An investigation into moving electromagnetic near-field hotspots inside a resonant cavity is presented. The investigation focused on simulating an alternative approach to microwave thermal ablation of tumours by manipulating the interaction between electromagnetic near fields instead of utilising an interstitial antenna. The methodology comprised comparing various electromagnetic field solvers, verifying the simulation techniques, characterising a rectangular resonant cavity, and attempting to manipulate the position of its hotspots by introducing a feed phase shift. The effects of dielectric media were also investigated. Progressive hotspot movement was achieved using input phase manipulation between 2.55 and 2.7 GHz with the feeds on opposite walls. No pattern change was evident at the system's eigenfrequencies, indicating a constant field pattern at its resonant peaks. Furthermore, it was determined that the characteristic modes of the system were narrowband, such that the addition of dielectric material altered the system's resonance. Therefore, the application of this method to thermal ablation, which requires high precision, accuracy and control, was deemed impractical. Future recommendations include using adjustable geometry to design field patterns, comparing dielectric media with significant thermal mass, and investigating the 'inverse problem' to create a specific current distribution around the resonant cavity and induce the desired hotspot patterns.

Abstract This paper presents a study about the dielectric constant εr, dielectric loss tangent tan g(δ) and effective electrical conductivity σe of graphene, graphite and graphene-bakelite combination using the resonant cavity method. For this purpose, cylindrical samples with diameter of 30 mm and thickness of 4.5 mm were analyzed taking into account the central frequency f0 = 3.5 GHz, according to 5G technology standards. The constants εr and tan g(δ) were obtained from the resonance frequency fa of measured scattering parameters (S-parameters), when the cavity was loaded with the samples. An empirical equation was developed to model the relation between fa and εr. With this empirical equation it was found εr = 9.3203 and tan g(δ) = 0.7000 for graphene and εr = 17.1508 and tan g(δ) = 0.2700 for graphite. The addition of bakelite in combination with graphene allowed controlling the dielectric properties of these composites. The results, obtained in this macroscale characterization, are interesting for Telecommunications Engineering, especially in the development of radiation-absorbent material, which is suitable for mitigation of interference between different wireless communication systems. gδ g δ g(δ graphenebakelite method purpose 3 45 4 5 4. f 35 3. GHz G standards Sparameters, Sparameters S , (S-parameters) 93203 9 3203 9.320 07000 0 7000 0.700 171508 17 1508 17.150 02700 2700 0.270 composites results characterization Engineering radiationabsorbent radiation absorbent material systems (S-parameters 9320 320 9.32 0700 700 0.70 17150 1 150 17.15 0270 270 0.27 932 32 9.3 070 70 0.7 1715 15 17.1 027 27 0.2 93 9. 07 7 0. 171 17. 02 2

Resumen Este trabajo aborda el diseño optimizado del filtro LCL y el controlador del lazo interno de corriente (PI) para un inversor trifásico de puente completo de un sistema de generación distribuida (GD). El objetivo es mejorar el desempeño y la calidad de la energía que suministran estos sistemas en su interconexión con la red eléctrica. En ese sentido, las variables de optimización son los parámetros del filtro y del controlador y se plantean dos funciones objetivo, una relacionada con la razón de atenuación armónica del filtro y otra con el desempeño del control, específicamente, la integral del error absoluto por el tiempo (ITAE, por sus siglas en inglés). Se resalta que la primera función objetivo depende de los parámetros del filtro, mientras que la segunda depende de los parámetros del controlador y también del filtro (planta); por lo cual, a diferencia de otros trabajos, la solución se aborda de manera conjunta y se resuelve utilizando optimización por enjambre de partículas (PSO, por sus siglas en inglés) a través de MatLab. Para la optimización, en primer lugar, se obtiene el modelo matemático del filtro y del controlador de corriente. Las restricciones, en el caso del filtro, se imponen en los parámetros de inductancia total, frecuencia de resonancia y resistencia de amortiguamiento; mientras que, en el controlador las restricciones buscan asegurar que las ganancias seleccionadas respeten el factor de amortiguamiento y ancho de banda propuesto. Derivado del proceso de optimización, en la parte final del documento se muestra la validación de los resultados obtenidos a nivel simulación, utilizando el esquema eléctrico de un inversor implementado en el software PSIM® de PowerSim®, donde se prueba el controlador y filtro diseñado ante cambios de potencia activa y reactiva. Con ello se demuestra la efectividad del diseño optimizado basado en PSO.

