Science.gov

Sample records for acoustic impedance measurements

  1. Acoustic Impedance Measurement for Underground Surfaces.

    NASA Astrophysics Data System (ADS)

    Cockcroft, Paul William

    Available from UMI in association with The British Library. Requires signed TDF. This thesis investigates the measurement of acoustic impedance for surfaces likely to be found in underground coal mines. By introducing the concepts of industrial noise, the effects of noise on the ear and relevant legislation the need for the protection of workers can be appreciated. Representative acoustic impedance values are vital as input for existing computer models that predict sound levels in various underground environments. These enable the mining engineer to predict the noise level at any point within a mine in the vicinity of noisy machinery. The concepts of acoustic intensity and acoustic impedance are investigated and different acoustic impedance measurement techniques are detailed. The possible use of either an impedance tube or an intensity meter for these kinds of measurements are suggested. The problems with acoustic intensity and acoustic impedance measurements are discussed with reference to the restraints that an underground environment imposes on any measurement technique. The impedance tube method for work in an acoustics laboratory is shown and the theory explained, accompanied by a few representative results. The use of a Metravib intensity meter in a soundproof chamber to gain impedance values is explained in detail. The accompanying software for the analysis of the two measured pressure signals is shown as well as the actual results for a variety of test surfaces. The use of a Nagra IV-SJ tape recorder is investigated to determine the effect of recording on the measurement and subsequent analysis of the input signals, particularly with reference to the phase difference introduced between the two simultaneous pressure signals. The subsequent use of a Norwegian Electronic intensity meter, including a proposal for underground work, is shown along with results for tests completed with this piece of equipment. Finally, recommendations are made on how to link up

  2. Acoustic impedance measurements of pulse tube refrigerators

    NASA Astrophysics Data System (ADS)

    Iwase, Takashi; Biwa, Tetsushi; Yazaki, Taichi

    2010-02-01

    Complex acoustic impedance is determined in a prototype refrigerator that can mimic orifice-type, inertance-type, and double inlet-type pulse tube refrigerators from simultaneous measurements of pressure and velocity oscillations at the cold end. The impedance measurements revealed the means by which the oscillatory flow condition in the basic pulse tube refrigerator is improved by additional components such as a valve and a tank. The working mechanism of pulse tube refrigerators is explained based on an electrical circuit analogy.

  3. A new method to measure the acoustic surface impedance outdoors.

    PubMed

    Carpinello, S; L'Hermite, Ph; Bérengier, M; Licitra, G

    2004-01-01

    In the European countries noise pollution is considered to be one of the most important environmental problems. With respect to traffic noise, different researchers are working on the reduction of noise at the source, on the modelling of the acoustic absorption of the road structure and on the effects of the pavement on the propagation. The aim of this paper is to propose a new method to measure the acoustic impedance of surfaces located outdoors, which allows us to further noise propagation models, in order to evaluate exactly the noise exposure.

  4. Optimization of Acoustic Pressure Measurements for Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; Nark, D. M.

    2007-01-01

    As noise constraints become increasingly stringent, there is continued emphasis on the development of improved acoustic liner concepts to reduce the amount of fan noise radiated to communities surrounding airports. As a result, multiple analytical prediction tools and experimental rigs have been developed by industry and academia to support liner evaluation. NASA Langley has also placed considerable effort in this area over the last three decades. More recently, a finite element code (Q3D) based on a quasi-3D implementation of the convected Helmholtz equation has been combined with measured data acquired in the Langley Grazing Incidence Tube (GIT) to reduce liner impedance in the presence of grazing flow. A new Curved Duct Test Rig (CDTR) has also been developed to allow evaluation of liners in the presence of grazing flow and controlled, higher-order modes, with straight and curved waveguides. Upgraded versions of each of these two test rigs are expected to begin operation by early 2008. The Grazing Flow Impedance Tube (GFIT) will replace the GIT, and additional capabilities will be incorporated into the CDTR. The current investigation uses the Q3D finite element code to evaluate some of the key capabilities of these two test rigs. First, the Q3D code is used to evaluate the microphone distribution designed for the GFIT. Liners ranging in length from 51 to 610 mm are investigated to determine whether acceptable impedance eduction can be achieved with microphones placed on the wall opposite the liner. This analysis indicates the best results are achieved for liner lengths of at least 203 mm. Next, the effects of moving this GFIT microphone array to the wall adjacent to the liner are evaluated, and acceptable results are achieved if the microphones are placed off the centerline. Finally, the code is used to investigate potential microphone placements in the CDTR rigid wall adjacent to the wall containing an acoustic liner, to determine if sufficient fidelity can be

  5. The use of electro-acoustic impedance measurements in detecting early clinical otosclerosis.

    PubMed

    Van Wagoner, R S; Campbell, J D

    1976-02-01

    The first evidence that sodium fluoride (NaFl) can stop the otosclerotic process was recently presented. This development has placed new emphasis on the early detection of clinical otosclerosis. Electro-acoustic impedance measurements often detect minute changes in absolute impedance and compliance of the ossicular chain. The most valuable diagnostic information, however, is a negative on-off (biphasic) type of acoustic reflex. These results are often evident prior to the detection of positive clinical signs of otosclerosis. The negative on-off acoustic reflex is reviewed in this paper along with case discussions involving medical/surgical management of early otosclerosis.

  6. Acoustic input impedance of the avian inner ear measured in ostrich (Struthio camelus).

    PubMed

    Muyshondt, Pieter G G; Aerts, Peter; Dirckx, Joris J J

    2016-09-01

    In both mammals and birds, the mechanical behavior of the middle ear structures is affected by the mechanical impedance of the inner ear. In this study, the aim was to quantify the acoustic impedance of the avian inner ear in the ostrich, which allows us to determine the effect on columellar vibrations and middle ear power flow in future studies. To determine the inner ear impedance, vibrations of the columella were measured for both the quasi-static and acoustic stimulus frequencies. In the frequency range of 0.3-4 kHz, we used electromagnetic stimulation of the ossicle and a laser Doppler vibrometer to measure the vibration response. At low frequencies, harmonic displacements were imposed on the columella using piezo stimulation and the resulting force response was measured with a force sensor. From these measurement data, the acoustic impedance of the inner ear could be determined. A simple RLC model in series of the impedance measurements resulted in a stiffness reactance of KIE = 0.20·10(12) Pa/m³, an inertial impedance of MIE = 0.652·10(6) Pa s(2)/m³, and a resistance of RIE = 1.57·10(9) Pa s/m. We found that values of the inner ear impedance in the ostrich are one to two orders in magnitude smaller than what is found in mammal ears.

  7. Acoustic Ground-Impedance Meter

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.

    1983-01-01

    Helmoltz resonator used in compact, portable meter measures acoustic impedance of ground or other surfaces. Earth's surface is subject of increasing acoustical investigations because of its importance in aircraft noise prediction and measurment. Meter offers several advantages. Is compact and portable and set up at any test site, irrespective of landscape features, weather or other environmental condition.

  8. Measurements and computational fluid dynamics predictions of the acoustic impedance of orifices

    NASA Astrophysics Data System (ADS)

    Su, J.; Rupp, J.; Garmory, A.; Carrotte, J. F.

    2015-09-01

    The response of orifices to incident acoustic waves, which is important for many engineering applications, is investigated with an approach combining both experimental measurements and numerical simulations. This paper presents experimental data on acoustic impedance of orifices, which is subsequently used for validation of a numerical technique developed for the purpose of predicting the acoustic response of a range of geometries with moderate computational cost. Measurements are conducted for orifices with length to diameter ratios, L/D, of 0.5, 5 and 10. The experimental data is obtained for a range of frequencies using a configuration in which a mean (or bias) flow passes from a duct through the test orifices before issuing into a plenum. Acoustic waves are provided by a sound generator on the upstream side of the orifices. Computational fluid dynamics (CFD) calculations of the same configuration have also been performed. These have been undertaken using an unsteady Reynolds averaged Navier-Stokes (URANS) approach with a pressure based compressible formulation with appropriate characteristic based boundary conditions to simulate the correct acoustic behaviour at the boundaries. The CFD predictions are in very good agreement with the experimental data, predicting the correct trend with both frequency and orifice L/D in a way not seen with analytical models. The CFD was also able to successfully predict a negative resistance, and hence a reflection coefficient greater than unity for the L / D = 0.5 case.

  9. A Comparison Study of Normal-Incidence Acoustic Impedance Measurements of a Perforate Liner

    NASA Technical Reports Server (NTRS)

    Schultz, Todd; Liu, Fei; Cattafesta, Louis; Sheplak, Mark; Jones, Michael

    2009-01-01

    The eduction of the acoustic impedance for liner configurations is fundamental to the reduction of noise from modern jet engines. Ultimately, this property must be measured accurately for use in analytical and numerical propagation models of aircraft engine noise. Thus any standardized measurement techniques must be validated by providing reliable and consistent results for different facilities and sample sizes. This paper compares normal-incidence acoustic impedance measurements using the two-microphone method of ten nominally identical individual liner samples from two facilities, namely 50.8 mm and 25.4 mm square waveguides at NASA Langley Research Center and the University of Florida, respectively. The liner chosen for this investigation is a simple single-degree-of-freedom perforate liner with resonance and anti-resonance frequencies near 1.1 kHz and 2.2 kHz, respectively. The results show that the ten measurements have the most variation around the anti-resonance frequency, where statistically significant differences exist between the averaged results from the two facilities. However, the sample-to-sample variation is comparable in magnitude to the predicted cross-sectional area-dependent cavity dissipation differences between facilities, providing evidence that the size of the present samples does not significantly influence the results away from anti-resonance.

  10. Digital PIV Measurements of Acoustic Particle Displacements in a Normal Incidence Impedance Tube

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Bartram, Scott M.; Parrott, Tony L.; Jones, Michael G.

    1998-01-01

    Acoustic particle displacements and velocities inside a normal incidence impedance tube have been successfully measured for a variety of pure tone sound fields using Digital Particle Image Velocimetry (DPIV). The DPIV system utilized two 600-mj Nd:YAG lasers to generate a double-pulsed light sheet synchronized with the sound field and used to illuminate a portion of the oscillatory flow inside the tube. A high resolution (1320 x 1035 pixel), 8-bit camera was used to capture double-exposed images of 2.7-micron hollow silicon dioxide tracer particles inside the tube. Classical spatial autocorrelation analysis techniques were used to ascertain the acoustic particle displacements and associated velocities for various sound field intensities and frequencies. The results show that particle displacements spanning a range of 1-60 microns can be measured for incident sound pressure levels of 100-130 dB and for frequencies spanning 500-1000 Hz. The ability to resolve 1 micron particle displacements at sound pressure levels in the 100 dB range allows the use of DPIV systems for measurement of sound fields at much lower sound pressure levels than had been previously possible. Representative impedance tube data as well as an uncertainty analysis for the measurements are presented.

  11. A direct method for measuring acoustic ground impedance in long-range propagation experiments.

    PubMed

    Soh, Jin H; Gilbert, Kenneth E; Frazier, W M Garth; Talmadge, Carrick L; Waxler, Roger

    2010-11-01

    A method is reported for determining ground impedance in long-range propagation experiments by using the definition of impedance directly. The method is envisioned as way of measuring the impedence at multiple locations along the propagation path, using the signals broadcast during the experiment itself. In a short-range (10 m) test, the direct method was in good agreement with a more conventional model-based least-squares method. The utility of the direct method was demonstrated in a 400 m propagation experiment in a agricultural field. The resulting impedance was consistent with the impedance measured previously in the same field.

  12. Analogies between the measurement of acoustic impedance via the reaction on the source method and the automatic microwave vector network analyzer technique

    NASA Astrophysics Data System (ADS)

    McLean, James; Sutton, Robert; Post, John

    2003-10-01

    One useful method of acoustic impedance measurement involves the measurement of the electrical impedance ``looking into'' the electrical port of a reciprocal electroacoustic transducer. This reaction on the source method greatly facilitates the measurement of acoustic impedance by borrowing highly refined techniques to measure electrical impedance. It is also well suited for in situ acoustic impedance measurements. In order to accurately determine acoustic impedance from the measured electrical impedance, the characteristics of the transducer must be accurately known, i.e., the characteristics of the transducer must be ``removed'' completely from the data. The measurement of acoustic impedance via the measurement of the reaction on the source is analogous to modern microwave measurements made with an automatic vector network analyzer. The action of the analyzer is described as de-embedding the desired data (such as acoustic impedance) from the raw data. Such measurements are fundamentally substitution measurements in that the transducer's characteristics are determined by measuring a set of reference standards. The reaction on the source method is extended to take advantage of improvements in microwave measurement techniques which allow calibration via imperfect standard loads. This removes one of the principal weaknesses of the method in that the requirement of high-quality reference standards is relaxed.

  13. Measurement of cantilever vibration using impedance-loaded surface acoustic wave sensor

    NASA Astrophysics Data System (ADS)

    Oishi, Masaki; Hamashima, Hiromitsu; Kondoh, Jun

    2016-07-01

    In this study, an impedance-loaded surface acoustic wave (SAW) sensor was demonstrated to monitor the vibration frequency. Commercialized pressure sensors and a variable capacitor were chosen as external sensors, which were connected to a reflector on a SAW device. As the reflection coefficient of the reflector depended on the impedance, the echo amplitude was influenced by changes in the impedance of the external sensor. The vibration frequency of the cantilever was determined by monitoring the echo amplitude of the SAW device. Moreover, the attenuation constant of an envelope was estimated. The results of our feasibility study indicate that the impedance-loaded SAW sensor can be applied as a detector for structural health monitoring.

  14. Measured and calculated acoustic attenuation rates of tuned resonator arrays for two surface impedance distribution models with flow

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Abrahamson, A. Louis; Jones, Michael G.

    1988-01-01

    An experiment was performed to validate two analytical models for predicting low frequency attenuation of duct liner configurations built from an array of seven resonators that could be individually tuned via adjustable cavity depths. These analytical models had previously been developed for high frequency aero-engine inlet duct liner design. In the low frequency application, the liner surface impedance distribution is unavoidably spatially varying by virtue of available fabrication techniques. The characteristic length of this spatial variation may be a significant fraction of the acoustic wavelength. Comparison of measured and predicted attenuation rates and transmission losses for both modal decomposition and finite element propagation models were in good to excellent agreement for a test frequency range that included the first and second cavity resonance frequencies. This was true for either of two surface impedance distribution modeling procedures used to simplify the impedance boundary conditions. In the presence of mean flow, measurements revealed a fine scale structure of acoustic hot spots in the attenuation and phase profiles. These details were accurately predicted by the finite element model. Since no impedance changes due to mean flow were assumed, it is concluded that this fine scale structure was due to convective effects of the mean flow interacting with the surface impedance nonuniformities.

  15. Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic-impedance measurements. [Patent application

    DOEpatents

    Not Available

    1981-06-10

    Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material are presented. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material.

  16. Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements

    DOEpatents

    Langlois, Gary N.

    1983-09-13

    Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material.

  17. Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements

    DOEpatents

    Langlois, G.N.

    1983-09-13

    Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material are disclosed. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material. 6 figs.

  18. High-Frequency Acoustic Impedance Imaging of Cancer Cells.

    PubMed

    Fadhel, Muhannad N; Berndl, Elizabeth S L; Strohm, Eric M; Kolios, Michael C

    2015-10-01

    Variations in the acoustic impedance throughout cells and tissue can be used to gain insight into cellular microstructures and the physiologic state of the cell. Ultrasound imaging can be used to create a map of the acoustic impedance, on which fluctuations can be used to help identify the dominant ultrasound scattering source in cells, providing information for ultrasound tissue characterization. The physiologic state of a cell can be inferred from the average acoustic impedance values, as many cellular physiologic changes are linked to an alteration in their mechanical properties. A recently proposed method, acoustic impedance imaging, has been used to measure the acoustic impedance maps of biological tissues, but the method has not been used to characterize individual cells. Using this method to image cells can result in more precise acoustic impedance maps of cells than obtained previously using time-resolved acoustic microscopy. We employed an acoustic microscope using a transducer with a center frequency of 375 MHz to calculate the acoustic impedance of normal (MCF-10 A) and cancerous (MCF-7) breast cells. The generated acoustic impedance maps and simulations suggest that the position of the nucleus with respect to the polystyrene substrate may have an effect on the measured acoustic impedance value of the cell. Fluorescence microscopy and confocal microscopy were used to correlate acoustic impedance images with the position of the nucleus within the cell. The average acoustic impedance statistically differed between normal and cancerous breast cells (1.636 ± 0.010 MRayl vs. 1.612 ± 0.006 MRayl), indicating that acoustic impedance could be used to differentiate between normal and cancerous cells.

  19. Effects of optimized and sub-optimum two degree of freedom lining tolerances on modeled inlet acoustic attenuation and Normal incidence impedance measurement at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Burd, David R.

    This work first investigates the effect of manufacturing tolerances on realized attenuation for two degree-of-freedom linings with the use of lining models and finite element duct propagation codes. Acoustic linings were created for two turbofan engines that optimize attenuation at takeoff/sideline and approach conditions. Lining physical and geometric parameters were set, which best meet the optimum impedance requirements at two target frequencies. Similar linings were created to investigate sub-optimum designs. Variations of these parameters representing realistic manufacturing tolerances were used to systematically examine the effect on installed impedance and predicted attenuation. Attenuation at sideline and approach conditions was found to be sensitive to manufacturing tolerances around optimum conditions. The results of the study are case dependent; however the analysis scheme presented provides a method for cost-benefit analysis of manufacturing processes. In a second study, an impedance tube, with an associated data analysis method, was developed and analyzed for temperature uncertainties that allowed the measurement of impedance of acoustic samples at elevated temperatures. This impedance measurement method was validated at room temperature by comparing the results with predicted impedance from empirically based impedance models and with impedance measurements in a standard traversing microphone impedance tube. Impedance for four samples was measured at elevated temperatures, and the results were compared to room temperature measurements. For two of the samples, the impedances measured at elevated temperatures were compared to the results of extensions of room temperature empirical models, confirming the trend of the results of the elevated temperature measurements.

  20. Acoustic impedance testing for aeroacoustic applications

    NASA Astrophysics Data System (ADS)

    Schultz, Todd

    Accurate acoustic propagation models are required to characterize and subsequently reduce aircraft engine noise. These models ultimately rely on acoustic impedance measurements of candidate materials used in sound-absorbing liners. The standard two-microphone method (TMM) is widely used to estimate acoustic impedance but is limited in frequency range and does not provide uncertainty estimates, which are essential for data quality assessment and model validation. This dissertation presents a systematic framework to estimate uncertainty and extend the frequency range of acoustic impedance testing. Uncertainty estimation for acoustic impedance data using the TMM is made via two methods. The first employs a standard analytical technique based on linear perturbations and provides useful scaling information. The second uses a Monte Carlo technique that permits the propagation of arbitrarily large uncertainties. Both methods are applied to the TMM for simulated data representative of sound-hard and sound-soft acoustic materials. The results indicate that the analytical technique can lead to false conclusions about the magnitude and importance of specific error sources. Furthermore, the uncertainty in acoustic impedance is strongly dependent on the frequency and the uncertainty in the microphone locations. Next, an increased frequency range of acoustic impedance testing is investigated via two methods. The first method reduces the size of the test specimen (from 25.4 mm square to 8.5 mm square) and uses the standard TMM. This method has issues concerning specimen nonuniformity because the small specimens may not be representative of the material. The second method increases the duct cross section and, hence, the required complexity of the sound field propagation model. A comparison among all three methods is conducted for each of the three specimens: two different ceramic tubular specimens and a single degree-of-freedom liner. The results show good agreement between the

  1. Modifying the acoustic impedance of polyurea-based composites

    NASA Astrophysics Data System (ADS)

    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.

  2. Manipulate acoustic waves by impedance matched acoustic metasurfaces

    NASA Astrophysics Data System (ADS)

    Wu, Ying; Mei, Jun; Aljahdali, Rasha

    We design a type of acoustic metasurface, which is composed of carefully designed slits in a rigid thin plate. The effective refractive indices of different slits are different but the impedances are kept the same as that of the host medium. Numerical simulations show that such a metasurface can redirect or reflect a normally incident wave at different frequencies, even though it is impedance matched to the host medium. We show that the underlying mechanisms can be understood by using the generalized Snell's law, and a unified analytic model based on mode-coupling theory. We demonstrate some simple realization of such acoustic metasurface with real materials. The principle is also extended to the design of planar acoustic lens which can focus acoustic waves. Manipulate acoustic waves by impedance matched acoustic metasurfaces.

