Capacitor Research Articles

Dielectric properties for characterization of fly ash-based geopolymer binders

In this study, a method for determining the setting time and the porosity of fly ash-based geopolymer binders (FAGPBs) has been established. This method permits a real-time monitoring of the geopolymerisation and hardening progressions. A parallel plate capacitor cell technique was used to determine the dielectric constant εr' and dielectric loss factor εr'' of fresh and hardened mixes. Equivalent model-circuits of the measurement system were developed, and the accuracy of the system was verified. The dielectric properties were monitored at different ages until 56 days over a frequency range of 0.1–60 MHz. The alkaline solution to fly ash ratio, sodium silicate to alkaline solution ratio, and sodium hydroxide solution molarity were varied to study their effects on the dielectric properties. It was found that dielectric properties can provide valuable information when measured in the frequency range of 10–25 MHz. In this range, the dielectric values responded well to the variations with age and with mix properties. The relationships between the dielectric properties and the different physical states and constituent materials of FAGPBs could be used for quality control applications. The εr' and εr'' time plots were effectively utilized to determine the setting time and the rate of geopolymerisation of FAGPBs. Measurements showed a strong correlation between εr' and porosity; the εr' values decreased 2.3-fold over a porosity range of 3–15%. The proposed regression models can be further used in determining the porosity of FAGPBs at a high accuracy level.

A Novel Proximity Sensor Based on Parallel Plate Capacitance

The proximity sensor plays an important role in recognition, positioning, tracking, and avoiding of obstacles in robot movement. The existing proximity sensors cannot identify the direction and measure the distance of the approaching object simultaneously. In order to solve mentioned problem, this paper presents a novel proximity sensor based on parallel plate capacitance. The proposed proximity sensor adopts the structure wherein driving electrode and sensing electrodes are located on the same plane. The number of driving electrodes differs from the number of sensing electrodes, and sensing electrodes are symmetrically distributed around the driving electrode. In this paper, we developed the circuit model of the proximity sensor based on parallel plate capacitance, and analyzed the influence of the guard ring on sensor sensitivity. We also designed a new sensor structure, which employs four sensing electrodes to identify direction of the approaching object. In addition, the proximity sensor performances in terms of direction identification were verified by experiments, and both sensing errors and sensor repeatability were calculated. The experimental results have shown that proposed proximity sensor can distinguish four different directions and measure the object distance in the range of 1 ~ 40 mm simultaneously. The sensing errors were less than 5% and the repeatability error was 1.05%.

Monitoring electromagnetic fields and safe operation levels in electrical power transmission lines

Electrical power systems and their elements such as power transformers, transmission lines, capacitors, reactors and other elements, during normal operation generates electromagnetic fields that changes according with design, equipment distribution, current and voltage operation levels. This paper describes the monitoring electromagnetic fields and safe operation levels in electrical power transmission and distribution lines during the last five years in power lines located in warm climate with high salinity, corrosion and pollution level. A literature review was considered during the study. This paper characterizes power lines in order to guarantee safe operation to occupational exposure and general public since planning process. Results will be used in order to characterize power lines and will be used as a tool for utilities with the aim to reduce legal penalties and promote social responsibility. Results also were contrasted with International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommendations with the reference levels for occupational exposure to time-varying electric and magnetic fields. Results provide recommendations for electrical grid utilities also the study compare real values with simulated values in order to guarantee an acceptable approach according with ICNIRP and international standards recommendations.

GWO Based Optimal Reactive Power Coordination of DFIG, ULTC and Capacitors

<p>Wind is available with free of cost anywhere in the world, this wind can be used for power generation due to many advantages. This attracts the researchers to work on wind power plants. The presence of wind power plants on distribution system causes major influence on voltage controlled devices (VCDs) in terms of life of the devices. Therefore, this paper proposes grey wolf optimization method (GWO) together with forecasted load one day in advance. VCDs are on load tap changer (ULTC) and capacitors (CS), there are two main objectives first one is curtail of distribution network (DN) loss and second one is curtailing of ULTC and CS switching’s. Objectives are achieved by controlling the reactive power of DFIG in coordination with VCDs. The proposed method is planned and applied in Matlab/Simulink on 10KV practical system with DFIG located at different locations. To validate the efficacy of GWO, results are compared with conventional and dynamic programming methods without profane grid circumstances.</p>

Toward an Improved Understanding of the Role of Dielectrics in Capacitors.

