Reliability of impedance cardiography in measuring central haemodynamics
DEFF Research Database (Denmark)
Mehlsen, J; Bonde, J; Stadeager, C;
1991-01-01
The purpose of the study described here was to investigate the reliability of impedance cardiography (IC) in measuring cardiac output (CO) and central blood volume. Absolute values and changes in these variables obtained by impedance cardiography and by isotope- or thermodilution techniques were...... healthy subjects and in 25 unmedicated patients with ischaemic heart disease. We obtained significant correlations between absolute values (y = 0.68x + 1.48) and changes (y = 1.00x + 0.0003) in CO measured by IC and isotope- or thermodilution. IC significantly overestimated absolute values of CO (P less...... suitable for repeated measurements in studies on the haemodynamic effects of physiological or pharmacological intervention. Impedance cardiography is sufficiently reliable for comparison of absolute values of CO between different groups of patients. We cannot recommend impedance cardiography for...
[Cardiac output monitoring by impedance cardiography in cardiac surgery].
Shimizu, H; Seki, S; Mizuguchi, A; Tsuchida, H; Watanabe, H; Namiki, A
1990-04-01
The cardiac output monitoring by impedance cardiography, NCCOM3, was evaluated in adult patients (n = 12) who were subjected to coronary artery bypass grafting. Values of cardiac output measured by impedance cardiography were compared to those by the thermodilution method. Changes of base impedance level used as an index of thoracic fluid volume were also investigated before and after cardiopulmonary bypass (CPB). Correlation coefficient (r) of the values obtained by thermodilution with impedance cardiography was 0.79 and the mean difference was 1.29 +/- 16.9 (SD)% during induction of anesthesia. During the operation, r was 0.83 and the mean difference was -14.6 +/- 18.7%. The measurement by impedance cardiography could be carried out through the operation except when electro-cautery was used. Base impedance level before CPB was significantly lower as compared with that after CPB. There was a negative correlation between the base impedance level and central venous pressure (CVP). No patients showed any signs suggesting lung edema and all the values of CVP, pulmonary artery pressure and blood gas analysis were within normal ranges. From the result of this study, it was concluded that cardiac output monitoring by impedance cardiography was useful in cardiac surgery, but further detailed examinations will be necessary on the relationship between the numerical values of base impedance and the clinical state of the patients. PMID:2362347
The IMPACT shirt: textile integrated and portable impedance cardiography
International Nuclear Information System (INIS)
Measurement of hemodynamic parameters such as stroke volume (SV) via impedance cardiography (ICG) is an easy, non-invasive and inexpensive way to assess the health status of the heart. We present a possibility to use this technology for monitoring risk patients at home. The IMPACT Shirt (IMPedAnce Cardiography Textile) has been developed with integrated textile electrodes and textile wiring, as well as with portable miniaturized hardware. Several textile materials were characterized in vitro and in vivo to analyze their performance with regard to washability, and electrical characteristics such as skin-electrode impedance, capacitive coupling and subjective tactile feeling. The small lightweight hardware measures ECG and ICG continuously and transmits wireless data via Bluetooth to a mobile phone (Android) or PC for further analysis. A lithium polymer battery supplies the circuit and can be charged via a micro-USB. Results of a proof-of-concept trial show excellent agreement between SV assessed by a commercial device and the developed system. The IMPACT Shirt allows monitoring of SV and ECG on a daily basis at the patient’s home. (paper)
Daralammouri, Yunis; Ayoub, Khubaib; Badrieh, Najwan; Lauer, Bernward
2016-01-01
Background Impedance cardiography (IC) is a noninvasive modality that utilizes changes in impedance across the thorax to assess hemodynamic parameters, including stroke volume (SV). This study compared aortic valve area (AVA) as assessed by a hybrid approach of transthoracic echocardiography (TTE) and impedance cardiography (IC) to AVA determined at cardiac catheterization using the Gorlin equation. Methods A total of 30 patients with moderate to severe aortic stenosis underwent AVA measureme...
Hemodynamic evaluation in pregnancy: limitations of impedance cardiography
International Nuclear Information System (INIS)
Impedance cardiography (ICG) has been proposed to estimate the stroke volume (SV) and cardiac output (CO) in various medical indications. The aim of this study was to explore the reliability of ICG during pregnancy with respect to SV and CO measurements. Blood pressure, heart rate and thoracic impedance were monitored during the course of pregnancy and related ICG patterns analyzed. We determined thoracic impedance (Z0), left ventricular ejection time (LVET) and the maximum value of the first derivative of the impedance waveform (dZ/dt)max beat-to-beat. The two main components of non-invasive SV estimation, LVET and (dZ/dt)max, decreased in week 35 relative to week 12 by 7.6% ± 4.8% and by 36.0% ± 14.0%, respectively, based on a decrease in R–R interval of 9.9% ± 9.7%, whereas changes in Z0 did not play a significant role. Furthermore, the decrease of (dZ/dt)max was greater in the third compared to the second trimester of pregnancy. Taking into account an 18.2% ± 6.8% body weight increase, the calculated SV decreased in week 35 relative to week 12 by 19.2% ± 14.3%. The normalized term ((dZ/dt)max)/Z0 explained 85–94% of the variance of SV change after week 20. These results were confirmed for fixed R–R interval at a constant value across the repeated measurements. Based on beat-to-beat analysis of the main components of non-invasive SV estimation by ICG, measured repeatedly throughout normal pregnancy, we conclude that SV calculations render invalid data. Our findings strongly suggest that CO cannot be reliably assessed with ICG in pregnant women. (paper)
Bernstein, Donald P.
2010-01-01
Impedance cardiography (ICG) is a branch of bioimpedance pimarily concerned with the determination of left ventricular stroke volume (SV). As implemented, using the transthoracic approach, the technique involves applying a current field longitudinally across a segment of thorax by means of a constant magnitude, high frequency, low amplitude alternating current (AC). By Ohm's Law, the voltage difference measured within the current field is proportional to the electrical impedance Z (&Omega...
DEFF Research Database (Denmark)
Osbak, Philip S; Henriksen, Jens Henrik Sahl; Kofoed, Klaus F;
2011-01-01
Abstract Background. Atrial fibrillation (AF) is associated with significant morbidity and mortality. To test the effect of interventions, knowledge of cardiac output (CO) is important. However, the irregular heart rate might cause some methods for determination of CO to have inherent weaknesses....... Objective. To assess the validity of these methods in AF, a new inert gas rebreathing device and impedance cardiography was tested with echocardiography as reference. Methods. Using a cross-sectional design, 127 patients with AF and 24 in SR were consecutively recruited. Resting CO was measured using inert...... gas rebreathing (n = 62) or impedance measurement of intrathoracic blood flow (n = 89) in separate studies with echocardiographic measurement as reference. Results. CO determined with impedance cardiography was mean 4.77 L/min ± 2.24(SD) compared to 4.93 L/min ± 1.17 by echocardiography (n = 89, n...
Juan Carlos Márquez Ruiz; Markus Rempfler; Fernando Seoane; Kaj Lindecrantz
2013-01-01
During the last decades the use of Electrical Bioimpedance (EBI) in the medical field has been subject of extensive research, especially since it is an affordable, harmless and non-invasive technology. In some specific applications such as body composition assessment where EBI has proven a good degree of effectiveness and reliability, the use of textile electrodes and measurement garments have shown a good performance and reproducible results. Impedance Cardiography (ICG) is another modality ...
Development of a wearable multi-frequency impedance cardiography device.
Weyer, Sören; Menden, Tobias; Leicht, Lennart; Leonhardt, Steffen; Wartzek, Tobias
2015-02-01
Cardiovascular diseases as well as pulmonary oedema can be early diagnosed using vital signs and thoracic bio-impedance. By recording the electrocardiogram (ECG) and the impedance cardiogram (ICG), vital parameters are captured continuously. The aim of this study is the continuous monitoring of ECG and multi-frequency ICG by a mobile system. A mobile measuring system, based on 'low-power' ECG, ICG and an included radio transmission is described. Due to the high component integration, a board size of only 6.5 cm×5 cm could be realized. The measured data can be transmitted via Bluetooth and visualized on a portable monitor. By using energy-efficient hardware, the system can operate for up to 18 hs with a 3 V battery, continuously sending data via Bluetooth. Longer operating times can be realized by decreased transfer rates. The relative error of the impedance measurement was less than 1%. The ECG and ICG measurements allow an approximate calculation of the heart stroke volume. The ECG and the measured impedance showed a high correlation to commercial devices (r=0.83, p<0.05). In addition to commercial devices, the developed system allows a multi-frequency measurement of the thoracic impedance between 5-150 kHz. PMID:25559781
Impedance cardiography for estimating cardiac output during submaximal and maximal work.
Kobayashi, Y; Andoh, Y; Fujinami, T; Nakayama, K; Takada, K; Takeuchi, T; Okamoto, M
1978-09-01
Impedance cardiography was used to estimate cardiac output in 10 men during rest and within 5 s after exercise on a bicycle ergometer, including work up to and including maximal aerobic capacity. An indwelling venous catheter permitted simultaneous sampling of venous blood for observing changes in hematocrit associated with each exercise level. Cardiac output, calculated from a standard equation which assumes a constant value of 150 omega.cm for the electrical resistivity of blood, was compared with corresponding calculations in which blood resistivity was individually determined as a function of hematocrit. It is concluded that many of the discrepancies in the literature related to values for cardiac output obtained during exercise by the impedance method may be inherent in calculations that do not consider the changing electrical resistivity of the blood with a changing hematocrit.
A comparison of systolic time intervals measured by impedance cardiography and carotid pulse tracing
DEFF Research Database (Denmark)
Mehlsen, J; Bonde, J; Rehling, Michael;
1990-01-01
.001) and found that left ventricular ejection times were longer when determined by the carotid technique (p less than 0.01). We found a significant correlation between drug-induced changes in STI-variables measured by the two methods (p less than 0.001). Both methods had a high degree of reproducibility......The purpose of this study was to compare the systolic time intervals (STI) obtained by impedance cardiography and by the conventional carotid technique. This comparison was done with respect to: 1) correlations between variables obtained by the two methods, 2) ability to reflect drug......-induced changes, 3) reliability in terms of reproducibility and 4) heart rate dependency of the variables measured. The study included 25 unmedicated patients with ischaemic heart disease and 36 healthy subjects. We obtained significant correlations between STI-variables measured by the two methods (p less than 0...
Oleksiak, Justyna; Cybulski, Gerard
2014-11-01
The aim of this work was to create a computer program, written in LabVIEW, which enables the visualization and analysis of hemodynamic parameters. It allows the user to import data collected using ReoMonitor, an ambulatory monitoring impedance cardiography (AICG) device. The data include one channel of the ECG and one channel of the first derivative of the impedance signal (dz/dt) sampled at 200Hz and the base impedance signal (Z0) sampled every 8s. The program consist of two parts: a bioscope allowing the presentation of traces (ECG, AICG, Z0) and an analytical portion enabling the detection of characteristic points on the signals and automatic calculation of hemodynamic parameters. The detection of characteristic points in both signals is done automatically, with the option to make manual corrections, which may be necessary to avoid "false positive" recognitions. This application is used to determine the values of basic hemodynamic variables: pre-ejection period (PEP), left ventricular ejection time (LVET), stroke volume (SV), cardiac output (CO), and heart rate (HR). It leaves room for further development of additional features, for both the analysis panel and the data acquisition function.
Yazdanian, Hassan; Mahnam, Amin; Edrisi, Mehdi; Esfahani, Morteza Abdar
2016-01-01
Measurement of the stroke volume (SV) and its changes over time can be very helpful for diagnosis of dysfunctions in the blood circulatory system and monitoring their treatments. Impedance cardiography (ICG) is a simple method of measuring the SV based on changes in the instantaneous mean impedance of the thorax. This method has received much attention in the last two decades because it is noninvasive, easy to be used, and applicable for continuous monitoring of SV as well as other hemodynamic parameters. The aim of this study was to develop a low-cost portable ICG system with high accuracy for monitoring SV. The proposed wireless system uses a tetrapolar configuration to measure the impedance of the thorax at 50 kHz. The system consists of carefully designed precise voltage-controlled current source, biopotential recorder, and demodulator. The measured impedance was analyzed on a computer to determine SV. After evaluating the system's electronic performance, its accuracy was assessed by comparing its measurements with the values obtained from Doppler echocardiography (DE) on 5 participants. The implemented ICG system can noninvasively provide a continuous measure of SV. The signal to noise ratio of the system was measured above 50 dB. The experiments revealed that a strong correlation (r = 0.89) exists between the measurements by the developed system and DE (P measured simply and reliably by the developed system, but more detailed validation studies should be conducted to evaluate the system performance. There is a good promise to upgrade the system to a commercial version domestically for clinical use in the future. PMID:27014612
Directory of Open Access Journals (Sweden)
Juan Carlos Márquez Ruiz
2013-10-01
Full Text Available During the last decades the use of Electrical Bioimpedance (EBI in the medical field has been subject of extensive research, especially since it is an affordable, harmless and non-invasive technology. In some specific applications such as body composition assessment where EBI has proven a good degree of effectiveness and reliability, the use of textile electrodes and measurement garments have shown a good performance and reproducible results. Impedance Cardiography (ICG is another modality of EBI that can benefit from the implementation and use of wearable sensors. ICG technique is based on continuous impedance measurements of a longitudinal segment across the thorax taken at a single frequency. The need for specific electrode placement on the thorax and neck can be easily ensured with the use of a garment with embedded textile electrodes, textrodes. The first step towards the implementation of ICG technology into a garment is to find out if ICG measurements with textile sensors give a good enough quality of the signal to allow the estimation of the fundamental ICG parameters. In this work, the measurement performance of a 2-belt set with incorporated textrodes for thorax and neck was compared against ICG measurements obtained with Ag/AgCl electrodes. The analysis was based on the quality of the fundamental ICG signals (∆Z, dZ/dt and ECG, systolic time intervals and other ICG parameters. The obtained results indicate the feasibility of using textrodes for ICG measurements with consistent measurements and relatively low data dispersion. Thus, enabling the development of measuring garments for ICG measurements.
Directory of Open Access Journals (Sweden)
Donald P Bernstein
2010-01-01
Full Text Available Impedance cardiography (ICG is a branch of bioimpedance pimarily concerned with the determination of left ventricular stroke volume (SV. As implemented, using the transthoracic approach, the technique involves applying a current field longitudinally across a segment of thorax by means of a constant magnitude, high frequency, low amplitude alternating current (AC. By Ohm's Law, the voltage difference measured within the current field is proportional to the electrical impedance Z (Ω. Without ventilatory or cardiac activity, Z is known as the transthoracic, static base impedance Z0. Upon ventricular ejection, a characteristic time dependent cardiac-synchronous pulsatile impedance change is obtained, ΔZ(t, which, when placed electrically in parallel with Z0, constitutes the time-variable total transthoracic impedance Z(t. ΔZ(t represents a dual-element composite waveform, which comprises both the radially-oriented volumetric expansion of and axially-directed forward blood flow within both great thoracic arteries. In its majority, however, ΔZ(t is known to primarily emanate from the ascending aorta. Conceptually, commonly implemented methods assume a volumetric origin for the peak systolic upslope of ΔZ(t, (i.e. dZ/dtmax, with the presumed units of Ω·s-1. A recently introduced method assumes the rapid ejection of forward flowing blood in earliest systole causes significant changes in the velocity-induced blood resistivity variation (Δρb(t, Ωcm·s-1, and it is the peak rate of change of the blood resistivity variation dρb(t/dtmax (Ωcm·s-2 that is the origin of dZ/dtmax. As a consequence of dZ/dtmax peaking in the time domain of peak aortic blood acceleration, dv/dtmax (cm·s-2, it is suggested that dZ/dtmax is an ohmic mean acceleration analog (Ω·s-2 and not a mean flow or velocity surrogate as generally assumed. As conceptualized, the normalized value, dZ/dtmax/Z0, is a dimensionless ohmic mean acceleration equivalent (s-2
Directory of Open Access Journals (Sweden)
Mathur Sharad
2007-01-01
Full Text Available Objective: Vasoconstrictors are one of the therapeutic modalities in the treatment of septic shock. In the present study, we have compared the effects of dopamine and norepinephrine in the treatment of septic shock with pre-defined end-points and continuous non-invasive cardiac output monitoring using impedance cardiography. Design: Randomized controlled trial. Settings: Sixteen-bedded mixed intensive care unit of a tertiary care teaching institution. Materials and Methods: The study included 50 consecutive patients presenting with septic shock and divided randomly into two groups with 25 patients in each group. Group I patients were treated with dopamine and those in Group II were treated with norepinephrine. They were optimized with fluid resuscitation upto CVP>10 cm of H 2 O, packed red cells transfusion upto hematocrit> 30, oxygenation and ventilation upto PaO 2 >60 mmHg before the inotropes were started. The goal of therapy was to achieve and maintain for six hours, all of the following: (1 SBP> 90 mm Hg, (2 SVRI> 1100 dynes.s/cm 5 m 2 , (3 Cardiac Index> 4.0L/min/m 2 , (4 IDO 2 > 550 ml/min/m 2 and (5 IVO 2 > 150 ml/min/m 2 . Measurements: The demographic data, baseline parameters and post-treatment parameters were statistically analyzed by using t-test. Results: The post-treatment parameters were statistically significant showing the superiority of norepinephrine over dopamine in optimization of hemodynamics and patient survival. Significant improvement in systolic blood pressure, heart rate, cardiac index, SVRI, IVO 2 and urine output were found in norepinephrine group than the dopamine group. Dopamine showed a response in 10 out of 25 patients up to a maximum dose of 25 mcg/kg/min while with norepinephrine, 19 patients responded up to a maximum dose of 2.5 mcg/kg/min The hemodynamic parameters were preserved in norepinephrine group with better preservation of organ perfusion and oxygen utilization with maintenance of splanchnic and
Design and evaluation of a portable device for the measurement of bio-impedance cardiography
Shi, Qinghai; Heinig, Andreas; Kanoun, Olfa
2011-01-01
Electrical impedance of biological matter is known as electrical bio-impedance or simply as bio-impedance. Bio-impedance devices are of great value for monitoring the pathological and physiological status of biological tissues in clinical and home environments. The technological progress in instrumentation has significantly contributed to the progress that has been observed during the last past decades in impedance spectroscopy and electrical impedance cardiograph. Although bio-impedance is n...
Variable impedance cardiography waveforms: how to evaluate the preejection period more accurately
Ermishkin, V. V.; Kolesnikov, V. A.; Lukoshkova, E. V.; Mokh, V. P.; Sonina, R. S.; Dupik, N. V.; Boitsov, S. A.
2012-12-01
Impedance method has been successfully applied for left ventricular function assessment during functional tests. The preejection period (PEP), the interval between Q peak in ECG and a specific mark on impedance cardiogram (ICG) which corresponds to aortic valve opening, is an important indicator of the contractility state and its neurogenic control. Accurate identification of ejection onset by ICG is often problematic, especially in the cardiologic patients, due to peculiar waveforms. An essential obstacle is variability of the shape of the ICG waveform during the exercise and subsequent recovery. A promissing solution can be introduction of an additional pulse sensor placed in the nearby region. We tested this idea in 28 healthy subjects and 6 cardiologic patients using a dual-channel impedance cardiograph for simultaneous recording from the aortic and neck regions, and an earlobe photoplethysmograph. Our findings suggest that incidence of abnormal complicated ICG waveforms increases with age. The combination of standard ICG with ear photoplethysmography and/or additional impedance channel significantly improves the efficacy and accuracy of PEP estimation.
Meijer, J.H.; Boesveldt, S.; Elbertse, E.; Berendse, H.W.
2008-01-01
The time difference between the electrocardiogram and impedance cardiogram can be considered as a measure for the time delay between the electrical and mechanical activities of the heart. This time interval, characterized by the pre-ejection period (PEP), is related to the sympathetic autonomous ner
The effect of peripheral resistance on impedance cardiography measurements in the anesthetized dog.
Critchley, Lester A H; Peng, Zhi Y; Fok, Benny S; James, Anthony E
2005-06-01
In the vasodilated and septic patient, the impedance method of measuring cardiac output (CO) may underestimate the true value. In this study, we sought to determine whether impedance CO (COIC) measurements are influenced by total peripheral resistance (TPR). In eight anesthetized and ventilated dogs, a high-precision flowprobe was placed on the ascending aorta, and direct CO was measured (CO flowprobe (COFP)). Mean arterial blood pressure was measured from the femoral artery. Simultaneous COIC measurements were made. TPR (mean arterial blood pressure x 80/COFP) was varied over 1-2 h by using infusions of phenylephrine and adrenaline and inhaled halothane. The bias between methods of CO measurement (COIC-COFP) was calculated and compared with TPR by using correlation and regression analysis. A total of 547 pairs of CO measurements were collected from the 8 dogs as TPR was varied. COFP changed by a mean of 190% (range, 89%-425%), and TPR changed by a mean of 266% (range, 94%-580%) during the experiment. The impedance method underestimated CO when TPR was low and overestimated CO when TPR was high. There was a logarithmic relationship between the CO bias and TPR. Correlation coefficients (r) between the CO bias and TPR ranged from 0.46 to 0.89 (P TPR halved or doubled. This finding explains the poor agreement between COIC and other methods of CO measurement found in validation studies involving critically ill patients.
Assessing cardiac preload by the Initial Systolic Time Interval obtained from impedance cardiography
Directory of Open Access Journals (Sweden)
Jan H Meijer
2010-01-01
Full Text Available The Initial Systolic Time Interval (ISTI, obtained from the electrocardiogram (ECG and impedance cardiogram (ICG, is considered to be a measure for the time delay between the electrical and mechanical activity of the heart and reflects an early active period of the cardiac cycle. The clinical relevance of this time interval is subject of study. This paper presents preliminary results of a pilot study investigating the use of ISTI in evaluating and predicting the circulatory response to fluid administration in patients after coronary artery bypass graft surgery, by comparing ISTI with cardiac output (CO responsiveness. Also the use of the pulse transit time (PTT, earlier recommended for this purpose, is investigated. The results show an inverse relationship between ISTI and CO at all moments of fluid administration and also an inverse relationship between the changes ΔISTI and ΔCO before and after full fluid administration. No relationships between PTT and CO or ΔPTT and ΔCO were found. It is concluded that ISTI is dependent upon preload, and that ISTI has the potential to be used as a clinical parameter assessing preload.
Impedance cardiography using band and regional electrodes in supine, sitting, and during exercise.
Patterson, R P; Wang, L; Raza, S B
1991-05-01
The electrical impedance and its first derivative (dZ/dt) were measured at 100 kHz on 10 normal males in supine, sitting, and during upright bicycle exercise in order to compare the contribution of regional electrodes to the standard band electrode signal and to evaluate the possible use of spot electrodes for stroke volume (SV) measurements. Simultaneous measurements were made from band electrodes placed around the neck and lower thorax and from spot electrodes which recorded signals from the neck, upper thorax, and lower thorax. The results showed that approximately equal parts of the dZ/dt waveform came from the neck and upper thorax with the lower thorax contribution small but providing important features of the band signal. Changing from supine to sitting showed percentage decreases of 35% and 46% for the band and neck signals, respectively, with an increase of 19% for the upper thorax signal. The percentage increases in SV with upright exercise were 34%, 52%, and 24% for the bands, neck, and upper thorax signals, respectively. Band signal is made up of different signals from various regions of the thorax. Its ability to predict correct changes in SV may result from some "lucky" coincidences. The use of regional electrodes will probably not give the same SV information but may be important in measuring regional activities of the central circulation.
Hoekstra, Femke; Martinsen, Ørjan G.; Verdaasdonk, Rudolf M.; Janssen, Thomas W. J.; Meijer, Jan H.
2012-12-01
The Initial Systolic Time Interval (ISTI), obtained from the electrocardiogram and impedance cardiogram, is considered to be a measure for the time delay between the electrical and mechanical activity of the heart. This time delay is influenced by the sympathetic nerve system. Therefore, an observational study was performed in a group of patients (SCI) with spinal cord injuries. The relationship between the ISTI and the total heart cycle (RR-interval) was established by varying the RR-interval using an exercise stimulus to increase the heart rate. The slope of this relationship was observed to be significantly higher in the SCI-group as compared with a control group, although there was no difference in ISTI in the range of common heart rates during the test between the groups. This slope and the ISTI was observed to be significantly different in an acute patient having a recent spinal cord injury at a high level. Because of the variety in injury levels and incompleteness of the injuries further, more specific research is necessary to draw decisive conclusions with respect to the contribution of autonomic nervous control on the ISTI in SCI, although the present observations are notable.
SASSMANNOVÁ, Anna
2007-01-01
Echocardiography is an investigation of heart via scan. This enables to intend the moving and the locality of heart structures via scan pulse waves which are repulsed with acoustic interfaces. Impedance measuring of the thorax hemodynamics is based on changes of electrical impedance. These changes happen mainly because of the heart function. By its rhytmical function the heart periodically changes the conditions of blood flow through all vessels. By this we can explain periodical changes of i...
Wavelet analysis of the impedance cardiogram waveforms
Podtaev, S.; Stepanov, R.; Dumler, A.; Chugainov, S.; Tziberkin, K.
2012-12-01
Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt)max) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.
DEFF Research Database (Denmark)
Kelbaek, H; Svendsen, Jesper Hastrup; Aldershvile, J;
2011-01-01
The stroke volume (SV) was determined by first passage radionuclide cardiography and the left ventricular ejection fraction (LVEF) by multigated radionuclide cardiography in 20 patients with ischemic heart disease. The results were evaluated against those obtained by the invasive dye dilution...... or thermodilution and left ventricular cardioangiographic techniques. In a paired comparison the mean difference between the invasive and radionuclide SV was -1 ml (SED 3.1) with a correlation coefficient of 0.83 (p less than 0.01). Radionuclide LVEF values also correlated well with cardioangiographic measurements...
Bucklar, G B; Kaplan, V; Bloch, K E
2003-05-01
Inductance cardiography (thoracocardiography) non-invasively monitors changes in stroke volume by recording ventricular volume curves with an inductive plethysmographic transducer encircling the chest at the level of the heart. Clinical application of this method has been hampered, as data analysis has not been feasible in real time. Therefore a novel, real-time signal processing technique for inductance cardiography has been developed. Its essential concept consists in performance of multiple tasks by several, logically linked signal processing modules that have access to common databases. Based on these principles, a software application was designed that performs acquisition, display, filtering and ECG-triggered ensemble averaging of inductance signals and separates cardiogenic waveforms from noise related to respiration and other sources. The resulting ventricular volume curves are automatically analysed. Performance of the technique for monitoring cardiac output in real time was compared with thermodilution in four patients in an intensive care unit. The bias (mean difference) among 76 paired thoracocardiographic and thermodilution derived changes in cardiac output was 0%; limits of agreement (+/- 2 SD of the bias) were +/- 25%. It is concluded that the proposed signal processing technique for inductance cardiography holds promise for non-invasive, real-time estimation of changes in cardiac output.
[Evaluation of orthostatic regulation by saddle support test using thoracic impedance].
Gugova, F K; Lapin, V V
2002-01-01
We investigated 21 healthy volunteers (10 males and 11 females, mean age 23 +/- 4 years). All the subjects have undergone two 20 min head-up tilt tests using tilt table "TRI W.G. inc." (USA): the first with footplate support and the second with bicycle saddle. Thoracic electrical impedance was measured using impedance cardiography according to Kubicek et al. The protocols included an initial period of 20 min of supine rest while baseline thoracic impedance, blood pressure and heart rate were recorded and then followed by a tilt to 65 degrees. Changes of impedance were measured at min 1, 2, 3, 5, 7, 10, 15, 20 after the procedure. Women had higher values of thoracic impedance both at rest and during the tilt test than men. The value of impedance of the chest negatively correlated with the body mass index. We suppose that an increase of impedance more than 15% may be related with pathological venous pooling. Thoracic impedance may be used to monitor changes of thoracic fluid volumes with posture and possibly to assess orthostatic regulation. The contribution of leg muscles in orthostatic regulation does not reflect values of thoracic impedance.
[Evaluation of orthostatic regulation by saddle support test using thoracic impedance].
Gugova, F K; Lapin, V V
2002-01-01
We investigated 21 healthy volunteers (10 males and 11 females, mean age 23 +/- 4 years). All the subjects have undergone two 20 min head-up tilt tests using tilt table "TRI W.G. inc." (USA): the first with footplate support and the second with bicycle saddle. Thoracic electrical impedance was measured using impedance cardiography according to Kubicek et al. The protocols included an initial period of 20 min of supine rest while baseline thoracic impedance, blood pressure and heart rate were recorded and then followed by a tilt to 65 degrees. Changes of impedance were measured at min 1, 2, 3, 5, 7, 10, 15, 20 after the procedure. Women had higher values of thoracic impedance both at rest and during the tilt test than men. The value of impedance of the chest negatively correlated with the body mass index. We suppose that an increase of impedance more than 15% may be related with pathological venous pooling. Thoracic impedance may be used to monitor changes of thoracic fluid volumes with posture and possibly to assess orthostatic regulation. The contribution of leg muscles in orthostatic regulation does not reflect values of thoracic impedance. PMID:12152425
International Nuclear Information System (INIS)
Computer assisted diagnosis using analysis of medical images is an area of active research in health informatics. This paper proposes a technique for indication of heart diseases by using information related to shapes of the left ventricle (LV). LV boundaries are tracked from echo-cardiography images taken from LV short axis view, corresponding to two disease conditions viz. dilated cardiomyopathy and hypertrophic cardiomyopathy, and discriminated from the normal condition. The LV shapes are modeled using shape histograms generated by plotting the frequency of normalized radii lengths drawn from the centroid to the periphery, against a specific number of bins. A 3-layer neural network activated by a log-sigmoid function is used to classify the shape histograms into one of the three classes. Experimentations on a dataset of 240 images show recognition accuracies of the order of 80%.
Wakefields and coupling impedances
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. (Superconducting Super Collider Laboratory, 2550 Beckleymeade Ave., Dallas, Texas 75237 (United States))
1995-02-01
After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example. [copyright] 1995 [ital American] [ital Institute] [ital of] [ital Physics
Wakefields and coupling impedances
Kurennoy, Sergey
1995-02-01
After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example.
Impedance model for nanostructures
Directory of Open Access Journals (Sweden)
R. S. Akhmedov
2007-06-01
Full Text Available The application of the impedance model for nanoelectronic quantum-mechanical structures modelling is described. Characteristics illustrating the efficiency of the model are presented.
Energy Technology Data Exchange (ETDEWEB)
Georges, R.; Vernejoul, P. de; Raynaud, C.; Blanchon, P.; Kellershohn, C.; Turiaf, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1961-07-01
The authors used gamma cardiology during the abatement of 16 cases of asthma with a view to detecting heart attacks not otherwise visible with routine methods of examination: clinical, radiological and electro-cardio-graphical. In gamma cardiology, a radioactive indicator is used and its path followed in the cavities of the heart. The method makes it possible to study the circulation in the right heart, the pulmonary crossing, and the left heart, as well as evaluation of the heart-flow. As a result of their investigations the authors, after having discussed the significance of the data obtained with the method, suggest that it is possible by the use of gamma cardiography during the abatement of an asthma attack: 1- To confirm attacks of the right heart which have already been detected by ordinary methods. 2- To confirm the presence of modifications in the recorded curves which suggest, in the case of the left heart, possible attack; such on attack is also indicated, in a small number of cases, by electrocardiography curves. Some considerations are put forward by the authors concerning the physiopathology of attacks on the left heart. (authors) [French] Les auteurs ont fait appel a la gammacardiographie au decours de 16 cas d'etat de mal asthmatique, dans le but d'objectiver des atteintes cardiaques incapables d'etre revelees par les moyens d'exploration de routine: cliniques, radiologiques et electrocardiographiques. La gammacardiographie est un procede qui enregistre a l'aide d'un indicateur radioactif, le trajet de celui-ci dans les cavites cardiaques. Elle permet l'etude de la circulation dans le coeur droit, de la traversee pulmonaire, et le coeur gauche, de meme que le calcul du debit cardiaque. Au terme de leurs investigations, les auteurs apres avoir discute la signification des donnees fournies par la methode admettent que la gammacardiographie objective au secours de l'etat de mal asthmatique: 1- La confirmation de l
Goovaerts, H G; Faes, T J; Raaijmakers, E; Heethaar, R M
1998-11-01
Design considerations and implementation of a multifrequency measuring channel for application in the field of bio-impedance measurement are discussed in this paper. The input amplifier has a differential configuration which is electrically isolated from the remaining circuits. Transformer coupling provides improved common mode rejection when compared to non-isolated input stages. The frequency characteristic of the section between input and demodulator is flat within +/- 0.1 dB between 4 kHz and 1024 kHz. The synchronous demodulator is based on a wideband switched video amplifier. In contrast to commonly used lock--in techniques, the carrier for demodulation is recovered from the input signal by means of a phase-locked loop. This method ensures zero phase shift with respect to the input signal and improves the accuracy of measurement. The system has been developed primarily for thoracic impedance cardiography (TIC) but has also successfully been applied in the field of total body bio-impedance analysis (BIA). At present an electrical impedance tomograph is under development based on the instrumentation described. Results regarding the measurement range and accuracy are given and some recordings of patient data are shown.
Impedance and Collective Effects
Metral, E; Rumolo, R; Herr, W
2013-01-01
This document is part of Subvolume C 'Accelerators and Colliders' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '4 Impedance and Collective Effects' with the content: 4 Impedance and Collective Effects Introduction 4.1 Space Charge 4.2 Wake Fields and Impedances 4.3 Coherent Instabilities 4.4 Landau Damping 4.5 Two-Stream Effects (Electron Cloud and Ions) 4.6 Beam-Beam Effects 4.7 Numerical Modelling
Impedance and component heating
Métral, E; Mounet, N; Pieloni, T; Salvant, B
2015-01-01
The impedance is a complex function of frequency, which represents, for the plane under consideration (longitudinal, horizontal or vertical), the force integrated over the length of an element, from a “source” to a “test” wave, normalized by their charges. In general, the impedance in a given plane is a nonlinear function of the test and source transverse coordinates, but it is most of the time sufficient to consider only the first few linear terms. Impedances can influence the motion of trailing particles, in the longitudinal and in one or both transverse directions, leading to energy loss, beam instabilities, or producing undesirable secondary effects such as excessive heating of sensitive components at or near the chamber wall, called beam-induced RF heating. The LHC performance limitations linked to impedances encountered during the 2010-2012 run are reviewed and the currently expected situation during the HL-LHC era is discussed.
Energy Technology Data Exchange (ETDEWEB)
Zotter, B. [European Organization for Nuclear Research, Geneva (Switzerland)
1996-08-01
This report describes a number of measurements and computations of the impedance of the Large Electron Positron collider LEP at CERN. The work has been performed over several years, together with D. Brandt, K. Cornelis, A. Hofmann, G. Sabbi and many others. The agreement between measurements of single bunch instabilities on the machine and computer simulations is in general excellent and gives confidence in the impedance model used. (author)
Creasy, M. Austin
2016-03-01
Impedance models of pipes can be used to estimate resonant frequencies of standing waves and model acoustic pressure of closed and open ended pipes. Modelling a pipe with impedance methods allows additional variations to the pipe to be included in the overall model as a system. Therefore an actuator can be attached and used to drive the system and the impedance model is able to include the dynamics of the actuator. Exciting the pipe system with a chirp signal allows resonant frequencies to be measured in both the time and frequency domain. The measurements in the time domain are beneficial for introducing undergraduates to resonances without needing an understanding of fast Fourier transforms. This paper also discusses resonant frequencies in open ended pipes and how numerous texts incorrectly approximate the resonant frequencies for this specific pipe system.
Kopp, Joachim; Slatyer, Tracy R; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppress...
DEFF Research Database (Denmark)
Vang, Jakob Rabjerg
potentially play an important role in the energy system of the future. One of the fuel cell technologies, that receives much attention from the Danish scientific community is high temperature proton exchange membrane (HTPEM) fuel cells based on polybenzimidazole (PBI) with phosphoric acid as proton conductor...... cells through experimental studies and mathematical modelling. These studies all revolve around the electrochemical impedance spectroscopy (EIS) characterisation method. EIS is performed by applying a sinusoidal current or voltage signal to the fuel cell and calculating the impedance from the response...
Implantable Impedance Plethysmography
Directory of Open Access Journals (Sweden)
Michael Theodor
2014-08-01
Full Text Available We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term.
Impedance calculation for ferrite inserts
Energy Technology Data Exchange (ETDEWEB)
Breitzmann, S.C.; Lee, S.Y.; /Indiana U.; Ng, K.Y.; /Fermilab
2005-01-01
Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.
Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonst...
Gynecologic electrical impedance tomograph
Korjenevsky, A.; Cherepenin, V.; Trokhanova, O.; Tuykin, T.
2010-04-01
Electrical impedance tomography extends to the new and new areas of the medical diagnostics: lungs, breast, prostate, etc. The feedback from the doctors who use our breast EIT diagnostic system has induced us to develop the 3D electrical impedance imaging device for diagnostics of the cervix of the uterus - gynecologic impedance tomograph (GIT). The device uses the same measuring approach as the breast imaging system: 2D flat array of the electrodes arranged on the probe with handle is placed against the body. Each of the 32 electrodes of the array is connected in turn to the current source while the rest electrodes acquire the potentials on the surface. The current flows through the electrode of the array and returns through the remote electrode placed on the patient's limb. The voltages are measured relative to another remote electrode. The 3D backprojection along equipotential surfaces is used to reconstruct conductivity distribution up to approximately 1 cm in depth. Small number of electrodes enables us to implement real time imaging with a few frames per sec. rate. The device is under initial testing and evaluation of the imaging capabilities and suitability of usage.
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)
1996-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)
Trakic, A; Akhand, M; Wang, H; Mason, D; Liu, F; Wilson, S; Crozier, S
2010-01-01
Studies have shown that blood-flow-induced change in electrical conductivity is of equal importance in assessment of the impedance cardiogram (ICG) as are volumetric changes attributed to the motion of heart, lungs and blood vessels. To better understand the sole effect of time-varying blood conductivity on the spatiotemporal distribution of trans-thoracic electric fields (i.e. ICG), this paper presents a segmented high-resolution (1 mm(3)) thoracic cardiovascular system, in which the time-varying pressures, flows and electrical conductivities of blood in different vessels are evaluated using a set of coupled nonlinear differential equations, red blood cell orientation and cardiac cycle functions. Electric field and voltage simulations are performed using two and four electrode configurations delivering a small alternating electric current to an anatomically realistic and electrically accurate model of modelled human torso. The simulations provide a three-dimensional electric field distribution and show that the time-varying blood conductivity alters the voltage potential difference between the electrodes by a maximum of 0.28% for a cardiac output of about 5 L min(-1). As part of a larger study, it is hoped that this initial model will be useful in providing improved insights into blood-flow-related spatiotemporal electric field variations and assist in the optimal placement of electrodes in impedance cardiography experiments.
Blaskiewicz, M.; Dooling, J.; Dyachkov, M.; Fedotov, A.; Gluckstern, R.; Hahn, H.; Huang, H.; Kurennoy, S.; Linnecar, T.; Shaposhnikova, E.; Stupakov, G.; Toyama, T.; Wang, J. G.; Weng, W. T.; Zhang, S. Y.; Zotter, B.
1999-12-01
The impedance working group was charged to reply to the following 8 questions relevant to the design of high-intensity proton machines such as the SNS or the FNAL driver. These questions were first discussed one by one in the whole group, then each ne of them assigned to one member to summarize. On the lst morning these contributions were publicly read, re-discussed and re-written where required—hence they are not the opinion of a particular person, but rather the averaged opinion of all members of the working group. (AIP)
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Galigekere, Veda Prakash;
2016-01-01
A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance S...... with an example single-switch 400 W dc-dc converter. For the closed-loop control design and stability assessment, a small signal model and its analysis of the proposed network are also presented in brief.......A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance...
Microwave Impedance Measurement for Nanoelectronics
Directory of Open Access Journals (Sweden)
M. Randus
2011-04-01
Full Text Available The rapid progress in nanoelectronics showed an urgent need for microwave measurement of impedances extremely different from the 50Ω reference impedance of measurement instruments. In commonly used methods input impedance or admittance of a device under test (DUT is derived from measured value of its reflection coefficient causing serious accuracy problems for very high and very low impedances due to insufficient sensitivity of the reflection coefficient to impedance of the DUT. This paper brings theoretical description and experimental verification of a method developed especially for measurement of extreme impedances. The method can significantly improve measurement sensitivity and reduce errors caused by the VNA. It is based on subtraction (or addition of a reference reflection coefficient and the reflection coefficient of the DUT by a passive network, amplifying the resulting signal by an amplifier and measuring the amplified signal as a transmission coefficient by a common vector network analyzer (VNA. A suitable calibration technique is also presented.
Optically stimulated differential impedance spectroscopy
Maxey, Lonnie C; Parks, II, James E; Lewis, Sr., Samuel A; Partridge, Jr., William P
2014-02-18
Methods and apparatuses for evaluating a material are described. Embodiments typically involve use of an impedance measurement sensor to measure the impedance of a sample of the material under at least two different states of illumination. The states of illumination may include (a) substantially no optical stimulation, (b) substantial optical stimulation, (c) optical stimulation at a first wavelength of light, (d) optical stimulation at a second wavelength of light, (e) a first level of light intensity, and (f) a second level of light intensity. Typically a difference in impedance between the impedance of the sample at the two states of illumination is measured to determine a characteristic of the material.
DEFF Research Database (Denmark)
Goh, Ailian; Gao, Feng; Loh, Pon Chiang;
2007-01-01
control, and push up the overall system costs. Therefore, alternative topological solutions are of interest, and should preferably be implemented using only passive LC elements and diodes, connected as unique impedance networks. A number of possible network configurations are now investigated...... in this paper, and are respectively named as Z-source, H-source, EZ-source and their respective "inverted" variants. The presented impedance networks can either be used with a traditional voltage-source or current-source inverter, and can either be powered by a voltage or current source. All impedance networks...... the practicalities and performances of the described impedance networks....
Analyzing Impedance Spectroscopy Results
Institute of Scientific and Technical Information of China (English)
Yoed Tsur; Sioma Baltianski
2006-01-01
In this contribution we briefly discuss several analysis techniques for impedance spectroscopy experiments. A number of different approaches, which differ even by the definition of the problem, are used in the literature. Some aimed towards finding an equivalent circuit. Others aimed towards finding directly dielectric properties of the material under an assumed model. Others towards finding distribution of relaxation times, either parametric or point-by point. No matter what the approach is, this will always be an ill-posed problem in the sense that there exist a large number of possible solutions that solve the problem (mathematically) equally well. Therefore some a-priori knowledge about the system must be used. In addition, we should remember that the ultimate goal is to get physical insight about the system.
Impedance source power electronic converters
Liu, Yushan; Ge, Baoming; Blaabjerg, Frede; Ellabban, Omar; Loh, Poh Chiang
2016-01-01
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding control methods. Presents the latest power conversion solutions that aim to advance the role of pow...
Acoustic impedances of ear canals measured by impedance tube
DEFF Research Database (Denmark)
Ciric, Dejan; Hammershøi, Dorte
2007-01-01
During hearing sensitivity tests, the sound field is commonly generated by an earphone placed on a subject ear. One of the factors that can affect the sound transmission in the ear is the acoustic impedance of the ear canal. Its importance is related to the contribution of other elements involved...... locations in an impedance tube. The end of the tube representing the measurement plane is placed at the ear canal entrance. Thus, the impedance seen from the entrance inward is measured on 25 subjects. Most subjects participated in the previous measurement of the ratio between the pressures at the open...
Richardson, John G.
2009-11-17
An impedance estimation method includes measuring three or more impedances of an object having a periphery using three or more probes coupled to the periphery. The three or more impedance measurements are made at a first frequency. Three or more additional impedance measurements of the object are made using the three or more probes. The three or more additional impedance measurements are made at a second frequency different from the first frequency. An impedance of the object at a point within the periphery is estimated based on the impedance measurements and the additional impedance measurements.
IMPEDANCE CHARACTERISTICS OF POLYFURAN FILMS
Institute of Scientific and Technical Information of China (English)
Liang Li; Xiao-bo Wan; Gi Xue
2002-01-01
Electrochemical impedance spectroscopy (EIS) was first used for the characterization of polyfuran (PFu) films that had been formed electrochemically on an Au electrode. The polyfuran was measured in high oxidation state, intermediate oxidation state and reduction state, respectively. As the oxidation level is increased, the ionic conductivity of PFu/BF4-increases. And impedance studies on PFu show that the anion BF4- appears to be mobile with a high diffusion coefficient of approximately 10-8 cm2 @ s-1.
[Monitoring cervical dilatation by impedance].
Salvat, J; Lassen, M; Sauze, C; Baud, S; Salvat, F
1992-01-01
Several different physics procedures have been tried to mechanize the recording of partograms. Can a measure of impedance of tissue Z using potential difference V, according to Ohm's law V = Z1, and 1 is a constant, be correlated with a measure of cervical dilatation using vaginal examination? This was our hypothesis. The tissue impedance meter was made to our design and applied according to a bipolar procedure. Our work was carried out on 28 patients. 10 patients were registered before labour started in order to test the apparatus and to record the impedance variations without labour taking place, and 18 patients were registered in labour to see whether there was any correlation. The level of impedance in the cervix without labour was 302.7 Ohms with a deviation of 8.2. Using student's t tests it was found that there was a significant correlation (p less than 0.001) in four measurements between the impedance measure and measures obtained by extrapolating the degrees of dilatation calculated from vaginal examination. This is a preliminary study in which we have defined the conditions that are necessary to confirm these first results and to further develop the method. PMID:1401774
Report of the SSC impedance workshop
Energy Technology Data Exchange (ETDEWEB)
NONE
1985-10-28
This workshop focused attention on the transverse, single-bunch instability and the detailed analysis of the broadband impedance which would drive it. Issues discussed included: (1) single bunch stability -- impact of impedance frequency shape, coupled-mode vs. fast blowup regimes, possible stopband structure; (2) numerical estimates of transverse impedance of inner bellows and sliding contact shielded bellows; (3) analytic estimates of pickup and kicker impedance contributions; and (4) feasibility studies of wire and beam measurements of component impedance.
Transverse Impedance of LHC Collimators
Métral, E; Assmann, Ralph Wolfgang; Boccardi, A; Bracco, C; Bohl, T; Caspers, Friedhelm; Gasior, M; Jones, O R; Kasinski, K; Kroyer, T; Redaelli, S; Robert-Demolaize, R; Roncarolo, F; Rumolo, G; Salvant, B; Steinhagen, R; Weiler, T; Zimmermann, F
2007-01-01
The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
Definition of the characteristic impedance
Institute of Scientific and Technical Information of China (English)
徐云生; Abbas Sayed OMAR
1996-01-01
Currently available definitions of the characteristic impedance are ambiguous andior inaccurate.A general definition,based on the description of discontinuities between adjacent waveguides,is given.This definition is accurate and independent of the structure concerned.So it can be applied to the design of passive components in any type of transmission lines.Using this definition,a given structure can be uniquely characterized,but the absolute value of the characteristic impedance has no sense any more.As an example,the design of a microstrip impedance transformer using this new definition is presented.Numerical results using the mode-matching method prove the accuracy of the theory.
Hybrid-Source Impedance Networks
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang;
2010-01-01
Hybrid-source impedance networks have attracted attention among researchers because of their flexibility in performing buck-boost energy conversion. To date, three distinct types of impedance networks can be summarized for implementing voltage-type inverters with another three types summarized...... for current-type inverters. These impedance networks can in principle be combined into two generic network entities, before multiple of them can further be connected together by applying any of the two proposed generalized cascading concepts. The resulting two-level and three-level inverters implemented using...... the cascaded networks would have a higher output voltage gain and other unique advantages that currently have not been investigated yet. It is anticipated that these advantages would help the formed inverters find applications in photovoltaic and other renewable systems, where a high voltage gain is usually...
Impedances of Laminated Vacuum Chambers
Energy Technology Data Exchange (ETDEWEB)
Burov, A.; Lebedev, V.; /Fermilab
2011-06-22
First publications on impedance of laminated vacuum chambers are related to early 70s: those are of S. C. Snowdon [1] and of A. G. Ruggiero [2]; fifteen years later, a revision paper of R. Gluckstern appeared [3]. All the publications were presented as Fermilab preprints, and there is no surprise in that: the Fermilab Booster has its laminated magnets open to the beam. Being in a reasonable mutual agreement, these publications were all devoted to the longitudinal impedance of round vacuum chambers. The transverse impedance and the flat geometry case were addressed in more recent paper of K. Y. Ng [4]. The latest calculations of A. Macridin et al. [5] revealed some disagreement with Ref. [4]; this fact stimulated us to get our own results on that matter. Longitudinal and transverse impendances are derived for round and flat laminated vacuum chambers. Results of this paper agree with Ref. [5].
