Low Reactance Research Articles

Trait Reactance Moderates Facebook Users' Irritation with Brand Communication

Our aim was to discover common relationship norms in Facebook communication between a brand and its fans, and to understand how these norms influence consumers' perceived irritation with brand messages. A semantic network analysis revealed that 7 out of 8 brands operated according to exchange relationship norms in communicating with their fans, whereas 1 brand operated according to communal relationship norms. We subsequently examined the effect of trait reactance and communication styles on the perceived level of irritation caused by branded messages received on Facebook with a sample of Korean college students (N = 161 participants). Results showed that those high in trait reactance perceived the exchange communication as more irritating than did those low in trait reactance. There was no difference between high and low reactance individuals in their perceived irritation with communal communication. Theoretical and practical implications are discussed and suggestions for future research provided.

Resistive Superconducting Fault Current Limiters Are Becoming a Mature Technology

Resistive superconducting fault current limiters (rSFCL) are reliably reacting devices and excellent means to overcome issues of higher short circuit current levels resulting from added electricity generation and more interconnected networks. Due to the strong impedance increase of the superconductor components initiated by a fault and the very low reactance under all operating conditions the rSFCL technology is ideal for protection of electricity grids. Several rSFCL systems based on different superconductor materials have been designed, built, tested, and commissioned by Nexans SuperConductors at distribution grids of several DNOs and also two times at a power plant. A recently built system is operating together with a HTS cable to supply up to 40 MVA on 10 kV enabling a very compact cable design. First market opportunities for medium voltage SFCLs have been identified and fully commercial projects targeting at permanent installations are now becoming reality. Different development stages leading from first trial devices to real commercial systems are presented including further necessary steps for SFCLs getting close to serial production.

Yes, we have no bananas: Consumer responses to restoration of freedom

When stockouts restrict consumers' freedoms, two independent responses can occur: product desirability, or a reactance-based increase in the desire for the unavailable option, and source negativity, or general frustration with the source of the restriction. In four studies, we provide a novel investigation of consumer responses to stockout-restoration and examine how these two forces combine to affect consumer responses after freedoms are restored. To do so, we investigate two moderators that influence the activation and strength of product desirability and source negativity, respectively: trait reactance and attributions. While all consumers experience source negativity in response to stockouts, only consumers high in reactance experience product desirability, leading to differential responses to stockout-restoration. Compared to an in-stock condition, high reactance consumers respond positively to stockout-restoration, while low reactance consumers respond negatively to stockout-restoration, in terms of store and product evaluations and store choice. However, when high reactants attribute a stockout to the store, thereby increasing source negativity relative to product desirability, they respond negatively to stockout-restoration.

Biomedical Implementation of Liquid Metal Ink as Drawable ECG Electrode and Skin Circuit

BackgroundConventional ways of making bio-electrodes are generally complicated, expensive and unconformable. Here we describe for the first time the method of applying Ga-based liquid metal ink as drawable electrocardiogram (ECG) electrodes. Such material owns unique merits in both liquid phase conformability and high electrical conductivity, which provides flexible ways for making electrical circuits on skin surface and a prospective substitution of conventional rigid printed circuit boards (PCBs).MethodsFundamental measurements of impedance and polarization voltage of the liquid metal ink were carried out to evaluate its basic electrical properties. Conceptual experiments were performed to draw the alloy as bio-electrodes to acquire ECG signals from both rabbit and human via a wireless module developed on the mobile phone. Further, a typical electrical circuit was drawn in the palm with the ink to demonstrate its potential of implementing more sophisticated skin circuits.ResultsWith an oxide concentration of 0.34%, the resistivity of the liquid metal ink was measured as 44.1 µΩ·cm with quite low reactance in the form of straight line. Its peak polarization voltage with the physiological saline was detected as −0.73 V. The quality of ECG wave detected from the liquid metal electrodes was found as good as that of conventional electrodes, from both rabbit and human experiments. In addition, the circuit drawn with the liquid metal ink in the palm also runs efficiently. When the loop was switched on, all the light emitting diodes (LEDs) were lit and emitted colorful lights.ConclusionsThe liquid metal ink promises unique printable electrical properties as both bio-electrodes and electrical wires. The implemented ECG measurement on biological surface and the successfully run skin circuit demonstrated the conformability and attachment of the liquid metal. The present method is expected to innovate future physiological measurement and biological circuit manufacturing technique in a large extent.