A new fundamental principle of the theory of dielectrics in capacitors is demonstrated. That is, dielectric material in any geometry that reduces the field generated by charges on capacitor electrodes is effective in increasing capacitance. Specifically, it is shown that super dielectric material on the outer surfaces of the electrodes of a parallel plate capacitor increases dielectric constant, as well as energy and power densities, by orders of magnitude. The implicit assumption in all current capacitor theory, that the “capacitor” is only that region occupied by the electrodes and the space between them, is shown to be incorrect.

A Highly Sensitive Capacitive-type Strain Sensor Using Wrinkled Ultrathin Gold Films.

Soft strain sensors are needed for a variety of applications including human motion and health monitoring, soft robotics, and human/machine interactions. Capacitive-type strain sensors are excellent candidates for practical applications due to their great linearity and low hysteresis; however, a big limitation of this sensor is its inherent property of low sensitivity when it comes to detecting various levels of applied strain. This limitation is due to the structural properties of the parallel plate capacitor structure during applied stretching operations. According to this model, at best the maximum gauge factor (sensitivity) that can be achieved is 1. Here, we report the highest gauge factor ever achieved in capacitive-type strain sensors utilizing an ultrathin wrinkled gold film electrode. Our strain sensor achieved a gauge factor slightly above 3 and exhibited high linearity with negligible hysteresis over a maximum applied strain of 140%. We further demonstrated this highly sensitive strain sensor in a wearable application. This work opens up the possibility of engineering even higher sensitivity in capacitive-type strain sensors for practical and reliable wearable applications.

A portable and low-cost parallel-plate capacitor sensor for alkali and heavy metal ions detection

A portable and low-cost design of parallel-plate capacitor sensor is proposed and investigated for detection of heavy and alkali metal ions concentration in liquid solution. The application of a thin and long-sided parallel PCB plate allows one to measure the dielectric response of each sample through capacitive sensing technique. The measurements were based on the peak output voltage corresponding to the capacitance of the output measured by an oscilloscope with metal ions concentration of the solution varying from 0 to 10[Formula: see text]ppm and input frequency ranging from 1[Formula: see text]kHz to 10[Formula: see text]MHz. The ICF of Li, Na and K in chloride solution was 2.4, 2.1 and 1.9[Formula: see text]MHz, respectively. The ICF of Na and K in hydroxide solution was 1.5[Formula: see text]MHz and 1.1[Formula: see text]MHz, respectively, while the ICF of Pb(NO[Formula: see text] was 490[Formula: see text]kHz. The detected ICF was applied to further construct the portable sensor system, which is simple in design, low-cost in fabrication and easy to operate. The finding of ICF of each chemical element is necessary to solve the selectivity challenge of the capacitance-based sensor, which will be appropriate for chemical, environmental and engineering applications.

Direct Demonstration of Unified Brønsted−Evans−Polanyi Relationships for Proton-Coupled Electron Transfer Reactions on Transition Metal Surfaces