Short-circuit impedance measurement
DEFF Research Database (Denmark)
Pedersen, Knud Ole Helgesen; Nielsen, Arne Hejde; Poulsen, Niels Kjølstad
2003-01-01
Methods for estimating the short-circuit impedance in the power grid are investigated for various voltage levels and situations. The short-circuit impedance is measured, preferably from naturally occurring load changes in the grid, and it is shown that such a measurement system faces different...... kinds of problems at different locations in the grid. This means that the best measurement methodology changes depending on the location in the grid. Three typical examples with different measurement problems at 400 kV, 132 kV and 400 V voltage level are discussed....
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Loh, Poh Chiang; Blaabjerg, Frede;
2014-01-01
This letter introduces a new versatile Y-shaped impedance network for realizing converters that demand a very high-voltage gain, while using a small duty ratio. To achieve that, the proposed network uses a tightly coupled transformer with three windings, whose obtained gain is presently not matched...... by existing networks operated at the same duty ratio. The proposed impedance network also has more degrees of freedom for varying its gain, and hence, more design freedom for meeting requirements demanded from it. This capability has been demonstrated by mathematical derivation, and proven in experiment...
Input impedance characteristics of microstrip structures
Directory of Open Access Journals (Sweden)
A. I. Nazarko
2015-06-01
Full Text Available Introduction. Electromagnetic crystals (EC and EC-inhomogeneities are one of the main directions of microstrip devices development. In the article the input impedance characteristics of EC- and traditional microstrip inhomogeneities and filter based on EC-inhomogeneities are investigated. Transmission coefficient characteristics. Transmission coefficient characteristics of low impedance EC- and traditional inhomogeneities are considered. Characteristics are calculated in the software package Microwave Studio. It is shown that the efficiency of EC-inhomogeneity is much higher. Input impedance characteristics of low impedance inhomogeneities. Dependences of input impedance active and reactive parts of EC- and traditional inhomogeneities are given. Dependences of the active part illustrate significant low impedance transformation of nominal impedance. The conditions of impedance matching of structure and input medium are set. Input impedance characteristics of high impedance inhomogeneities. Input impedance characteristics of high impedance EC- and traditional inhomogeneities are considered. It was shown that the band of transformation by high impedance inhomogeneities is much narrower than one by low impedance inhomogeneities. Characteristics of the reflection coefficient of inhomogeneities are presented. Input impedance characteristics of narrowband filter. The structure of narrowband filter based on the scheme of Fabry-Perot resonator is presented. The structure of the filter is fulfilled by high impedance EC-inhomogeneities as a reflectors. Experimental and theoretical amplitude-frequency characteristics of the filter are presented. Input impedance characteristics of the filter are shown. Conclusions. Input impedance characteristics of the structure allow to analyse its wave properties, especially resonant. EC-inhomogeneity compared with traditional microstrip provide substantially more significant transformation of the the input impedance.
The Aberdeen Impedance Imaging System.
Kulkarni, V; Hutchison, J M; Mallard, J R
1989-01-01
The Aberdeen Impedance Imaging System is designed to reconstruct 2 dimensional images of the average distribution of the amplitude and phase of the complex impedance within a 3 dimensional region. The system uses the four electrode technique in a 16 electrode split-array. The system hardware consists of task-orientated electronic modules for: driving a constant current, multiplexing the current drive, demultiplexing peripheral voltages, differential amplification, phase sensitive detection and low-pass filtration, digitisation with a 14 bit analog to digital converter (ADC), and -control logic for the ADC and multiplexors. A BBC microprocessor (Master series), initiates a controlled sequence for the collection of a number of data sets which are averaged and stored on disk. Image reconstruction is by a process of convolution-backprojection similar to the fan-beam reconstruction of computerised tomography and is also known as Equipotential Backprojection. In imaging impedance changes associated with fracture healing the changes may be large enough to allow retrieval of both the amplitude and phase of the complex impedance. Sequential imaging of these changes would necessitate monitoring electronic and electrode drift by imaging an equivalent region of the contralateral limb. Differential images could be retrieved when the image of the normal limb is the image template. Better characterisation of tissues would necessitate a cleaner retrieval of the quadrature signal. PMID:2742979
Small Signal Loudspeaker Impedance Emulator
DEFF Research Database (Denmark)
Iversen, Niels Elkjær; Knott, Arnold
2014-01-01
from driver to driver. Therefore, a loudspeaker emulator capable of adjusting its impedance to that of a given driver is desired for measurement purposes. This paper proposes a loudspeaker emulator circuit for small signals. Simulations and experimental results are compared and show that it is possible...
Beam Coupling Impedances of Small Discontinuities
Kurennoy, S S
2000-01-01
A general derivation of the beam coupling impedances produced by small discontinuities on the wall of the vacuum chamber of an accelerator is reviewed. A collection of analytical formulas for the impedances of small obstacles is presented.
Reducing the SPS Machine Impedance
Collier, Paul; Guinand, R; Jiménez, J M; Rizzo, A; Spinks, Alan; Weiss, K
2002-01-01
The SPS as LHC Injector project has been working for some time to prepare the SPS for its role as final injector for the LHC. This included major work related to injection, acceleration, extraction and beam instrumentation for the LHC beams [1]. Measurements carried out with the high brightness LHC beam showed that a major improvement of the machine impedance would also be necessary [2]. In addition to removing all lepton related components (once LEP operation ended in 2000), the decision was made to shield the vacuum system pumping port cavities. These accidental cavities had been identified as having characteristic frequencies in the 1-1.5GHz range. Since the SPS vacuum system contains roughly 1000 of these cavities, they constitute a major fraction of the machine impedance. As removal of the ports and associated bellows is not possible, transition shields (PPS) had to be designed to insert within the pumping port cavities.
Tapping mode microwave impedance microscopy
Lai, K.
2009-01-01
We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results. © 2009 American Institute of Physics.
A spatial impedance controller for robotic manipulation
Fasse, Ernest D.; Broenink, Jan F.
1997-01-01
Mechanical impedance is the dynamic generalization of stiffness, and determines interactive behavior by definition. Although the argument for explicitly controlling impedance is strong, impedance control has had only a modest impact on robotic manipulator control practice. This is due in part to the
A compact broadband nonsynchronous noncommensurate impedance transformer
DEFF Research Database (Denmark)
Zhurbenko, Vitaliy; Kim, Kseniya; Narenda, Kumar
2012-01-01
Nonsynchronous noncommensurate impedance transformers consist of a combination of high‐ and low‐impedance transmission lines. High‐impedance lines have narrow tracks in strip and microstrip technology, which allows for high flexibility and miniaturization of the layout in comparison to the tradit......Nonsynchronous noncommensurate impedance transformers consist of a combination of high‐ and low‐impedance transmission lines. High‐impedance lines have narrow tracks in strip and microstrip technology, which allows for high flexibility and miniaturization of the layout in comparison...... to the traditional tapered line transformers. This flexibility of the broadband nonsynchronous noncommensurate impedance transformers is experimentally demonstrated in this article allowing the length reduction by almost three times. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1832–1835, 2012; View...
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S.
1995-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impendance. This paper discusses three aspects of broadband impendance modeling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f cavity. The last is a discussion of requirements for the mathematical form of an impendance which follow from the general properties of impendances.
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2002-08-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
Impedance spectroscopy of food mycotoxins
Bilyy, Oleksandr I.; Yaremyk, Roman Ya.; Kotsyumbas, Ihor Ya.; Kotsyumbas, Halyna I.
2012-01-01
A new analytical method of high-selective detection of mycotoxins in food and feed are considered. A method is based on optical registration the changes of conduct of the electric polarized bacterial agents in solution at the action of the external gradient electric fields. Measuring are conducted in integrated electrode-optical cuvette of the special construction, which provides the photometric analysis of forward motion of the objects registration in liquid solution under act of the enclosed electric field and simultaneous registration of kinetics of change of electrical impedance parameters solution and electrode system.
Spheromak Impedance and Current Amplification
Energy Technology Data Exchange (ETDEWEB)
Fowler, T K; Hua, D D; Stallard, B W
2002-01-31
It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, {tau}{sub REC}, which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI{sub TOR}{sup 2}/dt {approx} I{sup 2}/{tau}{sub REC} - I{sub TOR}{sup 2}/{tau}{sub closed} where I is the gun current, I{sub TOR} is the spheromak toroidal current and {tau}{sub CLOSED} is the ohmic decay time of the spheromak. Achieving high current amplification, I{sub TOR} >> I, requires {tau}{sub REC} <<{tau}{sub CLOSED}. For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that {tau}{sub REC} actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B {proportional_to} I, or I{sub TOR} {approx} I. Program implications are discussed.
Pumping slots: impedances and power losses
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. [Maryland Univ., College Park, MD (United States). Dept. of Physics
1996-08-01
Contributions of pumping slots to the beam coupling impedances and power losses in a B-factory ring are considered. While their leading contribution is to the inductive impedance, for high-intensity machines with short bunches like e{sup +}e{sup -} B-factories the real part of the impedance and related loss factors are also important. Using an analytical approach we calculate the coupling impedances and loss factors due to slots in a ring with an arbitrary cross section of the vacuum chamber. Effects of the slot tilt on the beam impedance are also considered, and restrictions on the tilt angle are derived from limitations on the impedance increase. The power leakage through the slots is discussed briefly. The results are applied to the KEK B-factory. (author)
High frequency impedances in European XFEL
Energy Technology Data Exchange (ETDEWEB)
Dohlus, Martin; Zagorodnov, Igor; Zagorodnova, Olga
2010-06-15
The method of the optical approximation is used to estimate the high frequency impedances of different vacuum chamber transitions of the European XFEL beam line. The approximations of the longitudinal impedances are obtained in terms of simple one-dimensional integrals. The transverse impedances are written in analytical closed form. The analytical results are compared with the results obtained by numerical solution of Maxwell's equations. (orig.)
Wave impedance retrieving via Bloch modes analysis
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, S.; Sukhorukov, A.;
2011-01-01
The main bottleneck in the restoration of electromagnetic effective parameters is connected to the impedance retrieving. The S-parameters method gives the input (Bloch) impedance, which, being then used for permittivity and permeability determination, causes some fundamental physics prin......-ciples violation, like antiresonance behaviour with Im(ε) fundamental) Bloch mode. Then it is possible to determine the Bloch and wave impedances by the surface and volume aver-aging of the electromagnetic field...
Lorentz Force Electrical Impedance Tomography
Grasland-Mongrain, Pol; Chapelon, Jean-Yves; Lafon, Cyril
2014-01-01
This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers...
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede;
2014-01-01
This paper introduces a Y-shaped impedance network for realizing converters that demand a high voltage gain while using a small duty ratio. To achieve that, the proposed network uses a tightly coupled transformer with three windings, whose obtained gain is presently not matched by existing networks...... operated at the same duty ratio. This capability has been demonstrated by mathematical derivation for the proposed network in comparison with other recently reported networks. To further prove the network performance, a single-switch dc-dc converter has been implemented with the network, before testing...... it experimentally. The results obtained clearly verify the network performance in addition to its higher power density that can generally be achieved by coupled magnetics....
de Sitter, A; Verdaasdonk, R M; Faes, T J C
2016-09-01
Impedance cardiography (ICG) is a method to evaluate cardiac-stroke volume and cardiac-output by measuring the cardiac-synchronous changes in the dynamic trans-thoracic electrical impedance (ΔZ). Clinical evaluations on the accuracy of ICG showed varying results. Consequently, the classic assumption in ICG-the aorta as a main source of ΔZ-is questioned and subsequently investigated in simulation studies using mathematical models of the electrical resistivity of the human body. The aim is to review the consensus in mathematical modelling studies that investigate the origin of the ΔZ as measured in ICG. In a systematic literature search, studies were identified and surveyed with reference to characteristics, such as included organs and their resistivity and geometries, electrode positions and calculation of ΔZ, to review the consensus between mathematical modelling studies that investigate the origin of the ΔZ as measured in ICG. Thirteen papers showed considerable variation in the model's characteristics with varying or contradicting outcomes for the ΔZ 's origin. For instance, 11 studies excluded perfused muscle tissue, implying implicitly their insignificance, while 3 other studies included muscle tissue and indicated it as the most important origin of ΔZ. In conclusion, the reviewed papers show a lack of consensus with respect to both the modelled characteristics as well as the model outcomes and, as a result, these studies failed to settle the controversy on ΔZ 's origin. Recommendations have been added to improve future mathematical model studies.
Possibilities of electrical impedance tomography in gynecology
V, Trokhanova O.; A, Chijova Y.; B, Okhapkin M.; V, Korjenevsky A.; S, Tuykin T.
2013-04-01
The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.
Esophageal Impedance Monitoring: Clinical Pearls and Pitfalls.
Ravi, Karthik; Katzka, David A
2016-09-01
The development of intraluminal esophageal impedance monitoring has improved our ability to detect and measure gastroesophageal reflux without dependence on acid content. This ability to detect previously unrecognized weak or nonacid reflux episodes has had important clinical implications in the diagnosis and management of gastroesophageal reflux disease (GERD). In addition, with the ability to assess bolus transit within the esophageal lumen, impedance monitoring has enhanced the recognition and characterization of esophageal motility disorders in patients with nonobstructive dysphagia. The assessment of the intraluminal movement of gas and liquid has also been proven to be of diagnostic value in conditions such as rumination syndrome and excessive belching. Further, alternative applications of impedance monitoring, such as the measurement of mucosal impedance, have provided novel insights into assessing esophageal mucosal integrity changes as a consequence of inflammatory change. Future applications for esophageal impedance monitoring also hold promise in esophageal conditions other than GERD. However, despite all of the clinical benefits afforded by esophageal impedance monitoring, important clinical and technical shortcomings limit its diagnostic value and must be considered when interpreting study results. Overinterpretation of studies or application of impedance monitoring in patients can have deleterious clinical implications. This review will highlight the clinical benefits and limitations of esophageal impedance monitoring and provide clinical pearls and pitfalls associated with this technology. PMID:27325223
Active impedance matching of complex structural systems
Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.
1991-01-01
Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.
Impedance of a slotted-pipe kicker
Energy Technology Data Exchange (ETDEWEB)
Feng Zhou [Academia Sinica, Beijing, BJ (China). Inst. of High Energy Physics
1996-08-01
This paper introduces the principle of a new slotted kicker simply, which is made by using vacuum pipe itself with proper slits as current conductors, and then, presents a rough estimation of its longitudinal and transverse impedance, respectively. Calculation shows that its impedance is reduced significantly compared to our present air-coil kicker. (author)
Experimental Verification of Acoustic Impedance Inversion
Institute of Scientific and Technical Information of China (English)
郭永刚; 王宁; 林俊轩
2003-01-01
Well controlled model experiments were carried out to verify acoustic impedance inversion scheme, and different methods of extracting impulse responses were investigated by practical data. The acoustic impedance profiles reconstructed from impulse responses are in good agreement with the measured value and theoretical value.
Far-infrared embedding impedance measurements
Neikirk, D. P.; Rutledge, D. B.
1984-01-01
A technique which allows the measurement of detector embedding impedance has been developed. By using a bismuth microbolometer as a variable resistance load the impedance of one element in a bow-tie antenna array operating at 94 GHz was inferred. The technique is frequency insensitive, and could be used throughout the far-infrared.
Estimating the short-circuit impedance
DEFF Research Database (Denmark)
Nielsen, Arne Hejde; Pedersen, Knud Ole Helgesen; Poulsen, Niels Kjølstad
1997-01-01
A method for establishing a complex value of the short-circuit impedance from naturally occurring variations in voltage and current is discussed. It is the symmetrical three phase impedance at the fundamental grid frequency there is looked for. The positive sequence components in voltage and curr...
Fractional Order Element Based Impedance Matching
Radwan, Ahmed Gomaa
2014-06-24
Disclosed are various embodiments of methods and systems related to fractional order element based impedance matching. In one embodiment, a method includes aligning a traditional Smith chart (|.alpha.|=1) with a fractional order Smith chart (|.alpha.|.noteq.1). A load impedance is located on the traditional Smith chart and projected onto the fractional order Smith chart. A fractional order matching element is determined by transitioning along a matching circle of the fractional order Smith chart based at least in part upon characteristic line impedance. In another embodiment, a system includes a fractional order impedance matching application executed in a computing device. The fractional order impedance matching application includes logic that obtains a first set of Smith chart coordinates at a first order, determines a second set of Smith chart coordinates at a second order, and determines a fractional order matching element from the second set of Smith chart coordinates.
Identification of irradiated potatoes by impedance measurements
International Nuclear Information System (INIS)
Measuring the impedance was found to be a highly reliable and practical technique for identifying irradiated potatoes. Impedance was measured by puncturing a potato tuber with a steel electrode and passing a 3 -- 5 mA alternating current through it. Three parameters were determined: Z0/Z180 (impedance ratio at 5 kHz, 0 to 180 seconds after puncturing), Z sub(50k)/Z sub(0.5k) (impedance ratio at 50 kHz to 0.5 kHz) and Z sub(50k)/Z sub(5k) (impedance ratio at 50 kHz to 5 kHz). Among these, parameter Z sub(50k)/Z sub(5k) was the most favourable index. The technique allowed not only differentiation between unirradiated and irradiated potatoes but an estimation of the irradiation dose for up to six months after irradiation, independent of the potato storage condition. (author)
Rotor damage detection by using piezoelectric impedance
Qin, Y.; Tao, Y.; Mao, Y. F.
2016-04-01
Rotor is a core component of rotary machinery. Once the rotor has the damage, it may lead to a major accident. Thus the quantitative rotor damage detection method based on piezoelectric impedance is studied in this paper. With the governing equation of piezoelectric transducer (PZT) in a cylindrical coordinate, the displacement along the radius direction is derived. The charge of PZT is calculated by the electric displacement. Then, by the use of the obtained displacement and charge, an analytic piezoelectric impedance model of the rotor is built. Given the circular boundary condition of a rotor, annular elements are used as the analyzed objects and spectral element method is used to set up the damage detection model. The Electro-Mechanical (E/M) coupled impedance expression of an undamaged rotor is deduced with the application of a low-cost impedance test circuit. A Taylor expansion method is used to obtain the approximate E/M coupled impedance expression for the damaged rotor. After obtaining the difference between the undamaged and damaged rotor impedance, a rotor damage detection method is proposed. This method can directly calculate the change of bending stiffness of the structural elements, it follows that the rotor damage can be effectively detected. Finally, a preset damage configuration is used for the numerical simulation. The result shows that the quantitative damage detection algorithm based on spectral element method and piezoelectric impedance proposed in this paper can identify the location and the severity of the damaged rotor accurately.
Measurements of electrical impedance of biomedical objects.
Frączek, Marcin; Kręcicki, Tomasz; Moron, Zbigniew; Krzywaźnia, Adam; Ociepka, Janusz; Rucki, Zbigniew; Szczepanik, Zdzisław
2016-01-01
Some basic problems related to measurements of electrical impedance of biological objects (bioimpedance) have been presented in this paper. Particularly problems arising from impedance occurring at the sensor-tissue interface (interfacial impedances) in contact measuring methods have been discussed. The influence of finite values of impedances of the current source and voltage measuring device has also been taken into consideration. A model of the impedance sensor for the four-electrode measurement method containing the interfacial, source and measuring device impedances has been given and its frequency characteristics obtained by the computer simulation have been presented. The influence of these impedances on the shape of frequency characteristic of the sensor model has been discussed. Measurements of bioimpedance of healthy and anomalous soft tissues have been described. Some experimental results, particularly the frequency characteristics of bioimpedance, have been shown. The presented results of measurement show that bioimpedance can be a valuable source of information about the tissues, so measurement of bioimpedance can be a useful supplement to other medical diagnostic methods. PMID:27151250
Tracking of electrochemical impedance of batteries
Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.
2016-04-01
This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.
SPATIAL VARIABILITY OF PEDOZEMS MECHANICAL IMPEDANCE
Directory of Open Access Journals (Sweden)
Zhukov A.V.
2013-04-01
Full Text Available We studied the spatial variability of pedozem mechanical impedance in ResearchRemediation Center of the Dnipropetrovsk State Agrarian University in Ordzhonikidze. Thestatistical distribution of the soil mechanical impedance within the studied area is characterized by deviation from the normal law in 0–10 and 30–50 cm layers from the surface. 2D and 3D modeling shows the structural design of the soil as locations of high mechanical impedance which found in the soils with less hardness.
Universal impedance fluctuations in wave chaotic systems.
Hemmady, Sameer; Zheng, Xing; Ott, Edward; Antonsen, Thomas M; Anlage, Steven M
2005-01-14
We experimentally investigate theoretical predictions of universal impedance fluctuations in wave chaotic systems using a microwave analog of a quantum chaotic infinite square well potential. We emphasize the use of the radiation impedance to remove the nonuniversal effects of the particular coupling between the outside world and the scatterer. Specific predictions that we test include the probability density functions (PDFs) of the real and imaginary parts of the universal impedance, the equality of the variances of these PDFs, and the dependence of these PDFs on a single loss parameter.
Impedance Spectroscopy of Dielectrics and Electronic Conductors
DEFF Research Database (Denmark)
Bonanos, Nikolaos; Pissis, Polycarpos; Macdonald, J. Ross
2013-01-01
Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property......, and procedures for the correction of measurement errors. The applications of impedance spectroscopy are illustrated with examples from electroceramics and polymer-based dielectric systems. The way in which the technique is applied to the two classes of materials is compared with reference to the different models...
New Regularization Method in Electrical Impedance Tomography
Institute of Scientific and Technical Information of China (English)
侯卫东; 莫玉龙
2002-01-01
Image reconstruction in elecrical impedance tomography(EIT)is a highly ill-posed inverse problem,Regularization techniques must be used in order to solve the problem,In this paper,a new regularization method based on the spatial filtering theory is proposed.The new regularized reconstruction for EIT is independent of the estimation of impedance distribution,so it can be implemented more easily than the maxiumum a posteriori(MAP) method.The regularization level in our proposed method varies spatially so as to be suited to the correlation character of the object's impedance distribution.We implemented our regularization method with two dimensional computer simulations.The experimental results indicate that the quality of the reconstructed impedance images with the descibed regularization method based on spatial filtering theory is better than that with Tikhonov method.
Impedance and collective effects in the LHC
Energy Technology Data Exchange (ETDEWEB)
Gareyte, J. [European Organization for Nuclear Research, Geneva (Switzerland)
1996-08-01
After a review of the main LHC parameters, and a brief description of the RF and vacuum systems, the coupling impedances of the main machine elements are given, as well as the resulting thresholds for instabilities. (author)
Impedance feedback control for scanning electrochemical microscopy.
Alpuche-Aviles, M A; Wipf, D O
2001-10-15
A new constant-distance imaging method based on the relationship between tip impedance and tip-substrate separation has been developed for the scanning electrochemical microscope. The tip impedance is monitored by application of a high-frequency ac voltage bias between the tip and auxiliary electrode. The high-frequency ac current is easily separated from the dc-level faradaic electrochemistry with a simple RC filter, which allows impedance measurements during feedback or generation/collection experiments. By employing a piezo-based feedback controller, we are able to maintain the impedance at a constant value and, thus, maintain a constant tip-substrate separation. Application of the method to feedback and generation/collection experiments with tip electrodes as small as 2 microm is presented. PMID:11681463
Interpretation of faradaic impedance for Corrosion monitoring
Energy Technology Data Exchange (ETDEWEB)
Itagaki, M.; Taya, A.; Imamura, M.; Saruwatari, R.; Watanabe, K. [Science University of Tokyo, Chiba (Japan)
2004-02-15
A polarization resistance is generally used to estimate the corrosion rate in the corrosion monitoring by an electrochemical impedance method. When the Faradaic impedance has a time constant due to the reaction intermediate, the electrochemical impedance describes more than one loop on the complex plane. For example, the electrochemical impedance of iron in acidic solution shows capacitive and inductive loops on the complex plane. In this case, the charge transfer resistance and the polarization resistance are determined at middle and low frequency ranges, respectively. Which should be selected for corrosion resistance in corrosion monitoring, the charge transfer resistance or the polarization resistance? In the present paper, the above-mentioned question is examined theoretically and experimentally
Electrochemical Impedance Studies of SOFC Cathodes
DEFF Research Database (Denmark)
Hjelm, Johan; Søgaard, Martin; Wandel, Marie;
2007-01-01
Mixed ion- and electron-conducting composite electrodes consisting of doped ceria and perovskite have been studied by electrochemical impedance spectroscopy (EIS) at different temperatures and oxygen partial pressures. This paper aims to describe the different contributions to the polarisation...
Thermal Impedance of Rectangular Microwave Oven Linings
Institute of Scientific and Technical Information of China (English)
SHIShang－zhao; XUFu－qiu; 等
1996-01-01
Amodel was preseted for calcultaing the thermal impedance of the insulation and refractory linings of rectangular microwave ovens,of which the oven cavity's dimensions are relatively small,while the linings re relatively thick.
Modeling degradation in SOEC impedance spectra
DEFF Research Database (Denmark)
Jensen, Søren Højgaard; Hauch, Anne; Knibbe, Ruth;
2013-01-01
Solid oxide cell (SOC) performance is limited by various processes. One way to investigate these processes is by electrochemical impedance spectroscopy. In order to quantify and characterize the processes, an equivalent circuit can be used to model the SOC impedance spectra (IS). Unfortunately......, the optimal equivalent circuit is often unknown and to complicate matters further, several processes contribute to the SOC impedance - making detailed process characterization difficult. In this work we analyze and model a series of IS measured during steam electrolysis operation of an SOC. During testing......, degradation is only observed in the Ni/YSZ electrode and not in the electrolyte or the LSM/YSZ electrode. A batch fit of the differences between the IS shows that a modified Gerischer element provides a better fit to the Ni/YSZ electrode impedance than the frequently used RQ element - albeit neither...
Directory of Open Access Journals (Sweden)
Dejan Krizaj
2012-10-01
Full Text Available Electrical impedance measurements of the suspensions have to take into account the double layer impedance that is due to a very thin charged layer formed at the electrode-electrolite interface. A dedicated measuring cell that enables variation of the distance between the electrodes was developed for investigation of electrical properties of suspensions using two electrode impedance measurements. By varying the distance between the electrodes it is possible to separate the double layer and the suspension impedance from the measured data. From measured and extracted impedances electrical lumped models have been developed. The error of non inclusion of the double layer impedance has been analyzed. The error depends on the frequency of the measurements as well as on the distance between the electrodes.
CSR Impedance for Non-Ultrarelativistic Beams
Energy Technology Data Exchange (ETDEWEB)
Li, Rui [Jefferson Lab., Newport News, VA (United States); Tsai, Cheng Y. [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Jefferson Lab., Newport News, VA (United States)
2015-09-01
For the analysis of the coherent synchrotron radiation (CSR)-induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.
Analysis of formulas used in coupling impedance coaxial-wire measurements for distributed impedances
International Nuclear Information System (INIS)
In this paper the authors study the validity of coupling impedance bench measurements for distributed impedances, comparing the commonly used log formula to the result obtained applying a modified version of Bethe's theory of diffraction to a long slot in a coaxial beam pipe. The equations found provide a quantitative expression for the influence of the wire thickness used in the measurement of the real and imaginary part of the longitudinal impedance. The precision achievable in an actual measurement is therefore discussed. The method presented has also been applied in the presence of lumped impedances
Electromagnetic Wave Scattering By the Coated Impedance Cylinder
Directory of Open Access Journals (Sweden)
V.I. Vyunnik
2010-01-01
Full Text Available In this work the boundary conditions for the impedance circular cylinder coated by a low contrast dielectric thin layer are derived. Expression for the reduced impedance of the cylinder is obtained. Conditions and applicability limits of the proposed approach are defined. Influence of the coating impedance on the reduced impedance of the cylinder is investigated.
VISUALIZATION OF BIOLOGICAL TISSUE IMPEDANCE PARAMETERS
Directory of Open Access Journals (Sweden)
V. I. Bankov
2016-01-01
Full Text Available Objective. Investigation the opportunity for measurement of biological tissue impedance to visualize its parameters.Materials and methods. Studies were undertook on the experimental facility, consists of registrating measuring cell, constructed from flat inductors system, formed in oscillatory circuit, herewith investigated biological tissue is the part of this oscillatory circuit. An excitation of oscillatory circuit fulfilled by means of exciter inductor which forms impulse complex modulated electromagnetic field (ICM EMF. The measurement process and visualizations provided by set of certificated instruments: a digital oscillograph AKTAKOM ADS-2221MV, a digital generator АКТАКОМ AWG-4150 (both with software and a gauge RLC E7-22. Comparative dynamic studies of fixed volume and weight pig’s blood, adipose tissue, muscular tissue impedance were conducted by contact versus contactless methods. Contactless method in contrast to contact method gives opportunity to obtain the real morphological visualization of biological tissue irrespective of their nature.Results. Comparison of contact and contactless methods of impedance measurement shows that the inductance to capacitance ratio X(L / X(C was equal: 17 – for muscular tissue, 4 – for blood, 1 – for adipose tissue. It demonstrates the technical correspondence of both impedance registration methods. If propose the base relevance of X (L and X (C parameters for biological tissue impedance so contactless measurement method for sure shows insulating properties of adipose tissue and high conductivity for blood and muscular tissue in fixed volume-weight parameters. Registration of biological tissue impedance complex parameters by contactless method with the help of induced ICM EMF in fixed volume of biological tissue uncovers the most important informative volumes to characterize morphofunctional condition of biological tissue namely X (L / X (C.Conclusion. Contactless method of biological
Resonant impedance of bellows above cutoff
Energy Technology Data Exchange (ETDEWEB)
Krinsky, S
1980-01-01
The perturbation method of Chatard-Moulin and Papiernik is used to calculate the longitudinal and transverse impedances, Z(..omega..) and Z/sub perpendicular/(..omega..), of a bellows. The bellows shape is defined by its radius a(z) = a (1 + epsilons(z)), where a is the mean radius, epsilon a small parameter, and s(z) describes the convolution of the bellows. A finite wall conductivity is considered and the resonant contribution to the impedance above the cutoff frequency of the unperturbed chamber is determined, obtaining analytic approximations to the resonant frequencies, quality factors, and shunt impedances. The relation Z/sub perpendicular/(..omega..) = (2c/a/sup 2/)Z(..omega..)/..omega.., of course, does not hold as an identity, but it is found to be a useful relation for the shunt impedances, holding exactly for one family of transverse modes and providing an upper bound on the shunt impedances of the second set of transverse modes.
Ferrofluid Microwave Devices With Magnetically Controlled Impedances
Fannin, P. C.; Stefu, N.; Marin, C. N.; Malaescu, I.; Totoreanu, R.
2010-08-01
Ferrofluid filled transmission lines are microwave electronic devices. The complex dielectric permittivity and the complex magnetic permeability of a kerosene based ferrofluid with magnetite nanoparticles, in the frequency range (0.5-6) GHz were measured, for several values of polarising field, H. Afterwards, the input impedance of a short-circuited transmission line filled with this ferrofluid was computed using the equation Z = Zc tanh(γl). Here Zc and l are the characteristic impedance and the length of the coaxial line and γ is the propagation constant, depending on the dielectric and magnetic parameters of the material within the line. It is demonstrated how the impedance displays a frequency and polarizing field dependence, which has application in the design of magnetically controlled microwave devices.
Pumping slots: Coupling impedance calculations and estimates
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.
1993-08-01
Coupling impedances of small pumping holes in vacuum-chamber walls have been calculated at low frequencies, i.e., for wavelengths large compared to a typical hole size, in terms of electric and magnetic polarizabilities of the hole. The polarizabilities can be found by solving and electro- or magnetostatic problem and are known analytically for the case of the elliptic shape of the hole in a thin wall. The present paper studies the case of pumping slots. Using results of numerical calculations and analytical approximations of polarizabilities, we give formulae for practically important estimates of slot contribution to low-frequency coupling impedances.
On coupling impedances of pumping holes
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.
1993-04-01
Coupling impedances of a single small hole in vacuum-chamber walls have been calculated at low frequencies. To generalize these results for higher frequencies and/or larger holes one needs to solve coupled integral equations for the effective currents. These equations are solved for two specific hole shapes. The effects of many holes at high frequencies where the impedances are not additive are studied using a perturbation-theory method. The periodic versus random distributions of the pumping holes in the Superconducting Super Collider liner are compared.
Numerical modelling errors in electrical impedance tomography.
Dehghani, Hamid; Soleimani, Manuchehr
2007-07-01
Electrical impedance tomography (EIT) is a non-invasive technique that aims to reconstruct images of internal impedance values of a volume of interest, based on measurements taken on the external boundary. Since most reconstruction algorithms rely on model-based approximations, it is important to ensure numerical accuracy for the model being used. This work demonstrates and highlights the importance of accurate modelling in terms of model discretization (meshing) and shows that although the predicted boundary data from a forward model may be within an accepted error, the calculated internal field, which is often used for image reconstruction, may contain errors, based on the mesh quality that will result in image artefacts.
Electrical impedance measurement of irradiated potatoes
International Nuclear Information System (INIS)
Several chemical, biochemical and histological methods have been suggested for the identification of irradiated potatoes but these methods are either time consuming or lack the reliability and precision to be of much practical use. Measurement of electrical conductivity or impedance appears to be a simple and reliable technique. We have examined the suitability of electrical impedance method for potatoes grown in our country after exposing to a sprout inhibiting dose of 0.1 kGy. The results of this study are described. 10 refs., 3 figs., 2 tabs
Directory of Open Access Journals (Sweden)
Humayra Ferdous
2013-12-01
Full Text Available Focused Impedance Measurement (FIM is a technique where impedance can be measured with the optimum level of localization without much increase in complexity of measuring instrument. The electrodes are applied on the skin surface but the organs inside also contributes to the measurement, as the body is a volume conductor. In a healthy and disease free lung region, the air enters at breathe-in increases the impedance of the lung and impedance reduces during breathe-out. In contrast, for a diseased lung, where part of the lungs is filled with water or some fluid, air will not enter into this zone reducing impedance change between inspiration and expiration. With this idea, the current work had been executed to have general view of localised impedance change throughout thorax using 6-electrode FIM. This generated a matrix mapping from both the front and from the back of the thorax, which afterwards provided that how impedance change due to ventilation varies from frontal plane to back plane of human bodies.
Locating Impedance Change in Electrical Impedance Tomography Based on Multilevel BP Neural Network
Institute of Scientific and Technical Information of China (English)
彭源; 莫玉龙
2003-01-01
Electrical impedance tomography (EIT) is a new computer tomography technology, which reconstructs an impedance (resistivity, conductivity) distribution, or change of impedance, by making voltage and current measurements on the object's periphery.Image reconstruction in EIT is an ill-posed, non-linear inverse problem. A method for finding the place of impedance change in EIT is proposed in this paper, in which a multilevel BP neural network (MBPNN) is used to express the non-linear relation between theimpedance change inside the object and the voltage change measured on the surface of the object. Thus, the location of the impedance change can be decided by the measured voltage variation on the surface. The impedance change is then reconstructed using a linear approximate method. MBPNN can decide the impedance change location exactly without long training time. It alleviates some noise effects and can be expanded, ensuring high precision and space resolution of the reconstructed image that are not possible by using the back projection method.
Electrical Impedance Tomography Technology (EITT) Project
Oliva-Buisson, Yvette J.
2014-01-01
Development of a portable, lightweight device providing two-dimensional tomographic imaging of the human body using impedance mapping. This technology can be developed to evaluate health risks and provide appropriate medical care on the ISS, during space travel and on the ground.
Impedance and collective effects in the KEKB
Energy Technology Data Exchange (ETDEWEB)
Chin, Yongho [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan); Oide, Katsunobu
1996-08-01
This paper focuses on beam instabilities due to single-beam collective effects, impedances from various beamline elements, ion trapping, photo-electrons, and other issues in the KEKB. We will also discuss the power deposition generated by a beam in the form of the Higher-Order-Mode (HOM) losses by interacting with its surroundings. (author)
Identification of irradiated potatoes by impedance measurements
International Nuclear Information System (INIS)
A variety of parameters drawn from impedance measurements are tested to distinguish between irradiated and non-irradiated potatoes. Some of these parameters are able to identify the irradiated potatoes. The identification is still possible after a storage time of 3 months. (author)
Identification of irradiated potatoes by impedance measurements
International Nuclear Information System (INIS)
Identification of irradiated potatoes (Alpha variety) by electrical impedance measurements has been carried out. Experiments were performed by passing ∼3m A alternating current through the potato tubers that were punctured with the galvanized metallic electrodes. The parameters Z0/Z180 (impedance ratio at 50 Hz zero to 180 seconds post puncturing) Z50 k/Z5 k, Z0.5 k/ Z50 k/Z0.05 k (impedance ratio at 50 khz, and 0.05 khz, respectively) were determined at various temperatures and the best temperature for the measurement was obtained. The selection of the identification parameter was based on its constancy over the post irrigation storage time (six months), as well as, its dependency on the magnitude of the absorbed dose.Based on the above criteria, the impedance ratio of Z50 k/Z5 k was determined to be the best identification parameter.The obtained empirical formulas allow to estimate the applied dose and also to differentiation between the irradiated and unirradiated potatoes at the temperature of the (20-30digc)
Detection of irradiated potatoes by impedance measurement
International Nuclear Information System (INIS)
Potato is one of the major food items to be treated with ionising radiation and potatoes are irradiated on a large scale in several countries. Every year around 15,000 t of potatoes are irradiated at doses of 60 to 150 Gy (average dose is about 100 Gy) in Japan. Although various methods to detect irradiated potatoes have been investigated, no established method has been reported. Measuring electrical conductivity or impedance of potatoes has been reported as a promising method for the detection of irradiated potatoes. In previous studies it has been found that the ratio of impedance magnitude at 50 kHz to that at 5 kHz, measured immediately after puncturing a potato tuber, is dependent upon the dose applied to the tuber, independent of storage temperature and stable during storage after irradiation. The aim of this study was to establish the optimum conditions for impedance measurement and to examine the applicability of the impedance measuring method to various cultivars (cv.) of potatoes. (author)
The electrochemical impedance of metal hydride electrodes
DEFF Research Database (Denmark)
Valøen, Lars Ole; Lasia, Andrzej; Jensen, Jens Oluf;
2002-01-01
The electrochemical impedance responses for different laboratory type metal hydride electrodes were successfully modeled and fitted to experimental data for AB5 type hydrogen storage alloys as well as one MgNi type electrode. The models fitted the experimental data remarkably well. Several AC equ...
Impedance-matched drilling telemetry system
Normann, Randy A.; Mansure, Arthur J.
2008-04-22
A downhole telemetry system that uses inductance or capacitance as a mode through which signal is communicated across joints between assembled lengths of pipe wherein efficiency of signal propagation through a drill string, for example, over multiple successive pipe segments is enhanced through matching impedances associated with the various telemetry system components.
Beam measurements of the LHC impedance and validation of the impedance model
Esteban Müller, J F; Bohl, T; Mounet, N; Shaposhnikova, E; Timko, H
2014-01-01
Different measurements of the longitudinal impedance of the LHC done with single bunches with various intensities and longitudinal emittances during measurement sessions in 2011-2012 are compared with particle simulations based on the existing LHC impedance model. The very low reactive impedance of the LHC, with Im Z=n = 0.08, is not easy to measure. The most sensitive observation is the loss of Landau damping, which shows at which energy bunches become unstable depending on their parameters. In addition, the synchrotron frequency shift due to the reactive impedance was estimated following two methods. Firstly, it was obtained from the peak-detected Schottky spectrum. Secondly, a sine modulation in the RF phase was applied to the bunches of different intensities and the modulation frequency was scanned. In both cases, the synchrotron frequency shift was of the order of the measurement precision.
Huang, Jun; Li, Zhe; Zhang, Jianbo
2015-01-01
In this study, a novel implementation of dynamic electrochemical impedance spectroscopy (DEIS) is proposed. The method first measures the impedance continuously at a single frequency during one charging/discharging cycle, then repeats the measurement at a number of other selected frequencies. The impedance spectrum at a specific SOC is obtained by interpolating and collecting the impedance at all of the selected frequencies. The charge transfer resistance, Rct, from the DEIS is smaller than that from the steady EIS in a wide state-of-charge (SOC) range from 0.4 to 1.0, the Rct during charging is generally smaller than that during discharging for the battery chemistry used in this study.
International Nuclear Information System (INIS)
The purpose of this study is to compare measurement errors in two commercially available multi-frequency bioimpedance analyzers, a Xitron 4000B and an ImpediMed SFB7, including electrode impedance mismatch. The comparison was made using resistive electrical models and in ten human volunteers. We used three different electrical models simulating three different body segments: the right-side, leg and thorax. In the electrical models, we tested the effect of the capacitive coupling of the patient to ground and the skin–electrode impedance mismatch. Results showed that both sets of equipment are optimized for right-side measurements and for moderate skin–electrode impedance mismatch. In right-side measurements with mismatch electrode, 4000B is more accurate than SFB7. When an electrode impedance mismatch was simulated, errors increased in both bioimpedance analyzers and the effect of the mismatch in the voltage detection leads was greater than that in current injection leads. For segments with lower impedance as the leg and thorax, SFB7 is more accurate than 4000B and also shows less dependence on electrode mismatch. In both devices, impedance measurements were not significantly affected (p > 0.05) by the capacitive coupling to ground
Inter-Changeability of Impedance Devices for Lymphedema Assessment.
van Zanten, Malou; Piller, Neil; Ward, Leigh C
2016-06-01
Impedance technology is a popular technique for the early detection of lymphedema. The preferred approach is to use bioimpedance spectroscopy (BIS), with measurements being made with the subject lying supine, although attempts have been made to use single or multiple frequency impedance measurements obtained while the subject is standing. The aim of the present study was to determine the equivalence of these different approaches. Impedance measurements of the individual limbs of 37 healthy individuals were determined using both a stand-on, multi-frequency impedance device and a supine impedance spectroscopy instrument. Significant differences were found between the instruments in both absolute impedance values and, importantly, inter-limb impedance ratios. Since impedance ratios in healthy individuals provide the reference standard for detection of lymphedema, these data indicate that the methods are not interchangeable. Consideration of the errors associated with each method indicates that the BIS remains the preferred method for lymphedema detection. PMID:26574711
Electrochemical Impedance of Ethanol Oxidation in Alkaline Media
Institute of Scientific and Technical Information of China (English)
DANAEE Iman; JAFARIAN Majid; GOBAL Fereydoon; SHARAFI Mahboobeh; MAHJANI Mohammad-ghasem
2012-01-01
Nickel modified NiOOH electrodes were used for the electrocatalytic oxidation of ethanol in alkaline solutions.The electro-oxidation of ethanol in a 1 mol/L NaOH solution at different concentrations of ethanol was studied by ac impedance spectroscopy.Electrooxidation of ethanol on Ni shows negative resistance on impedance plots.The impedance shows different patterns at different applied anodic potential.The influence of the electrode potential on impedance was studied and a quantitative explanation for the impedance of ethanol oxidation was given by means of a proposed mathematical model.At potentials higher than 0.52 V(vs.Ag/AgCl),a pseudoinductive behavior was observed,but at those higher than 0.57 V,impedance patterns were reversed to the second and third quadrants.The conditions required for the reversing of impedance pattern were delineated with the impedance model.
Segmental and whole body electrical impedance measurements in dialysis patients
Nescolarde Selva, Lexa
2006-01-01
The main objective of this thesis is to contribute to the prevention and control of the cardiovascular risk, hydration state and nutritional state in dialysis patients using non-invasive electrical impedance measurements. The thesis is structured in three parts with the following objectives: 1) to establish electrical impedance reference data for healthy Cuban population, 2)to improve the diagnostic based on impedance methods in Cuban hemodialysis (HD)patients and 3) to develop the impedance ...
Using A Particular Sampling Method for Impedance Measurement
Lentka Grzegorz
2014-01-01
The paper presents an impedance measurement method using a particular sampling method which is an alternative to DFT calculation. The method uses a sine excitation signal and sampling response signals proportional to current flowing through and voltage across the measured impedance. The object impedance is calculated without using Fourier transform. The method was first evaluated in MATLAB by means of simulation. The method was then practically verified in a constructed simple impedance measu...
Acoustic Impedance Inversion VIa Wavelet Transform COnstraints
Institute of Scientific and Technical Information of China (English)
HuiyanZHANG; BainianLU; 等
1998-01-01
As is well known,the acoustic impedance inversion problem is,in general.an underdetermined inverse problem and some constraints about the model have to be incorporated in the inversion scheme,In this article,we assume that a prioir scale information about the model is available to constrain the inversion.We then explore another approach by means of the wavelet transform.WT,where we are specifically concerned with the selection and application of a priori scale information in the wavelet domain to reconstruct the acoustic impedance model.A simple example is explored,which show that the WT approach improves results in comparison with the conventional approach.
Are patents impeding medical care and innovation?
Directory of Open Access Journals (Sweden)
E Richard Gold
2010-01-01
Full Text Available BACKGROUND TO THE DEBATE: Pharmaceutical and medical device manufacturers argue that the current patent system is crucial for stimulating research and development (R&D, leading to new products that improve medical care. The financial return on their investments that is afforded by patent protection, they claim, is an incentive toward innovation and reinvestment into further R&D. But this view has been challenged in recent years. Many commentators argue that patents are stifling biomedical research, for example by preventing researchers from accessing patented materials or methods they need for their studies. Patents have also been blamed for impeding medical care by raising prices of essential medicines, such as antiretroviral drugs, in poor countries. This debate examines whether and how patents are impeding health care and innovation.
Impedance of Surface Footings on Layered Ground
DEFF Research Database (Denmark)
Andersen, Lars; Clausen, Johan Christian
2005-01-01
is discussed. Based on the Green's function for a stratified half-space, the impedance of a surface footing with arbitrary shape is computed. A wind turbine foundation is analysed in the frequency range 0 to 3 Hz. Analyses show that soil stratification may lead to a significant changes in the impedance related......Traditionally only the static bearing capacity and stiffness of the ground is considered in the design of wind turbine foundations. However, modern wind turbines are flexible structures with resonance frequencies as low as 0.2 Hz. Unfortunately, environmental loads and the passage of blades past...... the tower may lead to excitation with frequencies of the same order of magnitude. Therefore, dynamic soil-structure interaction has to be accounted for in order to get an accurate prediction of the structural response. In this paper the particular problem of a rigid foundation on a layered subsoil...
Impedance of Surface Footings on Layered Ground
DEFF Research Database (Denmark)
Andersen, Lars; Clausen, Johan
2007-01-01
is discussed. Based on the Green's function for a stratified half-space, the impedance of a surface footing with arbitrary shape is computed. A wind turbine foundation is analysed in the frequency range 0-3 Hz. Analyses show that soil stratification may lead to significant changes in the impedance related......Traditionally only the static bearing capacity and stiffness of the ground is considered in the design of wind turbine foundations. However, modern wind turbines are flexible structures with resonance frequencies as low as 0.2 Hz. Unfortunately, environmental loads and the passage of blades past...... the tower may lead to excitation with frequencies of the same order of magnitude. Therefore, dynamic soilstructure interaction has to be accounted for in order to get an accurate prediction of the structural response. In this paper the particular problem of a rigid foundation on a layered subsoil...
Assessment of chest impedance in relation to phonocardiography
DEFF Research Database (Denmark)
Zimmermann, Niels Henrik; Møller, Henrik; Hammershøi, Dorte;
2010-01-01
), it is possible to measure the impedance of the surface of the skin and at the same time investigate the influence of different pressures and diameters of a transducer. The impedance tube is made specifically with the purpose of measuring chest impedances in the frequency range from 50 Hz to 5 kHz. An MLS...
Estimating the Transverse Impedance in the Fermilab Recycler
Energy Technology Data Exchange (ETDEWEB)
Ainsworth, Robert [Fermilab; Adamson, Philip [Fermilab; Burov, Alexey [Fermilab; Kourbanis, Ioanis [Fermilab; Yang, Ming-Jen [Fermilab
2016-06-01
Impedance could represent a limitation of running high intensity bunches in the Fermilab recycler. With high intensity upgrades foreseen, it is important to quantify the impedance. To do this, studies have been performed measuring the tune shift as a function of bunch intensity allowing the transverse impedance to be derived.
