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
Comparison of Methods for Stroke Volume Computing from Impedance Cardiography
Czech Academy of Sciences Publication Activity Database
Jurák, Pavel; Halámek, Josef; Vondra, Vlastimil; Kára, T.; Nykodým, J.; Číp, Ondřej; Eisenberger, M.; Leinveber, P.; Fráňa, P.; Meluzín, J.; Souček, M.
Brno : Brno University of Technology, 2004, s. 69-71. ISBN 80-214-2633-0. ISSN 1211-412X. [Biosignal 2004 /17./. Brno (CZ), 23.06.2004-25.06.2004] R&D Projects: GA ČR GA102/02/1339 Keywords : Impedance Cardiography * Stroke Volume Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery
Coherent ensemble averaging techniques for impedance cardiography
Hurwitz, Barry E.; Shyu, Liang-Yu; Reddy, Sridhar P; Schneiderman, Neil; Nagel, Joachim H.
1990-01-01
EKG synchronized ensemble averaging of the impedance cardiogram tends to blur or suppress signal events due to signal jitter or event latency variability. Although ensemble averaging provides some improvement in the stability of the signal and signal to noise ratio under conditions of nonperiodic influences of respiration and motion, coherent averaging techniques were developed to determine whether further enhancement of the impedance cardiogram could be obtained. Physiological signals were o...
Czech Academy of Sciences Publication Activity Database
Jurák, Pavel; Halámek, Josef; Vondra, Vlastimil; Viščor, Ivo; Lipoldová, J.; Plachý, M.
2010-01-01
Roč. 37, - (2010), s. 1051-1054. ISSN 0276-6574 R&D Projects: GA AV ČR IAA200650801 Institutional research plan: CEZ:AV0Z20650511 Keywords : respiratory effect * thoracic impedance signal * impedance cardiography Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://cinc.mit.edu/archives/2010/pdf/1051.pdf
The IMPACT shirt: textile integrated and portable impedance cardiography.
Ulbrich, Mark; Mühlsteff, Jens; Sipilä, Auli; Kamppi, Merja; Koskela, Anne; Myry, Manu; Wan, Tingting; Leonhardt, Steffen; Walter, Marian
2014-06-01
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. PMID:24846072
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)
International Nuclear Information System (INIS)
The cardiac resynchronization therapy is an effective treatment for systolic failure patients. Independent electrical stimulation of left and right ventricle corrects mechanical ventricular dyssynchrony. About 30–40% treated patients do not respond to therapy. In order to improve clinical outcome authors propose the two channels impedance cardiography for assessment of ventricular dyssynchrony. The proposed method is intended for validation of patients diagnosis and optimization of pacemaker settings for cardiac resynchronization therapy. The preliminary study has showed that bichannel impedance cardiography is a promising tool for assessment of ventricular dyssynchrony.
Blood Pressure and Impedance Cardiography duríng Tilt Table Test
Czech Academy of Sciences Publication Activity Database
Jurák, Pavel; Halámek, Josef; Vondra, Vlastimil; Plachý, M.; Fráňa, P.; Leinveber, Pavel
2009-01-01
Roč. 36, - (2009), s. 429-432. ISSN 0276-6574 R&D Projects: GA AV ČR IAA200650801 Institutional research plan: CEZ:AV0Z20650511 Keywords : blood pressure * heart rate * thoracic impedance cardiography Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://cinc.mit.edu/archives/2009/pdf/0429.pdf
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...
Czech Academy of Sciences Publication Activity Database
Viščor, Ivo; Jurák, Pavel; Vondra, Vlastimil; Halámek, Josef; Leinveber, Pavel
2009-01-01
Roč. 36, - (2009), s. 749-751. ISSN 0276-6574 R&D Projects: GA AV ČR IAA200650801; GA ČR GP102/07/P425 Institutional research plan: CEZ:AV0Z20650511 Keywords : Mueller maneuver * impedance cardiography * congestive heart failure Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://cinc.mit.edu/archives/2009/pdf/0749.pdf
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
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.
A portable device to assess underwater changes of cardio dynamic variables by impedance cardiography
International Nuclear Information System (INIS)
Data concerning heart rate (HR), stroke volume (SV), and cardiac output (CO) during dynamic apnoea (DA) were collected from 10 healthy male, elite divers by means of an impedance cardiograph adapted to the underwater environment (C. O. Re., from 2C Technologies Inc, Italy). Three trials were performed by the divers in a 3-m-deep pool with a water temperature of 25°C: 3-minute head-out immersion during normal breathing (A), till exhaustion immersed at the surface (B) and at 3m depth (C). Both B and C conditions did not led to changes in HR, SV and CO compared to A. Data indicate that typical diving response consisting in a reduction of HR, SV and CO was not present during DA, probably due to sympathetic activation induced by exercise during DA, which partially obscured the effects of the diving response. Moreover, this study highlights the innovative role of our portable, impedance cardiography device, i.e. the C. O. Re., in easily assessing cardiodynamic changes in subjects engaged in exercise schedules including phases of underwater, dynamic apnoea.
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
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...
Borodiciene, Jurgita; Gudaityte, Jurate; Macas, Andrius
2015-01-01
Background Although the prone position providing better exposure for anorectal surgery is required it can cause a reduction of cardiac output and cardiac index. The goal was to compare haemodynamic changes assessed by impedance cardiography during anorectal surgery under low-dose spinal anaesthesia in lithotomy and jack-knife position. Methods The prospective randomized controlled study included 104, ASA I-II adult patients admitted for elective minor anorectal surgery, assigned to be perform...
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.
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.
International Nuclear Information System (INIS)
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...
The Device for the Two-Channel Impedance Cardiography
Czech Academy of Sciences Publication Activity Database
Vondra, Vlastimil; Verner, Petr; Viščor, Ivo
Brno : University of Technology, 2006, s. 116-118. ISBN 80-214-3152-0. ISSN 1211-412X. [BIOSIGNAL 2006 /18./. Brno (CZ), 28.06.2006-30.06.2006] R&D Projects: GA ČR GA102/06/0136 Institutional research plan: CEZ:AV0Z20650511 Keywords : bioimpedance * cardiac output Subject RIV: FS - Medical Facilities ; Equipment
Directory of Open Access Journals (Sweden)
Jon Kepa Balparda
2012-04-01
Full Text Available La cardiografía de impendancia (CGI representa un método no invasivo para la evaluación del estado hemodinámico latido a latido. Aunque se introdujo por primera vez hace más de 40 años, la CGI ha mostrado un resurgimiento en la última década, a partir de una serie de estudios clínicos que han demostrado su precisión en la estimación del volumen latido, tanto contra el "gold-standard" invasivo (termodilución, como contra los métodos de referencia no invasivos (ecocardiografía. Diversos estudios demuestran la utilidad de esta técnica en el manejo del paciente con falla cardíaca y en el enfoque diagnóstico y terapéutico de la hipertensión arterial, por lo cual constituyen actualmente dos de las aplicaciones clínicas más importantes de la CGI. En falla cardiaca, los cambios en el volumen de líquido del tórax y del gasto cardíaco evaluados por CGI, han demostrado ser predictores de descompensación aguda, incluso semanas antes del inicio de la sintomatología respiratoria; además, permiten identificar el origen cardiogénico o respiratorio de la disnea cuando el examen físico y los demás paraclínicos no son concluyentes. En los pacientes con hipertensión arterial no controlada o resistente, la CGI permite realizar una mejor caracterización del fenotipo hipertensivo y elegir la estrategia farmacológica más específica para intervenir la alteración hemodinámica predominante (resistencia vascular vs. gasto cardiaco elevado. En este artículo se realiza una revisión de los principios biofísicos de la CGI y su utilidad en la evaluación no invasiva del estado hemodinámico, así como una evaluación crítica de la literatura que da soporte a su aplicación clínica en el tratamiento de la falla cardíaca y la hipertensión arterial.Impedance cardiography (ICG represents a non-invasive method for hemodynamic assessment in a beat-to-beat basis. Since its introduction more than forty years ago, a renewed interest in the
Development of a Patch-Type Cardiography Monitoring System for Human Healthcare
Hamada, Hiroyuki; Jiang, Yonggang; Iga, Yuki; Okochi, Sayaka; Kanda, Kensuke; Fujita, Takayuki; Higuchi, Kohei; Maenaka, Kazusuke
This paper describes a wireless cardiography monitoring system for human healthcare. The system consists of a cardiography sensor module and a radio frequency (RF) module for data communication. And the P, Q, R, S, T signals was acquired by using the prototype cardiography sensor. Real-time cardiography monitoring was demonstrated with a RF base station which was located 10 m away from the sensing object.
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.
Czech Academy of Sciences Publication Activity Database
Jurák, Pavel; Halámek, Josef; Vondra, Vlastimil; Viščor, Ivo; Lipoldová, J.; Plachý, M.