  3. Effects of Liner Geometry on Acoustic Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Tracy, Maureen B.; Watson, Willie R.; Parrott, Tony L.

    2002-01-01

    Current aircraft engine nacelles typically contain acoustic liners consisting of perforated sheets bonded onto honeycomb cavities. Numerous models have been developed to predict the acoustic impedance of these liners in the presence of grazing flow, and to use that information with aeroacoustic propagation codes to assess nacelle liner noise suppression. Recent efforts have provided advances in impedance education methodologies that offer more accurate determinations of acoustic liner properties in the presence of grazing flow. The current report provides the results of a parametric study, in which a finite element method was used to assess the effects of variations of the following geometric parameters on liner impedance, with and without the presence of grazing flow: percent open area, sheet thickness, sheet thickness-to-hole diameter ratio and cavity depth. Normal incidence acoustic impedances were determined for eight acoustic liners, consisting of punched aluminum facesheets bonded to hexcell honeycomb cavities. Similar liners were tested in the NASA Langley Research Center grazing incidence tube to determine their response in the presence of grazing flow. The resultant data provide a quantitative assessment of the effects of these perforate, single-layer liner parameters on the acoustic impedance of the liner.

  4. Method of Adjusting Acoustic Impedances for Impedance-Tunable Acoustic Segments

    NASA Technical Reports Server (NTRS)

    Jones, Kennie H (Inventor); Nark, Douglas M. (Inventor); Jones, Michael G. (Inventor); Parrott, Tony L. (Inventor); Lodding, Kenneth N. (Inventor)

    2012-01-01

    A method is provided for making localized decisions and taking localized actions to achieve a global solution. In an embodiment of the present invention, acoustic impedances for impedance-tunable acoustic segments are adjusted. A first acoustic segment through an N-th acoustic segment are defined. To start the process, the first acoustic segment is designated as a leader and a noise-reducing impedance is determined therefor. This is accomplished using (i) one or more metrics associated with the acoustic wave at the leader, and (ii) the metric(s) associated with the acoustic wave at the N-th acoustic segment. The leader, the N-th acoustic segment, and each of the acoustic segments exclusive of the leader and the N-th acoustic segment, are tuned to the noise-reducing impedance. The current leader is then excluded from subsequent processing steps. The designation of leader is then given one of the remaining acoustic segments, and the process is repeated for each of the acoustic segments through an (N-1)-th one of the acoustic segments.

  5. Comparison of Two Acoustic Waveguide Methods for Determining Liner Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie R.; Tracy, Maureen B.; Parrott, Tony L.

    2001-01-01

    Acoustic measurements taken in a flow impedance tube are used to assess the relative accuracy of two waveguide methods for impedance eduction in the presence of grazing flow. The aeroacoustic environment is assumed to contain forward and backward-traveling acoustic waves, consisting of multiple modes, and uniform mean flow. Both methods require a measurement of the complex acoustic pressure profile over the length of the test liner. The Single Mode Method assumes that the sound pressure level and phase decay-rates of a single progressive mode can be extracted from this measured complex acoustic pressure profile. No a priori assumptions are made in the Finite Element. Method regarding the modal or reflection content in the measured acoustic pressure profile. The integrity of each method is initially demonstrated by how well their no-flow impedances match those acquired in a normal incidence impedance tube. These tests were conducted using ceramic tubular and conventional perforate liners. Ceramic tubular liners were included because of their impedance insensitivity to mean flow effects. Conversely, the conventional perforate liner was included because its impedance is known to be sensitive to mean flow velocity effects. Excellent comparisons between impedance values educed with the two waveguide methods in the absence of mean flow and the corresponding values educed with the normal incident impedance tube were observed. The two methods are then compared for mean flow Mach numbers up to 0.5, and are shown to give consistent results for both types of test liners. The quality of the results indicates that the Single Mode Method should be used when the measured acoustic pressure profile is clearly dominated by a single progressive mode, and the Finite Element Method should be used for all other cases.

  6. Design and optimization of a noise reduction system for infrasonic measurements using elements with low acoustic impedance.

    PubMed

    Alcoverro, Benoit; Le Pichon, Alexis

    2005-04-01

    The implementation of the infrasound network of the International Monitoring System (IMS) for the enforcement of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) increases the effort in the design of suitable noise reducer systems. In this paper we present a new design consisting of low impedance elements. The dimensioning and the optimization of this discrete mechanical system are based on numerical simulations, including a complete electroacoustical modeling and a realistic wind-noise model. The frequency response and the noise reduction obtained for a given wind speed are compared to statistical noise measurements in the [0.02-4] Hz frequency band. The effects of the constructive parameters-the length of the pipes, inner diameters, summing volume, and number of air inlets-are investigated through a parametric study. The studied system consists of 32 air inlets distributed along an overall diameter of 16 m. Its frequency response is flat up to 4 Hz. For a 2 m/s wind speed, the maximal noise reduction obtained is 15 dB between 0.5 and 4 Hz. At lower frequencies, the noise reduction is improved by the use of a system of larger diameter. The main drawback is the high-frequency limitation introduced by acoustical resonances inside the pipes.

  7. Estimating surface acoustic impedance with the inverse method.

    PubMed

    Piechowicz, Janusz

    2011-01-01

    Sound field parameters are predicted with numerical methods in sound control systems, in acoustic designs of building and in sound field simulations. Those methods define the acoustic properties of surfaces, such as sound absorption coefficients or acoustic impedance, to determine boundary conditions. Several in situ measurement techniques were developed; one of them uses 2 microphones to measure direct and reflected sound over a planar test surface. Another approach is used in the inverse boundary elements method, in which estimating acoustic impedance of a surface is expressed as an inverse boundary problem. The boundary values can be found from multipoint sound pressure measurements in the interior of a room. This method can be applied to arbitrarily-shaped surfaces. This investigation is part of a research programme on using inverse methods in industrial room acoustics.

  8. Impedance Measurement Box

    SciTech Connect

    Morrison, William

    2014-11-20

    The IMB 50V software provides functionality for design of impedance measurement tests or sequences of tests, execution of these tests or sequences, processing measured responses and displaying and saving of the results. The software consists of a Graphical User Interface that allows configuration of measurement parameters and test sequencing, a core engine that controls test sequencing, execution of measurements, processing and storage of results and a hardware/software data acquisition interface with the IMB hardware system.

  9. Optimization and Control of Acoustic Liner Impedance with Bias Flow

    NASA Technical Reports Server (NTRS)

    Wood, Houston; Follet, Jesse

    2000-01-01

    Because communities are impacted by steady increases in aircraft traffic, aircraft noise continues to be a growing problem for the growth of commercial aviation. Research has focused on improving the design of specific high noise source areas of aircraft and on noise control measures to alleviate noise radiated from aircraft to the surrounding environment. Engine duct liners have long been a principal means of attenuating engine noise. The ability to control in-situ the acoustic impedance of a liner would provide a valuable tool to improve the performance of liners. The acoustic impedance of a liner is directly related to the sound absorption qualities of that liner. Increased attenuation rates, the ability to change liner acoustic impedance to match various operating conditions, or the ability to tune a liner to more precisely match design impedance represent some ways that in-situ impedance control could be useful. With this in mind, the research to be investigated will focus on improvements in the ability to control liner impedance using a mean flow through the liner which is referred to as bias flow.

  10. Impedance matched joined drill pipe for improved acoustic transmission

    DOEpatents

    Moss, William C.

    2000-01-01

    An impedance matched jointed drill pipe for improved acoustic transmission. A passive means and method that maximizes the amplitude and minimize the temporal dispersion of acoustic signals that are sent through a drill string, for use in a measurement while drilling telemetry system. The improvement in signal transmission is accomplished by replacing the standard joints in a drill string with joints constructed of a material that is impedance matched acoustically to the end of the drill pipe to which it is connected. Provides improvement in the measurement while drilling technique which can be utilized for well logging, directional drilling, and drilling dynamics, as well as gamma-ray spectroscopy while drilling post shot boreholes, such as utilized in drilling post shot boreholes.

  11. Differences in acoustic impedance of fresh and embedded human trabecular bone samples-Scanning acoustic microscopy and numerical evaluation.

    PubMed

    Ojanen, Xiaowei; Töyräs, Juha; Inkinen, Satu I; Malo, Markus K H; Isaksson, Hanna; Jurvelin, Jukka S

    2016-09-01

    Trabecular bone samples are traditionally embedded and polished for scanning acoustic microscopy (SAM). The effect of sample processing, including dehydration, on the acoustic impedance of bone is unknown. In this study, acoustic impedance of human trabecular bone samples (n = 8) was experimentally assessed before (fresh) and after embedding using SAM and two-dimensional (2-D) finite-difference time domain simulations. Fresh samples were polished with sandpapers of different grit (P1000, P2500, and P4000). Experimental results indicated that acoustic impedance of samples increased significantly after embedding [mean values 3.7 MRayl (fresh), 6.1 MRayl (embedded), p < 0.001]. After polishing with different papers, no significant changes in acoustic impedance were found, even though higher mean values were detected after polishing with finer (P2500 and P4000) papers. A linear correlation (r = 0.854, p < 0.05) was found between the acoustic impedance values of embedded and fresh bone samples polished using P2500 SiC paper. In numerical simulations dehydration increased the acoustic impedance of trabecular bone (38%), whereas changes in surface roughness of bone had a minor effect on the acoustic impedance (-1.56%/0.1 μm). Thereby, the numerical simulations corroborated the experimental findings. In conclusion, acoustic impedance measurement of fresh trabecular bone is possible and may provide realistic material values similar to those of living bone.

  12. Impedance Measurement Box

    ScienceCinema

    Christophersen, Jon

    2016-07-12

    Energy storage devices, primarily batteries, are now more important to consumers, industries and the military. With increasing technical complexity and higher user expectations, there is also a demand for highly accurate state-of-health battery assessment techniques. IMB incorporates patented, proprietary, and tested capabilities using control software and hardware that can be part of an embedded monitoring system. IMB directly measures the wideband impedance spectrum in seconds during battery operation with no significant impact on service life. It also can be applied to batteries prior to installation, confirming health before entering active service, as well as during regular maintenance. For more information about this project, visit http://www.inl.gov/rd100/2011/impedance-measurement-box/

  13. Simulating Reflex Induced Changes in the Acoustic Impedance of the Ear.

    ERIC Educational Resources Information Center

    Sirlin, Mindy W.; Levitt, Harry

    1991-01-01

    A simple procedure for measuring changes in the acoustic impedance of the ear is described. The technique has several applications, including simulation using a standard coupler of changes in real ear impedance produced by the acoustic reflex, and calibration of response time of an otoadmittance meter. (Author/DB)

  14. Thermal Boundary Resistance between GaN and Cubic Ice and THz Acoustic Attenuation Spectrum of Cubic Ice from Complex Acoustic Impedance Measurements.

    PubMed

    Mante, Pierre-Adrien; Chen, Chien-Cheng; Wen, Yu-Chieh; Sheu, Jinn-Kong; Sun, Chi-Kuang

    2013-11-27

    A phonon nanoscopy method, based on the picosecond ultrasonics technique, capable of studying the complex acoustic reflection coefficient at frequency up to 1 THz is proposed and demonstrated. By measuring the reflection coefficient at the same surface location at the interface between GaN and air, and between GaN and the material to characterize, we get access to the THz amplitude and phase spectra of the acoustic phonon reflection. The retrieval of both these pieces of information then allows the calculation of the attenuation in a wide range of frequency and gives new insight into the Kapitza anomaly. This method is then applied to cubic ice, and the measurements of the elastic properties, the phonon anharmonic decay spectrum up to 1 THz, as well as the measurements of the thermal phonon lifetime at 150 K are all achieved.

  15. Monolithically compatible impedance measurement

    DOEpatents

    Ericson, Milton Nance; Holcomb, David Eugene

    2002-01-01

    A monolithic sensor includes a reference channel and at least one sensing channel. Each sensing channel has an oscillator and a counter driven by the oscillator. The reference channel and the at least one sensing channel being formed integrally with a substrate and intimately nested with one another on the substrate. Thus, the oscillator and the counter have matched component values and temperature coefficients. A frequency determining component of the sensing oscillator is formed integrally with the substrate and has an impedance parameter which varies with an environmental parameter to be measured by the sensor. A gating control is responsive to an output signal generated by the reference channel, for terminating counting in the at least one sensing channel at an output count, whereby the output count is indicative of the environmental parameter, and successive ones of the output counts are indicative of changes in the environmental parameter.

  16. Fluid mechanical model of the acoustic impedance of small orifices

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Rogers, T.

    1976-01-01

    A fluid mechanical model of the acoustic behavior of small orifices is presented which predicts orifice resistance and reactance as a function of incident sound pressure level, frequency, and orifice geometry. Agreement between predicted and measured values is excellent. The model shows the following: (1) The acoustic flow in immediate neighborhood of the orifice can be modeled as a locally spherical flow. Within this near field, the flow is, to a first approximation, unsteady and incompressible. (2) At very low sound pressure levels, the orifice viscous resistance is directly related to the effect of boundary-layer displacement along the walls containing the orifice, and the orifice reactance is directly related to the inertia of the oscillating flow in the neighborhood of the orifice. (3) For large values of the incident acoustic pressure, the impedance is dominated by nonlinear jet-like effects. (4) For low values of the pressure, the resistance and reactance are roughly equal.

  17. Manipulating acoustic wavefront by inhomogeneous impedance and steerable extraordinary reflection.

    PubMed

    Zhao, Jiajun; Li, Baowen; Chen, Zhining; Qiu, Cheng-Wei

    2013-01-01

    We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

  18. Manipulating Acoustic Wavefront by Inhomogeneous Impedance and Steerable Extraordinary Reflection

    PubMed Central

    Zhao, Jiajun; Li, Baowen; Chen, Zhining; Qiu, Cheng-Wei

    2013-01-01

    We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators. PMID:23985717

  19. Development of an Acoustic Impedance Tube Testbed for Material Sample Testing

    NASA Technical Reports Server (NTRS)

    Doty, Benjamin J.; Kolaini, Ali R.

    2012-01-01

    Acoustic impedance tube method: uses Traveling wave amplitudes are measured on either side of a sample in a tube. Many acoustic properties of the sample can be calculated. It is Simple and inexpensive to set up, ideal for high volume optimization tests

  20. Tests Of Shear-Flow Model For Acoustic Impedance

    NASA Technical Reports Server (NTRS)

    Parrot, Tony L.; Watson, Willie R.; Jones, Michael G.

    1992-01-01

    Tests described in report conducted to validate two-dimensional shear-flow analytical model for determination of acoustic impedance of acoustic liner in grazing-incidence, grazing-flow environment by use of infinite-waveguide method. Tests successful for both upstream and downstream propagations. Work has potential for utility in testing of engine ducts in commercial aircraft.

  1. Matching Impedances and Modes in Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.

    1985-01-01

    Temperature differences accommodated with tunable coupler. Report discusses schemes for coupling sound efficiently from cool outside atmosphere into hot acoustic-levitation chamber. Theoretical studies have practical implications for material-processing systems that employ acoustic levitation.

  2. High transmission acoustic focusing by impedance-matched acoustic meta-surfaces

    NASA Astrophysics Data System (ADS)

    Al Jahdali, Rasha; Wu, Ying

    2016-01-01

    Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.

  3. Validation of an Acoustic Impedance Prediction Model for Skewed Resonators

    NASA Technical Reports Server (NTRS)

    Howerton, Brian M.; Parrott, Tony L.

    2009-01-01

    An impedance prediction model was validated experimentally to determine the composite impedance of a series of high-aspect ratio slot resonators incorporating channel skew and sharp bends. Such structures are useful for packaging acoustic liners into constrained spaces for turbofan noise control applications. A formulation of the Zwikker-Kosten Transmission Line (ZKTL) model, incorporating the Richards correction for rectangular channels, is used to calculate the composite normalized impedance of a series of six multi-slot resonator arrays with constant channel length. Experimentally, acoustic data was acquired in the NASA Langley Normal Incidence Tube over the frequency range of 500 to 3500 Hz at 120 and 140 dB OASPL. Normalized impedance was reduced using the Two-Microphone Method for the various combinations of channel skew and sharp 90o and 180o bends. Results show that the presence of skew and/or sharp bends does not significantly alter the impedance of a slot resonator as compared to a straight resonator of the same total channel length. ZKTL predicts the impedance of such resonators very well over the frequency range of interest. The model can be used to design arrays of slot resonators that can be packaged into complex geometries heretofore unsuitable for effective acoustic treatment.

  4. Input impedance matching of acoustic transducers operating at off-resonant frequencies.

    PubMed

    Son, Kyu Tak; Lee, Chin C

    2010-12-01

    The input impedance matching technique of acoustic transducers at off-resonant frequencies is reported. It uses an inherent impedance property of transducers and thus does not need an external electric matching circuit or extra acoustic matching section. The input electrical equivalent circuit includes a radiation component and a dielectric capacitor. The radiation component consists of a radiation resistance and a radiation reactance. The total reactance is the sum of the radiation reactance and the dielectric capacitive reactance. This reactance becomes zero at two frequencies where the impedance is real. The transducer size can be properly chosen so that the impedance at one of the zero-crossing frequencies is close to 50 Ω, the output impedance of signal generators. At this off-resonant operating frequency, the reflection coefficient of the transducer is minimized without using any matching circuit. Other than the size, the impedance can also be fine tuned by adjusting the thickness of material that bonds the transducer plate to the substrates. The acoustic impedance of the substrate and that of the bonding material can also be used as design elements in the transducer structure to achieve better transducer matching. Lead titanate piezoelectric plates were bonded on Lucite, liquid crystal polymer (LCP), and bismuth (Bi) substrates to produce various transducer structures. Their input impedance was simulated using a transducer model and compared with measured values to illustrate the matching principle.

  5. Duct wall impedance control as an advanced concept for acoustic impression

    NASA Technical Reports Server (NTRS)

    Dean, P. D.; Tester, B. J.

    1975-01-01

    Models and tests on an acoustic duct liner system which has the property of controlled-variable acoustic impedance are described. This is achieved by a novel concept which uses the effect of steady air flow through a multi-layer, locally reacting, resonant-cavity absorber. The scope of this work was limited to a 'proof of concept.' The test of the concept was implemented by means of a small-scale, square-section flow duct facility designed specifically for acoustic measurements, with one side of the duct acoustically lined. The test liners were designed with the aid of previously established duct acoustic theory and a semi-empirical impedance model of the liner system. Over the limited range tested, the liner behaved primarily as predicted, exhibiting significant changes in resistance and reactance, thus providing the necessary concept validation.

  6. Sputtered SiO2 as low acoustic impedance material for Bragg mirror fabrication in BAW resonators.

    PubMed

    Olivares, Jimena; Wegmann, Enrique; Capilla, José; Iborra, Enrique; Clement, Marta; Vergara, Lucía; Aigner, Robert

    2010-01-01

    In this paper we describe the procedure to sputter low acoustic impedance SiO(2) films to be used as a low acoustic impedance layer in Bragg mirrors for BAW resonators. The composition and structure of the material are assessed through infrared absorption spectroscopy. The acoustic properties of the films (mass density and sound velocity) are assessed through X-ray reflectometry and picosecond acoustic spectroscopy. A second measurement of the sound velocity is achieved through the analysis of the longitudinal lambda/2 resonance that appears in these silicon oxide films when used as uppermost layer of an acoustic reflector placed under an AlN-based resonator.

  7. Duct wall impedance control as an advanced concept for acoustic suppression enhancement. [engine noise reduction

    NASA Technical Reports Server (NTRS)

    Dean, P. D.

    1978-01-01

    A systems concept procedure is described for the optimization of acoustic duct liner design for both uniform and multisegment types. The concept was implemented by the use of a double reverberant chamber flow duct facility coupled with sophisticated computer control and acoustic analysis systems. The optimization procedure for liner insertion loss was based on the concept of variable liner impedance produced by bias air flow through a multilayer, resonant cavity liner. A multiple microphone technique for in situ wall impedance measurements was used and successfully adapted to produce automated measurements for all liner configurations tested. The complete validation of the systems concept was prevented by the inability to optimize the insertion loss using bias flow induced wall impedance changes. This inability appeared to be a direct function of the presence of a higher order energy carrying modes which were not influenced significantly by the wall impedance changes.