Impedance Interaction Modeling and Analysis for Bidirectional Cascaded Converters
DEFF Research Database (Denmark)
Tian, Yanjun; Deng, Fujin; Chen, Zhe;
2015-01-01
For the cascaded converter system, the output impedance of source converter interacts with the input impedance of load converter, and the interaction may cause the system instability. In bidirectional applications, when the power flow is reversed, the impedance interaction also varies, which brin...
PHEMT Distributed Power Amplifier Adopting Broadband Impedance Transformer
DEFF Research Database (Denmark)
Narendra, K.; Limiti, E.; Paoloni, C.;
2013-01-01
A non-uniform drain line distributed power amplifier (DPA) employing a broadband impedance transformer is presented. The DPA is based on GaAs PHEMT technology. The impedance transformer employs asymmetric coupled lines and transforms a low output impedance of the amplifier to a standard 50 Ω...
Bioelectrical Impedance Assessment of Wound Healing
Lukaski, Henry C.; Moore, Micheal
2012-01-01
Objective assessment of wound healing is fundamental to evaluate therapeutic and nutritional interventions and to identify complications. Despite availability of many techniques to monitor wounds, there is a need for a safe, practical, accurate, and effective method. A new method is localized bioelectrical impedance analysis (BIA) that noninvasively provides information describing cellular changes that occur during healing and signal complications to wound healing. This article describes the ...
Detection of irradiated potatoes by impedance measurements
International Nuclear Information System (INIS)
The impedance ratio at 5kHz to 50kHz (Z6K/Z50K) determined at 22degC at an apical region of potato tuber which was pre-incubated at 22degC for 3 days or longer resulted in the best detection of radian treatment. Irradiated potatoes of 10 cultivars could be detected with this method, and potatoes 'Danshaku' commercially irradiated at Shihoro could be distinguished from unirradiated 'Danshaku'. (author)
Giant Magneto-Impedance and its Applications
Tannous, C
2002-01-01
The status of Giant Magneto-Impedance effect is reviewed in Wires, Ribbons and Multilayered Soft Ferromagnetic Thin Films. After establishing the theoretical framework for the description of the effect, and the constraints any material should have in order to show the effect, experimental work in Wires, Ribbons and Multilayered Thin Films is described. Existing and potential applications of the effect in Electronics and Sensing are highlighted.
Impedance Matched Absorptive Thermal Blocking Filters
Wollack, E J; Rostem, K; U-Yen, K
2014-01-01
We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match $50\\,\\Omega$ and its response has been validated from 0-to-50\\,GHz. The observed return loss in the 0-to-20\\,GHz design band is greater than $20\\,$dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.
Electrode models in electrical impedance tomography
Institute of Scientific and Technical Information of China (English)
WANG M.
2005-01-01
This paper presents different views on electrode modelling, which include electrode electrochemistry models for modelling the effects of electrode-electrolyte interface, electric field electrode models for modelling electrode geometry, and electrode models for modelling the effects of electrode common mode voltage and double layer capacitance. Taking the full electrode models into consideration .in electrical impedance tomography (EIT) will greatly help the optimised approach to a good solution and further understanding of the measurement principle.
Applications of Nonlinear Electrochemical Impedance Spectroscopy (NLEIS)
Adler, S. B.
2013-08-31
This paper reviews the use of nonlinear electrochemical impedance spectroscopy (NLEIS) in the analysis of SOFC electrode reactions. By combining EIS and NLEIS, as well as other independent information about an electrode material, it becomes possible to establish quantitative links between electrochemical kinetics and materials properties, even when systems are unstable with time. After a brief review of the method, this paper summarizes recent results analyzing the effects of Sr segregation in thin-film LSC electrodes. © The Electrochemical Society.
New methods of measuring normal acoustic impedance
Wayman, James L.
1984-01-01
In recent years new methods based on signal processing technical have been developed to measure the normal acoustic impedance of materials. These methods proved to be considerably faster easier to implement than the SRW method rhey replace. Mathematical, hardware and software aspects of these techniques are discussed and results obtained over a frequency range of 200-4000 Hz for several architectural materials are presented. NPS Foundation Research Program http://archive....
Bioelectrical impedance analysis of bovine milk fat
International Nuclear Information System (INIS)
Three samples of 250ml at home temperature of 20°C were obtained from whole, low fat and fat free bovine UHT milk. They were analysed by measuring both impedance spectra and dc conductivity in order to establish the relationship between samples related to fat content. An impedance measuring system was developed, which is based on digital oscilloscope, a current source and a FPGA. Data was measured by the oscilloscope in the frequency 1 kHz to 100 kHz. It was showed that there is approximately 7.9% difference in the conductivity between whole and low fat milk whereas 15.9% between low fat and free fat one. The change of fatness in the milk can be significantly sensed by both impedance spectra measurements and dc conductivity. This result might be useful for detecting fat content of milk in a very simple way and also may help the development of sensors for measuring milk quality, as for example the detection of mastitis.
Application of impedance spectroscopy to SOFC research
Energy Technology Data Exchange (ETDEWEB)
Hsieh, G.; Mason, T.O. [Northwestern Univ., Evanston, IL (United States); Pederson, L.R. [Pacific Northwest National Lab., Richland, WA (United States)
1996-12-31
With the resurgence of interest in solid oxide fuel cells and other solid state electrochemical devices, techniques originally developed for characterizing aqueous systems are being adapted and applied to solid state systems. One of these techniques, three-electrode impedance spectroscopy, is particularly powerful as it allows characterization of subcomponent and interfacial properties. Obtaining accurate impedance spectra, however, is difficult as reference electrode impedance is usually non-negligible and solid electrolytes typically have much lower conductance than aqueous solutions. Faidi et al and Chechirlian et al have both identified problems associated with low conductivity media. Other sources of error are still being uncovered. Ford et al identified resistive contacts with large time constants as a possibility, while Me et al showed that the small contact capacitance of the reference electrode was at fault. Still others show that instrument limitations play a role. Using the voltage divider concept, a simplified model that demonstrates the interplay of these various factors, predicts the form of possible distortions, and offers means to minimize errors is presented.
Qureshi, Tabassum-Ur-Razaq; Chatwin, Chris; Huber, Nicolas; Zarafshani, Ali; Tunstall, Benjamin; Wang, Wei
2010-01-01
The current source is a key component in bio-impedance measurement systems. The accuracy of the current source can be measured in terms of its output impedance together with other parameters, with certain applications demanding extremely high output impedance. This paper presents an investigation and comparison of different current source designs based on the Enhanced Howland circuit combined with a General Impedance Converter (GIC) circuit using both ideal and non-ideal operational amplifier...
Impedance spectroscopy and electrical modeling of electrowetting on dielectric devices
International Nuclear Information System (INIS)
Using impedance spectroscopy, we have determined models for the elements which determine the ac electrical behavior in electrowetting on dielectric (EWOD) systems. Three commonly used EWOD electrode configurations were analyzed. In each case, the impedance can be modeled by a combination of elements, including the solution resistance, the capacitance of the dielectric layer, and the constant phase impedance of the electrode double layers. The sensitivity of the system’s impedance to variations in the electrowetted area is also analyzed for these common configurations. We also demonstrate that the impedance per unit area of typical EWOD systems is invariant to bias voltage. (paper)
Wakefield and impedance studies of a liner using MAFIA
Energy Technology Data Exchange (ETDEWEB)
Chou, W.; Barts, T.
1993-03-01
The liner is a perforated beam tube that is coaxial with an outer bore tube. The 3D code MAFIA (version 3.1) is used to study the wakefields, impedances, and resonances of this structure. The short-range wakes and low-frequency (below the cutoff) impedances are in agreement with the theoretical model. The long-range wakes and high-frequency resonances are associated with the distribution of the holes (or slots). The dependence of the impedance on the size, shape, and pattern of the holes (or slots) is studied. The impact of the liner impedance on the Superconducting Super Collider impedance budget is discussed.
Wakefield and impedance studies of a liner using MAFIA
Energy Technology Data Exchange (ETDEWEB)
Chou, W.; Barts, T. (SSC Laboratory, Dallas, Texas 75237 (United States))
1993-12-25
The liner is a perforated beam tube which is coaxial with an outer bore tube. The 3D code MAFIA version 3.1 is used to study the wakefields, impedances, and resonances of this structure. The short range wakes and low frequency (below the cutoff) impedances are in agreement with the theoretical model. The long range wakes and high frequency resonances are associated with the distribution of the holes (or slots). The dependence of the impedance on the size, shape, and pattern of the holes (or slots) is studied. The impact of the liner impedance on the SSC impedance budget is discussed.
Wakefield and impedance studies of a liner using MAFIA
Chou, W.; Barts, T.
1993-12-01
The liner is a perforated beam tube which is coaxial with an outer bore tube. The 3D code MAFIA version 3.1 is used to study the wakefields, impedances, and resonances of this structure. The short range wakes and low frequency (below the cutoff) impedances are in agreement with the theoretical model. The long range wakes and high frequency resonances are associated with the distribution of the holes (or slots). The dependence of the impedance on the size, shape, and pattern of the holes (or slots) is studied. The impact of the liner impedance on the SSC impedance budget is discussed.
Impedance adaptation for optimal robot-environment interaction
Ge, Shuzhi Sam; Li, Yanan; Wang, Chen
2014-02-01
In this paper, impedance adaptation is investigated for robots interacting with unknown environments. Impedance control is employed for the physical interaction between robots and environments, subject to unknown and uncertain environments dynamics. The unknown environments are described as linear systems with unknown dynamics, based on which the desired impedance model is obtained. A cost function that measures the tracking error and interaction force is defined, and the critical impedance parameters are found to minimise it. Without requiring the information of the environments dynamics, the proposed impedance adaptation is feasible in a large number of applications where robots physically interact with unknown environments. The validity of the proposed method is verified through simulation studies.
Impedance analysis of fibroblastic cell layers measured by electric cell-substrate impedance sensing
Lo, Chun-Min; Ferrier, Jack
1998-06-01
Impedance measurements of cell layers cultured on gold electrode surfaces obtained by electric cell-substrate impedance sensing provide morphological information such as junctional resistance and cell-substrate separation. Previously, a model that assumes that cells have a disklike shape and that electric currents flow radially underneath the ventral cell surface and then through the paracellular space has been used to theoretically calculate the impedance of the cell-covered electrode. In this paper we propose an extended model of impedance analysis for cell layers where cellular shape is rectangular. This is especially appropriate for normal fibroblasts in culture. To verify the model, we analyze impedance data obtained from four different kinds of fibroblasts that display a long rectangular shape. In addition, we measure the average cell-substrate separation of human gingival fibroblasts at different temperatures. At temperatures of 37, 22, and 4 °C, the average separation between ventral cell surface and substratum are 46, 55, and 89 nm, respectively.
Oblique impacts into low impedance layers
Stickle, A. M.; Schultz, P. H.
2009-12-01
Planetary impacts occur indiscriminately, in all locations and materials. Varied geologic settings can have significant effects on the impact process, including the coupling between the projectile and target, the final damage patterns and modes of deformation that occur. For example, marine impact craters are not identical to impacts directly into bedrock or into sedimentary materials, though many of the same fundamental processes occur. It is therefore important, especially when considering terrestrial impacts, to understand how a low impedance sedimentary layer over bedrock affects the deformation process during and after a hypervelocity impact. As a first step, detailed comparisons between impacts and hydrocode models were performed. Experiments performed at the NASA Ames Vertical Gun Range of oblique impacts into polymethylmethacrylate (PMMA) targets with low impedance layers were performed and compared to experiments of targets without low impedance layers, as well as to hydrocode models under identical conditions. Impact velocities ranged from 5 km/s to 5.6 km/s, with trajectories from 30 degrees to 90 degrees above the horizontal. High-speed imaging provided documentation of the sequence and location of failure due to impact, which was compared to theoretical models. Plasticine and ice were used to construct the low impedance layers. The combination of experiments and models reveals the modes of failure due to a hypervelocity impact. How such failure is manifested at large scales can present a challenge for hydrocodes. CTH models tend to overestimate the amount of damage occurring within the targets and have difficulties perfectly reproducing morphologies; nevertheless, they provide significant and useful information about the failure modes and style within the material. CTH models corresponding to the experiments allow interpretation of the underlying processes involved as well as provide a benchmark for the experimental analysis. The transparency of PMMA
Superconducting fault current-limiter with variable shunt impedance
Llambes, Juan Carlos H; Xiong, Xuming
2013-11-19
A superconducting fault current-limiter is provided, including a superconducting element configured to resistively or inductively limit a fault current, and one or more variable-impedance shunts electrically coupled in parallel with the superconducting element. The variable-impedance shunt(s) is configured to present a first impedance during a superconducting state of the superconducting element and a second impedance during a normal resistive state of the superconducting element. The superconducting element transitions from the superconducting state to the normal resistive state responsive to the fault current, and responsive thereto, the variable-impedance shunt(s) transitions from the first to the second impedance. The second impedance of the variable-impedance shunt(s) is a lower impedance than the first impedance, which facilitates current flow through the variable-impedance shunt(s) during a recovery transition of the superconducting element from the normal resistive state to the superconducting state, and thus, facilitates recovery of the superconducting element under load.
A review of impedance measurements of whole cells.
Xu, Youchun; Xie, Xinwu; Duan, Yong; Wang, Lei; Cheng, Zhen; Cheng, Jing
2016-03-15
Impedance measurement of live biological cells is widely accepted as a label free, non-invasive and quantitative analytical method to assess cell status. This method is easy-to-use and flexible for device design and fabrication. In this review, three typical techniques for impedance measurement, i.e., electric cell-substrate impedance sensing, Impedance flow cytometry and electric impedance spectroscopy, are reviewed from the aspects of theory, to electrode design and fabrication, and applications. Benefiting from the integration of microelectronic and microfluidic techniques, impedance sensing methods have expanded their applications to nearly all aspects of biology, including living cell counting and analysis, cell biology research, cancer research, drug screening, and food and environmental safety monitoring. The integration with other techniques, the fabrication of devices for certain biological assays, and the development of point-of-need diagnosis devices is predicted to be future trend for impedance sensing techniques. PMID:26513290
International Nuclear Information System (INIS)
We report on the impedance mapping of in vitro cellular morphology by electrical impedance spectroscopy, using microelectrodes. A micro multielectrode system was designed, fabricated, assembled, tested and demonstrated for the monitoring of anchorage-dependent cell behavior and morphology. This system allowed continuous, label-free, quantitative monitoring and visualization of cell adhesion, spreading, proliferation and detachment due to cell cycle processes as well as cell–drug interaction, with spatio-temporal resolution. OvCa429 ovarian cancer cells were monitored in vitro over a period of 70 hours by inoculating the cell suspension directly on the multielectrode device. The phase angle of impedance was observed to develop a distinctive shape as a result of cell attachment and proliferation. The shape of the phase angle curve reverted back to the pre-attachment shape upon detachment of cells from the substrate, caused by the addition of trypsin to the cell culture medium. The impedance data of the cell culture were then successfully modeled as a multi-parametric equivalent circuit. The model incorporated both interfacial and cell-layer impedance parameters. Upon addition of trypsin, the cell-layer parameters showed a marked decline and were eventually eliminated from the multi-parametric model, confirming the correlation of the model to the electrode–cell–electrolyte system. These experiments demonstrate the applicability of the impedance mapping technique in visualizing and quantifying physiological changes in the cell layer due to cellular processes as well as the effect of external chemical stimulus on cells (cell–drug interaction)
Directory of Open Access Journals (Sweden)
Humberto Villacorta Junior
2012-12-01
Full Text Available FUNDAMENTO: A ressonância magnética cardíaca é considerada o método padrão-ouro para o cálculo de volumes cardíacos. A bioimpedância transtorácica cardíaca avalia o débito cardíaco. Não há trabalhos que validem essa medida comparada à ressonância. OBJETIVO: Avaliar o desempenho da bioimpedância transtorácica cardíaca no cálculo do débito cardíaco, índice cardíaco e volume sistólico, utilizando a ressonância como padrão-ouro. MÉTODOS: Avaliados 31 pacientes, com média de idade de 56,7 ± 18 anos, sendo 18 (58% do sexo masculino. Foram excluídos os pacientes cuja indicação para a ressonância magnética cardíaca incluía avaliação sob estresse farmacológico. A correlação entre os métodos foi avaliada pelo coeficiente de Pearson, e a dispersão das diferenças absolutas em relação à média foi demonstrada pelo método de Bland-Altman. A concordância entre os métodos foi realizada pelo coeficiente de correlação intraclasses. RESULTADOS: A média do débito cardíaco pela bioimpedância transtorácica cardíaca e pela ressonância foi, respectivamente, 5,16 ± 0,9 e 5,13 ± 0,9 L/min. Observou-se boa correlação entre os métodos para o débito cardíaco (r = 0,79; p = 0,0001, índice cardíaco (r = 0,74; p = 0,0001 e volume sistólico (r = 0,88; p = 0,0001. A avaliação pelo gráfico de Bland-Altman mostrou pequena dispersão das diferenças em relação à média, com baixa amplitude dos intervalos de concordância. Houve boa concordância entre os dois métodos quando avaliados pelo coeficiente de correlação intraclasses, com coeficientes para débito cardíaco, índice cardíaco e volume sistólico de 0,78, 0,73 e 0,88, respectivamente (p BACKGROUND: Cardiac magnetic resonance imaging is considered the gold-standard method for the calculation of cardiac volumes. Transthoracic impedance cardiography assesses the cardiac output. No studies validating this measurement, in comparison to that obtained
Directory of Open Access Journals (Sweden)
Humberto Villacorta Junior
2012-01-01
Full Text Available FUNDAMENTO: A ressonância magnética cardíaca é considerada o método padrão-ouro para o cálculo de volumes cardíacos. A bioimpedância transtorácica cardíaca avalia o débito cardíaco. Não há trabalhos que validem essa medida comparada à ressonância. OBJETIVO: Avaliar o desempenho da bioimpedância transtorácica cardíaca no cálculo do débito cardíaco, índice cardíaco e volume sistólico, utilizando a ressonância como padrão-ouro. MÉTODOS: Avaliados 31 pacientes, com média de idade de 56,7 ± 18 anos, sendo 18 (58% do sexo masculino. Foram excluídos os pacientes cuja indicação para a ressonância magnética cardíaca incluía avaliação sob estresse farmacológico. A correlação entre os métodos foi avaliada pelo coeficiente de Pearson, e a dispersão das diferenças absolutas em relação à média foi demonstrada pelo método de Bland-Altman. A concordância entre os métodos foi realizada pelo coeficiente de correlação intraclasses. RESULTADOS: A média do débito cardíaco pela bioimpedância transtorácica cardíaca e pela ressonância foi, respectivamente, 5,16 ± 0,9 e 5,13 ± 0,9 L/min. Observou-se boa correlação entre os métodos para o débito cardíaco (r = 0,79; p = 0,0001, índice cardíaco (r = 0,74; p = 0,0001 e volume sistólico (r = 0,88; p = 0,0001. A avaliação pelo gráfico de Bland-Altman mostrou pequena dispersão das diferenças em relação à média, com baixa amplitude dos intervalos de concordância. Houve boa concordância entre os dois métodos quando avaliados pelo coeficiente de correlação intraclasses, com coeficientes para débito cardíaco, índice cardíaco e volume sistólico de 0,78, 0,73 e 0,88, respectivamente (p BACKGROUND: Cardiac magnetic resonance imaging is considered the gold-standard method for the calculation of cardiac volumes. Transthoracic impedance cardiography assesses the cardiac output. No studies validating this measurement, in comparison to that obtained
Impedance analysis of an enhanced piezoelectric biosensor
Kim, Gi-Ho
This study investigated the usefulness and characteristics of a five-megahertz quartz crystal resonator oscillating in a thickness-shear mode as a sensor of biological pathogens such as Salmonella typhimurium . An impedance analyzer measured the impedance of the oscillating quartz crystal, which determined all mechanical properties of the oscillating quartz and its immediate environment. In this study, the impedance behavior of the bare crystal was characterized in air and in potassium phosphate buffer solution. The potassium phosphate buffer was a Newtonian liquid. The resonance frequency of the oscillating quartz shifted down about 900 Hz by contacting with the buffer. An immobilized-antibody layer on the quartz surface behaved like a rigid mass when immersed in the buffer solution. The quartz crystal with immobilized antibodies was characterized in various solutions containing antibody- coated paramagnetic microspheres and varying concentrations of Salmonella typhimurium (102 - 108 cells/ml). The Salmonella cells were captured by antibody- coated paramagnetic microspheres, and then these complexes were moved magnetically to the oscillating quartz and were captured by antibodies immobilized on the crystal surface. The response of the crystal was expressed in terms of equivalent circuit parameters. The motional inductance and the motional resistance increased as a function of the concentration of Salmonella. The viscous damping was the main contribution to the resistance and the inductance in a liquid environment. The load resistance was the most effective and sensitive circuit parameter. A magnetic force was a useful method to collect the complexes of Salmonella-microspheres on the crystal surface and enhance the response sensor. In this system, the detection limit, based on resistance monitoring, was about 103 cells/ml.
Transferring human impedance regulation skills to robots
Ajoudani, Arash
2016-01-01
This book introduces novel thinking and techniques to the control of robotic manipulation. In particular, the concept of teleimpedance control as an alternative method to bilateral force-reflecting teleoperation control for robotic manipulation is introduced. In teleimpedance control, a compound reference command is sent to the slave robot including both the desired motion trajectory and impedance profile, which are then realized by the remote controller. This concept forms a basis for the development of the controllers for a robotic arm, a dual-arm setup, a synergy-driven robotic hand, and a compliant exoskeleton for improved interaction performance.
Development of the impedance void meter
Energy Technology Data Exchange (ETDEWEB)
Chung, Moon Ki; Song, Chul Hwa; Won, Soon Yeon; Kim, Bok Deuk [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1994-06-01
An impedance void meter is developed to measure the area-averaged void fraction. Its basic principle is based on the difference in the electrical conductivity between phases. Several methods of measuring void fraction are briefly reviewed and the reason why this type of void meter is chosen to develop is discussed. Basic principle of the measurement is thoroughly described and several design parameters to affect the overall function are discussed in detail. As example of applications is given for vertical air-water flow. It is shown that the current design has good dynamic response as well as very fine spatial resolution. (Author) 47 refs., 37 figs.
Bioelectrical impedance modelling of gentamicin pharmacokinetic parameters.
Zarowitz, B J; Pilla, A M; Peterson, E L
1989-10-01
1. Bioelectrical impedance analysis was used to develop descriptive models of gentamicin pharmacokinetic parameters in 30 adult in-patients receiving therapy with gentamicin. 2. Serial blood samples obtained from each subject at steady state were analyzed and used to derive gentamicin pharmacokinetic parameters. 3. Multiple regression equations were developed for clearance, elimination rate constant and volume of distribution at steady state and were all statistically significant at P less than 0.05. 4. Clinical validation of this innovative technique is warranted before clinical use is recommended.
Bioelectrical impedance analysis--part I
DEFF Research Database (Denmark)
Kyle, Ursula G; Bosaeus, Ingvar; De Lorenzo, Antonio D;
2004-01-01
The use of bioelectrical impedance analysis (BIA) is widespread both in healthy subjects and patients, but suffers from a lack of standardized method and quality control procedures. BIA allows the determination of the fat-free mass (FFM) and total body water (TBW) in subjects without significant...... of the estimate. The determination of changes in body cell mass (BCM), extra cellular (ECW) and intra cellular water (ICW) requires further research using a valid model that guarantees that ECW changes do not corrupt the ICW. The use of segmental-BIA, multifrequency BIA, or bioelectrical spectroscopy in altered...
Method for conducting nonlinear electrochemical impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Adler, Stuart B.; Wilson, Jamie R.; Huff, Shawn L.; Schwartz, Daniel T.
2015-06-02
A method for conducting nonlinear electrochemical impedance spectroscopy. The method includes quantifying the nonlinear response of an electrochemical system by measuring higher-order current or voltage harmonics generated by moderate-amplitude sinusoidal current or voltage perturbations. The method involves acquisition of the response signal followed by time apodization and fast Fourier transformation of the data into the frequency domain, where the magnitude and phase of each harmonic signal can be readily quantified. The method can be implemented on a computer as a software program.
Coupled Transmission Lines as Impedance Transformer
DEFF Research Database (Denmark)
Jensen, Thomas; Zhurbenko, Vitaliy; Krozer, Viktor;
2007-01-01
A theoretical investigation of the use of a coupled line section as an impedance transformer is presented. We show how to properly select the terminations of the coupled line structures for effective matching of real and complex loads in both narrow and wide frequency ranges. The corresponding....... Wideband matching performance with relative bandwidth beyond 100% and return loss > 20 dB is demonstrated both theoretically and experimentally. Good agreement is achieved between the measured and predicted performance of the coupled line transformer section....
Study on Impedance Characteristics of Aircraft Cables
Directory of Open Access Journals (Sweden)
Weilin Li
2016-01-01
Full Text Available Voltage decrease and power loss in distribution lines of aircraft electric power system are harmful to the normal operation of electrical equipment and may even threaten the safety of aircraft. This study investigates how the gap distance (the distance between aircraft cables and aircraft skin and voltage frequency (variable frequency power supply will be adopted for next generation aircraft will affect the impedance of aircraft cables. To be more precise, the forming mechanism of cable resistance and inductance is illustrated in detail and their changing trends with frequency and gap distance are analyzed with the help of electromagnetic theoretical analysis. An aircraft cable simulation model is built with Maxwell 2D and the simulation results are consistent with the conclusions drawn from the theoretical analysis. The changing trends of the four core parameters of interest are analyzed: resistance, inductance, reactance, and impedance. The research results can be used as reference for the applications in Variable Speed Variable Frequency (VSVF aircraft electric power system.
Electrochemical Impedance Spectroscopy of Conductive Polymer Coatings
Calle, Luz Marina; MacDowell, Louis G.
1996-01-01
Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion protection performance of twenty nine proprietary conductive polymer coatings for cold rolled steel under immersion in 3.55 percent NaCl. Corrosion potential as well as Bode plots of the data were obtained for each coating after one hour immersion, All coatings, with the exception of one, have a corrosion potential that is higher in the positive direction than the corrosion potential of bare steel under the same conditions. Group A consisted of twenty one coatings with Bode plots indicative of the capacitive behavior characteristic of barrier coatings. An equivalent circuit consisting of a capacitor in series with a resistor simulated the experimental EIS data for these coatings very well. Group B consisted of eight coatings that exhibited EIS spectra showing an inflection point which indicates that two time constants are present. This may be caused by an electrochemical process taking place which could be indicitive of coating failing. These coatings have a lower impedance that those in Group A.
AC Impedance Behaviour of Black Diamond Films
Institute of Scientific and Technical Information of China (English)
Haitao YE; Olivier GAUDIN; Richard B.JACKMAN
2005-01-01
The first measurement of impedance on free-standing diamond films from 0.1 Hz to 10 MHz up to 300℃ were reported. A wide range of chemical vapour deposition (CVD) materials were investigated, but here we concentrate are well fitted to a RC parallel circuit model and the equivalent resistance and capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 62 MΩ at room temperature to 4 kΩ at300℃, with an activation energy around 0.51 eV. The equivalent capacitance is maintained at the level of 100 pF up to 300℃ suggesting that the diamond grain boundaries are dominating the conduction. At 400℃, the impedance at low frequencies shows a linear tail, which can be explained that the AC polarization of diamond/Au interface occurs.
Impedance matching for broadband piezoelectric energy harvesting
Hagedorn, F.; Leicht, J.; Sanchez, D.; Hehn, T.; Manoli, Y.
2013-12-01
This paper presents a system design for broadband piezoelectric energy harvesting by means of impedance matching. An inductive load impedance is emulated by controlling the output current of the piezoelectric harvester with a bipolar boost converter. The reference current is derived from the low pass filtered voltage measured at the harvester terminals. In order to maximize the harvested power especially for nonresonant frequencies the filter parameters are adjusted by a simple optimization algorithm. However the amount of harvested power is limited by the efficiency of the bipolar boost converter. Therefore an additional switch in the bipolar boost converter is proposed to reduce the capacitive switching losses. The proposed system is simulated using numerical parameters of available discrete components. Using the additional switch, the harvested power is increased by 20%. The proposed system constantly harvests 80% of the theoretically available power over frequency. The usable frequency range of ±4Hz around the resonance frequency of the piezoelectric harvester is mainly limited due to the boost converter topology. This comparison does not include the power dissipation of the control circuit.
Transverse impedance measurement in RHIC and the AGS
Energy Technology Data Exchange (ETDEWEB)
Biancacci, Nicolo [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Dutheil, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Mernick, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; White, S. M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.
2014-05-12
The RHIC luminosity upgrade program aims for an increase of the polarized proton luminosity by a factor 2. To achieve this goal a significant increase in the beam intensity is foreseen. The beam coupling impedance could therefore represent a source of detrimental effects for beam quality and stability at high bunch intensities. For this reason it is essential to quantify the accelerator impedance budget and the major impedance sources, and possibly cure them. In this MD note we summarize the results of the 2013 transverse impedance measurements in the AGS and RHIC. The studies have been performed measuring the tune shift as a function of bunch intensity and deriving the total accelerator machine transverse impedance. For RHIC, we could obtain first promising results of impedance localization measurements as well.
Electrical impedance tomography: so close to touching the holy grail
2014-01-01
Electrical impedance tomography is a new technology giving us lung imaging that may allow lung function to be monitored at the bedside. Several applications have been studied to guide mechanical ventilation at the bedside with electrical impedance tomography. Positive end-expiratory pressure trials guided by electrical impedance tomography are relevant in terms of recruited volume or homogeneity of the lung. Tidal impedance variation is a new parameter of electrical impedance tomography that may help physicians with ventilator settings in acute respiratory distress syndrome patients. This parameter is able to identify the onset of overdistention in the nondependent part and recruitment in the dependent part. Electrical impedance tomography presents a big step forward in mechanical ventilation. PMID:25041593
Breathing detection with a portable impedance measurement system: first measurements.
Cordes, Axel; Foussier, Jerome; Leonhardt, Steffen
2009-01-01
For monitoring the health status of individuals, detection of breathing and heart activity is important. From an electrical point of view, it is known that breathing and heart activity change the electrical impedance distribution in the human body over the time due to ventilation (high impedance) and blood shifts (low impedance). Thus, it is possible to detect both important vital parameters by measuring the impedance of the thorax or the region around lung and heart. For some measurement scenarios it is also essential to detect these parameters contactless. For instance, monitoring bus drivers health could help to limit accidents, but directly connected systems limit the drivers free moving space. One measurement technology for measuring the impedance changes in the chest without cables is the magnetic impedance tomography (MIT). This article describes a portable measurement system we developed for this scenario that allows to measure breathing contactless. Furthermore, first measurements with five volunteers were performed and analyzed.
Transverse beam coupling impedance of the CERN Proton Synchrotron
Persichelli, S.; Migliorati, M.; Biancacci, N.; Gilardoni, S.; Metral, E.; Salvant, B.
2016-04-01
Beam coupling impedance is a fundamental parameter to characterize the electromagnetic interaction of a particle beam with the surrounding environment. Synchrotron machine performances are critically affected by instabilities and collective effects triggered by beam coupling impedance. In particular, transverse beam coupling impedance is expected to impact beam dynamics of the CERN Proton Synchrotron (PS), since a significant increase in beam intensity is foreseen within the framework of the LHC Injectors Upgrade (LIU) project. In this paper we describe the study of the transverse beam coupling impedance of the PS, taking into account the main sources of geometrical impedance and the contribution of indirect space charge at different energies. The total machine impedance budget, determined from beam-based dedicated machine measurement sessions, is also discussed and compared with the theoretical model.
Harmonic analysis for identification of nonlinearities in impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Kiel, M.; Bohlen, O.; Sauer, D.U. [Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University (Germany)
2008-10-30
Though impedance is only defined for linear systems, impedance spectroscopy is also successfully applied to nonlinear systems such as fuel cells and batteries. The influence of nonlinearities on measurement results in impedance spectroscopy is therefore discussed on a theoretical and simulative basis. The basis is a simplified Randles model of an electrochemical cell, on which a simulated impedance spectroscopy in galvanostatic mode is performed. For the investigation the focus is on the Butler-Vollmer equation in order to describe the nonlinearity. Furthermore, a linear model for comparison is used, in which the Butler-Volmer nonlinearity is replaced by a linear resistor to show the differences in impedance measurement. In order to find a correlation, also the occurring harmonics are observed. The results are discussed and several methods are suggested for maintaining a quasi-linear impedance measurement by controlling the amplitude of the excitation signal. (author)
Active impedance metasurface with full 360° reflection phase tuning
Zhu, Bo O.; Junming Zhao; Yijun Feng
2013-01-01
Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit ce...
Reciprocity and mutual impedance formulas within lossy cavities
Directory of Open Access Journals (Sweden)
F. Gronwald
2005-01-01
Full Text Available We discuss the validity of reciprocity and mutual impedance formulas within lossy cavities. Mutual impedance formulas are well-known from antenna theory and useful to describe the electromagnetic coupling between electromagnetic interference sources and victims. As an example the mutual impedance between two dipole antennas within a lossy rectangular cavity is calculated from a system of coupled Hallén's equations that efficiently is solved by the method of moments.
Effects of temperature on the electrical impedance of piezoelectric elements
Krishnamurthy, Karthik Chandran
1996-01-01
A structural health monitoring technique, developed at the Center for Intelligent Material Systems and Structures, employs piezoelectric (PZT) materials for tracking the structural impedance to qualitatively identify damage. The mechanical impedance of a structure is a function of the structure's mass, stiffness, damping, and structural boundary conditions. Changes in any of the above-mentioned properties lead to a change in the mechanical impedance of the structure and a chang...
On the Passivity Based Impedance Control of Flexible Joint Robots
Ott, Christian; Albu-Schäffer, Alin; Kugi, A; Hirzinger, Gerd
2008-01-01
In this work a novel type of impedance controllers for flexible joint robots is proposed. As a target impedance a desired stiffness and damping are considered without inertia shaping. For this problem two controllers of different complexity are proposed. Both have a cascaded structure with an inner torque feedback loop and an outer impedance controller. For the torque feedback, a physical interpretation as a scaling of the motor inertia is given, which allows to incorpora...
Impedance Studies on Starch-NH_4NO_3 Films
Institute of Scientific and Technical Information of China (English)
A.Muda; A.S.A; Khiar; A.K.Arof
2007-01-01
1 Results Starch is considered a suitable source material because of its inherent biodegradability,ready viability and relatively low cost[1].In the present work,polymer electrolytes based on starch have been prepared by the solution cast technique.The conductivity of the films is characterized using impedance spectroscopy at room temperatures.The imaginary impedance (Zi) versus real impedance (ZR) plot of pure starch films consists of a semicircle.The bulk resistance (Rb) was taken from the intercept o...
Qualitative Model of the Input Impedance of Rectangular Microstrip Antenna
Directory of Open Access Journals (Sweden)
Saeed Reza Ostadzadeh
Full Text Available In this paper, a fuzzy-based approach is proposed so as to predict the input impedance of the rectangular microstrip antenna. In the proposed approach, at first, behavior of single microstrip antenna is represented as simple and unchanged membership functions, and the feed probe effect on the input impedance is then extracted as simple curves so that the input impedance of microstrip antenna in despite of other existing models is efficiently predicted.
Positive impedance humidity sensors via single-component materials
Jingwen Qian; Zhijian Peng; Zhenguang Shen; Zengying Zhao; Guoliang Zhang; Xiuli Fu
2016-01-01
Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via sing...
Line Impedance Estimation Using Active and Reactive Power Variations
DEFF Research Database (Denmark)
Timbus, Adrian Vasile; Rodriguez, Pedro; Teodorescu, Remus;
2007-01-01
This paper proposes an estimation method of power system impedance based on power variations caused by a distributed power generation system (DPGS) at the point of common coupling (PCC). The proposed algorithm is computationally simple and uses the voltage variations at the point of common coupling...... (PCC) caused by the variations of the power delivered to utility network to derive the value of grid impedance. Accurate estimation of both resistive and inductive part of the impedance is obtained, as the results presented show....
Transverse impedance measurements in RHIC and the AGS
Biancacci, N; Blaskiewicz, M; Liu, C; Mernick, K; Minty, M; White, S
2014-01-01
The RHIC luminosity upgrade program aims for an increase of the polarized proton luminosity by a factor 2. To achieve this goal a significant increase in the beam intensity is foreseen. The beam coupling impedance represents a source of detrimental effects for beam quality and stability at high bunch intensities. In this paper, we evaluate the global transverse impedance in both the AGS and RHIC with measurements of tune shift as a function of bunch intensity. The results are compared to past measurements and the present impedance model. First attempts at transverse impedance localization are as well presented for the RHIC Blue ring.
Impedance characterization of PV modules in outdoor conditions
DEFF Research Database (Denmark)
Oprea, Matei-lon; Spataru, Sergiu; Sera, Dezso;
2016-01-01
Impedance spectroscopy (IS) has been used for laboratory characterizations of photovoltaic (PV) technologies under well controlled conditions. This work applies IS for outdoor characterization of PV panels, in order to observe the effect of irradiance (G) and temperature (T) on the PV module’s...... impedance spectrum, and further construct an impedance model that can link environmental changes to the model’s parameters. To achieve this, an optimized setup has been developed for long-term impedance spectra monitoring synchronised with accurate irradiance and temperature data. Preliminary results show...
Comprehensive characterization of thermophysical properties in solids using thermal impedance
Martínez-Flores, J. J.; Licea-Jiménez, L.; Pérez García, S. A.; Rodríguez-Viejo, J.; Alvarez-Quintana, J.
2012-11-01
Thermal impedance Zth(iω) is a way of defining the thermophysical characteristics and behavior of thermal systems. Existing photoacoustic and photothermal approaches based on thermal impedance formalism merely allows a partial thermal characterization of the materials (generally, either thermal diffusivity or thermal effusivity). In this work, a new approach based on the thermal impedance concept in terms of its characteristic thermal time constant is developed from thermal quadrupoles formalism. The approach outlined in this contribution presents a set of analytical equations in which through a single measurement of thermal impedance is sufficient to obtain a comprehensive characterization of the thermophysical properties of solid materials in a simple way.
Iterative Reconstruction Methods for Hybrid Inverse Problems in Impedance Tomography
DEFF Research Database (Denmark)
Hoffmann, Kristoffer; Knudsen, Kim
2014-01-01
For a general formulation of hybrid inverse problems in impedance tomography the Picard and Newton iterative schemes are adapted and four iterative reconstruction algorithms are developed. The general problem formulation includes several existing hybrid imaging modalities such as current density...... impedance imaging, magnetic resonance electrical impedance tomography, and ultrasound modulated electrical impedance tomography, and the unified approach to the reconstruction problem encompasses several algorithms suggested in the literature. The four proposed algorithms are implemented numerically in two...... be based on a theoretical analysis of the underlying inverse problem....
Proceedings of the impedance and bunch instability workshop
Energy Technology Data Exchange (ETDEWEB)
1990-04-01
This report discusses the following topics: impedance and bunch lengthening; single bunch stability in the ESRF; a longitudinal mode-coupling instability model for bunch lengthening; high-frequency behavior of longitudinal coupling impedance; beam-induced energy spreads at beam-pipe transitions; on the calculation of wake functions using MAFIA-T3 code; preliminary measurements of the bunch length and the impedance of LEP; measurements and simulations of collective effects in the CERN SPS; bunch lengthening in the SLC damping rings; and status of impedance measurements for the spring-8 storage ring.
Electrode contact impedance sensitivity to variations in geometry
International Nuclear Information System (INIS)
Electrode contact impedance is a crucial factor in physiological measurements and can be an accuracy-limiting factor when performing electroencephalography and electrical impedance tomography. In this work, standard flat electrodes and micromachined multipoint spiked electrodes are characterized with a finite-element method electromagnetic solver and the dependence of the contact impedance on geometrical factors is explored. It is found that flat electrodes are sensitive to changes in the outer skin layer properties related to hydration and thickness, while spike electrodes are not. The impedance as a function of the effective contact area, number of spikes and penetration depth has also been studied and characterized. (paper)
Impedance of the PEP-II DIP screen
Energy Technology Data Exchange (ETDEWEB)
Ng, C.-K. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Weiland, T.
1996-08-01
The vacuum chamber of a storage ring normally consists of periodically spaced pumping slots. The longitudinal impedance of slots are analyzed in this paper. It is found that although the broad-band impedance is tolerable, the narrow-band impedance, as a consequence of the periodicity of the slots, may exceed the stability limit given by natural damping with no feedback system on. Based on this analysis, the PEP-II distributed-ion-pump (DIP) screen uses long grooves with hidden holes cut halfway to reduce both the broad-band and narrow-band impedances. (author)
Frequency Bandwidth of Half-Wave Impedance Repeater
Directory of Open Access Journals (Sweden)
Marek Dvorsky
2012-01-01
Full Text Available This article brings in the second part general information about half-wave impedance repeater. The third part describes the basic functional principles of the half-wave impedance repeater using Smith chart. The main attention is focused in part four on the derivation of repeater frequency bandwidth depending on characteristics and load impedance of unknown feeder line. Derived dependences are based on the elementary features of the feeder lines with specific length. The described functionality is proved in part 4.3 by measurement of transformed impedance using vector several unbalanced feeder lines and network analyzer VNWA3+.
Impedance Localization Measurements using AC Dipoles in the LHC
Biancacci, Nicolo; Papotti, Giulia; Persson, Tobias; Salvant, Benoit; Tomás, Rogelio
2016-01-01
The knowledge of the LHC impedance is of primary importance to predict the machine performance and allow for the HL-LHC upgrade. The developed impedance model can be benchmarked with beam measurements in order to assess its validity and limit. This is routinely done, for example, moving the LHC collimator jaws and measuring the induced tune shift. In order to localize possible unknown impedance sources, the variation of phase advance with intensity between beam position monitors can be measured. In this work we will present the impedance localization measurements performed at injection in the LHC using AC dipoles as exciter as well as the underlying theory.
Line impedance estimation using model based identification technique
DEFF Research Database (Denmark)
Ciobotaru, Mihai; Agelidis, Vassilios; Teodorescu, Remus
2011-01-01
into the operation of the grid-connected power converters. This paper describes a quasi passive method for estimating the line impedance of the distribution electricity network. The method uses the model based identification technique to obtain the resistive and inductive parts of the line impedance. The quasi......The estimation of the line impedance can be used by the control of numerous grid-connected systems, such as active filters, islanding detection techniques, non-linear current controllers, detection of the on/off grid operation mode. Therefore, estimating the line impedance can add extra functions...
Distribution transformer specifiers should reconsider altering natural impedances
Energy Technology Data Exchange (ETDEWEB)
Wiegand, D
1991-02-01
Loss evaluation formulae cause modern transformer manufacturers to produce designs which are optimized to achieve the most competitive balance between evaluated losses and cost. If impedance is not presented as a constraint, its value may be quite high or low, and could lead to concern about fault protection where impedance is low, or regulation where impedance is high. The effects on impedance of evaluation formulae from three major Canadian utilities are tabulated. Reasons for the setting of constraints on impedance include the avoidance of an unacceptable level of voltage regulation by setting an upper limit, avoiding failure of the transformer due to load-side faults by applying a lower limit, coordinating system protection devices, or matching impedances of similar transformers purchased from different manufacturers. An urban type of formula will likely result in a transformer with low impedance down to 1.3%, causing concern about the ability of the transformer to withstand short circuit conditions, however the probability of this occurrence is very low, and circuit impedance increases rapidly as one moves from the tranformer to the load location. Thus, a transformer with an impedance value that appears low is not likely to make a system any less reliable, and it is recommended that the optimum loss design be accepted in such situations. 2 figs., 5 tabs.
Simulation of the low-frequency collimator impedance
Kroyer, T
2008-01-01
The low-frequency transverse collimator impedance constitutes a major part of the LHC impedance budget. In this paper numerical simulations for frequencies below 1 MHz using a commercial package are presented. From the 3D field solution of the two-wire simulations the transverse impedance is directly calculated. After a cross-check with theory for rotationally symmetric structures a geometry with two jaws and an LHC graphite collimator is examined. Furthermore, a simple physics picture that explains the principal characteristics of the impedance at high and low frequencies is given.
Electrochemical Impedance of a Battery Electrode with Anisotropic Active Particles
Song, J
2013-01-01
Electrochemical impedance spectra for battery electrodes are usually interpreted using models that assume isotropic active particles, having uniform current density and symmetric diffusivities. While this can be reasonable for amorphous or polycrystalline materials with randomly oriented grains, modern electrode materials increasingly consist of highly anisotropic, single-crystalline, nanoparticles, with different impedance characteristics. In this paper, analytical expressions are derived for the impedance of anisotropic particles with tensorial diffusivities and orientation-dependent surface reaction rates and capacitances. The resulting impedance spectrum contains clear signatures of the anisotropic material properties and aspect ratio, as well as statistical variations in any of these parameters.
Magnetically Coupled Impedance-Source Inverters
DEFF Research Database (Denmark)
Loh, Poh Chiang; Blaabjerg, Frede
2013-01-01
input-to-output gain and the presence of an impedance network. The former means a high dc-link voltage, which can stress the semiconductor switches unnecessarily. The latter leads to increases in cost and size, which similarly are undesirable. To lessen these concerns, an interesting approach is to use......Z-source inverters are a new class of inverters proposed with output voltage or current buck-boost ability. Despite their general attractiveness, there are some present limitations faced by existing Z-source inverters, most of which are linked to their requirement for low modulation ratio at high...... magnetically coupled transformers or inductors to raise the gain and modulation ratio simultaneously, while reducing the number of passive components needed. A study of the approach is now presented to show how various existing magnetically coupled inverters can be derived by applying a generic methodology...
Magnetically coupled impedance-source inverters
DEFF Research Database (Denmark)
Loh, Poh Chiang; Blaabjerg, Frede
2012-01-01
input-to-output gain, and the presence of an impedance network. The former means a high dc-link voltage, which can stress the semiconductor switches unnecessarily. The latter leads to increases in cost and size, which similarly are undesirable. To lessen these concerns, an interesting approach is to use......Z-source inverters are a new class of inverters proposed with output voltage or current buck-boost ability. Despite their general attractiveness, there are some present limitations faced by existing Z-source inverters. Most of which are linked to their requirement for low modulation ratio at high...... magnetically coupled transformers or inductors to raise the gain and modulation ratio simultaneously, while reducing the number of passive components needed. A study of the approach is now presented to show how various existing magnetically coupled inverters can be derived by applying a generic methodology...
The sensitivity in Electrical Impedance Tomography
Directory of Open Access Journals (Sweden)
A. I. Rybin
2013-12-01
Full Text Available Introduction. The concept of sensitivity in Electrical Impedance Tomography is introduced (first – fourth type. The experimental researches measuring the voltages on the phantom outline are conducted on the created layout (for uniform cylindrical vessel with brine and placed inhomogeneities in a vessel. The main part. The inverse problems are solved for simulated on PC phantom (the third type sensitivity and from measured results (the fourth type sensitivity by conductivity zones method using regularization by A. Tykhonov. The sensitivity to conductivity increasing of elements inside the phantom is significantly less than the sensitivity to resistance increasing. The results of measured voltages processing and the results of projection reconstruction (obtained from mathematical model and from measured results are described. Conclusions. The satisfactory agreements of reconstruction results between themselves and with mathematical and measured phantoms are shown.
Quartz tuning fork based microwave impedance microscopy
Cui, Yong-Tao; Ma, Eric Yue; Shen, Zhi-Xun
2016-06-01
Microwave impedance microscopy (MIM), a near-field microwave scanning probe technique, has become a powerful tool to characterize local electrical responses in solid state samples. We present the design of a new type of MIM sensor based on quartz tuning fork and electrochemically etched thin metal wires. Due to a higher aspect ratio tip and integration with tuning fork, such design achieves comparable MIM performance and enables easy self-sensing topography feedback in situations where the conventional optical feedback mechanism is not available, thus is complementary to microfabricated shielded stripline-type probes. The new design also enables stable differential mode MIM detection and multiple-frequency MIM measurements with a single sensor.