Vol. 37. New York: IEEE, 2010, s. 1051-1054. ISBN 978-1-4244-7318-2. ISSN 0276-6574. [Annual Conference of the Computing-in- Cardiology /37./. Belfast (IE), 26.09.2010-29.09.2010] R&D Projects: GA AV ČR IAA200650801 Institutional support: RVO:68081731 Keywords : electrical bioimpendance * cardiac-output Subject RIV: FS - Medical Facilities ; Equipment
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...
Energy Technology Data Exchange (ETDEWEB)
Kelbaek, H.; Svendsen, J.H.; Aldershvile, J.; Folke, K.; Nielsen, S.L.
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 < 0.01). Radionuclide LVEF values also correlated well with cardioangiographic measurements, r = 0.93 (p < 0.001). LVEF determined by multigated radionuclide cardiography was, however, significantly lower than when measured by cardioangiography, the mean difference being 6% (p < 0.001). These findings suggest that radionuclide determinations of SV and LVEF are reliable. The discrepancy between the non-invasive and invasive LVEF values raises the question, whether LVEF is overestimated by cardioangiography or underestimated by radionuclide cardiography.
Two-channel high dynamic range bioimpedance monitor for cardiography
Czech Academy of Sciences Publication Activity Database
Viščor, Ivo; Vondra, Vlastimil; Halámek, Josef
Berlin : Springer, 2007, s. 225-228. ISBN 978-3-540-92840-9. [IFMBE: Electrical Bioimpedance /13./ and Electrical Impedance Tomography /8./. Graz (AT), 29.08.2007-02.09.2007] R&D Projects: GA ČR GP102/07/P425 Institutional research plan: CEZ:AV0Z20650511 Keywords : bioimpedance monitor * dynamic range * reactance * digital quadrature demodulation Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery
Couroussé, Damien
2007-01-01
Mechanical impedance is a transposition to mechanics of the term impedance that is used and defined in circuit theory. The theory of circuit (theory of Kirchhoff networks) is basically applicable to electric networks but can be considered more generally as a unifying simplified theory of physics available in several domains like mechanics, electromagnetism, aero-acoustics and fluids mechanics.
[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%.
Influence of physiological sources on the impedance cardiogram analyzed using 4D FEM simulations
International Nuclear Information System (INIS)
Impedance cardiography is a simple and inexpensive method to acquire data on hemodynamic parameters. This study analyzes the influence of four dynamic physiological sources (aortic expansion, heart contraction, lung perfusion and erythrocyte orientation) on the impedance signal using a model of the human thorax with a high temporal resolution (125 Hz) based on human MRI data. Simulations of electromagnetic fields were conducted using the finite element method. The ICG signal caused by these sources shows very good agreement with the measured signals (r = 0.89). Standard algorithms can be used to extract characteristic points to calculate left ventricular ejection time and stroke volume (SV). In the presented model, the calculated SV equals the implemented left ventricular volume change of the heart. It is shown that impedance changes due to lung perfusion and heart contraction compensate themselves, and that erythrocyte orientation together with the aortic impedance basically form the ICG signal while taking its characteristic morphology from the aortic signal. The model is robust to conductivity changes of tissues and organ displacements. In addition, it reflects the multi-frequency behavior of the thoracic impedance. (paper)
The Influence of Heart and Lung Dynamics on the Impedance Cardiogram — A Simulative Analysis
Directory of Open Access Journals (Sweden)
M. Ulbrich
2011-01-01
Full Text Available Impedance cardiography (ICG is a simple and cheap method for acquiring hemodynamic parameters. Unfortunately, not all physiological influences on the ICG signal have yet been identified. In this work, the influence of heart and lung dynamics is analyzed using a simplified model of the human thorax with high temporal resolution. Simulations are conducted using the finite integration technique (FIT with temporal resolution of 103 Hz. It is shown that changes in heart volume as well as conductivity changes of the lung have a high impact on the ICG signal, if analyzed separately. Considering the sum signal of both physiological sources, it can be shown that they compensate each other and thus do not contribute to the signal. This finding supports Kubicek’s model.
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.
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
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
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)
International Nuclear Information System (INIS)
The proton Storage Ring (PSR), now in operation at Los Alamos, is a fast-cycling high-current accumulator designed to produce intense 800 MeV proton pulses for driving a spallation neutron source. This paper presents graphs of calculated longitudinal and transverse coupling impedances vs frequency for various components in the PSR beamline. The impedances are estimated using simplified formulas for the effects of steps, cavities, monitor plates, and other discontinuities in the beam pipe for the ring. An examination of stability limits indicates that the longitudinal impedance per harmonic should be less than something in the hundreds of ohms range and the transverse impedance should be less than something of the order of a megohm/meter at low frequencies. For the PSR, the impedances due to the harmonic buncher and due to possible high-Q resonances in the bump magnet chambers might be significant. Simplified growth rate estimates using the real part of the transverse impedance indicate that the bumper magnet coils for the fast kicker plates might be contributing to an observed instability with onset at about 1013 protons per bunch
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...
Longitudinal impedance of RHIC
International Nuclear Information System (INIS)
The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2?. For the yellow ring Im(Z/n) = 5.4±1?.
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.
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...... in the transmission such as the earphone impedance. In order to determine the acoustic impedances of human ear canals, the standardized method for measurement of complex impedances used for the measurement of the audiometric earphone impedances is applied. It is based on the transfer function between...... two microphone 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...
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)
Aortic Impedance in Little Mice
Reddy, Anilkumar K.; Taffet, George E.; Hartley, Craig J.
2008-01-01
The Little dwarf mouse lives 30% longer than its age-matched wild-type (WT) mouse. We determined aortic input impedance in 21 (8 Little, 13 WT) 4 month-old mice. Modulus of impedance was calculated from the Fourier transformed aortic pressure (P) and average luminal flow velocity (Vavg) as ∣Zi∣ = ∣P∣/∣Vavg∣. Characteristic impedance was estimated by averaging the 2nd-10th harmonic of the impedance moduli. We found the impedance modulus ∣Zi∣ to be similar in the 2 groups (WT vs. Little; mean±S...
RF impedance measurement calibration
International Nuclear Information System (INIS)
The intent of this note is not to explain all of the available calibration methods in detail. Instead, we will focus on the calibration methods of interest for RF impedance coupling measurements and attempt to explain: (1). The standards and measurements necessary for the various calibration techniques. (2). The advantages and disadvantages of each technique. (3). The mathematical manipulations that need to be applied to the measured standards and devices. (4). An outline of the steps needed for writing a calibration routine that operated from a remote computer. For further details of the various techniques presented in this note, the reader should consult the references
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.
International Nuclear Information System (INIS)
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 mm3) 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
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....
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.
Mechanical Impedance of Cerebral Material
Directory of Open Access Journals (Sweden)
Hédi Ben Ghozlen
2012-03-01
Full Text Available The tentative variation of the mechanical impedance, of a cylindrical sample of cerebral material, has been achieved by Vibrometer Laser according to the frequency. The studied matter is supposed homogeneous, isotropic and stationary. A multilayered mechanical model has been associated to the studied sample to simulate its vibration. The theoretical expression of mechanical impedance has been determined while taking the mechanical/electric analogy as a basis. A good adjustment of theoretical model parameters permitted us to have a good agreement theory/experience of the mechanical impedance variation according to the sample vibration frequency.
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
Noncontact scanning electrical impedance imaging.
Liu, Hongze; Hawkins, Aaron; Schultz, Stephen; Oliphant, Travis E
2004-01-01
We are interested in applying electrical impedance imaging to a single cell because it has potential to reveal both cell anatomy and cell function. Unfortunately, classic impedance imaging techniques are not applicable to this small scale measurement due to their low resolution. In this paper, a different method of impedance imaging is developed based on a noncontact scanning system. In this system, the imaging sample is immersed in an aqueous solution allowing for the use of various probe designs. Among those designs, we discuss a novel shield-probe design that has the advantage of better signal-to-noise ratio with higher resolution compared to other probes. Images showing the magnitude of current for each scanned point were obtained using this configuration. A low-frequency linear physical model helps to relate the current to the conductivity at each point. Line-scan data of high impedance contrast structures can be shown to be a good fit to this model. The first two-dimensional impedance image of biological tissues generated by this technique is shown with resolution on the order of 100 mum. The image reveals details not present in the optical image. PMID:17271930
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...... Source (MCIS) networks to attain a high voltage gain. In addition, the proposed converter draws a continuous current from the source, and hence it is suitable for many types of renewable energy sources. The derived network expressions and theoretical analysis are finally validated experimentally...... 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....
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].
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...
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....
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
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 match...
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...
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.
Impedance based automatic electrode positioning.