The existence of Brønsted-Evans-Polanyi (BEP) relationships, which relate elementary reaction barriers to reaction thermodynamics across a space of different catalysts, has been extensively investigated for reactions on traditional heterogeneous catalysts, and BEP’s are known to provide the central physical paradigm underlying the existence of volcano plots and other trends-based descriptions of catalytic reactivity. However, the extension of such relationships to elementary electrochemical reactions, simultaneously spanning a space of both different applied voltages and different catalyst surfaces, has been widely discussed but never verified. In this contribution, the BEP model is explicitly shown to describe both multiple catalyst surfaces and variable voltages in electrochemical environments. For proton-coupled electron transfer to surface nitrogen (N*) and nitric oxide (NO*), reaction energies and activation barriers are calculated using density functional theory on a parallel plate capacitor model at three different potentials and for nine different transition metal surfaces. Linear BEP relations that describe all potentials and catalyst surfaces are obtained for these elementary reactions, and the slopes of the correlations are shown to be directly related to the fractional coordinate of the transition states (FCTS) of the reactions. The results, which are explained in terms of Marcus Theory, prove a direct equivalence between unified BEP coefficients, describing both variable catalyst surfaces and voltages, and electrochemical symmetry factors and provide a straightforward means of estimating this quantify for proton-coupled electron transfer reactions on transition metal surfaces. The resulting relationships, in turn, could lead to predictions of electrocatalytic reactivity trends of enhanced accuracy and efficiency.

Relaxation Processes at Interfaces in Polymer Nanocomposites

Polymer nanocomposites (PNC) where nanofillers such as nanoparticles and nanotubes are dispersed show better mechanical, electric and dielectric properties in comparison with the neat polymer matrix. The improvement of the properties is strongly dependent on the formation of interfacial regions between fillers and matrix polymer chains. A core-shell model [1], in which each nanofiller (core) is supposed to be covered with an interfacial polymer layer (shell) with slower dynamics than the bulk one, has been widely used to rationalize the property improvement. When the nanofiller fraction increases above a percolation threshold, the presence of nanofiller network can lead to the formation of interfacial regions with hierarchical dynamics. A quantitative understanding of the hierarchical nature in the relaxation dynamics of interfacial chains is critical for tailoring multiple properties of PNCs. In this study, the relaxation dynamics of a model rubber nanocomposite, nitrile-butadiene rubber (NBR) with silica (SiO2) nanoparticles, was characterized over broad temperature and frequency ranges by means of dielectric relaxation spectroscopy (DRS). As samples, NBR with a number-average molecular weight of 81.9k, a polydispersity index of 3.56 and a glass transition temperature (T g) of 242 K, and SiO2 nanoparticles with an average diameter of 18 nm, and their composites were kindly provided by Bridgestone Co., Ltd.. The weight content of acrylonitrile component in NBR was 34%, and the volume fraction of SiO2 nanoparticle in PNC (Φ) was varied from ~5 to ~30%. For DRS measurements, neat NBR and PNC films were prepared by a spin-coating method from tetrahydrofuran solutions onto quartz substrates coated with a 50 nm-thick Al layer. The films were dried in vacuum for 24 h at room temperature, and then a second 50 nm-thick Al layer was deposited on the surface of each film to form a parallel-plate capacitor. DRS measurements were conducted using a frequency response analyzer over the range from 10-1 to 106 Hz. Panels (a) and (b) of Figure 1 show representative examples of SEM images for PNC samples with Φ = 7 and 17 vol%, respectively. For the PNC sample with Φ = 7 vol%, SiO2 agglomerates with different sizes were distributed in the NBR matrix without the formation of long-range particle-particle structured network. In contrast, at Φ = 17 vol%, the SiO2 agglomerates tended to connect each other to form a long-range particle-particle network. This behavior has been experimentally confirmed in many nanocomposite systems. However, for a moment, it remains challenging to discuss a relationship between the particle-particle network and the relaxation dynamics of interfacial polymers. Panel (c) of Figure 1 shows dielectric loss (ε″) spectra for the neat NBR and PNCs as a function of frequency measured at 262 K. A strong peak representing the segmental relaxation process of NBR chains was observed around 5×102 Hz for each sample [2]. However, comparing with the neat NBR, the peak for the PNCs exhibited a decrease in amplitude and broadening on the low-frequency side. This trend became more remarkable for samples with higher Φ. This suggests the existence of a second relaxation process which represents the relaxation dynamics of the polymer shell layer surrounding SiO2 nanoparticle surface [1]. The ε′′ data for the neat NBR could be well fit using a Havriliak-Negami (HN) function with a single relaxation process [2]. However, a HN function with double relaxation processes and a conductivity term were necessary to well express the ε′′ data for the NBR-SiO2 films. The relaxation process of the shell layer was found to be slower than that of the bulk process by approximately two decades and almost independent of Φ. Panel (d) of Figure 1 shows temperature dependence of ε″. For all samples, a peak assignable to the segmental relaxation process was observed around 262 K. For the PNC films with Φ = 17 and 29 vol%, an additional peak was observed at a temperature higher than that for the bulk segmental relaxation peak by 50 ~ 80 K. The temperature elevation was more remarkable for the PNC sample with Φ = 29 vol%. Although the origin of this relaxation process can be hardly concluded, it seems reasonable to consider that it is arisen from slowed dynamics for chains restricted on the surface of SiO2 nanoparticles. [1] S. Cheng, S. Mirigian, J.-M. Y. Carrillo, V. Bocharova, B. G. Sumpter, K. S. Schweizer, and A. P. Sokolov, J. Chem. Phys. 143, 194704 (2015). [2] H. K. Nguyen, A. Konomi, S. Sugimoto, M. Inutsuka, D. Kawaguchi, and K. Tanaka, Macromol. Chem. Phys. 219, 1700329 (2018). Figure 1