Sensing Estrogen with Electrochemical Impedance Spectroscopy
Li, Jing; Kim, Byung Kun; Im, Ji-Eun; Choi, Han Nim; Kim, Dong-Hwan; Cho, Seong In
2016-01-01
This study demonstrates the application feasibility of electrochemical impedance spectroscopy (EIS) in measuring estrogen (17β-estradiol) in gas phase. The present biosensor gives a linear response (R2 = 0.999) for 17β-estradiol vapor concentration from 3.7 ng/L to 3.7 × 10−4 ng/L with a limit of detection (3.7 × 10−4 ng/L). The results show that the fabricated biosensor demonstrates better detection limit of 17β-estradiol in gas phase than the previous report with GC-MS method. This estrogen biosensor has many potential applications for on-site detection of a variety of endocrine disrupting compounds (EDCs) in the gas phase.
The vacuum impedance and unit systems
Kitano, M
2006-01-01
In electromagnetism, the vacuum impedance $Z_0$ is a universal constant, which is as important as the velocity of light $c$ in vacuum. Unfortunately, however, its significance does not seem to be appreciated so well and sometimes the presence itself is ignored. It is partly because in the Gaussian system of units, which has widely been used for long time, $Z_0$ is a dimensionless constant and of unit magnitude. In this paper, we clarify that $Z_0$ is a fundamental parameter in electromagnetism and plays major roles in the following scenes: reorganizing the structure of the electromagnetic formula in reference to the relativity; renormalizing the quantities toward natural unit systems starting from the SI unit system; and defining the magnitudes of electromagnetic units.
Sensing Estrogen with Electrochemical Impedance Spectroscopy
Directory of Open Access Journals (Sweden)
Jing Li
2016-01-01
Full Text Available This study demonstrates the application feasibility of electrochemical impedance spectroscopy (EIS in measuring estrogen (17β-estradiol in gas phase. The present biosensor gives a linear response (R2=0.999 for 17β-estradiol vapor concentration from 3.7 ng/L to 3.7 × 10−4 ng/L with a limit of detection (3.7 × 10−4 ng/L. The results show that the fabricated biosensor demonstrates better detection limit of 17β-estradiol in gas phase than the previous report with GC-MS method. This estrogen biosensor has many potential applications for on-site detection of a variety of endocrine disrupting compounds (EDCs in the gas phase.
Relating membrane potential to impedance spectroscopy
Directory of Open Access Journals (Sweden)
Eugen Gheorghiu
2011-12-01
Full Text Available Non-invasive, label-free assessment of membrane potential of living cells is still a challenging task. The theory linking membrane potential to the low frequency α dispersion exhibited by suspensions of spherical shelled particles (presenting a net charge distribution on the inner side of the shell has been pioneered in our previous studies with emphasis on the permittivity spectra. Whereas α dispersion is related to a rather large variation exhibited by the permittivity spectrum, we report that the related decrement presented by the impedance magnitude spectrum is either extremely small, or occurs (for large cells at very small frequencies (~mHz explaining the lack of experimental bioimpedance data on the matter. We stress that appropriate choice of the parameters (as revealed by the microscopic model may enable access to membrane potential as well as to other relevant parameters when investigating living cells and charged lipid vesicles. We analyse the effect on the low frequency of the permittivity and impedance spectra of: I. Parameters pertaining to cell membrane i.e. (i membrane potential (through the amount of the net charge on the inner side of the membrane, (ii size of the cells/vesicles, (iii conductivity of the membrane; II. Parameters of the extra cellular medium (viscosity and conductivity. The applicability of the study has far reaching implications for basic (life sciences (providing non-invasive access to the dynamics of relevant cell parameters as well as for biosensing applications, e.g. assessment of cytotoxicity of a wide range of stimuli. doi:10.5617/jeb.214 J Electr Bioimp, vol. 2, pp. 93-97, 2011
Bioelectric impedance phase angle in breast carcinoma
Directory of Open Access Journals (Sweden)
Ruchi Tyagi
2014-01-01
Full Text Available Context: Worldwide breast cancer is the most frequently diagnosed life threatening cancer and the leading cause of death in women. Bioelectric impedance analysis (BIA affords an emerging opportunity to assess prognosis because of its ability to non invasively assess cell and plasma membrane structure and function by means of phase angle. Aims: To compare the phase angle between patients of breast cancer and their matched control with the help of BIA. Settings and Design: After taking clearance from ethical committee, a total of 34 female cases of histologically proven infiltrating ductal breast carcinoma were included from the surgery IPD, department of surgery. Equal numbers of the matched controls were recruited from the friends and relatives of cases. Materials and Methods: Bio Electrical Impedance Analyzer (BIA BODY STAT QUAD SCAN 4000 was used to measure resistance (R and reactance (Xc by recording a voltage drop in applied current. Phase angle is the ratio of reactance to resistance and is a measure of cell vitality. Statistical analysis used: Unpaired "t" test was applied. Results: In control group, the phase angle showed a mean of 5.479 whereas in test group, it showed a mean value of 4.726. The P value showed a significant difference (P < 0.0001. The smaller the phase angle values were higher was the tumor, nodes, metastases (TNM staging. The phase angles differed significantly from the healthy age matched control values. Conclusions: This study demonstrated that phase angle is a strong predictor of severity of breast cancer and differed significantly between the two groups.
DEFF Research Database (Denmark)
Kwon, JunBum; Wang, Xiongfei; Bak, Claus Leth;
2014-01-01
This paper addresses the harmonic compensation error problem existing with parallel connected inverter in the same grid interface conditions by means of impedance-based analysis and modeling. Unlike the single grid connected inverter, it is found that multiple parallel connected inverters and grid...... impedance can make influence to each other if they each have a harmonic compensation function. The analysis method proposed in this paper is based on the relationship between the overall output impedance and input impedance of parallel connected inverter, where controller gain design method, which can...
Grant, Caroline A; Pham, Trang; Hough, Judith; Riedel, Thomas; Stocker, Christian; Schibler, Andreas
2011-01-01
Introduction Electrical impedance tomography (EIT) has been shown to be able to distinguish both ventilation and perfusion. With adequate filtering the regional distributions of both ventilation and perfusion and their relationships could be analysed. Several methods of separation have been suggested previously, including breath holding, electrocardiograph (ECG) gating and frequency filtering. Many of these methods require interventions inappropriate in a clinical setting. This study ther...
Bogónez Franco, Francisco; Nescolarde Selva, Lexa Digna; Bragós Bardia, Ramon; Rosell Ferrer, Francisco Javier; Yandiola, Iñigo
2009-01-01
The purpose of this study is to compare measurement errors in two commercially available multi-frequency bioimpedance analyzers, a Xitron 4000B and an ImpediMed SFB7, including electrode impedance mismatch. The comparison was made using resistive electrical models and in ten human volunteers. We used three different electrical models simulating three different body segments: the right-side, leg and thorax. In the electrical models, we tested the effect of the capacitive coupling of the ...
Broadband electrical impedance spectroscopy for dynamic electrical bio-impedance characterization
Sánchez Terrones, Benjamín
2012-01-01
The electrical impedance of biological samples is known in the literature as Electrical Bioimpedance (EBI). The Electrical Bioimpedance enables to characterize physiological conditions and events that are interesting for physiological research and medical diagnosis. Although the Electrical Bioimpedance weakness is that it depends on many physiological parameters, on the other hand, it is suitable for many medical applications where minimally invasive and real-time measurements with simple and...
Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Pouliopoulos, J.; Oh, T. I.; Thiagalingam, A.; McEwan, A.
2013-04-01
Recent studies in animal models suggest that the use of small volume boluses of NaCl as an impedance contrast agent can significantly improve pulmonary perfusion imaging by Electrical Impedance Tomography (EIT). However, these studies used highly concentrated NaCl solution (20%) which may have adverse effects on the patients. In a pilot experiment, we address this problem by comparing a number of different Impedance Contrast Boluses (ICBs). Conductivity changes in the lungs of a sheep after the injection of four different ICBs were compared, including three NaCl-based ICBs and one glucose-based ICB. The following procedure was followed for each ICB. Firstly, ventilation was turned off to provide an apneic window of approximately 40s to image the conductivity changes due to the ICB. Each ICB was then injected through a pig-tail catheter directly into the right atrium. EIT images were acquired throughout the apnea to capture the conductivity change. For each ICB, the experiment was repeated three times. The three NaCl-based ICB exhibited similar behaviour in which following the injection of each of these ICBs, the conductivity of each lung predictably increased. The effect of the ICB of 5% glucose solution was inconclusive. A small decrease in conductivity in the left lung was observed in two out of three cases and none was discernible in the right lung.
Equivalent circuit models for ac impedance data analysis
Danford, M. D.
1990-01-01
A least-squares fitting routine has been developed for the analysis of ac impedance data. It has been determined that the checking of the derived equations for a particular circuit with a commercially available electronics circuit program is essential. As a result of the investigation described, three equivalent circuit models were selected for use in the analysis of ac impedance data.
Equivalent Circuits For AC-Impedance Analysis Of Corrosion
Danford, M. D.
1992-01-01
Report presents investigation of equivalent circuits for ac-impedance analysis of corrosion. Impedance between specimen and electrolyte measured as function of frequency. Data used to characterize corrosion electrochemical system in terms of equivalent circuit. Eleven resistor/capacitor equivalent-circuit models were analyzed.
Analysis and design of complex impedance transforming marchand baluns
DEFF Research Database (Denmark)
Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld M.
2014-01-01
A new type of Marchand balun is presented in this paper, which has the property of complex impedance transformation. To allow the Marchand balun to transform between arbitrary complex impedances, three reactances should be added to the circuit. A detailed analysis of the circuit gives the governing...
Induced optical metric in the non-impedance-matched media
Mousavi, S. A.; Roknizadeh, R.; Sahebdivan, S.
2016-11-01
In non-magnetic anisotropic media, the behavior of electromagnetic waves depends on the polarization and direction of the incident light. Therefore, to tame the unwanted wave responses such as polarization dependent reflections, the artificial impedance-matched media are suggested to be used in optical devices like invisibility cloak or super lenses. Nevertheless, developing the impedance-matched media is far from trivial in practice. In this paper, we are comparing the samples of both impedance-matched and non-impedance-matched (non-magnetic) media regarding their electromagnetic response in constructing a well-defined optical metric. In the case of similar anisotropic patterns, we show that the optical metric in an impedance-matched medium for unpolarized light is the same as the optical metric of an electrical birefringent medium when the extraordinary mode is concerned. By comparing the eikonal equation in an empty curved space-time and its counterparts in the medium, we have shown that a non-impedance-matched medium can resemble an optical metric for a particular polarization. As an example of non-impedance-matched materials, we are studying a medium with varying optical axis profile. We show that such a medium can be an alternative to impedance-matched materials in various optical devices.
Beam Coupling Impedances of Obstacles Protruding into Beam Pipe
Kurennoy, S S
1997-01-01
The beam coupling impedances of small obstacles protruding inside the vacuum chamber of an accelerator are calculated at frequencies for which the wavelength is large compared to a typical size of the obstacle. Formulas for a few important particular cases are presented which allow simple practical estimates of the broad-band impedance contributions from such discontinuities.
Application of dynamic impedance spectroscopy to atomic force microscopy
Directory of Open Access Journals (Sweden)
Kazimierz Darowicki, Artur Zieliński and Krzysztof J Kurzydłowski
2008-01-01
Full Text Available Atomic force microscopy (AFM is a universal imaging technique, while impedance spectroscopy is a fundamental method of determining the electrical properties of materials. It is useful to combine those techniques to obtain the spatial distribution of an impedance vector. This paper proposes a new combining approach utilizing multifrequency scanning and simultaneous AFM scanning of an investigated surface.
Surface impedance in the anomalous skin effect regime
Chrzanowski, Janusz; Kirkiewicz, Józef
2008-12-01
An analytical solution of the surface impedance is obtained using the kinetic equation with the collision integral that takes into account the Fermi liquid effects. It is assumed that the reflection of electrons is purely diffusive. Particular attention is paid to the influence of external magnetic field and polarization of the incident wave on the real and imagine part of the surface impedance.
Synthesis of adaptive impedance control for bipedal robot mechanisms
Directory of Open Access Journals (Sweden)
Petrović Milena
2008-01-01
Full Text Available The paper describes the impedance algorithm in locomotion of humanoid robot with proposed parameter modulation depending on the gate phase. The analysis shows influence of walking speed and foot elevation on regulator's parameters. Chosen criterion cares for footpath tracking and needed energy for that way of walking. The experiments give recommendation for impedance regulator tuning.
Modifying the acoustic impedance of polyurea-based composites
Nantasetphong, Wiroj; Amirkhizi, Alireza V.; Jia, Zhanzhan; Nemat-Nasser, Sia
2013-04-01
Acoustic impedance is a material property that depends on mass density and acoustic wave speed. An impedance mismatch between two media leads to the partial reflection of an acoustic wave sent from one medium to another. Active sonar is one example of a useful application of this phenomenon, where reflected and scattered acoustic waves enable the detection of objects. If the impedance of an object is matched to that of the surrounding medium, however, the object may be hidden from observation (at least directly) by sonar. In this study, polyurea composites are developed to facilitate such impedance matching. Polyurea is used due to its excellent blast-mitigating properties, easy casting, corrosion protection, abrasion resistance, and various uses in current military technology. Since pure polyurea has impedance higher than that of water (the current medium of interest), low mass density phenolic microballoon particles are added to create composite materials with reduced effective impedances. The volume fraction of particles is varied to study the effect of filler quantity on the acoustic impedance of the resulting composite. The composites are experimentally characterized via ultrasonic measurements. Computational models based on the method of dilute-randomly-distributed inclusions are developed and compared with the experimental results. These experiments and models will facilitate the design of new elastomeric composites with desirable acoustic impedances.
Flip-Chip Carrier Would Match Microwave FET Impedances
Huang, H. C.
1982-01-01
Proposed field-effect transistor consists of three cells which make up one complete FET pellet. Pellet is flip-chip mounted on carrier with source grounded gate and drain posts connected directly to impedance-matching transmission-line segments. Impedance transformers are part of mounting and contact strips.
Impedance-Source Networks for Electric Power Conversion Part II
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede;
2015-01-01
Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance...
Impedance Matching of Tapered Slot Antenna using a Dielectric Transformer
Simons, R. N.; Lee, R. Q.
1998-01-01
A new impedance matching technique for tapered slot antennas using a dielectric transformer is presented. The technique is demonstrated by measuring the input impedance, Voltage Standing Wave Ratio (VSWR) and the gain of a Vivaldi antenna (VA). Measured results at Ka-Band frequencies are presented and discussed.
Reconstruction of a potential from the impedance boundary map
Isaev, Mikhail
2012-01-01
We give formulas and equations for finding generalized scattering data for the Schr\\"odinger equation in open bounded domain at fixed energy from the impedance boundary map (or Robin-to-Robin map). Combining these results with results of the inverse scattering theory we obtain efficient methods for reconstructing potential from the impedance boundary map.
The Impedance Response of Semiconductors: An Electrochemical Engineering Perspective.
Orazem, Mark E.
1990-01-01
Shows that the principles learned in the study of mass transport, thermodynamics, and kinetics associated with electrochemical systems can be applied to the transport and reaction processes taking place within a semiconductor. Describes impedance techniques and provides several graphs illustrating impedance data for diverse circuit systems. (YP)
Electrochemical impedance spectroscopy in solid state ionics: recent advances
Boukamp, Bernard A.
2004-01-01
Electrochemical Impedance Spectroscopy (EIS) has become an important research tool in Solid State Ionics. Some new developments are highlighted: new methods of automatic parameter extraction from impedance measurements are briefly discussed. The Kramers–Kronig data validation test presents another p
Development on electromagnetic impedance function modeling and its estimation
Energy Technology Data Exchange (ETDEWEB)
Sutarno, D., E-mail: Sutarno@fi.itb.ac.id [Earth Physics and Complex System Division Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung (Indonesia)
2015-09-30
Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition
[Effects of different electrodes on bioelectrical impedance values].
Nakadomo, F; Tanaka, K; Yokoyama, T; Maeda, K
1990-01-01
Effects of different electrodes on bioelectrical impedance values measured by the Selco bioelectrical impedance plethysmograph (SIF-881, Japan) were investigated using 8 adult females (age: 35.3 +/- 7.6 yr, Ht: 156.9 +/- 3.8 cm, Wt: 57.1 +/- 9.9 kg, and hydrodensitometrically determined body fat: 29.4 +/- 6.0%). The Lectec MP3000 electrode (Liberty Carton, USA) and the Bipolar electrode (Sanwa, Japan) produced significantly higher impedance values when compared to the Disposable electrode (Adovance, Japan) and the ECG electrode (Nihon Kohden, Japan). The coefficient of variation was significantly lower for the Disposable electrode (0.8%) and the ECG electrode (0.2%) than that for the Lectec MP3000 electrode (2.3%) and the Bipolar electrode (4.9%). In conclusion, the ECG electrode provides higher bioelectrical impedance values with the highest reproducibility in the assessment of human body composition by the bioelectrical impedance plethysmography.
A Multisection Broadband Impedance Transforming Branch-Line Hybrid
Kumar, S; Danshin, T
1995-01-01
Measurements and design equations for a two section impedance transforming hybrid suitable for MMIC applications and a new method of synthesis for multisection branch-line hybrids are reported. The synthesis method allows the response to be specified either of Butterworth or Chebyshev type. Both symmetric (with equal input and output impedances) and non-symmetric (impedance transforming) designs are feasible. Starting from a given number of sections, type of response, and impedance transformation ratio and for a specified midband coupling, power division ratio, isolation or directivity ripple bandwidth, the set of constants needed for the evaluation of the reflection coefficient response is first calculated. The latter is used to define a driving point impedance of the circuit, synthesize it and obtain the branch line immittances with the use of the concept of double length unit elements (DLUE). The experimental results obtained with microstrip hybrids constructed to test the validity of the brute force optim...
Finite difference time domain implementation of surface impedance boundary conditions
Beggs, John H.; Luebbers, Raymond J.; Yee, Kane S.; Kunz, Karl S.
1991-01-01
Surface impedance boundary conditions are employed to reduce the solution volume during the analysis of scattering from lossy dielectric objects. In the finite difference solution, they also can be utilized to avoid using small cells, made necessary by shorter wavelengths in conducting media throughout the solution volume. The standard approach is to approximate the surface impedance over a very small bandwidth by its value at the center frequency, and then use that result in the boundary condition. Here, two implementations of the surface impedance boundary condition are presented. One implementation is a constant surface impedance boundary condition and the other is a dispersive surface impedance boundary condition that is applicable over a very large frequency bandwidth and over a large range of conductivities. Frequency domain results are presented in one dimension for two conductivity values and are compared with exact results. Scattering width results from an infinite square cylinder are presented as a two dimensional demonstration. Extensions to three dimensions should be straightforward.
Optical approximation in the theory of geometric impedance
Stupakov, G; Zagorodnov, I
2007-01-01
In this paper we introduce an optical approximation into the theory of impedance calculation, one valid in the limit of high frequencies. This approximation neglects diffraction effects in the radiation process, and is conceptually equivalent to the approximation of geometric optics in electromagnetic theory. Using this approximation, we derive equations for the longitudinal impedance for arbitrary offsets, with respect to a reference orbit, of source and test particles. With the help of the Panofsky-Wenzel theorem we also obtain expressions for the transverse impedance (also for arbitrary offsets). We further simplify these expressions for the case of the small offsets that are typical for practical applications. Our final expressions for the impedance, in the general case, involve two dimensional integrals over various cross-sections of the transition. We further demonstrate, for several known axisymmetric examples, how our method is applied to the calculation of impedances. Finally, we discuss the accuracy...
Impedance Modeling of Solid Oxide Fuel Cell Cathodes
DEFF Research Database (Denmark)
Mortensen, Jakob Egeberg; Søgaard, Martin; Jacobsen, Torben
2010-01-01
A 1-dimensional impedance model for a solid oxide fuel cell cathode is formulated and applied to a cathode consisting of 50/50 wt% strontium doped lanthanum cobaltite and gadolinia doped ceria. A total of 42 impedance spectra were recorded in the temperature range: 555-852°C and in the oxygen...... partial pressure range 0.028-1.00 atm. The recorded impedance spectra were successfully analyzed using the developed impedance model in the investigated temperature and oxygen partial pressure range. It is also demonstrated that the model can be used to predict how impedance spectra evolve with different...... physical parameters such as the cathode thickness. ©2010 COPYRIGHT ECS - The Electrochemical Society...
Plasmonic-Based Electrochemical Impedance Spectroscopy: Application to Molecular Binding
Lu, Jin; Wang, Wei; Wang, Shaopeng; Shan, Xiaonan; Li, Jinghong; Tao, Nongjian
2012-01-01
Plasmonic-based electrochemical impedance spectroscopy (P-EIS) is developed to investigate molecular binding on surfaces. Its basic principle relies on the sensitive dependence of surface plasmon resonance (SPR) signal on surface charge density, which is modulated by applying an AC potential to a SPR chip surface. The AC component of the SPR response gives the electrochemical impedance, and the DC component provides the conventional SPR detection. The plasmonic-based impedance measured over a range of frequency is in quantitative agreement with the conventional electrochemical impedance. Compared to the conventional SPR detection, P-EIS is sensitive to molecular binding taking place on the chip surface, and less sensitive to bulk refractive index changes or non-specific binding. Moreover, this new approach allows for simultaneous SPR and surface impedance analysis of molecular binding processes. PMID:22122514
Advanced impedance modeling of solid oxide electrochemical cells
DEFF Research Database (Denmark)
Graves, Christopher R.; Hjelm, Johan
2014-01-01
Impedance spectroscopy is a powerful technique for detailed study of the electrochemical and transport processes that take place in fuel cells and electrolysis cells, including solid oxide cells (SOCs). Meaningful analysis of impedance measurements is nontrivial, however, because a large number...... techniques to provide good guesses for the modeling parameters, like transforming the impedance data to the distribution of relaxation times (DRT), together with experimental parameter sensitivity studies, is the state-of-the-art approach to achieve good EC model fits. Here we present new impedance modeling...... electrode and 2-D gas transport models which have fewer unknown parameters for the same number of processes, (ii) use of a new model fitting algorithm, “multi-fitting”, in which multiple impedance spectra are fit simultaneously with parameters linked based on the variation of measurement conditions, (iii...
Institute of Scientific and Technical Information of China (English)
Jean-Luc Fellahi; Vincent Caille; Cyril Charron; Pierre-Hervé Deschamps-Berger; Antoine Vieillard-Baron; 黄建廷
2011-01-01
背景 胸阻抗心动图(ICG),一直被认为是一种无创性、连续性、可独立操作且经济有效的方法,用于监测心输出量.本研究比较了在静息状态下改变健康志愿者血流动力学参数时,胸阻抗心动图(Niccomo装置)与经胸超声多普勒心动图对心脏指数(CI)的测量情况.方法 本研究共纳入了25例健康志愿者(7例男性,18例女性;平均年龄36±6岁;体表面积1.75±O.17 m2),分别在3种实验条件进行测定:基础水平、呼气末正压通气(+10 cm H2O)、下半身加压(用医疗抗休克裤对腹部施加30 cm H2O的压力).结果 在所有测量中,胸阻抗心动图的信号质量>89%.胸阻抗心动图与多普勒心动图测定的心脏指数(CITTE和CICG)间存在着较弱但有统计学意义的相关性(r=0.36;P=0.002).2种技术测得的心脏指数的一致性数值为0.94 L·min-1·m-2(95%可信区间0.77～1.11);一致性可变范围为-0.47～2.35 L·min-1·m-2,误差百分率为53%.施加呼气末正压+10 cm H2O(r=0.21;P=0.31)或医疗抗休克裤(r=0.22;P=0.30)后,CITTE和CIICG的变化率之间的相关性没有统计学意义.结论 采用胸阻抗心动图与多普勒心动图测量健康志愿者静息状态下的CI,两者测量所得CI的绝对值相关性较差,缺乏一致性.在血流动力学变化时,使用Niccomo装置测量心脏指数的变化也缺乏可靠性.
DEFF Research Database (Denmark)
Nielsen, Jimmi; Hjelm, Johan
2014-01-01
It was shown through a comprehensive impedance spectroscopy study that the impedance of the classic composite LSM:YSZ (lanthanum strontium manganite and yttria stabilized zirconia) solid oxide fuel cell (SOFC) cathode can be described well with porous electrode theory. Furthermore, it was illustr...
DEFF Research Database (Denmark)
Nielsen, Jimmi; Hjelm, Johan
2014-01-01
It was shown through a comprehensive impedance spectroscopy study that the impedance of the classic composite LSM:YSZ (lanthanum strontium manganite and yttria stabilized zirconia) solid oxide fuel cell (SOFC) cathode can be described well with porous electrode theory. Furthermore, it was illustr...... electrode theory is the most suitable framework for any type of porous composite SOFC electrode evaluation.......It was shown through a comprehensive impedance spectroscopy study that the impedance of the classic composite LSM:YSZ (lanthanum strontium manganite and yttria stabilized zirconia) solid oxide fuel cell (SOFC) cathode can be described well with porous electrode theory. Furthermore, it was...... illustrated through a literature review on SOFC electrodes that porous electrode theory not only describes the classic LSM:YSZ SOFC cathode well, but SOFC electrodes in general. The extensive impedance spectroscopy study of LSM:YSZ cathodes consisted of measurements on cathodes with three different sintering...
Modified sparse regularization for electrical impedance tomography.
Fan, Wenru; Wang, Huaxiang; Xue, Qian; Cui, Ziqiang; Sun, Benyuan; Wang, Qi
2016-03-01
Electrical impedance tomography (EIT) aims to estimate the electrical properties at the interior of an object from current-voltage measurements on its boundary. It has been widely investigated due to its advantages of low cost, non-radiation, non-invasiveness, and high speed. Image reconstruction of EIT is a nonlinear and ill-posed inverse problem. Therefore, regularization techniques like Tikhonov regularization are used to solve the inverse problem. A sparse regularization based on L1 norm exhibits superiority in preserving boundary information at sharp changes or discontinuous areas in the image. However, the limitation of sparse regularization lies in the time consumption for solving the problem. In order to further improve the calculation speed of sparse regularization, a modified method based on separable approximation algorithm is proposed by using adaptive step-size and preconditioning technique. Both simulation and experimental results show the effectiveness of the proposed method in improving the image quality and real-time performance in the presence of different noise intensities and conductivity contrasts.
Electrochemical impedance spectroscopy of oxidized porous silicon
Energy Technology Data Exchange (ETDEWEB)
Mula, Guido, E-mail: guido.mula@unica.it [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Tiddia, Maria V. [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Falqui, Andrea [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Palmas, Simonetta; Mascia, Michele [Dipartimento di Ingegneria Meccanica Chimica e dei Materiali, Università degli Studi di Cagliari, Piazza d' Armi, 09126 Cagliari (Italy)
2014-04-01
We present a study of the electrochemical oxidation process of porous silicon. We analyze the effect of the layer thickness (1.25–22 μm) and of the applied current density (1.1–11.1 mA/cm{sup 2}, values calculated with reference to the external samples surface) on the oxidation process by comparing the galvanostatic electrochemical impedance spectroscopy (EIS) measurements and the optical specular reflectivity of the samples. The results of EIS were interpreted using an equivalent circuit to separate the contribution of different sample parts. A different behavior of the electrochemical oxidation process has been found for thin and thick samples: whereas for thin samples the oxidation process is univocally related to current density and thickness, for thicker samples this is no more true. Measurements by Energy Dispersive Spectroscopy using a Scanning Electron Microscopy confirmed that the inhomogeneity of the electrochemical oxidation process is increased by higher thicknesses and higher currents. A possible explanation is proposed to justify the different behavior of thin and thick samples during the electrochemical process. - Highlights: • A multidisciplinary approach on porous Si electrochemical oxidation is proposed. • Electrochemical, optical, and structural characterizations are used. • Layer thickness and oxidation current effects are shown. • An explanation of the observed behavior is proposed.
Electrochemical impedance spectroscopy of oxidized porous silicon
International Nuclear Information System (INIS)
We present a study of the electrochemical oxidation process of porous silicon. We analyze the effect of the layer thickness (1.25–22 μm) and of the applied current density (1.1–11.1 mA/cm2, values calculated with reference to the external samples surface) on the oxidation process by comparing the galvanostatic electrochemical impedance spectroscopy (EIS) measurements and the optical specular reflectivity of the samples. The results of EIS were interpreted using an equivalent circuit to separate the contribution of different sample parts. A different behavior of the electrochemical oxidation process has been found for thin and thick samples: whereas for thin samples the oxidation process is univocally related to current density and thickness, for thicker samples this is no more true. Measurements by Energy Dispersive Spectroscopy using a Scanning Electron Microscopy confirmed that the inhomogeneity of the electrochemical oxidation process is increased by higher thicknesses and higher currents. A possible explanation is proposed to justify the different behavior of thin and thick samples during the electrochemical process. - Highlights: • A multidisciplinary approach on porous Si electrochemical oxidation is proposed. • Electrochemical, optical, and structural characterizations are used. • Layer thickness and oxidation current effects are shown. • An explanation of the observed behavior is proposed
Electrical Impedance Tomography During Mechanical Ventilation.
Walsh, Brian K; Smallwood, Craig D
2016-10-01
Electrical impedance tomography (EIT) is a noninvasive, non-radiologic imaging modality that may be useful for the quantification of lung disorders and titration of mechanical ventilation. The principle of operation is based on changes in electrical conductivity that occur as a function of changes in lung volume during ventilation. EIT offers potentially important benefits over standard imaging modalities because the system is portable and non-radiologic and can be applied to patients for long periods of time. Rather than providing a technical dissection of the methods utilized to gather, compile, reconstruct, and display EIT images, the present article seeks to provide an overview of the clinical application of this technology as it relates to monitoring mechanical ventilation and providing decision support at the bedside. EIT has been shown to be useful in the detection of pneumothoraces, quantification of pulmonary edema and comparison of distribution of ventilation between different modes of ventilation and may offer superior individual titration of PEEP and other ventilator parameters compared with existing approaches. Although application of EIT is still primarily done within a research context, it may prove to be a useful bedside tool in the future. However, head-to-head comparisons with existing methods of mechanical ventilation titration in humans need to be conducted before its application in general ICUs can be recommended. PMID:27682815
Journal and Wave Bearing Impedance Calculation Software
Hanford, Amanda; Campbell, Robert
2012-01-01
The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.
Summary of Human Ankle Mechanical Impedance During Walking
Rouse, Elliott J.; Krebs, Hermano Igo
2016-01-01
The human ankle joint plays a critical role during walking and understanding the biomechanical factors that govern ankle behavior and provides fundamental insight into normal and pathologically altered gait. Previous researchers have comprehensively studied ankle joint kinetics and kinematics during many biomechanical tasks, including locomotion; however, only recently have researchers been able to quantify how the mechanical impedance of the ankle varies during walking. The mechanical impedance describes the dynamic relationship between the joint position and the joint torque during perturbation, and is often represented in terms of stiffness, damping, and inertia. The purpose of this short communication is to unify the results of the first two studies measuring ankle mechanical impedance in the sagittal plane during walking, where each study investigated differing regions of the gait cycle. Rouse et al. measured ankle impedance from late loading response to terminal stance, where Lee et al. quantified ankle impedance from pre-swing to early loading response. While stiffness component of impedance increases significantly as the stance phase of walking progressed, the change in damping during the gait cycle is much less than the changes observed in stiffness. In addition, both stiffness and damping remained low during the swing phase of walking. Future work will focus on quantifying impedance during the “push off” region of stance phase, as well as measurement of these properties in the coronal plane. PMID:27766187
Frequency dependent elastic impedance inversion for interstratified dispersive elastic parameters
Zong, Zhaoyun; Yin, Xingyao; Wu, Guochen
2016-08-01
The elastic impedance equation is extended to frequency dependent elastic impedance equation by taking partial derivative to frequency. With this equation as the forward solver, a practical frequency dependent elastic impedance inversion approach is presented to implement the estimation of the interstratified dispersive elastic parameters which makes full use of the frequency information of elastic impedances. Three main steps are included in this approach. Firstly, the elastic Bayesian inversion is implemented for the estimation of elastic impedances from different incident angle. Secondly, with those estimated elastic impedances, their variations are used to estimate P-wave velocity and S-wave velocity. Finally, with the prior elastic impedance and P-wave and S-wave velocity information, the frequency dependent elastic variation with incident angle inversion is presented for the estimation of the interstratified elastic parameters. With this approach, the interstratified elastic parameters rather than the interface information can be estimated, making easier the interpretation of frequency dependent seismic attributes. The model examples illustrate the feasibility and stability of the proposed method in P-wave velocity dispersion and S-wave velocity dispersion estimation. The field data example validates the possibility and efficiency in hydrocarbon indication of the estimated P-wave velocity dispersion and S-wave velocity dispersion.
Geometric Beam Coupling Impedance of LHC Secondary Collimators
Frasciello, O; Zobov, M; Grudiev, A; Mounet, N; Salvant, B
2014-01-01
The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep under control beam instabilities and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are the main impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were by about a factor of 2 higher with respect to the theoretical predictions based on the current model. Up to now the resistive wall impedance has been considered as the major impedance contribution for collimators. By carefully simulating their geometric impedance we show that for the graphite collimators with half-gaps higher than 10 mm the geometric impedance exceeds the resistive wall one. In turn, for the tungsten collimators the geometric impedance dominates for all used gap values. Hence, i...
Impedances and power losses for an off-axis beam
Kurennoy, S S
1996-01-01
A method for calculating coupling impedances and power losses for off-axis beams is developed. It is applied to calculate impedances of small localized discontinuities like holes and slots, as well as the impedance due to a finite resistivity of chamber walls, in homogeneous chambers with an arbitrary shape of the chamber cross section. The approach requires to solve a two-dimensional electrostatic problem, which can be easily done numerically in the general case, while for some particular cases analytical solutions are obtained.
Note: electrode polarization of Galinstan electrodes for liquid impedance spectroscopy.
Mellor, Brett L; Kellis, Nathan A; Mazzeo, Brian A
2011-04-01
Electrode polarization is a significant obstacle in the impedance measurements of ionic liquids. An atomically smooth electrode surface could potentially reduce unwanted impedance contributions from electrode polarization. Liquid metal electrodes were formed by adhering Galinstan to acrylic plates in a parallel-plate capacitor arrangement. Electrode polarization was compared to a similar cell with stainless steel electrodes. The impedance of salt and protein solutions (β-lactoglobulin) was measured from 40 Hz to 110 MHz. Because of oxide layer formation, the performance of the Galinstan electrode is significantly different than the theoretical ideal.
Impedance-Source Networks for Electric Power Conversion Part I
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede;
2015-01-01
power chain, which may improve the reliability and performance of the power system. The first part of this paper provides a comprehensive review of the various impedance-source-networks-based power converters and discusses the main topologies from an application point of view. This review paper...... is the first of its kind with the aim of providing a “one-stop” information source and a selection guide on impedance-source networks for power conversion for researchers, designers, and application engineers. A comprehensive review of various modeling, control, and modulation techniques for the impedance...
Impedance coordinative control for cascaded converter in bidirectional application
DEFF Research Database (Denmark)
Tian, Yanjun; Loh, Poh Chiang; Deng, Fujin;
2016-01-01
-converter is constant-power-controlled, and hence has different impedance characteristics when its power reverses. To lessen such constant-power effects, a control scheme that can coordinate impedance behaviors of the two sub-converters is proposed. The idea is to reshape the lowfrequency negative impedance...... of the constant-power subconverter to a positive resistance needed for neutralizing stability differences between the two directions of power flow. A smooth power reversal can thus be ensured, as verified through simulations and experiments performed with a scaled-down 400-W laboratory prototype....
Low profile conformal antenna arrays on high impedance substrate
Singh, Hema; Jha, Rakesh Mohan
2016-01-01
This book presents electromagnetic (EM) design and analysis of dipole antenna array over high impedance substrate (HIS). HIS is a preferred substrate for low-profile antenna design, owing to its unique boundary conditions. Such substrates permit radiating elements to be printed on them without any disturbance in the radiation characteristics. Moreover HIS provides improved impedance matching, enhanced bandwidth, and increased broadside directivity owing to total reflection from the reactive surface and high input impedance. This book considers different configurations of HIS for array design on planar and non-planar high-impedance surfaces. Results are presented for cylindrical dipole, printed dipole, and folded dipole over single- and double-layered square-patch-based HIS and dogbone-based HIS. The performance of antenna arrays is analyzed in terms of performance parameters such as return loss and radiation pattern. The design presented shows acceptable return loss and mainlobe gain of radiation pattern. Thi...
Beam coupling impedances of fast transmission-line kickers.
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. (Sergey)
2002-01-01
Fast transmission-line kickers contain no ferrite and consist of two long metallic parallel plates supported by insulators inside a beam pipe. A beam is deflected by both the electric and magnetic fields of a TEM wave created by a pulse propagating along the strips in the direction opposite to the beam. Computations of the beam coupling impedances for such structures are difficult because of their length. In the paper, the beam coupling impedances of transmission-line kickers are calculated by combining analytical and numerical methods: the wake potentials computed in short models are extended analytically to obtain the wakes for the long kickers, and then the corresponding beam impedances are derived. At very low frequencies the results are compared with simple analytical expressions for the coupling impedances of striplines in beam position monitors.
Coupling Impedances of Small Discontinuities: Dependence on Beam Velocity
Kurennoy, S S
2006-01-01
The beam coupling impedances of small discontinuities of an accelerator vacuum chamber have been calculated [e.g., S.S. Kurennoy, R.L. Gluckstern, and G.V. Stupakov, Phys. Rev. E 52, 4354 (1995)] for ultrarelativistic beams using the Bethe diffraction theory. Here we extend the results to an arbitrary beam velocity. The vacuum chamber is assumed to have an arbitrary, but uniform along the beam path, cross section. The longitudinal and transverse coupling impedances are derived in terms of series over cross-section eigenfunctions, while the discontinuity shape enters via its polarizabilities. Simple explicit formulas for two important particular cases - circular and rectangular chamber cross sections - are presented. The impedance dependence on the beam velocity exhibits some unusual features: for example, the reactive impedance, which dominates in the ultrarelativistic limit, can vanish at a certain beam velocity, or its magnitude can exceed the ultrarelativistic value many times. In addition, we demonstrate ...
Smart mug to measure hand's geometrical mechanical impedance.
Hondori, Hossein Mousavi; Tech, Ang Wei
2011-01-01
A novel device, which looks like a mug, has been proposed for measuring the impedance of human hand. The device is designed to have convenient size and light weight similar to an ordinary coffee mug. It contains a 2-axis inertia sensor to monitor vibration and a small motor to carry an eccentric mass (m=100 gr, r=2 cm, rpm=600). The centrifugal force due to the rotating mass applies a dynamic force to the hand that holds the mug. Correlation of the acceleration signals with the perturbing force gives the geometrical mechanical impedance. Experimental results on a healthy subject shows that impedance is posture dependant while it changes with the direction of the applied perturbing force. For nine postures the geometrical impedance is obtained all of which have elliptical shapes. The method can be used for assessment of spasticity and monitoring stability in patients with stroke or similar problems.
EXPERIMENTAL RESEARCH ON EVALUATING STRUCTURE DAMAGE WITH PIEZOELECTRIC DYNAMIC IMPEDANCE
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A dynamic impedance-based structural health monitoring technique is introduced. According to the direct and the converse piezoelectric property of piezoelectric materials, the piezoceramic ( PZT ) can be used as an actuator and a sensor synchronously. If damages like cracks, holes, debonding or loose connections are presented in the structure, the physical variations of the structure will cause the mechanical impedance modified. On the basis of introducing the principle and the theory, the experiment and the analysis on some damages of the structure are studied by means of the dynamic impedance technique. On the view of experiment, kinds of structural damages are evaluated by the information of dynamic impedance in order to validate the feasibility of the method.
Analysis of impedance characteristics of IMPATT-generators
Directory of Open Access Journals (Sweden)
F. B. Bereziuk
2007-10-01
Full Text Available Model of power solid-state oscillators in a millimeter wave band is presented. This model based on non-stationary impedance characteristics of pulse oscillating impact avalanche transit time diodes.
Motion discrimination of throwing a baseball using forearm electrical impedance
International Nuclear Information System (INIS)
The extroversion or hyperextension of elbow joint cause disorders of elbow joint in throwing a baseball. A method, which is easy handling and to measure motion objectively, can be useful for evaluation of throwing motion. We investigated a possibility of motion discrimination of throwing a baseball using electrical impedance method. The parameters of frequency characteristics (Cole-Cole arc) of forearm electrical impedance were measured during four types of throwing a baseball. Multiple discriminant analysis was used and the independent variables were change ratios of 11 parameters of forearm electrical impedance. As results of 120 data with four types of throwing motion in three subjects, hitting ratio was very high and 95.8%. We can expect to discriminate throwing a baseball using multiple discriminant analysis of impedance parameters.
Motion discrimination of throwing a baseball using forearm electrical impedance
Nakamura, Takao; Kusuhara, Toshimasa; Yamamoto, Yoshitake
2013-04-01
The extroversion or hyperextension of elbow joint cause disorders of elbow joint in throwing a baseball. A method, which is easy handling and to measure motion objectively, can be useful for evaluation of throwing motion. We investigated a possibility of motion discrimination of throwing a baseball using electrical impedance method. The parameters of frequency characteristics (Cole-Cole arc) of forearm electrical impedance were measured during four types of throwing a baseball. Multiple discriminant analysis was used and the independent variables were change ratios of 11 parameters of forearm electrical impedance. As results of 120 data with four types of throwing motion in three subjects, hitting ratio was very high and 95.8%. We can expect to discriminate throwing a baseball using multiple discriminant analysis of impedance parameters.
Impedance of rigid bodies in one-dimensional elastic collisions
Santos, Janilo; Nelson, Osman Rosso
2012-01-01
In this work we study the problem of one-dimensional elastic collisions of billiard balls, considered as rigid bodies, in a framework very different from the classical one presented in text books. Implementing the notion of impedance matching as a way to understand eficiency of energy transmission in elastic collisions, we find a solution which frames the problem in terms of this conception. We show that the mass of the ball can be seen as a measure of its impedance and verify that the problem of maximum energy transfer in elastic collisions can be thought of as a problem of impedance matching between different media. This approach extends the concept of impedance, usually associated with oscillatory systems, to system of rigid bodies.
Generalised Impedance Converters with only Transconductance Elements and Grounded Capacitors
Directory of Open Access Journals (Sweden)
Iqbal A. Khan
2002-01-01
capacitors in the realisation of continuous time filters lend to electronic tunability and compatibility to integration in contemporary IC technologies. The generalised impedance converters are also verified using PSPICE-based simulation.
Electrochemical Impedance Spectra of Particulate Matter and Smoke
Energy Technology Data Exchange (ETDEWEB)
Osite, A; Katkevich, J; Viksna, A; Vaivars, G, E-mail: agnese.osite@lu.lv [Department of Chemistry, University of Latvia, Riga, Valdemara Street 48, Latvia, LV-1013 (Latvia)
2011-06-23
Particularly aerosol particles of fine dimensions are recognized to have a strong impact on the climate change, on the atmospheric energy budget, on the environment and on human health. In this study coarse aerosol particles with different black carbon mass concentrations were investigated by electrochemical impedance spectroscopy. Present work describes preparation of particulate matter samples for impedance measurements, the principles of the structure of electrochemical cell and the relationship between parameters obtained from impedance spectra and black carbon mass concentration. Using complex electrode it is possible to obtain qualitative impedance spectra of particulate matter which were sampled on glass fibre filters. The values of equivalent circuit's elements (R, Q and n) are depending on sampled mass of black carbon and mass of other carbonaceous components which are not black as well as they depend on filter pore packing with solid particles.
Experiences with a two terminal-pair digital impedance bridge
Callegaro, Luca; D'Elia, Vincenzo; Kampik, Marian; Kim, Dan Bee; Ortolano, Massimo; Pourdanesh, Faranak
2014-01-01
This paper describes the realization of a two terminal-pair digital impedance bridge and the test measurements performed with it. The bridge, with a very simple architecture, is based on a commercial two-channel digital signal synthesizer and a synchronous detector. The bridge can perform comparisons between impedances having arbitrary phase and magnitude ratio: its balance is achieved automatically in less than a minute. $R$-$C$ comparisons with calibrated standards, at kHz frequency and 100...
A valveless micro impedance pump driven by electromagnetic actuation
Rinderknecht, Derek; Hickerson, Anna Iwaniec; Gharib, Morteza
2005-01-01
Over the past two decades, a variety of micropumps have been explored for various applications in microfluidics such as control of pico- and nanoliter flows for drug delivery as well as chemical mixing and analysis. We present the fabrication and preliminary experimental studies of flow performance on the micro impedance pump, a previously unexplored method of pumping fluid on the microscale. The micro impedance pump was constructed of a simple thin-walled tube coupled at either end to glass ...
Beam coupling impedances of obstacles protruding into a beam pipe
Kurennoy, Sergey S.
1997-03-01
The beam coupling impedances of small obstacles protruding inside the vacuum chamber of an accelerator are calculated at frequencies for which the wavelength is large compared to a typical size of the obstacle. Formulas for a few important particular cases including both essentially three-dimensional objects like a post or a mask and axisymmetric irises, are presented. These results allow simple practical estimates of the broadband impedance contributions from such discontinuities.
Beam coupling impedances of obstacles protruding into a beam pipe
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.S. [AOT-1, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
1997-03-01
The beam coupling impedances of small obstacles protruding inside the vacuum chamber of an accelerator are calculated at frequencies for which the wavelength is large compared to a typical size of the obstacle. Formulas for a few important particular cases including both essentially three-dimensional objects like a post or a mask and axisymmetric irises, are presented. These results allow simple practical estimates of the broadband impedance contributions from such discontinuities. {copyright} {ital 1997} {ital The American Physical Society}
An Electrochemical Impedance Spectroscopy System for Monitoring Pineapple Waste Saccharification
Claudia Conesa; Javier Ibáñez Civera; Lucía Seguí; Pedro Fito; Nicolás Laguarda-Miró
2016-01-01
[EN] Electrochemical impedance spectroscopy (EIS) has been used for monitoring the enzymatic pineapple waste hydrolysis process. The system employed consists of a device called Advanced Voltammetry, Impedance Spectroscopy & Potentiometry Analyzer (AVISPA) equipped with a specific software application and a stainless steel double needle electrode. EIS measurements were conducted at different saccharification time intervals: 0, 0.75, 1.5, 6, 12 and 24 h. Partial least squares (PLS) ...
Effects of Human Arm Impedance on Dynamics Learning and Generalization
Darainy, Mohammad; Mattar, Andrew A. G.; Ostry, David J.
2009-01-01
Previous studies have demonstrated anisotropic patterns of hand impedance under static conditions and during movement. Here we show that the pattern of kinematic error observed in studies of dynamics learning is associated with this anisotropic impedance pattern. We also show that the magnitude of kinematic error associated with this anisotropy dictates the amount of motor learning and, consequently, the extent to which dynamics learning generalizes. Subjects were trained to reach to visual t...
A Simplified Algorithm for Impedance Calculation of Arbitrarily Shaped Radiators
Institute of Scientific and Technical Information of China (English)
YANG Jun; SHA Kan; GAN Woon-Seng; YAN Yong-Hong; TIAN Jing
2005-01-01
@@ It is well known that a computationally efficient model for calculation of radiation impedance of an arbitrarily shaped piston has been developed. We simplify the proposed algorithm by using geometric characteristics and intrinsic relationship between the analytic expressions. As an example, the method accuracy is illustrated and the radiation impedance of a right-angled triangular piston is calculated. The numerical results are in good agreement with that obtained directly by the quadruple integral method.
A Batteryless Sensor ASIC for Implantable Bio-impedance Applications
Rodriguez, Saul; Ollmar, Stig; Waqar, Muhammad; Rusu, Ana
2015-01-01
The measurement of the biological tissue's electrical impedance is an active research field that has attracted a lot of attention during the last decades. Bio-impedances are closely related to a large variety of physiological conditions; therefore, they are useful for diagnosis and monitoring in many medical applications. Measuring living tissues, however, is a challenging task that poses countless technical and practical problems, in particular if the tissues need to be measured under the sk...
Impedance-based monitoring for tissue engineering applications
DEFF Research Database (Denmark)
Canali, Chiara; Heiskanen, Arto; Martinsen, Ø.G.;
2015-01-01
Impedance is a promising technique for sensing the overall process of tissue engineering. Different electrode configurations can be used to characterize the scaffold that supports cell organization in terms of hydrogel polymerization and degree of porosity, monitoring cell loading, cell prolifera......Impedance is a promising technique for sensing the overall process of tissue engineering. Different electrode configurations can be used to characterize the scaffold that supports cell organization in terms of hydrogel polymerization and degree of porosity, monitoring cell loading, cell...
