The Thyristor Switched Parallel Capacitors (TSPC) Converter for Power Factor Correction in Wind Power Systems

This paper presents a novel power factor correction circuit suitable for low-speed electric generators usually used in direct drive wind turbines. The Thyristor Switched Parallel Capacitors (TSPC) circuit belongs to the Controlled Series Capacitor (CSC) circuits. Those circuits have been used in power transmission lines to correct the power factor and improve the performance of the electrical system. Such a circuit can be used in wind power systems to improve and maximize the efficiency of a wind turbine. A typical direct-drive wind power system employs variable speed electric generators, but the downside is that systems like that suffer from high and variable inductive reactance. In order to correct the power factor and to improve the efficiency of the system, the inductive reactance of the generator must become equal in value to the capacitive reactance. A TSPC circuit uses a set of capacitors, connected in series with anti-parallel thyristors. In every cycle, a controller triggers the appropriate thyristors, allowing the current to pass from the capacitor which then provides the system with the capacitive reactance that matches the generator’s inductor reactance. Therefore, the TSPC circuit is able to counteract for any reactive losses and improve the power factor, as well as, the efficiency. This paper introduces this novel power factor correction circuit that employs capacitors in parallel configuration. This circuit was simulated in PSPICE and was implemented and tested in the lab. Based on the simulation and implementation results, we discuss the benefits as well as the drawbacks of the proposed circuit

Fish quality investigations using electrical impedance spectroscopy: preliminary results

The consumption of seafood has increased over the last 10 years. This article analyses impedance changes of tilapia (Oreochromis niloticus) sample measured over 36 hours by using electrical impedance spectroscopy (EIS). It was also investigated the correlations between variables in order to predictive models to degradation studies. Measurements were collected every 12 hours in order to verify any change due to deterioration. The results show that measurements in both longitudinal and transverse axes are equivalent and that the sample undergoes gradual variations in the impedance. The first set of data collected in the frequency range from 0.1 to 1,000 kHz showed that resistance varied from 310.9 (@ 0.1 kHz) to 86.8 Ω (@1 MHz) and capacitive reactance varied from -8.6 to 11.5 Ω, respectively. The forth set of data showed a decrease of 79.3% (@0.1 kHz) in the resistance part of the impedance, whereas 98.8% in capacitive reactance at 0.1 kHz. These results might suggest that there was a nutritional loss of the sample over time. Further experiments must be done over a long period of time in order to fully understand the process. EIS might be pointed out as a potential technique for fish shelf live quality control.

Comparison on the Nutrient Plunder Capacity of Orychophragmus violaceus and Brassica napus L. Based on Electrophysiological Information

The nutrient metabolism, growth and development of plants are strongly affected by its nutrient plunder, and plants have different adaptive mechanisms to low-nutrient environments. The electrophysiological activities involve almost all life processes of plants. In this study, the active transport flow of nutrient (NAF) and nutrient plunder capacity (NPC) of plants were defined based on leaf intrinsic impedance (IZ), capacitive reactance (IXc), inductive reactance (IXL) and capacitance (IC) to evaluate the nutrient plunder capacity of plants for the first time. The results indicate that Orychophragmus violaceus had higher (p < 0.01) NPC and IC and lower (p < 0.01) IR, IXc, IXL and IZ as compared to Brassica napus L., which supports a superior ion affinity and that it could be better adapted to low-nutrient environments. UAF and NPC of plants exhibited good correlations with crude protein, crude ash and water content, and precisely revealed the plunder capacity and adaptive strategies of plants to nutrients. The present work highlights that O. violaceus had superior NPC and ion affinity compared with B. napus, and provided a novel, rapid, reliable method based on the plant’s electrophysiological information for real-time determination of the nutrient plunder capacity of plants.

Virtual Laboratory: Using Electronic Workbench as Alternative Learning Physics in Covid-19 Mass Pandemic

The purpose of this research is to describe the use of assisted virtual laboratories of Electronic Workbench (EWB) in physics experiments learning. The method in this study used (1) calibration of the results of experiments with theory and (2) analysis of user responses to EWB in practicum activities. The study concluded that: 1) EWB is easy to use for practical learning, 2) capacitive reactance values obtained from calculations and observations following the theory (close to the same), 3) the time needed for one-time trial data retrieval until the analysis phase in this practicum activity is 10 minutes means that the experiment with EWB is very efficient. Based on the results obtained indicate that EWB is feasible to use as an alternative to physics learning in the mass pandemic COVID-19.