Analysis of metallic hemispherical shell vibration modes for coriolis vibratory gyroscope

Gyroscope is an instrument widely used in the navigation systems for sensing inertial angular motion. One of the principle of Gyroscope is Coriolis Vibrating Gyroscope (CVG), which is simple and easy to operate. It is realized during the development of the CVG that it is most suitable inertial sensor for aerospace applications. In this paper, a novel method for high reliable gyroscope application is demonstrated to verify the ‘Mode 2’ vibration pattern of vibrating hemispherical metallic shell. A parallel plate capacitor arrangement is made by placing discrete metallic plates around the metallic shell to study the vibration mode pattern. The shell vibrating at this particular mode, flexes along the axial direction of capacitor. The air gap of the parallel plate capacitor changes as the shell vibrates. The ‘Mode 2’ vibration pattern from the shell is confirmed by studying the phase relation at different capacitor locations.

Exploring Mesh Generation and Quality Enhancement with Open Source Codes

The finite element method is a very reliable and precise technique for solving partial differential equations in three-dimensional domains, with relevant applications in several areas. However, 3D simulations by FEM require computer programs for solid modeling and automatic mesh generation and there are few examples of open source codes available and dedicated to these tasks. Unfortunately, these open source codes are not usually conceived to operate together in an integrated fashion, showing distinct life cycles and different origins, which may result in contradictory specifications. In this study, a method is proposed to integrate solid modeling and automatic mesh generation with focus on open source codes and how the quality of FEM simulations can be improved by the improvement of the mesh. The method was structured in desired features for the solid construction and in integration strategies for an automatic mesh generation. The approach was tested in nontrivial domains and with known relevance for studies focused on computational electromagnetics. Meshes were generated with millions of tetrahedral elements and the results were compared to the quality values commonly discussed in literature focused on FEM. Complex geometries were meshed in a few seconds, with consistent values of aspect ratios (more than 90% of the tetrahedral elements were constructed with values at most 5) and dihedral angles (the values were bounded between 5.9 to 166.7°C, with a peak value around 90°C). Finally, in order to show the relation among highly refined meshes and quality criteria which can be explored by proposed method, the Laplace's equation was simulated by FEM in order to analyze the equipotential lines of a parallel-plate capacitor. The results show how the quality of a simulation can be improved, especially concerning the increasing number of tetrahedra in the mesh with proper aspect ratio.