Miklody, Daniel; Hohne, Johannes
2015-08-01
The position of electrodes in electrical imaging and stimulation of the human brain is an important variable with vast influences on the precision in modeling approaches. Nevertheless, the exact position is obscured by many factors. 3-D Digitization devices can measure the distribution over the scalp surface but remain uncomfortable in application and often imprecise. We demonstrate a new approach that uses solely the impedance information between the electrodes to determine the geometric position. The algorithm involves multidimensional scaling to create a 3 dimensional space based on these impedances. The success is demonstrated in a simulation study. An average electrode position error of 1.67cm over all 6 subjects could be achieved. PMID:26736345
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 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...... this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26975...
Impedance analysis of acupuncture points and pathways
International Nuclear Information System (INIS)
Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.
Anderson, Karl F. (Inventor)
1994-01-01
A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.
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.
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)
Impedances for electron linacs and storage rings
International Nuclear Information System (INIS)
Some basic concepts and results are presented concerning the impedances of electron linacs and storage rings. The impedances of an accelerator or ring completely characterizes the interaction of the beam with its environment. Not only does the impedance (or its Fourier transform, the wake potential) determine the energy loss by a bunched beam to its environment, but it is also the chief ingredient required for any calculation of beam stability
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.)
Impedance-controlled ultrasound probe
Gilbertson, Matthew W.; Anthony, Brian W.
2011-03-01
An actuated hand-held impedance-controlled ultrasound probe has been developed. The controller maintains a prescribed contact state (force and velocity) between the probe and a patient's body. The device will enhance the diagnostic capability of free-hand elastography and swept-force compound imaging, and also make it easier for a technician to acquire repeatable (i.e. directly comparable) images over time. The mechanical system consists of an ultrasound probe, ball-screw-driven linear actuator, and a force/torque sensor. The feedback controller commands the motor to rotate the ball-screw to translate the ultrasound probe in order to maintain a desired contact force. It was found that users of the device, with the control system engaged, maintain a constant contact force with 15 times less variation than without the controller engaged. The system was used to determine the elastic properties of soft tissue.
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...
Transverse Impedance of Ferrite Elements
Burov, A
2004-01-01
A specific feature of ferrites is that these materials behave either as metals or magneto-dielectrics, depending on the frequency range. Their magnetic permeability is a function of frequency as well. In this paper, the transverse impedance of a ferrite kicker is calculated. The method suggested in Ref. [1] is generalized here for ferrites. Namely, in [1] it is assumed that the electric field of the beam charge dipole is always perfectly shielded. In fact, this assumption requires the conductivity being high compared with the frequency. This is not necessarily true for the high frequencies of a proton single-bunch spectrum. That is why the dynamics of the electric shielding has to be taken into account for ferrite kickers. The generalized analytic result is applied for the ferrite MKE kickers at the CERN SPS, and a fairly good agreement with observations [2] is found.
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
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)
Impedance of Surface Footings on Layered Ground
DEFF Research Database (Denmark)
Andersen, Lars; Clausen, Johan Christian
2005-01-01
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...
Impedance of Surface Footings on Layered Ground
DEFF Research Database (Denmark)
Andersen, Lars; Clausen, Johan
2007-01-01
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 to...
New OTRA-Based Generalized Impedance Simulator
Ashish Gupta; Raj Senani; D. R. Bhaskar; SINGH, A.K.
2013-01-01
Operational transresistance amplifier (OTRA) has attracted considerable attention in the recent literature in several applications such as impedance simulation, universal biquad filter realization, realization of sinusoidal oscillators and multivibrators. However, to the best knowledge of the authors, any OTRA-based generalized impedance simulator circuits have not been reported so far. The purpose of this paper is to present such a circuit.
Analytic methods for calculating coupling impedances
International Nuclear Information System (INIS)
These lecture notes describe a variety of analytic techniques to calculate the longitudinal and transverse impedances of obstacles in a beam pipe. They also treat the effort to shield these impedances from the beam by appropriate use of thin conducting layers. (orig.)
Estimating the short-circuit impedance
DEFF Research Database (Denmark)
Nielsen, Arne Hejde; Pedersen, Knud Ole Helgesen; Poulsen, Niels Kjølstad
through a RLS-algorithm. The algorithms have been tested and implemented on a PC at a 132 kV substation supplying a rolling mill. Knowing the short-circuit impedance gives the rolling mill an opportunity to adjust the arc furnace operation to keep flicker below a certain level. Therefore, the PC performs...... a simultaneously measurement of impedance and flicker....
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.
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)
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.
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.
Summary of the impedance working group
International Nuclear Information System (INIS)
The impedance working group concentrated on the LHC design during the workshop. They look at the impedance contributions of liner, beam position monitors, shielded bellows, experimental chambers, superconducting cavities, recombination chambers, space charge, kickers, and the resistive wall. The group concluded that the impedance budgeting and the conceptual designs of the vacuum chamber components looked basically sound. It also noted, not surprisingly, that a large amount of studies are to be carried out further, and it ventured to give a partial list of these studies
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.
The electrochemical impedance of metal hydride electrodes
DEFF Research Database (Denmark)
Valøen, Lars Ole; Lasia, Andrzej; Jensen, Jens Oluf; Tunold, Reidar
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......, explaining the experimental impedances in a wide frequency range for electrodes of hydride forming materials mixed with copper powder, were obtained. Both charge transfer and spherical diffusion of hydrogen in the particles are important sub processes that govern the total rate of the electrochemical...... observed. The impedance analysis was found to be an efficient method for characterizing metal hydride electrodes in situ....
Estimating the short-circuit impedance
DEFF Research Database (Denmark)
Nielsen, Arne Hejde; Pedersen, Knud Ole Helgesen; Poulsen, Niels Kjølstad
1997-01-01
current are derived each period, and the short-circuit impedance is estimated from variations in these components created by load changes in the grid. Due to the noisy and dynamic grid with high harmonic distortion it is necessary to threat the calculated values statistical. This is done recursively......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...... through a RLS-algorithm. The algorithms have been tested and implemented on a PC at a 132 kV substation supplying a rolling mill. Knowing the short-circuit impedance gives the rolling mill an opportunity to adjust the arc furnace operation to keep flicker below a certain level. Therefore, the PC performs...
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
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
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)
Interpretation of faradaic impedance for Corrosion monitoring
International Nuclear Information System (INIS)
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
Effective impedance modeling of metamaterial structures.
Dossou, Kokou B; Poulton, Christopher G; Botten, Lindsay C
2016-03-01
We present methods for retrieving the effective impedance of metamaterials from the Fresnel reflection coefficients at the interface between two semi-infinite media. The derivation involves the projection of rigorous modal expansions onto the dominant modes of the two semi-infinite media. It is shown that the effective impedance can also be written as a ratio of averaged field quantities. Thus, a number of effective impedance formulas, previously obtained by field averaging techniques, can also be derived from the scattering-based formalism by an appropriate choice of projection. Within the effective medium limit, it is observed that a simple semianalytic modeling technique based on the effective impedance can be used to reliably compute the reflection coefficients of metamaterials over a wide range of incidence angles. We use this technique to model planar metamaterial waveguides or surface modes. PMID:26974905
Study of high impedance magnetic alloy core
International Nuclear Information System (INIS)
J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) and Main Ring (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. The MA core shunt impedance Rp is a key parameter to increase the beam power. To achieve the high shunt impedance Rp, we increased the filling factor by a strong winding tension. As a result, the shunt impedance Rp was reduced in despite of the filling factor increase because the strong winding tension deteriorates the MA core magnetic properties significantly. On the other hand, the MA core with thin ribbons and the MA core that is magnetized by the rotation process show the high permeability in the accelerating frequency region, and those MA cores show the high shunt impedance Rp consequently. (author)
Wave impedance of an atomically thin crystal.
Merano, Michele
2015-11-30
I propose an expression for the electromagnetic wave impedance of a two-dimensional atomic crystal, and I deduce the Fresnel coefficients in terms of this quantity. It is widely known that a two-dimensional crystal can absorb light, if its conductivity is different from zero. It is less emphasized that they can also store a certain amount of electromagnetic energy. The concept of impedance is useful to quantify this point. PMID:26698783
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.
Surface impedance and the Casimir force
Bezerra, V.B.; Klimchitskaya, G. L.; Romero, C.
2001-01-01
The impedance boundary condition is used to calculate the Casimir force in configurations of two parallel plates and a shpere (spherical lens) above a plate at both zero and nonzero temperature. The impedance approach allows one to find the Casimir force between the realistic test bodies regardless of the electromagnetic fluctuations inside the media. Although this approach is an approximate one, it has wider areas of application than the Lifshitz theory of the Casimir force. The general form...
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.
