Capacitive Reactance Research Articles

A pilot study to evaluate Australian predictive equations for the impulse oscillometry system

Impulse oscillometry (IOS) measures respiratory function during normal breathing by transmitting mixed frequency rectangular pressure impulses down the airways and measuring the resultant pressure and flow relationships, which describe the mechanical parameters of the lungs. Respiratory impedance and its components, airways resistance and reactance, at a range of frequencies from 0.1 to 150 Hz are calculated by computer analysis. The IOS software generates predictive normal values for each of the parameters measured, including total airway resistance (R5), proximal airway resistance (R20) and peripheral capacitive reactance (X5). However, these values are based on German data and no other Caucasian data or Australian normative data exist. This was a cross-sectional study of over 100 community dwelling adults, with about 10 men and 10 women per 10-year cohort. Inclusion criteria were age between 25 and 74 years and apparently good respiratory health. Exclusion criteria were smoking, asthma and acute or chronic respiratory disease. IOS and spirometry were performed on all participants. Australian predictive normal equations were generated and compared with current published equations. The IOS parameters were correlated with the spirometric data. Results were analysed by gender, age, height and weight, and compared with the predicted normal values for each parameter provided by the German manufacturer of the IOS instrument. A preliminary set of Australian predictive equations have been produced for the IOS. These have been compared with international equations. IOS has potential applications in a range of respiratory diseases and in population screening for occupational health assessment.

Background voltage distortion influence on power electric systems in the presence of the Steinmetz circuit

In traction systems, it is usual to connect reactances in delta configuration with single-phase loads to reduce voltage unbalances and avoid electric system operation problems. This set is known as Steinmetz circuit. Parallel and series resonances can occur due to the capacitive reactance of the Steinmetz circuit and affect power quality. In this paper, the series resonance “observed” from the supply system is numerically located. The study of this resonance is important to avoid problems due to background voltage distortion. Experimental measurements are also presented to validate the obtained numerical results.

SIMULTANEOUS MEASUREMENTS OF THE RESISTANCE AND CAPACITANCE USING A CYLINDRICAL SENSOR SYSTEM

In this article, the design and operation of a cylindrical capacitive sensor based on the dielectric reactance capacitance and conductance changes of the gap medium is reported. The proposed system was used to determine characteristics of different water liquids as a result of the capacitance and resistance variations. The air gap capacitance (dry signal) is measured and then by filling the gap with a liquid, the capacitance (wet signal) is monitored for different liquids. A reported sensor is used for the distilled, tap, boiled, and salt water measurements and the capacitance and resistance results are compared. A big difference of about 38.5 μF in the measured capacitance values for the salt and distilled water shows a high sensitivity, which can be used to recognize different water liquids. The experimental results are promising for water liquids and verify the successful operation of such a device as a liquid sensor, a useful method for checking the electrical quality of the water that is required for different applications. It is also possible to monitor the resistance change of the filling medium as a function of time.

P‐80: External Electrode Fluorescent Lamps and Backlight Units for the Large Area of 32″∼42″ LCD‐TVs

AbstractThe commercialized EEFL‐BLUs of 32″, 37″, and 42″ LCD‐TVs are reported with respect to the basic characteristics of luminance and efficiency. The capacitive and resistive reactance is also presented to design the inverter for lamps and BLUs.

Influence of the Steinmetz Circuit Capacitor Failure on the Electric System Harmonic Response

Traction systems are generally single-phase loads that can cause voltage unbalances which affect the electric system operation. It is usual to delta-connect reactances with these single-phase loads to reduce voltage unbalances. The set of reactances and single-phase loads is known as a Steinmetz circuit. A parallel resonance can be produced between the capacitive reactance of the Steinmetz circuit and the system inductive reactances, which can damage power quality. This paper locates the frequency of this parallel resonance analytically and studies the influence of capacitor loss with respect to its design value. Experimental measurements are also presented to validate the obtained analytical results

Indirect Adaptive External Neuro-Control for a Series Capacitive Reactance Compensator Based on a Voltage Source PWM Converter in Damping Power Oscillations

A series capacitive reactance compensator (SCRC), using a voltage source converter to inject a controllable voltage in quadrature with the line current of a power network, is capable of rapidly providing a specified and controllable magnitude of capacitive reactance compensation independent of the line current. Moreover, with a suitably designed external controller, the SCRC can also be used to damp low-frequency power oscillations in a power network. Conventionally, linear control techniques are used to design the SCRC external controller around a specific operating point, where the nonlinear system equations are linearized. However, at other operating points its performance degrades. Nonlinear adaptive neuro-controllers offer an attractive approach to overcome this degradation problem. In this paper, an indirect adaptive external neuro-controller (INDAEC) using two radial basis function neural networks (RBFNNs) is proposed to improve the damping performance of an SCRC connected to a power network. This nonlinear INDAEC needs no mathematical model of the SCRC or the power network. It provides the SCRC with improved damping performance over a wide range of system operating conditions. This is shown by results on a single machine infinite bus power system, as well as a multimachine power system

