Simple and inexpensive microwave setup for industrial based applications: Quantification of flower honey adulteration as a case study.

A simple and inexpensive microwave measurement setup based on measurements of magnitudes of transmission properties ( | S 21 | dB ) is proposed for industrial-based microwave aquametry (moisture or water content) applications. An easy-to-apply calibration procedure based on normalization is implemented to eliminate systematic errors in the measurement system. As a case study, we applied this setup for the quantification of water-adulteration in flower honey. After validating this system by distilled water and pure flower honey measurements, | S 21 | dB measurements of the pure flower honey with various adulteration percentages ( δ ) up to 9% are conducted to examine the performance of the measurement setup for quantification of water adulteration. A multi-dimensional fitting procedure is implemented to predict δ using the proposed inexpensive microwave measurement setup. It is shown that it is possible to quantify an adulteration level with an accuracy better than ∓ 1 % by the proposed measurement setup and the applied multi-dimensional fitting procedure.

Development of Tunable Ferroelectric Ceramic Capacitors.

Ferroelectric perovskite ceramics with a high dielectric constant, low loss, high tunability, and high electric breakdown are ideal for nonlinear transmission lines (NLTLs) to generate radio frequency (RF) signals at high-power levels. To achieve the required properties, a comprehensive study of the material phase transitions and the optimal ratio adjustment between the chemical elements in the perovskite crystal structure is required. The advancement of this solid-state technology is the most promising optimization for NLTLs in developing high-power (>100 MW) devices with high tunability (>60%) and high repetition rate (>1 kHz) for soliton generation. The barium strontium zirconium titanate (BSZT) ceramic compositions were synthesized and characterized to maximize material tunability. The composition Ba0.97Sr0.03Zr0.2Ti0.8O3 exhibited a high permittivity (>12200), low loss tangent (< 0.01), and an exceptional tunability of the order of 79% at an electric field of 10 kV/cm near the phase temperature transition at 300 K. Ferroelectric ceramic is an outstanding material with promising characteristics for producing RF signals in an NLTL, and here, the BSZT is considered for this application.

Analysis of the sharpening effect in gyromagnetic nonlinear transmission lines using the unidimensional form of the Landau-Lifshitz-Gilbert equation.

Continuous nonlinear transmission lines (NLTLs), also known as gyromagnetic lines, consist of ferrite-based magnetic cores biased by an external magnetic field. Over the past years, many analytical and experimental studies have predicted the rise time reduction of the input pulse to the range of a few nanoseconds or even hundreds of ps experimentally observed in such gyromagnetic lines. This effect, known as pulse sharpening, is investigated in this paper built on a model based on a periodic structure of inductive-capacitive cells in series with magnetization-driven voltage sources expressed by the one-dimensional form (1D) of the Landau-Lifshitz-Gilbert (LLG) gyromagnetic equation. We explore the model through parametric study under various input-pulse parameters to understand the physics behind the ferrimagnetic material responses. Moreover, the numerical results obtained from computational simulations using Mathematica (v. 12.1) show how the line parameters (input voltage, damping constant, saturation magnetization, and length) affect the sharpening effect, which is quantified by the switching time. Our results on ferrite-loaded coaxial lines have confirmed many results found in the literature. We validated with a good agreement the proposed model with the result obtained by Dolan in 1993 using the same 1D form of the LLG equation, thus showing that the model proposed here is suitable to quantify the sharpening effect produced by a gyromagnetic NLTL.

Assessment of heart rate variability by application of central tendency measure.

The heart rate variability (HRV) is an indicator of the subject homeostasis alterations. For a healthy individual, the HRV shows a nonlinear behavior, thus requiring a nonlinear approach to provide additional information about HRV dynamics. In this work, the nonlinear techniques, central tendency measure (CTM) and second-order difference plot, are applied to HRV analysis using the successive difference of RR intervals in a time series. In total are analyzed 170 tachograms collected by Polar monitor and then classified into three groups according to a cardiologist: healthy young adults, adults in preoperative evaluation for coronary artery bypass grafting for severe coronary disease and premature newborns. This approach identified the tachograms with high and low variability, which demonstrates the ability of CTM to classify and quantitatively characterize cardiac RR intervals.

Application of an automatic adaptive filter for Heart Rate Variability analysis.