Predicting SMPS's remaining life using ripple ratio of electrolyte capacitor

Our objective is predicting electrolyte capacitor's lifetime at operating situation using ripple ratio. Most electrical products have SMPS(Switched mode power supply) and SMPS's life is mostly dependent on electrolyte capacitor's life. Our research can help predicting SMPS's lifetime and establishing maintenance plan of SMPS.

Equivalent capacitive thickness of the vapor layer below Leidenfrost drops

For the first time, a capacitive method is reported to provide information about the thickness of the vapor layer below Leidenfrost drops. Contrarily to the other available techniques, the present approach is fast and simple which allows a continuous monitoring of the thickness over time. The electrostatic system can be represented by a parallel-plate capacitor. The heated substrate and the conductive liquid water are the plates of the capacitor while the insulating vapor constitutes the dielectric layer. The concept of equivalent capacitive thickness (hcapacitance) is introduced using electrostatic calculations taking into account the real shape of the drops. Experimentally, hcapacitance has been obtained from the simultaneous measurement of the drop radius and the capacitance. The temporal evolution of hcapacitance has been evaluated for various initial drop volumes. For all the drop volumes, a linear diminution with time is obtained. The results evidence that the major parameter that controls the value of hcapacitance is the instantaneous drop volume. The comparison between hcapacitance and the thicknesses obtained by laser diffraction and literature data reveals that the value of the thicknesses seems to depend on the measurement method. In fact, the thickness is variable from the center to the edge of the drop and each method is more or less sensitive to different positions. At the same time, hcapacitance remains larger than the resulting thickness using light diffraction and is included between the thicknesses at the center (hcenter) and at the neck (hneck) of the drop.

FEM and experimental studies of flexible pressure sensors with micro-structured dielectric layers

E-skin (electronic skin) is a key component for use ranging from wearable electronic devices to human-machine interactions. Previous studies proposed that a parallel plate capacitor with a PDMS dielectric layer of micro-pyramids showed good pressure sensing abilities, but overlooked effects of the flat PDMS layers at the top and bottom of these microstructures induced by fabrication processes of soft imprinting. In this work, these effects were firstly studied by the finite element method. The second-order Ogden model was employed to describe the nonlinear mechanical behaviors of the PDMS. We found that the E-skin sensing unit showed increased sensitivity but decreased linearity with the increase of the pyramid height ratio. 48% pyramid height ratio was therefore applied for experimental studies for compromising the performances. We demonstrated an easy accessible and cost-effective method of fabricating the sensing unit, by using a commercial precision abrasive sheet as the mold of the microstructured dielectric film. We introduced a prefilling step to control the pyramid height ratio. Experimental results proved that the sensitivity, pressure resolution and time response of the sensor unit with pyramid height ratio of 45% were better than that with 0. We further demonstrated its applications as a wearable health monitoring device and an approaching and touch sensing unit for a 3D-printed soft hand, showing its great potentials in continuous health monitoring sensors, as well as large area human-machine interactions.

Potential of two dielectric spectroscopy techniques and chemometric analyses for detection of adulteration in grape syrup

Food adulteration is a widespread illegitimate procedure involving contamination of food with chemical and physical substances. The adulterated food products are not only of decreased quality but also may cause pathogenic effects that jeopardize the human health. Adulteration of liquid foods is majorly performed for economic gains by utilizing cheap adulterants which do not necessarily change the color, taste and appearance of the food to be easily detectable by human senses. In the present study, two different dielectric spectroscopy sensors (parallel plate capacitor (PPC) and cylindrical stub resonator (CSR)) were examined and compared for detection of adulteration in grape syrup. The aim was to address which sensor could be a more precise instrument for detecting the type and level of a variety of common adulterants in grape syrup. The different adulterants tested were the date syrup, grape paste and sugar-water solution mixed at 5, 10, 15, 20, 25 and 30% with pure grape syrup. The multivariate dielectric spectral data were visualized with principal component analysis (PCA). Furthermore, similarity between different adulterants and their levels was identified with the hierarchal cluster analysis (HCA). To perform classification analysis, two different classification techniques i.e., linear discriminant analysis (LDA) and multi-class support vector machines (SVM) were utilized and compared. The results showed that PCA provided clear visualization identifying different types of adulterants over the score plots. Classification of adulteration type using SVM and LDA resulted in 100% accuracy for either of the sensors. For classifying the level of adulteration, PPC sensor associated with SVM classifier resulted in the highest accuracy (100%). In conclusion, the adulteration detection in grape syrup was satisfactorily addressed by the dielectric spectroscopy techniques. As diagnosistic tools, both the instruments could be implemented with standards executed for food security assessments.