Formation of nanogaps by nanoscale Cu electrodeposition and dissolution

We utilize an ac feedback signal to control the size of Cu nanogaps by electrochemically depositing or dissolving copper onto pre-patterned electrodes. The ac frequency in this work was set to 820 Hz, at which the capacitive reactance contributes notably to the gap impedance. As a result, distinct changes can be observed in the monitored signals at relatively large gap size, as compared with the high sensitivity of resistive reactance to small gap distance when the frequency is set lower. Within the present parameter, we have prepared nanoscale gaps ranging from tens of nm to sub-10 nm by carefully choosing the subsequent deposition or dissolution time.

Capacitive VAr requirements for wind driven self-excited induction generators

Abstract This paper presents the capacitive VAr requirements of a three phase pole changing self-excited induction generator and a single phase self-excited induction generator, used as isolated power sources by a constant speed or a variable speed prime mover, to obtain the desired voltage regulation at various values of load and speed. Different performance criteria such as constant terminal voltage or constant air gap flux have been considered. The developed mathematical model using nodal analysis based on graph theory is quite general in nature and can be used for any combination of the unknown variables such as magnetizing reactance (XM) and frequency (F) or capacitive reactance (XC) and frequency (F) or capacitive reactance (XC) and speed (υ). The proposed model completely avoids the tedious and erroneous manual work of segregating the real and imaginary components of the complex impedance of the machine for deriving the specific model for each operating modes. Moreover, any element, like the core loss component, can be included or excluded from the model if required. Next, to obtain the capacitive VAr requirements of a three phase pole changing self-excited induction generator and a single phase self-excited induction generator, a fuzzy logic approach is used for the first time to find the unknown variables using the above model. The results are presented in a normalized form so that they are valid for a wide range of machines and would be useful for the design of voltage regulators for such generators.

Preparation and Electrical Properties of (Ca, Mn)-codoped Ba1xSrxTiO3 Solid Solution

(Ca, Mn)-codoped Ba1xSrxTiO3 (BST) solid solution, i.e. Ba0.4Sr0.5Ca0.08Mn0.02TiO3, was successfully synthesized via sol-gel process. The product was characterized by TG-DTA thermal analyses, XRD, TEM. The effects of both curing temperature and applied voltage on the resistance, etc. were investigated. It showed that the structure of BST was unable to be changed even though it was codoped by Ca2+ and Mn2+. TEM photographs demonstrated the influence of curing temperature on the morphologies of the tested samples. The dependence of resistance on the curing temperature illustrated that (Ca, Mn)-codoped BST was capable of exhibiting the positive temperature coefficient (PTC) effect at low frequency; nevertheless, it might display the negative temperature coefficient (NTC) effect at other frequencies. The relationships between the resistance and applied voltage revealed that the resistance property of (Ca, Mn)-codoped BST appeared at low frequencies, but its property of capacitive reactance might present at high frequency. These findings mean that the electrical property of BST can be adjusted by codoping method. These phenomena can be explained by the grain boundary resistance effect, Heywang model and ion polarization theory.

Study of the power system harmonic response in the presence of the Steinmetz circuit

The Steinmetz circuit is constituted by single-phase loads, e.g. traction systems, delta-connected with reactances to load the network with balanced currents. A parallel resonance between the capacitive reactance of the Steinmetz circuit and the power system reactances can be produced, and therefore harmonic voltage distortion in the presence of non-linear loads increases. The paper studies this resonance analytically and presents an expression to locate it. Experimental measurements have also been made to validate the obtained analytical results.

Modelo experimental de icterícia obstrutiva: avaliação por meio da bioimpedância

OBJETIVO: A bioimpedância é um método utilizado, como medida de massa corporal, volume líquido e volume de gordura corporal. Os autores analisam a utilização e desempenho da impedância em modelo de pesquisa experimental de icterícia obstrutiva. MÉTODO: Utilizaram-se oito ratos da linhagem Wistar, que foram divididos em dois grupos de quatro animais: grupo 1(experimento) e grupo 2 (controle). No grupo 1 foi realizado ligadura do colédoco e no grupo 2 laparotomia. Realizou-se a mensuração da resistência e da reatância capacitiva com aparelho de análise de bioimpedância no pré e pós-operatórios. RESULTADOS: O estudo revelou valores médios de resistência para o grupo controle maiores do que para o experimento, mostrando uma diferença significante. Também os valores de reatância capacitiva apresentaram médias maiores no grupo controle com p<0,0001. CONCLUSÕES: A análise dos resultados permite concluir que no rato: há diferenças nos valores de impedância entre os animais do grupo controle e experimental; os valores médios de resistência e reatância capacitiva são menores no grupo experimento e que a aplicabilidade da impedância no presente modelo pode ser sugerida.