MD 349: Impedance Localization with AC-dipole
Biancacci, Nicolo; Metral, Elias; Salvant, Benoit; Papotti, Giulia; Persson, Tobias Hakan Bjorn; Tomas Garcia, Rogelio; CERN. Geneva. ATS Department
2016-01-01
The purpose of this MD is to measure the distribution of the transverse impedance of the LHC by observing the phase advance variation with intensity between the machine BPMs. Four injected bunches with different intensities are excited with an AC dipole and the turn by turn data is acquired from the BPM system. Through post-processing analysis the phase variation along the machine is depicted and, from this information, first conclusions of the impedance distribution can be drawn.
Impedance of tissue-mimicking phantom material under compression
Barry Belmont; Dodde, Robert E.; Shih, Albert J.
2013-01-01
The bioimpedance of tissues under compression is a field in need of study. While biological tissues can become compressed in a myriad of ways, very few experiments have been conducted to describe the relationship between the passive electrical properties of a material (impedance/admittance) during mechanical deformation. Of the investigations that have been conducted, the exodus of fluid from samples under compression has been thought to be the cause of changes in impedance, though until now ...
Ultrasonic flow measurement and wall acoustic impedance effects.
Willatzen, M
2004-03-01
An examination of the influence of wall acoustic impedance effects on sound propagation in flowing liquids confined by cylindrical walls is presented. Special focus is given to the importance of the wall acoustic impedance value for ultrasonic flow meter performance. The mathematical model presented allows any radially-dependent axial flow profile to be examined in the linear flow acoustics regime where fluid flow speed is much smaller than the fluid sound speed everywhere in the fluid medium. PMID:14996531
Impedance Analysis of Longitudinal Bunch Shape Measurements at PLS
Hwang, Ilmoon; Kim Eun San; Yoon, Moohyun
2005-01-01
We measured the longitudinal bunch shape by streak camera at 2.5 GeV Pohang Light Source. The impedances estimated by a series R+L model indicate a resistance R= 960 ohm, an inductance L= 80 nH and a longitudinal impedance Z/n= 0.53 ohm. The scaling law for the bunch lengthenig is expressed as I0
Positive impedance humidity sensors via single-component materials.
Qian, Jingwen; Peng, Zhijian; Shen, Zhenguang; Zhao, Zengying; Zhang, Guoliang; Fu, Xiuli
2016-05-06
Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via single-component WO3-x crystals. The resistance of WO3-x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. And it was revealed that the positive humidity impedance was driven by the defects of oxygen vacancy. This result will extend the application field of humidity sensors, because the positive humidity impedance sensors would be more energy-efficient, easier to be miniaturized and electrically safer than their negative counterparts for their lower operation voltages. And we believe that constructing vacancies in semiconducting materials is a universal way to fabricate positive impedance humidity sensors.
Validity of estimating limb muscle volume by bioelectrical impedance.
Miyatani, M; Kanehisa, H; Masuo, Y; Ito, M; Fukunaga, T
2001-07-01
The present study aimed to investigate the validity of estimating muscle volume by bioelectrical impedance analysis. Bioelectrical impedance and series cross-sectional images of the forearm, upper arm, lower leg, and thigh on the right side were determined in 22 healthy young adult men using a specially designed bioelectrical impedance acquisition system and magnetic resonance imaging (MRI) method, respectively. The impedance index (L(2)/Z) for every segment, calculated as the ratio of segment length squared to the impedance, was significantly correlated to the muscle volume measured by MRI, with r = 0.902-0.976 (P estimation was 38.4 cm(3) for the forearm, 40.9 cm(3) for the upper arm, 107.2 cm(3) for the lower leg, and 362.3 cm(3) for the thigh. Moreover, isometric torque developed in elbow flexion or extension and knee flexion or extension was significantly correlated to the L(2)/Z values of the upper arm and thigh, respectively, with correlation coefficients of 0.770-0.937 (P knee flexors or extensors. Thus the present study indicates that bioelectrical impedance analysis may be useful to predict the muscle volume and to investigate possible relations between muscle size and strength capability in a limited segment of the upper and lower limbs.
Positive impedance humidity sensors via single-component materials
Qian, Jingwen; Peng, Zhijian; Shen, Zhenguang; Zhao, Zengying; Zhang, Guoliang; Fu, Xiuli
2016-05-01
Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via single-component WO3-x crystals. The resistance of WO3-x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. And it was revealed that the positive humidity impedance was driven by the defects of oxygen vacancy. This result will extend the application field of humidity sensors, because the positive humidity impedance sensors would be more energy-efficient, easier to be miniaturized and electrically safer than their negative counterparts for their lower operation voltages. And we believe that constructing vacancies in semiconducting materials is a universal way to fabricate positive impedance humidity sensors.
Damage detection technique by measuring laser-based mechanical impedance
Energy Technology Data Exchange (ETDEWEB)
Lee, Hyeonseok; Sohn, Hoon [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (Daehak-ro 291, Yuseong-gu, Daejeon 305-701) (Korea, Republic of)
2014-02-18
This study proposes a method for measurement of mechanical impedance using noncontact laser ultrasound. The measurement of mechanical impedance has been of great interest in nondestructive testing (NDT) or structural health monitoring (SHM) since mechanical impedance is sensitive even to small-sized structural defects. Conventional impedance measurements, however, have been based on electromechanical impedance (EMI) using contact-type piezoelectric transducers, which show deteriorated performances induced by the effects of a) Curie temperature limitations, b) electromagnetic interference (EMI), c) bonding layers and etc. This study aims to tackle the limitations of conventional EMI measurement by utilizing laser-based mechanical impedance (LMI) measurement. The LMI response, which is equivalent to a steady-state ultrasound response, is generated by shooting the pulse laser beam to the target structure, and is acquired by measuring the out-of-plane velocity using a laser vibrometer. The formation of the LMI response is observed through the thermo-mechanical finite element analysis. The feasibility of applying the LMI technique for damage detection is experimentally verified using a pipe specimen under high temperature environment.
Optical approximation in the theory of geometric impedance
Stupakov, G.; Bane, K. L. F.; Zagorodnov, I.
2007-05-01
In this paper we introduce an optical approximation into the theory of impedance calculation, one valid in the limit of high frequencies. This approximation neglects diffraction effects in the radiation process, and is conceptually equivalent to the approximation of geometric optics in electromagnetic theory. Using this approximation, we derive equations for the longitudinal impedance for arbitrary offsets, with respect to a reference orbit, of source and test particles. With the help of the Panofsky-Wenzel theorem, we also obtain expressions for the transverse impedance (also for arbitrary offsets). We further simplify these expressions for the case of the small offsets that are typical for practical applications. Our final expressions for the impedance, in the general case, involve two-dimensional integrals over various cross sections of the transition. We further demonstrate, for several known axisymmetric examples, how our method is applied to the calculation of impedances. Finally, we discuss the accuracy of the optical approximation and its relation to the diffraction regime in the theory of impedance.
Skin impedance comparisons of electrodes for electro-oculography.
Lee, J B; Reinecke, R D
1991-01-01
In an effort to define the most comfortable electrode needing the simplest skin preparation with low and stable skin impedance, we compared the impedance between skin electrodes and Stat-Trace II St-102 EKG electrodes (Niko Med USA, New Brunswick, NJ)--the latter being renamed "dry electrodes" because they are used without electrolyte paste--on 12 normal subjects with two different skin preparations, with and without alcohol. The dry electrodes were found to have lower impedance than the skin electrodes. With each skin preparation the alcohol scored better, 7.2 kOhm vs 16.5 kOhm, respectively, and "no preparation" worse, 13.8 kOhm vs 22.7 kOhm, respectively, (but still acceptable when the dry electrode was used). The dry electrode's impedance was quite stable from the moment of application while the skin electrode's impedance drifted dramatically for 30 minutes. If the dry electrode was halved in area of skin contact, as often is necessary with the nasal electrode in children, the impedance rose proportionally but remained acceptable. We conclude that the new dry electrodes give us improved electro-oculography records and suggest their use, particularly for infants and young children where ease of application and simple skin preparation are particularly important.
[Experimental study on electrical impedance properties of human hepatoma cells].
Fang, Yun; Tang, Zhiyuan; Zhang, Qian; Zhao, Xin; Ma, Qing
2014-10-01
The AC impedance of human hepatoma SMMC-7721 cells were measured in our laboratory by Agilent 4294A impedance analyzer in the frequency range of 0.01-100 MHz. And then the effect of hematocrit on electrical impedance characteristics of hepatoma cells was observed by electrical impedance spectroscopy, Bode diagram, Nyquist diagram and Nichols diagram. The results showed that firstly, there is a frequency dependence, i.e., the increment of real part and the imaginary part of complex electrical impedance (δZ', δZ"), the increment of the amplitude modulus of complex electrical impedance (δ[Z *]) and phase angle (δθ) were all changed with the increasing frequency. Secondly, it showed cell volume fraction (CVF) dependence, i. e. , the increment of low-frequency limit (δZ'0, δ[Z*] 0), peak (δZ"(p), δθ(p)), area and radius (Nyquist diagram, Nichols diagram) were all increased along with the electric field frequency. Thirdly, there was the presence of two characteristic frequencies: the first characteristic frequency (f(c1)) and the second characteristic frequency (f(c2)), which were originated respectively in the polarization effects of two interfaces that the cell membrane and extracellular fluid, cell membrane and cytoplasm. A conclusion can be drawn that the electrical impedance spectroscopy is able to be used to observe the electrical characteristics of human hepatoma cells, and therefore this method can be used to investigate the electrophysiological mechanisms of liver cancer cells, and provide research tools and observation parameters, and it also has important theoretical value and potential applications for screening anticancer drugs. PMID:25764724
Piezogenerator impedance matching using Mason equivalent circuit for harvester identification
Li, Yang; Richard, Claude
2014-04-01
Any piezoelectric generator structure can be modeled close to its resonance by an equivalent circuit derived from the well known Mason equivalent circuit. This equivalent circuit can therefore be used in order to optimize the harvested power using usual electrical impedance matching. The objective of this paper is to illustrate the full process leading to the definition of the proper passive load allowing the optimization of the harvested energy of any harvesting device. First, the electric equivalent circuit of the generator is derived from the Mason equivalent circuit of a seismic harvester. Theoretical ideal impedance matching and optimal load analyze is then given emphasizing the fact that for a given acceleration a constant optimal output power is achievable for any frequency as long as the optimal load is feasible. Identification of the equivalent circuit of an experimental seismic harvester is then derived and matched impedance is defined both theoretically and experimentally. Results demonstrate that an optimal load can always be obtained and that the corresponding output power is constant. However, it is very sensitive to this impedance, and that even if impedance matching is a longtime well known technique, it is not really experimentally and practically achievable.
Determination of soil ionic concentration using impedance spectroscopy
Pandey, Gunjan; Kumar, Ratnesh; Weber, Robert J.
2013-05-01
This paper presents a novel approach to estimate the soil ionic concentration by way of multi-frequency impedance measurements and using the quasi-static dielectric mixing models to infer the various ionic concentrations. In our approach, the permittivity of the soil dielectric mixture is measured using impedance spectroscopy and the results are used as input parameters to dielectric mixing models, combined with the debye-type dielectric relaxation models. We observe that the dielectric mixing models work well for low RF (radio-frequency) range and help in determining the individual ionic concentration in a multi-component soil mixture. Using the fact that the permittivity of a dielectric mixture is proportional to its impedance, we validated our approach by making multi-frequency impedance measurements of a soil mixture at different concentrations of various components. The method provides a good estimate of individual components such as air, water and ions like nitrates. While the paper is written with the perspective of soil constituent concentration determination, the underlying principle of determining individual component concentration using multi-frequency impedance measurement is applicable more generally in areas such as characterizing biological systems like pathogens, quality control of pharmaceuticals etc.
Uncertainty Analysis of the Grazing Flow Impedance Tube
Brown, Martha C.; Jones, Michael G.; Watson, Willie R.
2012-01-01
This paper outlines a methodology to identify the measurement uncertainty of NASA Langley s Grazing Flow Impedance Tube (GFIT) over its operating range, and to identify the parameters that most significantly contribute to the acoustic impedance prediction. Two acoustic liners are used for this study. The first is a single-layer, perforate-over-honeycomb liner that is nonlinear with respect to sound pressure level. The second consists of a wire-mesh facesheet and a honeycomb core, and is linear with respect to sound pressure level. These liners allow for evaluation of the effects of measurement uncertainty on impedances educed with linear and nonlinear liners. In general, the measurement uncertainty is observed to be larger for the nonlinear liners, with the largest uncertainty occurring near anti-resonance. A sensitivity analysis of the aerodynamic parameters (Mach number, static temperature, and static pressure) used in the impedance eduction process is also conducted using a Monte-Carlo approach. This sensitivity analysis demonstrates that the impedance eduction process is virtually insensitive to each of these parameters.
Coupling impedances of small discontinuities: Dependence on beam velocity
Kurennoy, Sergey S.
2006-05-01
The beam coupling impedances of small discontinuities of an accelerator vacuum chamber have been calculated [e.g., Kurennoy, Gluckstern, and Stupakov, Phys. Rev. E 52, 4354 (1995)PLEEE81063-651X10.1103/PhysRevE.52.4354] for ultrarelativistic beams using the Bethe diffraction theory. Here we extend the results to an arbitrary beam velocity. The vacuum chamber is assumed to have an arbitrary, but uniform along the beam path, cross section. The longitudinal and transverse coupling impedances are derived in terms of series over cross-section eigenfunctions, while the discontinuity shape enters via its polarizabilities. Simple explicit formulas for two important particular cases—circular and rectangular chamber cross sections—are presented. The impedance dependence on the beam velocity exhibits some unusual features: for example, the reactive impedance, which dominates in the ultrarelativistic limit, can vanish at a certain beam velocity, or its magnitude can exceed the ultrarelativistic value many times. In addition, we demonstrate that the same technique, the field expansion into a series of cross-section eigenfunctions, is convenient for calculating the space-charge impedance of uniform beam pipes with arbitrary cross section.
Are active elements necessary in the basilar membrane impedance?
Diependaal, R J; Viergever, M A; de Boer, E
1986-07-01
This article is motivated by the current hypothesis [Kim et al., Psychological, Physiological and Behavioural Studies in Hearing (Delft U. P., The Netherlands, 1980); Neely, Doctoral dissertation, Washington University, St. Louis, MO (1981); de Boer, J. Acoust. Soc. Am. 73, 567-573 (1983a) and 73, 574-576 (1983b)] that it is necessary to include active elements in the basilar membrane (BM) impedance in order to explain recent data on the vibration of the BM [Khanna and Leonard, Science 215, 305-306 (1982); Sellick et al., J. Acoust. Soc. Am. 72, 131-141 (1982); Robles et al., Peripheral Auditory Mechanisms (Springer, New York, 1986)]. In order to test this hypothesis, first, a method which is an inversion of the customary description of cochlear mechanics is described. Instead of computing the BM velocity for a given point impedance of the membrane, we show how to compute the impedance function from a given BM velocity pattern in response to a sinusoidal input at the stapes. This method is then used to study the sensitivity of the recovered impedance to perturbations in the velocity pattern. The simulations used show that the real part of the impedance is extremely sensitive to such perturbations. Therefore, measured velocity patterns are unlikely to resolve the issue of whether active elements should be included. Frequency responses measured at a few points on the membrane are even less likely to do so.
Materials analyses and electrochemical impedance of implantable metal electrodes.
Howlader, Matiar M R; Ul Alam, Arif; Sharma, Rahul P; Deen, M Jamal
2015-04-21
Implantable electrodes with high flexibility, high mechanical fixation and low electrochemical impedance are desirable for neuromuscular activation because they provide safe, effective and stable stimulation. In this paper, we report on detailed materials and electrical analyses of three metal implantable electrodes - gold (Au), platinum (Pt) and titanium (Ti) - using X-ray photoelectron spectroscopy (XPS), scanning acoustic microscopy, drop shape analysis and electrochemical impedance spectroscopy. We investigated the cause of changes in electrochemical impedance of long-term immersed Au, Pt and Ti electrodes on liquid crystal polymers (LCPs) in phosphate buffered saline (PBS). We analyzed the surface wettability, surface and interface defects and the elemental depth profile of the electrode-adhesion layers on the LCP. The impedance of the electrodes decreased at lower frequencies, but increased at higher frequencies compared with that of the short-term immersion. The increase of impedances was influenced by the oxidation of the electrode/adhesion-layers that affected the double layer capacitance behavior of the electrode/PBS. The oxidation of the adhesion layer for all the electrodes was confirmed by XPS. Alkali ions (sodium) were adsorbed on the Au and Pt surfaces, but diffused into the Ti electrode and LCPs. The Pt electrode showed a higher sensitivity to surface and interface defects than that of Ti and Au electrodes. These findings may be useful when designing electrodes for long-term implantable devices.
Ring impedance and stored current for the photon factory
International Nuclear Information System (INIS)
The impedance of the Photon Factory ring is computed using estimates for individual vacuum chamber component impedances, and computer results for the impedance of the RF cavities. The total single-bunch loss impedance is expected to be about 2.5 MΩ at a bunch length of 2.0 cm. This is lower than the SPEAR impedance (per unit length of ring circumference) by about a factor of 5. Thus, the threshold current for single bunch instabilities which limit the beam current will probably be on the order of 150 - 200 mA. There should be no problem in reaching a stored current of 500 mA with 312 bunches. RF and beam parameters, such as stored current, klystron power, synchrotron radiation power, higher mode power, cavity power and reflected power are computed as a function of energy for two operating regions: at a constant beam current of 500 mA for lower energies where a klystron power of less than 650 kW is required, and at a constant klystron power of 650 kW at higher energies. Results are given for operation with and without a wiggler, and for both the single-bunch and 312-bunch modes. (author)
Reconstruction of relaxation time distribution from linear electrochemical impedance spectroscopy
Zhang, Yanxiang; Chen, Yu; Yan, Mufu; Chen, Fanglin
2015-06-01
Linear electrochemical impedance spectroscopy (EIS), and in particular its representation of distribution of relaxation time (DRT), enables the identification of the number of processes and their nature involved in electrochemical cells. With the advantage of high frequency resolution, DRT has recently drawn increasing attention for applications in solid oxide fuel cells (SOFCs). However, the method of DRT reconstruction is not yet presented clearly in terms of what mathematical treatments and theoretical assumptions have been made. Here we present unambiguously a method to reconstruct DRT function of impedance based on Tikhonov regularization. By using the synthetic impedances and analytic DRT functions of RQ element, generalized finite length Warburg element, and Gerischer element with physical quantities representative to those of SOFC processes, we show that the quality of DRT reconstruction is sensitive to the sampling points per decade (ppd) of frequency from the impedance measurement. The robustness of the DRT reconstruction to resist noise imbedded in impedance data and numerical calculations can be accomplished by optimizing the weighting factor λ according to well defined criterion.
Study of PEM fuel cell performance by electrochemical impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Asghari, Saeed; Mokmeli, Ali; Samavati, Mahrokh [Isfahan Engineering Research Center, 7th kilometer of Imam Khomeini ave., P.O. Box 81395-619, Isfahan (Iran)
2010-09-15
Electrochemical impedance spectroscopy is a suitable and powerful diagnostic testing method for fuel cells because it is non-destructive and provides useful information about fuel cell performance and its components. This paper presents the diagnostic testing results of a 120 W single cell and a 480 W PEM fuel cell short stack by electrochemical impedance spectroscopy. The effects of clamping torque, non-uniform assembly pressure and operating temperature on the single cell impedance spectrum were studied. Optimal clamping torque of the single cell was determined by inspection of variations of high frequency and mass transport resistances with the clamping torque. The results of the electrochemical impedance analysis show that the non-uniform assembly pressure can deteriorate the fuel cell performance by increasing the ohmic resistance and the mass transport limitation. Break-in procedure of the short stack was monitored and it is indicated that the ohmic resistance as well as the charge transfer resistance decrease to specified values as the break-in process proceeds. The effect of output current on the impedance plots of the short stack was also investigated. (author)
Impedance simulation for LEReC booster cavity transformed from ERL gun cavity
Energy Technology Data Exchange (ETDEWEB)
Liu, Chuyu [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-11-24
Wake impedance induced energy spread is a concern for the low energy cooling electron beam. The impedance simulation of the booster cavity for the LEReC projection is presented in this report. The simulation is done for both non-relativistic and ultra-relativistic cases. The space charge impedance in the first case is discussed. For impedance budget consideration of the electron machine, only simulation of the geometrical impedance in the latter case is necessary since space charge is considered separately.
Active impedance metasurface with full 360° reflection phase tuning
Zhu, Bo O.; Zhao, Junming; Feng, Yijun
2013-01-01
Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit cell of the metasurface is a multiple resonance structure with two resonance poles and one resonance zero, capable of providing 360° reflection phase variation and active tuning within a finite frequency band. Linear reflection phase tuning can also be obtained. Theoretical analysis and simulation are presented and validated by experiment at microwave frequency. The proposed approach can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas. PMID:24162366
Electrical Modeling and Impedance Analysis of Biological Cells
Directory of Open Access Journals (Sweden)
Gowri Sree V.
2014-03-01
Full Text Available It was proved that the external electric field intensity has significant effects on the biological systems. The applied electric field intensity changes the electrical behavior of the cell systems. The impact of electric field intensity on the cell systems should be studied properly to optimize the electric field treatments of biological systems. Based on the cell dimensions and its dielectric properties, an electrical equivalent circuit for an endosperm cell in rice was developed and its total impedance and capacitance were verified with measurement results. The variations of impedance and conductance with respect to applied impulse voltage at different frequencies were plotted. This impedance analysis method can be used to determine the optimum voltage level for electric field treatment and also to determine the cell rupture due to electric field applications.
Road Impedance Model Study under the Control of Intersection Signal
Directory of Open Access Journals (Sweden)
Yunlin Luo
2015-01-01
Full Text Available Road traffic impedance model is a difficult and critical point in urban traffic assignment and route guidance. The paper takes a signalized intersection as the research object. On the basis of traditional traffic wave theory including the implementation of traffic wave model and the analysis of vehicles’ gathering and dissipating, the road traffic impedance model is researched by determining the basic travel time and waiting delay time. Numerical example results have proved that the proposed model in this paper has received better calculation performance compared to existing model, especially in flat hours. The values of mean absolute percentage error (MAPE and mean absolute deviation (MAD are separately reduced by 3.78% and 2.62 s. It shows that the proposed model has feasibility and availability in road traffic impedance under intersection signal.
Space-charge impedance calculations in long-wavelength approximation
Kurennoy, Sergey S.
1999-12-01
Space-charge impedance calculations for smooth vacuum chambers with an arbitrary cross-section and perfectly conducting walls are considered in the long-wavelength approximation, when ωb/(βγc)≪1, where b is a typical transverse size. For the SNS beam energies βγ⩽1.8, and the wavelengths are long when λ≫b. Within the long-wavelength approximation, the fields can be found by solving a 2-D electrostatic problem. Two examples are presented: the space-charge impedance of screening wires (RF-cage) and of a ceramic chamber with inner metal stripes. In addition, we explore the transverse space-charge impedance of a circular pipe with account of betatron oscillations in a wide frequency range.
REDUCING BEAM COUPLING IMPEDANCES IN SNS RING EXTRACTION KICKERS
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. (Sergey); Davino, D. (Daniele); Lee, Y. Y.
2001-01-01
The Spallation Neutron Source (SNS) Accumulator ring extraction system includes 14 modules of windowframe ferrite pulsing kicker magnets with the rise time of about 200 ns. Their contribution to the beam coupling impedances is a serious concern. The kicker impedances, as well as its deflecting magnetic field versus time, are studied using detailed 3-D MAFIA modeling. Various design options, external circuit resistances, and a range of ferrite permeabilities are explored. A kicker module with wide conductor windings around the ferrite behind the kicker current sheet suggests a significant reduction of the kicker transverse and longitudinal coupling impedances. This design provides a good extraction field performance, as demonstrated by electromagnetic simulations. Results of measurements for a small model are also presented.
REDUCING BEAM COUPLING IMPEDANCES IN SNS RING EXTRACTION KICKERS.
Energy Technology Data Exchange (ETDEWEB)
KURENNOY,S.S.; DAVINO,D.; LEE,Y.Y.
2001-06-18
The Spallation Neutron Source (SNS) Accumulator ring extraction kickers [1] consists of 14 modules of windowframe ferrite pulsing magnets with the rise time of about 200 ns. Their contribution to the beam coupling impedances is a serious concern. The kicker impedances, as well as its deflecting magnetic field versus time, are studied using detailed 3-D MAFIA modeling. Various design options, external circuit resistances, and a range of ferrite permeabilities are explored. A kicker module with wide conductor windings around the ferrite behind the kicker current sheet suggests a significant reduction of the kicker transverse and longitudinal coupling impedances. This design provides a good extraction field performance, as demonstrated by electromagnetic simulations. Results of measurements for a small model are also presented.
REDUCING BEAM COUPLING IMPEDANCES IN SNS RING EXTRACTION KICKERS
Energy Technology Data Exchange (ETDEWEB)
S.S. KURENNOY; D. DAVINO; Y. LEE
2001-06-01
The Spallation Neutron Source (SNS) Accumulator ring extraction system [1] includes 14 modules of window-frame ferrite pulsing kicker magnets with the rise time of about 200 ns. Their contribution to the beam coupling impedances is a serious concern. The kicker impedances, as well as its deflecting magnetic field versus time, are studied using detailed 3-D MAFIA modeling. Various design options, external circuit resistances, and a range of ferrite permeabilities are explored. A kicker module with wide conductor windings around the ferrite behind the kicker current sheet suggests a significant reduction of the kicker transverse and longitudinal coupling impedances. This design provides a good extraction field performance, as demonstrated by electromagnetic simulations. Results of measurements for a small model are also presented.
Impedance-stabilized positive corona discharge and its decontamination properties
Energy Technology Data Exchange (ETDEWEB)
Horak, P; Khun, J, E-mail: pavel.horak@vscht.c [Department of Physics and Measurements, Faculty of Chemical Engineering, Institute of Chemical Technology, Technicka 5, 166 28 Praha 6 (Czech Republic)
2010-04-01
The point-to-plane DC corona discharge in air at atmospheric pressure was stabilized by a serially connected ballast impedance. The ballast impedance was implemented by a resistor-capacitor group connected in parallel. In the case of connecting the serial impedance into the electric circuit of a negative corona, the transition into a spark takes place at parameters similar to those of a non-stabilized discharge. In contrast, in the case of a positive corona, the discharge does not undergo a transition into a spark, but rather into a mode of periodic streamers. We measured the bactericidal effect of the stabilized discharge. The experiments showed that after a 2-minute exposure the quantity of surviving bacteria decreased from 95% for a non-stabilized discharge down to 5% for a stabilized one.
Impedance-stabilized positive corona discharge and its decontamination properties
International Nuclear Information System (INIS)
The point-to-plane DC corona discharge in air at atmospheric pressure was stabilized by a serially connected ballast impedance. The ballast impedance was implemented by a resistor-capacitor group connected in parallel. In the case of connecting the serial impedance into the electric circuit of a negative corona, the transition into a spark takes place at parameters similar to those of a non-stabilized discharge. In contrast, in the case of a positive corona, the discharge does not undergo a transition into a spark, but rather into a mode of periodic streamers. We measured the bactericidal effect of the stabilized discharge. The experiments showed that after a 2-minute exposure the quantity of surviving bacteria decreased from 95% for a non-stabilized discharge down to 5% for a stabilized one.
Advanced impedance modeling of solid oxide electrochemical cells
DEFF Research Database (Denmark)
Graves, Christopher R.; Hjelm, Johan
2014-01-01
Impedance spectroscopy is a powerful technique for detailed study of the electrochemical and transport processes that take place in fuel cells and electrolysis cells, including solid oxide cells (SOCs). Meaningful analysis of impedance measurements is nontrivial, however, because a large number of...... modeling parameters are fit to the many processes which often overlap in the same frequency ranges. Also, commonly used equivalent circuit (EC) models only provide zero-dimensional (0-D) approximations of the processes of the two electrodes, electrolyte and gas transport. Employing improved analytical...... electrode and 2-D gas transport models which have fewer unknown parameters for the same number of processes, (ii) use of a new model fitting algorithm, “multi-fitting”, in which multiple impedance spectra are fit simultaneously with parameters linked based on the variation of measurement conditions, (iii...
Beam Impedance Studies of the PS Beam Gas Ionization Monitor
Avgidis, Fotios
2016-01-01
The Beam Gas Ionization monitor (BGI) is a device for continuous beam size monitoring that is intended to be installed in the CERN Proton Synchrotron (PS) during the extended year-end technical stop from December 2016 to April 2017. With the objective of determining the impedance contribution of the BGI vacuum chamber to the overall beam impedance, we report on RF measurements on the device in a laboratory frame, measurement data analysis, and RF simulations of the structure under investigation. For the impedance contribution characterization of the BGI, the following approach has been followed: First, the EM fields inside a simplified BGI model that doesn’t include any of the internal components of the vacuum chamber have been simulated. RF measurements have been performed on the same empty structure showing great agreement between measurement and simulation and thus verifying the validity of the model. Second, simulations have been executed on a fully assembled BGI model that includes all the internal ele...
Acoustic impedance inversion of zero-offset VSP data
Institute of Scientific and Technical Information of China (English)
Wang Jing; Liu Yang; Sun Zhe; Tian Hong; Su Hua; Zhao Qianhua; Liu Yingyu
2009-01-01
Highly precise acoustic impedance inversion is a key technology for pre-drilling prediction by VSP data. In this paper, based on the facts that VSP data has high resolution, high signal to noise ratio, and the downgoing and upgoing waves can be accurately separated, we propose a method of predicting the impedance below the borehole in front of the bit using VSP data. First, the method of nonlinear iterative inversion is adopted to invert for impedance using the VSP corridor stack. Then, by modifying the damping factor in the iteration and using the preconditioned conjugate gradient method to solve the equations, the stability and convergence of the inversion results can be enhanced. The results of theoretical models and actual data demonstrate that the method is effective for pre-drilling prediction using VSP data.
Wave impedance of W-Mo system composite
Institute of Scientific and Technical Information of China (English)
Qiang Shen; Lianmeng Zhang; Hua Tan; Fuqian Jing
2003-01-01
W-Mo composites with different mass fractions of W and Mo were prepared at 1473 K by Spark Plasma Sintering technique. The transverse and longitudinal wave velocities of the samples were accurately measured using the ultrasonic pulse echo overlap method, and the wave impedance values of the samples were then calculated. The results show that W-Mo system composites are of nearly full dense and can be regarded as a mechanical mixture system. The ideal mixture model was adopted to estimate the wave impedance of W-Mo composites. Comparisons with the experimental data demonstrate that the suggested model is sufficiently accurate to predict the wave impedance of W-Mo composites.
Fiber Materials AC Impedance Characteristics and Principium Analysis
Wang, Jianjun; Li, Xiaofeng
With an invariable amplitude and variable frequency inspiriting, impedance of fiber materials rapidly decrease at first and then increase speedy followed with increasing of signal frequency. For the impedance curve of frequency is section of bathtub, this phenomenon is defined as alternating current electric conductive bathtub effect of fiber material. With analysis tools,of circuit theory and medium polarization theory, the phenomenon can be deeply detected that in AC electric field there are four different kind of currents in fiber material: absorbing current, conductance current, charging current and superficial current. With more analyzing it's discovered this phenomenon can be explained by medium polarize theory. Make using of fiber AC electric conductivity bathtub effect, fast testing equipment on fiber moisture regain can be invent, and disadvantages of conventional impedance technique, such as greatness test error and electrode polarization easily. This paper affords directions to design novel speediness fiber moisture test equipments in theory.
Nuclear EMP: stripline test method for measuring transfer impedance
International Nuclear Information System (INIS)
A method for measuring the transfer impedance of flat metal joints for frequencies to 100 MHz has been developed which makes use of striplines. The stripline method, which has similarities to the quadraxial method used for cylindrical components, is described and sets of test results are given. The transfer impedance of a simple joint is modeled as a spurious hyperbolic curve, and a close curve fit to transfer impedance test data from various samples is demonstrated for both the stripline and the quadraxial methods. Validity checks of the test data are discussed using the curve model and other criteria. The method was developed for testing riveted joints which form the avionics bays on B-1s. The joints must provide shielding from EMP currents
Impedance planimetric description of normal rectoanal motility in humans
DEFF Research Database (Denmark)
Andersen, Inge S; Michelsen, Hanne B; Krogh, Klaus;
2007-01-01
PURPOSE: Manometry and pressure-volume measurements are commonly used to study anorectal physiology. However, the methods are limited by several sources of error. Recently, a new impedance planimetric system has been introduced in a porcine model. It allows simultaneous determination of anorectal...... pressures and multiple rectal luminal cross-sectional areas. This study was designed to study normal human rectoanal motility by means of impedance planimetry with multiple rectal cross-sectional areas and rectal and anal pressure. METHODS: Twelve healthy volunteers (10 females), aged 24 to 53 years, were...... the experiment, the cross-sectional area at all channels showed strong cyclic contractile activity and the anal pressure increased by approximately 100 percent. CONCLUSIONS: The new rectal impedance planimetry system allows highly detailed description of rectoanal motility patterns. It has promise as a new...
Broadband excitation for short-time impedance spectroscopy
International Nuclear Information System (INIS)
Frequency domain impedance measurements are still the common approach in assessing passive electrical properties of cells and tissues. However, due to the time requirements for sweeping over a frequency range for performing spectroscopy, they are not suited for recovering fast impedance changes of biological objects. The use of broad bandwidth excitation and monitoring the response as a function of time will greatly reduce the measurement time. The widespread usage of a square wave excitation is simple but not always the best choice. Here we consider different waveforms for excitation and discuss not only the advantages but also their limitations. Measurements in a miniaturized chamber where frequency and time domain measurements are compared show the suitability of different waveforms as excitation signals for the measurements of bio-impedance. The chirp excitation has been found to be most promising in terms of frequency range, signal-to-noise ratio and crest factor
A Wireless Multi-Sensor Dielectric Impedance Spectroscopy Platform
Directory of Open Access Journals (Sweden)
Seyed Alireza Ghaffari
2015-09-01
Full Text Available This paper describes the development of a low-cost, miniaturized, multiplexed, and connected platform for dielectric impedance spectroscopy (DIS, designed for in situ measurements and adapted to wireless network architectures. The platform has been tested and used as a DIS sensor node on ZigBee mesh and was able to interface up to three DIS sensors at the same time and relay the information through the network for data analysis and storage. The system is built from low-cost commercial microelectronics components, performs dielectric spectroscopy ranging from 5 kHz to 100 kHz, and benefits from an on-the-fly calibration system that makes sensor calibration easy. The paper describes the microelectronics design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the testing of the platform for in situ dielectric impedance spectroscopy applications pertaining to fertilizer sensing, water quality sensing, and touch sensing.
Gas breakdown and plasma impedance in split-ring resonators
Hoskinson, Alan R.; Parsons, Stephen; Hopwood, Jeffrey
2016-02-01
The appearance of resonant structures in metamaterials coupled to plasmas motivates the systematic investigation of gas breakdown and plasma impedance in split-ring resonators over a frequency range of 0.5-9 GHz. In co-planar electrode gaps of 100 μm, the breakdown voltage amplitude decreases from 280 V to 225 V over this frequency range in atmospheric argon. At the highest frequency, a microplasma can be sustained using only 2 mW of power. At 20 mW, we measure a central electron density of 2 × 1020 m-3. The plasma-electrode overlap plays a key role in the microplasma impedance and causes the sheath impedance to dominate the plasma resistance at very low power levels. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.
Experimental verification of depolarization effects in bioelectrical impedance measurement.
Chen, Xiaoyan; Lv, Xinqiang; Du, Meng
2014-01-01
The electrode polarization effects on bioelectrical impedance measurement at low-frequency cannot be ignored. In this paper, the bioelectrical data of mice livers are measured to specify the polarization effects on the bio-impedance measurement data. We firstly introduce the measurement system and methodology. Using the depolarization method, the corrected results are obtained. Besides, the specific effects of electrode polarization on bio-impedance measurement results are investigated using comparative analysis of the previous and posterior correction results from dielectric spectroscopy, Cole-Cole plot, conductivity and spectroscopy of dissipation tangent. Experimental results show that electrode polarization has a significant influence on the characteristic parameters of mouse liver tissues. To be specific, we see a low-frequency limit resistance R0 increase by 19.29%, a reactance peak XP increase by 8.50%, a low-frequency limit conductivity Kl decrease by 17.65% and a dissipation peak tangent decrease by 160%.
Impedance characteristics of nanoparticle-LiCoO2+PVDF
Panjaitan, Elman; Kartini, Evvy; Honggowiranto, Wagiyo
2016-02-01
The impendance of np-LiCoO2+xPVDF, as a cathode material candidate for lithium-ion battery (LIB), has been characterized using impedance spectroscopy for x = 0, 5, 10, 15 and 20 volume percentage (%v/v) and for frequencies in the 42 Hz to 5 MHz range. Both real and imaginary components of the impedance were found to be frequency dependent, and both tend to increase for increasing PVDF (polyvinyilidene fluoride) concentration, except that for 10% PVDF both real and imaginary components of impedance are smaller than for 5%. The mechanism for relaxation time for each addition of PVDF was analyzed using Cole-Cole plots. The analysis showed that the relaxation times of the nanostructured LiCoO2 with PVDF additive is relatively constant. Further, PVDF addition increases the bulk resistance and decreases the bulk capacitance of the nanostructured LiCoO2.
Using FOCUS to determine the radiation impedance for square transducers
Jennings, Matthew R.; McGough, Robert J.
2012-10-01
The power radiated by an ultrasound transducer is calculated with the radiation resistance, which is the real part of the radiation impedance. For circular transducers, an analytical solution for the radiation impedance is known, but an analytical expression for the radiation impedance is not available for rectangular or square transducers. To determine the radiation resistance in FOCUS, the pressure on the surface of a square transducer is computed with the fast nearfield method, and then the force on the transducer face is computed by integrating the pressure. Results using this approach are numerically evaluated for a range of ka values from 0.1 to 16. The pressure on the transducer face is also computed with the Rayleigh-Sommerfeld integral, and the results are compared. The numerical value of the radiation resistance computed with FOCUS and with the Rayleigh-Sommerfeld integral converge to the same value, although FOCUS calculates the same result in about one-quarter of the time.
Microgrid Reactive and Harmonic Power Sharing Using Enhanced Virtual Impedance
DEFF Research Database (Denmark)
He, Jinwei; Wei Li, Yun; Guerrero, Josep M.;
2013-01-01
only a line current feed-forward term is added to the DG voltage reference, the proposed virtual impedances at fundamental and harmonic frequencies are realized using DG line current and point of common coupling (PCC) voltage feed-forward terms, respectively. With this modification, the mismatched DG...... feeder impedances can be properly compensated, resulting in accurate reactive and harmonic power sharing at the same time. In addition, this paper shows that the microgrid PCC harmonic voltages can be mitigated by reducing the magnitude of DG unit equivalent harmonic impedance. Finally, an improved...... proportional plus resonant voltage controller is developed to ensure accurate power sharing and PCC harmonic voltage compensation without using any fundamental/harmonic component detections....
Correcting electrode impedance effects in broadband SIP measurements
Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Vereecken, Harry
2016-04-01
Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.
Design of optimized impedance transformer for ICRF antenna in LHD
International Nuclear Information System (INIS)
Highlights: ► We developed optimization method of impedance transformer for ICRF antenna. ► Power loss will be one-third with the optimized impedance transformer. ► Possibility of damage on the transmission line will be drastically reduced. ► High performance will be kept in the wide antenna impedance region. -- Abstract: A pair of ion cyclotron range of frequencies (ICRF) antennas in the large helical device (LHD), HAS antennas showed high efficiency in minority ion heating. However the low loading resistance must be increased to prevent breakdown in transmission line. Moreover, the voltage and the current around the feed-through must be reduced to protect it. For these purpose, we developed a design procedure of the impedance transformer for HAS antennas. To optimize the transformer, the inner conductors were divided into several segments and the radii of them were given discretely and independently. The maximum effective loading resistance was obtained by using all combinations of radii within the limitations of the voltage and current at the feed-through and the electric field on the transformer. To get a precise solution, this procedure was repeated several times by narrowing the range of radii of inner conductors. Then the optimized impedance transformer was designed by smoothing the radii of inner conductors. For the typical discharge, the voltage and current at the feed-through were reduced to the half of the original values with the same power. The effective loading resistance was increased to more than four times. High performance is expected in wide impedance region
Fuzzy modeling of electrical impedance tomography images of the lungs
Directory of Open Access Journals (Sweden)
Harki Tanaka
2008-01-01
Full Text Available OBJECTIVES: Aiming to improve the anatomical resolution of electrical impedance tomography images, we developed a fuzzy model based on electrical impedance tomography's high temporal resolution and on the functional pulmonary signals of perfusion and ventilation. INTRODUCTION: Electrical impedance tomography images carry information about both ventilation and perfusion. However, these images are difficult to interpret because of insufficient anatomical resolution, such that it becomes almost impossible to distinguish the heart from the lungs. METHODS: Electrical impedance tomography data from an experimental animal model were collected during normal ventilation and apnea while an injection of hypertonic saline was administered. The fuzzy model was elaborated in three parts: a modeling of the heart, the pulmonary ventilation map and the pulmonary perfusion map. Image segmentation was performed using a threshold method, and a ventilation/perfusion map was generated. RESULTS: Electrical impedance tomography images treated by the fuzzy model were compared with the hypertonic saline injection method and computed tomography scan images, presenting good results. The average accuracy index was 0.80 when comparing the fuzzy modeled lung maps and the computed tomography scan lung mask. The average ROC curve area comparing a saline injection image and a fuzzy modeled pulmonary perfusion image was 0.77. DISCUSSION: The innovative aspects of our work are the use of temporal information for the delineation of the heart structure and the use of two pulmonary functions for lung structure delineation. However, robustness of the method should be tested for the imaging of abnormal lung conditions. CONCLUSIONS: These results showed the adequacy of the fuzzy approach in treating the anatomical resolution uncertainties in electrical impedance tomography images.
Fuzzy modeling of electrical impedance tomography images of the lungs
Energy Technology Data Exchange (ETDEWEB)
Tanaka, Harki; Ortega, Neli Regina Siqueira; Galizia, Mauricio Stanzione [Universidade de Sao Paulo (USP), SP (Brazil). Faculdade de Medicina. Medical Informatics; Borges, Joao Batista; Amato, Marcelo Britto Passos [Universidade de Sao Paulo (USP), SP (Brazil). Faculdade de Medicina. Dept. of Experimental Pneumology]. E-mail: harki_t@yahoo.com
2008-07-01
Objectives: Aiming to improve the anatomical resolution of electrical impedance tomography images, we developed a fuzzy model based on electrical impedance tomography's high temporal resolution and on the functional pulmonary signals of perfusion and ventilation. Introduction: Electrical impedance tomography images carry information about both ventilation and perfusion. However, these images are difficult to interpret because of insufficient anatomical resolution, such that it becomes almost impossible to distinguish the heart from the lungs. Methods: Electrical impedance tomography data from an experimental animal model were collected during normal ventilation and apnoea while an injection of hypertonic saline was administered. The fuzzy model was elaborated in three parts: a modeling of the heart, the pulmonary ventilation map and the pulmonary perfusion map. Image segmentation was performed using a threshold method, and a ventilation/perfusion map was generated. Results: Electrical impedance tomography images treated by the fuzzy model were compared with the hypertonic saline injection method and computed tomography scan images, presenting good results. The average accuracy index was 0.80 when comparing the fuzzy modeled lung maps and the computed tomography scan lung mask. The average ROC curve area comparing a saline injection image and a fuzzy modeled pulmonary perfusion image was 0.77. Discussion: The innovative aspects of our work are the use of temporal information for the delineation of the heart structure and the use of two pulmonary functions for lung structure delineation. However, robustness of the method should be tested for the imaging of abnormal lung conditions. Conclusions: These results showed the adequacy of the fuzzy approach in treating the anatomical resolution uncertainties in electrical impedance tomography images. (author)
Impedance reduction mechanisms in a magnetically immersed electron diode
International Nuclear Information System (INIS)
The successful operation of a magnetically-immersed electron diode using inductive-voltage-adder (IVA) technology for radiography requires a stable impedance for > 30 ns. In an IVA, the voltages from many acceleration gaps are added in series along a magnetically-insulated transmission line. The final voltage is applied to a thin needle that is immersed in a 10--50 Tesla solenoidal magnetic field. An electron beam is produced in a small spot at the anode target (10 MV). The electron current flowing off the needle is determined by the space-charge limited flow in a long pipe. Ion-emitting plasmas are produced from direct beam heating of the target and from radiation emitted from the several eV target surface that heats the outer walls of the anode (1--4.5-cm radius). Plasma ions are attracted to the electron beam and provide a degree of charge neutralization. The presence of these neutralizing ions reduces the diode impedance (nominally 300 Ohms), enhancing the electron current. The author is studying the impedance reduction mechanisms with the hybrid simulation code IPROP. He finds ions emitted from the anode walls lead to a reduced but stable impedance consistent with bipolar flow. If the ions are permitted to strip in ion-ion collisions, however, a runaway loss of impedance occurs that provides diode current well above the bipolar limit. Assuming nitrogen ion emission, he has qualitatively reproduced impedance behavior observed in experiments on the Hermes III IVA accelerator at Sandia National Laboratories. Several mitigation schemes are being investigated
Experiences with a two terminal-pair digital impedance bridge
Callegaro, Luca; Kampik, Marian; Kim, Dan Bee; Ortolano, Massimo; Pourdanesh, Faranak
2014-01-01
This paper describes the realization of a two terminal-pair digital impedance bridge and the test measurements performed with it. The bridge, with a very simple architecture, is based on a commercial two-channel digital signal synthesizer and a synchronous detector. The bridge can perform comparisons between impedances having arbitrary phase and magnitude ratio: its balance is achieved automatically in less than a minute. $R$-$C$ comparisons with calibrated standards, at kHz frequency and 100 kohm magnitude level, give ratio errors of the order of $10^{-6}$, with potential for further improvements.
Coupling impedances of small discontinuities: A general approach
Kurennoy, Sergey S.; Gluckstern, Robert L.; Stupakov, Gennady V.
1995-10-01
A general theory of the beam interaction with small discontinuities of the vacuum chamber of an accelerator is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in an easy and natural way, the analytical results for the frequencies and coupling impedances of the trapped modes due to small discontinuities on the vacuum chamber of a general cross section. Formulas for two important particular cases-a circular and a rectangular chamber-are presented.
Beam coupling impedances of obstacles protruding into beam pipe
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.S.
1997-08-01
The beam coupling impedances of small obstacles protruding inside the vacuum chamber of an accelerator are calculated analytically at frequencies for which the wavelength is large compared to a typical size of the obstacle. Simple formulas for a few important particular cases, including both essentially three-dimensional objects like a post or a mask and axisymmetric irises, are presented. The analytical results are compared and agree with three-dimensional computer simulations. These results allow simple practical estimates of the broad-band impedance contributions from such discontinuities.
Coupling impedances of small discontinuities: A general approach
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.S.; Gluckstern, R.L. [Physics Department, University of Maryland, College Park, Maryland 20742 (United States); Stupakov, G.V. [Stanford Linear Accelerator Center, Stanford, California 94309 (United States)
1995-10-01
A general theory of the beam interaction with small discontinuities of the vacuum chamber of an accelerator is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in an easy and natural way, the analytical results for the frequencies and coupling impedances of the trapped modes due to small discontinuities on the vacuum chamber of a general cross section. Formulas for two important particular cases---a circular and a rectangular chamber---are presented.
Beam Coupling Impedances of Obstacles Protruding into Beam Pipe.
Kurennoy, Sergey S.
1997-05-01
The beam coupling impedances of small obstacles protruding inside the vacuum chamber of an accelerator are calculated analytically at frequencies for which the wavelength is large compared to a typical size of the obstacle. Simple formulas for a few important particular cases including both essentially three-dimensional objects like a post or a mask and axisymmetric irises, are presented. The analytical results are compared and agree with three-dimensional computer simulations. These results allow simple practical estimates of the broad-band impedance contributions from such discontinuities.