Abstract This work addresses the optimized design of the LCL filter and the internal current controller (PI), for a three-phase full-bridge inverter, of a distributed generation (DG) system. The objective is to improve the performance and quality of the energy supplied by these systems in their interconnection with the electrical grid. In this regard, the optimization variables are the filter and controller parameters; and two objective functions are established, one related with the filter harmonic attenuation ratio and other with the control performance, specifically, the integral time absolute error (ITAE). It is highlighted that the first objective function depends on the filter parameters, while the second one depends on the parameters of both the controller and the filter (plant); this is why, different to other proposals, here the solution is addressed in a combined way and is solved using particle swarm optimization (PSO) by means of MatLab. For the optimization, first, the mathematical model of the filter and the current controller is obtained. The constraints, in the case of the filter, are in the following parameters: total inductance, resonant frequency and damping resistance; while, in the controller, the constraints allow the selected gains to fulfill the proposed damping factor and bandwidth. As a result of the optimization process, in the final part of the document, the validation of the obtained results is shown, using the electrical schematic of an inverter implemented in the PSIM® software by PowerSim®, where the controller and filter designed is tested under active and reactive power changes; showing the effectiveness of the optimized design based on PSO.

Abstract We show that the technique of Stark-chirped rapid adiabatic passage (SCRAP) can be implemented in tripod quantum systems. We propose a robust scheme to create a coherent superposition of two ground states, in a tripod system, via the Stark-shift-chirped rapid adiabatic passage technique. The technique of tripod-SCRAP uses four laser pulses: an intense far-off-resonance Stark laser pulse modifies the transition frequency between the states by Stark shifting their energies and three nearly resonant pump, Stokes and control laser pulses that fractionally transfer the population between the ground states via the adiabatic passage. In our scheme, the pulse duration of the pump pulse must be larger than the pulse duration of the Stokes and control pulses, although with a smaller amplitude, and the atom encounters with the pump and Stokes laser pulses with counterintuitive pulse sequence (the Stokes pulse arrives before the rest of the pulses). This technique applies to one-photon as well as multiphoton transitions, and the two fields do not need to vanish simultaneously. Tripod-SCRAP can be a powerful alternative tool for f-STIRAP and tripod-STIRAP techniques, at least when inhomogeneous broadenings are included. This scheme is robust against variations of intensities of the laser pulses, of detunings from resonances, and the time delay between the pulses.

Abstract In this paper, it is demonstrated that the efficiency and ability to transfer power to the load in three-coil wireless power transfer (WPT) systems are always higher than in equivalent four-coil ones. On the other hand, it is shown that there are features attainable in four-coil WPT system that are not in three-coil ones. For instance, in a four-coil WPT system, which can be divided into source, two communication, and load circuits, it is possible to devise a method for which the maximum power transferred to the load circuit or the maximum efficiency do not depend on the mutual inductance between the two communication coils, independently of the load resistance value. The necessary conditions to achieve the above feature together with the overall circuit analysis are discussed in details and practical results presented.

Abstract Wideband, dual sense circularly polarized (CP), asymmetric circular slot fed by coplanar waveguide is proposed and designed. Dual polarizations are obtained by using a horizontal stub to the feed line and embedding the L-shaped strip onto the slotted ground plane. The simulated result of impedance bandwidth shows wideband performance is produced by four resonant modes. Some key parameters are studied to analyze the characteristics of the proposed antenna. The overall volume of the proposed antenna is 18 mm × 18 mm × 1.6 mm. The measured value of 10 dB impedance bandwidth is 112%at frequencies from 4.2 GHz to 14.9 GHz with voltage standing wave ratio (VSWR) ≤ 2. The 3-dB axial ratio bandwidths are 39.3% for the lower band which senses right-hand circular polarization (RHCP) and 2.8% for the upper band which senses left-hand circular polarization (LHCP) relative to the center frequency of 6.1GHz and 14.1 GHz, respectively. The proposed structure gives a good radiation pattern with moderate gain.