  8. Improved phonocardiogram system based on acoustic impedance matching.

    PubMed

    Schwartz, R S; Reeves, J T; Sodal, I E; Barnes, F S

    1980-04-01

    We considered that phonocardiographic recording could be improved 1) by minimizing the acoustic impedance mismatch between the precordial tissue and transducer, 2) by optimizing the configuration of the impedance-matching medium and transducer design, and 3) by storing signals in digital form through analog-to-digital conversion of analog recordings made at the bedside. The use of an aqueous coupling medium to improve energy transmission increased signal voltage approximately 100-fold over presently used commercial devices. Further match to the crystal was achieved by a concentrating horn configuration for the aqueous medium. Measured frequency response of the device in the range 1 Hz to 1 kHz was better than two other commercially tested microphones. Inspection of comparative phonocardiograms showed more information from the new device than from the two other commercial devices. Unfiltered digitized signals, using our microphone in normal subjects, demonstrated good beat-to-beat repeatability, but analog filtering to obtain the conventional phonocardiogram showed significant loss of information. The new instrument appears to be superior to those commercial devices tested in recording heart sounds.

  9. Effects of Flow Profile on Educed Acoustic Liner Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie r.; Nark, Douglas M.

    2010-01-01

    This paper presents results of an investigation of the effects of shear flow profile on impedance eduction processes employed at NASA Langley. Uniform and 1-D shear-flow propagation models are used to educe the acoustic impedance of three test liners based on aeroacoustic data acquired in the Langley Grazing Flow Impedance Tube, at source levels of 130, 140 and 150 dB, and at centerline Mach numbers of 0.0, 0.3 and 0.5. A ceramic tubular, calibration liner is used to evaluate the propagation models, as this liner is expected to be insensitive to SPL, grazing flow Mach number, and flow profile effects. The propagation models are then used to investigate the effects of shear flow profile on acoustic impedances educed for two conventional perforate-over-honeycomb liners. Results achieved with the uniform-flow models follow expected trends, but those educed with the 1-D shear-flow model do not, even for the calibration liner. However, when the flow profile used with the shear-flow model is varied to increase the Mach number gradient near the wall, results computed with the shear-flow model are well matched to those achieved with the uniform-flow model. This indicates the effects of flow profile on educed acoustic liner impedance are small, but more detailed investigations of the flow field throughout the duct are needed to better understand these effects.

  10. Appraisal of broadband acoustic impedances from first principles and band-limited seismic reflection data

    NASA Astrophysics Data System (ADS)

    Mandal, A.; Ghosh, S. K.

    2015-12-01

    Seismic derived acoustic impedance is an essential output for the quantitative interpretation of seismic data. However, the band limitation of seismic data leads to a nonunique estimate of the acoustic impedance profile. The prevalent methods counter the nonuniqueness either by stabilizing the answer with respect to an initial model or by resorting to an assumption of certain criterion such as sparsity of the reflection coefficients. Making a nominal assumption of a homogeneous layered earth model, we formulate a set of linear equations where the reflection coefficients are the unknowns and the recursively integrated seismic trace constitutes the data. The approach makes a frontal assault on the problem of reconstructing reflection coefficients from band-limited data and stems from first principles, i.e., Zöppritz's equation in this case. Nonuniqueness is countered in part by the layercake assumption, and in part by the adoption of the singular value decomposition (SVD) method of finding an optimal solution to the set of linear equations, provided the objective is to reconstruct a smoothed version of the impedance profile that includes only its coarser structures. The efficacy of the method has been tested with synthetic data added with significant noise and generated from rudimentary earth models as well as from measured logs of acoustic impedance. Emergence of consistent estimates of impedance from synthetic data generated for several frequency bands increases the confidence in the method. The study also proves the successfulness of the method for (a) an accurate estimate of the impedance mean, (b) an accurate reconstruction of the direct-current (dc) frequency of the reflectivity, and (c) an acceptable reconstruction of the broad trend of the original impedance profile. All these outputs can serve as significant constraints for either more refined inversions or geological interpretations. (Keywords: Reflection data, Acoustic impedance, Broadband, Linear

  11. Air-ground interface: Surface waves, surface impedance and acoustic-to-seismic coupling coefficient

    NASA Technical Reports Server (NTRS)

    Daigle, Gilles; Embleton, Tony

    1990-01-01

    In atmospheric acoustics, the subject of surface waves has been an area of discussion for many years. The existence of an acoustic surface wave is now well established theoretically. The mathematical solution for spherical wave propagation above an impedance boundary includes the possibility of a contribution that possesses all the standard properties for a surface wave. Surface waves exist when the surface is sufficiently porous, relative to its acoustical resistance, that it can influence the airborne particle velocity near the surface and reduce the phase velocity of sound waves in air at the surface. This traps some of the sound energy in the air to remain near the surface as it propagates. Above porous grounds, the existence of surface waves has eluded direct experimental confirmation (pulse experiments have failed to show a separate arrival expected from the reduced phase speed) and indirect evidence for its existence has appeared contradictory. The experimental evidence for the existence of an acoustical surface wave above porous boundaries is reviewed. Recent measurements including pulse experiments are also described. A few years ago the acoustic impedance of a grass-covered surface was measured in the frequency range 30 to 300 Hz. Here, further measurements on the same site are discussed. These measurements include core samples, a shallow refractive survey to determine the seismic velocities, and measurements of the acoustic-to-seismic coupling coefficient.

  12. Experimental validation of a two-dimensional shear-flow model for determining acoustic impedance

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Watson, Willie R.; Jones, Michael G.

    1987-01-01

    Tests were conducted to validate a two-dimensional shear-flow analytical model for determining the acoustic impedance of a liner test specimen in a grazing-incidence, grazing-flow environment. The tests were limited to a test specimen chosen to exhibit minimal effects of grazing flow so that the results obtained by using the shear-flow analytical model would be expected to match those obtained from normal-incidence impedance measurements. Impedances for both downstream and upstream sound propagation were generally consistent with those from normal-incidence measurements. However, sensitivity of the grazing-incidence impedance to small measurement or systematic errors in propagation constant varied dramatically over the range of test frequencies.

  13. Acoustic measurements of articulator motions.

    PubMed

    Schroeder, M R; Strube, H W

    1979-01-01

    Methods for estimating articulatory data from acoustic measurements are reviewed. First, relations between the vocal-tract area function and formant or impedance data are pointed out. Then the possibility of determining a (discretized) area function from the speech signal itself is considered. Finally, we look at the estimation of certain articulatory parameters rather than the area function. By using a regression method, such parameters can even be estimated independently of any vocal-tract model. Results for real-speech data are given.

  14. Numerical analysis of acoustic impedance microscope utilizing acoustic lens transducer to examine cultured cells.

    PubMed

    Gunawan, Agus Indra; Hozumi, Naohiro; Takahashi, Kenta; Yoshida, Sachiko; Saijo, Yoshifumi; Kobayashi, Kazuto; Yamamoto, Seiji

    2015-12-01

    A new technique is proposed for non-contact quantitative cell observation using focused ultrasonic waves. This technique interprets acoustic reflection intensity into the characteristic acoustic impedance of the biological cell. The cells are cultured on a plastic film substrate. A focused acoustic beam is transmitted through the substrate to its interface with the cell. A two-dimensional (2-D) reflection intensity profile is obtained by scanning the focal point along the interface. A reference substance is observed under the same conditions. These two reflections are compared and interpreted into the characteristic acoustic impedance of the cell based on a calibration curve that was created prior to the observation. To create the calibration curve, a numerical analysis of the sound field is performed using Fourier Transforms and is verified using several saline solutions. Because the cells are suspended by two plastic films, no contamination is introduced during the observation. In a practical observation, a sapphire lens transducer with a center frequency of 300 MHz was employed using ZnO thin film. The objects studied were co-cultured rat-derived glial (astrocyte) cells and glioma cells. The result was the clear observation of the internal structure of the cells. The acoustic impedance of the cells was spreading between 1.62 and 1.72 MNs/m(3). Cytoskeleton was indicated by high acoustic impedance. The introduction of cytochalasin-B led to a significant reduction in the acoustic impedance of the glioma cells; its effect on the glial cells was less significant. It is believed that this non-contact observation method will be useful for continuous cell inspections.

  15. Alignment of an acoustic manipulation device with cepstral analysis of electronic impedance data.

    PubMed

    Hughes, D A; Qiu, Y; Démoré, C; Weijer, C J; Cochran, S

    2015-02-01

    Acoustic particle manipulation is an emerging technology that uses ultrasonic standing waves to position objects with pressure gradients and acoustic radiation forces. To produce strong standing waves, the transducer and the reflector must be aligned properly such that they are parallel to each other. This can be a difficult process due to the need to visualise the ultrasound waves and as higher frequencies are introduced, this alignment requires higher accuracy. In this paper, we present a method for aligning acoustic resonators with cepstral analysis. This is a simple signal processing technique that requires only the electrical impedance measurement data of the resonator, which is usually recorded during the fabrication process of the device. We first introduce the mathematical basis of cepstral analysis and then demonstrate and validate it using a computer simulation of an acoustic resonator. Finally, the technique is demonstrated experimentally to create many parallel linear traps for 10 μm fluorescent beads inside an acoustic resonator.

  16. Evaluation of a multi-point method for determining acoustic impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Parrott, Tony L.

    1988-01-01

    An investigation was conducted to explore potential improvements provided by a Multi-Point Method (MPM) over the Standing Wave Method (SWM) and Two-Microphone Method (TMM) for determining acoustic impedance. A wave propagation model was developed to model the standing wave pattern in an impedance tube. The acoustic impedance of a test specimen was calculated from a best fit of this standing wave pattern to pressure measurements obtained along the impedance tube centerline. Three measurement spacing distributions were examined: uniform, random, and selective. Calculated standing wave patterns match the point pressure measurement distributions with good agreement for a reflection factor magnitude range of 0.004 to 0.999. Comparisons of results using 2, 3, 6, and 18 measurement points showed that the most consistent results are obtained when using at least 6 evenly spaced pressure measurements per half-wavelength. Also, data were acquired with broadband noise added to the discrete frequency noise and impedances were calculated using the MPM and TMM algorithms. The results indicate that the MPM will be superior to the TMM in the presence of significant broadband noise levels associated with mean flow.

  17. Acoustic Impedance Analysis with High-Frequency Ultrasound for Identification of Fatty Acid Species in the Liver.

    PubMed

    Ito, Kazuyo; Yoshida, Kenji; Maruyama, Hitoshi; Mamou, Jonathan; Yamaguchi, Tadashi

    2017-03-01

    Acoustic properties of free fatty acids present in the liver were studied as a possible basis for non-invasive ultrasonic diagnosis of non-alcoholic steatohepatitis. Acoustic impedance was measured for the following types of tissue samples: Four pathologic types of mouse liver, five kinds of FFAs in solvent and five kinds of FFAs in cultured Huh-7 cells. A transducer with an 80-MHz center frequency was incorporated into a scanning acoustic microscopy system. Acoustic impedance was calculated from the amplitude of the signal reflected from the specimen surface. The Kruskal-Wallis test revealed statistically significant differences (p < 0.01) in acoustic impedance not only among pathologic types, but also among the FFAs in solvent and in cultured Huh-7 cells. These results suggest that each of the FFAs, especially palmitate, oleate and palmitoleate acid, can be distinguished from each other, regardless of whether they were in solution or absorbed by cells.

  18. A state feedback electro-acoustic transducer for active control of acoustic impedance.

    PubMed

    Samejima, Toshiya

    2003-03-01

    In this paper, a new control system in which the acoustic impedance of an electro-acoustic transducer diaphragm can be actively varied by modifying design parameters is presented and its effectiveness is theoretically investigated. The proposed control system is based on a state-space description of the control system derived from an electrical equivalent circuit of an electro-acoustic transducer to which a differentiating circuit is connected, and is designed using modem control theory. The optimal quadratic regulator is used in the control system design, with its quadratic performance index formulated for producing desired acoustic impedance. Computer simulations indicate that the acoustic impedance of the diaphragm can be significantly varied over a wide frequency range that includes the range below the resonance frequency of the electro-acoustic transducer. A computer model of the proposed control system is used to illustrate its application to semi-active noise control in a duct. It is demonstrated that the proposed control system provides substantial reductions in the noise radiating from the outlet of the duct, both in the stiffness control range and in the mass control range.

  19. Evaluation of Parallel-Element, Variable-Impedance, Broadband Acoustic Liner Concepts

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Howerton, Brian M.; Ayle, Earl

    2012-01-01

    Recent trends in aircraft engine design have highlighted the need for acoustic liners that provide broadband sound absorption with reduced liner thickness. Three such liner concepts are evaluated using the NASA normal incidence tube. Two concepts employ additive manufacturing techniques to fabricate liners with variable chamber depths. The first relies on scrubbing losses within narrow chambers to provide acoustic resistance necessary for sound absorption. The second employs wide chambers that provide minimal resistance, and relies on a perforated sheet to provide acoustic resistance. The variable-depth chambers used in both concepts result in reactance spectra near zero. The third liner concept employs mesh-caps (resistive sheets) embedded at variable depths within adjacent honeycomb chambers to achieve a desired impedance spectrum. Each of these liner concepts is suitable for use as a broadband sound absorber design, and a transmission line model is presented that provides good comparison with their respective acoustic impedance spectra. This model can therefore be used to design acoustic liners to accurately achieve selected impedance spectra. Finally, the effects of increasing the perforated facesheet thickness are demonstrated, and the validity of prediction models based on lumped element and wave propagation approaches is investigated. The lumped element model compares favorably with measured results for liners with thin facesheets, but the wave propagation model provides good comparisons for a wide range of facesheet thicknesses.

  20. Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow

    NASA Astrophysics Data System (ADS)

    Troian, Renata; Dragna, Didier; Bailly, Christophe; Galland, Marie-Annick

    2017-03-01

    A new broadband impedance eduction method is introduced to identify the surface impedance of acoustic liners from in situ measurements on a test rig. Multimodal acoustic propagation is taken into account in order to reproduce realistic conditions. The present approach is based on the resolution of the linearized 3D Euler equations in the time domain. The broadband impedance time domain boundary condition is prescribed from a multipole impedance model, and is formulated as a differential form well-suited for high-order numerical methods. Numerical values of the model coefficients are determined by minimizing the difference between measured and simulated acoustic quantities, namely the insertion loss and wall pressure fluctuations at a few locations inside the duct. The minimization is performed through a multi-objective optimization thanks to the Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The present eduction method is validated with benchmark data provided by NASA for plane wave propagation, and by synthesized numerical data for multimodal propagation.

  1. A finite element propagation model for extracting normal incidence impedance in nonprogressive acoustic wave fields

    NASA Astrophysics Data System (ADS)

    Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.

    1995-04-01

    A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme was computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressirve wave environment such as that usually encountered in a commercial aircraft engine and most laboratory settings.

  2. A Finite Element Propagation Model for Extracting Normal Incidence Impedance in Nonprogressive Acoustic Wave Fields

    NASA Astrophysics Data System (ADS)

    Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.

    1996-04-01

    A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme were computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressive wave environment such as that usually encountered in a commercial aircraft engine and in most laboratory settings.

  3. Acoustic Treatment Design Scaling Methods. Volume 2; Advanced Treatment Impedance Models for High Frequency Ranges

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.; Yu, J.; Kwan, H. W.

    1999-01-01

    The primary purpose of this study is to develop improved models for the acoustic impedance of treatment panels at high frequencies, for application to subscale treatment designs. Effects that cause significant deviation of the impedance from simple geometric scaling are examined in detail, an improved high-frequency impedance model is developed, and the improved model is correlated with high-frequency impedance measurements. Only single-degree-of-freedom honeycomb sandwich resonator panels with either perforated sheet or "linear" wiremesh faceplates are considered. The objective is to understand those effects that cause the simple single-degree-of- freedom resonator panels to deviate at the higher-scaled frequency from the impedance that would be obtained at the corresponding full-scale frequency. This will allow the subscale panel to be designed to achieve a specified impedance spectrum over at least a limited range of frequencies. An advanced impedance prediction model has been developed that accounts for some of the known effects at high frequency that have previously been ignored as a small source of error for full-scale frequency ranges.

  4. Measuring acoustic habitats.

    PubMed

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-03-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies.

  5. Measuring acoustic habitats

    PubMed Central

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-01-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies. PMID:25954500

  6. Sensing the characteristic acoustic impedance of a fluid utilizing acoustic pressure waves

    PubMed Central

    Antlinger, Hannes; Clara, Stefan; Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard

    2012-01-01

    Ultrasonic sensors can be used to determine physical fluid parameters like viscosity, density, and speed of sound. In this contribution, we present the concept for an integrated sensor utilizing pressure waves to sense the characteristic acoustic impedance of a fluid. We note that the basic setup generally allows to determine the longitudinal viscosity and the speed of sound if it is operated in a resonant mode as will be discussed elsewhere. In this contribution, we particularly focus on a modified setup where interferences are suppressed by introducing a wedge reflector. This enables sensing of the liquid's characteristic acoustic impedance, which can serve as parameter in condition monitoring applications. We present a device model, experimental results and their evaluation. PMID:23565036

  7. Structural health monitoring using piezoelectric impedance measurements.

    PubMed

    Park, Gyuhae; Inman, Daniel J

    2007-02-15

    This paper presents an overview and recent advances in impedance-based structural health monitoring. The basic principle behind this technique is to apply high-frequency structural excitations (typically greater than 30kHz) through surface-bonded piezoelectric transducers, and measure the impedance of structures by monitoring the current and voltage applied to the piezoelectric transducers. Changes in impedance indicate changes in the structure, which in turn can indicate that damage has occurred. An experimental study is presented to demonstrate how this technique can be used to detect structural damage in real time. Signal processing methods that address damage classifications and data compression issues associated with the use of the impedance methods are also summarized. Finally, a modified frequency-domain autoregressive model with exogenous inputs (ARX) is described. The frequency-domain ARX model, constructed by measured impedance data, is used to diagnose structural damage with levels of statistical confidence.