Surface impedance and the Casimir force
International Nuclear Information System (INIS)
The impedance boundary condition is used to calculate the Casimir force in configurations of two parallel plates and a sphere (spherical lens) above a plate at both zero and nonzero temperature. The impedance approach allows one to find the Casimir force between the realistic test bodies regardless of the electromagnetic fluctuations inside the media. Although this approach is an approximate one, it has wider areas of application than the Lifshitz theory of the Casimir force. The general formulas of the impedance approach to the theory of the Casimir force are given and the formal substitution is found for connecting it with the Lifshitz formula. The range of micrometer separations between the test bodies, which is interesting from the experimental point of view, is investigated in detail. It is shown that at zero temperature the results obtained on the basis of the surface impedance method are in agreement with those obtained in framework of the Lifshitz theory within a fraction of a percent. The temperature correction to the Casimir force from the impedance method coincides with that from the Lifshitz theory up to four significant figures. The case of millimeter separations that corresponds to the normal skin effect is also considered. At zero temperature the obtained results have good agreement with the Lifshitz theory. At nonzero temperature the impedance approach is not subject to the interpretation problems peculiar to the zero-frequency term of the Lifshitz formula in dissipative media
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.
Non-contact scanning electrical impedance imaging.
Liu, Hongze; Hawkins, Aaron; Schultz, Stephen; Oliphant, Travis
2004-01-01
We are interested in applying electrical impedance imaging to a single cell because it has potential to reveal both cell anatomy and cell function. Unfortunately, classic impedance imaging techniques are not applicable to this small scale measurement due to their low resolution. In this paper, a different method of impedance imaging is developed based on a non-contact scanning system. In this system, the imaging sample is immersed in an aqueous solution allowing for the use of various probe designs. Among those designs, we discuss a novel shield-probe design that has the advantage of better signal-to-noise ratio with higher resolution compared to other probes. Images showing the magnitude of current for each scanned point were obtained using this configuration. A low-frequency linear physical model helps to relate the current to the conductivity at each point. Line-scan data of high impedance contrast structures can be shown to be a good fit to this model. The first two-dimensional impedance image of biological tissues generated by this technique is shown with resolution on the order of 100 mum. The image reveals details not present in the optical image. PMID:17271931
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.
Respiratory acoustic impedance in left ventricular failure.
Depeursinge, F B; Feihl, F; Depeursinge, C; Perret, C H
1989-12-01
The measurement of respiratory acoustic impedance (Zrs) by forced pseudorandom noise provides a simple means of assessing respiratory mechanics in nonintubated intensive care patients. To characterize the lung mechanical alterations induced by acute vascular congestion of the lung, Zrs was measured in 14 spontaneously breathing patients hospitalized for acute left ventricular failure. The Zrs data in the cardiac patients were compared with those of 48 semirecumbent normal subjects and those of 23 sitting asthmatic patients during allergen-induced bronchospasm. In the patients with acute left ventricular failure, the Zrs abnormalities noted were an excessive frequency dependence of resistance from 10 to 20 Hz and an abnormally low reactance at all frequencies, abnormalities qualitatively similar to those observed in the asthmatic patients but of lesser magnitude. Acute lung vascular congestion modifies the acoustic impedance of the respiratory system. Reflex-induced bronchospasm might be the main mechanism altering respiratory acoustic impedance in acute left ventricular failure. PMID:2582846
Coupling slots without shunt impedance drop
International Nuclear Information System (INIS)
It is well known that coupling slots between adjacent cells in a π-mode structure reduce shunt impedance per unit length with respect to single cell cavities. To design optimized coupling slots, one has to answer the following question: for a given coupling factor, what shape, dimension, position and number of slots lead to the lowest shunt impedance drop? A numerical study using the 3D code MAFIA has been carried out. The aim was to design the 352 MHz cavities for the high intensity proton accelerator of the TRISPAL project. The result is an unexpected set of four 'petal' slots. Such slots should lead to a quasi-negligible drop in shunt impedance: about -1% on average, for particle velocity from 0.4 c to 0.8 c. (author)
Impedance plethysmographic observations in thoracic outlet syndrome.
Directory of Open Access Journals (Sweden)
Nerurkar S
1990-07-01
Full Text Available Forty patients with symptoms of neuro-vascular compression in the upper extremities were subjected to impedance plethysmographic study using Parulkar′s method. Two patients recorded decreased blood flow (BFI in supine position and were diagnosed as having partial occlusion at subclavian level. Sixteen of the patients recorded decreased BFI on 90 degrees abduction and hyper-abduction. Twelve of these patients had radiological evidence of anomalous cervicle ribs. In remaining four patients extrinsic impression on the subclavian artery due to fibrous deposits was confirmed by arteriography. Remaining 22 patients recorded normal impedance plethysmograms. Impedance plethysmography thus provided a non-invasive modality for confirmation of vascular compression in thoracic outlet syndrome.
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
Wave impedance retrieving via Bloch modes analysis
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, S.; Sukhorukov, A.; Malureanu, Radu; Kivshar, Y.; Lavrinenko, Andrei
-ciples violation, like antiresonance behaviour with Im(ε) <0, Im(μ) <0. We employ the Bloch mode analysis of periodic metamaterials to extract the dominating (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 of...... the Bloch mode, respectively. Case studies prove that our ap-proach can determine material and wave effective parameters of lossy and lossless metamaterials. In some examples when the passivity is violated we made further analysis and showed that this is due to the failure of concept of impedance...
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.
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.
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)
Variable high surge impedance loading line
Energy Technology Data Exchange (ETDEWEB)
Drummond, Marcio; Podporkin, Georgij; Ruffier, Aureo P.; Fernandes, Chester; Mesquita, Evanise M. de; Oliveira, Gloria Suzana G. de [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)
1996-07-01
Taking advantage of the High Surge Impedance Loading Line technology and of it's physical characteristics, more specifically those related to the maximization of transmission capacity by increasing the number of sub-conductors, an innovative opportunity related to adaptive electrical parameters of the line was disclosed: the possibility of independently switching of phase sub-conductors to adapt the line impedance to transmission power. The aim of this procedure is to adapt the electrical parameters of the line in such way that Surge Impedance Loading is kept higher enough to make possible the transmitted power, imposing a system favorable operating condition. The assessment of this concept is presented in this paper including electrical studies for the definition of line configuration and steady state power system studies, considering the alternative of feeding power by a hypothetical 230 kV radial transmission line. The transmission distance was varied from 100 km to 300 km. technical and economical comparisons between this new transmission line technology and the conventional one are also presented. Transmission, Transmission Line, High Surge Impedance Loading Line, FACTs. (author)
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.
Explicit Expressions of Impedances and Wake Functions
Energy Technology Data Exchange (ETDEWEB)
Ng, K.Y.; /Fermilab; Bane, K,; /SLAC
2012-06-11
Sections 3.2.4 and 3.2.5 of the Handbook of Accelerator Physics and Engineering on Landau damping are combined and updated. The new addition includes impedances and wakes for multi-layer beam pipe, optical model, diffraction model, and cross-sectional transition.
Explicit expressions of impedances and wake functions
Energy Technology Data Exchange (ETDEWEB)
Ng, K.Y.; /Fermilab; Bane, K,; /SLAC
2010-10-01
Sections 3.2.4 and 3.2.5 of the Handbook of Accelerator Physics and Engineering on Landau damping are combined and updated. The new addition includes impedances and wakes for multi-layer beam pipe, optical model, diffraction model, and cross-sectional transition.
Microwave transmission-line impedance data
Gunston, M A R
1996-01-01
A compendium of data for computing the characteristic impedance of transmission lines based on physical dimensions. Covers both conventional structures and unusual geometries, including coaxial, eccentric and elliptic coaxial, twin-wire, wire-above-ground, microstrip and derivatives, stripline, slabline and trough line. Also details numerous configurations of coupled lines.
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)
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 im...
Electrical impedance spectroscopy and diagnosis of tendinitis
International Nuclear Information System (INIS)
There have been a number of studies that investigate the usefulness of bioelectric signals in diagnoses and treatment in the medical field. Tendinitis is a musculoskeletal disorder with a very high rate of occurrence. This study attempts to examine whether electrical impedance spectroscopy (EIS) can detect pathological changes in a tendon and find the exact location of the lesion. Experimental tendinitis was induced by injecting collagenase into one side of the patellar tendons in rabbits, while the other side was used as the control. After measuring the impedance in the tendinitis and intact tendon tissue, the dissipation factor was computed. The real component of impedance and the dissipation factor turned out to be lower in tendinitis than in intact tissues. Moreover, the tendinitis dissipation factor spectrum showed a clear difference from that of the intact tendon, indicating its usefulness as a tool for detecting the location of the lesion. Pathologic findings from the tissues that were obtained after measuring the impedance confirmed the presence of characteristics of tendinitis. In conclusion, EIS is a useful method for diagnosing tendinitis and detecting the lesion location in invasive treatment
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
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...
