the multi-sensor system is also studied, in order to characterize its transference function and to improve the quality in the restoration of images. Furthermore, the images are generated by mapping the response of the sensors due to the presence of phantoms constructed of iron oxide, which are magnetized by a pulse of 80 mT. The magnetized phantoms are linearly scanned through the sensor array and the remanent magnetic field is acquired and displayed in gray levels using a PC. The images of the magnetic sources are reconstructed using two-dimensional generalized parametric Wiener filtering. Our results exhibit a very good capability to determine the spatial distribution of magnetic field sources, which produce magnetic fields of low intensity.