Prototype Fault Current Limiter Using Transformer and a Modular Device of YBCO Coated Conductor

A superconducting fault current limiter (SCFL) consisted of a transformer with low reactance connected to the power line and with the secondary winding short-circuited by a modular superconducting limiter device with 16 elements connected in series was constructed and tested. The designed coupling transformer has low dispersion reactance in order to limit the voltage drop in the power line within the range of 5 % to 10 %. The experimental results showed that an insertion of a 0.125 Ω resistance limited the peak current to a factor of 2.5 times of the unlimited current. The power dissipation reached 39 kW during 100 ms, with an energy density of 380 J/cm3. Based on these results, the SCFL will be further tested in a 3 MVA (15 kV/380 V) generator for currents up to 10 kA.

Steady-state operating conditions of very long EHVAC cable lines: Two case studies

The paper deals with the operation of very long EHV AC cable lines in a well-developed bulk power system, by simulating two 400 kV–50 Hz single circuit cable lines, 80–100 km long, installed at different locations of the Italian transmission network, both standing alone and in parallel to an existing overhead line. The power transmission limits of the considered cable lines are assessed analytically, as well as the required amount of shunt compensation and its location, at line terminals or also at mid-line; a criterion for sizing mid-line shunt compensation is also proposed. In order to check theoretical analyses carried out by analytical formulas, AC load flow simulations of the transmission network with the hypothetical cable lines in place are evaluated, referring to severe loading conditions in both normal and post-contingency operation. Open-ended cable operation and shunt compensation contingencies are also addressed. Results show that power transmission limits due to cable ampacity and higher active power flows due to low cable reactance do not pose special constraints on the operation of the powerful network under examination. Appropriate shunt compensation minimizes the effects of surplus cable reactive power, allowing to operate long 400 kV–50 Hz cable lines (up to 100 km at least) with reactors at line terminals only. Moreover, if shunt compensation is installed also at mid-line, operating capabilities of the long cable lines are enhanced and losses reduced.

A 225 kW Direct Driven PM Generator Adapted to a Vertical Axis Wind Turbine

A unique direct driven permanent magnet synchronous generator has been designed and constructed. Results from simulations as well as from the first experimental tests are presented. The generator has been specifically designed to be directly driven by a vertical axis wind turbine and has an unusually low reactance. Generators for wind turbines with full variable speed should maintain a high efficiency for the whole operational regime. Furthermore, for this application, requirements are placed on high generator torque capability for the whole operational regime. These issues are elaborated in the paper and studied through simulations. It is shown that the generator fulfils the expectations. An electrical control can effectively substitute a mechanical pitch control. Furthermore, results from measurements of magnetic flux density in the airgap and no load voltage coincide with simulations. The electromagnetic simulations of the generator are performed by using an electromagnetic model solved in a finite element environment.

A Five-/Nine-Level Twelve-Switch Neutral-Point-Clamped Inverter for High-Speed Electric Drives

A five-/nine-level twelve-switch inverter is described for three-phase high-speed electric machines having a low per-unit leakage reactance. By reducing the voltage blocking requirement of the semiconductors, the neutral-point-clamped (NPC) variant of the coupled inductor (CI) inverter topology (NPC-CI) is more suited to high dc bus voltages than the six-switch alternative (six-switch CI). Operational and design details are described for the NPC-CI inverter using a three-limb inductor core, including practical considerations for the inverter construction and operation, 480 V/208 V inductor mass comparison between six- and twelve-switch topologies, natural voltage balancing of the split-capacitor dc link, and voltage stresses of the freewheel diodes. Improvements in machine performance are illustrated using two experimental test rigs: an unloaded 18 000-r/min 15-hp induction machine to illustrate improved harmonic quality when operating with a limited switching frequency and a high fundamental output frequency, and a loaded 2-hp utility speed induction machine to demonstrate transient performance.