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......, explaining the experimental impedances in a wide frequency range for electrodes of hydride forming materials mixed with copper powder, were obtained. Both charge transfer and spherical diffusion of hydrogen in the particles are important sub processes that govern the total rate of the electrochemical...... hydrogen absorption/desorption reaction. To approximate the experimental data, equations describing the current distribution in porous electrodes were needed. Indications of one or more parallel reduction/oxidation processes competing with the electrochemical hydrogen absorption/desorption reaction were...
Impedance effects in the CLIC damping rings
Koukovini-Platia, E; Mounet, N; Rumolo, G; Salvant, B
2011-01-01
Due to the unprecedented brilliance of the beams, the performance of the Compact Linear Collider (CLIC) damping rings (DR) is affected by collective effects. Single bunch instability thresholds based on a broad-band resonator model and the associated coherent tune shifts have been evaluated with the HEADTAIL code. Simulations performed for positive and negative values of chromaticity showed that higher order bunch modes can be potentially dangerous for the beam stability. This study also includes the effects of high frequency resistive wall impedance due to different coatings applied on the chambers of the wigglers for e-cloud mitigation and/or ultra-low vacuum pressure. The impact of the resistive wall wake fields on the transverse impedance budget is finally discussed.
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.
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.
Learning collaborative impedance-based robot behaviors
Rozo, Leonel; Calinon, Sylvain; Caldwell, Darwin,; Jiménez Schlegl, Pablo; Torras, Carme
2013-01-01
Research in learning from demonstration has focused on transferring movements from humans to robots. However, a need is arising for robots that do not just replicate the task on their own, but that also interact with humans in a safe and natural way to accomplish tasks cooperatively. Robots with variable impedance capabilities opens the door to new challenging applications, where the learning algorithms must be extended by encapsulating force and vision information. In this paper we propose a...
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.
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 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)
Electrical impedance studies of uranium oxide
International Nuclear Information System (INIS)
The thesis presents data on the electrical properties of uranium oxide at temperatures from 1700K to 4.2K, and pressures between 25 K bar and 70 K bar. The impedance data were analysed using the technique of complex plane representation to establish the conductivity and dielectric constant of uranium dioxide. The thermophysical data were compared with previously reported experimental and theoretical work on uranium dioxide and other fluorite structured oxides. (U.K.)
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 of a beam tube with antechamber
International Nuclear Information System (INIS)
A beam vacuum chamber was proposed to allow synchrotron light to radiate from a circulating electron beam into an antechamber containing photon targets, pumps, etc. To determine the impedance, electromagnetic measurements were carried out on a section of chamber using for low frequencies a current-carrying wire and for up to 16 GHz, a resonance perturbation method. Because the response of such a chamber would depend on upstream and downstream restrictions of aperture yet to be determined, the resonance studies were analyzed in some generality. The favorable conclusion of these studies is that the antechamber makes practically no contribution to either the longitudinal or the transverse impedances. The small beam tube with slot-isolated antechamber responds as a small cylinder up to the frequency (∼ 15 GHz) where energy can propagate transversely in the narrow slot. The important function of the slot is to prevent the beam from coupling to the many lower-frequency modes of the antechamber. If cut off frequency were higher than the slot-coupling at 15 GHz, only an increased density of modes is expected, with little change in average beam impedances
Bioelectrical impedance analysis of bovine milk fat
Veiga, E. A.; Bertemes-Filho, P.
2012-12-01
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.
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.
PEP-X IMPEDANCE AND INSTABILITY CALCULATIONS
Energy Technology Data Exchange (ETDEWEB)
Bane, K.L.F.; Lee, L.-Q.; Ng, C.; Stupakov, G.; au Wang, L.; Xiao, L.; /SLAC
2010-08-25
PEP-X, a next generation, ring-based light source is designed to run with beams of high current and low emittance. Important parameters are: energy 4.5 GeV, circumference 2.2 km, beam current 1.5 A, and horizontal and vertical emittances, 185 pm by 8 pm. In such a machine it is important that impedance driven instabilities not degrade the beam quality. In this report they study the strength of the impedance and its effects in PEP-X. For the present, lacking a detailed knowledge of the vacuum chamber shape, they create a straw man design comprising important vacuum chamber objects to be found in the ring, for which they then compute the wake functions. From the wake functions they generate an impedance budget and a pseudo-Green function wake representing the entire ring, which they, in turn, use for performing microwave instability calculations. In this report they, in addition, consider in PEP-X the transverse mode-coupling, multi-bunch transverse, and beam-ion instabilities.
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 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.
Using A Particular Sampling Method for Impedance Measurement
Directory of Open Access Journals (Sweden)
Lentka Grzegorz
2014-08-01
Full Text Available 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 measurement instrument based on a PSoC (Programmable System on Chip. The obtained calculation simplification recommends the method for implementation in simple portable impedance analyzers destined for operation in the field or embedding in sensors.
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 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)
Impedance Modeling of Solid Oxide Fuel Cell Cathodes
DEFF Research Database (Denmark)
Mortensen, Jakob Egeberg; Søgaard, Martin; Jacobsen, Torben
2010-01-01
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......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...
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
Effective surface impedance of a high temperature superconductor
International Nuclear Information System (INIS)
Highlights: •Effective surface impedance depends on London penetration depth and operating temperature, T. •The effective surface resistance and the effective surface reactance are important. •The surface resistance determines the electromagnetic power dissipation. -- Abstract: In this work, we will investigate theoretically the effective surface impedance of a high temperature superconducting thin film in the microwave range. This investigation will be according to varying the thickness of the superconducting thin film and the operating temperature, based on means of impedance transformations. The microwave surface impedance is related to the fundamental properties of high-Tc superconductors. The study of surface impedance has two important aspects. The first one is the real part of the surface impedance; the surface resistance determines the electromagnetic power dissipation through the superconductor thin film. The second is the imaginary part of the surface impedance; the surface reactance is proportional to the magnetic-field penetration depth
Effective surface impedance of a high temperature superconductor
Energy Technology Data Exchange (ETDEWEB)
Aly, Arafa H., E-mail: arafa16@yahoo.com; Sabra, Walied
2013-12-15
Highlights: •Effective surface impedance depends on London penetration depth and operating temperature, T. •The effective surface resistance and the effective surface reactance are important. •The surface resistance determines the electromagnetic power dissipation. -- Abstract: In this work, we will investigate theoretically the effective surface impedance of a high temperature superconducting thin film in the microwave range. This investigation will be according to varying the thickness of the superconducting thin film and the operating temperature, based on means of impedance transformations. The microwave surface impedance is related to the fundamental properties of high-T{sub c} superconductors. The study of surface impedance has two important aspects. The first one is the real part of the surface impedance; the surface resistance determines the electromagnetic power dissipation through the superconductor thin film. The second is the imaginary part of the surface impedance; the surface reactance is proportional to the magnetic-field penetration depth.
Acoustic impedances of audiometric earphones coupled to different loads
DEFF Research Database (Denmark)
Ciric, Dejan; Hammershøi, Dorte
The acoustic impedance of an audiometric earphone is one of the factors that can affect sound transmission through the ear during tests of hearing sensitivity. Similar situation exists during calibration of the earphone where its impedance can affect sound transmission through a coupler. The...... importance of this impedance is related to the contribution of other elements involved in transmission such as ear canal impedance or impedance of the coupler seen from outside. In order to determine the acoustic impedances of five audiometric earphones, the standardized method for measurement of complex......, audiometric earphones are coupled to different loads. Thus, they are placed on different terminations of the tube including metal plate, artificial rubber pinna and upper part of the standardized coupler. The results show that the impedances of earphones are different, but they also differ from radiation...
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)
Method for conducting nonlinear electrochemical impedance spectroscopy
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.
Magnetic field dependence of rf surface impedance
International Nuclear Information System (INIS)
In this paper the surface impedance, Zs, is calculated for type-II superconductors subjected to a static magnetic field and small-amplitude microwave radiation. A complex penetration depth is calculated by using a model of vortex dynamics including a linear pinning restoring force and a viscous drag force. The static magnetic field dependence of the surface resistance Rs and surface reactance Xs is found by examining the dependence of the complex penetration depth on the length scales for low-field penetration, pinning penetration, and flux-flow penetration. In turn, from Rs, the static magnetic field dependence of the rate of energy dissipation is found
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.