A Retrofit Technique for Kicker Beam-Coupling Impedance Reduction
Caspers, Friedhelm; Kroyer, T; Timmins, M; Uythoven, J; Kurennoy, S
2004-01-01
The reduction of the impedance of operational ferrite kicker structures may be desirable in order to avoid rebuilding such a device. Often resistively coated ceramic plates or tubes are installed for this purpose but at the expense of available aperture. Ceramic U-shaped profiles with a resistive coating fitting between the ellipse of the beam and the rectangular kicker aperture have been used to significantly reduce the impedance of the magnet, while having a limited effect on the available physical aperture. Details of this method, constraints, measurements and simulation results as well as practical aspects are presented and discussed.
The beam coupling impedance model of CERN Proton Synchrotron
Persichelli, Serena; Migliorati, Mauro; Salvant, Benoit
The research activity described in this thesis work is dedicated to developing a longitudinal and a transverse beam coupling impedance model for the CERN Proton Synchrotron (PS), in the framework of the Large Hadron Collider (LHC) Injector Upgrade (LIU) project. The study allows a better understanding of the instability threshold of the machine, helping predicting the effects of the current increase planned for the upgrade program. Furthermore, the knowledge of the machine beam coupling impedance model allows improving the stability of beams injected into the LHC chain, in prevision for the particle collision energy increase in program for LHC physics experiments.
The frequency characteristics of medium voltage distribution system impedances
Directory of Open Access Journals (Sweden)
Liviu Emil Petrean
2009-10-01
Full Text Available In this paper we present the frequency characteristics of impedances involved in the electrical equivalent circuit of a large medium voltage distribution system. These impedances influence harmonics distortions propagation occurring due to the nonsinusoidal loads. We analyse the case of a 10 kV large urban distribution system which supplies industrial, commercial and residential customers. The influence of various parameters of the distribution network on the frequency characteristics are presented, in order to assess the interaction of harmonic distortion and distribution system network.
Impedance technique for measuring dielectrophoretic collection of microbiological particles
Allsopp, D W E; Brown, A P; Betts, W B
1999-01-01
Measurement of the impedance change resulting from the collection of microbiological particles at coplanar electrodes is shown to be an effective and potentially quantitative method of detecting dielectrophoresis. Strong correlations between the frequency-dependent dielectrophoretic collection characteristics measured by impedance change and those observed using an established counting method based on image analysis have been obtained for Escherichia coli. In addition it is shown that the new electrical method can be used to sense dielectrophoretic collection of 19 nm diameter latex beads, particles too small to be resolved by conventional optical detection systems. (author)
Theory of fractional order elements based impedance matching networks
Radwan, Ahmed
2011-03-01
Fractional order circuit elements (inductors and capacitors) based impedance matching networks are introduced for the first time. In comparison to the conventional integer based L-type matching networks, fractional matching networks are much simpler and versatile. Any complex load can be matched utilizing a single series fractional element, which generally requires two elements for matching in the conventional approach. It is shown that all the Smith chart circles (resistance and reactance) are actually pairs of completely identical circles. They appear to be single for the conventional integer order case, where the identical circles completely overlap each other. The concept is supported by design equations and impedance matching examples. © 2010 IEEE.
Two port network analysis for three impedance based oscillators
Said, Lobna A.
2011-12-01
Two-port network representations are applied to analyze complex networks which can be dissolved into sub-networks connected in series, parallel or cascade. In this paper, the concept of two-port network has been studied for oscillators. Three impedance oscillator based on two port concept has been analyzed using different impedance structures. The effect of each structure on the oscillation condition and the frequency of oscillation have been introduced. Two different implementations using MOS and BJT have been introduced. © 2011 IEEE.
Measurement of solar cell parameters using impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Suresh, M.S. [Battery Division, ISRO Satellite Centre, Bangalore (India)
1996-08-15
Measurement of solar cell parameters is important for the design of satellite power systems. These parameters can be measured using impedance spectroscopy and an equivalent circuit model developed. In this study parameters of a Back Surface Reflector Field solar cell (BSFR) have been measured using impedance spectroscopy. The results show high diffusion capacitance of BSFR cells and their exponential relation to the operating voltage. Cell dynamic resistance, diode factor, transition capacitance, and series resistance could also be measured. The minority carrier life time also has been calculated
A transient model to simulate HTPEM fuel cell impedance spectra
DEFF Research Database (Denmark)
Vang, Jakob Rabjerg; Andreasen, Søren Juhl; Kær, Søren Knudsen
2012-01-01
This paper presents a spatially resolved transient fuel cell model applied to the simulation of high temperature PEM fuel cell impedance spectra. The model is developed using a 2D finite volume method approach. The model is resolved along the channel and across the membrane. The model considers...... diffusion of cathode gas species in gas diffusion layers and catalyst layer, transport of protons in the membrane and the catalyst layers, and double layer capacitive effects in the catalyst layers. The model has been fitted simultaneously to a polarization curve and to an impedance spectrum recorded...... this, phenomena neglected in this version of the model must be incorporated in future versions....
A Case of Aerophagia Diagnosed by Multichannel Intraluminal Impedance Monitoring.
Sohn, Ki Chang; Jeong, Young Hoon; Jo, Dong Ho; Heo, Won Gak; Yeom, Dong Han; Choi, Suck Chei; Ryu, Han Seung
2015-11-01
Aerophagia is a disorder caused by abnormal accumulation of air in the gastrointestinal tract as a result of repetitive and frequent inflow of air through the mouth. For the diagnosis of this condition, it is difficult to objectively measure the air swallowing. However, multichannel intraluminal impedance monitoring facilitates the differential diagnosis between normal air swallowing and pathologic aerophagia, and can aid in the determination of the frequency and amount of air swallowed. In this report, in addition to a literature review, we describe a case of 36-year-old man with abdominal distension who was diagnosed with aerophagia using esophageal impedance monitoring and was treated with clonazepam. PMID:26586352
Construction of Tunnel Diode Oscillator for AC Impedance Measurement
Shin, J. H.; Kim, E.
2014-03-01
We construct a tunnel diode oscillator (TDO) to study electromagnetic response of a superconducting thin film. Highly sensitive tunnel diode oscillators allow us to detect extremely small changes in electromagnetic properties such as dielectric constant, ac magnetic susceptibility and magnetoresistance. A tunnel diode oscillator is a self-resonant oscillator of which resonance frequency is primarily determined by capacitance and inductance of a resonator. Amplitude of the signal depends on the quality factor of the resonator. The change in the impedance of the sample electromagnetic coupled to one of inductors in the resonator alters impedance of the inductor, and leads to the shift in the resonance frequency and the change of the amplitude.
Electrical impedance along connective tissue planes associated with acupuncture meridians
Directory of Open Access Journals (Sweden)
Hammerschlag Richard
2005-05-01
Full Text Available Abstract Background Acupuncture points and meridians are commonly believed to possess unique electrical properties. The experimental support for this claim is limited given the technical and methodological shortcomings of prior studies. Recent studies indicate a correspondence between acupuncture meridians and connective tissue planes. We hypothesized that segments of acupuncture meridians that are associated with loose connective tissue planes (between muscles or between muscle and bone visible by ultrasound have greater electrical conductance (less electrical impedance than non-meridian, parallel control segments. Methods We used a four-electrode method to measure the electrical impedance along segments of the Pericardium and Spleen meridians and corresponding parallel control segments in 23 human subjects. Meridian segments were determined by palpation and proportional measurements. Connective tissue planes underlying those segments were imaged with an ultrasound scanner. Along each meridian segment, four gold-plated needles were inserted along a straight line and used as electrodes. A parallel series of four control needles were placed 0.8 cm medial to the meridian needles. For each set of four needles, a 3.3 kHz alternating (AC constant amplitude current was introduced at three different amplitudes (20, 40, and 80 μAmps to the outer two needles, while the voltage was measured between the inner two needles. Tissue impedance between the two inner needles was calculated based on Ohm's law (ratio of voltage to current intensity. Results At the Pericardium location, mean tissue impedance was significantly lower at meridian segments (70.4 ± 5.7 Ω compared with control segments (75.0 ± 5.9 Ω (p = 0.0003. At the Spleen location, mean impedance for meridian (67.8 ± 6.8 Ω and control segments (68.5 ± 7.5 Ω were not significantly different (p = 0.70. Conclusion Tissue impedance was on average lower along the Pericardium meridian, but not
Ground Loop Impedance of Long EHV Cable Lines
DEFF Research Database (Denmark)
Ohno, Teruo; Bak, Claus Leth; Sørensen, Thomas K.
2012-01-01
The distance protection scheme without communication is often applied to the backup protection of EHV cable lines. For a reliable operation of a ground distance relay, the ground loop impedance of EHV cable lines needs to have a linear relationship to the distance from the relay location...... in literature. Through the calculation of the ground loop impedance for cable lines, it has been found that, for long EHV cable lines, the reliable operation of the ground distance relay is possible with a typical relay setting. Effects of parameters, such as substation grounding, cable layouts...
Amplifier input impedance in dry electrode ECG recording.
Assambo, Cedric; Burke, Martin J
2009-01-01
This paper presents a novel approach for designing the front-end of instrumentation amplifiers for use in dry electrode recording of the human electrocardiogram (ECG). The method relies on information provided by the characterization of the skin-electrode interface and the analysis of low frequency ECG criteria defined by international standards. Marginal measurements of capacitive elements of the skin-electrode interface as small as 0.01 microF, suggest values of input impedance in the order of 1.3 GOmega. However, results in 99% of the data analyzed indicate that a recording amplifier providing an input impedance of 500 MOmega should ensure clear signal sensing without distortion.
Electrochemical Impedance Modeling of a Solid Oxide Fuel Cell Anode
DEFF Research Database (Denmark)
Mohammadi, R.; Søgaard, Martin; Ramos, Tania;
2014-01-01
A simulation package for the impedance response of SOFC anodes is presented here. The model couples the gas transport in gas channels and within a porous electrode with the electrochemical kinetics. The gas phase mass transport is modeled using mass conservation equations. A transmission line model...... (TLM), which is suitably modified to account for the electrode microstructural details, is used for modeling the impedance arising from the electrochemical reactions. In order to solve the system of nonlinear equations, an in-house code based on the finite difference method was developed. Some...
Impedance Spectra of Activating/Passivating Solid Oxide Electrodes
DEFF Research Database (Denmark)
Mogensen, Mogens Bjerg; Sun, Xiufu; Koch, Søren;
2014-01-01
The aim of this paper is to show that the inductive arcs seen in electrochemical impedance spectra of solid oxide cells (SOCs) are real electrochemical features that in several cases can be qualitatively explained by passivation/activation processes. Several degradation processes of Solid Oxide...... Fuel Cells (SOFC) and Electrolyser Cells (SOEC) exist. Not all of them are irreversible, especially not over short periods. A reversible degradation is termed “passivation” and the reverse is then “activation”. These processes may exhibit themselves in the Electrochemical Impedance Spectra (EIS...
Local resolved electrochemical impedance spectroscopy of PEFC single cells
Energy Technology Data Exchange (ETDEWEB)
Schulze, M.; Gulzow, E. [German Aerospace Center, Inst. of Technical Thermodynamics, Stuttgart (Germany)
2009-07-01
Experimental data on a spatial resolved level is needed to understand the integral behaviour of fuel cells as well as to validate models describing fuel cell behaviour. This paper described a new tool developed to increase the accuracy of current density measurements. Based on a printed circuit board, the tool integrated local electrochemical impedance spectroscopy techniques in order to determine local membrane resistance, electrochemical reactions, and transport processes. Solutions for locally resolved impedance spectroscopy measurements were presented. It was concluded that the tool will help to provide a more detailed understanding of fuel cell behaviour.
Impedance and instability threshold estimates in the main injector I
International Nuclear Information System (INIS)
One of the important considerations in the design of the Main Injector is the beam coupling impedances in the vacuum chamber and the stability of the beam. Along with the higher intensities comes the possibility of instabilities which lead to growth in beam emittances and/or the loss of beam. This paper makes estimations of the various impedances and instability thresholds based on impedance estimations and measurements. Notably missing from this paper is any analysis of transition crossing and its potential limitations on beam intensity and beam emittance. Future work should consider this issue. The body of the work contains detailed analysis of the various impedance estimations and instability threshold calculations. The calculations are based on the Main Injector beam intensity of 6 x 1010 protons per bunch, 95% normalized transverse emittances of 20π mm-mrad, and 95% normalized longitudinal emittance of 0.1 eV-s at 8.9 GeV injection energy and 0.25 eV-s at 150 GeV flattop energy. The conclusions section summarizes the results in the paper and is meant to be readable by itself without referring to the rest of the paper. Also in the conclusion section are recommendations for future investigations
Development of a current monitor using a negative impedance circuit
International Nuclear Information System (INIS)
We developed a beam current transformer which appropriates for monitoring beam of an accelerator having operating period of a few seconds. The beam monitor is a new type CT which can measure DC component of beam using a negative impedance circuit. In this report, we describe stability of a time constant, temperature and frequency characteristic of the CT. (author)
Improved techniques of impedance calculation and localization in particle accelerators
Biancacci, Nicolò; Migliorati, Mauro; Métral, Elias; Salvant, Benoit
In this thesis we mainly focus on particle accelerators applied to high energy physics research where a fundamental parameter, the luminosity, is maximized in order to increase the rate of particle collisions useful to particle physicists. One way to increase this parameter is to increase the intensity of the circulating beams which is limited by the onset of collective effects that may drive the beam unstable and eventually provoke beam losses or reduce the beam quality required by the particle physics experiments. One major cause of collective effects is the beam coupling impedance, a quantity that quantifies the effect of the fields scattered by a beam passing through any accelerator device. The development of an impedance budget is required in those machines that are planning substantial upgrades as shown in this thesis for the CERN PS case. The main source of impedance in the CERN LHC are the collimators. Within an impedance reduction perspective, in order to reach the goals of the planned upgrades, it ...
Contactless Impedance Sensors and Their Application to Flow Measurements
Directory of Open Access Journals (Sweden)
Karel Štulík
2013-02-01
Full Text Available The paper provides a critical discussion of the present state of the theory of high-frequency impedance sensors (now mostly called contactless impedance or conductivity sensors, the principal approaches employed in designing impedance flow-through cells and their operational parameters. In addition to characterization of traditional types of impedance sensors, the article is concerned with the use of less common sensors, such as cells with wire electrodes or planar cells. There is a detailed discussion of the effect of the individual operational parameters (width and shape of the electrodes, detection gap, frequency and amplitude of the input signal on the response of the detector. The most important problems to be resolved in coupling these devices with flow-through measurements in the liquid phase are also discussed. Examples are given of cell designs for continuous flow and flow-injection analyses and of detection systems for miniaturized liquid chromatography and capillary electrophoresis. New directions for the use of these sensors in molecular biology and chemical reactors and some directions for future development are outlined.
Impedance characterization of PV modules in outdoor conditions
DEFF Research Database (Denmark)
Oprea, Matei-lon; Thorsteinsson, Sune; Spataru, Sergiu;
2016-01-01
Impedance spectroscopy (IS) has been used for laboratory characterizations of photovoltaic (PV) technologies under well controlled conditions. This work applies IS for outdoor characterization of PV panels, in order to observe the effect of irradiance (G) and temperature (T) on the PV module...
Identification of Critical Transmission Limits in Injection Impedance Plane
DEFF Research Database (Denmark)
Jóhannsson, Hjörtur; Østergaard, Jacob; Nielsen, Arne Hejde
2012-01-01
for the critical and characteristic lines in the impedance plane form the basis for a new phasormeasurement based situational awareness method, which uses the results in this paper to identify critical operational boundariesin real time and to visualize the system operating conditions in an informative way...
EU Regulations Impede Market Introduction of GM Forest Trees.
Custers, René; Bartsch, Detlef; Fladung, Matthias; Nilsson, Ove; Pilate, Gilles; Sweet, Jeremy; Boerjan, Wout
2016-04-01
Biotechnology can greatly improve the efficiency of forest tree breeding for the production of biomass, energy, and materials. However, EU regulations impede the market introduction of genetically modified (GM) trees so their socioeconomic and environmental benefits are not realized. European policy makers should concentrate on a science-based regulatory process. PMID:26897457
Impedance and instability threshold estimates in the main injector I
Energy Technology Data Exchange (ETDEWEB)
Martens, M.A.; Ng, K.Y.
1994-03-01
One of the important considerations in the design of the Main Injector is the beam coupling impedances in the vacuum chamber and the stability of the beam. Along with the higher intensities comes the possibility of instabilities which lead to growth in beam emittances and/or the loss of beam. This paper makes estimations of the various impedances and instability thresholds based on impedance estimations and measurements. Notably missing from this paper is any analysis of transition crossing and its potential limitations on beam intensity and beam emittance. Future work should consider this issue. The body of the work contains detailed analysis of the various impedance estimations and instability threshold calculations. The calculations are based on the Main Injector beam intensity of 6 x 10{sup 10} protons per bunch, 95% normalized transverse emittances of 20{pi} mm-mrad, and 95% normalized longitudinal emittance of 0.1 eV-s at 8.9 GeV injection energy and 0.25 eV-s at 150 GeV flattop energy. The conclusions section summarizes the results in the paper and is meant to be readable by itself without referring to the rest of the paper. Also in the conclusion section are recommendations for future investigations.
Diffusion and conversion impedance in solid oxide fuel cells
DEFF Research Database (Denmark)
Jacobsen, Torben; Hendriksen, Peter Vang; Koch, Søren
2008-01-01
of these processes. The first is a CSTR model based on a well convected gas supply volume equipped with gas inlet and outlet. Since the current distribution on the electrode surface is uniform, the impedance is derived for perturbation from a steady state and contributions from kinetics are directly additive...
Calculation of longitudinal CSR impedance in curved chamber
International Nuclear Information System (INIS)
Coherent synchrotron radiation (CSR) fields are generated when a bunched beam moves along a curved trajectory. A new code, named CSRZ, was developed using finite difference method to calculate the longitudinal CSR impedance for a beam moving along a curved chamber. The method adopted in our code was originated by T. Agoh and K. Yokoya [1]. It solves the parabolic equation in the frequency domain in a curvilinear coordinate system. In our studies, the chamber has uniform rectangular crosssection along the beam trajectory, which is the same as that in [1]. But the curvature of the beam trajectory is freed, and then we can investigate the CSR impedance of a single or a series of bending magnets. The calculation results indicate that the shielding effect due to outer chamber wall can be well explained by a simple optical approximation model at high frequencies. With an approximation of a wiggling chamber inside a wiggler, the coherent wiggler radiation (CWR) impedance has also been studied. Due to chamber shielding, the CWR impedance exhibits narrow peaks at frequencies satisfying the resonant conditions. (author)
Effect of rib-cage structure on acoustic chest impedance
DEFF Research Database (Denmark)
Zimmermann, Niels Henrik; Møller, Henrik; Hansen, John;
2011-01-01
When a stethoscope is placed on the surface of the chest, the coupler picks up sound from heart and lungs transmitted through the tissues of the ribcage and from the surface of the skin. If the acoustic impedance of the chest surface is known, it is possible to optimize the coupler for picking up...
Mutual Radiation Impedance of Uncollapsed CMUT Cells with Different Radii
Ozgurluk, Alper; Atalar, Abdullah; Koymen, Hayrettin
2015-01-01
A polynomial approximation is proposed for the mutual acoustic impedance between uncollapsed capacitive micromachined ultrasonic transducer (CMUT) cells with different radii in an infinite rigid baffle. The resulting approximation is employed in simulating CMUTs with a circuit model. A very good agreement is obtained with the corresponding finite element simulation (FEM) result.
Monitoring of yeast cell concentration using a micromachined impedance sensor
Krommenhoek, E.E.; Gardeniers, J.G.E.; Bomer, J.G.; Berg, van den A.; Li, X.; Ottens, M.; Wielen, van der L.A.M.; Dedem, van G.W.K.; Leeuwen, M.; Gulik, van W.M.; Heijnen, J.J.
2005-01-01
The paper describes the design, modelling and experimental characterization of a micromachined impedance sensor for on-line monitoring of the viable yeast cell concentration (biomass) in a miniaturized cell assay. Measurements in a Saccharomyces cerevisiae cell culture show that the permittivity of
Monitoring of yeast cell concentration using a micromachnined impedance sensor
Krommenhoek, E.E.; Gardeniers, J.G.E.; Bomer, J.G.; Berg, van den A.; Li, X.; Ottens, M.; Wielen, van der L.A.M.; Dedem, van G.W.K.; Leeuwen, van M.; Gulik, van W.M.; Heijnen, J.J.
2006-01-01
This paper describes the design, modeling and experimental characterization of a micromachined impedance sensor for on-line monitoring of the viable yeast cell concentration (biomass) in a miniaturized cell assay. Measurements in Saccharomyces cerevisiae cell culture show that the characteristic fre
On-chip electrical impedance tomography for imaging biological cells.
Sun, Tao; Tsuda, Soichiro; Zauner, Klaus-Peter; Morgan, Hywel
2010-01-15
Electrical impedance tomography is an imaging technology that spatially characterizes the electrical properties of an object. We present a miniaturized electrical impedance tomography system that can image the electrical conductivity distribution within a two-dimensional cell culture. A chip containing a circular 16-electrode array was fabricated using printed circuit board developing technology and used to inject current and to measure spatial voltage across the object. The signal stimulation and voltage data acquisition were performed using an impedance analyzer, operating in four-electrode mode. An open source software, EIDORS was used for image reconstruction. Finite element modelling was used to simulate the image reconstruction process by imaging two ellipsoidal phantoms in the circular 16-electrode array. The effect of the regularization parameter in the reconstruction algorithm and the influence from noise on the fidelity of the images has been numerically analyzed. Experimentally, we show reconstructed images of a multi-nuclear single cellular organism, Physarum Polycephalum, demonstrating the first step towards impedance imaging of single cells in culture. Our system provides a non-invasive lab-on-a-chip technology for spatially mapping the electrical properties of single cells, which would be significant and useful for diagnostic and clinical applications.
A method for suppressing cardiogenic oscillations in impedance pneumography
International Nuclear Information System (INIS)
The transthoracic electrical impedance signal originates from the cardiac and respiratory functions. In impedance pneumography (IP) the lung function is assessed and the cardiac impedance signal, cardiogenic oscillations (CGOs), is considered an additive noise in the measured signal. In order to accurately determine pulmonary flow parameters from the signal, the CGO needs to be attenuated without distorting the respiratory part of the signal. We assessed the suitability of a filtering technique, originally described by Schuessler et al (1998 Ann. Biomed. Eng. 26 260–7) for an esophageal pressure signal, for CGO attenuation in the IP signal. The technique is based on ensemble averaging the CGO events using the electrocardiogram (ECG) R-wave as the trigger signal. Lung volume is known to affect the CGO waveforms. Therefore we modified the filtering method to produce a lung volume-dependent parametric model of the CGO waveform. A simultaneous recording of ECG, IP and pneumotachograph (PNT) was conducted on 41 healthy, sitting adults. The performance of the proposed method was compared to a low-pass filter and a Savitzky–Golay filter in terms of CGO attenuation and respiratory signal distortion. The method was found to be excellent, exhibiting CGO attenuation of 35.0±12.5 dB (mean±SD) and minimal distortion of the respiratory part of the impedance signal
Does strategic planning enhance or impede innovation and firm performance?
Song, Michael; Im, Subin; van der Bij, Hans; Song, Lisa Z.
2011-01-01
Does strategic planning enhance or impede innovation and firm performance? The current literature provides contradictory views. This study extends the resource-advantage theory to examine the conditions in which strategic planning increases or decreases the number of new product development projects
Does Strategic Planning Enhance or Impede Innovation and Firm Performance?
Song, Michael; Im, Subin; Bijl, van der Hans; Song, Lisa Z.
2011-01-01
Does strategic planning enhance or impede innovation and firm performance? The current literature provides contradictory views. This study extends the resource-advantage theory to examine the conditions in which strategic planning increases or decreases the number of new product development projects
Contactless impedance sensors and their application to flow measurements.
Opekar, František; Tůma, Petr; Stulík, Karel
2013-02-27
The paper provides a critical discussion of the present state of the theory of high-frequency impedance sensors (now mostly called contactless impedance or conductivity sensors), the principal approaches employed in designing impedance flow-through cells and their operational parameters. In addition to characterization of traditional types of impedance sensors, the article is concerned with the use of less common sensors, such as cells with wire electrodes or planar cells. There is a detailed discussion of the effect of the individual operational parameters (width and shape of the electrodes, detection gap, frequency and amplitude of the input signal) on the response of the detector. The most important problems to be resolved in coupling these devices with flow-through measurements in the liquid phase are also discussed. Examples are given of cell designs for continuous flow and flow-injection analyses and of detection systems for miniaturized liquid chromatography and capillary electrophoresis. New directions for the use of these sensors in molecular biology and chemical reactors and some directions for future development are outlined.
BIOELECTRICAL IMPEDANCE VECTOR ANALYSIS IDENTIFIES SARCOPENIA IN NURSING HOME RESIDENTS
Loss of muscle mass and water shifts between body compartments are contributing factors to frailty in the elderly. The body composition changes are especially pronounced in institutionalized elderly. We investigated the ability of single-frequency bioelectrical impedance analysis (BIA) to identify b...
Design methodology to enhance high impedance surfaces performances
Directory of Open Access Journals (Sweden)
Michael Grelier
2014-04-01
Full Text Available A methodology is introduced for designing wideband, compact and ultra-thin high impedance surfaces (HIS. A parametric study is carried out to examine the effect of the periodicity on the electromagnetic properties of an HIS. This approach allows designers to reach the best trade-off for HIS performances.
The Current Distribution and Characteristic Impedance of Multiwire Hexaedric Antenna
Z. Novacek
1996-01-01
Both the current distribution and characteristic impedance variations along a hexaedric antenna are analysed in this paper. The presented arrangement by auxiliary wires may ensure equal currents in all antenna wires. The results are required for calculations of the field in the operating volume and may be used for antenna design.
An impedance model of the relativistic heavy ion collider, RHIC
International Nuclear Information System (INIS)
This paper is an abbreviated version of a comprehensive and detailed analysis of RHIC instabilities soon to be published as a RHIC project report. It emphasises longitudinal impedance modeling and design choices in RHIC, wile a companion paper emphasises instability calculations
Lower leg electrical impedance after distal bypass surgery
DEFF Research Database (Denmark)
Belanger, G K; Bolbjerg, M L; Heegaard, N H;
1998-01-01
Electrical impedance was determined in 13 patients following distal bypass surgery to evaluate lower leg oedema as reflected by its circumference. Tissue injury was assessed by the plasma concentration of muscle enzymes. After surgery, the volume of the control lower leg increased from 1250 (816...... to be a useful method for the evaluation of lower leg oedema after distal bypass surgery....
Tunable nanogap devices for ultra-sensitive electrochemical impedance biosensing.
Lu, Yong; Guo, Zheng; Song, Jing-Jing; Huang, Qin-An; Zhu, Si-Wei; Huang, Xing-Jiu; Wei, Yan
2016-01-28
A wealth of research has been available discussing nanogap devices for detecting very small quantities of biomolecules by observing their electrical behavior generally performed in dry conditions. We report that a gold nanogapped electrode with tunable gap length for ultra-sensitive detection of streptavidin based on electrochemical impedance technique. The gold nanogap is fabricated using simple monolayer film deposition and in-situ growth of gold nanoparticles in a traditional interdigitated array (IDA) microelectrode. The electrochemical impedance biosensor with a 25-nm nanogap is found to be ultra-sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin hinder the electron transfer between two electrodes, resulting in a large increase in electron-transfer resistance (Ret) for operating the impedance. A linear relation between the relative Ret and the logarithmic value of streptavidin concentration is observed in the concentration range from 1 pM (picomolar) to 100 nM (nanomolar). The lowest detectable concentration actually measured reaches 1 pM. We believe that such an electrochemical impedance nanogap biosensor provides a useful approach towards biomolecular detection that could be extended to a number of other systems.
Organic electrochemical transistors for cell-based impedance sensing
Rivnay, Jonathan; Ramuz, Marc; Leleux, Pierre; Hama, Adel; Huerta, Miriam; Owens, Roisin M.
2015-01-01
Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.
Monitoring early zeolite formation via in situ electrochemical impedance spectroscopy.
Brabants, G; Lieben, S; Breynaert, E; Reichel, E K; Taulelle, F; Martens, J A; Jakoby, B; Kirschhock, C E A
2016-04-01
Hitherto zeolite formation has not been fully understood. Although electrochemical impedance spectroscopy has proven to be a versatile tool for characterizing ionic solutions, it was never used for monitoring zeolite growth. We show here that EIS can quantitatively monitor zeolite formation, especially during crucial early steps where other methods fall short.
Detailed characterization of anode-supported SOFCs by impedance spectroscopy
DEFF Research Database (Denmark)
Barfod, R.; Mogensen, Mogens Bjerg; Klemensø, Trine;
2007-01-01
Anode-supported thin electrolyte cells are studied by electrochemical impedance spectroscopy (EIS). The aim is to describe how the losses of this type of cells are distributed at low current density (around open-circuit voltage) as a function of temperature. An equivalent circuit consisting...
Organic electrochemical transistors for cell-based impedance sensing
Energy Technology Data Exchange (ETDEWEB)
Rivnay, Jonathan, E-mail: rivnay@emse.fr, E-mail: owens@emse.fr; Ramuz, Marc; Hama, Adel; Huerta, Miriam; Owens, Roisin M., E-mail: rivnay@emse.fr, E-mail: owens@emse.fr [Department of Bioelectronics, Ecole des Mines de St. Etienne, 13541 Gardanne (France); Leleux, Pierre [Department of Bioelectronics, Ecole des Mines de St. Etienne, 13541 Gardanne (France); Microvitae Technologies, Pole d' Activite Y. Morandat, 13120 Gardanne (France)
2015-01-26
Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.
Sensorless battery temperature measurements based on electrochemical impedance spectroscopy
Raijmakers, L. H. J.; Danilov, D. L.; van Lammeren, J. P. M.; Lammers, M. J. G.; Notten, P. H. L.
2014-02-01
A new method is proposed to measure the internal temperature of (Li-ion) batteries. Based on electrochemical impedance spectroscopy measurements, an intercept frequency (f0) can be determined which is exclusively related to the internal battery temperature. The intercept frequency is defined as the frequency at which the imaginary part of the impedance is zero (Zim = 0), i.e. where the phase shift between the battery current and voltage is absent. The advantage of the proposed method is twofold: (i) no hardware temperature sensors are required anymore to monitor the battery temperature and (ii) the method does not suffer from heat transfer delays. Mathematical analysis of the equivalent electrical-circuit, representing the battery performance, confirms that the intercept frequency decreases with rising temperatures. Impedance measurements on rechargeable Li-ion cells of various chemistries were conducted to verify the proposed method. These experiments reveal that the intercept frequency is clearly dependent on the temperature and does not depend on State-of-Charge (SoC) and aging. These impedance-based sensorless temperature measurements are therefore simple and convenient for application in a wide range of stationary, mobile and high-power devices, such as hybrid- and full electric vehicles.
Characterization of antimicrobial peptide activity by electrochemical impedance spectroscopy
Chang, William K.; Wimley, William C.; Searson, Peter C.; Hristova, Kalina; Merzlyakov, Mikhail
2008-01-01
Summary Electrochemical impedance spectroscopy performed on surface-supported bilayer membranes allows for the monitoring of changes in membrane properties, such as thickness, ion permeability, and homogeneity, after exposure to antimicrobial peptides (AMPs). We show that two model cationic peptides, very similar in sequence but different in activity, induce dramatically different changes in membrane properties as probed by impedance spectroscopy. Moreover, the impedance results excluded the “barrel-stave” and the “toroidal pore” models of AMP mode of action, and are more consistent with the “carpet” and the “detergent” models. The impedance data provide important new insights about the kinetics and the scale of the peptide action which currently are not addressed by the “carpet” and the “detergent” models. The method presented not only provides additional information about the mode of action of a particular AMP, but offers a means of characterizing AMP activity in reproducible, well-defined quantitative terms. PMID:18657512
Interpretation of electrochemical impedance spectroscopy (EIS) circuit model for soils
Institute of Scientific and Technical Information of China (English)
韩鹏举; 张亚芬; 陈幼佳; 白晓红
2015-01-01
Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy (EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.
Dynamic impedance of piles in visco-elastic material considering axial loads
Institute of Scientific and Technical Information of China (English)
JIANG Jian-guo; ZHOU Xu-hong; ZHANG Jia-sheng
2005-01-01
The dynamic impedance function of pile in visco-elastie material considering axial loads under lateral dynamic force was analyzed, and the beam dynamic differential equation was used to induce the dynamic impedance function. After analyzing the edge conditions, the dynamic impedance functions were deduced. Contrasted with the result that does not consider axial loads, the axial loads have obvious influence on the dynamic impedance function.And the results show that the dimensionless prarmeter of the dynamic impedance will change from 6 % to 9 % when considering axial loads, and dimensionless prarmeter of the dynamic impedance of the coupling horizontal-sway will increase by 31 %.
Modern Trends in Imaging XI: Impedance Measurements in the Biomedical Sciences
Directory of Open Access Journals (Sweden)
Frederick D. Coffman
2012-01-01
Full Text Available Biological organisms and their component organs, tissues and cells have unique electrical impedance properties. Impedance properties often change with changes in structure, composition, and metabolism, and can be indicative of the onset and progression of disease states. Over the past 100 years, instruments and analytical methods have been developed to measure the impedance properties of biological specimens and to utilize these measurements in both clinical and basic science settings. This chapter will review the applications of impedance measurements in the biomedical sciences, from whole body analysis to impedance measurements of single cells and cell monolayers, and how cellular impedance measuring instruments can now be used in high throughput screening applications.
Impedance characteristics of the Bz diode on the LION accelerator
International Nuclear Information System (INIS)
The LION accelerator at Cornell University is being used to study the characteristics of the applied B/sub z/, or 'barrel' diode. This 0.8 TW, 4 ohm, ion accelerator has the ability to take several shots per day, and hence alloys systematic scans to be performed. An important result of a recent series of experiments is that the diode impedance remains relatively constant, decaying only slowly, during the 50 nsec pulse. When the diode is operated with a 4.5 mm gap and a 21 kG insulating magnetic field, the typical diode parameters, are a voltage of 1 MV and a total current of 250 kA, leading to a diode impedance of 4 ohms and power of 0.25 TW. The diode impedance decays with a 100 nsec time constant. The ion beams have peak currents of roughly 125 kA and typical impedances of Bohms, which decays with a time constant of 25 nsec. The Child-Langmuir gap was approximately 2 mm and closed with a velocity of roughly 2X10/sup 6/ cm/sec. Current experimental work is aimed at characterizing the impedance of the B/sub z/ diode as a function of the applied magnetic field, the A-K gap, the anode curvature, and the anode groove parameters. In addition, the effect of changing the voltage rise with a plasma opening switch and of adding an electron limiter is examined. The ion beam quality is examined at the focus of the barrel diode with a swept Thomson parabola and various Rutherford scattering diagnostics
Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes
Ruffo, Riccardo
2009-07-02
The impedance behavior of silicon nanowire electrodes has been investigated to understand the electrochemical process kinetics that influences the performance when used as a high-capacity anode in a lithium ion battery. The ac response was measured by using impedance spectroscopy in equilibrium conditions at different lithium compositions and during several cycles of charge and discharge in a half cell vs. metallic lithium. The impedance analysis shows the contribution of both surface resistance and solid state diffusion through the bulk of the nanowires. The surface process is dominated by a solid electrolyte layer (SEI) consisting of an inner, inorganic insoluble part and several organic compounds at the outer interface, as seen by XPS analysis. The surface resistivity, which seems to be correlated with the Coulombic efficiency of the electrode, grows at very high lithium contents due to an increase in the inorganic SEI thickness. We estimate the diffusion coefficient of about 2 × 10 -10 cm 2/s for lithium diffusion in silicon. A large increase in the electrode impedance was observed at very low lithium compositions, probably due to a different mechanism for lithium diffusion inside the wires. Restricting the discharge voltage to 0.7 V prevents this large impedance and improves the electrode lifetime. Cells cycled between 0.07 and 0.70 V vs. metallic lithium at a current density of 0.84 A/g (C/5) showed good Coulombic efficiency (about 99%) and maintained a capacity of about 2000 mAh/g after 80 cycles. © 2009 American Chemical Society.
A mathematical model for electrical impedance spectroscopy of zwitterionic hydrogels.
Feicht, Sarah E; Khair, Aditya S
2016-08-17
We report a mathematical model for ion transport and electrical impedance in zwitterionic hydrogels, which possess acidic and basic functional groups that carry a net charge at a pH not equal to the isoelectric point. Such hydrogels can act as an electro-mechanical interface between a relatively hard biosensor and soft tissue in the body. For this application, the electrical impedance of the hydrogel must be characterized to ensure that ion transport to the biosensor is not significantly hindered. The electrical impedance is the ratio of the applied voltage to the measured current. We consider a simple model system, wherein an oscillating voltage is applied across a hydrogel immersed in electrolyte and sandwiched between parallel, blocking electrodes. We employ the Poisson-Nernst-Planck (PNP) equations coupled with acid-base dissociation reactions for the charge on the hydrogel backbone to model the ionic transport across the hydrogel. The electrical impedance is calculated from the numerical solution to the PNP equations and subsequently analyzed via an equivalent circuit model to extract the hydrogel capacitance, resistance, and the capacitance of electrical double layers at the electrode-hydrogel interface. For example, we predict that an increase in pH from the isoelectric point, pH = 6.4 for a model PCBMA hydrogel, to pH = 8 reduces the resistance of the hydrogel by ∼40% and increases the double layer capacitance by ∼250% at an electrolyte concentration of 0.1 mM. The significant impact of charged hydrogel functional groups to the impedance is damped at higher electrolyte concentration. PMID:27464763
Energy Technology Data Exchange (ETDEWEB)
Petracca, S. [Salerno Univ. (Italy)
1996-08-01
Debye potentials, the Lorentz reciprocity theorem, and (extended) Leontovich boundary conditions can be used to obtain simple and accurate analytic estimates of the longitudinal and transverse coupling impedances of (piecewise longitudinally uniform) multi-layered pipes with non simple transverse geometry and/or (spatially inhomogeneous) boundary conditions. (author)
Kimura, Tomoharu; Kobayashi, Kei; Yamada, Hirofumi
2015-08-01
The device performances of organic thin film transistors are often limited by the metal-organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.
Pliquett, Uwe
2013-04-01
Over recent years advanced measurement methods have facilitated outstanding achievements not only in medical instrumentation but also in biotechnology. Impedance measurement is a simple and innocuous way to characterize materials. For more than 40 years biological materials, most of them based on cells, have been characterized by means of electrical impedance for quality control of agricultural products, monitoring of biotechnological or food processes or in health care. Although the list of possible applications is long, very few applications successfully entered the market before the turn of the century. This was, on the one hand, due to the low specificity of electrical impedance with respect to other material properties because it is influenced by multiple factors. On the other hand, equipment and methods for many potential applications were not available. With the appearance of microcontrollers that could be easily integrated in applications at the beginning of the 1980s, impedance measurement advanced as a valuable tool in process optimization and lab automation. However, established methods and data processing were mostly used in a new environment. This has changed significantly during the last 10 years with a dramatic growth of the market for medical instrumentation and also for biotechnological applications. Today, advanced process monitoring and control require fast and highly parallel electrical characterization which in turn yields incredible data volumes that must be handled in real time. Many newer developments require miniaturized but precise sensing methods which is one of the main parts of Lab-on-Chip technology. Moreover, biosensors increasingly use impedometric transducers, which are not compatible with the large expensive measurement devices that are common in the laboratory environment. Following the achievements in the field of bioimpedance measurement, we will now witness a dramatic development of new electrode structures and electronics
Tian, Lian; Hunter, Kendall S; Kirby, K Scott; Ivy, D Dunbar; Shandas, Robin
2010-06-01
Pulmonary vascular input impedance better characterizes right ventricular (RV) afterload and disease outcomes in pulmonary hypertension compared to the standard clinical diagnostic, pulmonary vascular resistance (PVR). Early efforts to measure impedance were not routine, involving open-chest measurement. Recently, the use of pulsed-wave (PW) Doppler-measured velocity to non-invasively estimate instantaneous flow has made impedance measurement more practical. One critical concern remains with clinical use: the measurement uncertainty, especially since previous studies only incorporated random error. This study utilized data from a large pediatric patient population to comprehensively examine the systematic and random error contributions to the total impedance uncertainty and determined the least error prone methodology to compute impedance from among four different methods. We found that the systematic error contributes greatly to the total uncertainty and that one of the four methods had significantly smaller propagated uncertainty; however, even when this best method is used, the uncertainty can be large for input impedance at high harmonics and for the characteristic impedance modulus. Finally, we found that uncertainty in impedance between normotensive and hypertensive patient groups displays no significant difference. It is concluded that clinical impedance measurement would be most improved by advancements in instrumentation, and the best computation method is proposed for future clinical use of the input impedance.
Deurenberg, P; Andreoli, A; de Lorenzo, A
1996-01-01
Total body water and extracellular water were measured by deuterium oxide and bromide dilution respectively in 23 healthy males and 25 healthy females. In addition, total body impedance was measured at 17 frequencies, ranging from 1 kHz to 1350 kHz. Modelling programs were used to extrapolate impedance values to frequency zero (extracellular resistance) and frequency infinity (total body water resistance). Impedance indexes (height2/Zf) were computed at all 17 frequencies. The estimation errors of extracellular resistance and total body water resistance were 1% and 3%, respectively. Impedance and impedance index at low frequency were correlated with extracellular water, independent of the amount of total body water. Total body water showed the greatest correlation with impedance and impedance index at high frequencies. Extrapolated impedance values did not show a higher correlation compared to measured values. Prediction formulas from the literature applied to fixed frequencies showed the best mean and individual predictions for both extracellular water and total body water. It is concluded that, at least in healthy individuals with normal body water distribution, modelling impedance data has no advantage over impedance values measured at fixed frequencies, probably due to estimation errors in the modelled data.
International Nuclear Information System (INIS)
Pulmonary vascular input impedance better characterizes right ventricular (RV) afterload and disease outcomes in pulmonary hypertension compared to the standard clinical diagnostic, pulmonary vascular resistance (PVR). Early efforts to measure impedance were not routine, involving open-chest measurement. Recently, the use of pulsed-wave (PW) Doppler-measured velocity to non-invasively estimate instantaneous flow has made impedance measurement more practical. One critical concern remains with clinical use: the measurement uncertainty, especially since previous studies only incorporated random error. This study utilized data from a large pediatric patient population to comprehensively examine the systematic and random error contributions to the total impedance uncertainty and determined the least error prone methodology to compute impedance from among four different methods. We found that the systematic error contributes greatly to the total uncertainty and that one of the four methods had significantly smaller propagated uncertainty; however, even when this best method is used, the uncertainty can be large for input impedance at high harmonics and for the characteristic impedance modulus. Finally, we found that uncertainty in impedance between normotensive and hypertensive patient groups displays no significant difference. It is concluded that clinical impedance measurement would be most improved by advancements in instrumentation, and the best computation method is proposed for future clinical use of the input impedance
Micro-Horn Arrays for Ultrasonic Impedance Matching
Rao, Shanti; Palmer, Dean
2009-01-01
Thin-layered structures containing arrays of micromachined horns, denoted solid micro-horn arrays (SMIHAs), have been conceived as improved means of matching acoustic impedances between ultrasonic transducers and the media with which the transducers are required to exchange acoustic energy. Typically, ultrasonic transducers (e.g., those used in medical imaging) are piezoelectric or similar devices, which produce small displacements at large stresses. However, larger displacements at smaller stresses are required in the target media (e.g., human tissues) with which acoustic energy is to be exchanged. Heretofore, efficiencies in transmission of acoustic energy between ultrasonic transducers and target media have been severely limited because substantial mismatches of acoustic impedances have remained, even when coupling material layers have been interposed between the transducers and the target media. In contrast, SMIHAs can, in principle, be designed to effect more nearly complete acoustic impedance matching, leading to power transmission efficiencies of 90 percent or even greater. The SMIHA concept is based on extension, into the higher-frequency/ lower-wavelength ultrasonic range, of the use of horns to match acoustic impedances in the audible and lower-frequency ultrasonic ranges. In matching acoustic impedance in transmission from a higher-impedance acoustic source (e.g., a piezoelectric transducer) and a lowerimpedance target medium (e.g., air or human tissue), a horn acts as a mechanical amplifier. The shape and size of the horn can be optimized for matching acoustic impedance in a specified frequency range. A typical SMIHA would consist of a base plate, a face plate, and an array of horns that would constitute pillars that connect the two plates (see figure). In use, the base plate would be connected to an ultrasonic transducer and the face plate would be placed in contact with the target medium. As at lower frequencies, the sizes and shapes of the pillars
DEFF Research Database (Denmark)
Kim, Kseniya; Zhurbenko, Vitaliy; Johansen, Tom Keinicke;
2012-01-01
to a traditional tapered line impedance transformer. The increase in bandwidth of nonsynchronous noncommensurate impedance transformers typically leads to shortening the transformer length, which makes the transformer attractive for applications, where a wide operating band and high transformation ratios...
Architecture, modeling, and analysis of a plasma impedance probe
Jayaram, Magathi
Variations in ionospheric plasma density can cause large amplitude and phase changes in the radio waves passing through this region. Ionospheric weather can have detrimental effects on several communication systems, including radars, navigation systems such as the Global Positioning Sytem (GPS), and high-frequency communications. As a result, creating models of the ionospheric density is of paramount interest to scientists working in the field of satellite communication. Numerous empirical and theoretical models have been developed to study the upper atmosphere climatology and weather. Multiple measurements of plasma density over a region are of marked importance while creating these models. The lack of spatially distributed observations in the upper atmosphere is currently a major limitation in space weather research. A constellation of CubeSat platforms would be ideal to take such distributed measurements. The use of miniaturized instruments that can be accommodated on small satellites, such as CubeSats, would be key to achieving these science goals for space weather. The accepted instrumentation techniques for measuring the electron density are the Langmuir probes and the Plasma Impedance Probe (PIP). While Langmuir probes are able to provide higher resolution measurements of relative electron density, the Plasma Impedance Probes provide absolute electron density measurements irrespective of spacecraft charging. The central goal of this dissertation is to develop an integrated architecture for the PIP that will enable space weather research from CubeSat platforms. The proposed PIP chip integrates all of the major analog and mixed-signal components needed to perform swept-frequency impedance measurements. The design's primary innovation is the integration of matched Analog-to-Digital Converters (ADC) on a single chip for sampling the probes current and voltage signals. A Fast Fourier Transform (FFT) is performed by an off-chip Field-Programmable Gate Array (FPGA
Wave impedances of drill strings and other periodic media
Drumheller, Douglas S.
2002-12-01
It is commonly known that wave reflections are caused by abrupt spatial variations in the physical parameter called wave impedance. When a material contains a spatially periodic distribution of wave impedances some very interesting and complex wave propagation phenomena will occur. Two examples of such periodic structures immediately come to mind: the first is a sandwiched structure of two types of plates, say for example, identical layers of thin steel plates interspersed with identical thick aluminum plates; and the second is a large number of identical long thin pipes that are connected from end to end with identical short heavy threaded couplings. The pipe assembly is our primary concern here because it represents the drill string, used worldwide to drill for natural energy resources. We want to understand how waves propagate through drill strings because we want to use them as a means of communication. But while the second structure is our primary concern, it is the study of the first structure, composed of layers, that is the truly historical problem and the source of much of our understanding of this rich set of wave physics. Traditionally, wave propagation in periodic media has been studied as an eigenvalue problem. The eigenvalues themselves yield information about phase velocities, group velocities, passbands, and stopbands. Most often the analysis has stopped there and the eigenvectors have been ignored. Here we turn our attention to the eigenvectors, using them to evaluate the impedance of the periodic structure with particular emphasis on the periodic drill string. As you might expect the impedance of the drill string is a complex number, which is evaluated from a very complicated expression. However, we have discovered that the impedance at two physical locations along the length of each piece of drill pipe in the drill string always reduces to a real number. This is immensely important because it allows us to match the impedance of the drill string
An Electrochemical Impedance Study of the Capacity Limitations in Na–O2 Cells
DEFF Research Database (Denmark)
Knudsen, Kristian Bastholm; Nichols, Jessica E.; Vegge, Tejs;
2016-01-01
Electrochemical impedance spectroscopy, pressure change measurements, and scanning electron microscopy were used to investigate the nonaqueous Na–O2 cell potential decrease and rise (sudden deaths) on discharge and charge, respectively. To fit the impedance spectra from operating cells, an equiva......Electrochemical impedance spectroscopy, pressure change measurements, and scanning electron microscopy were used to investigate the nonaqueous Na–O2 cell potential decrease and rise (sudden deaths) on discharge and charge, respectively. To fit the impedance spectra from operating cells...