  8. Wireless Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Anderson, Paul D.; Dorland, Wade D.

    2005-01-01

    A prototype wireless acoustic measurement system (WAMS) is one of two main subsystems of the Acoustic Prediction/Measurement Tool, which comprises software, acoustic instrumentation, and electronic hardware combined to afford integrated capabilities for predicting and measuring noise emitted by rocket and jet engines. The other main subsystem is described in "Predicting Rocket or Jet Noise in Real Time" (SSC-00215-1), which appears elsewhere in this issue of NASA Tech Briefs. The WAMS includes analog acoustic measurement instrumentation and analog and digital electronic circuitry combined with computer wireless local-area networking to enable (1) measurement of sound-pressure levels at multiple locations in the sound field of an engine under test and (2) recording and processing of the measurement data. At each field location, the measurements are taken by a portable unit, denoted a field station. There are ten field stations, each of which can take two channels of measurements. Each field station is equipped with two instrumentation microphones, a micro-ATX computer, a wireless network adapter, an environmental enclosure, a directional radio antenna, and a battery power supply. The environmental enclosure shields the computer from weather and from extreme acoustically induced vibrations. The power supply is based on a marine-service lead-acid storage battery that has enough capacity to support operation for as long as 10 hours. A desktop computer serves as a control server for the WAMS. The server is connected to a wireless router for communication with the field stations via a wireless local-area network that complies with wireless-network standard 802.11b of the Institute of Electrical and Electronics Engineers. The router and the wireless network adapters are controlled by use of Linux-compatible driver software. The server runs custom Linux software for synchronizing the recording of measurement data in the field stations. The software includes a module that

  9. Wireless Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Anderson, Paul D.; Dorland, Wade D.; Jolly, Ronald L.

    2007-01-01

    A prototype wireless acoustic measurement system (WAMS) is one of two main subsystems of the Acoustic Prediction/ Measurement Tool, which comprises software, acoustic instrumentation, and electronic hardware combined to afford integrated capabilities for predicting and measuring noise emitted by rocket and jet engines. The other main subsystem is described in the article on page 8. The WAMS includes analog acoustic measurement instrumentation and analog and digital electronic circuitry combined with computer wireless local-area networking to enable (1) measurement of sound-pressure levels at multiple locations in the sound field of an engine under test and (2) recording and processing of the measurement data. At each field location, the measurements are taken by a portable unit, denoted a field station. There are ten field stations, each of which can take two channels of measurements. Each field station is equipped with two instrumentation microphones, a micro- ATX computer, a wireless network adapter, an environmental enclosure, a directional radio antenna, and a battery power supply. The environmental enclosure shields the computer from weather and from extreme acoustically induced vibrations. The power supply is based on a marine-service lead-acid storage battery that has enough capacity to support operation for as long as 10 hours. A desktop computer serves as a control server for the WAMS. The server is connected to a wireless router for communication with the field stations via a wireless local-area network that complies with wireless-network standard 802.11b of the Institute of Electrical and Electronics Engineers. The router and the wireless network adapters are controlled by use of Linux-compatible driver software. The server runs custom Linux software for synchronizing the recording of measurement data in the field stations. The software includes a module that provides an intuitive graphical user interface through which an operator at the control server

  10. Waveform-preserved unidirectional acoustic transmission based on impedance-matched acoustic metasurface and phononic crystal

    NASA Astrophysics Data System (ADS)

    Song, Ai-Ling; Chen, Tian-Ning; Wang, Xiao-Peng; Wan, Le-Le

    2016-08-01

    The waveform distortion happens in most of the unidirectional acoustic transmission (UAT) devices proposed before. In this paper, a novel type of waveform-preserved UAT device composed of an impedance-matched acoustic metasurface (AMS) and a phononic crystal (PC) structure is proposed and numerically investigated. The acoustic pressure field distributions and transmittance are calculated by using the finite element method. The subwavelength AMS that can modulate the wavefront of the transmitted wave at will is designed and the band structure of the PC structure is calculated and analyzed. The sound pressure field distributions demonstrate that the unidirectional acoustic transmission can be realized by the proposed UAT device without changing the waveforms of the output waves, which is the distinctive feature compared with the previous UAT devices. The physical mechanism of the unidirectional acoustic transmission is discussed by analyzing the refraction angle changes and partial band gap map. The calculated transmission spectra show that the UAT device is valid within a relatively broad frequency range. The simulation results agree well with the theoretical predictions. The proposed UAT device provides a good reference for designing waveform-preserved UAT devices and has potential applications in many fields, such as medical ultrasound, acoustic rectifiers, and noise insulation.

  11. Bonding and impedance matching of acoustic transducers using silver epoxy.

    PubMed

    Son, Kyu Tak; Lee, Chin C

    2012-04-01

    Silver epoxy was selected to bond transducer plates on glass substrates. The properties and thickness of the bonding medium affect the electrical input impedance of the transducer. Thus, the thickness of the silver epoxy bonding layer was used as a design parameter to optimize the structure for the transducer input impedance to match the 50 Ω output impedance of most radio frequency (RF) generators. Simulation and experimental results show that nearly perfect matching is achieved without using any matching circuit. At the matching condition, the transducer operates at a frequency band a little bit below the half-wavelength resonant frequency of the piezoelectric plate. In experiments, lead titanate (PT) piezoelectric plates were employed. Both full-size, 11.5 mm × 2 mm × 0.4 mm, and half-size, 5.75 mm × 2 mm × 0.4 mm, can be well matched using optimal silver epoxy thickness. The transducer assemblies demonstrate high efficiency. The conversion loss from electrical power to acoustic power in soda-lime glass is 4.3 dB. This loss is low considering the fact that the transducers operate at off-resonance by 12%. With proper choice of silver epoxy thickness, the transducer can be matched at the fundamental, the 3rd and 5th harmonic frequencies. This leads to the possible realization of triple-band transducers. Reliability was assessed with thermal cycling test according to Telcordia GR-468-Core recommendation. Of the 30 transducer assemblies tested, none broke until 2900 cycles and 27 have sustained beyond 4050 cycles.

  12. Gas hydrate saturation from acoustic impedance and resistivity logs in the shenhu area, south china sea

    USGS Publications Warehouse

    Wang, X.; Wu, S.; Lee, M.; Guo, Y.; Yang, S.; Liang, J.

    2011-01-01

    During the China's first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ???10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity. ?? 2011 Elsevier Ltd.

  13. Characterizing the ear canal acoustic impedance and reflectance by pole-zero fitting.

    PubMed

    Robinson, Sarah R; Nguyen, Cac T; Allen, Jont B

    2013-07-01

    This study characterizes middle ear complex acoustic reflectance (CAR) and impedance by fitting poles and zeros to real-ear measurements. The goal of this work is to establish a quantitative connection between pole-zero locations and the underlying physical properties of CAR data. Most previous studies have analyzed CAR magnitude; while the magnitude accounts for reflected power, it does not encode latency information. Thus, an analysis that studies the real and imaginary parts of the data together, being more general, should be more powerful. Pole-zero fitting of CAR data is examined using data compiled from various studies, dating back to Voss and Allen (1994). Recent CAR measurements were taken using the Mimosa Acoustics HearID system, which makes complex acoustic impedance and reflectance measurements in the ear canal over a 0.2-6.0 [kHz] frequency range. Pole-zero fits to measurements over this range are achieved with an average RMS relative error of less than 3% with 12 poles. Factoring the reflectance fit into its all-pass and minimum-phase components estimates the effect of the residual ear canal, allowing for comparison of the eardrum impedance and admittance across measurements. It was found that individual CAR magnitude variations for normal middle ears in the 1-4 [kHz] range often give rise to closely-placed pole-zero pairs, and that the locations of the poles and zeros in the s-plane may systematically differ between normal and pathological middle ears. This study establishes a methodology for examining the physical and mathematical properties of CAR using a concise parametric model. Pole-zero modeling accurately parameterizes CAR data, providing a foundation for detection and identification of middle ear pathologies. This article is part of a special issue entitled "MEMRO 2012".

  14. Effects of grazing flow on the steady-state flow resistance and acoustic impedance of thin porous-faced liners

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Walker, B.

    1978-01-01

    The effects of grazing flow on the steady state flow resistance and acoustic impedance of seven Feltmetal and three Rigimesh thin porous faced liners were studied. The steady-state flow resistance of the ten specimens was measured using standard fluid mechanical experimental techniques. The acoustic impedance was measured using the two microphone method. The principal findings of the study are that the effects of grazing flow were measured and found to be small; small differences were measured between steady-state and acoustic resistance, and a semi-empirical model was derived that correlated the steady-state resistance data of the seven Feltmetal liners and the face sheet reactance of both the Feltmetal and Rigimesh liners.

  15. Reflectance measurement validation using acoustic horns

    PubMed Central

    Rasetshwane, Daniel M.; Neely, Stephen T.

    2015-01-01

    Variability in wideband acoustic reflectance (and absorbance) measurements adversely affects the clinical utility of reflectance for diagnosis of middle-ear disorders. A reflectance standard would encourage consistency across different measurement systems and help identify calibration related issues. Theoretical equations exist for the reflectance of finite-length exponential, conical, and parabolic acoustic horns. Reflectance measurements were repeatedly made in each of these three horn shapes and the results were compared to the corresponding theoretical reflectance. A method is described of adjusting acoustic impedance measurements to compensate for spreading of the wave front that propagates from the small diameter sound port of the probe to the larger diameter of the acoustic cavity. Agreement between measured and theoretical reflectance was less than 1 dB at most frequencies in the range from 0.2 to 10 kHz. Pearson correlation coefficients were greater than 0.95 between measured and theoretical time-domain reflectance within the flare region of the horns. The agreement suggests that the distributed reflectance of acoustic horns may be useful for validating reflectance measurements made in human ear canals; however, refinements to reflectance measurement methods may still be needed. PMID:26520306

  16. Reflectance measurement validation using acoustic horns.

    PubMed

    Rasetshwane, Daniel M; Neely, Stephen T

    2015-10-01

    Variability in wideband acoustic reflectance (and absorbance) measurements adversely affects the clinical utility of reflectance for diagnosis of middle-ear disorders. A reflectance standard would encourage consistency across different measurement systems and help identify calibration related issues. Theoretical equations exist for the reflectance of finite-length exponential, conical, and parabolic acoustic horns. Reflectance measurements were repeatedly made in each of these three horn shapes and the results were compared to the corresponding theoretical reflectance. A method is described of adjusting acoustic impedance measurements to compensate for spreading of the wave front that propagates from the small diameter sound port of the probe to the larger diameter of the acoustic cavity. Agreement between measured and theoretical reflectance was less than 1 dB at most frequencies in the range from 0.2 to 10 kHz. Pearson correlation coefficients were greater than 0.95 between measured and theoretical time-domain reflectance within the flare region of the horns. The agreement suggests that the distributed reflectance of acoustic horns may be useful for validating reflectance measurements made in human ear canals; however, refinements to reflectance measurement methods may still be needed.

  17. Constant current loop impedance measuring system that is immune to the effects of parasitic impedances

    NASA Technical Reports Server (NTRS)

    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.

  18. Protein Aggregation Measurement through Electrical Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Affanni, A.; Corazza, A.; Esposito, G.; Fogolari, F.; Polano, M.

    2013-09-01

    The paper presents a novel methodology to measure the fibril formation in protein solutions. We designed a bench consisting of a sensor having interdigitated electrodes, a PDMS hermetic reservoir and an impedance meter automatically driven by calculator. The impedance data are interpolated with a lumped elements model and their change over time can provide information on the aggregation process. Encouraging results have been obtained by testing the methodology on K-casein, a protein of milk, with and without the addition of a drug inhibiting the aggregation. The amount of sample needed to perform this measurement is by far lower than the amount needed by fluorescence analysis.

  19. Inverse acoustic scattering problem in half-space with anisotropic random impedance

    NASA Astrophysics Data System (ADS)

    Helin, Tapio; Lassas, Matti; Päivärinta, Lassi

    2017-02-01

    We study an inverse acoustic scattering problem in half-space with a probabilistic impedance boundary value condition. The Robin coefficient (surface impedance) is assumed to be a Gaussian random function with a pseudodifferential operator describing the covariance. We measure the amplitude of the backscattered field averaged over the frequency band and assume that the data is generated by a single realization of λ. Our main result is to show that under certain conditions the principal symbol of the covariance operator of λ is uniquely determined. Most importantly, no approximations are needed and we can solve the full non-linear inverse problem. We concentrate on anisotropic models for the principal symbol, which leads to the analysis of a novel anisotropic spherical Radon transform and its invertibility.

  20. Deduction of the acoustic impedance of the ground via a simulated three-dimensional microphone array.

    PubMed

    Alberts, W C Kirkpatrick; Sanchez, Kevin J

    2013-11-01

    While commonly used ground impedance deduction methods often utilize pairs of vertically separated microphones, deployed arrays rarely have this configuration, which increases the difficulty in automatically deducing local ground impedance from these arrays. The ability to deduce ground impedance using random sounds incident on a three-dimensional array would increase, for example, the accuracy of estimated elevation angles. The methods described by the American National Standards Institute Method for Determining the Acoustic Impedance of Ground Surfaces are extended to simulate deducing ground impedance by a three-dimensional array. Ground parameters indicative of grassland are successfully determined using a simulated three-dimensional array.

  1. Metamaterial buffer for broadband non-resonant impedance matching of obliquely incident acoustic waves.

    PubMed

    Fleury, Romain; Alù, Andrea

    2014-12-01

    Broadband impedance matching and zero reflection of acoustic waves at a planar interface between two natural materials is a rare phenomenon, unlike its optical counterpart, frequently observed for polarized light incident at the Brewster angle. In this article, it is shown that, by inserting a metamaterial layer between two acoustic materials with different impedance, it is possible to artificially realize an extremely broadband Brewster-like acoustic intromission angle window, in which energy is totally transmitted from one natural medium to the other. The metamaterial buffer, composed of acoustically hard materials with subwavelength tapered apertures, provides an interesting way to match the impedances of two media in a broadband fashion, different from traditional methods like quarter-wave matching or Fabry-Pérot resonances, inherently narrowband due to their resonant nature. This phenomenon may be interesting for a variety of applications including energy harvesting, acoustic imaging, ultrasonic transducer technology, and noise control.

  2. Optimization of Microphone Locations for Acoustic Liner Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; June, J. C.

    2015-01-01

    Two impedance eduction methods are explored for use with data acquired in the NASA Langley Grazing Flow Impedance Tube. The first is an indirect method based on the convected Helmholtz equation, and the second is a direct method based on the Kumaresan and Tufts algorithm. Synthesized no-flow data, with random jitter to represent measurement error, are used to evaluate a number of possible microphone locations. Statistical approaches are used to evaluate the suitability of each set of microphone locations. Given the computational resources required, small sample statistics are employed for the indirect method. Since the direct method is much less computationally intensive, a Monte Carlo approach is employed to gather its statistics. A comparison of results achieved with full and reduced sets of microphone locations is used to determine which sets of microphone locations are acceptable. For the indirect method, each array that includes microphones in all three regions (upstream and downstream hard wall sections, and liner test section) provides acceptable results, even when as few as eight microphones are employed. The best arrays employ microphones well away from the leading and trailing edges of the liner. The direct method is constrained to use microphones opposite the liner. Although a number of arrays are acceptable, the optimum set employs 14 microphones positioned well away from the leading and trailing edges of the liner. The selected sets of microphone locations are also evaluated with data measured for ceramic tubular and perforate-over-honeycomb liners at three flow conditions (Mach 0.0, 0.3, and 0.5). They compare favorably with results attained using all 53 microphone locations. Although different optimum microphone locations are selected for the two impedance eduction methods, there is significant overlap. Thus, the union of these two microphone arrays is preferred, as it supports usage of both methods. This array contains 3 microphones in the upstream

  3. Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers.

    PubMed

    Li, Zheng; Yang, Dan-Qing; Liu, Shi-Lei; Yu, Si-Yuan; Lu, Ming-Hui; Zhu, Jie; Zhang, Shan-Tao; Zhu, Ming-Wei; Guo, Xia-Sheng; Wu, Hao-Dong; Wang, Xin-Long; Chen, Yan-Feng

    2017-02-17

    High-quality broadband ultrasound transducers yield superior imaging performance in biomedical ultrasonography. However, proper design to perfectly bridge the energy between the active piezoelectric material and the target medium over the operating spectrum is still lacking. Here, we demonstrate a new anisotropic cone-structured acoustic metamaterial matching layer that acts as an inhomogeneous material with gradient acoustic impedance along the ultrasound propagation direction. When sandwiched between the piezoelectric material unit and the target medium, the acoustic metamaterial matching layer provides a broadband window to support extraordinary transmission of ultrasound over a wide frequency range. We fabricated the matching layer by etching the peeled silica optical fibre bundles with hydrofluoric acid solution. The experimental measurement of an ultrasound transducer equipped with this acoustic metamaterial matching layer shows that the corresponding -6 dB bandwidth is able to reach over 100%. This new material fully enables new high-end piezoelectric materials in the construction of high-performance ultrasound transducers and probes, leading to considerably improved resolutions in biomedical ultrasonography and compact harmonic imaging systems.

  4. Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers

    PubMed Central

    Li, Zheng; Yang, Dan-Qing; Liu, Shi-Lei; Yu, Si-Yuan; Lu, Ming-Hui; Zhu, Jie; Zhang, Shan-Tao; Zhu, Ming-Wei; Guo, Xia-Sheng; Wu, Hao-Dong; Wang, Xin-Long; Chen, Yan-Feng

    2017-01-01

    High-quality broadband ultrasound transducers yield superior imaging performance in biomedical ultrasonography. However, proper design to perfectly bridge the energy between the active piezoelectric material and the target medium over the operating spectrum is still lacking. Here, we demonstrate a new anisotropic cone-structured acoustic metamaterial matching layer that acts as an inhomogeneous material with gradient acoustic impedance along the ultrasound propagation direction. When sandwiched between the piezoelectric material unit and the target medium, the acoustic metamaterial matching layer provides a broadband window to support extraordinary transmission of ultrasound over a wide frequency range. We fabricated the matching layer by etching the peeled silica optical fibre bundles with hydrofluoric acid solution. The experimental measurement of an ultrasound transducer equipped with this acoustic metamaterial matching layer shows that the corresponding −6 dB bandwidth is able to reach over 100%. This new material fully enables new high-end piezoelectric materials in the construction of high-performance ultrasound transducers and probes, leading to considerably improved resolutions in biomedical ultrasonography and compact harmonic imaging systems. PMID:28211510

  5. Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Li, Zheng; Yang, Dan-Qing; Liu, Shi-Lei; Yu, Si-Yuan; Lu, Ming-Hui; Zhu, Jie; Zhang, Shan-Tao; Zhu, Ming-Wei; Guo, Xia-Sheng; Wu, Hao-Dong; Wang, Xin-Long; Chen, Yan-Feng

    2017-02-01

    High-quality broadband ultrasound transducers yield superior imaging performance in biomedical ultrasonography. However, proper design to perfectly bridge the energy between the active piezoelectric material and the target medium over the operating spectrum is still lacking. Here, we demonstrate a new anisotropic cone-structured acoustic metamaterial matching layer that acts as an inhomogeneous material with gradient acoustic impedance along the ultrasound propagation direction. When sandwiched between the piezoelectric material unit and the target medium, the acoustic metamaterial matching layer provides a broadband window to support extraordinary transmission of ultrasound over a wide frequency range. We fabricated the matching layer by etching the peeled silica optical fibre bundles with hydrofluoric acid solution. The experimental measurement of an ultrasound transducer equipped with this acoustic metamaterial matching layer shows that the corresponding ‑6 dB bandwidth is able to reach over 100%. This new material fully enables new high-end piezoelectric materials in the construction of high-performance ultrasound transducers and probes, leading to considerably improved resolutions in biomedical ultrasonography and compact harmonic imaging systems.

  6. Absorption and impedance boundary conditions for phased geometrical-acoustics methods.

    PubMed

    Jeong, Cheol-Ho

    2012-10-01

    Defining accurate acoustical boundary conditions is of crucial importance for room acoustic simulations. In predicting sound fields using phased geometrical acoustics methods, both absorption coefficients and surface impedances of the boundary surfaces can be used, but no guideline has been developed on which boundary condition produces accurate results. In this study, various boundary conditions in terms of normal, random, and field incidence absorption coefficients and normal incidence surface impedance are used in a phased beam tracing model, and the simulated results are validated with boundary element solutions. Two rectangular rooms with uniform and non-uniform absorption distributions are tested. Effects of the neglect of reflection phase shift are also investigated. It is concluded that the impedance, random incidence, and field incidence absorption boundary conditions produce reasonable results with some exceptions at low frequencies for acoustically soft materials.

  7. Readout electrode assembly for measuring biological impedance

    NASA Technical Reports Server (NTRS)

    Montgomery, L. D.; Moody, D. L., Jr. (Inventor)

    1976-01-01

    The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.

  8. Evaluation of a Variable-Impedance Ceramic Matrix Composite Acoustic Liner

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; Nark, D. M.; Howerton, B. M.

    2014-01-01

    As a result of significant progress in the reduction of fan and jet noise, there is growing concern regarding core noise. One method for achieving core noise reduction is via the use of acoustic liners. However, these liners must be constructed with materials suitable for high temperature environments and should be designed for optimum absorption of the broadband core noise spectrum. This paper presents results of tests conducted in the NASA Langley Liner Technology Facility to evaluate a variable-impedance ceramic matrix composite acoustic liner that offers the potential to achieve each of these goals. One concern is the porosity of the ceramic matrix composite material, and whether this might affect the predictability of liners constructed with this material. Comparisons between two variable-depth liners, one constructed with ceramic matrix composite material and the other constructed via stereolithography, are used to demonstrate this material porosity is not a concern. Also, some interesting observations are noted regarding the orientation of variable-depth liners. Finally, two propagation codes are validated via comparisons of predicted and measured acoustic pressure profiles for a variable-depth liner.