Adaptive techniques in electrical impedance tomography reconstruction
International Nuclear Information System (INIS)
We present an adaptive algorithm for solving the inverse problem in electrical impedance tomography. To strike a balance between the accuracy of the reconstructed images and the computational efficiency of the forward and inverse solvers, we propose to combine an adaptive mesh refinement technique with the adaptive Kaczmarz method. The iterative algorithm adaptively generates the optimal current patterns and a locally-refined mesh given the conductivity estimate and solves for the unknown conductivity distribution with the block Kaczmarz update step. Simulation and experimental results with numerical analysis demonstrate the accuracy and the efficiency of the proposed algorithm. (paper)
Low impedance kicker for high intensity accelerator
International Nuclear Information System (INIS)
A kicker magnet is one of the most important components in a synchrotron. To kick the beam from injection line to synchrotron orbit or opposite direction, a ferrite material is used to achieve a fast rise time. In case of a high intensity accelerator, the material is heated by beam current. Sometimes, it is reported that characteristic of material is changed when the material reaches Curie temperature. In this paper, we propose a low impedance kicker which consists of thin magnetic alloy ribbon. The structure of the new kicker is suitable to avoid to receive the beam effects. (author)
Impedance matching for broadband piezoelectric energy harvesting
International Nuclear Information System (INIS)
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
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.
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.
Fisher information analysis in electrical impedance tomography
International Nuclear Information System (INIS)
This paper provides a quantitative analysis of the optimal accuracy and resolution in electrical impedance tomography (EIT) based on the Cramér–Rao lower bound. The imaging problem is characterized by the forward operator and its Jacobian. The Fisher information operator is defined for a deterministic parameter in a real Hilbert space and a stochastic measurement in a finite-dimensional complex Hilbert space with a Gaussian measure. The connection between the Fisher information and the singular value decomposition (SVD) based on the maximum likelihood (ML) criterion (the ML-based SVD) is established. It is shown that the eigenspaces of the Fisher information provide a suitable basis to quantify the trade-off between the accuracy and the resolution of the (nonlinear) inverse problem. It is also shown that the truncated ML-based pseudo-inverse is a suitable regularization strategy for a linearized problem, which exploits sufficient statistics for estimation within these subspaces. The statistical-based Cramér–Rao lower bound provides a complement to the deterministic upper bounds and the L-curve techniques that are employed with linearized inversion. To this end, electrical impedance tomography provides an interesting example where the eigenvalues of the SVD usually do not exhibit a very sharp cut-off, and a trade-off between the accuracy and the resolution may be of practical importance. A numerical study of a hypothetical EIT problem is described, including a statistical analysis of the model errors due to the linearization. (paper)
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
Validation of a Numerical Method for Determining Liner Impedance
Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.
1996-01-01
This paper reports the initial results of a test series to evaluate a method for determining the normal incidence impedance of a locally reacting acoustically absorbing liner, located on the lower wall of a duct in a grazing incidence, multi-modal, non-progressive acoustic wave environment without flow. This initial evaluation is accomplished by testing the methods' ability to converge to the known normal incidence impedance of a solid steel plate, and to the normal incidence impedance of an absorbing test specimen whose impedance was measured in a conventional normal incidence tube. The method is shown to converge to the normal incident impedance values and thus to be an adequate tool for determining the impedance of specimens in a grazing incidence, multi-modal, nonprogressive acoustic wave environment for a broad range of source frequencies.
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)
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.
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...
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...
Impedance studies for the PS Finemet loaded longitudinal damper
Persichelli, S; Paoluzzi, M; Salvant, B
2014-01-01
The impedance of the Finemet® loaded longitudinal damper cavity, installed in the CERN Proton Synchrotron straight section 02 during the Long Shutdown 2013-2014, has been evaluated [1]. Time domain simulations with CST Particle Studio have been performed in order to get the longitudinal and transverse impedance of the device and make a comparison with the longitudinal impedance that was measured for a single cell prototype.
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...
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.
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....
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......’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...... clear correlation between the determined parameters and ambient conditions....
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.
In vivo impedance spectroscopy of deep brain stimulation electrodes
Lempka, Scott F.; Miocinovic, Svjetlana; Johnson, Matthew D.; Vitek, Jerrold L.; McIntyre, Cameron C.
2009-08-01
Deep brain stimulation (DBS) represents a powerful clinical technology, but a systematic characterization of the electrical interactions between the electrode and the brain is lacking. The goal of this study was to examine the in vivo changes in the DBS electrode impedance that occur after implantation and during clinically relevant stimulation. Clinical DBS devices typically apply high-frequency voltage-controlled stimulation, and as a result, the injected current is directly regulated by the impedance of the electrode-tissue interface. We monitored the impedance of scaled-down clinical DBS electrodes implanted in the thalamus and subthalamic nucleus of a rhesus macaque using electrode impedance spectroscopy (EIS) measurements ranging from 0.5 Hz to 10 kHz. To further characterize our measurements, equivalent circuit models of the electrode-tissue interface were used to quantify the role of various interface components in producing the observed electrode impedance. Following implantation, the DBS electrode impedance increased and a semicircular arc was observed in the high-frequency range of the EIS measurements, commonly referred to as the tissue component of the impedance. Clinically relevant stimulation produced a rapid decrease in electrode impedance with extensive changes in the tissue component. These post-operative and stimulation-induced changes in impedance could play an important role in the observed functional effects of voltage-controlled DBS and should be considered during clinical stimulation parameter selection and chronic animal research studies.
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.
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.
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)
Esophageal impedance baseline according to different time intervals
Directory of Open Access Journals (Sweden)
Ummarino Dario
2012-06-01
Full Text Available Abstract Background The impedance baseline has been shown to reflect esophageal integrity, and to be decreased in patients with esophagitis. However, different methods for the determination of the impedance baseline have not been compared. Methods The median impedance baseline was calculated in 10 consecutive multichannel intraluminal impedance recordings in children with non-erosive reflux disease. All children underwent an endoscopy with a biopsy as part of the clinical work-up to exclude esophagitis. The impedance baseline was obtained both by including and excluding all impedance episodes (IE; reflux, swallows and gas episodes during the full recording, and during the first 1-minute period without an IE every hour (method 1, every 2 hours (method 2 or every 4 hours (method 3. The impedance baseline obtained during the full recording was set at 100%, and the variation (difference in impedance baseline for the different methods and variability (difference in impedance baseline during one analysis period were assessed. Results None of the participants had esophagitis. The mean difference over the six channels between the impedance baseline over the total recording with and without IE was approximately 2.5%, and comparable for each channel (range 0.47% to 5.55%. A mean of 1,028 IEs were excluded in each tracing, and it took between 4 and 24 hours to delete all events in one tracing. The difference in the impedance baseline obtained with and without IEs was mainly caused by the gas episodes in the upper channels and swallows in the lower channels. The median impedance baseline according to the three one-minute analysis methods was comparable to the median impedance baseline according to the 24 hour analysis. Conclusions The automatic determination of the median impedance baseline over the total tracing including IEs is an adequate method. In isolated tracings with numerous IEs, the calculation of the median impedance baseline over one minute
Validation of an Impedance Education Method in Flow
Watson, Willie R.; Jones, Michael G.; Parrott, Tony L.
2004-01-01
This paper reports results of a research effort to validate a method for educing the normal incidence impedance of a locally reacting liner, located in a grazing incidence, nonprogressive acoustic wave environment with flow. The results presented in this paper test the ability of the method to reproduce the measured normal incidence impedance of a solid steel plate and two soft test liners in a uniform flow. The test liners are known to be locally react- ing and exhibit no measurable amplitude-dependent impedance nonlinearities or flow effects. Baseline impedance spectra for these liners were therefore established from measurements in a conventional normal incidence impedance tube. A key feature of the method is the expansion of the unknown impedance function as a piecewise continuous polynomial with undetermined coefficients. Stewart's adaptation of the Davidon-Fletcher-Powell optimization algorithm is used to educe the normal incidence impedance at each Mach number by optimizing an objective function. The method is shown to reproduce the measured normal incidence impedance spectrum for each of the test liners, thus validating its usefulness for determining the normal incidence impedance of test liners for a broad range of source frequencies and flow Mach numbers. Nomenclature
Lower leg electrical impedance after distal bypass surgery
DEFF Research Database (Denmark)
Belanger, G K; Bolbjerg, M L; Heegaard, N H; Wiik, A; Schroeder, T V; Secher, 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...... concentration of troponin I (n = 8). In conclusion, tissue injury was reflected by increases in muscle enzymes in plasma. We found an inverse correlation between lower leg electrical impedance and volume, but the deviation in electrical impedance was approximately twice that of the leg volume. Electrical...... impedance appears to be a useful method for the evaluation of lower leg oedema after distal bypass surgery....
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.
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.
Proceedings of the impedance and bunch instability workshop
International Nuclear Information System (INIS)
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)
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.
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...... circuit configurations and the design procedures are proposed. Synthesis relations are derived and provided for efficient matching circuit construction. Design examples are given to demonstrate the flexibility and limitations of the design methods and to show their validity for practical applications....... 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....
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.
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.
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.
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.
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.
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.