Electric properties of olive oil under pressure

The main purpose of the experiment was a thermodynamic research with use of the electric methods chosen. The substance examined was olive oil. The paper presents the resistance, capacitive reactance, relative permittivity and resistivity of olive. Compression was applied with two mean velocities up to 450 MPa. The results were shown as functions of pressure and time and depicted on the impedance phase diagram. The three first order phase transitions have been detected. All the changes in material parameters were observed during phase transitions. The material parameters measured turned out to be the much more sensitive long-time phase transition factors than temperature. The values of material parameters and their dependence on pressure and time were compared with the molecular structure, arrangement of molecules and interactions between them. Knowledge about olive oil parameters change with pressure and its phase transitions is very important for olive oil production and conservation.

A Plant’s Electrical Parameters Indicate Its Physiological State: A Study of Intracellular Water Metabolism

Almost all of a plant’s life activities involve electrochemical reactions. Plant electrical parameters respond quickly to environmental changes and are closely related to physiological activities. In this study, the theoretical intrinsic relationships between clamping force and leaf impedance (Z) or capacitive reactance (Xc) and capacitance (C) were revealed as 3-parameter exponential decay and linear models based on bioenergetics, respectively, for the first time. Leaf electrical characteristics including intrinsic impedance (IZ), capacitive reactance (IXc), capacitance (IC) and specific effective thickness (d) were successfully detected using the above-mentioned relationships and were used to manifest plant metabolic activity. The intracellular water-holding capacity (IWHC), water-use efficiency (IWUE), water-holding time (IWHT) and water transfer rate (WTR) of plant leaves were defined on the basis of IZ, IXc, IC and d, and applied to reflect the intracellular water metabolism. The results demonstrated that the leaves of Broussonetia papyrifera plants grown in agricultural soil had higher IC, d, IWHC, WTR, water content values and lower IZ, IXc values than those grown in moderately rocky desertified soil. The leaf IC, d, IWHC, WTR and water content values of herbaceous plants were higher than those of woody plants. Solanum tuberosum L. had higher leaf IC, d, IWHC and WTR values, but exhibited lower IZ, IXc, IWUE and IWHT values than Capsicum annuum L. This study highlighted that a plant’s electrical parameters based on bioenergetics clearly indicate its physiological process—e.g., the intracellular water metabolism.

Plant Electrophysiological Information Manifests the Composition and Nutrient Transport Characteristics of Membrane Protein

Background: Almost all life activities of plants are accompanied by electrophysiological information. Plant electrical parameters are considered to be the fastest response to environment.Results: In this study, the theoretically intrinsic relationships between the clamping force and leaf resistance (R), capacitive reactance (Xc) and inductive reactance (XL) were revealed as 3-parameter exponential decay based on bioenergetics for the first time. The intrinsic resistance (IR), intrinsic capacitive reactance (IXc) and intrinsic inductive reactance (IXL) in plant leaves were monitored via these relationships for the first time, and the nutrient transport capacity (NTC) in plant cells based on IR, IXc and IXL was first defined. The results indicate that IXc and IXL could be used to manifest the composition of surface and binding proteins in cell membrane, plant with high crude proteins and crude ash had higher NTC, and which accurately revealed the nutrient transport strategies in tested plants. Conclusions: This study highlights that plant electrophysiological information could effectively manifest the composition and nutrient transport characteristics of membrane protein in plant cells.

Asymmetric Entrainment Structure of Pierce Oscillator Circuit

Experimental study is presented to uncover entrainment property of Pierce oscillator circuit (i.e., one of the most standard circuits for crystal oscillators) subject to sinusoidal external forcing. In contrast to the well-known Arnold tongues observed in a wide class of forced nonlinear systems, asymmetric shape was observed as an entrainment region of the circuit in two-dimensional parameter space spanned by the external forcing strength and frequency. Computation of the impedance curve revealed that the asymmetric shape is due to positive (inductive) or negative (capacitive) reactance of the Pierce circuit, which facilitates or inhibits the circuit oscillations. We extend this insight into two coupled Pierce circuits and show that, to efficiently achieve their synchronization, it is advantageous to drive a slow oscillator circuit by a fast circuit rather than to drive a fast circuit by a slow circuit. Our study provides a guideline on an optimal network configuration for coupled crystal oscillators, which may find applications in distributed digital clocks and wireless communication systems.

Influence mechanism of pulse frequency on the corrosion resistance of Cu–Zn binary alloy

In this work, the influence of pulse frequency on the corrosion resistance of Cu–Zn binary alloy has been investigated by using electrochemical workstation, scanning electron microscope and X-ray diffraction. The results have shown that after the electric pulse treatment, the average grain size in the microstructure of high-zinc binary brass decreased and the corrosion resistance increased. The thickness of dezincification layer decreased from 49.8 to 30.8 µm. The diameter of capacitive reactance arc increased from 741.1 to 2898.0 µm. The corrosion potential increased from −0.2719 to −0.2378 V, and the corrosion current density decreased from 6.3147 × 10−6 to 4.6971 × 10−7 A cm−2 by one magnitude order.