The predictive value of gastric reactance for postoperative morbidity and mortality in cardiac surgery patients

No useful method to directly monitor the level of end organ tissue injury is currently available clinically. Gastric reactance has been proposed to measure changes in a tissue structure caused by ischemia. The purpose of this study was to assess whether gastric reactance is a reliable, clinically relevant predictor of complications and a potentially useful tool to assess hypoperfusion in cardiovascular surgery patients. The value of gastric reactance measurements, standard hemodynamic and regional perfusion variables, and scores to predict postoperative complications were compared in 55 higher risk cardiovascular surgery patients with cardiopulmonary bypass. Low frequency gastric reactance, XL, had a significant predictive value of postoperative persistent shock requiring more than 48 h of vasopressors and associated complications, before, during and after surgery (p < 0.05). Results suggest that reactance is an earlier predictor of patients at risk than all other variables tested. Patients with a high reactance (XL > 26) before surgery had a significantly higher incidence of complications, higher mortality and more days in the ICU than patients with a low reactance (XL < 13). XL was found to be a reliable and clinically relevant measurement. These results justify further clinical research to explore how this information may be used to improve patient management.

A Practical Series-Shunt Hybrid Active Power Filter Based on Fundamental Magnetic Potential Self-Balance

In this paper, a novel series-shunt hybrid active power filter based on fundamental magnetic potential self-balance is reported. It consists of three parts: a passive power filter, a voltage-source pulsewidth-modulated (PWM) converter and a series zero magnetic flux current transformer. The zero magnetic flux current transformer locating in series between the power supply and nonlinear loads presents low reactance to fundamental and high impedance to the harmonics automatically. And the harmonic voltage dropped on the zero magnetic flux current transformer can be detected in real time. The voltage-source PWM converter is controlled as a harmonic voltage source. Wherein, it is connected to the passive filters in series through an isolated transformer. Therefore the flow-in harmonic current will be less than before. The configuration, working principle and performance analysis of the designed hybrid active power filter are determined. The validity of the theory and excellent compensation characteristics are proved by an experimental prototype. The current distortion factor is decreased from 20.46% to 2.67% by using this hybrid active power filter.

AIRFLOW PERTURBATION DEVICE REFLECTS FORCED OSCILLATION INDICES OF PERIPHERAL AIRWAY OBSTRUCTION

PURPOSE: Forced Oscillation (FO) provides indices of peripheral airway obstruction (frequency dependence of resistance [f-d R] and low frequency reactance); but resistance (R) measured by occlusion or airflow perturbation devices (APD) has hitherto measured R at only a single frequency. We used APD to measure R at 5 and 15 Hz (R5 and R15) to correlate with FO measures of f-d R and low frequency reactance area (AX) and thereby to determine if APD reflects peripheral airway obstruction in patients with asthma or COPD (obstructive airway disease, OAD).

Clinical applications of forced oscillation to assess peripheral airway function

Forced oscillation applies external pressures to the respiratory system to measure respiratory impedance. Impedance of larger central airways may be dissected from that of peripheral airways using multiple oscillation frequencies. Respiratory impedance is calculated by computer-assisted methods that yield separate resistive and reactive components. The reactive component includes respiratory system capacitative and inertive properties, which may be separately visualized for clinical purposes using resonance as a rough dividing line. Low oscillation frequencies comprise those below resonance, and relate most prominently to capacitative properties of peripheral airways. High oscillation frequencies comprise those greater than resonance, which relate most prominently to inertial properties of larger central airways. Measurements of resistance and reactance in patients with peripheral airway disease, before and after therapeutic intervention, manifest characteristic patterns of response in low frequency resistance and reactance measures that appear to be closely correlated with each other. In contrast, changes in large central airways manifest resistance change uniformly over low and high frequencies.