  9. Algorithmic Error Correction of Impedance Measuring Sensors

    PubMed Central

    Starostenko, Oleg; Alarcon-Aquino, Vicente; Hernandez, Wilmar; Sergiyenko, Oleg; Tyrsa, Vira

    2009-01-01

    This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer functions of the measuring sensor and signal conditioning converter, which contribute the principal additive and relative measurement errors. Some measuring systems have been implemented in order to estimate in practice the performance of the proposed methods. Particularly, a measuring system for analysis of C-V, G-V characteristics has been designed and constructed. It has been tested during technological process control of charge-coupled device CCD manufacturing. The obtained results are discussed in order to define a reasonable range of applied methods, their utility, and performance. PMID:22303177

  10. Acoustic Intensity Measurements in the Presence of Low Mach Number Flow

    DTIC Science & Technology

    1993-09-01

    broadband acoustic holography ,3 intensity measurements in the presence of flow,"𔄁𔄀. 7 in-situ evaluation of the acoustic impedance and sound absorption...Cross Spectra" Ph.D. Thesis, Catholic University, (1987). 3. Loyau, T., Pascal, J., Gaillard, P., "Broadband Acoustic Holography Reconstruction From...AD-A269 995 The Pennsylvania State University APPLIED RESEARCH LABORATORY P.O. Box 30 State College, PA 16804 ACOUSTIC INTENSITY MEASUREMENTS IN THE

  11. LDV measurement of bird ear vibrations to determine inner ear impedance and middle ear power flow

    NASA Astrophysics Data System (ADS)

    Muyshondt, Pieter G. G.; Pires, Felipe; Dirckx, Joris J. J.

    2016-06-01

    The mechanical behavior of the middle ear structures in birds and mammals is affected by the fluids in the inner ear (IE) that are present behind the oval window. In this study, the aim was to gather knowledge of the acoustic impedance of the IE in the ostrich, to be able to determine the effect on vibrations and power flow in the single-ossicle bird middle ear for future studies. To determine the IE impedance, vibrations of the ossicle were measured for both the quasi-static and acoustic stimulus frequencies. In the acoustic regime, vibrations were measured with a laser Doppler vibrometer and electromagnetic stimulation of the ossicle. The impedance of the inner ear could be determined by means of a simple RLC model in series, which resulted in a stiffness reactance of KIE = 0.20.1012 Pa/m3, an inertial impedance of MIE = 0.652.106 Pa s2/m3, and a resistance of RIE = 1.57.109 Pa s/m. The measured impedance is found to be considerably smaller than what is found for the human IE.

  12. Bioelectrical impedance analysis. What does it measure?

    NASA Technical Reports Server (NTRS)

    Schoeller, D. A.

    2000-01-01

    Bioelectrical impedance analysis (BIA) has been proposed for measuring fat-free mass, total body water, percent fat, body cell mass, intracellular water, and extracellular water: a veritable laboratory in a box. Although it is unlikely that BIA is quite this versatile, correlations have been demonstrated between BIA and all of these body compartments. At the same time, it is known that all of the compartments are correlated among themselves. Because of this, it is difficult to determine whether BIA is specific for any or all of these compartments. To investigate this question, we induced acute changes in total body water and its compartments over a 3-h period. Using this approach, we demonstrated that multifrequency BIA, using the Cole-Cole model to calculate the zero frequency and infinite frequency resistance, measures extracellular and intracellular water.

  13. Underwater asymmetric acoustic transmission structure using the medium with gradient change of impedance

    NASA Astrophysics Data System (ADS)

    Bo, Hu; Jie, Shi; Sheng-Guo, Shi; Yu, Sun; Zhong-Rui, Zhu

    2016-02-01

    We propose an underwater asymmetric acoustic transmission structure comprised of two media each with a gradient change of acoustic impedance. By gradually increasing the acoustic impedances of the media, the propagating direction of the acoustic wave can be continuously bent, resulting in allowing the acoustic wave to pass through along the positive direction and blocking acoustic waves from the negative one. The main advantages of this structure are that the asymmetric transmission effect of this structure can be realized and enhanced more easily in water. We investigate both numerically and experimentally the asymmetric transmission effect. The experimental results show that a highly efficient asymmetric acoustic transmission can be yielded within a remarkable broadband frequency range, which agrees well with the numerical prediction. It is of potential practical significance for various underwater applications such as reducing vibration and noise. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204049 and 11204050), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT1228), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20122304120023 and 20122304120011).

  14. Acoustic Liner Drag: Measurements on Novel Facesheet Perforate Geometries

    NASA Technical Reports Server (NTRS)

    Howerton, Brian M.; Jones, Michael G.

    2016-01-01

    Interest in characterization of the aerodynamic drag of acoustic liners has increased in the past several years. This paper details experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of several perforate-over-honeycomb liner configurations at flow speeds of centerline flow Mach number equals 0.3 and 0.5. Various perforate geometries and orientations are investigated to determine their resistance factors using a static pressure drop approach. Comparison of these resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 hertz at source sound pressure levels of 140 and 150 decibels. Educed impedance and attenuation spectra are used to determine the impact of variations in perforate geometry on acoustic performance.

  15. Acoustic Propagation and Barrier Diffraction Over an Impedance Plane.

    DTIC Science & Technology

    1982-10-13

    propagation solution into a barrier model so that ground reflections in addition to edge diffraction could be accounted for. Only the first term in the...model so that ground reflections in addition to edge N diffraction could be accounted for. Only the first term in the asymptotic ground propagation... contemporary research needs-particularly those of underwater acoustics as weil as community and aircraft noise control-a re-evaluation of previous results has

  16. Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Ahumada, Al (Technical Monitor)

    1997-01-01

    These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.

  17. On the Propagation of Plane Acoustic Waves in a Duct With Flexible and Impedance Walls

    NASA Technical Reports Server (NTRS)

    Frendi, Abdelkader; Vu, Bruce

    2003-01-01

    This Technical Memorandum (TM) discusses the harmonic and random plane acoustic waves propagating from inside a duct to its surroundings. Various duct surfaces are considered, such as rigid, flexible, and impedance. In addition, the effects of a mean flow are studied when the duct alone is considered. Results show a significant reduction in overall sound pressure levels downstream of the impedance wall for both mean flow and no mean flow cases and for a narrow duct. When a wider duct is used, the overall sound pressure level (OSPL) reduction downstream of the impedance wall is much smaller. In the far field, the directivity is such that the overall sound pressure level is reduced by about 5 decibels (dB) on the side of the impedance wall. When a flexible surface is used, the far field directivity becomes asymmetric with an increase in the OSPL on the side of the flexible surface of about 7 dB.

  18. Acoustical Measurement Of Furnace Temperatures

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Shakkottai; Venkateshan, Shakkottai P.

    1989-01-01

    Simple probes withstand severe conditions, yet give spatially-resolved temperature readings. Prototype acoustical system developed to measure temperatures from ambient to 1,800 degree F in such structures as large industrial lime kilns and recovery-boiler furnaces. Pulses of sound reflected from obstructions in sensing tube. Speed of sound and temperature in each segment deduced from travel times of pulses.

  19. Acoustic impedance characterization via numerical resolution of the inverse Helmholtz problem

    NASA Astrophysics Data System (ADS)

    Scalo, Carlo; Patel, Danish; Gupta, Prateek

    2016-11-01

    Impedance boundary conditions (IBCs) regulate the relative phasing and amplitudes of pressure and velocity fluctuations and, therefore, the acoustic energy flux. We present a numerical method to determine the acoustic impedance at the surface of an arbitrarily shaped cavity as seen by a generically oriented incident external harmonic planar wave. The proposed method (conceptually) inverts the usual eigenvalue-solving procedure underlying Helmholtz solvers: the impedance at one or multiple (but not all) boundaries is an output of the calculation and is obtained via implicit reconstruction the linear acoustic waveform at the frequency of the incident wave. The linearized governing equations are discretized via a mixed finite-difference/finite-volume approach and are closed with a generalized equation of state. Results are validated against quasi one-dimensional cases derived via direct application of Rott's linear thermoacoustic theory and by comparison against fully compressible Navier-Stokes simulations. This work is motivated by the need to develop a comprehensive suite of predictive tools capable of performing high-fidelity simulations of compressible boundary layers over assigned IBCs, accurately representing the acoustic response of arbitrarily shaped porous cavities.

  20. Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces

    PubMed Central

    Song, Kyungjun; Kim, Jedo; Hur, Shin; Kwak, Jun-Hyuk; Lee, Seong-Hyun; Kim, Taesung

    2016-01-01

    Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication. PMID:27562634

  1. Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces

    NASA Astrophysics Data System (ADS)

    Song, Kyungjun; Kim, Jedo; Hur, Shin; Kwak, Jun-Hyuk; Lee, Seong-Hyun; Kim, Taesung

    2016-08-01

    Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication.

  2. Multi-stage pulse tube cryocooler with acoustic impedance constructed to reduce transient cool down time and thermal loss

    NASA Technical Reports Server (NTRS)

    Gedeon, David R. (Inventor); Wilson, Kyle B. (Inventor)

    2008-01-01

    The cool down time for a multi-stage, pulse tube cryocooler is reduced by configuring at least a portion of the acoustic impedance of a selected stage, higher than the first stage, so that it surrounds the cold head of the selected stage. The surrounding acoustic impedance of the selected stage is mounted in thermally conductive connection to the warm region of the selected stage for cooling the acoustic impedance and is fabricated of a high thermal diffusivity, low thermal radiation emissivity material, preferably aluminum.

  3. Influence of exit impedance on finite difference solutions of transient acoustic mode propagation in ducts

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.

    1981-01-01

    The cutoff mode instability problem associated with a transient finite difference solution to the wave equation is explained. The steady-state impedance boundary condition is found to produce acoustic reflections during the initial transient, which cause finite instabilities in the cutoff modes. The stability problem is resolved by extending the duct length to prevent transient reflections. Numerical calculations are presented at forcing frequencies above, below, and nearly at the cutoff frequency, and exit impedance models are presented for use in the practical design of turbofan inlets.

  4. Scale Model Thruster Acoustic Measurement Results

    NASA Technical Reports Server (NTRS)

    Kenny, R. Jeremy; Vargas, Magda B.

    2013-01-01

    Subscale rocket acoustic data is used to predict acoustic environments for full scale rockets. Over the last several years acoustic data has been collected during horizontal tests of solid rocket motors. Space Launch System (SLS) Scale Model Acoustic Test (SMAT) was designed to evaluate the acoustics of the SLS vehicle including the liquid engines and solid rocket boosters. SMAT is comprised of liquid thrusters scalable to the Space Shuttle Main engines (SSME) and Rocket Assisted Take Off (RATO) motors scalable to the 5-segment Reusable Solid Rocket Motor (RSTMV). Horizontal testing of the liquid thrusters provided an opportunity to collect acoustic data from liquid thrusters to characterize the acoustic environments. Acoustic data was collected during the horizontal firings of a single thruster and a 4-thruster (Quad) configuration. Presentation scope. Discuss the results of the single and 4-thruster acoustic measurements. Compare the measured acoustic levels of the liquid thrusters to the Solid Rocket Test Motor V - Nozzle 2 (SRTMV-N2).

  5. Measurement of the acoustic reflex without a pressure seal.

    PubMed

    Surr, R K; Schuchman, G I

    1976-03-01

    Obtaining a hermetic seal in the external auditory canal is often a major obstacle in impedance audiometry. In the present study, the acoustic reflex threshold was determined for three groups of subjects, first with and then without a pressure-tight seal. It was found that for subjects with normal hearing or sensorineural hearing loss and normal tympanograms, 96% of the measurements obtained without a pressure seal were within 5 dB of those obtained with a seal. Among the subjects who exhibited negative middle ear pressure, the acoustic reflex could be measured consistently at the point of maximum compliance, while no response was observed without a pressure seal.

  6. Acoustic impedance matching of piezoelectric transducers to the air.

    PubMed

    Gómez Alvarez-Arenas, Tomás E

    2004-05-01

    The purpose of this work is threefold: to investigate material requirements to produce impedance matching layers for air-coupled piezoelectric transducers, to identify materials that meet these requirements, and to propose the best solution to produce air-coupled piezoelectric transducers for the low megahertz frequency range. Toward this end, design criteria for the matching layers and possible configurations are reviewed. Among the several factors that affect the efficiency of the matching layer, the importance of attenuation is pointed out. A standard characterization procedure is applied to a wide collection of candidate materials to produce matching layers. In particular, some types of filtration membranes are studied. From these results, the best materials are identified, and the better matching configuration is proposed. Four pairs of air-coupled piezoelectric transducers also are produced to illustrate the performance of the proposed solution. The lowest two-way insertion loss figure is -24 dB obtained at 0.45 MHz. This increases for higher frequency transducers up to -42 dB at 1.8 MHz and -50 at 2.25 MHz. Typical bandwidth is about 15-20%.

  7. A two electrode apparatus for electrical impedance measurements

    NASA Astrophysics Data System (ADS)

    Merriam, J. B.

    2009-12-01

    A two electrode cell for complex impedance measurements on core samples in the range 1 mHz - 0.3 kHz is described. Two electrode cells are more convenient than four electrode cells but some restrictions need to be observed. I will show that the contact impedance between the electrodes and the sample can be controlled and reduced to less than fifty ohms in most cases. The contact impedance is repeatable, with a peak phase near 10 Hz of less than one degree and a maximum change in impedance magnitude of less than fifty ohm. A model for the contact impedance is used to correct impedance measurements, leaving an un-modeled contact impedance of a few ohms. There is typically a drift of about 100 ohm during a measurement sequence due to diffusion between the ceramic frits at the ends of the sample. This is corrected by repeat measurements at 100 Hz. Un-modeled impedance changes due to drift are about ten ohm. The un-modeled impedance changes mean that the relative error on conductive samples is greater than on resistive samples. Repeat measurements on a sandstone sample with conductive pore water (0.14 S/m) yield a mean of 492 ohms with a standard deviation of 20 ohm, or about five percent. Measurements on mineralized core and on cells constructed from mixtures of silica sand and polarizable minerals demonstrate that the two electrode set up can be used even on heavily mineralized samples.

  8. Transverse impedance measurement in RHIC and the AGS

    SciTech Connect

    Biancacci, Nicolo; Blaskiewicz, M.; Dutheil, Y.; Liu, C.; Mernick, M.; Minty, M.; White, S. M.

    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.

  9. Quantitative non-linear ultrasonic imaging of targets with significant acoustic impedance contrast--an experimental study.

    PubMed

    Guillermin, Régine; Lasaygues, Philippe; Rabau, Guy; Lefebvre, Jean-Pierre

    2013-08-01

    This study deals with the reconstruction, from ultrasonic measured data, of the sound speed profile of a penetrable two-dimensional target of arbitrary cross-section embedded in an infinite medium. Green's theorem is used to obtain a domain integral representation of the acoustical scattered field, and a discrete formulation of the inverse problem is obtained using a moment method. An iterative non-linear algorithm minimizing the discrepancy between the measured and computed scattered fields is used to reconstruct the sound speed profile in the region of interest. The minimization process is performed using a conjugated-gradient method. An experimental study with significant acoustical impedance contrast targets immersed in water was performed. Images of the sound speed profile obtained by inversion of experimental data are presented.

  10. Impedance measurements for detecting pathogens attached to antibodies

    DOEpatents

    Miles, Robin R.; Venkateswaran, Kodumudi S.; Fuller, Christopher K.

    2004-12-28

    The use of impedance measurements to detect the presence of pathogens attached to antibody-coated beads. In a fluidic device antibodies are immobilized on a surface of a patterned interdigitated electrode. Pathogens in a sample fluid streaming past the electrode attach to the immobilized antibodies, which produces a change in impedance between two adjacent electrodes, which impedance change is measured and used to detect the presence of a pathogen. To amplify the signal, beads coated with antibodies are introduced and the beads would stick to the pathogen causing a greater change in impedance between the two adjacent electrodes.

  11. Investigation of ground reflection and impedance from flyover noise measurements

    NASA Technical Reports Server (NTRS)

    Chapkis, R. L.; Marsh, A. H.

    1978-01-01

    An extensive series of flyover noise tests was conducted for the primary purpose of studying meteorological effects on propagation of aircraft noise. The test airplane, a DC 9-10, flew several level-flight passes at various heights over a taxiway. Two microphone stations were located under the flight path. A total of 37 runs was selected for analysis and processed to obtain a consistant set of 1/3 octave band sound pressure levels at half-second intervals. The goal of the present study was to use the flyover noise data to deduce acoustical reflection coefficients and hence, acoustical impedances.

  12. Acoustic impedance studies in Triassic reservoirs in the Netherlands - application to development and exploration

    SciTech Connect

    Griffiths, M.; Ford, J.

    1995-08-01

    Simple and cost effective seismic forward modelling techniques have been used in conjunction with petrophysical and geological data to provide an integrated approach to understanding the seismic response of Triassic gas reservoirs onshore and offshore Netherlands. Analysis shows that for the Volpriehausen Sandstone in the offshore sector a relationship exists between reservoir acoustic impedance and porosity such that an increase in porosity leads to a decrease in acoustic impedance. Data can be sub-divided on the basis of fluid fill and cementation with trends for both gas and water cases. Regression analysis has defined the optimum relationship for each fluid case and these relationships have been used to predict the acoustic impedance profiles for a variety of reservoir scenarios. Modelling shows that the highest seismic amplitudes and the greatest relative amplitude variation with fluid fill are related to high porosity reservoir. In the onshore sector, analysis for the Roet Sandstone has shown that even small scale variations in reservoir properties can be recorded within the detail of the seismic response. Results from seismic forward modelling compare with amplitude variations observed in real data and suggest that, within the limitations of the dataset and methodology, the technique can be used to predict reservoir attributes from the seismic response. So far, the technique has been sucessfully applied to both exploration and field development projects.

  13. A frequency-response-based method of sound velocity measurement in an impedance tube

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Thomas, P. J.; Wang, Tongqing

    2017-04-01

    A stable and accurate new method for the measurement of the velocity of sound is proposed. The method is based on the characteristics of the frequency response measured at different positions in an impedance tube and it eliminates adverse effects caused by reflections from the transmitting transducer at the bottom of the impedance tube. A series of experiments is conducted, at different water temperatures, different positions in the impedance tube and under constant pressure, to validate the feasibility and stability of the new method. The new technique is also extended to hydrostatic pressure conditions with stable sound velocity. Our method generates an accurate measurement result in comparison to the estimated or average value obtained with currently existing methods. The novel method is suitable to be widely used in underwater acoustics.

  14. Comparison of Acoustic Impedance Eduction Techniques for Locally-Reacting Liners

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Parrott, T. L.; Watson, W. R.

    2003-01-01

    Typical acoustic liners used in current aircraft inlets and aft-fan ducts consist of some type of perforated facesheet bonded to a honeycomb core. A number of techniques for determining the acoustic impedance of these locallyreacting liners have been developed over the last five decades. In addition, a number of models have been developed to predict the acoustic impedance of locallyreacting liners in the presence of grazing flow, and to use that information together with aeroacoustic propagation codes to assess the noise absorption provided by these liners. These prediction models have incorporated the results from databases acquired with specific impedance eduction techniques. Thus, while these prediction models are acceptable for liners that are similar to those tested in these databases, their application to new liner configurations must be viewed with caution. The primary purpose of this paper is to provide a comparison of impedance eduction techniques that have been implemented at various aerospace research laboratories in the United States (NASA Langley Research Center, General Electric Aircraft Engines, B. F. Goodrich and Boeing). A secondary purpose is to provide data for liner configurations that extend the porosity range beyond that which has been previously used in common aircraft engine nacelles. Two sets of liners were designed to study the effects of three parameters: perforate hole diameter, facesheet thickness and porosity. These two sets of liners were constructed for testing in each of the laboratories listed above. The first set of liners was designed to fit into the NASA Langley and Boeing test facilities. The second set was designed to fit into the General Electric Aircraft Engines and B. F. Goodrich test facilities. By using the same parent material, both sets of liners were identical to within the limits of material and fabrication variability. Baseline data were obtained in the normal incidence impedance tubes at NASA Langley and B. F

  15. Electrochemical impedance measurement of a carbon nanotube probe electrode

    NASA Astrophysics Data System (ADS)

    Inaba, Akira; Takei, Yusuke; Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

    2012-12-01

    We measured and analyzed the electrochemical impedance of carbon nanotube (CNT) probe electrodes fabricated through the physical separation of insulated CNT bridges. The fabricated CNT electrodes were free-standing CNTs that were completely covered with an insulator, except for their tips. Typical dimensions of the nanoelectrodes were 1-10 nm in CNT diameter, 80-300 nm in insulator diameter, 0.5-4 μm in exposed CNT length and 1-10 μm in probe length. The electrochemical impedance at frequencies ranging from 40 Hz to 1 MHz was measured in physiological saline. The measured impedance of the CNT electrode was constant at 32 MΩ at frequencies below 1 kHz and was inversely proportional to frequency at frequencies above 10 kHz. By means of comparison with the parasitic capacitive impedance of the insulator membrane, we confirmed that the electrode was sufficiently insulated such that the measured constant impedance was given by the exposed CNT tip. Consequently, we can use the CNT electrode for highly localized electrochemical impedance measurements below 1 kHz. Considering an equivalent circuit and the nanoscopic dimensions of the CNT electrode, we demonstrated that the constant impedance was governed by diffusion impedance, whereas the solution resistance, charge-transfer resistance and double-layer capacitance were negligible.