Electrochemical impedance studies of AB{sub 5}-type hydrogen storage alloy
Energy Technology Data Exchange (ETDEWEB)
Slepski, Pawel; Darowicki, Kazimierz; Andrearczyk, Karolina [Department of Electrochemistry Corrosion and Materials Engineering, Gdansk University of Technology, 11/12 Narutowicza Street, 80-233 Gdansk (Poland); Kopczyk, Maciej; Sierczynska, Agnieszka [Institute of Non-ferrous Metals, Department in Poznan, Central Laboratory of Batteries and Cells, 12 Forteczna Street, 61-362 Poznan (Poland)
2010-05-01
Electrochemical impedance spectroscopy technique was used to describe behavior of AB{sub 5}-type hydrogen storage alloy. Impedance investigations were performed during cyclic voltammetry measurement and charge/discharge cycles. The comprehensive interpretation of instantaneous impedance spectra obtained in potentiostatic mode allowed further to interpret impedance results in galvanostatic mode. Proposed methodology enabled to trace electrical parameters as a function of state of charge (SOC) and depth of discharge (DOD). (author)
A method to separate process contributions in impedance spectra by variation of test conditions
DEFF Research Database (Denmark)
Jensen, Søren Højgaard; Hauch, Anne; Hendriksen, Peter Vang;
2007-01-01
Many processes contribute to the overall impedance of an electrochemical cell, and these may be difficult to separate in the impedance spectrum. Here, we present an investigation of a solid oxide fuel cell based on differences in impedance spectra due to a change of operating parameters and present...... the result as the derivative of the impedance with respect to ln(f). The method is used to separate the anode and cathode contributions and to identify various types of processes....
A CMOS Electrochemical Impedance Spectroscopy (EIS) Biosensor Array.
Manickam, Arun; Chevalier, Aaron; McDermott, Mark; Ellington, Andrew D; Hassibi, Arjang
2010-12-01
In this paper, we present a fully integrated biosensor 10 × 10 array in a standard complementary metal-oxide semiconducor process, which takes advantage of electrochemical impedance spectroscopy (EIS). We also show that this system is able to detect various biological analytes, such as DNA and proteins, in real time and without the need for molecular labels. In each pixel of this array, we implement a biocompatible Au electrode transducer and embedded sensor circuitry which takes advantage of the coherent detector to measure the impedance of the associated electrode-electrolyte interface. This chip is capable of concurrently measuring admittance values as small as 10(-8) Ω(-1) within the array with the detection dynamic range of more than 90 dB in the frequency range of 10 Hz-50 MHz. PMID:23850755
Beam steering and impedance matching of plasmonic horn nanoantennas
Afridi, Adeel
2016-01-01
In this paper, we study a plasmonic horn nanoantenna on a metal-backed substrate. The horn nanoantenna structure consists of a two-wire transmission line (TWTL) flared at the end. We analyze the effect of the substrate thickness on the nanoantenna's radiation pattern, and demonstrate beam steering in a broad range of elevation angles. Furthermore, we analyze the effect of the ground plane on the impedance matching between the antenna and the TWTL, and observe that the ground plane increases the back reflection into the waveguide. To reduce the reflection, we develop a transmission line model to design an impedance matching section which leads to 99.75% power transmission to the nanoantenna.
Gemstone Grinding Process Improvement by using Impedance Force Control
Directory of Open Access Journals (Sweden)
Hamprommarat Chumpol
2015-01-01
Full Text Available Chula Automatic Faceting Machine has been developed by The Advance Manufacturing Research Lab, Chulalongkorn University to support Thailand Gems-Industry. The machine has high precision motion control by using position and force control. A contact stiffness model is used to estimate grinding force. Although polished gems from the Faceting Machine have uniform size and acceptable shape, the force of the grinding and polishing process cannot be maintain constant and has some fluctuation due to indirect force control. Therefor this research work propose a new controller for this process based on an impedance direct force control to improve the gemstone grinding performance during polishing process. The grinding force can be measured through motor current. The results show that the polished gems by using impedance direct force control can maintain uniform size as well as good shape and high quality surface.
Acoustic Wavefront Manipulation: Impedance Inhomogeneity and Extraordinary Reflection
Zhao, Jiajun; Chen, Zhining; Li, Baowen
2013-01-01
Optical wavefront can be manipulated by interfering elementary beams with phase inhomogeneity. Therefore a surface allowing huge, abrupt and position-variant phase change would enable all possibilities of wavefront engineering. However, one may not have the luxury of efficient abrupt-phase-changing materials in acoustics. This motivates us to establish a counterpart mechanism for acoustics, in order to empower the wide spectrum of novel acoustic applications. Remarkably, the proposed impedance-governed generalized Snell's law (IGSL) of reflection is distinguished from that in optics. Via the manipulation of inhomogeneous acoustic impedance, extraordinary reflection can be tailored for unprecedented wavefront manipulation while ordinary reflection can be surprisingly switched on or off. Our results may power the acoustic-wave manipulation and engineering. We demonstrate novel acoustic applications by planar surfaces designed with IGSL.
Impedance effect of manganite thin film-based photodetectors
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
We report on the photodetector structures based on perovskite manganite La0.67Ca0.33MnO3 thin films on tilted SrTiO3 (001) substrates. The photovoltaic effect has been observed in response to excitation by 308 nm ultraviolet laser pulse irradiation in duration of 20 ns at room temperature. The outputs obtained required no amplification. To reduce the deformation of the signal detected, a series of testing measurements were made to investigate the impedance effect. When the impedance at the oscilloscope end matched to the co-axis cable, the signal trace was almost triangular and symmetrical, with response time equal to the excitation laser. In addation, the response linearly depends on the irradiated area for low on-sample energy. The devices work well under unbiased conditions and so are simple to configure for practical applications.
Dielectrophoresis and dielectrophoretic impedance detection of adenovirus and rotavirus
Nakano, Michihiko; Ding, Zhenhao; Suehiro, Junya
2016-01-01
The aim of this study is the electrical detection of pathogenic viruses, namely, adenovirus and rotavirus, using dielectrophoretic impedance measurement (DEPIM). DEPIM consists of two simultaneous processes: dielectrophoretic trapping of the target and measurement of the impedance change and increase in conductance with the number of trapped targets. This is the first study of applying DEPIM, which was originally developed to detect bacteria suspended in aqueous solutions, to virus detection. The dielectric properties of the viruses were also investigated in terms of their dielectrophoretic behavior. Although their estimated dielectric properties were different from those of bacteria, the trapped viruses increased the conductance of the microelectrode in a manner similar to that in bacteria detection. We demonstrated the electrical detection of viruses within 60 s at concentrations as low as 70 ng/ml for adenovirus and 50 ng/ml for rotavirus.
An Electrochemical Impedance Spectroscopy System for Monitoring Pineapple Waste Saccharification.
Conesa, Claudia; Ibáñez Civera, Javier; Seguí, Lucía; Fito, Pedro; Laguarda-Miró, Nicolás
2016-01-01
Electrochemical impedance spectroscopy (EIS) has been used for monitoring the enzymatic pineapple waste hydrolysis process. The system employed consists of a device called Advanced Voltammetry, Impedance Spectroscopy & Potentiometry Analyzer (AVISPA) equipped with a specific software application and a stainless steel double needle electrode. EIS measurements were conducted at different saccharification time intervals: 0, 0.75, 1.5, 6, 12 and 24 h. Partial least squares (PLS) were used to model the relationship between the EIS measurements and the sugar determination by HPAEC-PAD. On the other hand, artificial neural networks: (multilayer feed forward architecture with quick propagation training algorithm and logistic-type transfer functions) gave the best results as predictive models for glucose, fructose, sucrose and total sugars. Coefficients of determination (R²) and root mean square errors of prediction (RMSEP) were determined as R² > 0.944 and RMSEP 0.973 and RMSEP pineapple waste saccharification step. PMID:26861317
High accuracy particle analysis using sheathless microfluidic impedance cytometry.
Spencer, Daniel; Caselli, Federica; Bisegna, Paolo; Morgan, Hywel
2016-07-01
This paper describes a new design of microfluidic impedance cytometer enabling accurate characterization of particles without the need for focusing. The approach uses multiple pairs of electrodes to measure the transit time of particles through the device in two simultaneous different current measurements, a transverse (top to bottom) current and an oblique current. This gives a new metric that can be used to estimate the vertical position of the particle trajectory through the microchannel. This parameter effectively compensates for the non-uniform electric field in the channel that is an unavoidable consequence of the use of planar parallel facing electrodes. The new technique is explained and validated using numerical modelling. Impedance data for 5, 6 and 7 μm particles are collected and compared with simulations. The method gives excellent coefficient of variation in (electrical) radius of particles of 1% for a sheathless configuration.
Time-domain based impedance measurement: strengths and drawbacks
International Nuclear Information System (INIS)
While most applications of bio-impedance measurements for characterization of cells or tissue do not have any time requirements, newer developments like real time monitoring of moving cells or membrane recovery after high voltage application depend on fast measurement. This is not compatible with sweeping the frequency through the desired range while assessing magnitude and phase of the material under test (MUT). A high speed is only achievable by using broad-bandwidth excitation signals and monitoring the response in time-domain. Time-domain based methods can be distinguished by the excitation signals as well as by assessing the transmission or reflection behavior of the MUT. Although there is good agreement regarding the advantages of fast measurements, time-domain measurements are often rejected because of low precision and noise sensitivity. This paper points not only the advantages of impedance measurements in time domain but shows also drawbacks together with possible solutions.
Impedance of tissue-mimicking phantom material under compression
Directory of Open Access Journals (Sweden)
Barry Belmont
2013-02-01
Full Text Available The bioimpedance of tissues under compression is a field in need of study. While biological tissues can become compressed in a myriad of ways, very few experiments have been conducted to describe the relationship between the passive electrical properties of a material (impedance/admittance during mechanical deformation. Of the investigations that have been conducted, the exodus of fluid from samples under compression has been thought to be the cause of changes in impedance, though until now was not measured directly. Using a soft tissue-mimicking phantom material (tofu whose passive electrical properties are a function of the conducting fluid held within its porous structure, we have shown that the mechanical behavior of a sample under compression can be measured through bioimpedance techniques.
Structural damage identification using piezoelectric impedance and Bayesian inference
Shuai, Q.; Zhou, K.; Tang, J.
2015-04-01
Structural damage identification is a challenging subject in the structural health monitoring research. The piezoelectric impedance-based damage identification, which usually utilizes the matrix inverse-based optimization, may in theory identify the damage location and damage severity. However, the sensitivity matrix is oftentimes ill-conditioned in practice, since the number of unknowns may far exceed the useful measurements/inputs. In this research, a new method based on intelligent inference framework for damage identification is presented. Bayesian inference is used to directly predict damage location and severity using impedance measurement through forward prediction and comparison. Gaussian process is employed to enrich the forward analysis result, thereby reducing computational cost. Case study is carried out to illustrate the identification performance.
Impedance function of a group of vertical piles
International Nuclear Information System (INIS)
Impedance and transfer functions of a group of vertical piles located in any desired configuration in plan in a horizontally stratified soil layer are derived. Hysteretic and radiation damping are accounted for. The method separates the piles and the soil, introducing unknown interaction forces. The total flexibility matrix of the soil is constructed, superposing the (complex) flexibility coefficients caused by the interaction forces of a single pile only. The dependence of the impedance and transfer functions on the oscllating frequency for foundations with different numbers of piles is investigated. Pile-soil-pile interaction is shown to be very important for all modes of vibration. The procedure is used in the seismic analysis of a reactor building. (Author)
Traceable calibration of impedance heads and artificial mastoids
International Nuclear Information System (INIS)
Artificial mastoids are devices which simulate the mechanical characteristics of the human head, and in particular of the bony structure behind the ear. They are an essential tool in the calibration of bone-conduction hearing aids and audiometers. With the emergence of different types of artificial mastoids in the market, and the realisation that the visco-elastic part of these instruments changes over time, the development of a method of traceable calibration of these devices without relying on commercial software has become important for national metrology institutes. This paper describes commercially available calibration methods, and the development of a traceable calibration method including the traceable calibration of the impedance head used to measure the mechanical impedance of the artificial mastoid. (paper)
High resolution impedance manometric findings in dysphagia of Huntington's disease
Institute of Scientific and Technical Information of China (English)
Tae Hee Lee; Joon Seong Lee; Wan Jung Kim
2012-01-01
Conventional manometry presents significant challenges,espedally in assessment of pharyngeal swallowing,because of the asymmetry and deglutitive movements of oropharyngeal structures.It only provides information about intraluminal pressure and thus it is difficult to study functional details of esophageal motility disorders.New technology of solid high resolution impedance manometry (HRIM),with 32 pressure sensors and 6 impedance sensors,is likely to provide better assessment of pharyngeal swallowing as well as more information about esophageal motility disorders.However,the clinical usefulness of application of HRIM in patients with oropharyngeal dysphagia or esophageal dysphagia is not known.We experienced a case of Huntington's disease presenting with both oropharyngeal and esophageal dysphagia,in which HRIM revealed the mechanism of oropharyngeal dysphagia and provided comprehensive information about esophageal dysphagia.
Meandered-line antenna with integrated high-impedance surface.
Energy Technology Data Exchange (ETDEWEB)
Forman, Michael A.
2010-09-01
A reduced-volume antenna composed of a meandered-line dipole antenna over a finite-width, high-impedance surface is presented. The structure is novel in that the high-impedance surface is implemented with four Sievenpiper via-mushroom unit cells, whose area is optimized to match the meandered-line dipole antenna. The result is an antenna similar in performance to patch antenna but one fourth the area that can be deployed directly on the surface of a conductor. Simulations demonstrate a 3.5 cm ({lambda}/4) square antenna with a bandwidth of 4% and a gain of 4.8 dBi at 2.5 GHz.
Traceable calibration of impedance heads and artificial mastoids
Scott, D. A.; Dickinson, L. P.; Bell, T. J.
2015-12-01
Artificial mastoids are devices which simulate the mechanical characteristics of the human head, and in particular of the bony structure behind the ear. They are an essential tool in the calibration of bone-conduction hearing aids and audiometers. With the emergence of different types of artificial mastoids in the market, and the realisation that the visco-elastic part of these instruments changes over time, the development of a method of traceable calibration of these devices without relying on commercial software has become important for national metrology institutes. This paper describes commercially available calibration methods, and the development of a traceable calibration method including the traceable calibration of the impedance head used to measure the mechanical impedance of the artificial mastoid.
On accurate differential measurements with electrochemical impedance spectroscopy
Kernbach, S; Kernbach, O
2016-01-01
This paper describes the impedance spectroscopy adapted for analysis of small electrochemical changes in fluids. To increase accuracy of measurements the differential approach with temperature stabilization of fluid samples and electronics is used. The impedance analysis is performed by the single point DFT, signal correlation, calculation of RMS amplitudes and interference phase shift. For test purposes the samples of liquids and colloids are treated by fully shielded electromagnetic generators and passive cone-shaped structures. Fluidic samples collected from different geological locations are also analysed. In all tested cases we obtained different results for impacted and non-impacted samples, moreover, a degradation of electrochemical stability after treatment is observed. This method is used in laboratory analysis of weak emissions and ensures a high repeatability of results.
Development of a radio frequency excited local impedance probe
International Nuclear Information System (INIS)
Local void fraction measurements were made with a Karlsruhe type impedance probe. The probe was operated at radiofrequency to minimize sensitivity to liquid phase resistivity. Two types of signal thresholding were used: level and derivative. A dual beam X-ray system was used as a calibration standard for the radio frequency excited impedance probe. Calibration was performed in vertical air/water flows. Derivative thresholding was found to be preferable to level thresholding, however, in both schemes hydrodynamic and surface tension effects were observed below a liquid superficial velocity of 0.5 m/s. Table salt (NaCl) was added to the water to verify the probe's response to changing water resistivity. Derivative thresholding appeared to work quite well but level thresholding was found to be inadequate due to the change in capacitance. (orig.)
Object impedance control for cooperative manipulation - Theory and experimental results
Schneider, Stanley A.; Cannon, Robert H., Jr.
1992-01-01
This paper presents the dynamic control module of the Dynamic and Strategic Control of Cooperating Manipulators (DASCCOM) project at Stanford University's Aerospace Robotics Laboratory. First, the cooperative manipulation problem is analyzed from a systems perspective, and the desirable features of a control system for cooperative manipulation are discussed. Next, a control policy is developed that enforces a controlled impedance not of the individual arm endpoints, but of the manipulated object itself. A parallel implementation for a multiprocessor system is presented. The controller fully compensates for the system dynamics and directly controls the object internal forces. Most importantly, it presents a simple, powerful, intuitive interface to higher level strategic control modules. Experimental results from a dual two-link-arm robotic system are used to compare the object impedance controller with other strategies, both for free-motion slews and environmental contact.
An electrochemical impedance model for integrated bacterial biofilms
Energy Technology Data Exchange (ETDEWEB)
Ben-Yoav, Hadar, E-mail: benyoav@post.tau.ac.il [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University (Israel); Freeman, Amihay [Department of Molecular Microbiology and Biotechnology, Faculty of Life Sciences, Tel Aviv University (Israel); Sternheim, Marek [The Center for Nanoscience and Nanotechnology, Tel Aviv University (Israel); Shacham-Diamand, Yosi [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University (Israel)
2011-09-30
Bacterial cells attachment onto solid surfaces and the following growth into mature microbial biofilms may result in highly antibiotic resistant biofilms. Such biofilms may be incidentally formed on tissues or implanted devices, or intentionally formed by directed deposition of microbial sensors on whole-cell bio-chip surface. A new method for electrical characterization of the later on-chip microbial biofilm buildup is presented in this paper. Measurement of impedance vs. frequency in the range of 100 mHz to 400 kHz of Escherichia coli cells attachment to indium-tin-oxide-coated electrodes was carried out while using optical microscopy estimating the electrode area coverage. We show that impedance spectroscopy measurements can be interpreted by a simple electrical equivalent model characterizing both attachment and growth of the biofilm. The correlation of extracted equivalent electrical lumped components with the visual biofilm parameters and their dependence on the attachment and growth phases is confirmed.
The AC Impedance Characteristic of High Power Li4Ti5O12-based Battery Cells
DEFF Research Database (Denmark)
Stroe, Ana-Irina; Stroe, Daniel Loan; Swierczynski, Maciej Jozef;
2015-01-01
This paper studies the impedance characteristics of a fresh 13 Ah high-power lithium titanate oxide (LTO) battery cell and analyses its dependence on the temperature and state-of-charge. The impedance of the battery cell was measured by means of the electrochemical impedance spectroscopy (EIS) te...
Deurenberg, P.R.M.; Deurenberg-Yap, M.; Schouten, F.J.M.
2002-01-01
Methods: Anthropometric parameters were measured in addition to impedance (100 kHz) of the total body, arms and legs. Impedance indexes were calculated as height2/impedance. Arm length (span) and leg length (sitting height), wrist and knee width were measured from which body build indices were calcu
Boukamp, Bernard A.
1993-01-01
A method is presented for executing the Kramers-Kronig transforms of electrochemical impedance data on a computer. Attention is paid to the extrapolation techniques for impedance data with a limited frequency range. It is shown that impedance spectra of systems with blocking electrodes, exhibiting a
Electrical Impedance of Acupuncture Meridians: The Relevance of Subcutaneous Collagenous Bands
Ahn, Andrew C.; Min Park; Shaw, Jessica R; McManus, Claire A.; Kaptchuk, Ted J.; Langevin, Helene M.
2010-01-01
Background: The scientific basis for acupuncture meridians is unknown. Past studies have suggested that acupuncture meridians are physiologically characterized by low electrical impedance and anatomically associated with connective tissue planes. We are interested in seeing whether acupuncture meridians are associated with lower electrical impedance and whether ultrasound-derived measures – specifically echogenic collagenous bands - can account for these impedance differences. Methods/Results...
AC Complex Impedance Analysis of Doped Strontium Titanate Multifunctional Ceramics
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Doped SrTiO3 capacitor-varistor multifunctional ceramics were fabricated by a single sintering process. AC compleximpedance analysis was performed to investigate electrical features ofgrains and grain boundaries for both as-reducedceramic and reoxidized ceramics. The results showed that the as-reduced ceramic exhibited inductive response athigh frequencies above 2 MHz, which is attributed to the contribution of electron behavior in semiconducting grains.The high frequency inductive response disappeared in impedance plots of reoxidized ceramics.
Design and Analysis of Impedance Pumps Utilizing Electromagnetic Actuation
Yu-Hisang Wang; Yao-Wen Tsai; Chien-Hsiung Tsai; Chia-Yen Lee; Lung-Ming Fu
2010-01-01
This study designs and analyzes an impedance pump utilizing an electromagnetic actuator. The pump is designed to have three major components, namely a lower glass substrate patterned with a copper micro-coil, a microchannel, and an upper glass cover plate attached a magnetic PDMS diaphragm. When a current is passed through the micro-coil, an electromagnetic force is established between the coil and the magnetic diaphragm. The resulting deflection of the PDMS diaphragm creates an acoustic impe...
Modes and exceptional points in waveguides with impedance boundary conditions
Midya, Bikashkali
2016-01-01
A planar waveguide with impedance boundary, composed of non-perfect metallic plates, and with passive or active dielectric filling is considered. We show the possibility of selective mode guiding and amplification when homogeneous pump is added to the dielectric, and analyze differences in TE and TM mode propagation. Such a non-conservative system is also shown to feature exceptional points, for specific and experimentally tunable parameters, which are described for a particular case of transparent dielectric.
Numerical evaluation of self and mutual earth return impedances
Denisa Stet; Dan D. Micu; Levente Czumbil; Emil Simion
2014-01-01
The paper presents an evaluation of analytical self and mutual impedances formulas of lines with earth return, taking into account the ground correction terms. The determined formulas contain semi-infinite integral terms which are calculated by a novel stable and efficient numerical integration scheme in order to overcome the involved oscillation problems. It might seek approximations of the semi-infinite integrals by replacing an exponential or algebraic function, the objective being to perm...
A general approach for calculating coupling impedances of small discontinuities
Kurennoy, S S; Stupakov, G V; Kurennoy, Sergey S; Gluckstern, Robert L; Stupakov, Gennady V
1995-01-01
A general theory of the beam interaction with small discontinuities of the vacuum chamber is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order, and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in a very natural way, the results for the trapped modes due to small discontinuities obtained earlier by a different method.
A General approach for calculating coupling impedances of small discontinuities
Kurennoy, Sergei S.; Gluckstern, Robert L.; Stupakov, Gennady V.
A general theory of the beam interaction with small discontinuities of the vacuum chamber is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order, and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in a very natural way, the results for the trapped modes due to small discontinuities obtained earlier by a different method.
"Paradoxical" reduction in postexercise ejection time and increased transthoracic impedance.
Nakamura, Y; Kotilainen, P; Haffty, B; Jolda, R; Bishop, R; Spodick, D
1978-12-01
Despite decreasing heart rate, left ventricular ejection time (LVET) transiently falls immediately following bicycle exercise. In seven normal, untrained subjects LVET decreases at 15 s postexercise corresponded (r = 0.78) with an increase in transthoracic electrical impedance (Z) consistent with decreased venous return to the thorax. Because the determinants of LVET are stroke volume (SV) and ejection rate, the deltaZ implies that decreased SV contributed to the "paradoxical" fall in LVET.
Low Power Implantable ASIC forBio-Impedance Measurements
Hussain Waqar, Muhammad
2012-01-01
Electrical bio-impedance can give a lot of insight into the basic physiological parameters of human body and concentration of glucose is one of those vital parameters.In order to control diabetes mellitus, it is critically essential to maintain blood glucose concentrations within the normal physiological range to avoid diabetes related complications.Consequently, accurate in-vivo and in-vitro measurement of glucose concentration in physiological uids has long been a central goal of bio sensor...
The Impedance of the Ceramic Chamber in J-PARC
Shobuda, Yoshihiro; Ohmi, Kazuhito; Toyama, Takeshi
2005-01-01
The ceramic chamber is adopted at the RCS (rapid cycling synchrotron) in J-PARC. The copper stripes are on the outer surface of the chamber in order to shield the electro-magnetic field produced by the beam. The inner surface of the chamber is coated by TiN to suppress the secondary electron emission. In this paper, we calculate the strength of electro-magnetic field produced by the beam and evaluate the impedance of this ceramic chamber.
Impedance matching through a single passive fractional element
Radwan, Ahmed Gomaa
2012-07-01
For the first time, a generalized admittance Smith chart theory is introduced to represent fractional order circuit elements. The principles of fractional order matching circuits are described. We show that for fractional order α < 1, a single parallel fractional element can match a wider range of load impedances as compared to its series counterpart. Several matching examples demonstrate the versatility of fractional order series and parallel element matching as compared to the conventional approach. © 2012 IEEE.
Impedance microflow cytometry for viability studies of microorganisms
Di Berardino, Marco; Hebeisen, Monika; Hessler, Thomas; Ziswiler, Adrian; Largiadèr, Stephanie; Schade, Grit
2011-02-01
Impedance-based Coulter counters and its derivatives are widely used cell analysis tools in many laboratories and use normally DC or low frequency AC to perform these electrical analyses. The emergence of micro-fabrication technologies in the last decade, however, provides a new means of measuring electrical properties of cells. Microfluidic approaches combined with impedance spectroscopy measurements in the radio frequency (RF) range increase sensitivity and information content and thus push single cell analyses beyond simple cell counting and sizing applications towards multiparametric cell characterization. Promising results have been shown already in the fields of cell differentiation and blood analysis. Here we emphasize the potential of this technology by presenting new data obtained from viability studies on microorganisms. Impedance measurements of several yeast and bacteria strains performed at frequencies around 10 MHz enable an easy discrimination between dead and viable cells. Moreover, cytotoxic effects of antibiotics and other reagents, as well as cell starvation can also be monitored easily. Control analyses performed with conventional flow cytometers using various fluorescent dyes (propidium iodide, oxonol) indicate a good correlation and further highlight the capability of this device. The label-free approach makes on the one hand the use of usually expensive fluorochromes obsolete, on the other hand practically eliminates laborious sample preparation procedures. Until now, online cell monitoring was limited to the determination of viable biomass, which provides rather poor information of a cell culture. Impedance microflow cytometry, besides other aspects, proposes a simple solution to these limitations and might become an important tool for bioprocess monitoring applications in the biotech industry.
Physically based Impedance Modelling of Lithium-Ion Cells
Illig, Jörg
2014-01-01
In this book, a new procedure to analyze lithium-ion cells is introduced. The cells are disassembled to analyze their components in experimental cell housings. Then, Electrochemical Impedance Spectroscopy, time domain measurements and the Distribution function of Relaxation Times are applied to obtain a deep understanding of the relevant loss processes. This procedure yields a notable surplus of information about the electrode contributions to the overall internal resistance of the cell.
Stepped Impedance Resonators for High Field Magnetic Resonance Imaging
Akgun, Can E.; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J.; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J. Thomas
2014-01-01
Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high field magnetic resonance imaging (MRI). In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) multi-element transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections referred to as step...
Studies on Electrical behavior of Glucose using Impedance Spectroscopy
Juansah, Jajang; Yulianti, Wina
2016-01-01
In this work we report the electrical characteristics of glucose at different frequencies. We show the correlation between electrical properties (impedance, reactance, resistance and conductance) of glucose and glucose concentration. Electrical property measurements on glucose solution were performed in order to formulate the correlation. The measurements were conducted for frequencies between 50 Hz and 1 MHz. From the measurements, we developed a single-pole Cole-Cole graph as a function of glucose concentration.
Voltammetric and impedance studies of inosine-5'-monophosphate and hypoxanthine
Oliveira-Brett, Ana Maria; Silva, Luís A.; Farace, Giosi; Vadgama, Pankaj; Christopher M. A. Brett
2003-01-01
The oxidation mechanism and adsorption of inosine 5'-monophosphate and hypoxanthine were investigated in solutions of different pH using voltammetric and impedance methods at glassy carbon electrodes. For both compounds, the pH dependence from differential pulse voltammetry showed that the same number of electrons and protons are involved in the rate-determining step of the electrochemical reaction. In the case of hypoxanthine, it was also possible to study the effect of different concentrati...
On second order shape optimization methods for electrical impedance tomography
Afraites, Lekbir; Dambrine, Marc; Kateb, Djalil
2007-01-01
This paper is devoted to the analysis of a second order method for recovering the \\emph{a priori} unknown shape of an inclusion $\\omega$ inside a body $\\Omega$ from boundary measurement. This inverse problem - known as electrical impedance tomography - has many important practical applications and hence has focussed much attention during the last years. However, to our best knowledge, no work has yet considered a second order approach for this problem. This paper aims to fill that void: we in...
Embedded silver PDMS electrodes for single cell electrical impedance spectroscopy
Wei, Yuan; Xu, Zhensong; Cachia, Mark A.; Nguyen, John; Zheng, Yi; Wang, Chen; Sun, Yu
2016-09-01
This paper presents a microfluidic device with wide channels and embedded AgPDMS electrodes for measuring the electrical properties of single cells. The work demonstrates the feasibility of using a large channel design and embedded electrodes for impedance spectroscopy to circumvent issues such as channel clogging and limited device re-usability. AgPDMS electrodes were formed on channel sidewalls for impedance detection and cell electrical properties measurement. Equivalent circuit models were used to interpret multi-frequency impedance data to quantify each cell’s cytoplasm conductivity and specific membrane capacitance. T24 cells were tested to validate the microfluidic system and modeling results. Comparisons were then made by measuring two leukemia cell lines (AML-2 and HL-60) which were found to have different cytoplasm conductivity values (0.29 ± 0.15 S m‑1 versus 0.47 ± 0.20 S m‑1) and specific membrane capacitance values (41 ± 25 mF m‑2 versus 55 ± 26 mF m‑2) when the cells were flown through the wide channel and measured by the AgPDMS electrodes.
Study of surfactant-skin interactions by skin impedance measurements.
Lu, Guojin; Moore, David J
2012-02-01
The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation. PMID:21923733
Vertical Dynamic Impedance of Tapered Pile considering Compacting Effect
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Wenbing Wu
2013-01-01
Full Text Available Based on complex stiffness transfer model, the vertical vibration of tapered pile embedded in layered soil is theoretically investigated by considering the compacting effect of the soil layer surrounding the tapered pile in the piling process. Allowing for the stratification of the surrounding soil and variable crosssection of the tapered pile, the pile-soil system is discretized into finite segments. By virtue of the complex stiffness transfer model to simulate the compacting effect, the complex stiffness of different soil segments surrounding the tapered pile is obtained. Then, substituting the complex stiffness into the vertical dynamic governing equation of tapered pile, the analytical solution of vertical dynamic impedance of tapered pile under vertical exciting force is derived by means of the Laplace technique and impedance function transfer method. Based on the presented solutions, the influence of compacting effect of surrounding soil on vertical dynamic impedance at the pile head is investigated within the low frequency range concerned in the design of dynamic foundation.
Time-domain fitting of battery electrochemical impedance models
Alavi, S. M. M.; Birkl, C. R.; Howey, D. A.
2015-08-01
Electrochemical impedance spectroscopy (EIS) is an effective technique for diagnosing the behaviour of electrochemical devices such as batteries and fuel cells, usually by fitting data to an equivalent circuit model (ECM). The common approach in the laboratory is to measure the impedance spectrum of a cell in the frequency domain using a single sine sweep signal, then fit the ECM parameters in the frequency domain. This paper focuses instead on estimation of the ECM parameters directly from time-domain data. This may be advantageous for parameter estimation in practical applications such as automotive systems including battery-powered vehicles, where the data may be heavily corrupted by noise. The proposed methodology is based on the simplified refined instrumental variable for continuous-time fractional systems method ('srivcf'), provided by the Crone toolbox [1,2], combined with gradient-based optimisation to estimate the order of the fractional term in the ECM. The approach was tested first on synthetic data and then on real data measured from a 26650 lithium-ion iron phosphate cell with low-cost equipment. The resulting Nyquist plots from the time-domain fitted models match the impedance spectrum closely (much more accurately than when a Randles model is assumed), and the fitted parameters as separately determined through a laboratory potentiostat with frequency domain fitting match to within 13%.
Optimal impedance on transmission of Lorentz force EMATs
Isla, Julio; Seher, Matthias; Challis, Richard; Cegla, Frederic
2016-02-01
Electromagnetic-acoustic transducers (EMATs) are attractive for non-destructive inspections because direct contact with the specimen under test is not required. This advantage comes at a high cost in sensitivity and therefore it is important to optimise every aspect of an EMAT. The signal strength produced by EMATs is in part determined by the coil impedance regardless of the transduction mechanism (e.g. Lorentz force, magnetostriction, etc.). There is very little literature on how to select the coil impedance that maximises the wave intensity; this paper addresses that gap. A transformer circuit is used to model the interaction between the EMAT coil and the eddy currents that are generated beneath the coil in the conducting specimen. Expressions for the coil impedances that satisfy the maximum efficiency and maximum power transfer conditions on transmission are presented. To support this analysis, a tunable coil that consists of stacked identical thin layers independently accessed is used so that the coil inductance can be modified while leaving the radiation pattern of the EMAT unaffected.
Embedded silver PDMS electrodes for single cell electrical impedance spectroscopy
Wei, Yuan; Xu, Zhensong; Cachia, Mark A.; Nguyen, John; Zheng, Yi; Wang, Chen; Sun, Yu
2016-09-01
This paper presents a microfluidic device with wide channels and embedded AgPDMS electrodes for measuring the electrical properties of single cells. The work demonstrates the feasibility of using a large channel design and embedded electrodes for impedance spectroscopy to circumvent issues such as channel clogging and limited device re-usability. AgPDMS electrodes were formed on channel sidewalls for impedance detection and cell electrical properties measurement. Equivalent circuit models were used to interpret multi-frequency impedance data to quantify each cell’s cytoplasm conductivity and specific membrane capacitance. T24 cells were tested to validate the microfluidic system and modeling results. Comparisons were then made by measuring two leukemia cell lines (AML-2 and HL-60) which were found to have different cytoplasm conductivity values (0.29 ± 0.15 S m-1 versus 0.47 ± 0.20 S m-1) and specific membrane capacitance values (41 ± 25 mF m-2 versus 55 ± 26 mF m-2) when the cells were flown through the wide channel and measured by the AgPDMS electrodes.
Enhanced modeling of magnetic impedance sensing system for damage detection
International Nuclear Information System (INIS)
There has been recent interest in utilizing the magneto-mechanical coupling characteristics of a magnetic transducer to perform impedance-based damage detection of electrically conductive structures. This approach is non-contact in nature and has potential advantages in many applications. One important parameter in this approach is the lift-off distance, i.e. the distance from the transducer to the structure monitored, the change of which changes the magneto-mechanical coupling. In the past, the magneto-mechanical coupling is extracted completely or partially from experiment in an ad hoc manner. A predictive capability of magneto-mechanical coupling under given lift-off distance would play a significant role in damage detection practice and in sensor design/optimization. In this research, we formulate detailed first-principles-based modeling of a magnetic impedance transducer. In particular, the complete electrical effect of the structure is explicitly taken into consideration. Comprehensive analyses and experiments are carried out, which validate the underlying hypothesis as well as the accuracy of the new model proposed for impedance response prediction. (paper)
Dielectric and impedance spectroscopic studies of neodymium gallate
Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T. P.
2016-05-01
The AC electrical properties of a polycrystalline neodymium gallate, NdGaO3 (NGO), synthesized by the sol-gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.
NEW BIOTESTING METHOD WITH THE APPLICATION OF MODERN IMPEDANCE TECHNOLOGIES
Directory of Open Access Journals (Sweden)
Sibirtsev V.S.
2015-03-01
Full Text Available The paper deals with new concepts of biotesting method updating. Modern conductometric technologies and the analysis of microbial «growth curves» are used. The registration occurs in a real time mode for the set of parallel samples. Results are shown for comparison of the proposed impedance biotesting technique with standard cultural determination method for total amount of microorganismes in the tested samples. Results are presented for practical application of the proposed impedance biotesting technique to the analysis as inhibitory action of clorhexidine disinfectant on the vital activity of Escherichia coli, as milk ripening process at the presence of various microorganisms species and protein preparations. The impedance biotesting method, proposed in the present work, provides high level of its own data convergence with the data, being received as a result of application of standard cultural biotesting techniques. Thus, the proposed method has such advantages, as: an opportunity of the detailed information reception about dynamics change of magnitude of population and intensity of test microorganisms metabolism, significant reduction of the culture media amount used, as well as researcher's temporary and labor efforts while the analyses realization, and the growth of analysis objectivity.
A comprehensive impedance journey to continuous microbial fuel cells.
Sevda, Surajbhan; Chayambuka, Kudakwashe; Sreekrishnan, T R; Pant, Deepak; Dominguez-Benetton, Xochitl
2015-12-01
The aim of the present work was to characterize the impedance response of an air-cathode MFC operating in a continuous mode and to determine intrinsic properties that define its performance which are crucial to be controlled for scalability purposes. The limiting step on electricity generation is the anodic electrochemically-active biofilm, independently of the external resistance, Rext, utilized. However, for Rext below 3 kΩ the internal impedance of the bioanode remained invariable, in good correspondence to the power density profile. The hydraulic retention time (HRT) had an effect on the impedance of both the bioanode and the air-cathode and especially on the overall MFC. The lowest HRT at which the MFC was operable was 3h. Yet, the variation on the HRT did not have a significant impact on power generation. A two constant phase element-model was associated with the EIS response of both bioanode and air-cathode, respectively. Consistency was found between the CPE behaviour and the normal power-law distribution of local resistivity with a uniform dielectric constant, which represented consistent values with the electrical double layer, the Nernst diffusion layer and presumably the biofilm thickness. These results have future implications on MFC monitoring and control, as well as in providing critical parameters for scale-up. PMID:25921205
Study of surfactant-skin interactions by skin impedance measurements.
Lu, Guojin; Moore, David J
2012-02-01
The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation.
Portable audio electronics for impedance-based measurements in microfluidics
International Nuclear Information System (INIS)
We demonstrate the use of audio electronics-based signals to perform on-chip electrochemical measurements. Cell phones and portable music players are examples of consumer electronics that are easily operated and are ubiquitous worldwide. Audio output (play) and input (record) signals are voltage based and contain frequency and amplitude information. A cell phone, laptop soundcard and two compact audio players are compared with respect to frequency response; the laptop soundcard provides the most uniform frequency response, while the cell phone performance is found to be insufficient. The audio signals in the common portable music players and laptop soundcard operate in the range of 20 Hz to 20 kHz and are found to be applicable, as voltage input and output signals, to impedance-based electrochemical measurements in microfluidic systems. Validated impedance-based measurements of concentration (0.1–50 mM), flow rate (2–120 µL min−1) and particle detection (32 µm diameter) are demonstrated. The prevailing, lossless, wave audio file format is found to be suitable for data transmission to and from external sources, such as a centralized lab, and the cost of all hardware (in addition to audio devices) is ∼10 USD. The utility demonstrated here, in combination with the ubiquitous nature of portable audio electronics, presents new opportunities for impedance-based measurements in portable microfluidic systems. (technical note)
Design and Analysis of Impedance Pumps Utilizing Electromagnetic Actuation
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Yu-Hisang Wang
2010-04-01
Full Text Available This study designs and analyzes an impedance pump utilizing an electromagnetic actuator. The pump is designed to have three major components, namely a lower glass substrate patterned with a copper micro-coil, a microchannel, and an upper glass cover plate attached a magnetic PDMS diaphragm. When a current is passed through the micro-coil, an electromagnetic force is established between the coil and the magnetic diaphragm. The resulting deflection of the PDMS diaphragm creates an acoustic impedance mismatch within the microchannel, which results in a net flow. In performing the analysis, simulated models of the magnetic field, the diaphragm displacement and the flow rate are developed using Ansoft/Maxwell3D, ANSYS FEA and FLUENT 6.3 CFD software, respectively. Overall, the simulated results reveal that a net flow rate of 52.8 μL/min can be obtained using a diaphragm displacement of 31.5 μm induced by a micro-coil input current of 0.5 A. The impedance pump proposed in this study provides a valuable contribution to the ongoing development of Lab-on-Chips (LoCs systems.
Application of impedance measurement techniques to accelerating cavity mode characterization
Hanna, S. M.; Stefan, P. M.
1993-11-01
Impedance measurements, using a central wire to simulate the electron beam, were performed on a 52 MHz accelerating cavity at the National Synchrotron Light Source (NSLS). This cavity was recently installed in the X-ray storage ring at the NSLS as a part of an upgrade of the ring. To damp higher-order modes (HOM) in this cavity, damping antennas have been installed. We implemented the impedance measurement technique to characterize the cavity modes up to 1 GHz and confirm the effectiveness of the damping antennas. Scattering parameters were measured using a network analyzer (HP 8510B) with a personal computer as a controller. Analysis based on S and T parameters for the system was used to solve for the cavity impedance, Z( ω), as a function of the measured transmission response, S21( ω). Search techniques were used to find the shunt resistance Rsh, and Q from the calculated Z( ω) for different modes. Our results for {R}/{Q} showed good agreement with URMEL simulations. The values of Q were compared with other independent Q measurement techniques. Our analytical technique offers an alternative approach for cases where full thru-reflection-line (TRL) calibration is not feasible and a more time-effective technique for obtaining {R}/{Q}, compared with the bead-pull method.
Electrochemical Impedance Spectroscopy to Characterize Inflammatory Atherosclerotic Plaques
Yu, Fei; Dai, Xiaohu; Beebe, Tyler; Hsiai, Tzung
2011-01-01
Despite advances in diagnosis and therapy, atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality in the Western world. Predicting metabolically active atherosclerotic lesions has remained an unmet clinical need. We hereby developed an electrochemical strategy to characterize the inflammatory states of high-risk atherosclerotic plaques. Using the concentric bipolar microelectrodes, we sought to demonstrate distinct Electrochemical Impedance Spectroscopic (EIS) measurements for unstable atherosclerotic plaques that harbored active lipids and inflammatory cells. Using equivalent circuits to simulate vessel impedance at the electrode-endoluminal tissue interface, we demonstrated specific electric elements to model working and counter electrode interfaces as well as the tissue impedance. Using explants of human coronary, carotid, and femoral arteries at various Stary stages of atherosclerotic lesions (n = 15), we performed endoluminal EIS measurements (n = 147) and validated with histology and immunohistochemistry. We computed the vascular tissue resistance using the equivalent circuit model and normalized the resistance to the lesion-free regions. Tissue resistance was significantly elevated in the oxLDL-rich thin-cap atheromas (1.57±0.40, n = 14, p 0.05). Hence, we demonstrate that the application of EIS strategy was sensitive to detect fibrous cap oxLDL-rich lesions and specific to distinguish oxLDL-absent fibroatheroma. PMID:21959227
Electrochemical impedance analysis of SOFC cathode reaction using evolutionary programming
Energy Technology Data Exchange (ETDEWEB)
Hershkovitz, S.; Baltianski, S.; Tsur, Y. [Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa (Israel)
2012-02-15
Investigation of the cathode reaction in solid oxide fuel cells (SOFC) by impedance spectroscopy (IS) measurements using evolutionary-based programming analysis is demonstrated. In contrast to the conventional analysis methods used for impedance spectroscopy measurements, e.g., equivalent circuits, the impedance spectroscopy genetic programming (ISGP) program seeks for a distribution of relaxation times that has the form of a peak or a sum of several peaks, assuming the Debye kernel. Using this method one finds a functional (parametric) form of the distribution of relaxation times. A symmetric cell configuration of Pt vertical stroke LSCF vertical stroke GDC vertical stroke LSCF vertical stroke Pt was examined using IS measurements combined with I-V measurements. Different samples at different temperatures and different oxygen partial pressures were examined in order to investigate their influence on the oxygen reduction reaction. The resulting IS data was analyzed using the ISGP program and the resulting peaks constructing the distribution of relaxation times were assigned for the different processes that occur at the cathode side. The activation energies as well as the dependence of the processes on the oxygen partial pressure were also evaluated. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Directory of Open Access Journals (Sweden)
Elin Ericsson
Full Text Available Ventilator-induced or ventilator-associated lung injury (VILI/VALI is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion.
Bera, Tushar Kanti
2016-03-18
Abstract: Electrical impedance tomography (EIT) phantoms are essential for the calibration, comparison and evaluation of the EIT systems. In EIT, the practical phantoms are typically developed based on inhomogeneities surrounded by a homogeneous background to simulate a suitable conductivity contrast. In multifrequency EIT (Mf-EIT) evaluation, the phantoms must be developed with the materials which have recognizable or distinguishable impedance variations over a wide range of frequencies. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity are analyzed. A number of practical phantoms with different tissue inhomogeneities and different inhomogeneity configurations are developed and the multifrequency impedance imaging is studied with the Mf-EIT system to evaluate the phantoms. The conductivity of the vegetable inhomogeneities reconstructed from the EIT imaging is compared with the conductivity values obtained from the EIS studies. Experimental results obtained from multifrequency EIT reconstruction demonstrate that the electrical impedance of all the biological tissues inhomogenity decreases with frequency. The potato tissue phantom produces better impedance image in high frequency ranges compared to the cucumber phantom, because the cucumber impedance at high frequency becomes lesser than that of the potato at the same frequency range. Graphical Abstract: [Figure not available: see fulltext.] © 2016 The Visualization Society of Japan
Ericsson, Elin; Tesselaar, Erik; Sjöberg, Folke
2016-01-01
Ventilator-induced or ventilator-associated lung injury (VILI/VALI) is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT) can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion. PMID:27253433
Timmer, B.; Sluyters-Rehbach, M.; Sluyters, J.H.
1967-01-01
The electrode impedance in the case of specific adsorption of the electroactive species is discussed, critically applying the charge separation model of Delahay. Comparison with experiments performed with the In3+/In(Hg) couple in 1 M KCNS, comprising impedance, chronopotentiometric and surface-tens
High Dynamic Range Complex Impedance Measurement System for Petrophysical Usage
Chen, R.; He, X.; Yao, H.; Tan, S.; Shi, H.; Shen, R.; Yan, C.; Zeng, P.; He, L.; Qiao, N.; Xi, F.; Zhang, H.; Xie, J.
2015-12-01
Spectral induced polarization method (SIP) or complex resistivity method is increasing its application in metalliferous ore exploration, hydrocarbon exploration, underground water exploration, monitoring of environment pollution, and the evaluation of environment remediation. And the measurement of complex resistivity or complex impedance of rock/ore sample and polluted water plays a fundamental role in improving the application effect of SIP and the application scope of SIP. However, current instruments can't guaranty the accuracy of measurement when the resistance of sample is less than 10Ω or great than 100kΩ. A lot of samples, such as liquid, polluted sea water, igneous rock, limestone, and sandstone, can't be measured with reliable complex resistivity result. Therefore, this problem projects a shadow in the basic research and application research of SIP. We design a high precision measurement system from the study of measurement principle, sample holder, and measurement instrument. We design input buffers in a single board. We adopt operation amplifier AD549 in this system because of its ultra-high input impedance and ultra-low current noise. This buffer is good in acquiring potential signal across high impedance sample. By analyzing the sources of measurement error and errors generated by the measurement system, we propose a correction method to remove the error in order to achieve high quality complex impedance measurement for rock and ore samples. This measurement system can improve the measurement range of the complex impedance to 0.1 Ω ~ 10 GΩ with amplitude error less than 0.1% and phase error less than 0.1mrad when frequency ranges as 0.01 Hz ~ 1 kHz. We tested our system on resistors with resistance as 0.1Ω ~ 10 GΩ in frequency range as 1 Hz ~ 1000 Hz, and the measurement error is less than 0.1 mrad. We also compared the result with LCR bridge and SCIP, we can find that the bridge's measuring range only reaches 100 MΩ, SCIP's measuring range
Optimal multisine excitation design for broadband electrical impedance spectroscopy
International Nuclear Information System (INIS)
Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer–Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements
Optimal multisine excitation design for broadband electrical impedance spectroscopy
Sanchez, B.; Vandersteen, G.; Bragos, R.; Schoukens, J.