Analytical Calculation of the Magnetic Field Produced by Electric Power Lines

The magnetic field produced by electric power lines is usually calculated numerically with the use of a computer. However, the analytical calculation of the magnetic field is preferable because it results in a mathematical expression for showing its dependences on the various parameters of the line arrangement. A method to derive the analytical formula of the magnetic field vector produced by any power line is developed in this paper. The specific formulas for the magnetic field produced by any single circuit line in flat, vertical, or delta arrangement, as well as for hexagonal lines considered as double circuit lines in super bundle or low reactance phase arrangements or as six-phase lines, are given. The derived formulas are valid at any point with practical importance, close to or far from the line. The development of the method is made possible with the use of new kinds of numbers, named double complex numbers, to represent the magnetic field vector in the vicinity of power lines. Double complex numbers remarkably simplify the mathematical expressions for the magnetic field vector. Using these numbers, it is observed that the infinite terms of the magnetic field multipole expansion, for flat single circuit lines and for lines exhibiting polygonal symmetry are contracted, resulting in simple formulas for the magnetic field vector, which is used to derive the formulas for the resultant value of the magnetic field. The general formula of the magnetic field vector produced by an arbitrary power line is a rational function of the distance from it. Through the given expressions for the coefficients of this function numerator and denominator, the formula for the magnetic field vector produced by any power line can be derived.

Continuous conduction mode operation of three-phase diode bridge rectifier with constant load voltage

Three-phase diode bridge rectifiers with a low source reactance cause considerable current harmonics in the AC supply, which may not meet the latest EMI regulations. At higher source reactance the bridge is more likely to operate in continuous conduction mode (CCM), leading to a reduction in harmonic current level. In the paper accurate analytical expressions are derived for the AC current harmonics, the input power and the power factor in CCM, which have been validated through numerical simulations and practical experiments. They can therefore be used with confidence for the design of power supplies with lower harmonic levels. Remedies are proposed to compensate for the drawbacks of CCM operation, using power factor correction capacitors and a single-switch inductor-less boost rectifier.

Effects of deep inspiration (DI) on respiratory impedance measured by impulse oscillometry (IOS)

Rationale Deep inspiration (DI) normally causes a decrease of bronchomotor tone; but in some asthmatic subjects, DI has been shown to cause increased bronchomotor tone. Methods This study measured effects of DI by forced oscillation using IOS, in 29 patients evaluated for allergic rhinitis and asthma. Triplicate 30 sec IOS tests of quiet breathing, and a 60 sec IOS test with DI between 30-35 sec were done before and after nebulized levalbuterol including resistance at 5Hz (R5) and low frequency reactance (AX). Routine spirometry was performed after each set of IOS tests. Results Baseline small airway inflammation (increased AX) was associated with increased bronchoconstrictor response (increased impedance) to DI; and levalbuterol inhalation was associated with decreased bronchoconstrictor response to DI, irrespective of spirometry. Conclusions We conclude that concurrent airway inflammation and baseline bronchomotor tone modulate the response to DI in asthmatic subjects, irrespective of spirometric results.

Within- and between-day variability of respiratory impedance, using impulse oscillometry in adolescent asthmatics.

The objectives of the present study were to: 1) assess spirometric indices and respiratory impedance with forced oscillation (FO), using impulse oscillometry (IOS) in clinically stable asthmatic children over 3 consecutive days; 2) assess FO reactance (X), using an integrated index and resistance (R) separately during inspiration and expiration; and 3) assess effects on FO of hand support of cheeks vs. no hand support. Our hypotheses were: 1) because of increased sensitivity, IOS manifests day-to-day variability not demonstrable by spirometry; 2) IOS R during expiration exceeds that during inspiration; and 3) hand support of cheeks affects IOS R and X only minimally. We obtained triplicate twice-daily measures of IOS R and X in asthmatic adolescents at summer camp, in a convenience sample of children willing, with parental permission, to undergo repeated testing on consecutive days. Subjects received all medications between 6:30-7:30 AM, and were bronchodilated at time of testing. Subjects underwent IOS tests without hand support of cheeks, followed by tests with both hands supporting cheeks. ANOVA and regression analyses were used to discern technique differences.Significant differences in IOS inspiratory R5, R5 - R15 (frequency dependence of R), and low frequency reactance area (AX) occurred across 3 days, but spirometric indices were unchanged. Inspiratory R at 5 Hz (R5) was significantly smaller than expiratory R5 (P < 0.0001). ANOVA revealed no significant differences between hand and facial muscle cheek support for IOS R and X below 15 Hz, but significant differences occurred above 15 Hz. In conclusion, inspiratory R5, R5 - R15, and AX are sensitive measures for detecting changes in bronchomotor tone in adolescent asthmatic subjects, while expiratory R5 may be influenced by additional factors. Manual support of cheeks does not appear to affect IOS indices of peripheral airway obstruction in adolescent asthmatics. IOS is a practical method for quantifying respiratory mechanics, and its potential role in disease management warrants further study.