  16. Effect of Feeding and Suction on Gastric Impedance Spectroscopy Measurements.

    PubMed

    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.

  17. Viscous effects on the acoustics and stability of a shear layer over an impedance wall

    NASA Astrophysics Data System (ADS)

    Khamis, Doran; Brambley, Edward James

    2017-01-01

    The effect of viscosity and thermal conduction on the acoustics in a shear layer above an impedance wall is investigated numerically and asymptotically by solving the compressible linearised Navier-Stokes equations. It is found that viscothermal effects can be as important as shear, and therefore including shear while neglecting viscothermal effects by solving the linearised Euler equations is questionable. In particular, the damping rate of upstream propagating waves is found to be dramatically under-predicted by the LEE in certain instances. The effects of viscosity on stability are also found to be important. Short wavelength disturbances are stabilised by viscosity, greatly altering the characteristic wavelength and maximum growth rate of instability. For the parameters typical of aeroacoustic simulations considered here, the Reynolds number below which the flow stabilizes ranges from $10^5$ to $10^7$. By assuming a thin but nonzero-thickness boundary layer, asymptotic analysis leads to a system of boundary layer governing equations for the acoustics. This system may be solved numerically to produce an effective impedance boundary condition, applicable at the wall of a uniform inviscid flow, that accounts for both the shear and viscosity within the boundary layer. An alternative asymptotic analysis in the high frequency limit yields a different set of equations with analytic solutions. The acoustic mode shapes and axial wavenumbers from both asymptotic analyses compare well with numerical solutions of the full LNSE. A closed-form effective impedance boundary condition is derived from the high-frequency asymptotics, suitable for application in frequency-domain numerical simulations. Finally, surface waves are considered, and it is shown that a viscous flow over an impedance lining supports a greater number of surface wave modes than an inviscid flow.

  18. Influence of exit impedance on finite difference solutions of transient acoustic mode propagation in ducts

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.

    1981-01-01

    The time-dependent governing acoustic-difference equations and boundary conditions are developed and solved for sound propagation in an axisymmetric (cylindrical) hard-wall duct without flow and with spinning acoustic modes. The analysis begins with a harmonic sound source radiating into a quiescent duct. This explicit iteration method then calculates stepwise in real time to obtain the steady solutions of the acoustic field. The transient method did not converge to the steady-state solution for cutoff acoustic duct modes. This has implications as to its use in a variable-area duct, where modes may become cutoff in the smal-area portion of the duct. For single cutoff mode propagation the steady-state impedance boundary condition produced acoustic reflections during the initial transient that caused finite instabilities in the numerical calculations. The stability problem is resolved by reformulating the exit boundary condition. Example calculations show good agreement with exact analytical and numerical results for forcing frequencies above, below, and nearly at the cutoff frequency.

  19. International Congress on Acoustic Intensity Measurement: Measurement Techniques and Applications, 2nd, Senlis, France, September 23-26, 1985, Proceedings

    NASA Astrophysics Data System (ADS)

    Recent developments in acoustic-intensity measurement are discussed in reviews and reports of theoretical and experimental investigations. Instrumentation, vector acoustics, sound radiation, intensity in the presence of flow, intensity in structures, sound power, source localization, impedance, absorption, and transmission are the fields covered by the contributions. Specific topics addressed include microphone configurations for intensity probes, the rotational structure of intensity fields, acoustic intensity and numerical simulation, sound-power measurement in the presence of background noise, and techniques for measuring the absorption coefficient of acoustic materials. Graphs, drawings, diagrams, tables of numerical data, and photographs of test setups are provided.

  20. Measurement and simulation of the RHIC abort kicker longitudinal impedence

    SciTech Connect

    Abreu,N.P.; Hahn,H.; Choi, E.

    2009-09-01

    In face of the new upgrades for RHIC the longitudinal impedance of the machine plays an important role in setting the threshold for instabilities and the efficacy of some systems. In this paper we describe the measurement of the longitudinal impedance of the abort kicker for RHIC as well as computer simulations of the structure. The impedance measurement was done by the S{sub 21} wire method covering the frequency range from 9 kHz to 2.5 GHz. We observed a sharp resonance peak around 10 MHz and a broader peak around 20 MHz in both, the real and imaginary part, of the Z/n. These two peaks account for a maximum imaginary longitudinal impedance of j15 {Omega}, a value an order of magnitude larger than the estimated value of j0.2 {Omega}, which indicates that the kicker is one of the main sources of longitudinal impedance in the machine. A computer model was constructed for simulations in the CST MWS program. Results for the magnet input and the also the beam impedance are compared to the measurements. A more detail study of the system properties and possible changes to reduce the coupling impedance are presented.

  1. Damage detection technique by measuring laser-based mechanical impedance

    SciTech Connect

    Lee, Hyeonseok; Sohn, Hoon

    2014-02-18

    This study proposes a method for measurement of mechanical impedance using noncontact laser ultrasound. The measurement of mechanical impedance has been of great interest in nondestructive testing (NDT) or structural health monitoring (SHM) since mechanical impedance is sensitive even to small-sized structural defects. Conventional impedance measurements, however, have been based on electromechanical impedance (EMI) using contact-type piezoelectric transducers, which show deteriorated performances induced by the effects of a) Curie temperature limitations, b) electromagnetic interference (EMI), c) bonding layers and etc. This study aims to tackle the limitations of conventional EMI measurement by utilizing laser-based mechanical impedance (LMI) measurement. The LMI response, which is equivalent to a steady-state ultrasound response, is generated by shooting the pulse laser beam to the target structure, and is acquired by measuring the out-of-plane velocity using a laser vibrometer. The formation of the LMI response is observed through the thermo-mechanical finite element analysis. The feasibility of applying the LMI technique for damage detection is experimentally verified using a pipe specimen under high temperature environment.

  2. Correcting electrode impedance effects in broadband SIP measurements

    NASA Astrophysics Data System (ADS)

    Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Vereecken, Harry

    2016-04-01

    Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference <0.2 mrad) up to a frequency of 10 kHz after the effect of the different electrode impedances was removed. Finally, SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.

  3. Plasma Impedance Spectrum Analyzer (PISA): an advanced impedance probe for measuring plasma density and other parameters

    NASA Astrophysics Data System (ADS)

    Rowland, D. E.; Pfaff, R. F.; Uribe, P.; Burchill, J.

    2006-12-01

    High-accuracy, high-cadence measurements of ionospheric electron density between 100 and a few x 106 / cc and electron temperature from 200 K to a few thousand K are of critical importance for understanding conductivity, Joule heating rates, and instability growth rates. We present results from the development of an impedance probe at NASA GSFC and show its strengths relative to other measurement techniques. Complementary measurement techniques such as Langmuir Probes, while providing extremely high measurement cadence, suffer from uncertainties in calibration, surface contamination effects, and wake/sheath effects. Impedance Probes function by measuring the phase shift between the voltage on a long antenna and the current flowing from the antenna into the plasma as a function of frequency. At frequencies for which the phase shift is zero, a plasma resonance is assumed to exist. These resonances depend on a variety of plasma parameters, including the electron density, electron temperature, and magnetic field strength, as well as the antenna geometry, angle between the antenna and the magnetic field, and sheath / Debye length effects, but do not depend on the surface properties of the antenna. Previous impedance probe designs which "lock" onto the upper hybrid resonance are susceptible to losing lock in low-density environments. Information about other resonances, including the series resonance (which strongly depends on temperature) and other resonances which may occur near the upper hybrid, confounding its identification, are typically not transmitted. The novel features of the GSFC Impedance Probe (PISA) include: 1) A white noise generator that stimulates a wide range of frequencies simultaneously, allowing the instrument to send down the entire impedance frequency spectrum every few milliseconds. This allows identification of all resonance frequencies, including the series resonance which depends on temperature. 2) DC bias voltage stepping to bring the antenna

  4. Electrical impedance measurements: rapid method for detecting and monitoring microorganisms.

    PubMed Central

    Cady, P; Dufour, S W; Shaw, J; Kraeger, S J

    1978-01-01

    A conceptually simple and east-to-use technique is described that uses continuous impedance measurements for automated monitoring of microbial growth and metabolism. The method has been applied to a wide range of microorganisms. Optical clarity is not required. The sensitivity and reproducibility of the method are demonstrated. The mechanism whereby microbial growth alters the impedance of the medium is discussed, as well as potential applications of the method to clinical microbiology. Images PMID:348718

  5. Propagation of sound through the Earth's atmosphere. 1: Measurement of sound absorption in the air. 2: Measurement of ground impedance

    NASA Technical Reports Server (NTRS)

    Becher, J.; Meredith, R. W.; Zuckerwar, A. J.

    1981-01-01

    The fabrication of parts for the acoustic ground impedance meter was completed, and the instrument tested. Acoustic ground impedance meter, automatic data processing system, cooling system for the resonant tube, and final results of sound absorption in N2-H2O gas mixtures at elevated temperatures are described.

  6. Feasibility of Bioelectrical Impedance Spectroscopy Measurement before and after Thoracentesis

    PubMed Central

    Weyer, Sören; Pauly, Karolin; Napp, Andreas; Dreher, Michael; Leonhardt, Steffen; Marx, Nikolaus; Schauerte, Patrick; Mischke, Karl

    2015-01-01

    Background. Bioelectrical impedance spectroscopy is applied to measure changes in tissue composition. The aim of this study was to evaluate its feasibility in measuring the fluid shift after thoracentesis in patients with pleural effusion. Methods. 45 participants (21 with pleural effusion and 24 healthy subjects) were included. Bioelectrical impedance was analyzed for “Transthoracic,” “Foot to Foot,” “Foot to Hand,” and “Hand to Hand” vectors in low and high frequency domain before and after thoracentesis. Healthy subjects were measured at a single time point. Results. The mean volume of removed pleural effusion was 1169 ± 513 mL. The “Foot to Foot,” “Hand to Hand,” and “Foot to Hand” vector indicated a trend for increased bioelectrical impedance after thoracentesis. Values for the low frequency domain in the “Transthoracic” vector increased significantly (P < 0.001). A moderate correlation was observed between the amount of removed fluid and impedance change in the low frequency domain using the “Foot to Hand” vector (r = −0.7). Conclusion. Bioelectrical impedance changes in correlation with the thoracic fluid level. It was feasible to monitor significant fluid shifts and loss after thoracentesis in the “Transthoracic” vector by means of bioelectrical impedance spectroscopy. The trial is registered with Registration Numbers IRB EK206/11 and NCT01778270. PMID:25861647

  7. Microbial Sulfate Reduction Measured by an Automated Electrical Impedance Technique

    NASA Technical Reports Server (NTRS)

    Oremland, R. S.; Silverman, M. P.

    1979-01-01

    Electrical impedance measurements are used to investigate the rates of sulfate reduction by pure cultures of and sediments containing sulfur-reducing bacteria. Changes in the electrical impedance ratios of pure cultures of Desulfovibrio aestuarii and samples of reduced sediments from San Francisco Bay were measured by a Bactometer 32, and sulfate reduction was followed by measuring the incorporation of (S-35) sulfate into metal sulfides. The growth of the bacteria in pure culture is found to result in an increase of 0.2200 in the impedance ratio within 24 h, accompanied by increases in protein, ATP, sulfide and absorptance at 660 nm, all of which are inhibited by the addition of molybdate. Similar responses were observed in the sediments, although impedance ratio responses were not completely inhibited upon the addition of molybdate, due to the presence of nonsulfate-respiring microorganisms. Experiments conducted with sterile media and autoclaved sediments indicate that the presence of H2S together with iron is responsible for the impedance effect, and sulfate reduction rates ranging between 0.85 and 1.78 mmol/l per day are estimated for the sediments by the impedance technique.

  8. Scatterer size and concentration estimation technique based on a 3D acoustic impedance map from histologic sections

    NASA Astrophysics Data System (ADS)

    Mamou, Jonathan; Oelze, Michael L.; O'Brien, William D.; Zachary, James F.

    2004-05-01

    Accurate estimates of scatterer parameters (size and acoustic concentration) are beneficial adjuncts to characterize disease from ultrasonic backscatterer measurements. An estimation technique was developed to obtain parameter estimates from the Fourier transform of the spatial autocorrelation function (SAF). A 3D impedance map (3DZM) is used to obtain the SAF of tissue. 3DZMs are obtained by aligning digitized light microscope images from histologic preparations of tissue. Estimates were obtained for simulated 3DZMs containing spherical scatterers randomly located: relative errors were less than 3%. Estimates were also obtained from a rat fibroadenoma and a 4T1 mouse mammary tumor (MMT). Tissues were fixed (10% neutral-buffered formalin), embedded in paraffin, serially sectioned and stained with H&E. 3DZM results were compared to estimates obtained independently against ultrasonic backscatter measurements. For the fibroadenoma and MMT, average scatterer diameters were 91 and 31.5 μm, respectively. Ultrasonic measurements yielded average scatterer diameters of 105 and 30 μm, respectively. The 3DZM estimation scheme showed results similar to those obtained by the independent ultrasonic measurements. The 3D impedance maps show promise as a powerful tool to characterize ultrasonic scattering sites of tissue. [Work supported by the University of Illinois Research Board.

  9. Acoustic Measurements of Small Solid Rocket Motor

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Kenny, R. Jeremy

    2010-01-01

    Rocket acoustic noise can induce loads and vibration on the vehicle as well as the surrounding structures. Models have been developed to predict these acoustic loads based on scaling existing solid rocket motor data. The NASA Marshall Space Flight Center acoustics team has measured several small solid rocket motors (thrust below 150,000 lbf) to anchor prediction models. This data will provide NASA the capability to predict the acoustic environments and consequent vibro-acoustic response of larger rockets (thrust above 1,000,000 lbf) such as those planned for the NASA Constellation program. This paper presents the methods used to measure acoustic data during the static firing of small solid rocket motors and the trends found in the data.

  10. Measurement and modelling the sensitivity of tetrapolar transfer impedance measurements.

    PubMed

    Naydenova, E; Cavendish, S; Wilson, A J

    2016-10-01

    Finite element method (FEM) modelling of a small disk in a homogeneous saline medium showed that the sensitivity distribution for tetrapolar transfer impedance measurements was dependant on the ratio, σdisk/σsaline, and not absolute conductivity values. In addition, the amplitude of the negative sensitivity regions between the drive and receive electrodes decreased non-linearly with σdisk/σsaline for σdisk/σsaline < 1, eventually becoming zero. This non-linear behaviour determined the limit of the assumption of a small change in conductivity in Geselowitz's lead theorem with 0.5 <σdisk/σsaline <1.5 for the measurements reported. The modelling supported the design of a sensitivity measurement system using an insulating support and a metal disk in a saline filled tank. Measurements were shown to give good agreement with sensitivity predictions from Geselowitz's lead theorem. Replacing the homogeneous medium in the FEM model with layers of different conductivity parallel to the plane of the electrodes changed the sensitivity distribution when the thickness of the layers adjacent to the electrodes were less than ½ the electrode spacing. A layer of greater conductivity over a layer of lesser conductivity next to the electrodes gave a peak in the sensitivity distribution and extended regions of negative sensitivity further into the tissue.

  11. Calibration of ipsilateral stimulus transducer for acoustic reflex measurements.

    PubMed

    Olsen, S; Osterhammel, P A; Rasmussen, A N; Nielsen, L H

    1995-01-01

    Pure-tone Reference Equivalent Threshold Sound Pressure Level (RETSPL) of the ipsilateral stimulus receiver for acoustic reflex measurements on Madsen Electronics type Zodiac 901 impedance audiometer is provided. The results, obtained from 20 normal-hearing subjects, are achieved by comparing hearing threshold levels measured using a TDH 39 telephone (calibrated to ISO 389) with thresholds recorded using the ipsilateral stimulus insert phone. The calibration is referenced to an IEC-711 ear simulator and comprises the following frequencies: 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, 8000 Hz.

  12. Impedance spectral measurements made through a membrane infection barrier.

    PubMed

    Brown, Brian H; Gonzalez-Correa, Carlos A; Bremner, John; Tidy, John A

    2006-12-01

    Impedance spectra of superficial tissues can be used to detect pre-malignant changes in the cervix but require electrical contact to be made between a probe and the tissue. Using a membrane which is permeable to ions but forms a barrier to agents of infection should enable impedance spectra to be measured without causing an infection risk to the patient. The properties required of such a membrane are considered and measurements on two suitable membranes are presented. It is shown that impedance spectra can be measured through a thin natural cellulose based membrane (Cuprophan) and that these are not significantly different from directly measured spectra. The ability of the membranes to block a virus is tested using expired polio virus vaccine.

  13. The influence of urine volume on body impedance measurement.

    PubMed

    Hong, K H; Park, K S

    2008-01-01

    Bio-signal has some characteristics that the signal is so weak. So, it is good that the factors to influence measured electrical signal are eliminated as much as they can. So, in this paper we will show the influence of urine in bladder on measuring human body impedance. Human urine has different conductivity from other human tissues. Therefore, if the volume of the urine changed, the measured body impedance data also changed.So, in this paper, we will show the influence of urine in bladder with foot-to-foot and thigh-to-thigh current paths. As a result, if the current flows through human bladder, the influence of urine in the bladder must be considered when the body impedance is measured

  14. In situ impedance measurement of microwave atmospheric pressure plasma

    NASA Astrophysics Data System (ADS)

    Lee, S. T.; Nam, W. J.; Lee, J. K.; Yun, G. S.

    2017-04-01

    The impedance of atmospheric pressure argon plasma jets driven by microwave frequency is determined in situ by a novel ‘two frequency method’. In the conventional method of reflection coefficient ({{S}}11) measurement, the frequency of the driving microwave power is scanned, which inevitably affects the plasma characters and leads to uncertainty in the estimated plasma impedance. In our proposed method, the frequency-scanning signal additional to the driving power is used to measure {{S}}11 over a wide frequency range, which enables accurate determination of the plasma impedance based on an equivalent circuit model. The measured resistance and reactance of the plasma increase with the driving power in agreement with the transmission line theory. Based on this in situ measurement of the plasma impedance, the net power coupled to the plasma has been determined. The overall power efficiency remains approximately unchanged around 45% for different input power levels owing to the competing effects between the impedance mismatch and the volume change of the plasma.

  15. Possibilities for predictive measurement of the transthoracic impedance in defibrillation.

    PubMed

    Krasteva, V; Hatib, F A; Trendafilova, E; Daskalov, I

    2001-01-01

    Transthoracic electrical defibrillation is administered by high voltages and currents applied through large size electrodes. Therefore, the defibrillator load impedance becomes an essential factorfor the efficacy of the procedure. Attempts at prediction of transthoracic impedance by pre-shock measurement with low-amplitude high-frequency current have yielded apparently promising results. A reassessment was undertaken of the comparison between transthoracic impedance measured over a wide frequency range (bioimpedance spectroscopy) and measured during the shock. An estimation of the possibilities for pre-shock 'prediction ' of the impedance was performed, to allow adequate selection of the defibrillation energy or current with the intention of increasing the possibility for positive results with the first shock. Data were obtained from experimental fibrillation/defibrillation cycles on dogs andfrom cardioversion of atrial fibrillation or flutter in patients. The final results suggest that high-frequency low-amplitude impedance measurements cannot predict the corresponding value during the shock with very high accuracy, as differences up to 15-17% were found using biphasic pulses in patients. However, the method can be used for approximate assessments.

  16. A semi-analytical model for the acoustic impedance of finite length circular holes with mean flow

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Morgans, Aimee S.