The presence of artifacts and noise effects in temporal series can seriously hinder the analysis of Heart Rate Variability (HRV). The tachograms should be carefully edited to avoid erroneous interpretations. The physician should carefully analyze the tachogram in order to detect points that might be associated with unlikely biophysical behavior and manually eliminate them from the data series. However, this is a time-consuming procedure. To facilitate the pre-analysis of the tachogram, this study uses a method of data filtering based on an adaptive filter which is quickly able to analyze a large amount of data. The method was applied to 229 time series from a database of patients with different clinical conditions: premature newborns, full-term newborns, healthy young adults, adults submitted to a very-low-calorie diet, and adults under preoperative evaluation for coronary artery bypass grafting. This proposed method is compared to the demanding conventional method, wherein the corrections of occasional ectopic beats and artifacts are usually manually executed by a specialist. To confirm the reliability of the results obtained, correlation coefficients were calculated, using both automatic and manual methods of ltering for each HRV index selected. A high correlation between the results was found, with highly significant p values, for all cases, except for some parameters analyzed in the premature newborns group, an issue that is thoroughly discussed. The authors concluded that the proposed adaptive filtering method helps to efficiently handle the task of editing temporal series for HRV analysis.

Differential uncertainty analysis for evaluating the accuracy of S-parameter retrieval methods for electromagnetic properties of metamaterial slabs.

We apply a complete uncertainty analysis, not studied in the literature, to investigate the dependences of retrieved electromagnetic properties of two MM slabs (the first one with only split-ring resonators (SRRs) and the second with SRRs and a continuous wire) with single-band and dual-band resonating properties on the measured/simulated scattering parameters, the slab length, and the operating frequency. Such an analysis is necessary for the selection of a suitable retrieval method together with the correct examination of exotic properties of MM slabs especially in their resonance regions. For this analysis, a differential uncertainty model is developed to monitor minute changes in the dependent variables (electromagnetic properties of MM slabs) in functions of independent variables (scattering (S-) parameters, the slab length, and the operating frequency). Two complementary approaches (the analytical approach and the dispersion model approach) each with different strengths are utilized to retrieve the electromagnetic properties of various MM slabs, which are needed for the application of the uncertainty analysis. We note the following important results from our investigation. First, uncertainties in the retrieved electromagnetic properties of the analyzed MM slabs drastically increase when values of electromagnetic properties shrink to zero or near resonance regions where S-parameters exhibit rapid changes. Second, any low-loss or medium-loss inside the MM slabs due to an imperfect dielectric substrate or a finite conductivity of metals can decrease these uncertainties near resonance regions because these losses hinder abrupt changes in S-parameters. Finally, we note that precise information of especially the slab length and the operating frequency is a prerequisite for accurate analysis of exotic electromagnetic properties of MM slabs (especially multiband MM slabs) near resonance regions.

Edge state and crisis in the Pierce diode.

We study the chaotic dynamics of the Pierce diode, a simple spatially extended system for collisionless bounded plasmas, focusing on the concept of edge of chaos, the boundary that separates transient from asymptotic dynamics. We fully characterize an interior crisis at the end of a periodic window, thereby showing direct evidence of the collision between a chaotic attractor, a chaotic saddle, and the edge of chaos, formed by a period-3 unstable periodic orbit and its stable manifold. The edge of chaos persists after the interior crisis, when the global attractor of the system increases its size in the phase space.

Bouncing ball problem: stability of the periodic modes.

Exploring all its ramifications, we give an overview of the simple yet fundamental bouncing ball problem, which consists of a ball bouncing vertically on a sinusoidally vibrating table under the action of gravity. The dynamics is modeled on the basis of a discrete map of difference equations, which numerically solved fully reveals a rich variety of nonlinear behaviors, encompassing irregular nonperiodic orbits, subharmonic and chaotic motions, chattering mechanisms, and also unbounded nonperiodic orbits. For periodic motions, the corresponding conditions for stability and bifurcation are determined from analytical considerations of a reduced map. Through numerical examples, it is shown that a slight change in the initial conditions makes the ball motion switch from periodic to chaotic orbits bounded by a velocity strip v=+/-Gamma(1-epsilon) , where Gamma is the nondimensionalized shaking acceleration and epsilon the coefficient of restitution which quantifies the amount of energy lost in the ball-table collision.

Experimental characterization of a 6.7 GHz coaxial Bragg reflector.

A coaxial line periodically loaded by circular disks on the inner conductor is designed and constructed to act as Bragg reflector in the 4.0-9.5 GHz frequency range. This is achieved by placing 10 disks (0.35 cm thick and 6.22 cm in diameter) equally spaced by the periodic distance of 1.8 cm on a coaxial waveguide with inner and outer diameters of 6.90 and 4.22 cm. Experiments on a periodic structure made from stainless steel demonstrate a band gap of 5.6 GHz centered at the 6.7 GHz design frequency in close agreement with 3D microwave computer simulations.