Comparison of Different Motor Types for Electricvehicle Application

SummaryThe drive of an electrk Vehicle (Fig.I) requires a small volume, a high power to weight ratio, a high efficiency, a wide speed range. reliability and low costs in manufacturing and maintenance. In this article is presented the comparison of . induction motors (ASIWN). permanent magnet synchmous motors (PMSM’s) and a permanent magnet synchronous motor with auxiliary exciting windings (HYB).Because of absence of maintenance and its large robustness the squirrel-cage ASM is absolutely suitable to equip an electric vehicle. To reach a wide speed range (over 7000 rpm) and a high efficiency the motor must be designed with low stray reactance’s and coppercage rotor. This does not lead to a weight optimal solution.The PAISM with high energy rare earth magnets has a higher efficiency than the ASM. because it does not need a magnetizing current. which produces additional losses. it can also reach speeds as high as the ASM, by feeding the stator windings with an additional negative direct current. But such properties are only possible with a small number of pole pairs.The HYB has a high number of pole pairs, that is more interesting from the weight point of view. but it needs auxiliary exciting windings. By field-strengthening at low speed the motor can deliver a high torque if necessary. By field-weak-ening in the rotor and feeding the suitor with a negative direct current the motor can also reach the maximal speed. Prototypes of each synchronous machine have been designed by FEM-analysis, built and measured on a test bench in the institute.

Potential of microperforated panel absorber

Many applications have been found for the microperforated panel (MPP) absorber, on which the perforations are reduced to submillimeter size so that they themselves will provide enough acoustic resistance and also sufficiently low acoustic mass reactance necessary for a wide-band sound absorber. The most important parameter of the MPP is found to be the perforate constant k which is proportional to the ratio of the perforation radius to the viscous boundary layer thickness inside the holes. This, together with the relative (to the characteristic acoustic impedance in air) acoustic resistance r and the frequency f0 of maximum absorption of the MPP absorber, decides the entire structure of the MPP absorber and its frequency characteristics. In other words, the MPP absorber may be designed according to the required absorbing characteristics in terms of the parameters k, r, and f0. Formulas and curves are presented toward this end. It is shown that the MPP absorber has tremendous potential for wide-band absorption up to 3 or 4 octaves and for low-frequency absorption with a cavity of depth small compared to the wavelength. Techniques of making minute holes (of 0.1–0.3 mm, say) have to be developed, though.

The study of the relation between R/sub n/-G/sub n/ noise model and E/sub n/-I/sub n/ noise model of an amplifier

The R/sub n/-G/sub n/ noise model can only be used in the case of microwave low-noise amplifier design. Its application scopes are limited and in particular, it cannot be used in low-frequency low-noise amplifier design. This paper has adopted the E/sub n/-I/sub n/ noise model with spectral correlative coefficient (SCC) so that it can be used not only in high-frequency and narrow-band, but also in low frequency, source reactance, and wide-band amplifier low-noise design. In this paper, the equivalent relation between the E/sub n/-I/sub n/ noise model and the R/sub n/-G/sub n/, noise model is derived, and the measurement method of the E/sub n/-I/sub n/ noise model parameters and the measurement results are given. The R/sub n/-G/sub n/, noise model parameters can be accurately obtained by use of the equivalent relation.

Power line magnetic flux density quick estimation plots

This paper introduces the method of quick estimation plots to characterize the magnetic flux density associated with power lines. The largest value of the magnetic flux density magnitude and its location along a lateral traverse at or close to ground level can be determined using these quick estimation plots. The plots are available for single circuit (horizontal, vertical and delta) and double circuit (super bundle and low reactance) three phase power line configurations, assuming balanced, symmetrical three phase currents.