    2016-12-01

    The acoustic response of a circular hole with mean flow passing through it is highly relevant to Helmholtz resonators, fuel injectors, perforated plates, screens, liners and many other engineering applications. A widely used analytical model [M.S. Howe. "Onthe theory of unsteady high Reynolds number flow through a circular aperture", Proc. of the Royal Soc. A. 366, 1725 (1979), 205-223] which assumes an infinitesimally short hole was recently shown to be insufficient for predicting the impedance of holes with a finite length. In the present work, an analytical model based on Green's function method is developed to take the hole length into consideration for "short" holes. The importance of capturing the modified vortex noise accurately is shown. The vortices shed at the hole inlet edge are convected to the hole outlet and further downstream to form a vortex sheet. This couples with the acoustic waves and this coupling has the potential to generate as well as absorb acoustic energy in the low frequency region. The impedance predicted by this model shows the importance of capturing the path of the shed vortex. When the vortex path is captured accurately, the impedance predictions agree well with previous experimental and CFD results, for example predicting the potential for generation of acoustic energy at higher frequencies. For "long" holes, a simplified model which combines Howe's model with plane acoustic waves within the hole is developed. It is shown that the most important effect in this case is the acoustic non-compactness of the hole.

  17. Flow Duct Data for Validation of Acoustic Liner Codes for Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Munro, Scott; Gaeta, R. J., Jr.

    2000-01-01

    The objective of the study reported here was to acquire acoustic and flow data with hard and lined duct wall duct sections for validation of a liner prediction code being developed at NASA LaRC. Both the mean flowfield and acoustic flowfields were determined in a cross-plane of the rectangular duct. A flow duct facility with acoustic drivers connected to a rectangular (4.7 x 2.0 inch) source section and a linear acoustic liner mounted downstream of the source section was used in this study. The liner section was designed to allow liner materials to be placed on all 4 walls of the duct. The test liner was of the locally-reacting type and was made from a ceramic material. The material, consisting of a tubular structure, was provided by NASA LaRC. The liner was approximately 8.89 cm (3.5 inches) thick. For the current study, only the two "short" sides of the duct were lined with liner material. The other two sides were hard walls. Two especially built instrumentation sections were attached on either sides of the liner section to allow acoustic and flow measurements to be made upstream and downstream of the liner. The two instrumentation duct sections were built to allow measurement of acoustic and flow properties at planes perpendicular to flow upstream and downstream of the liner section. The instrumentation section was also designed to provide a streamwise gradient in acoustic (complex) pressure from which the acoustic particle velocity, needed for the model validation, can be computed. Flow measurements included pressure, temperature, and velocity profiles upstream of the liner section. The in-flow sound pressure levels and phases were obtained with a microphone probe equipped with a nose cone in two cross planes upstream of the liner and two cross plane downstream of the liner. In addition to the acoustic measurements at the cross planes. axial centerline acoustic data was acquired using an axially traversing microphone probe which was traversed from a location

  18. Effect of grazing flow on the acoustic impedance of Helmholtz resonators consisting of single and clustered orifices

    NASA Technical Reports Server (NTRS)

    Hersch, A. S.; Walker, B.

    1979-01-01

    A semiempirical fluid mechanical model is derived for the acoustic behavior of thin-walled single orifice Helmholtz resonators in a grazing flow environment. The incident and cavity sound fields are connected in terms of an orifice discharge coefficient whose values are determined experimentally using the two-microphone method. Measurements show that at high grazing flow speeds, acoustical resistance is almost linearly proportional to the grazing flow speed and almost independent of incident sound pressure. The corresponding values of reactance are much smaller and tend towards zero. For thicker-walled orifice plates, resistance and reactance were observed to be less sensitive to grazing flow as the ratio of plate thickness to orifice diameter increased. Loud tones were observed to radiate from a single orifice Helmholtz resonator due to interaction between the grazing flow shear layer and the resonator cavity. Measurements showed that the tones radiated at a Strouhal number equal to 0.26. The effects of grazing flow on the impedance of Helmholtz resonators consisting of clusters of orifices was also studied. In general, both resistance and reaction were found to be virtually independent of orifice relative spacing and number. These findings are valid with and without grazing flow.

  19. A model for the pressure excitation spectrum and acoustic impedance of sound absorbers in the presence of grazing flow

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1973-01-01

    The acoustic impedance of sound absorbers in the presence of grazing flow is essential information when analyzing sound propagation within ducts. A unification of the theory of the nonlinear acoustic resistance of Helmholtz resonators including grazing flow is presented. The nonlinear resistance due to grazing flow is considered to be caused by an exciting pressure spectrum produced by the interaction of the grazing flow and the jets flowing from the resonator orifices. With this exciting pressure spectrum the resonator can be treated in the same manner as a resonator without grazing flow but with an exciting acoustic spectrum.

  20. Analogy electromagnetism-acoustics: Validation and application to local impedance active control for sound absorption

    NASA Astrophysics Data System (ADS)

    Nicolas, L.; Furstoss, M.; Galland, M. A.

    1998-10-01

    An analogy between electromagnetism and acoustics is presented in 2D. The propagation of sound in presence of absorbing material is modeled using an open boundary microwave package. Validation is performed through analytical and experimental results. Application to local impedance active control for free field sound absorption is finally described. Une analogie entre acoustique et électromagnétisme est présentée en 2D, afin de modéliser la propagation d'ondes acoustiques, en présence de matériau absorbant et à l'aide d'un logiciel de micro-ondes en domaine ouvert. Cette analogie est validée par des résultats analytiques et expérimentaux. Une application au contrôle actif de l'impédance acoustique de surface de matériaux poreux est finalement décrite.

  1. Contribution to classification of buried objects based on acoustic impedance matching.

    PubMed

    Stepanić, J; Wüstenberg, H; Krstelj, V; Mrasek, H

    2003-03-01

    Determination of material the buried objects are made of could contribute significantly to their recognition, or classification. This is important in detecting buried antipersonnel landmines within the context of humanitarian demining, as well as in a variety of other applications. In this article the concept has been formulated of the approach to buried object's material determination starting with ultrasonic impulse propagation analysis in a particular testing set configuration. The impulse propagates through a characterized transfer material in such a way that a part of it, a reflected wave, carries the information about the buried object's surface material acoustic impedance. The limit of resolution capability is theoretically analyzed and experimentally evaluated and the influencing factors described. Among these, the contact between clean surfaces of the transfer material and buried object is emphasized.

  2. Density, ultrasound velocity, acoustic impedance, reflection and absorption coefficient determination of liquids via multiple reflection method.

    PubMed

    Hoche, S; Hussein, M A; Becker, T

    2015-03-01

    The accuracy of density, reflection coefficient, and acoustic impedance determination via multiple reflection method was validated experimentally. The ternary system water-maltose-ethanol was used to execute a systematic, temperature dependent study over a wide range of densities and viscosities aiming an application as inline sensor in beverage industries. The validation results of the presented method and setup show root mean square errors of: 1.201E-3 g cm(-3) (±0.12%) density, 0.515E-3 (0.15%) reflection coefficient and 1.851E+3 kg s(-1) m(-2) (0.12%) specific acoustic impedance. The results of the diffraction corrected absorption showed an average standard deviation of only 0.12%. It was found that the absorption change shows a good correlation to concentration variations and may be useful for laboratory analysis of sufficiently pure liquids. The main part of the observed errors can be explained by the observed noise, temperature variation and the low signal resolution of 50 MHz. In particular, the poor signal-to-noise ratio of the second reflector echo was found to be a main accuracy limitation. Concerning the investigation of liquids the unstable properties of the reference material PMMA, due to hygroscopicity, were identified to be an additional, unpredictable source of uncertainty. While dimensional changes can be considered by adequate methodology, the impact of the time and temperature dependent water absorption on relevant reference properties like the buffer's sound velocity and density could not be considered and may explain part of the observed deviations.

  3. Bunch Length and Impedance Measurements at SPEAR3

    SciTech Connect

    Corbett, W.J.; Cheng, W.X.; Fisher, A.S.; Huang, X.; /SLAC

    2011-11-02

    Streak camera measurements were made at SPEAR3 to characterize longitudinal coupling impedance. For the nominal optics, data was taken at three rf voltages and a single-bunch current range of 0-20mA. Both bunchcentroid phase shift and bunch lengthening were recorded to extract values for resistive and reactive impedance. An (R+L) and a Q=1 model were then back-substituted into the Haissinski equation and compared with raw profile data. In the short bunch (low-{alpha}) mode, distribution 'bursting' was observed.

  4. Sensorless battery temperature measurements based on electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Raijmakers, L. H. J.; Danilov, D. L.; van Lammeren, J. P. M.; Lammers, M. J. G.; Notten, P. H. L.

    2014-02-01

    A new method is proposed to measure the internal temperature of (Li-ion) batteries. Based on electrochemical impedance spectroscopy measurements, an intercept frequency (f0) can be determined which is exclusively related to the internal battery temperature. The intercept frequency is defined as the frequency at which the imaginary part of the impedance is zero (Zim = 0), i.e. where the phase shift between the battery current and voltage is absent. The advantage of the proposed method is twofold: (i) no hardware temperature sensors are required anymore to monitor the battery temperature and (ii) the method does not suffer from heat transfer delays. Mathematical analysis of the equivalent electrical-circuit, representing the battery performance, confirms that the intercept frequency decreases with rising temperatures. Impedance measurements on rechargeable Li-ion cells of various chemistries were conducted to verify the proposed method. These experiments reveal that the intercept frequency is clearly dependent on the temperature and does not depend on State-of-Charge (SoC) and aging. These impedance-based sensorless temperature measurements are therefore simple and convenient for application in a wide range of stationary, mobile and high-power devices, such as hybrid- and full electric vehicles.

  5. Measuring the acoustic response of Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Monteiro, Martín; Marti, Arturo C.; Vogt, Patrik; Kasper, Lutz; Quarthal, Dominik

    2015-04-01

    Many experiments have been proposed to investigate acoustic phenomena in college and early undergraduate levels, in particular the speed of sound,1-9 by means of different methods, such as time of flight, transit time, or resonance in tubes. In this paper we propose to measure the acoustic response curves of a glass beaker filled with different gases, used as an acoustic resonator. We show that these curves expose many interesting peaks and features, one of which matches the resonance peak predicted for a Helmholtz resonator fairly well, and gives a decent estimate for the speed of sound in some cases. The measures are obtained thanks to the capabilities of smartphones.

  6. High Dynamic Range Complex Impedance Measurement System for Petrophysical Usage

    NASA Astrophysics Data System (ADS)

    Chen, R.; He, X.; Yao, H.; Tan, S.; Shi, H.; Shen, R.; Yan, C.; Zeng, P.; He, L.; Qiao, N.; Xi, F.; Zhang, H.; Xie, J.

    2015-12-01

    Spectral induced polarization method (SIP) or complex resistivity method is increasing its application in metalliferous ore exploration, hydrocarbon exploration, underground water exploration, monitoring of environment pollution, and the evaluation of environment remediation. And the measurement of complex resistivity or complex impedance of rock/ore sample and polluted water plays a fundamental role in improving the application effect of SIP and the application scope of SIP. However, current instruments can't guaranty the accuracy of measurement when the resistance of sample is less than 10Ω or great than 100kΩ. A lot of samples, such as liquid, polluted sea water, igneous rock, limestone, and sandstone, can't be measured with reliable complex resistivity result. Therefore, this problem projects a shadow in the basic research and application research of SIP. We design a high precision measurement system from the study of measurement principle, sample holder, and measurement instrument. We design input buffers in a single board. We adopt operation amplifier AD549 in this system because of its ultra-high input impedance and ultra-low current noise. This buffer is good in acquiring potential signal across high impedance sample. By analyzing the sources of measurement error and errors generated by the measurement system, we propose a correction method to remove the error in order to achieve high quality complex impedance measurement for rock and ore samples. This measurement system can improve the measurement range of the complex impedance to 0.1 Ω ~ 10 GΩ with amplitude error less than 0.1% and phase error less than 0.1mrad when frequency ranges as 0.01 Hz ~ 1 kHz. We tested our system on resistors with resistance as 0.1Ω ~ 10 GΩ in frequency range as 1 Hz ~ 1000 Hz, and the measurement error is less than 0.1 mrad. We also compared the result with LCR bridge and SCIP, we can find that the bridge's measuring range only reaches 100 MΩ, SCIP's measuring range

  7. Reproducibility experiments on measuring acoustical properties of rigid-frame porous media (round-robin tests).

    PubMed

    Horoshenkov, Kirill V; Khan, Amir; Bécot, François-Xavier; Jaouen, Luc; Sgard, Franck; Renault, Amélie; Amirouche, Nesrine; Pompoli, Francesco; Prodi, Nicola; Bonfiglio, Paolo; Pispola, Giulio; Asdrubali, Francesco; Hübelt, Jörn; Atalla, Noureddine; Amédin, Celse K; Lauriks, Walter; Boeckx, Laurens

    2007-07-01

    This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex acoustic impedance at normal incidence and plane wave absorption coefficient which are determined using the standard impedance tube method. The paper provides detailed procedures related to sample preparation and installation and it discusses the dispersion in the acoustical material property observed between individual material samples and laboratories. The importance of the boundary conditions, homogeneity of the porous material structure, and stability of the adopted signal processing method are highlighted.

  8. Measurement of the Impedance of Frog Skeletal Muscle Fibers

    PubMed Central

    Valdiosera, R.; Clausen, C.; Eisenberg, R. S.

    1974-01-01

    Impedance measurements are necessary to determine the passive electrical properties of cells including the equivalent circuits of the several pathways for current flow. Such measurements are usually made with microelectrodes of high impedance (some 15 MΩ) over a wide frequency range (1-10,000 Hz) and so are subject to many errors. An input amplifier has been developed which has negligible phase shift in this frequency range because it uses negative feedback to keep tiny the voltage on top of the microelectrode. An important source of artifact is the extracellular potential produced by capacitive current flow through the wall of the microelectrodes and the effective resistance of the bathing solution. This artifact is reduced some 10 times by shielding the current microelectrode with a conductive paint. The residual artifact is analyzed, measured, and subtracted from our results. The interelectrode coupling capacitance is reduced below 2 × 10-17 F and can be neglected. Phase and amplitude measurements are made with phase-sensitive detectors insensitive to noise. The entire apparatus is calibrated at different signal to noise ratios and the nature of the extracellular potential is investigated. The phase shift in the last 5-20 μm of the microelectrode tip is shown to be small and quite independent of frequency under several conditions. Experimental measurements of the phase characteristic of muscle fibers in normal Ringer are presented. The improvements in apparatus and the physiological significance of impedance measurements are discussed. It is suggested that the interpretation of impedance measurements is sensitive to small errors and so it is necessary to present objective evidence of the reliability of one's apparatus and measurements. PMID:4857358

  9. Acoustic Measurements for Small Solid Rocket Motors

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Kenny, R. Jeremy

    2010-01-01

    Models have been developed to predict large solid rocket motor acoustic loads based on the scaling of small solid rocket motors. MSFC has measured several small solid rocket motors in horizontal and launch configurations to anchor these models. Solid Rocket Test Motor (SRTM) has ballistics similar to the Reusable Solid Rocket Motor (RSRM) therefore a good choice for acoustic scaling. Acoustic measurements were collected during the test firing of the Insulation Configuration Extended Length (ICXL) 7,6, and 8 (in firing order) in order to compare to RSRM horizontal firing data. The scope of this presentation includes: Acoustic test procedures and instrumentation implemented during the three SRTM firings and Data analysis method and general trends observed in the data.

  10. Noninvasive measurement of transdermal drug delivery by impedance spectroscopy

    PubMed Central

    Arpaia, Pasquale; Cesaro, Umberto; Moccaldi, Nicola

    2017-01-01

    The effectiveness in transdermal delivery of skin permeation strategies (e.g., chemical enhancers, vesicular carrier systems, sonophoresis, iontophoresis, and electroporation) is poorly investigated outside of laboratory. In therapeutic application, the lack of recognized techniques for measuring the actually-released drug affects the scientific concept itself of dosage for topically- and transdermally-delivered drugs. Here we prove the suitability of impedance measurement for assessing the amount of drug penetrated into the skin after transdermal delivery. In particular, the measured amount of drug depends linearly on the impedance magnitude variation normalized to the pre-treated value. Three experimental campaigns, based on the electrical analysis of the biological tissue behavior due to the drug delivery, are reported: (i) laboratory emulation on eggplants, (ii) ex-vivo tests on pig ears, and finally (iii) in-vivo tests on human volunteers. Results point out that the amount of delivered drug can be assessed by reasonable metrological performance through a unique measurement of the impedance magnitude at one single frequency. In particular, in-vivo results point out sensitivity of 23 ml−1, repeatability of 0.3%, non-linearity of 3.3%, and accuracy of 5.7%. Finally, the measurement resolution of 0.20 ml is compatible with clinical administration standards. PMID:28338008

  11. Determination of Complex Microcalorimeter Parameters with Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Saab, T.; Bandler, S. R.; Chervenak, J.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C. A.; Lindeman, M. A.; Porter, F. S.; Sadleir, J.

    2005-01-01

    The proper understanding and modeling of a microcalorimeter s response requires the accurate knowledge of a handful of parameters, such as C, G, alpha, . . . . While a few of these, such 8s the normal state resistance and the total thermal conductance to the heat bath (G) are directly determined from the DC IV characteristics, some others, notoriously the heat capacity (C) and alpha, appear in degenerate combinations in most measurable quantities. The case of a complex microcalorimeter, i.e. one in which the absorber s heat capacity is connected by a finite thermal impedance to the sensor, and subsequently by another thermal impedance to the heat bath, results in an added ambiguity in the determination of the individual C's and G's. In general, the dependence of the microcalorimeter s complex impedance on these parameters varies with frequency. This variation allows us to determine the individual parameters by fitting the prediction of the microcalorimeter model to the impedance data. We describe in this paper our efforts at characterizing the Goddard X-ray microcalorimeters. Using the parameters determined with this method we them compare the pulse shape and noise spectra predicted by the microcalorimeter model to data taken with the same devices.

  12. Contactless impedance sensors and their application to flow measurements.

    PubMed

    Opekar, František; Tůma, Petr; Stulík, Karel

    2013-02-27

    The paper provides a critical discussion of the present state of the theory of high-frequency impedance sensors (now mostly called contactless impedance or conductivity sensors), the principal approaches employed in designing impedance flow-through cells and their operational parameters. In addition to characterization of traditional types of impedance sensors, the article is concerned with the use of less common sensors, such as cells with wire electrodes or planar cells. There is a detailed discussion of the effect of the individual operational parameters (width and shape of the electrodes, detection gap, frequency and amplitude of the input signal) on the response of the detector. The most important problems to be resolved in coupling these devices with flow-through measurements in the liquid phase are also discussed. Examples are given of cell designs for continuous flow and flow-injection analyses and of detection systems for miniaturized liquid chromatography and capillary electrophoresis. New directions for the use of these sensors in molecular biology and chemical reactors and some directions for future development are outlined.

  13. Acoustic Doppler discharge-measurement system

    USGS Publications Warehouse

    Simpson, Michael R.; Oltmann, Richard N.; ,

    1990-01-01

    A discharge-measurement system that uses a vessel-mounted acoustic Doppler current profiler has been developed and tested by the U.S. Geological Survey. Discharge measurements using the system require a fraction of the time needed for conventional current-meter discharge measurements and do not require shore-based navigational aids or tag lines for positioning the vessel.

  14. Probe impedance measurements for millimeter-wave integrated horn antennas

    NASA Technical Reports Server (NTRS)

    Guo, Yong; Chiao, Jung-Chih; Potter, Kent A.; Rutledge, David B.

    1993-01-01

    In order to achieve an impedance-matched millimeter-wave integrated horn antenna mixer array, the characteristics of the antenna probes inside the horn must be known. This paper describes impedance measurements for various probes in low-frequency model horns of two different types: (1) a 3 x 3 array made of aluminum by electric discharge machining and (2) a half horn made of copper sheet placed on a big copper-clad circuit board that was used as an image plane. The results of measurements indicate that the presence of the horn increases the effective length of the probe element, in agreement with reports of Guo et al. (1991) and theoretical analysis of Eleftheriades et al. (1991). It was also found that the resonant frequencies can be controlled by changing the length of the probes or by loading the probes.