Montelukast improves pulmonary function measured by impulse oscillometry in children with asthma (Mio study)

Systemic drugs-like oral montelukast can reach lower airways, whose inflammation plays a crucial role in the evolution of asthma, while inhaled drugs hardly reach them. The impulse oscillometry (IOS) technique is useful to evaluate both central and peripheral airways function. To measure the effect of oral montelukast on airways resistance evaluated by oscillometry in children with asthma. In an open study, respiratory function in 23 children with mild asthma and a positive bronchodilator response was assessed by spirometry and oscillometry. They took oral montelukast during 4 weeks and were again evaluated. As a control group, 23 similar patients with no preventive treatment underwent the same study. Children on oral montelukast showed improvements (measured in kPa s L(-1)) in all oscillometry parameters: mean 0.20 (22.4%) in total respiratory impedance Zrs5, 0.18 (21.8%) in total airway resistance Rrs5, 0.09 (17.8%) in central airway resistance Rrs20, and 0.09 (28.8%) in distal capacitive reactance Xrs5; the frequency of resonance Fres improved 2.3 Hz (8.7%) (P<0.05 in all cases). No changes were found in the control group. Expiratory flows showed no changes except for a small (0.23 L s(-1), 7.4%) but significant worsening of FEF25-75 in the control group. Montelukast improves central and especially peripheral airways function in the first month of treatment, as evaluated by IOS, a technique based on tidal breathing analysis which is more sensitive than conventional forced spirometry.

PSSC Turbo Ring Flinger

This is a description of an inexpensive version of the Thompson's jumping ring demonstration apparatus, which provides for a spectacular demonstration of Lenz's law. The device has the additional capability of being used to demonstrate the opposing nature of inductive and capacitive reactance.

Analysis of EIS characteristics of CO 2 corrosion of well tube steels with corrosion scales

The electrochemical impedance spectroscopy (EIS) was used to study the characteristics of CO 2 corrosion of N80 and 4Cr steels with corrosion scales. The results indicated that CO 2 corrosion scale on tube steel could prevent the rate of mass transfer remarkably, corrosion rate was controlled by ions diffusion in corrosion scale, which led to finite length diffusion impedance occurred in electrochemical impedance spectra. Additionally, pitting of N80 steel could lead to additional capacitive reactance in impedance spectrum. The ion diffusion coefficient in corrosion scale and porosity of corrosion scale could be calculated by Warburg impedance coefficient, the results shown that the value of H + diffusion coefficient in N80 and 4Cr corrosion scale is (3.46 and 1.76) × 10 −10 m 2 s −1, respectively. The protective ability of 4Cr corrosion scale was better than that of N80 corrosion scale.

Investigation on EM Wave Absorbers by Using Resistive Film with Capacitive Reactance

It is known that the thickness of the λ/4 type EM wave absorber having a resistive film with the capacitive reactance is thinner than 1/4 wavelength. This paper investigates EM wave absorbers using the resistive film with capacitive reactance. We introduced the impedance into the resistive film, and then clarified the relationship between the impedance and the matching thickness in the single layer EM wave absorber. Practically, we carried out to grasp the impedance of the resistive films, which were prepared using the conductive flake powder. As the results, we have proven that the matching thickness in the single layer EM wave absorber could be realized 0.17 λ - 0.09 λ in the frequency range from 2 GHz to 8 GHz by using these resistive films. We also fabricated the single resistive layer and the double resistive layers EM wave absorber using these resistive films for Dedicated Short Range Communications (DSRC) and wireless Local Area Network (LAN), in which the matching thickness could be reduced to 45% and 30%, respectively, as compared with the each absorber using the non-capacitive reactance.

Importance of Proton Conductivity Measurement in Polymer Electrolyte Membrane for Fuel Cell Application