Abstract In this paper we show how the IBM superconducting chips can be a powerful tool for teaching foundations of quantum mechanics for undergraduate students (for graduates as well, in some cases). To this end, we briefly discuss about the main elements of the IBM Quantum Experience platform necessary to understand this paper, i.e., how to implement operations and single-qubit measurements. We experimentally study the dynamics of single spin systems interacting with static and time-dependent magnetic fields. First, we study the resonant behavior of a single spin coupled to a time-dependent rotating magnetic field. To end, we study the Larmor precession phenomenon. In both cases we show the theoretical and real experimental implementation. This article could be useful in introductory courses on quantum mechanics and nuclear magnetic resonance foundations, for example.

Abstract A compact broadband millimeter wave antenna for intelligent transportation (ITS) application is proposed in this paper. This antenna uses coplanar wave guide feeding technique for broad bandwidth. The proposed antenna works at 79 GHz resonant frequency having a large bandwidth of 78.2 GHz. The measured gain of the antenna is 17.5 dBi. The proposed antenna is very suitable for short range radar (SRR) application and %G technologies.

Se propone un enfoque de control novedoso para seguimiento por realimentación de la salida para sistemas mecánicos vibratorios del tipo masa-resorte-amortiguador lineales sub-actuados. La metodología de diseño de control que se presenta considera robustez con respecto de dinámicas no modeladas y fuerzas externas. El esquema de control propuesto solamente requiere mediciones de la variable de la salida de posición. Se utiliza compensación integral del error de seguimiento de manera apropiada para evitar la estimación en tiempo real de las perturbaciones. Resultados analíticos y numéricos muestran la efectividad del esquema de control activo de vibración para atenuación de vibraciones resonantes y caóticas afectando la respuesta de la variable de salida.

A novel output feedback tracking control approach is proposed for underactuated linear mass-spring-damper vibrating mechanical systems of multiple degrees of freedom. The presented control design methodology considers robustness against unmodeled dynamics and external forces. The proposed control scheme only requires measurements of the position output variable. Tracking error integral compensation is properly used to avoid real-time disturbance estimation. Analytical and numerical results prove the effectiveness of the introduced active vibration control scheme for resonant and chaotic vibration attenuation on the output variable response.

Los sistemas de generación de ozono generalmente utilizan la modulación por amplitud de pulsos (PAM) para variar o controlar la concentración de ozono. En este trabajo se presentan los resultados obtenidos luego de la implementación de la modulación por densidad de pulsos (PDM) en la fuente de potencia de un sistema de generación de ozono y el mejoramiento logrado en la curva característica de la eficiencia. Las técnicas PAM y PDM se aplicaron en un sistema de generación de ozono con inversor push-pull auto-resonante. La amplitud de voltaje ajustada en la onda de potencia PDM se determinó de la condición de la onda PAM donde se obtuvo la máxima eficiencia en el 60 % de los puntos de operación del sistema de generación de ozono.

The ozone generation systems generally use the pulse amplitude modulation (PAM) to vary or control the ozone concentration. The results obtained after the implementation of pulse density modulation (PDM) in the power supply system of an ozone generation and the improvement achieved in the efficiency curve is presented in this paper. PAM and PDM techniques were applied in ozone generation system with push-pull inverter resonant self. The adjusted voltage amplitude of the PDM waveform power is determined from the condition of the PAM waveform where the maximum efficiency was obtained; Thus achieving increased efficiency in 60% of operating points ozone generation system.

The role of an Automatic Gain Control (AGC) circuit is to provide relatively constant output amplitude regardless of the signal variations at its input. For this reason, AGC circuits reduce the required input dynamic range of subsequent conditioning circuits for resonant sensors, where information is frequency modulated. An AGC circuit in a 0.35µm and biased with V DD=3V is presented in this paper, to be used in sensor systems operating from DC to 100kHz. The Variable Gain Amplifier is based on a novel technique which uses a pre-distortion piecewise-linear block to exponentially vary the gain. The total harmonic distortion is lower than -54dB and the power consumption of the whole system is 12.4mW. The results were obtained by HSpice simulations.

Los circuitos de Control Automático de Ganancia (AGC), cuya función es mantener relativamente constante el nivel de la señal de salida independientemente de las variaciones en la amplitud de entrada, permiten reducir el rango dinámico de entrada de los bloques de acondicionamiento en sensores resonantes, donde la información está modulada en frecuencia. En este trabajo se presenta un circuito AGC en tecnología CMOS de 0.35µm con voltaje de polarización V DD=3V para sistemas sensores trabajando a frecuencias desde DC hasta 100kHz. El Amplificador de Ganancia Variable fue implementado de manera novedosa mediante un bloque de predistorsión lineal a tramos que realiza un control exponencial de la ganancia. La distorsión armónica total del sistema es inferior a -54dB, con un consumo de potencia global de 12.4mW. Los resultados aquí mostrados fueron obtenidos mediante simulaciones utilizando HSpice.

