Change In Admittance Research Articles

Signal Processing of Vector Network Analyzer Measurement for Quartz Crystal Microbalance With Viscous Damping

We have developed a system to obtain both the resonance frequency and resistance from a quartz crystal microbalance (QCM) using a portable vector network analyzer (VNWA). Acoustic loading on a QCM causes a change in admittance, which can be measured by a VNWA. For application as an odor sensor, it is necessary to coat the QCM with a sensing film. Since many sensing films are highly viscous, the noise level is high owing to viscous damping. Thus, we propose a curve fitting method by utilizes all the datapoints within a certain frequency range to obtain the resonance frequency. The scan frequency range, the number of datapoints and the measurement time per datapoint are optimized to achieve minimum noise. Then, the data after curve fitting are applied to a Savitzky–Golay filter with a polynomial approximation within the moving window to further smooth the temporal frequency data, while maintaining the sharpness of the sensor response. All the entire process can be carried out in real time. The Savitzky–Golay filter was found to be able to suppress noise after the optimization of window size optimization. The effectiveness of the system was confirmed by performing an independent t-test.

An Optimal Control Approach to Identify the Worst-Case Cascading Failures in Power Systems

Cascading failures in power systems normally occur as a result of initial disturbances or faults on electrical elements, closely followed by situational awareness errors of human operators. It remains a great challenge to systematically trace the source of cascading failures in power systems. In this paper, we develop a mathematical model to describe the cascading outages of transmission lines in power networks. In particular, the direct current power-flow equation is employed to calculate the power flow on the branches. By regarding the disturbances on branches as the control inputs, the problem of identifying the initial disruptive disturbances is formulated with optimal control theory, which provides a systematic approach to explore the most disruptive disturbances that give rise to changes of branch admittance in addition to direct branch outages. Moreover, an iterative search algorithm is proposed to look for the optimal solution leading to the worst-case cascading failures. Theoretical analysis guarantees the asymptotic convergence of the iterative search algorithm. Finally, numerical simulations are carried out on the IEEE test systems to validate the proposed approach.

Effect of Probe-Tone Frequency on Ipsilateral and Contralateral Electrical Stapedius Reflex Measurement in Children With Cochlear Implants.

The upper loudness limit of electrical stimulation in cochlear implant patients is sometimes set using electrically elicited stapedius reflex thresholds (eSRTs), especially in children for whom reporting skills may be limited. In unilateral cochlear implant patients, eSRT levels are measured typically in the contralateral unimplanted ear because the ability to measure eSRTs in the implanted ear is likely to be limited due to the cochlear implant surgery and consequential changes in middle ear dynamics. This practice is particularly limiting in the case of fitting bilaterally implanted pediatric cases because there is no unimplanted ear option to choose for eSRT measurement. The goal of this study was to identify an improved measurement protocol to increase the success of eSRT measurement in ipsilateral or contralateral or both implanted ears of pediatric cochlear implant recipients. This work hypothesizes that use of a higher probe frequency (e.g., 1000 Hz compared with the 226 Hz standard), which is closer to the mechanical middle ear resonant frequency, may be more effective in measuring middle ear muscle contraction in either ear. In the present study, eSRTs were measured using multiple probe frequencies (226, 678, and 1000 Hz) in the ipsilateral and contralateral ears of 19 children with unilateral Advanced Bionics (AB) cochlear implants (mean age = 8.6 years, SD = 2.29). An integrated middle ear analyzer designed by AB was used to elicit and detect stapedius reflexes and assign eSRT levels. In the integrated middle ear analyzer system, an Interacoustics Titan middle ear analyzer was used to perform middle ear measurements in synchrony with research software running on an AB Neptune speech processor, which controlled the delivery of electrical pulse trains at varying levels to the test subject. Changes in middle ear acoustic admittance following an electrical pulse train stimulus indicated the occurrence of an electrically elicited stapedius reflex. Of the 19 ears tested, ipsilateral eSRTs were successfully measured in 3 (16%), 4 (21%), and 7 (37%) ears using probe tones of 226, 678, and 1000 Hz, respectively. Contralateral eSRT levels were measured in 11 (58%), 13 (68%), and 13 (68%) ears using the three different probe frequencies, respectively. A significant difference was found in the incidence of successful eSRT measurement as a function of probe frequency in the ipsilateral ears with the greatest pair-wise difference between the 226 and 1000 Hz probe. A significant increase in contralateral eSRT measurement success as a function of probe frequency was not found. These findings are consistent with the idea that changes in middle ear mechanics, secondary to cochlear implant surgery, may interfere with the detection of stapedius muscle contraction in the ipsilateral middle ear. The best logistic, mixed-effects model of the occurrence of successful eSRT measures included ear of measurement and probe frequency as significant fixed effects. No significant differences in average eSRT levels were observed across ipsilateral and contralateral measurements or as a function of probe frequency. Typically, measurement of stapedius reflexes is less successful in the implanted ears of cochlear implant recipients compared with measurements in the contralateral, unimplanted ear. The ability to measure eSRT levels ipsilaterally can be improved by using a higher probe frequency.