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)
Development of impedance matching technologies for ICRF antenna arrays
International Nuclear Information System (INIS)
All high power ICRF heating systems include devices for matching the input impedance of the antenna array to the generator output impedance. For most types of antennas used, the input impedance is strongly time-dependent on timescales as rapid as 10-4 s, while the rf generators used are capable of producing full power only into a stationary load impedance. Hence, the dynamic response of the matching method is of great practical importance. In this paper, world-wide developments in this field over the past decade are reviewed. These techniques may be divided into several classes. The edge plasma parameters that determine the antenna array's input impedance may be controlled to maintain a fixed load impedance. The frequency of the rf source can be feedback controlled to compensate for changes in the edge plasma conditions, or fast variable tuning elements in the transmission line between the generator output and the antenna input connections can provide the necessary time-varying impedance transformation. In lossy passive schemes, reflected power due to the time-varying impedance of the antenna array is diverted to a dummy load. Each of these techniques can be applied to a pre-existing antenna system. If a new antenna is to be designed, recent advances allow the antenna array to have the intrinsic property of presenting a constant load to the feeding transmission lines despite the varying load seen by each antenna in the array
Effect of Feeding and Suction on Gastric Impedance Spectroscopy Measurements.
Beltran, Nohra E; Sánchez-Miranda, Gustavo; Sacristan, Emilio
2015-01-01
A specific device and system has been developed and tested for clinical monitoring of gastric mucosal reactance in the critically ill as an early warning of splanchnic hypoperfusion associated with shock and sepsis. This device has been proven effective in clinical trials and is expected to become commercially available next year. The system uses a combination nasogastric tube and impedance spectroscopy probe as a single catheter. Because this device has a double function, the question is: Does enteral feeding or suction affect the gastric reactance measurements? This study was designed to evaluate the effect of feeding and suction on the measurement of gastric impedance spectroscopy in healthy volunteers. Impedance spectra were obtained from the gastric wall epithelia of 18 subjects. The spectra were measured for each of the following conditions: postinsertion of gastric probe, during active suction, postactive suction, and during enteral feeding (236 ml of nutritional supplement). Impedance spectra were reproducible in all volunteers under all conditions tested. There was a slight increase in impedance parameters after suction, and a decrease in impedance after feeding; however, these observed differences were insignificant compared to patient-to-patient variability, and truly negligible compared with previously observed changes associated with splanchnic ischemia in critically ill patients. Our results demonstrate that suction or feeding when using the impedance spectro-metry probe/nasogastric tube does not significantly interfere with gastric impedance spectrometer measurements. PMID:26226020
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.
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.
Development on electromagnetic impedance function modeling and its estimation
Sutarno, D.
2015-09-01
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
Development on electromagnetic impedance function modeling and its estimation
International Nuclear Information System (INIS)
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
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
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.
Impedance Coordinative Control for Cascaded Converter in Bidirectional Application
DEFF Research Database (Denmark)
Tian, Yanjun; Deng, Fujin; Chen, Zhe;
2015-01-01
Two stage cascaded converters are widely used in bidirectional applications, but the negative impedance may cause system instability. Actually the impedance interaction is much different between forward power flow and reversed power flow, which will introduce more uncertainty to the system...... difference between forward and reversed power flow. This paper addresses the analysis with the topology of cascaded dual-active-bridge converter (DAB) with inverter, and the proposed control method can also be implemented in unidirectional applications and other general cascaded converter system. The...... stability. This paper proposes a control method for the constant power controlled converter in cascaded system, and consequently it can change the negative impedance of constant power converter into resistive impedance, which will improve the cascaded system stability, as well as merge the impedance...
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.
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.
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
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.
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...
Impedance spectroscopy for the detection and identification of unknown toxins
Riggs, B. C.; Plopper, G. E.; Paluh, J. L.; Phamduy, T. B.; Corr, D. T.; Chrisey, D. B.
2012-06-01
Advancements in biological and chemical warfare has allowed for the creation of novel toxins necessitating a universal, real-time sensor. We have used a function-based biosensor employing impedance spectroscopy using a low current density AC signal over a range of frequencies (62.5 Hz-64 kHz) to measure the electrical impedance of a confluent epithelial cell monolayer at 120 sec intervals. Madin Darby canine kidney (MDCK) epithelial cells were grown to confluence on thin film interdigitated gold electrodes. A stable impedance measurement of 2200 Ω was found after 24 hrs of growth. After exposure to cytotoxins anthrax lethal toxin and etoposide, the impedance decreased in a linear fashion resulting in a 50% drop in impedance over 50hrs showing significant difference from the control sample (~20% decrease). Immunofluorescent imaging showed that apoptosis was induced through the addition of toxins. Similarities of the impedance signal shows that the mechanism of cellular death was the same between ALT and etoposide. A revised equivalent circuit model was employed in order to quantify morphological changes in the cell monolayer such as tight junction integrity and cell surface area coverage. This model showed a faster response to cytotoxin (2 hrs) compared to raw measurements (20 hrs). We demonstrate that herein that impedance spectroscopy of epithelial monolayers serves as a real-time non-destructive sensor for unknown pathogens.
Measuring the Acoustic Impedance of Pipes and Musical Instruments
Jaeger, Herbert
2007-05-01
Using a small electret microphone and a piezo-buzzer we have constructed a simple impedance transducer to measure the input impedance of air columns, such as cylindrical pipes, as well as musical instruments. The input impedance of an air column is given as the ratio of the pressure to the volume flow of air at the input of the air column. The microphone serves as the pressure transducer, while the piezo-buzzer is controlled to provide a constant velocity amplitude. Therefore the microphone signal is proportional to the acoustical impedance and, if required, can be calibrated using a simple air column for which the impedance can be calculated. This impedance transducer is currently in use as demonstration equipment for a physical acoustics class. It is simple to use and robust, so that it is well-suited for an undergraduate introductory laboratory environment. This talk will discuss the function of the impedance transducer and show examples of the type of measurements that can be performed. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.OSS07.C1.1
Characterizing aging effects of lithium ion batteries by impedance spectroscopy
International Nuclear Information System (INIS)
Impedance spectroscopy is one of the most promising methods for characterizing aging effects of portable secondary batteries online because it provides information about different aging mechanisms. However, application of impedance spectroscopy 'in the field' has some higher requirements than for laboratory experiments. It requires a fast impedance measurement process, an accurate model applicable with several batteries and a robust method for model parameter estimation. In this paper, we present a method measuring impedance at different frequencies simultaneously. We propose to use a composite electrode model, capable to describe porous composite electrode materials. A hybrid method for parameter estimation based on a combination of evolution strategy and Levenberg-Marquardt method allowed a robust and fast parameter calculation. Based on this approach, an experimental investigation of aging effects of a lithium ion battery was carried out. After 230 discharge/charge cycles, the battery showed a 14% decreased capacity. Modeling results show that series resistance, charge transfer resistance and Warburg coefficient changed thereby their values by approximately 60%. A single frequency impedance measurement, usually carried out at 1 kHz, delivers only information about series resistance. Impedance spectroscopy allows additionally the estimation of charge transfer resistance and Warburg coefficient. This fact and the high sensitivity of model parameters to capacity change prove that impedance spectroscopy together with an accurate modeling deliver information that significantly improve characterization of aging effects
A comparison study of electrodes for neonate electrical impedance tomography
International Nuclear Information System (INIS)
Electrical impedance tomography (EIT) is an imaging technique that has the potential to be used for studying neonate lung function. The properties of the electrodes are very important in multi-frequency EIT (MFEIT) systems, particularly for neonates, as the skin cannot be abraded to reduce contact impedance. In this work, the impedance of various clinical electrodes as a function of frequency is investigated to identify the optimum electrode type for this application. Six different types of self-adhesive electrodes commonly used in general and neonatal cardiology have been investigated. These electrodes are Ag/AgCl electrodes from the Ambu® Cardiology Blue sensors range (BR, NF and BRS), Kendall (KittyCat(TM) and ARBO®) and Philips 13953D electrodes. In addition, a textile electrode without gel from Textronics was tested on two subjects to allow comparison with the hydrogel-based electrodes. Two- and four-electrode measurements were made to determine the electrode-interface and tissue impedances, respectively. The measurements were made on the back of the forearm of six healthy adult volunteers without skin preparation with 2.5 cm electrode spacing. Impedance measurements were carried out using a Solartron SI 1260 impedance/gain-phase analyser with a frequency range from 10 Hz to 1 MHz. For the electrode-interface impedance, the average magnitude decreased with frequency, with an average value of 5 kΩ at 10 kHz and 337 Ω at 1 MHz; for the tissue impedance, the respective values were 987 Ω and 29 Ω. Overall, the Ambu BRS, Kendall ARBO® and Textronics textile electrodes gave the lowest electrode contact impedance at 1 MHz. Based on the results of the two-electrode measurements, simple RC models for the Ambu BRS and Kendall-ARBO and Textronics textile electrodes have been derived for MFEIT applications
Measurements of the SPS transverse impedance in 2000
Arduini, Gianluigi; Cornelis, Karel; Klem, J T; Zimmermann, Frank; Zorzano-Mier, M P
2001-01-01
We report on measurements of coherent tune shifts, head-tail growth rates, and current-dependent betatron phase advances at the CERN SPS in the year 2000. Comparing results obtained at two different energies shows that there is no notable contribution from space charge. Within the measurement resolution the impedance is the same as in 1999, consistent with the expected small effect from changes to ony a small number of pumping ports. In 2000, data were taken over an expanded range of chromaticities, which increases the sensitivity to the impedance frequency distribution. Measuremeents of the current-dependent phase advance around the ring help localizing the most important impedance sources.