High speed maglev is one of the most important reformations in the ground transportation systems because of its no physical contact nature. This paper intends to study the dynamic response of the single-span guideway induced by moving maglev train. The dynamic model of the maglev train-guideway system is established. In this model, a maglev train consists of three vehicles and each vehicle is regarded as a multibody system with 34 degrees-of-freedom. The guideway is modeled as a simply supported beam. Considering the motion-dependent nature of electromagnetic forces in the maglev system, an iterative approach is presented to compute the dynamic response of a maglev train-guideway system. The histories of the train traversing the guideways are simulated and the dynamic responses of the guideway and the train vehicles are calculated. A field experiment is carried out to verify the results of the analysis. The resonant conditions of single-span guideway are analyzed. The results show that all the dynamic indexes of train-guideway system are far less than permissive values of railway and maglev system, the vertical resonant of guideways caused by periodical excitations of the train will not happen.

This review deals with surface-enhancved Raman scattering (SERS) employing Langmuir-Blodgett (LB) films, which serve as model systems for developing theoretical and experimental studies to elucidate the SERS effect. In addition, LB films have be used as integral parts of molecular architectures for SERS-active substrates. On the other hand, SERS and surface-enhaced resonant Raman scattering (SERRS) have allowed various properties of LB films to be investigated, especially those associated with molecular-level interactions. In the paper, emphasis is placed on single molecule detection (SMD), where the target molecule is diluted on an LB matrix of spectral silent material (low Raman cross section). The perspectives and challenges for combining SERS and LB films are also discussed.

En este artículo se presenta un esquema de control activo de vibraciones para atenuar las amplitudes de vibración síncrona inducidas por el desbalance en un sistema rotorchumaceras; donde una de las chumaceras puede ser desplazada automáticamente para modificar la longitud efectiva del rotor, y como consecuencia, la rigidez del rotor. El control de la rigidez dinámica se basa en un análisis de la respuesta en frecuencia, control de velocidad y en el uso de esquemas de aceleración, para evadir las amplitudes de la vibración en la resonancia mientras el sistema rotatorio pasa (acelerado o desacelerado) a través de una velocidad crítica. Se utiliza identificación algebraica para estimar el desbalance en línea, mientras el rotor es llevado a la velocidad de operación deseada. Algunas simulaciones numéricas y resultados experimentales son incluidos para mostrar las propiedades de la compensación del desbalance y la robustez del esquema de control activo de vibraciones propuesto, cuando el rotor se opera a una velocidad por encima de la primera velocidad crítica.

This paper presents an active vibration control scheme to reduce unbalance induced synchronous vibration in rotorbearing systems supported on two ball bearings, one of which can be automatically moved to control the effective rotor length and, as an immediate consequence, the rotor stiffness. This dynamic stiffness control scheme, based on frequency analysis, speed control and acceleration scheduling, is used to avoid resonant vibration of a rotor system when it passes (runup or coast down) through its first critical speed. Algebraic identification is used for online unbalance estimation at the same time that the rotor is taken to the desired operating speed. Some numerical simulations and experiments are included to show the unbalance compensation properties and robustness of the proposed active vibration control scheme when the rotor is started and operated over the first critical speed.

Fenômenos oscilatórios e ressonantes são explorados em vários cursos experimentais de física. Em geral os experimentos são interpretados no limite de pequenas oscilações e campos uniformes. Neste artigo descrevemos um experimento de baixo custo para o estudo da ressonância em campo magnético da agulha de uma bússola fora dos limites acima. Nesse caso, termos não lineares na equação diferencial são responsáveis por fenômenos interessantes de serem explorados em laboratórios didáticos.

Oscillatory and resonant phenomena are usually explored in many experimental physics courses. These experiments are generaly interpreted in the regime of small angle oscillation and uniform fields. In this paper we describe a low cost resonance experiment to explore physics phenomena out of this regime. In such case, non-linear terms in the differential equation are responsible for interesting physics behavior of the oscillatory system.