Interaction of increasing ICU survival and admittance policies in patients with hematologic neoplasms: A single center experience with 304 patients.

We evaluated the development of ICU survival of patients with hematopoietic malignancies and discussed changes in admittance policies. We compared 166 patients treated between 2009 and 2012 with 138 patients treated between 2013 and 2016. Patient characteristics and outcome were analyzed. ICU survival was 45.2% in the first group and 66.7% in the second (P<0.0005). Infection (P=0.033), invasive ventilation (IMV) (P=0.014) and SOFA score at day 3 (SOFA-48h) (P=0.007) independently indicated worse ICU survival in the first group, IMV (P=0.013) and SOFA-48h (P=0.019) in the second group. The second group showed lower frequencies of infection (P=0.003), IMV (P<0.0005), need for vasopressors (P<0.0005) and RRT (P=0.021) at ICU admittance than the first. Further, the accumulation of hyperkaliemia, acidosis, low bicarbonate, high lactate and hypotension showed worse ICU survival in both groups and was lower in second group. ICU survival increased distinctly between 2009 and 2016. At ICU admittance, parameters showing severity of illness were less frequent in the second group. Our findings indicate general treatment improvements especially of infections and changes of admittance policies toward early ICU admittance during time.

Fast identification of symmetrical/asymmetrical faults during power swing with dual use line relays

Increasing power demand, penetration of renewables, and limitations of necessary grid expansion are proffering new challenges to existing power system protection and control strategies. However, with the advancement in intelligent electronic devices and relaying technology, fast, accurate and reliable protection schemes can be developed for smart power systems. In this paper, a new protection scheme based on admittance and power change has been proposed with dual-use line relays to detect symmetrical/asymmetrical faults in power systems. A large number of fault environments have been simulated by varying fault distances from relay location, fault resistance, and power angle in single machine infinite bus and WSCC 9-bus systems. Some crucial decisive fault scenarios e.g. close in/far end faults, faults in series compensated line, faults during asymmetrical swings, switching ON/OFF large loads, single and multi-modal swings have also been verified for the proposed index. In this paper, for the first time, detection of faults during power swings have been examined and verified in the presence of wind farms. The simulation results show the proficiency of the proposed algorithm for detecting faults in the presence or absence of power swings.

Binding of Potassium Ions Inside the Access Channel at the Cytoplasmic Side of Na+,K+-ATPase

Binding of potassium ions through an access channel from the cytoplasmic side of Na+,K+-ATPase and the effect of pH and magnesium ions on this process have been studied. The studies were carried out by a previously developed method of measuring small increments of the admittance (capacitance and conductivity) of a compound membrane consisting of a bilayer lipid membrane with adsorbed membranes fragments containing Na+,K+-ATPase. The capacitance change of the membrane with the Na+,K+-ATPase was induced abruptly by release of protons from a bound form (caged H+) upon a UV-light flash in the absence of magnesium ions. The change of admittance consisted of an initial fast jump and a slow relaxation to a stationary value within a time of about 1–2 s. The kinetics of the capacitance relaxation depended on pH and the concentration of magnesium and potassium ions. The dependence of the rapid capacitance jump on the potassium concentration corresponded to the predictions of the model developed earlier that describes binding of sodium or potassium ions in competition with protons. The effect of magnesium ions can be explained by the assuming that they bind to the Na+,K+-ATPase and affect binding of potassium ions because of either changes in protein conformation or the creation of an electrostatic field in the access channel on the cytoplasmic side.

Impact of Insulation Type and Thickness on the Dynamic Thermal Characteristics of an External Wall Structure

The dynamic thermal characteristics of external wall structures are directly related to indoor thermal comfort and energy savings in buildings; they are also complicated and worth investigating. Thermal insulation in external wall structures has become a popular topic of investigation in the domain of building energy efficiency. This study aims to find the impact of insulation type and thickness on the dynamic thermal characteristics of external wall structures using a homogeneous multi-layer building external wall structure and three types of insulation materials that are widely used in Japan. The impact of insulation type and thickness on seven thermal characteristics of external walls, including thermal transmittance, decrement factor or amplitude attenuation, time lag, thermal admittance, time lead for thermal admittance, surface factor, and thermal capacity, was evaluated by numerical methods in this study. It was shown that insulation type and thickness would have a significant effect on thermal transmittance, decrement factor and time lag, but yield no significant change in thermal admittance, time lead for thermal admittance, surface factor, and the thermal capacity of external wall structures.