The precise impedance measurement system based on the well-known two-probe and four-probe methods was prepared to measure the impedance and consequent proton conductivity of Nafion membranes as standard samples, considering not only the number of electrodes and the bridging methods but also the elimination of electrical error sources for the precise electrical analysis. The proton conductivities of Nafion membranes are reported and discussed in the present study with respect to different cell configurations and measurement conditions. The values of proton conductivities measured using the four-probe method were always higher (2−5 times) than those measured using the two-probe method at ambient humidity and temperature. The proton conductivities were also measured under two different humidity conditions: water-vapor state and liquid-water state. In the water-vapor state (95% relative humidity), completely different impedance behaviors for the identical Nafion membrane were observed from the Nyquist impedance plots. All Nyquist plots derived from the two-probe method represented the inductive reactance derived from various components, such as Pt electrodes, electric conductive leads, and a potentiometer in the path of current flow rather than the capacitive reactance between Pt electrodes. The effect of contact resistance between the membrane sample and electrodes on proton conductivity was also investigated by using the two conductivity-cell configurations. It was shown that the effect of the contact resistance on the proton conductivity was more severe in the two-probe measurement, and this factor should be seriously considered in the water-vapor state. Furthermore, the humidity and the temperature effects on the proton conductivity of the membranes were observed under various measuring conditions and compared with the two different cell configurations. The four-probe method well reflected the proton conductivity behavior of Nafion membrane in the wide range of temperature and humidity, as compared with the two-probe method with reasonable proton conductivity in the low humidity.

Effect of reactor configuration on nitric oxide conversion in nitrogen plasma

AbstractThe configuration of a nonthermal plasma reactor strongly affects the rate of electron collision reactions. Experiments involving the decomposition of NO in N2 were performed in a reactor in which the number of parallel reactor tubes varied from 1 to 10 at a constant pressure of 147.6 kPa and ambient temperature. A previously developed lumped model of the reactions accurately predicted the effects of varying the initial concentrations of NO (from 240 ppm to 593 ppm) and gas residence time (from 1.93 to 7.42 s). With an increasing number of parallel reactor tubes, the rate of electron collision reactions decreases because the energy input per unit reactor volume at unit time decreases, while the energy consumption per molecule of NO converted to N2 and O2 decreases due to electrical and geometric effects associated with the decreasing peak width of the discharge voltage pulses and increasing reactor capacitance. Therefore, increasing the number of parallel reactor tubes provides a viable scale‐up method for constructing more efficient pulsed corona discharge reactors. © 2005 American Institute of Chemical Engineers AIChE J, 2005

A Novel Approach to Classify Risk in Dengue Hemorrhagic Fever (DHF) Using Bioelectrical Impedance Analysis (BIA)

This paper introduces a novel approach to classify the risk in dengue hemorrhagic fever (DHF) patients using the bioelectrical impedance analysis (BIA) technique. This in vivo technique involves the application of a small average constant current of less than 1 mA at a single frequency of 50 kHz through the human body, and measurement of the body's bioelectrical resistance (R), phase angle (/spl alpha/), body capacitance (BC) and capacitive reactance (X/sub c/) via four surface electrodes. BIA measurements have been conducted on 184 (97 males and 87 females) serological confirmed dengue patients during their hospitalization in University Kebangsaan Malaysia Hospital, Malaysia. The patients included in the study were DHF I-IV according to World Health Organization criteria. Univariate analysis of variance is used for assessing the relationship between gender and group with the bioelectrical tissue conductivity (BETC) parameters. Experimental findings show that BETC, as reflected by reactance, is the key determinant indicator for classifying risk category in the DHF patients. Hence, this novel approach of the BIA technique can provide a rapid, noninvasive, and promising method for classifying and evaluating the risk of the DHF patients.

Series compensation of radial power system by a combination of SSSC and dielectric capacitors

This paper shows that the addition of dielectric capacitors lowers the cost of series compensation by static synchronous series compensator (SSSC). Normally the capacitor resonates with the line inductance and the L-C electrical resonance can interact with the torsional resonances of the multiple-inertia elastic shaft of steam turbine-generators to give rise to subsynchronous resonance (SSR) instability. The SSSC has two functions: (1) to provide some series capacitive reactance compensation; (2) to damp out incipient unstable SSR modes. Digital simulation using HYPERSIM shows that for an overall degree of capacitive compensation of 0.7 pu, the SSSC component is only about 1/3 of the capacitive Mvar. Based on the transient stability limit, the transmissibility of the line is increased by a factor of 2.23.

A Method for Improving the Matched Termination of Microstrip Line in FDTD Calculation

When characteristics of microstrip line components are calculated by the FDTD method, a non-reflecting termination of the microstrip line is desired. In this paper, a novel method for making a termination producing a small reflection is proposed. The matched termination is composed of lumped-circuit elements. The frequency range of the analysis is up to 10 GHz. The reflection level of a resistance termination previously proposed increases in the high frequency region. The impedance calculated from the reflection coefficient in the termination shows that the cause of the increase is floating capacitance at the end of the microstrip line. And the other cause is the frequency dispersive characteristic impedance of microstrip line. In order to reduce the effect of the capacitive reactance and the difference between the terminal impedance and the characteristic impedance, a termination using resistance and inductance determined by FDTD and simple circuit calculations is introduced. The reflection coefficient at the proposed termination is 13.5 dB lower than that of the previous resistance termination at 10 GHz.