Literature Review on Recent Magnetocardiography and Impedance-Magnetocardiography Technologies
Energy Technology Data Exchange (ETDEWEB)
Kandori, A.; Miyashita, T.; Ogata, K. [Advaned Research Laboratory, Hitachi, Ltd, Mito (Japan); and others
2006-10-15
We have developed magnetocardiography(MCG) and impedance magnetocardiography(I-MCG) for detecting heart disease by using dc-SQUID technology. The MCG system, using low-Tc SQUID, is being applied commercially for diagnosing heart disease. Using the low-Tc MCG system, many clinical studies on detection of abnormality have been performed. Furthermore, we have developed a portable MCG system using high-Tc SQUID. For detecting changes in kinetic impedance in the heart, an I-MCG system has been demonstrated. The I-MCG system could detect the mechanical movement of the heart. In this report, we review current clinical applications of magnetocardiography and impedance magnetocardiography.
MEASURED TRANSVERSE COUPLING IMPEDANCE OF RHIC INJECTION AND ABORT KICKERS
International Nuclear Information System (INIS)
Concerns regarding possible transverse instabilities in RHIC and the SNS pointed to the need for measurements of the transverse coupling impedance of ring components. The impedance of the RHIC injection and abort kicker was measured using the conventional method based on the S21 forward transmission coefficient. A commercial 450 Ω twin-wire Lecher line were used and the data was interpreted via the log-formula. All measurements, were performed in test stands fully representing operational conditions including pulsed power supplies and connecting cables. The measured values for the transverse coupling impedance in kick direction and perpendicular to it are comparable in magnitude, but differ from Handbook predictions
PHEMT Distributed Power Amplifier Adopting Broadband Impedance Transformer
DEFF Research Database (Denmark)
Narendra, K.; Limiti, E.; Paoloni, C.; Zhurbenko, Vitaliy
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...... transmission line. The output power of approximately 600 mW, with an associated gain of 9 dB and PAE greater than 30 percent, is demonstrated in the frequency range from 10 to 1800 MHz....
Impedance-type measurements using XPS
International Nuclear Information System (INIS)
An impedance type of measurement using X-ray photoelectron spectroscopy is applied for probing charging/discharging dynamics of a sample containing Rb deposited on a SiO2/Si substrate containing an octadecyltrichlorosilane (OTS) bilayer coating. The OTS bilayer coatings have possible use as anti-relaxation wall coatings for alkali atom vapor cells in miniaturized instruments such as chip-scale atomic clocks, and/or magnetometers. The measurement consists of the application of bipolar square wave pulses of ±10.0 V amplitude to the sample with varying frequencies in the range of 10-2 to 102 Hz while recording X-ray photoemission data. For a conducting sample this type of measurement twins all the photoemission peaks at -10.0 and +10.0 eV positions at all frequencies with exactly 20.0 eV difference between them. However, for samples amenable to charging, the difference between the twinned peaks is less than 20.0 eV, and gradually decreases at correspondingly lower frequencies. For the sample under consideration here at 0.01 Hz, the twinned O1s and Si2p peaks, representing the SiO2 substrate, are separated by 18.2 eV, displaying a 1.8 eV charging shift. These positions differ from those of the C1s (18.0 eV) representing the OTS bilayer and the Rb3d peaks (18.1 eV). These results reveal that the Rb is electrically (perhaps also chemically) isolated from the OTS bilayer, which may be correlated with the improved performance of the OTS bilayers as anti-relaxation coatings in these alkali atom magnetometer cells.
Volume dependence of respiratory impedance in infants.
Peták, F; Hayden, M J; Hantos, Z; Sly, P D
1997-10-01
We previously studied low-frequency respiratory impedance (Zrs) data at an elevated lung volume to separate airway and tissue mechanical properties in normal infants (Am. I. Respir. Crit. Care Med. 1996; 154:161-166). The aim of the present study was to determine the volume dependence of the airway and tissue mechanics by extending Zrs measurements to lower lung volumes. Zrs spectra between 0.5 and 21 Hz were measured in supine sleeping infants (n = 8; 7 to 26 mo of age) at mean transrespiratory pressures (Ptr[mean]) of 20, 10, and 0 cm H2O, during periods of apnea induced by inflating the infants' lungs to a pressure of 20 cm H2O through a face mask. At each inflation pressure, a model containing airway resistance (Raw) and inertance (law) and tissue damping (G) and elastance (H) was fitted to Zrs data. At FRC, the values of Raw, law, G, and H were 20.6+/-4.9 (SD) cm H2O x s/L, 0.037+/-0.014 cm H2O x s2/L, 39.6+/-10.3 cm H2O/L, and 147+/-35 cm H2O/L, respectively. Increase of Ptr(mean) caused a monotonous decrease in Raw (42+/-7% of the value at FRC), while law remained constant. The tissue parameters were minimal at a Ptr(mean) of 10 cm H2O (68+/-10% and 78+/-6% in G and H, respectively) and significantly higher at both 0 and 20 cm H2O. Although Zrs measurements can be made in most infants at lung volumes as low as FRC, an inflation pressure of 20 cm H2O provides a higher success rate and is therefore a more suitable condition for general use. PMID:9351618
Qin, F. X.; Peng, H. X.; Popov, V. V.; Phan, M. H.
2011-02-01
Composites consisting of glass-coated amorphous microwire Co 68.59Fe 4.84Si 12.41B 14.16 and 913 E-glass prepregs were designed and fabricated. The influences of tensile stress, annealing and number of composite layers on the giant magneto-impedance (GMI) and giant stress-impedance (GSI) effects in these composites were investigated systematically. It was found that the application of tensile stress along the microwire axis or an increase in the number of composite layers reduced the GMI effect and increased the circular anisotropy field, while the annealing treatment had a reverse effect. The value of matrix-wire interfacial stress calculated via the GMI profiles coincided with the value of the applied effective tensile stress to yield similar GMI profiles. Enhancement of the GSI effect was achieved in the composites relative to their single microwire inclusion. These findings are important for the development of functional microwire-based composites for magnetic- and stress-sensing applications. They also open up a new route for probing the interfacial stress in fibre-reinforced polymer (FRP) composites.
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.
Bioelectrical impedance analysis for bovine milk: Preliminary results
Bertemes-Filho, P.; Valicheski, R.; Pereira, R. M.; Paterno, A. S.
2010-04-01
This work reports the investigation and analysis of bovine milk quality by using biological impedance measurements using electrical impedance spectroscopy (EIS). The samples were distinguished by a first chemical analysis using Fourier transform midinfrared spectroscopy (FTIR) and flow citometry. A set of milk samples (100ml each) obtained from 17 different cows in lactation with and without mastitis were analyzed with the proposed technique using EIS. The samples were adulterated by adding distilled water and hydrogen peroxide in a controlled manner. FTIR spectroscopy and flow cytometry were performed, and impedance measurements were made in a frequency range from 500Hz up to 1MHz with an implemented EIS system. The system's phase shift was compensated by measuring saline solutions. It was possible to show that the results obtained with the Bioelectrical Impedance Analysis (BIA) technique may detect changes in the milk caused by mastitis and the presence of water and hydrogen peroxide in the bovine milk.
Studying of acid-gas pipelines corrosion with impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Neshati, J.; Fardi, M.R.; Ghassem, H. [Corrosion Department, NIOC-RIPI, Pazhooheshgah Bulevard, Khairabad Junction, Old Qom Road Tehran (Iran)
2004-07-01
In this research, the acid-gas pipelines of a gas refinery were simulated in laboratory. Acid gas is normally the feed of sulfur recovery plant (SRP) in a gas refinery. For studying corrosion kinetic and related mechanisms the impedance spectroscopy was used. Impedance diagrams were simulated by Boukamp1988 software. It was found that the simulated systems can be equated to a circuit with two time constants. For studying corrosion rate changes a type of inhibitor was utilized. The inhibitor used in this work was an imidazoline, an appropriate based inhibitor formulated with the commercial grade imidazoline and dimmer - trimer acid. It was shown that impedance spectroscopy technique can be used for corrosion monitoring of acid gas pipelines in gas refineries. The impedance spectroscopy will be tried in due course as a suitable technique in field for corrosion control of acid-gas pipelines. (authors)
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 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.
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.
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...
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.