Electrically Evoked Stapedial Reflex Threshold: A Procedure

Objective measures, such as the electrically evoked stapedial reflex threshold (ESRT), are critical components of optimal cochlear implant (CI) programming. Recent data suggest, however, that ESRT measurements are not commonly used by audiologists when programming CIs (Hemmingson & Messersmith, 2017). Potential reasons for limited use of these measures may be limited knowledge of the procedure for completing the measures and limited knowledge of how to apply results to programming. Clinically, ESRT is observed as a change in the static admittance of the ear canal in response to electrical stimulation through the CI; this deflection can be observed using the decay setting on an immitance bridge. ESRT is defined as the lowest amount of electrical stimulation that results in a 0.02 deflection from baseline (Gelfand, 2002). ESRT has been found to align closely to behaviorally measured upper comfort levels (e.g., C/M levels in the manufacturer software) and, as such, can assist in determining appropriate C/M l...

Estimating driver time-varying neuromuscular admittance through LPV model and grip force

Humans can rapidly change their low-frequency arm dynamics (i.e., stiffness) to resist forces or give way to them. Quantifying driver’s time-varying arm dynamics is important for the development of steer-by-wire systems and haptic driver support systems. Conventional LTI identification, and even time-varying techniques such as wavelets, fail to capture rapidly-varying low-frequency dynamics. In this study, we propose to estimate driver admittance in real-time, using grip force measurement of the hands on the steering wheel and linear parameter-varying (LPV) modeling techniques. We hypothesized that grip force is strongly correlated to neuromuscular admittance, and can serve as an appropriate scheduling variable for an LPV model. We performed an experiment in which 18 subjects performed a boundary tracking task, and applied torque perturbations to the steering wheel to perform a baseline LTI identification. Six different boundary widths were used to evoke changes in admittance, while their grip force was measured with pressure gloves. A global LPV model is identified by linear interpolation between the local LTI models identified for each boundary width. The estimated stiffness and damping parameters varied proportionally with the grip force. Although small between-subject variations in grip force levels are found, we conclude that grip force can indeed serve as an appropriate scheduling variable for a global LPV model, which is capable of tracking fast-changing admittance changes. Future work focuses on using the LPV model in realistic driving tasks, permitting admittance estimates to be obtained without the need to apply external disturbance torques on the steering wheel.

Fault identification using piezoelectric impedance measurement and model-based intelligent inference with pre-screening

While piezoelectric impedance/admittance measurements have been used for fault detection and identification, the actual identification of fault location and severity remains to be a challenging topic. On one hand, the approach that uses these measurements entertains high detection sensitivity owing to the high-frequency actuation/sensing nature. On the other hand, high-frequency analysis requires high dimensionality in the model and the subsequent inverse analysis contains a very large number of unknowns which often renders the identification problem under-determined. A new fault identification algorithm is developed in this research for piezoelectric impedance/admittance based measurement. Taking advantage of the algebraic relation between the sensitivity matrix and the admittance change measurement, we devise a pre-screening scheme that can rank the likelihoods of fault locations with estimated fault severity levels, which drastically reduces the fault parameter space. A Bayesian inference approach is then incorporated to pinpoint the fault location and severity with high computational efficiency. The proposed approach is examined and validated through case studies.

Quantitative microwave impedance microscopy with effective medium approximations

Microwave impedance microscopy (MIM) is a scanning probe technique to measure local changes in tip-sample admittance. The imaginary part of the reported change is calibrated with finite element simulations and physical measurements of a standard capacitive sample, and thereafter the output ΔY is given a reference value in siemens. Simulations also provide a means of extracting sample conductivity and permittivity from admittance, a procedure verified by comparing the estimated permittivity of polytetrafluoroethlyene (PTFE) to the accepted value. Simulations published by others have investigated the tip-sample system for permittivity at a given conductivity, or conversely conductivity and a given permittivity; here we supply the full behavior for multiple values of both parameters. Finally, the well-known effective medium approximation of Bruggeman is considered as a means of estimating the volume fractions of the constituents in inhomogeneous two-phase systems. Specifically, we consider the estimation of porosity in carbide-derived carbon, a nanostructured material known for its use in energy storage devices.