A Continuous Semi-Empirical VJFET Capacitance Model from Sub to above Threshold Regime

This paper presents and discusses the depletion mechanisms that dominate in a TSI-VJFET under different bias conditions as expressed by the gate-source (CGS) and gate-drain (CGD) capacitances. It is shown that at pinch off the dominant capacitance is the drift capacitance and that in conduction the drain source voltage plays a significant role in channel’s formation. Furthermore a semi empirical capacitance model is introduced. CGS and CGD are modeled below and above threshold voltage by considering parallel plate capacitors with different plate configuration in te two cases. Then, the derived expressions are unified using a transition function that preserves the continuity of the model. The model was adjusted and fitted adequately to measured CV data from fabricated TSI-VJFET.

An overview of high-k oxides on hydrogenated-diamond for metal-oxide-semiconductor capacitors and field-effect transistors

An overview of high-k oxides on hydrogenated-diamond for metal-oxide-semiconductor capacitors and field-effect transistors

A light weight and broadband metamaterial absorber with 3D cube unit cells

Metamaterial absorber (MA) with lossless spacing substrate is accompanied by total reflection which is a defect for the broadband design. In this paper, a theoretical transmission-line study of the total reflection is presented to introduce a 3D structural solution: a MA with polyurethane foam inserted by lateral resistive sheets and sandwiched between surface-resistive sheets and grounded aluminum foil. By virtue of the effective parallel plate capacitors formed between the neighboring square-resistive sheets which are perpendicular to the incident electric field, electromagnetic loss is generated from the charges accumulate and ohmic loss on them. As a result, the original total reflection (at f = 10 GHz) can be eliminated and a broadband absorption (from 2.88 to 18 GHz) with absorbance more than 90% is obtained for the proposed light weight (5.64 × 10−5 g/mm3) 3D MA. The measurement result has a good agreement with simulation. This design opens up opportunities for the absorption bandwidth enhancement of MA and can be extended to infrared or optical region.

Superconducting membrane mechanical oscillator based on vacuum-gap capacitor**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0301801), the National Natural Science Foundation of China (Grant Nos. 11474154 and 61521001), and the Priority Academic Development Program of Jiangsu Higher Education Institutions and Dengfeng Project B of Nanjing University, China.

Using the diluted S1813 UV photoresist as a sacrificial layer, we successfully fabricate a superconducting suspended parallel-plate capacitor, in which the top layer of aluminum film acts as a membrane mechanical resonator. Together with a superconducting octagonal spiral inductor, this parallel-plate capacitor constitutes a superconducting microwave resonator. At mK temperature, the transmission characteristic and spectrum of the microwave resonator are measured. Sideband frequencies caused by the vibration of the membrane mechanical resonator are clearly demonstrated. By down-converting with a mixer, the dependence of fundamental frequency and its harmonics on the input microwave power are clearly demonstrated, which is consistent with the numerical simulation.

Using the Cycloid as an Introduction to Transformations of E and B Fields

The transformations of electric and magnetic fields are usually introduced by viewing systems such as a long, straight current-carrying wire and a parallel plate capacitor in two different reference frames. These well-known examples show that magnetism is a necessary consequence of augmenting electrostatics with relativity. Because they require the full apparatus of Lorentz contraction and Lorentz transformation of forces, they are often postponed until the upper-division undergraduate electrodynamics course.