2011-11-01
Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer-Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements when
Wang, Jing
2015-01-01
Electrical bioimpedance measurement is widely used today for monitoring body condition. The applications include and go beyond, body composition assessment, nutritional status evaluation, and cancer detection. The modalities for interpreting the impedance information have also developed quickly over the recent decades from single frequency bioimpedance analysis to spectrum and to images. Bioimpedance is measured by computing the relationship between voltage and current. In a current based bio...
Güren, Onan; Çayören, Mehmet; Tükenmez Ergene, Lale; Akduman, Ibrahim
2014-10-01
A new microwave imaging method that uses microwave contrast agents is presented for the detection and localization of breast tumours. The method is based on the reconstruction of breast surface impedance through a measured scattered field. The surface impedance modelling allows for representing the electrical properties of the breasts in terms of impedance boundary conditions, which enable us to map the inner structure of the breasts into surface impedance functions. Later a simple quantitative method is proposed to screen breasts against malignant tumours where the detection procedure is based on weighted cross correlations among impedance functions. Numerical results demonstrate that the method is capable of detecting small malignancies and provides reasonable localization.
Güren, Onan; Çayören, Mehmet; Ergene, Lale Tükenmez; Akduman, Ibrahim
2014-10-01
A new microwave imaging method that uses microwave contrast agents is presented for the detection and localization of breast tumours. The method is based on the reconstruction of breast surface impedance through a measured scattered field. The surface impedance modelling allows for representing the electrical properties of the breasts in terms of impedance boundary conditions, which enable us to map the inner structure of the breasts into surface impedance functions. Later a simple quantitative method is proposed to screen breasts against malignant tumours where the detection procedure is based on weighted cross correlations among impedance functions. Numerical results demonstrate that the method is capable of detecting small malignancies and provides reasonable localization.
Evaluation of different methods for measuring the impedance of Lithium-ion batteries during ageing
DEFF Research Database (Denmark)
Stroe, Daniel Loan; Swierczynski, Maciej Jozef; Stroe, Ana-Irina;
2015-01-01
are presented for measuring the impedance of Lithium-ion batteries and electrochemical impedance spectroscopy and dc current pulses are the most used ones; each of these approaches has its own advantages and drawbacks. The goal of this paper is to investigate which of the most encountered impedance measurement......The impedance represents one of the most important performance parameters of the Lithium-ion batteries since it used for power capability calculations, battery pack and system design, cooling system design and also for state-of-health estimation. In the literature, different approaches...... approaches is the most suitable for measuring the impedance of Lithium-ion batteries during ageing....
A study on the multi-freedom broadband impedance model for time-domain simulations
Institute of Scientific and Technical Information of China (English)
LI Xiaodong; LI Xiaoyan
2012-01-01
The purpose of this paper is to construct a general broadband impedance model, which is suited for predicting acoustic propagation problems in time domain. A multi-freedom broadband impedance model for sound propagation over impedance surfaces is proposed and the corresponding time domain impedance boundary condition is presented. Basing on the extended Helmholtz resonator, the multi-freedom impedance model is constructed through combing with a sum of rational functions in the form of general complex-conjugate pole-residue pairs and it is proved that the impedance model is well posed. The impedance boundary condition can be implemented into a computational aeroacoustics solver by a rectlrsive convolution technique, which results in a fast and computationally efficient algorithm. The two dimensional and three dimensional benchmark problems are selected to validate the accuracy of the proposed impedance model and time domain simulations. The numerical results are in good agreement with the reference solutions. It is demonstrated that the proposed impedance model can be used to describe the broadband characteristics of acoustic liners, and the corresponding time domain impedance boundary condition is viable and accurate for the prediction of sound propagation over broadband impedance surfaces.
Characterization of electro-acoustics impedance and its application to active noise control
Institute of Scientific and Technical Information of China (English)
HOU Hong; YANG Jianhua
2004-01-01
Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to Active Noise Control is demonstrated through a coil driven loudspeaker. A general formula of radiation impedance is derived for two control strategies, according to the criterion of total acoustic power output. The radiation impedances of some commonly used sound sources are calculated. We discuss in detail the relation between variation of the input electrical impedance and radiation impedance for the two control strategies. The measured data of the input electrical impedance from a loudspeaker agree fairly well with theoretical analysis. An AC- bridge circuit is designed in order to measure the weak variation of electrical impedance resulted from radiation impedance. The bridge relative output is unique for a certain control strategy, from which an impedance-based error criterion is then proposed and the implementation of its application to an active control system is analyzed.Numerical results of such criterion are presented. An analogue control system is set up and experiments are carried out in a semi-anechoic chamber to verify the new control approach.
Time and frequency dependence of disposable ECG electrode-skin impedance.
Olson, W H; Schmincke, D R; Henley, B L
1979-01-01
The magnitude and phase of disposable electrode-skin impedance were studied as functions of time, 0-48 hours, and frequency, 1 Hz-1 kHz. For both unabraded and mildly abraded skin, the impedance decreased as a function of time steadily or exponentially with time constants of several hours. Impedance decreased as a function of frequency by factors of 2 to 20 with greatest change at low frequencies. For heavily abraded skin, the impedance decreased slightly and then increased as a function of time especially at low frequencies. Impedance imbalance between pairs of identical electrodes applied in a like manner to the forearm were often greater than k omega, nearly equal to individual electrode-skin impedances, and decreased with time. Electrode impedance imbalance is particularly important because it affects noise levels in ECG recordings.
Directory of Open Access Journals (Sweden)
Yangkyu Park
2016-01-01
Full Text Available Purpose. To distinguish between normal (SV-HUC-1 and cancerous (TCCSUP human urothelial cell lines using microelectrical impedance spectroscopy (μEIS. Materials and Methods. Two types of μEIS devices were designed and used in combination to measure the impedance of SV-HUC-1 and TCCSUP cells flowing through the channels of the devices. The first device (μEIS-OF was designed to determine the optimal frequency at which the impedance of two cell lines is most distinguishable. The μEIS-OF trapped the flowing cells and measured their impedance at a frequency ranging from 5 kHz to 1 MHz. The second device (μEIS-RT was designed for real-time impedance measurement of the cells at the optimal frequency. The impedance was measured instantaneously as the cells passed the sensing electrodes of μEIS-RT. Results. The optimal frequency, which maximized the average difference of the amplitude and phase angle between the two cell lines (p<0.001, was determined to be 119 kHz. The real-time impedance of the cell lines was measured at 119 kHz; the two cell lines differed significantly in terms of amplitude and phase angle (p<0.001. Conclusion. The μEIS-RT can discriminate SV-HUC-1 and TCCSUP cells by measuring the impedance at the optimal frequency determined by the μEIS-OF.
Park, Yangkyu; Kim, Hyeon Woo; Yun, Joho; Seo, Seungwan; Park, Chang-Ju; Lee, Jeong Zoo; Lee, Jong-Hyun
2016-01-01
Purpose. To distinguish between normal (SV-HUC-1) and cancerous (TCCSUP) human urothelial cell lines using microelectrical impedance spectroscopy (μEIS). Materials and Methods. Two types of μEIS devices were designed and used in combination to measure the impedance of SV-HUC-1 and TCCSUP cells flowing through the channels of the devices. The first device (μEIS-OF) was designed to determine the optimal frequency at which the impedance of two cell lines is most distinguishable. The μEIS-OF trapped the flowing cells and measured their impedance at a frequency ranging from 5 kHz to 1 MHz. The second device (μEIS-RT) was designed for real-time impedance measurement of the cells at the optimal frequency. The impedance was measured instantaneously as the cells passed the sensing electrodes of μEIS-RT. Results. The optimal frequency, which maximized the average difference of the amplitude and phase angle between the two cell lines (p < 0.001), was determined to be 119 kHz. The real-time impedance of the cell lines was measured at 119 kHz; the two cell lines differed significantly in terms of amplitude and phase angle (p < 0.001). Conclusion. The μEIS-RT can discriminate SV-HUC-1 and TCCSUP cells by measuring the impedance at the optimal frequency determined by the μEIS-OF. PMID:26998490
Fully Parallel Electrical Impedance Tomography Using Code Division Multiplexing.
Tšoeu, M S; Inggs, M R
2016-06-01
Electrical Impedance Tomography (EIT) has been dominated by the use of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM) as methods of achieving orthogonal injection of excitation signals. Code Division Multiplexing (CDM), presented in this paper is an alternative that eliminates temporal data inconsistencies of TDM for fast changing systems. Furthermore, this approach eliminates data inconsistencies that arise in FDM when frequency bands of current injecting electrodes are chosen over frequencies that have large changes in the imaged object's impedance. To the authors knowledge no fully functional wideband system or simulation platform using simultaneous injection of Gold codes currents has been reported. In this paper, we formulate, simulate and develop a fully functional pseudo-random (Gold) code driven EIT system with 15 excitation currents and 16 separate voltage measurement electrodes. In the work we verify the use of CDM as a multiplexing modality in simultaneous injection EIT, using a prototype system with an overall bandwidth of 15 kHz, and attainable speed of 462 frames/s using codes with a period of 31 chips. Simulations and experiments are performed using the Electrical Impedance and Diffuse Optics Reconstruction Software (EIDORS). We also propose the use of image processing on reconstructed images to establish their quality quantitatively without access to raw reconstruction data. The results of this study show that CDM can be successfully used in EIT, and gives results of similar visual quality to TDM and FDM. Achieved performance shows average position error of 3.5% and size error of 6.2%. PMID:26731774
Effect of borehole design on electrical impedance tomography measurements
Mozaffari, Amirpasha; Huisman, Johan Alexander; Treichel, Andrea; Zimmermann, Egon; Kelter, Matthias; Vereecken, Harry
2015-04-01
Electrical Impedance Tomography (EIT) is a sophisticated non-invasive tool to investigate the subsurface in engineering and environmental studies. To increase the depth of investigation, EIT measurements can be made in boreholes. However, the presence of the borehole may affect EIT measurements. Here, we aim to investigate the effect of different borehole components on EIT measurements using 2,5-D and 3D finite element modeling and unstructured meshes. To investigate the effect of different borehole components on EIT measurements, a variety of scenarios were designed. In particular, the effect of the water-filled borehole, the PVC casing, and the gravel filter were investigated relative to complex resistivity simulations for a homogenous medium with chain and electrode modules. It was found that the results of the complex resistivity simulations were best understood using the sensitivity distribution of the electrode configuration under consideration. In all simulations, the sensitivity in the vicinity of the borehole was predominantly negative. Therefore, the introduction of the water-filled borehole caused an increase in the real part of the impedance, and a decrease (more negative) in the imaginary part of the simulated impedance. The PVC casing mostly enhanced the effect of the water-filled borehole described above, although this effect was less clear for some electrode configuration. The effect of the gravel filter mostly reduced the effect of the water-filled borehole with PVC casing. For EIT measurements in a single borehole, the highest simulated phase error was 12% for a Wenner configuration with electrode spacing of 0.33 m. This error decreased with increasing electrode spacing. In the case of cross-well configurations, the error in the phase shit was as high as 6%. Here, it was found that the highest errors occur when both current electrodes are located in the same borehole. These results indicated that cross-well measurements are less affected by the
A phase field model of electrochemical impedance spectroscopy
Gathright, William
One of the fundamental tenets of Material Science is the link between microstructure and material properties. As such, there is a need for a microstructure-sensitive model of electrochemistry. Phase field models have been designed to simulate systems with complex and evolving microstructures such as eutectic solidification and dendrite growth. The goal of this work is to extend phase field models into electrochemistry: with a chemical reaction model and a method of simulating electro-chemical impedance spectroscopy (EIS). The model given in the present work also forms the foundation for a microstructure-sensitive model of electrochemistry. EIS is a widely-used and powerful diagnostic technique in which the frequency-dependant impedance is measured. Though popular, data from EIS can be notoriously difficult to interpret. The present work also presents simulated EIS data, as well as explanations into the origins of common Nyquist plot features. At high-frequency, an analytic expression for the resistances is derived by analogy to Ohm's law. At low-frequency, the value for the resistance can be predicted by a simulated DC experiment. High- frequency capacitance originates in a difference in the current between the electrode and electrolyte. Low-frequency capacitance is defined by an “effective" surface charge, calculated by integrating the current over time rather than the charge density over distance. Depressed semicircle constant-phase element (CPE) behavior is also observed in the simulated data. Simulations with fast reaction kinetics exhibit power-law CPE impedance behavior, while simulations with a slow or no reaction are best explained by a combination of finite-length diffusion and electromigration. The model developed in this work is a tool to simulate, study, and interpret EIS data. Ultimately, it will serve as the foundation for a microstructure-sensitive model of electrochemistry.
Impedance Controller Tuned by Particle Swarm Optimization for Robotic Arms
Directory of Open Access Journals (Sweden)
Haifa Mehdi
2011-11-01
Full Text Available This paper presents an efficient and fast method for fine tuning the controller parameters of robot manipulators in constrained motion. The stability of the robotic system is proved using a Lyapunov‐based impedance approach whereas the optimal design of the controller parameters are tuned, in offline, by a Particle Swarm Optimization (PSO algorithm. For designing the PSOmethod,differentindexperformancesare considered in both joint and Cartesian spaces. A 3DOF manipulator constrained to a circular trajectory is finally used to validate the performances of the proposed approach. The simulation results show the stability and the performances of the proposed approach.
Impedance rheoplethysmography. The role of estimation of vasodilatory activity.
Demenge, P; Silice, C; Lebas, J F; Piquard, J F; Carraz, G
1979-01-01
The activity of a number of vasodilatory drugs was studied, with the help of impedance rheoplethysmography, on the vascular bed of the hind limb of anaesthetized rabbits. The vasodilators under study induce changes in rheoplethysmogram to a more or less important degree. The results were compared with those obtained with electromagnetic flowmetry. This method seems to be useful in the study of vasodilators because it allows to measure their effects and the duration thereof in a non-aggressive way. This method using flowmetry, allows to study in an analytical way those substances' effects on artery, vein and also capillary.
Chronic impedance spectroscopy of an endovascular stent-electrode array
Opie, Nicholas L.; John, Sam E.; Rind, Gil S.; Ronayne, Stephen M.; Grayden, David B.; Burkitt, Anthony N.; May, Clive N.; O’Brien, Terence J.; Oxley, Thomas J.
2016-08-01
Objective. Recently, we reported a minimally invasive stent-electrode array capable of recording neural signals from within a blood vessel. We now investigate the use of electrochemical impedance spectroscopy (EIS) measurements to infer changes occurring to the electrode–tissue interface from devices implanted in a cohort of sheep for up to 190 days. Approach. In a cohort of 15 sheep, endovascular stent-electrode arrays were implanted in the superior sagittal sinus overlying the motor cortex for up to 190 days. EIS was performed routinely to quantify viable electrodes for up to 91 days. An equivalent circuit model (ECM) was developed from the in vivo measurements to characterize the electrode–tissue interface changes occurring to the electrodes chronically implanted within a blood vessel. Post-mortem histological assessment of stent and electrode incorporation into the wall of the cortical vessels was compared to the electrical impedance measurements. Main results. EIS could be used to infer electrode viability and was consistent with x-ray analysis performed in vivo, and post-mortem evaluation. Viable electrodes exhibited consistent 1 kHz impedances across the 91 day measurement period, with the peak resistance frequency for the acquired data also stable over time. There was a significant change in 100 Hz phase angles, increasing from ‑67.8° ± 8.8° at day 0 to ‑43.8° ± 0.8° at day 91, which was observed to stabilize after eight days. ECM’s modeled to the data suggested this change was due to an increase in the capacitance of the electrode–tissue interface. This was supported by histological assessment with >85% of the implanted stent struts covered with neointima and incorporated into the blood vessel within two weeks. Conclusion. This work demonstrated that EIS could be used to determine the viability of electrode implanted chronically within a blood vessel. Impedance measurements alone were not observed to be a useful predictor of alterations
Optimization of Acoustic Pressure Measurements for Impedance Eduction
Jones, M. G.; Watson, W. R.; Nark, D. M.
2007-01-01
As noise constraints become increasingly stringent, there is continued emphasis on the development of improved acoustic liner concepts to reduce the amount of fan noise radiated to communities surrounding airports. As a result, multiple analytical prediction tools and experimental rigs have been developed by industry and academia to support liner evaluation. NASA Langley has also placed considerable effort in this area over the last three decades. More recently, a finite element code (Q3D) based on a quasi-3D implementation of the convected Helmholtz equation has been combined with measured data acquired in the Langley Grazing Incidence Tube (GIT) to reduce liner impedance in the presence of grazing flow. A new Curved Duct Test Rig (CDTR) has also been developed to allow evaluation of liners in the presence of grazing flow and controlled, higher-order modes, with straight and curved waveguides. Upgraded versions of each of these two test rigs are expected to begin operation by early 2008. The Grazing Flow Impedance Tube (GFIT) will replace the GIT, and additional capabilities will be incorporated into the CDTR. The current investigation uses the Q3D finite element code to evaluate some of the key capabilities of these two test rigs. First, the Q3D code is used to evaluate the microphone distribution designed for the GFIT. Liners ranging in length from 51 to 610 mm are investigated to determine whether acceptable impedance eduction can be achieved with microphones placed on the wall opposite the liner. This analysis indicates the best results are achieved for liner lengths of at least 203 mm. Next, the effects of moving this GFIT microphone array to the wall adjacent to the liner are evaluated, and acceptable results are achieved if the microphones are placed off the centerline. Finally, the code is used to investigate potential microphone placements in the CDTR rigid wall adjacent to the wall containing an acoustic liner, to determine if sufficient fidelity can be
Numerical evaluation of self and mutual earth return impedances
Directory of Open Access Journals (Sweden)
Denisa Stet
2014-12-01
Full Text Available The paper presents an evaluation of analytical self and mutual impedances formulas of lines with earth return, taking into account the ground correction terms. The determined formulas contain semi-infinite integral terms which are calculated by a novel stable and efficient numerical integration scheme in order to overcome the involved oscillation problems. It might seek approximations of the semi-infinite integrals by replacing an exponential or algebraic function, the objective being to permit analytic integration. Since there is no good systematic method for making these replacements, their success depends directly on the intuition and ingenuity, taking into account that in practice the integrand has limited accuracy.
Effective impedance for predicting the existence of surface states
Xiao, Meng; Huang, Xueqin; Fang, Anan; Chan, C. T.
2016-03-01
We build an effective impedance for two-dimensional (2D) photonic crystals (PCs) comprising a rectangular lattice of dielectric cylinders with the incident electric field polarized along the axis of the cylinders. In particular, we discuss the feasibility of constructing an effective impedance for the case where the Bloch wave vector is far away from the center of Brillouin zone, where the optical response of the PC is necessarily anisotropic, and hence the effective description becomes inevitably angle dependent. We employ the scattering theory and treat the 2D system as a stack of 1D arrays. We consider only the zero-order interlayer diffraction, and all the higher order diffraction terms of interlayer scattering are ignored. This approximation works well when the higher order diffraction terms are all evanescent waves and the interlayer distance is far enough for them to decay out. Scattering theory enables the calculation of transmission and reflection coefficients of a finite-sized slab, and we extract the effective parameters such as the effective impedance (Ze) and the effective refractive index (ne) using a parameter retrieval method. We note that ne is uniquely defined only in a very limited region of the reciprocal space. (nek0a ≪1 , where k0 is the wave vector inside the vacuum and a is thickness of the slab for retrieval), but Ze is uniquely defined and has a well-defined meaning inside a much larger domain in the reciprocal space. For a lossless system, the effective impedance Ze is purely real for the pass band and purely imaginary in the band gaps. Using the sign of the imaginary part of Ze, we can classify the band gaps into two groups, and this classification explains why there is usually no surface state on the boundary of typical fully gapped PCs composed of a lattice of dielectric cylinders. This effective medium approach also allows us to predict the dispersion of surface states even when the surface wave vectors are well beyond the zone
Chronic impedance spectroscopy of an endovascular stent-electrode array
Opie, Nicholas L.; John, Sam E.; Rind, Gil S.; Ronayne, Stephen M.; Grayden, David B.; Burkitt, Anthony N.; May, Clive N.; O'Brien, Terence J.; Oxley, Thomas J.
2016-08-01
Objective. Recently, we reported a minimally invasive stent-electrode array capable of recording neural signals from within a blood vessel. We now investigate the use of electrochemical impedance spectroscopy (EIS) measurements to infer changes occurring to the electrode-tissue interface from devices implanted in a cohort of sheep for up to 190 days. Approach. In a cohort of 15 sheep, endovascular stent-electrode arrays were implanted in the superior sagittal sinus overlying the motor cortex for up to 190 days. EIS was performed routinely to quantify viable electrodes for up to 91 days. An equivalent circuit model (ECM) was developed from the in vivo measurements to characterize the electrode-tissue interface changes occurring to the electrodes chronically implanted within a blood vessel. Post-mortem histological assessment of stent and electrode incorporation into the wall of the cortical vessels was compared to the electrical impedance measurements. Main results. EIS could be used to infer electrode viability and was consistent with x-ray analysis performed in vivo, and post-mortem evaluation. Viable electrodes exhibited consistent 1 kHz impedances across the 91 day measurement period, with the peak resistance frequency for the acquired data also stable over time. There was a significant change in 100 Hz phase angles, increasing from -67.8° ± 8.8° at day 0 to -43.8° ± 0.8° at day 91, which was observed to stabilize after eight days. ECM’s modeled to the data suggested this change was due to an increase in the capacitance of the electrode-tissue interface. This was supported by histological assessment with >85% of the implanted stent struts covered with neointima and incorporated into the blood vessel within two weeks. Conclusion. This work demonstrated that EIS could be used to determine the viability of electrode implanted chronically within a blood vessel. Impedance measurements alone were not observed to be a useful predictor of alterations occurring
The effect of vocal tract impedance on the vocal folds
DEFF Research Database (Denmark)
Agerkvist, Finn T.; Selamtzis, Andreas
2011-01-01
for the Neutral mode compared to the other, so-called metallic modes. The differences in waveform between Curbing, Overdrive and Edge modes are minor. However, the spectrum of the Overdrive mode shows stronger 2nd harmonic and weaker 4th and 6th harmonic compared to Curbing and Edge. Finally the Overdrive mode......, which is the mode that is most limited in pitch range, was tested at its pitch limit C5 (523 Hz) under normal conditions and when the singer has inhaled Helium. When inhaling Helium the acoustic impedance of the vocal tract is reduced in magnitude and the resonances are scaled upwards in frequency due...
Mechanical impedance measurement and damage detection using noncontact laser ultrasound.
Lee, Hyeonseok; Lim, Hyeong Uk; Hong, Jung-Wuk; Sohn, Hoon
2014-06-01
This Letter proposes a mechanical impedance (MI) measurement technique using noncontact laser ultrasound. The ultrasound is generated by shooting a pulse laser beam onto a target structure, and its response is measured using a laser vibrometer. Once ultrasound propagation converges to structural vibration, MI is formed over the entire structure. Because noncontact lasers are utilized, this technique is applicable in harsh environments, free of electromagnetic interference, and able to perform wide-range scanning. The formation of MI and its feasibility for damage detection are verified through thermo-mechanical finite element analysis and lab-scale experiments.
Does Dividend Tax Impede Competition for Corporate Charters?
DEFF Research Database (Denmark)
Lai, Tat-kei; Ng, Travis
High dividend income tax in the U.S. can impede state competition in the market for corporate charters. We offer a model to formalize the mechanism through which dividend tax lowers the incentives for a state legislator to refrain from enacting takeover regulations. We test a key driver within...... the model, that dividend tax exacerbates agency conﬂicts between management and shareholders, making takeover regulations less consequential to the corporations that have their shareholders subject to the tax. The implication, that under a dividend tax cut, ﬁrms governed by fewer anti-takeover provisions...
Ionic conductivity measurements of zirconia under pressure using impedance spectroscopy
Takebe, H; Ohtaka, O; Fukui, H; Yoshiasa, A; Yamanaka, T; Ota, K; Kikegawa, T
2002-01-01
We have set up an electrical conductivity measurement system under high-pressure and high-temperature conditions with a multi-anvil high-pressure apparatus using an AC complex impedance method. With this system, we have successfully measured the electrical conductivity of stabilized ZrO sub 2 (Y sub 2 O sub 3 -ZrO sub 2 solid solution) under pressures up to 5 GPa in the temperature range from 300 to 1200 K. The electrical conductivities obtained under pressure are compatible with those of previous results measured at ambient pressure.
Determination of time delay between ventricles contraction using impedance measurements
International Nuclear Information System (INIS)
The paper presents a novel approach to assessment of ventricular dyssynchrony basing on multichannel electrical impedance measurements. Using a proper placement of electrodes, the sensitivity approach allows estimating time difference between chambers contraction from over determined nonlinear system of equations. The theoretical considerations which include Finite Element Method simulations were verified using measurements on healthy 28 year's old woman. The nonlinear least squares method was applied to obtain a time difference between heart chambers contraction. The obtained value was in a good agreement with theoretical values found in literature.
RF impedance measurements of DC atmospheric micro-discharges
Overzet, Lawrence J; Mandra, Monali; Goeckner, Matthew; Dufour, Thierry; Dussart, Remi; Lefaucheux, Philippe
2016-01-01
The available diagnostics for atmospheric micro-plasmas remain limited and relatively complex to implement; so we present a radio-frequency technique for diagnosing a key parameter here. The technique allows one to estimate the dependencies of the electron density by measuring the RF-impedance of the micro-plasma and analyzing it with an appropriate equivalent circuit. This technique is inexpensive, can be used in real time and gives reasonable results for argon and helium DC micro-plasmas in holes over a wide pressure range. The electron density increases linearly with current in the expected range consistent with normal glow discharge behavior.
Axisymmetric fundamental solutions for a finite layer with impeded boundaries
Institute of Scientific and Technical Information of China (English)
程泽海; 陈云敏; 凌道盛; 唐晓武
2003-01-01
Axisymmetric fundamental solutions that are applied in the consolidation calculations of a finite clay layer with impeded boundaries were derived. Laplace and Hankel integral transforms were utilized with respect to time and radial coordinates, respectively in the analysis. The derivation of fundamental solutions considers two boundary-value problems involving unit point loading and ring loading in the vertical. The solutions are extended to circular distributed and strip distributed normal load. The computation and analysis of settlements, vertical total stress and excess pore pressure in the consolidation layer subject to circular loading are presented.
Axisymmetric fundamental solutions for a finite layer with impeded boundaries
Institute of Scientific and Technical Information of China (English)
程泽海; 陈云敏; 凌道盛; 唐晓武
2003-01-01
Axisymmetrie fundamental solutions that are applied in the consolidation calculations of a finite clay layer with impeded boundaries were derived. Laplace and Hankel integral transforms were utilized with respect to time and radial coordinates, respectively in the analysis. The derivation of fundamental solutions considers two boundary-value problems involving unit point loading and ring loading in the vertical. The solut-ions are extended to circular distributed and strip distributed normal load. The computation and analysis of set-tlements, vertical total stress and excess pore pressure in the consolidation layer subject to circular loading are presented.
Electrical impedance measured changes in thoracic fluid content during thoracentesis
DEFF Research Database (Denmark)
Petersen, J R; Jensen, B V; Drabaek, H;
1994-01-01
of each 500 ml, and at the end of the thoracentesis. We found a close linear correlation (r = 0.97) between changes in Z0 and the volume of aspirated pleural effusion (y = 0.415.x+0.093). The variability of the estimated thoracic fluid volumes was analysed with a plot of the residuals from the regression...... line, and we found that changes in thoracic fluid volume estimated by impedance technique would be within +/- 302 ml (= 2 SD). However, the absolute value of Z0 before thoracentesis could not differentiate the group of patients with pleural effusion from normal subjects (n = 28)....
Soil amplification with a strong impedance contrast: Boston, Massachusetts
Baise, Laurie G.; Kaklamanos, James; Berry, Bradford M; Thompson, Eric
2016-01-01
In this study, we evaluate the effect of strong sediment/bedrock impedance contrasts on soil amplification in Boston, Massachusetts, for typical sites along the Charles and Mystic Rivers. These sites can be characterized by artificial fill overlying marine sediments overlying glacial till and bedrock, where the depth to bedrock ranges from 20 to 80 m. The marine sediments generally consist of organic silts, sand, and Boston Blue Clay. We chose these sites because they represent typical foundation conditions in the city of Boston, and the soil conditions are similar to other high impedance contrast environments. The sediment/bedrock interface in this region results in an impedance ratio on the order of ten, which in turn results in a significant amplification of the ground motion. Using stratigraphic information derived from numerous boreholes across the region paired with geologic and geomorphologic constraints, we develop a depth-to-bedrock model for the greater Boston region. Using shear-wave velocity profiles from 30 locations, we develop average velocity profiles for sites mapped as artificial fill, glaciofluvial deposits, and bedrock. By pairing the depth-to-bedrock model with the surficial geology and the average shear-wave velocity profiles, we can predict soil amplification in Boston. We compare linear and equivalent-linear site response predictions for a soil layer of varying thickness over bedrock, and assess the effects of varying the bedrock shear-wave velocity (VSb) and quality factor (Q). In a moderate seismicity region like Boston, many earthquakes will result in ground motions that can be modeled with linear site response methods. We also assess the effect of bedrock depth on soil amplification for a generic soil profile in artificial fill, using both linear and equivalent-linear site response models. Finally, we assess the accuracy of the model results by comparing the predicted (linear site response) and observed site response at the Northeastern
Determination of time delay between ventricles contraction using impedance measurements
Lewandowska, M.; Poliński, A.; Wtorek, J.
2013-04-01
The paper presents a novel approach to assessment of ventricular dyssynchrony basing on multichannel electrical impedance measurements. Using a proper placement of electrodes, the sensitivity approach allows estimating time difference between chambers contraction from over determined nonlinear system of equations. The theoretical considerations which include Finite Element Method simulations were verified using measurements on healthy 28 year's old woman. The nonlinear least squares method was applied to obtain a time difference between heart chambers contraction. The obtained value was in a good agreement with theoretical values found in literature.
Anaemia impedes functional mobility after hip fracture surgery
DEFF Research Database (Denmark)
Foss, N.B.; Kristensen, M.T.; Kehlet, H.
2008-01-01
BACKGROUND: the impact of anaemia on the outcome after a hip fracture surgery is controversial, but anaemia can potentially decrease the physical performance and thereby impede post-operative rehabilitation. We therefore conducted a prospective study to establish whether anaemia affected functional...... was measured on each of the first three post-operative days, and anaemia defined as Hb ..., respectively. A significant association between anaemia and the ability to walk independently before the correction of anaemia was present on each of the 3 days separately (P
Spatially resolved voltage, current and electrochemical impedance spectroscopy measurements
Energy Technology Data Exchange (ETDEWEB)
Gerteisen, D.; Kurz, T.; Schwager, M.; Hebling, C. [Fraunhofer Institute for Solar Energy Systems ISE, Freiburg im Breisgau (Germany); Merida, W. [Clean Energy Research Centre, University of British Columbia, Vancouver, BC (Canada); Lupotto, P. [Materials Mates Italia, Milano (Italy)
2011-04-15
In this work a 50-channel characterisation system for PEMFCs is presented. The system is capable of traditional electrochemical measurements (e.g. staircase voltammetry, chronoamperometry and cyclic voltammetry), and concurrent EIS measurements. Unlike previous implementations, this system relies on dedicated potentiostats for current and voltage control, and independent frequency response analysers (FRAs) at each channel. Segmented fuel cell hardware is used to illustrate the system's flexibility and capabilities. The results here include steady-state data for cell characterisation under galvanostatic and potentiostatic control as well as spatially resolved impedance spectra. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
A MEMS-based valveless impedance pump utilizing electromagnetic actuation
International Nuclear Information System (INIS)
This study presents a planar valveless impedance-based micro pump for biomedical applications. The micro pump comprises four major components, namely a lower glass substrate containing a copper micro coil, a microchannel, an upper glass cover plate and a PDMS diaphragm with a magnet mounted on its upper surface. When a current is passed through the micro coil, an electromagnetic force is established between the coil and the magnet. The resulting deflection of the PDMS diaphragm creates an acoustic impedance mismatch within the microchannel, which results in a net flow. The performance of the micro pump is characterized both experimentally and numerically using Ansoft/Maxwell3D FEA software. The results show that the mechanical integrity of the micro pump is assured provided that the diaphragm deflection does not exceed 110 µm. This deflection is obtained by supplying the micro coil with an input current of 0.6 A, and results in a flow rate of 7.2 ml min−1 when the PDMS membrane is driven by an actuating frequency of 200 Hz
Electrical conduction in polycrystalline CVD diamond: Temperature dependent impedance measurements
Energy Technology Data Exchange (ETDEWEB)
Ye, H.; Williams, O.A.; Jackman, R.B. [Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Rudkin, R.; Atkinson, A. [Department of Materials, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom)
2002-10-16
In this paper, we report the first measurement of impedance on freestanding diamond films from 0.1 Hz to 10 MHz up to 300 C. A wide range of CVD materials have been investigated, but here we concentrate on 'black' diamond grown by MWPECVD. The Cole-Cole (Z' via Z{sup ''}) plots are well fitted to a RC parallel circuit model and the equivalent resistance and capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 62 M{omega} at room temperature to 4 k{omega} at 300 C, with an activation energy around 0.51 eV. The equivalent capacitance is maintained at the level of 10{sup 2} pF up to 300 C, suggesting that the diamond grain boundaries are dominating the conduction. At 400 C, the impedance at low frequencies shows a linear tail, which can be explained that the ac polarization of diamond/Au interface occurs. (Abstract Copyright [2002], Wiley Periodicals, Inc.)
A MEMS-based valveless impedance pump utilizing electromagnetic actuation
Lee, Chia-Yen; Chang, Hsien-Tsung; Wen, Chih-Yung
2008-03-01
This study presents a planar valveless impedance-based micro pump for biomedical applications. The micro pump comprises four major components, namely a lower glass substrate containing a copper micro coil, a microchannel, an upper glass cover plate and a PDMS diaphragm with a magnet mounted on its upper surface. When a current is passed through the micro coil, an electromagnetic force is established between the coil and the magnet. The resulting deflection of the PDMS diaphragm creates an acoustic impedance mismatch within the microchannel, which results in a net flow. The performance of the micro pump is characterized both experimentally and numerically using Ansoft/Maxwell3D FEA software. The results show that the mechanical integrity of the micro pump is assured provided that the diaphragm deflection does not exceed 110 µm. This deflection is obtained by supplying the micro coil with an input current of 0.6 A, and results in a flow rate of 7.2 ml min-1 when the PDMS membrane is driven by an actuating frequency of 200 Hz.
Determinants of pulmonary perfusion measured by electrical impedance tomography.
Smit, Henk J; Vonk Noordegraaf, Anton; Marcus, J Tim; Boonstra, Anco; de Vries, Peter M; Postmus, Pieter E
2004-06-01
Electrical impedance tomography (EIT) is a non-invasive imaging technique for detecting blood volume changes that can visualize pulmonary perfusion. The two studies reported here tested the hypothesis that the size of the pulmonary microvascular bed, rather than stroke volume (SV), determines the EIT signal. In the first study, the impedance changes relating to the maximal pulmonary pulsatile blood volume during systole (Delta Z(sys)) were measured in ten healthy subjects, ten patients diagnosed with chronic obstructive pulmonary disease, who were considered to have a reduced pulmonary vascular bed, and ten heart failure patients with an assumed low cardiac output but with a normal lung parenchyma. Mean Delta Z(sys) (SD) in these groups was 261 (34)x10(-5), 196 (39)x10(-5) ( Pbicycle while SV was measured by means of magnetic resonance imaging. The Delta Z(sys) at rest was 352 (53)x10(-5 ) and 345 (112)x10(-5 )AU during exercise (P=NS), whereas SV increased from 83 (21) to 105 (34) ml (P<0.05). The EIT signal likely reflects the size of the pulmonary microvascular bed, since neither a low cardiac output nor a change in SV of the heart appear to influence EIT.
Characterization of Physiological Glucose Concentration Using Electrical Impedance Spectroscopy
Directory of Open Access Journals (Sweden)
Quazi Delwar Hossain
2013-01-01
Full Text Available Non-invasive glucose monitoring is crucial for effective diabetes mellitus treatment while a sound correlation of a non-invasive parameter to glucose level variation is quite challenging. This paper presents characterization of glucose concentrations using Electrical Impedance Spectroscopy (EIS in three different solutions: 1 0.9% NaCl, 2 Saline (NaCl 1.3gm, KCl 0.75gm, Na3C6H5O7 1.45gm, D-glucose 6.75gm in 500mL and 3 Human Blood for every 25mg/dl change of glucose in total 150ml solution. A rectangular current pulse of 1.5s duration with 1mA peak is applied to the solutions and corresponding voltage is acquired across the solutions with Agilent InfiniiVision 7000B Series oscilloscope and Matlab R2011a Instrument Control Toolbox. The circuit proposed for current injection and voltage acquisition requires only two electrodes would reduce electrode polarization and skin irritation greatly which is a major concern in many previous works use generally four electrodes. Experimental results show sound correlation between EIS and blood glucose concentration. It is clearly found from the EIS that the DC impedance of solutions increases linearly with the increment in glucose concentrations.
Elliptic cylinder geometry for distinguishability analysis in impedance tomography.
Saka, Birsen; Yilmaz, Atila
2004-01-01
Electrical impedance tomography (EIT) is a technique that computes the cross-sectional impedance distribution within the body by using current and voltage measurements made on the body surface. It has been reported that the image reconstruction is distorted considerably when the boundary shape is considered to be more elliptical than circular as a more realistic shape for the measurement boundary. This paper describes an alternative framework for determining the distinguishability region with a finite measurement precision for different conductivity distributions in a body modeled by elliptic cylinder geometry. The distinguishable regions are compared in terms of modeling error for predefined inhomogeneities with elliptical and circular approaches for a noncircular measurement boundary at the body surface. Since most objects investigated by EIT are noncircular in shape, the analytical solution for the forward problem for the elliptical cross section approach is shown to be useful in order to reach a better assessment of the distinguishability region defined in a noncircular boundary. This paper is concentrated on centered elliptic inhomogeneity in the elliptical boundary and an analytic solution for this type of forward problem. The distinguishability performance of elliptical cross section with cosine injected current patterns is examined for different parameters of elliptical geometry. PMID:14723501
Impedance adaptation methods of the piezoelectric energy harvesting
Kim, Hyeoungwoo
In this study, the important issues of energy recovery were addressed and a comprehensive investigation was performed on harvesting electrical power from an ambient mechanical vibration source. Also discussed are the impedance matching methods used to increase the efficiency of energy transfer from the environment to the application. Initially, the mechanical impedance matching method was investigated to increase mechanical energy transferred to the transducer from the environment. This was done by reducing the mechanical impedance such as damping factor and energy reflection ratio. The vibration source and the transducer were modeled by a two-degree-of-freedom dynamic system with mass, spring constant, and damper. The transmissibility employed to show how much mechanical energy that was transferred in this system was affected by the damping ratio and the stiffness of elastic materials. The mechanical impedance of the system was described by electrical system using analogy between the two systems in order to simply the total mechanical impedance. Secondly, the transduction rate of mechanical energy to electrical energy was improved by using a PZT material which has a high figure of merit and a high electromechanical coupling factor for electrical power generation, and a piezoelectric transducer which has a high transduction rate was designed and fabricated. The high g material (g33 = 40 [10-3Vm/N]) was developed to improve the figure of merit of the PZT ceramics. The cymbal composite transducer has been found as a promising structure for piezoelectric energy harvesting under high force at cyclic conditions (10--200 Hz), because it has almost 40 times higher effective strain coefficient than PZT ceramics. The endcap of cymbal also enhances the endurance of the ceramic to sustain ac load along with stress amplification. In addition, a macro fiber composite (MFC) was employed as a strain component because of its flexibility and the high electromechanical coupling
An instrument for simultaneous EQCM impedance and SECM measurements.
Gollas, B; Bartlett, P N; Denuault, G
2000-01-15
A novel combination of an electrochemical quartz crystal microbalance (EQCM) and a scanning electrochemical microscope (SECM) has been built. Unlike conventional EQCMs, the instrument described here allows rapid in situ measurement of the modulus of the quartz crystal's transfer function. Data analysis in the complex plane for the Butterworth-Van Dyke (BVD) equivalent circuit yields the real and the imaginary components R (damping resistance) and XL (reactive inductance) of the crystal's electroacoustic impedance around its resonant frequency of 10 MHz. The influence of different tip shapes of an approaching microelectrode on the electroacoustic impedance of the quartz crystal was studied and found to be minimal for certain geometries. The capability of the EQCM/SECM instrument was tested in cyclic voltammetric plating/stripping experiments using a copper(I) chloride solution of high concentration in 1 M HCl. Four parameters, XL, R, the substrate, and the tip current, can be recorded simultaneously. Depletion layer effects were observed and could be corrected for to yield accurate current efficiencies for potentiodynamic and potentiostatic copper plating. The amperometric response of the SECM tip positioned closely to the substrate reflects the concentration changes of electroactive ions in the diffusion layer of the substrate electrode. PMID:10658330
Simplified signal processing for impedance spectroscopy with spectrally sparse sequences
International Nuclear Information System (INIS)
Classical method for measurement of the electrical bio-impedance involves excitation with sinusoidal waveform. Sinusoidal excitation at fixed frequency points enables wide variety of signal processing options, most general of them being Fourier transform. Multiplication with two quadrature waveforms at desired frequency could be easily accomplished both in analogue and in digital domains, even simplest quadrature square waves can be considered, which reduces signal processing task in analogue domain to synchronous switching followed by low pass filter, and in digital domain requires only additions. So called spectrally sparse excitation sequences (SSS), which have been recently introduced into bio-impedance measurement domain, are very reasonable choice when simultaneous multifrequency excitation is required. They have many good properties, such as ease of generation and good crest factor compared to similar multisinusoids. Typically, the usage of discrete or fast Fourier transform in signal processing step is considered so far. Usage of simplified methods nevertheless would reduce computational burden, and enable simpler, less costly and less energy hungry signal processing platforms. Accuracy of the measurement with SSS excitation when using different waveforms for quadrature demodulation will be compared in order to evaluate the feasibility of the simplified signal processing. Sigma delta modulated sinusoid (binary signal) is considered to be a good alternative for a synchronous demodulation.
Biomass measurement of living Lumbriculus variegatus with impedance spectroscopy
Directory of Open Access Journals (Sweden)
Martina Sammer
2014-12-01
Full Text Available Impedance spectroscopy is a useful tool for non-invasive and real time measurements of cell suspensions and a variety of biological tissues. The objective of this study was the investigation of the dielectric properties of living aquatic worms (Lumbriculus variegatus using impedance spectroscopy in a frequency range between 100 Hz and 10 MHz. We demonstrate a linear relation between the worm biomass and the phase response of the signal thereby providing a quick and precise method to determine the biomass of aquatic worms in situ. Possible applications for non-destructive online biomass monitoring of aquatic worms and other aqueous organisms are discussed. Furthermore, we show that groups of worms fed different diets can be distinguished by the method presented. These results reveal a close relationship between the nutritional composition of the worms and the measured phase response. We also demonstrate that the phase response at 90 kHz does not depend on the worm size. In contrast, the response function for the signal at 440 Hz reveals a linear correlation of average individual worm size and phase. Therefore, we conclude that the measured phase response at 90 kHz qualifies as a measure of the total amount of worm biomass present in the measuring cell, whereas the phase measurement at 440 Hz can be used to estimate the average individual worm size.
SVM for prostate cancer using electrical impedance measurements
International Nuclear Information System (INIS)
Biopsies are currently the 'gold standard' method for identifying cancer of the prostate. While biopsies yield very accurate information regarding the area they sample, they are performed at discrete points and provide no information on the adjacent tissue. To enhance procedural accuracy, biopsies of a large number of sites are routinely carried out. Although more accurate, this method is both more complex and nevertheless remains discrete. In this paper, we evaluate the advantages of using bio-impedance information as the input for a support vector machines (SVMs) classifier to overcome these limitations. In this method, the biopsy probes are used as electrodes to obtain electrical impedance data during each biopsy sample. Using a computer model of the prostate, a SVM was trained and tested. Different tumor shapes and conductivity values, and the classifier's ability to generalize to these different properties, were examined. We demonstrate that by using this classifier the number of biopsies can be reduced and valuable information concerning the adjacent tissue which was not biopsied can be generated
Studies of deionization and impedance spectroscopy for blood analyzer
Kwong, Charlotte C.; Li, Nan; Ho, Chih-Ming
2005-11-01
Blood analysis provides vital information for health conditions. For instance, typical infection response is correlated to an elevated White Blood Cell (WBC) count, while low Red Blood Cell (RBC) count, hemoglobin and hematocrit are caused by anemia or internal bleeding. We are developing two essential modules, deionization (DI) chip and microfluidic cytometer with impedance spectroscopy flow, for enabling the realization of a single platform miniaturized blood analyzer. In the proposed analyzer, blood cells are preliminarily sorted by Dielectrophoretic (DEP) means into sub-groups, differentiated and counted by impedance spectroscopy in a flow cytometer. DEP techniques have been demonstrated to stretch DNA, align Carbon Nanotubes (CNT) and trap cells successfully. However, DEP manipulation does not function in biological media with high conductivity. The DI module is designed to account for this challenge. H Filter will serve as an ion extraction platform in a microchamber. Sample and buffer do not mix well in micro scale allowing the ions being extracted by diffusion without increasing the volume. This can keep the downstream processing time short. Micro scale hydrodynamic focusing is employed to place single cell passing along the central plane of the flow cytometer module. By applying an AC electrical field, suspended cells are polarized, membrane capacitance C m, cytoplasm conductivity σ c, and cytoplasm permittivity ɛ c will vary as functions of frequency. Tracing back the monitored current, the numbers of individual cell species can be evaluated.
Determinants of pulmonary perfusion measured by electrical impedance tomography.
Smit, Henk J; Vonk Noordegraaf, Anton; Marcus, J Tim; Boonstra, Anco; de Vries, Peter M; Postmus, Pieter E
2004-06-01
Electrical impedance tomography (EIT) is a non-invasive imaging technique for detecting blood volume changes that can visualize pulmonary perfusion. The two studies reported here tested the hypothesis that the size of the pulmonary microvascular bed, rather than stroke volume (SV), determines the EIT signal. In the first study, the impedance changes relating to the maximal pulmonary pulsatile blood volume during systole (Delta Z(sys)) were measured in ten healthy subjects, ten patients diagnosed with chronic obstructive pulmonary disease, who were considered to have a reduced pulmonary vascular bed, and ten heart failure patients with an assumed low cardiac output but with a normal lung parenchyma. Mean Delta Z(sys) (SD) in these groups was 261 (34)x10(-5), 196 (39)x10(-5) ( Pbicycle while SV was measured by means of magnetic resonance imaging. The Delta Z(sys) at rest was 352 (53)x10(-5 ) and 345 (112)x10(-5 )AU during exercise (P=NS), whereas SV increased from 83 (21) to 105 (34) ml (P<0.05). The EIT signal likely reflects the size of the pulmonary microvascular bed, since neither a low cardiac output nor a change in SV of the heart appear to influence EIT. PMID:14985995
An Electrochemical Impedance Spectroscopy System for Monitoring Pineapple Waste Saccharification
Directory of Open Access Journals (Sweden)
Claudia Conesa
2016-02-01
Full Text Available Electrochemical impedance spectroscopy (EIS has been used for monitoring the enzymatic pineapple waste hydrolysis process. The system employed consists of a device called Advanced Voltammetry, Impedance Spectroscopy & Potentiometry Analyzer (AVISPA equipped with a specific software application and a stainless steel double needle electrode. EIS measurements were conducted at different saccharification time intervals: 0, 0.75, 1.5, 6, 12 and 24 h. Partial least squares (PLS were used to model the relationship between the EIS measurements and the sugar determination by HPAEC-PAD. On the other hand, artificial neural networks: (multilayer feed forward architecture with quick propagation training algorithm and logistic-type transfer functions gave the best results as predictive models for glucose, fructose, sucrose and total sugars. Coefficients of determination (R2 and root mean square errors of prediction (RMSEP were determined as R2 > 0.944 and RMSEP < 1.782 for PLS and R2 > 0.973 and RMSEP < 0.486 for artificial neural networks (ANNs, respectively. Therefore, a combination of both an EIS-based technique and ANN models is suggested as a promising alternative to the traditional laboratory techniques for monitoring the pineapple waste saccharification step.