A robust power flow model for active power flow control via thyristor‐controlled series compensator

In this paper, a new power flow model for active power flow control through a thyristor‐controlled series compensator (TCSC) in an AC network system is proposed. The proposed power flow model is based on the Newton–Raphson method. In this model, TCSC's admittance effect is included as a state variable into the Jacobian matrix to avoid the divergence problem. Unlike similar studies in the literature, TCSC's admittance is ignored in the bus admittance matrix, and the need for rebuilding the bus admittance matrix in each power flow iteration caused by the change of TCSC's admittance is prevented. So, faster convergence for power flow calculation is achieved. For this aim, new power equations are obtained. Also, in the proposed approach, we need not consider each terminal of TCSC as an individual bus in the power flow calculation. Thus, increasing the Jacobian and bus admittance matrixes sizes caused by the total bus number is prevented. The proposed approach is tested on an IEEE 57‐bus test system. The obtained results prove that this approach provides efficient, reliable, and fast convergence. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Disturbance compensation in electric generator network control

The paper considers electric generator network control under conditions of parametric uncertainty and disturbing actions caused by the mechanical power nonstationarity and possible changes in transmission-line admittance. A decentralized control algorithm that maintains operator generation stability and network phase synchronization with the required accuracy is synthesized. Numerical examples and computational simulation results are presented illustrating the operation capability of the proposed control scheme.

Differential C4D sensor for conductive and non-conductive fluidic channel

This paper presents a novel design of a differential C4D (DC4D) sensor based on three electrodes for both conductive and non-conductive fluidic channel. This structure consists of two single C4D with an applied carrier sinusoidal signal to the center electrode as the excitation electrode. The electrodes are directly bonded on the PCB with built-in differential amplifier and signal processing circuit in order to reduce the parasitic component and common noise. In the non-conductive fluidic channel, the output voltage and capacitance changes 214.39 mV and 14 fF, respectively when a 3.83 μl tin particle crosses an oil channel. In conductive fluidic channel, the output voltage and admittance change up to 300 mV and 0.07 μS for the movement of a 4.88 μl plastic particle through channel. Moreover, the voltage change of this sensor is linear relation with the volume of investigated particle. This sensor also allows measuring velocity of particle inside fluidic channel and resistivity of the conductive fluidic.

Simulation of PZT monitoring of reinforced concrete beams retrofitted with CFRP

A numerical study has been carried out to simulate an innovative monitoring procedure to detect and localize damage in reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) unidirectional laminates. The main novelty of the present simulation is its ability to conduct the electromechanical admittance monitoring technique by considerably compressing the amount of data required for damage detection and localization. A FEM simulation of electromechanical admittance-based sensing technique was employed by applying lead zirconate titanate (PZT) transducers to acquire impedance spectrum signatures. Response surface methodology (RSM) is finally adopted as a tool for solving inverse problems to estimate the location and size of damaged areas from the relationship between damage and electromechanical admittance changes computed at PZT transducer surfaces. This statistical metamodel technique allows polynomial models to be produced without requiring complicated modeling or numerous data sets after the generation of damage, leading to considerably lower cost of creating diagnostic database. Finally, a numerical example is carried out regarding a steel-reinforced concrete (RC) beam model monotonically loaded up to its failure which is also retrofitted by a CFRP laminate to verify the validity of the present metamodeling monitoring technique. The load-carrying capacity of concrete is predicted in the present paper by utilizing an Ottosen-type failure surface in order to better take into account the passive confinement behavior of retrofitted concrete material under the application of FRP laminate.

Airway obstruction, upper airway artifact and response to bronchodilator in asthmatic and healthy children.

The forced oscillation technique (FOT) may be affected by the upper airway artifact in children with airway obstruction. The aim was to test the impact of the artifact on FOT ability to diagnose asthma in children as recommended by current guidelines. The FOT was performed in 58 asthmatics and 27 controls before and after salbutamol. Respiratory resistance (Rrs) was measured at 8 Hz with a standard generator (SG), and a head generator (HG) that minimizes the upper airway artifact. The response to salbutamol was computed as change in respiratory resistance (Δ%Rrs) and admittance (Δ%Ars) that almost cancels the effect of the upper airway artifact. Rrs and Δ%Rrs were significantly larger in patients than controls by HG (respectively P < 0.001 and P = 0.002) but not SG, while Δ%Ars was larger in asthma than control by both (P < 0.04). Best discriminators between patients and controls were Rrs or Δ%Rrs by HG and Δ%Ars by SG. In asthmatic children, the upper airway artifact significantly impacts FOT measurements. The diagnostic value may be improved by minimization of the shunt, such as the computation of Δ%Ars.

Investigating the Kinetics of Antibody Adsorption onto Polyethylene Terephthalat (PET) Modified with Gold Nanoparticles in Flow Microchannel

The real-time monitoring of the adsorption kinetic of antibody onto polyethylene terephthalate (PET) modified with gold nanoparticles (NPs) is performed into a dielectric flow microchannel. The principle is based on the microelectrode–dielectric interface excitation by a modulated voltage excitation through the dielectric layer with high frequency range. The set-up configuration using a homemade current-to-voltage converter has been developed for fast monitoring of biomolecule adsorption without direct electrical contact of microelectrodes with the microchannel flow. The change in the interfacial admittance, related to the output voltage measured through the microchip, during antibody incubation, gives information on the kinetics involved while antibodies are adsorbed at the interface. An example of adsorption on PET modified with gold NPS was taken. Experimental data were fit with the Langmuir equation and a good correlation was obtained with this latter, where the equilibrium constant, K, was found as 1.55 × 108 M−1 with a limit of detection for antibody concentration without depletion equal to 8.25 nM.

The Effect of Flying and Low Humidity on the Admittance of the Tympanic Membrane and Middle Ear System

Many passengers experience discomfort during flight because of the effect of low humidity on the skin, eyes, throat, and nose. In this physiological study, we have investigated whether flight and low humidity also affect the tympanic membrane. From previous studies, a decrease in admittance of the tympanic membrane through drying might be expected to affect the buffering capacity of the middle ear and to disrupt automatic pressure regulation. This investigation involved an observational study onboard an aircraft combined with experiments in an environmental chamber, where the humidity could be controlled but could not be made to be as low as during flight. For the flight study, there was a linear relationship between the peak compensated static admittance of the tympanic membrane and relative humidity with a constant of proportionality of 0.00315mmho/% relative humidity. The low humidity at cruise altitude (minimum 22.7%) was associated with a mean decrease in admittance of about 20% compared with measures in the airport. From the chamber study, we further found that a mean decrease in relative humidity of 23.4% led to a significant decrease in mean admittance by 0.11mmho [F(1,8) = 18.95, P = 0.002], a decrease of 9.4%. The order of magnitude for the effect of humidity was similar for the flight and environmental chamber studies. We conclude that admittance changes during flight were likely to have been caused by the low humidity in the aircraft cabin and that these changes may affect the automatic pressure regulation of the middle ear during descent.

Acoustic Reflex Measurement

Middle ear muscle reflex (MEMR) measurements have been a part of the standard clinical immittance test battery for decades as a cross-check with the behavioral audiogram and as a way to separate cochlear from retrocochlear pathologies. MEMR responses are measured in the ear canal by using a probe stimulus (e.g., single frequency or broadband noise) to monitor admittance changes elicited by a reflex-activating stimulus. In the clinical MEMR procedures, one test yields changes in a single measurement (i.e., admittance) at a single pure tone (e.g., 226 or 1000 Hz). In contrast, for the wideband acoustic immittance (WAI) procedure,one test yields information about multiple measurements (e.g., admittance, power reflectance, absorbance) across a wide frequency range (e.g., 250 to 8000 Hz analysis bandwidth of the probe). One benefit of the WAI method is that the MEMR can be identified in a single test regardless of the frequency at which the maximum shift in the immittance measurement occurs; this is beneficial because maximal shifts in immittance vary as a function of age and other factors. Another benefit is that the wideband response analysis yields lower MEMR thresholds than with the clinical procedures. Lower MEMR thresholds would allow for MEMR decay tests in ears in which the activator levels could not be safely presented. Finally, the WAI procedures can be automated with objective identification of the MEMR, which would allow for use in newborn and other screening programs in which the tests are completed by nonaudiological personnel.

Effects of mode coupling on the admittance of an AT-cut quartz thickness-shear resonator

We study the effects of couplings to flexure and face-shear modes on the admittance of an AT-cut quartz plate thickness-shear mode resonator. Mindlin's two-dimensional equations for piezoelectric plates are employed. Electrically forced vibration solutions are obtained for three cases: pure thickness-shear mode alone; two coupled modes of thickness shear and flexure; and three coupled modes of thickness shear, flexure, and face shear. Admittance is calculated and its dependence on the driving frequency and the length/thickness ratio of the resonator is examined. Results show that near the thickness-shear resonance, admittance assumes maxima, and that for certain values of the length/thickness ratio, the coupling to flexure causes severe admittance drops, while the coupling to the face-shear mode causes additional admittance changes that were previously unknown and hence are not considered in current resonator design practice.