  15. Multiscale analysis of the acoustic scattering by many scatterers of impedance type

    NASA Astrophysics Data System (ADS)

    Challa, Durga Prasad; Sini, Mourad

    2016-06-01

    We are concerned with the acoustic scattering problem, at a frequency {κ}, by many small obstacles of arbitrary shapes with impedance boundary condition. These scatterers are assumed to be included in a bounded domain {Ω} in {{R}^3} which is embedded in an acoustic background characterized by an eventually locally varying index of refraction. The collection of the scatterers {D_m, m=1,ldots,M} is modeled by four parameters: their number M, their maximum radius a, their minimum distance d and the surface impedances {λ_m, m=1,ldots,M}. We consider the parameters M, d and {λ_m}'s having the following scaling properties: {M:=M(a)=O(a^{-s}), d:=d(a)≈ a^t} and {λ_m:=λ_m(a)=λ_{m,0}a^{-β}}, as {a→ 0}, with non negative constants s, t and {β} and complex numbers {λ_{m, 0}}'s with eventually negative imaginary parts. We derive the asymptotic expansion of the far-fields with explicit error estimate in terms of a, as {a→ 0}. The dominant term is the Foldy-Lax field corresponding to the scattering by the point-like scatterers located at the centers {z_m}'s of the scatterers {D_m}'s with {λ_m \\vert partial D_m\\vert} as the related scattering coefficients. This asymptotic expansion is justified under the following conditions a ≤ a_0, \\vert Re (λ_{m,0})\\vert ≥ λ_-,quad \\vertλ_{m,0}\\vert ≤ λ_+,quad β < 1,quad 0 ≤ s ≤2-β,quads/3 ≤ t and the error of the approximation is {C a^{3-2β-s}}, as {a → 0}, where the positive constants {a_0, λ_-,λ_+} and C depend only on the a priori uniform bounds of the Lipschitz characters of the obstacles {D_m}'s and the ones of {M(a)a^s} and {d(a)/a^t}. We do not assume the periodicity in distributing the small scatterers. In addition, the scatterers can be arbitrary close since t can be arbitrary large, i.e., we can handle the mesoscale regime. Finally, for spherical scatterers, we can also allow the limit case {β=1} with a slightly better error of the approximation.

  16. Drag Measurements of Porous Plate Acoustic Liners

    NASA Technical Reports Server (NTRS)

    Wolter, John D.

    2005-01-01

    This paper presents the results of direct drag measurements on a variety of porous plate acoustic liners. The existing literature describes numerous studies of drag on porous walls with injection or suction, but relatively few of drag on porous plates with neither injection nor suction. Furthermore, the porosity of the porous plate in existing studies is much lower than typically used in acoustic liners. In the present work, the acoustic liners consisted of a perforated face sheet covering a bulk acoustic absorber material. Factors that were varied in the experiment were hole diameter, hole pattern, face sheet thickness, bulk material type, and size of the gap (if any) between the face sheet and the absorber material.

  17. Unfolding plasma density from cylindrical monopole impedance measurements in ionosphere

    NASA Astrophysics Data System (ADS)

    Kiraga, A.

    2003-04-01

    Several common problems occur in measurement techniques and interpretation of plasma natural emissions and impedance data. Antenna characteristics are of prime importance in equivalent circuit analysis. Spacecraft - plasma interaction contributes to variability of equivalent circuit impedances and e.m.f. components and imposes constrains on usefulness of experimental data. In order to have independent, built in estimate of local plasma frequency and to get deeper insight into properties of equivalent circuit for wave diagnostics, impedance measurement was integrated with radio receivers on the ACTIVE, APEX and CORONAS satellites. Impedance measurements of 7.5m long monopole were performed in frequency range .1-10MHz with the frequency step of 50kHz, in voltage divider configuration. Due to high inclination of 82.5deg and altitude range of 500-3000km, data from very different plasmas were collected. Data can be split into quasi normal, disturbed and very disturbed measurements. Equivalent circuit structure evolved in attempt to match even very disturbed measurements. For quasi normal measurements, satisfactory matching is obtained with computed gyrofrequency fc and fitted plasma frequency fn, stray capacitance Cs and capacitance Cv of phenomenological vacuum sheath. With formulas for monopole impedance in cold magnetoplasma, two basic pectral structures are explained. For sufficiently magnetized plasma (roughly fn/fc<2 if Cs=20pF), circuit parallel resonance frequency Fr falls into upper hybrid band (max(fn,fc),fu), resonance amplitude is reduced by high antenna resistance and horn like absolute maximum points fu. For values of fn/fc ratio, greater then critical, Fr is less than fn and broad absolute maximum at Fr follows from low antenna resistance. Further increase of fn/fc results in increasing lag of Fr behind fn. Critical ratio fn/fc increases with decreasing stray capacitance Cs. It follows from data analysis that stray capacitance may change in flight, at

  18. Damage Diagnosis in Semiconductive Materials Using Electrical Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Ross, Richard W.; Hinton, Yolanda L.

    2008-01-01

    Recent aerospace industry trends have resulted in an increased demand for real-time, effective techniques for in-flight structural health monitoring. A promising technique for damage diagnosis uses electrical impedance measurements of semiconductive materials. By applying a small electrical current into a material specimen and measuring the corresponding voltages at various locations on the specimen, changes in the electrical characteristics due to the presence of damage can be assessed. An artificial neural network uses these changes in electrical properties to provide an inverse solution that estimates the location and magnitude of the damage. The advantage of the electrical impedance method over other damage diagnosis techniques is that it uses the material as the sensor. Simple voltage measurements can be used instead of discrete sensors, resulting in a reduction in weight and system complexity. This research effort extends previous work by employing finite element method models to improve accuracy of complex models with anisotropic conductivities and by enhancing the computational efficiency of the inverse techniques. The paper demonstrates a proof of concept of a damage diagnosis approach using electrical impedance methods and a neural network as an effective tool for in-flight diagnosis of structural damage to aircraft components.

  19. The neonatal acoustic reflex.

    PubMed

    Weatherby, L A; Bennett, M J

    1980-01-01

    Probe tones from 220 Hz to 2 000 Hz were used to measure the static and dynamic acoustic impedance of 44 neonates. Acoustic reflex thresholds to broad band noise were obtained from every neonate tested when employing the higher frequency probe tones. The reflex threshold levels measured are similar to those of adults. The static impedance values are discussed to give a possible explanation of why reflex thresholds cannot be detected using conventional 220 Hz impedance bridges.

  20. Cryogenic calibration setup for broadband complex impedance measurements

    NASA Astrophysics Data System (ADS)

    Diener, P.; Couëdo, F.; Marrache-Kikuchi, C.; Aprili, M.; Gabelli, J.

    2014-08-01

    Reflection measurements give access to the complex impedance of a material on a wide frequency range. This is of interest to study the dynamical properties of various materials, for instance disordered superconductors. However reflection measurements made at cryogenic temperature suffer from the difficulty to reliably subtract the circuit contribution. Here we report on the design and first tests of a setup able to precisely calibrate in situ the sample reflection, at 4.2 K and up to 2 GHz, by switching and measuring, during the same cool down, the sample and three calibration standards.

  1. Nuclear radiation-warning detector that measures impedance

    DOEpatents

    Savignac, Noel Felix; Gomez, Leo S; Yelton, William Graham; Robinson, Alex; Limmer, Steven

    2013-06-04

    This invention is a nuclear radiation-warning detector that measures impedance of silver-silver halide on an interdigitated electrode to detect light or radiation comprised of alpha particles, beta particles, gamma rays, X rays, and/or neutrons. The detector is comprised of an interdigitated electrode covered by a layer of silver halide. After exposure to alpha particles, beta particles, X rays, gamma rays, neutron radiation, or light, the silver halide is reduced to silver in the presence of a reducing solution. The change from the high electrical resistance (impedance) of silver halide to the low resistance of silver provides the radiation warning that detected radiation levels exceed a predetermined radiation dose threshold.

  2. Effect of borehole design on electrical impedance tomography measurements

    NASA Astrophysics Data System (ADS)

    Mozaffari, Amirpasha; Huisman, Johan Alexander; Treichel, Andrea; Zimmermann, Egon; Kelter, Matthias; Vereecken, Harry

    2015-04-01

    Electrical Impedance Tomography (EIT) is a sophisticated non-invasive tool to investigate the subsurface in engineering and environmental studies. To increase the depth of investigation, EIT measurements can be made in boreholes. However, the presence of the borehole may affect EIT measurements. Here, we aim to investigate the effect of different borehole components on EIT measurements using 2,5-D and 3D finite element modeling and unstructured meshes. To investigate the effect of different borehole components on EIT measurements, a variety of scenarios were designed. In particular, the effect of the water-filled borehole, the PVC casing, and the gravel filter were investigated relative to complex resistivity simulations for a homogenous medium with chain and electrode modules. It was found that the results of the complex resistivity simulations were best understood using the sensitivity distribution of the electrode configuration under consideration. In all simulations, the sensitivity in the vicinity of the borehole was predominantly negative. Therefore, the introduction of the water-filled borehole caused an increase in the real part of the impedance, and a decrease (more negative) in the imaginary part of the simulated impedance. The PVC casing mostly enhanced the effect of the water-filled borehole described above, although this effect was less clear for some electrode configuration. The effect of the gravel filter mostly reduced the effect of the water-filled borehole with PVC casing. For EIT measurements in a single borehole, the highest simulated phase error was 12% for a Wenner configuration with electrode spacing of 0.33 m. This error decreased with increasing electrode spacing. In the case of cross-well configurations, the error in the phase shit was as high as 6%. Here, it was found that the highest errors occur when both current electrodes are located in the same borehole. These results indicated that cross-well measurements are less affected by the

  3. Body Fat Measurement: Weighing the Pros and Cons of Electrical Impedance.

    ERIC Educational Resources Information Center

    Nash, Heyward L.

    1985-01-01

    Research technologists have developed electrical impedance units in response to demand for a convenient and reliable method of measuring body fat. Accuracy of impedance measures versus calipers and underwater weighing are discussed. (MT)

  4. Design of broadband time-domain impedance boundary conditions using the oscillatory-diffusive representation of acoustical models.

    PubMed

    Monteghetti, Florian; Matignon, Denis; Piot, Estelle; Pascal, Lucas

    2016-09-01

    A methodology to design broadband time-domain impedance boundary conditions (TDIBCs) from the analysis of acoustical models is presented. The derived TDIBCs are recast exclusively as first-order differential equations, well-suited for high-order numerical simulations. Broadband approximations are yielded from an elementary linear least squares optimization that is, for most models, independent of the absorbing material geometry. This methodology relies on a mathematical technique referred to as the oscillatory-diffusive (or poles and cuts) representation, and is applied to a wide range of acoustical models, drawn from duct acoustics and outdoor sound propagation, which covers perforates, semi-infinite ground layers, as well as cavities filled with a porous medium. It is shown that each of these impedance models leads to a different TDIBC. Comparison with existing numerical models, such as multi-pole or extended Helmholtz resonator, provides insights into their suitability. Additionally, the broadly-applicable fractional polynomial impedance models are analyzed using fractional calculus.

  5. Study of surfactant-skin interactions by skin impedance measurements.

    PubMed

    Lu, Guojin; Moore, David J

    2012-02-01

    The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation.

  6. Stability analysis and design of time-domain acoustic impedance boundary conditions for lined duct with mean flow.

    PubMed

    Liu, Xin; Huang, Xun; Zhang, Xin

    2014-11-01

    This work develops the so-called compensated impedance boundary conditions that enable stable time domain simulations of sound propagation in a lined duct with uniform mean flow, which has important practical interest for noise emission by aero-engines. The proposed method is developed analytically from an unusual perspective of control that shows impedance boundary conditions act as closed-loop feedbacks to an overall duct acoustic system. It turns out that those numerical instabilities of time domain simulations are caused by deficient phase margins of the corresponding control-oriented model. A particular instability of very low frequencies in the presence of steady uniform background mean flow, in addition to the well known high frequency numerical instabilities at the grid size, can be identified using this analysis approach. Stable time domain impedance boundary conditions can be formulated by including appropriate phaselead compensators to achieve desired phase margins. The compensated impedance boundary conditions can be simply designed with no empirical parameter, straightforwardly integrated with ordinary linear acoustic models, and efficiently calculated with no need of resolving sheared boundary layers. The proposed boundary conditions are validated by comparing against asymptotic solutions of spinning modal sound propagation in a duct with a hard-soft interface and reasonable agreement is achieved.

  7. Acoustic Measurement of Potato Cannon Velocity

    ERIC Educational Resources Information Center

    Courtney, Michael; Courtney, Amy

    2007-01-01

    Potato cannon velocity can be measured with a digitized microphone signal. A microphone is attached to the potato cannon muzzle, and a potato is fired at an aluminum target about 10 m away. Flight time can be determined from the acoustic waveform by subtracting the time in the barrel and time for sound to return from the target. The potato…

  8. Acoustical measurements in ancient Roman theatres

    NASA Astrophysics Data System (ADS)

    Farnetani, Andrea; Fausti, Patrizio; Pompoli, Roberto; Prodi, Nicola

    2004-05-01

    The Greek and Roman theatres are among the most precious and spectacular items of cultural heritage in the Mediterranean countries. The theatres are famous not only for their impressive architecture, but also for the acoustic qualities. For this reason it is important to consider these theatres as an acoustical heritage and to study their sound field. Within the activities of the ERATO (identification Evaluation and Revival of the Acoustical heritage of ancient Theatres and Odea) project, acoustical measurements were taken in well-preserved ancient Roman theatres at Aspendos (Turkey) and Jerash (Jordan). Roman theatres have an impressive stage building that forms a back wall in the orchestra area, and it was found that, from the analysis of the acoustical parameters, the reverberation time (e.g., 1.7 s at middle frequencies in the theatre of Aspendos) is quite long compared not only with other open-space theatres but also with closed spaces. Contrary to modern halls the clarity is high and this fact, together with a low sound level in most of the seats, gives the sound field a unique character.

  9. Crosstalk Compensation for a Rapid, Higher Resolution Impedance Spectrum Measurement

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; David M. Rose; William H. Morrison; Chester G. Motloch

    2012-03-01

    Batteries and other energy storage devices are playing larger roles in various industries (e.g., military, automotive, electric utilities, etc.) as the U.S. seeks to reduce its dependence on foreign energy resources. As such, there exists a significant need for accurate, robust state-of-health assessment techniques. Present techniques tend to focus on simple, passive monitoring of voltage and current at a given ambient temperature. However, this approach has the disadvantage of ignoring key elements of health, that is, changes in resistance growth and power fade. Impedance spectroscopy is considered a useful laboratory tool in gauging changes in the resistance and power performance, but it has not been widely considered as an onboard diagnostic tool due to the length of time required to complete the measurement. Cross-Talk Compensation (CTC) is a novel approach that enables rapid, high resolution impedance spectra measurements using a hardware platform that could be designed as an embedded system. This input signal consists of a sum-of-sines excitation current that has a known frequency spread and a duration of one period of the lowest frequency. The voltage response is then captured at a sufficiently fast sample rate. Previously developed rapid impedance spectrum measurement techniques either required a longer excitation signal or a sum-of-sines signal that was separated by harmonic frequencies to reduce or eliminate, respectively, the cross-talk interference in the calculated results. The distinct advantage of CTC, however, is that non-harmonic frequencies can now be included within the excitation signal while still keeping the signal duration at one period of the lowest frequency. Since the frequency spread of the input signal is known, the crosstalk interference between sinusoidal signals within the sum-of-sines at a given frequency of interest can be pre-determined and assigned to an error matrix. Consequently, the real and imaginary components of the

  10. Auditory evoked field measurement using magneto-impedance sensors

    SciTech Connect

    Wang, K. Tajima, S.; Song, D.; Uchiyama, T.; Hamada, N.; Cai, C.

    2015-05-07

    The magnetic field of the human brain is extremely weak, and it is mostly measured and monitored in the magnetoencephalography method using superconducting quantum interference devices. In this study, in order to measure the weak magnetic field of the brain, we constructed a Magneto-Impedance sensor (MI sensor) system that can cancel out the background noise without any magnetic shield. Based on our previous studies of brain wave measurements, we used two MI sensors in this system for monitoring both cerebral hemispheres. In this study, we recorded and compared the auditory evoked field signals of the subject, including the N100 (or N1) and the P300 (or P3) brain waves. The results suggest that the MI sensor can be applied to brain activity measurement.

  11. Auditory evoked field measurement using magneto-impedance sensors

    NASA Astrophysics Data System (ADS)

    Wang, K.; Tajima, S.; Song, D.; Hamada, N.; Cai, C.; Uchiyama, T.

    2015-05-01

    The magnetic field of the human brain is extremely weak, and it is mostly measured and monitored in the magnetoencephalography method using superconducting quantum interference devices. In this study, in order to measure the weak magnetic field of the brain, we constructed a Magneto-Impedance sensor (MI sensor) system that can cancel out the background noise without any magnetic shield. Based on our previous studies of brain wave measurements, we used two MI sensors in this system for monitoring both cerebral hemispheres. In this study, we recorded and compared the auditory evoked field signals of the subject, including the N100 (or N1) and the P300 (or P3) brain waves. The results suggest that the MI sensor can be applied to brain activity measurement.

  12. Measurement of limb blood flow by electrical impedance plethysmography.

    PubMed Central

    Porter, J. M.; Swain, I. D.; Shakespeare, P. G.

    1985-01-01

    Limb blood flow has been measured in 72 individuals by the noninvasive technique of electrical impedance plethysmography. Venous occlusion was not used. Blood flow was measured in 230 limbs in which 195 limbs were either in normal individuals or the clinically normal limbs of patients (normal limbs). Thirty-five limbs were clinically abnormal. Measurements on limbs with clinical abnormalities showed that blood flow values often fell within the limits of the normal range. However 3 cases of known vascular injury and 2 cases studied after hand surgery under tourniquet showed lowered blood flow values by comparison with the unaffected limb. A simultaneously recorded range of cardiac output and stroke volume measurements gave similar results to those obtained in a previous, unconnected study. Images Fig. 1 PMID:4004047

  13. System for simultaneous measurements of bilaterally symmetrical acupoints multifrequency impedances.

    PubMed

    Su, Mi-Yong; Tan, Yong-Hong; Wang, Zi-Min; Gan, Cai-Jun; Chen, Shou-Hong

    2013-01-01

    Devices which can obtain comparable bilaterally symmetrical acupoints (BSA) multifrequency impedances (MFI) are often needed in the detection of the energy balance states of acupoints in traditional Chinese medicine. To satisfy these needs, a two-channel impedance measurement system has been introduced which is capable of accurately and simultaneously measuring BSA MFI. The system includes a set of five electrodes, two of which are injected with exciting current signal to synchronously and equally excite BSA; the other three electrodes are used as sensors to simultaneously sense the response signal from both sides. The system also includes a PC-based time-domain signal testing platform with arbitrary current waveform generation and three channels (one exciting current and two response voltages) simultaneously sampling, and a set of MFI simultaneously unbiased computing algorithms based on special odd multisine current signal input. Preliminary validating experiments suggest that the system allows accurate and synchronous measurement of BSA MFI at least in the frequency range of 10 Hz to 60 kHz, and the obtained BSA MFI are well comparable.

  14. Determination of acoustic impedances of multi matching layers for narrowband ultrasonic airborne transducers at frequencies <2.5 MHz - Application of a genetic algorithm.

    PubMed

    Saffar, Saber; Abdullah, Amir

    2012-01-01

    The effective ultrasonic energy radiation into the air of piezoelectric transducers requires using multilayer matching systems with accurately selected acoustic impedances and the thickness of particular layers. One major problem of ultrasonic transducers, radiating acoustic energy into air, is to find the proper acoustic impedances of one or more matching layers. This work aims at developing an original solution to the acoustic impedance mismatch between transducer and air. If the acoustic impedance defences between transducer and air be more, then finding best matching layer(s) is harder. Therefore we consider PZT (lead zirconate titanate piezo electric) transducer and air that has huge acoustic impedance deference. The vibration source energy (PZT), which is used to generate the incident wave, consumes a part of the mechanical energy and converts it to an electrical one in theoretical calculation. After calculating matching layers, we consider the energy source as layer to design a transducer. However, this part of the mechanical energy will be neglected during the mathematical work. This approximation is correct only if the transducer is open-circuit. Since the possibilities of choosing material with required acoustic impedance are limited (the counted values cannot always be realized and applied in practice) it is necessary to correct the differences between theoretical values and the possibilities of practical application of given acoustic impedances. Such a correction can be done by manipulating other parameters of matching layers (e.g. by changing their thickness). The efficiency of the energy transmission from the piezoceramic transducer through different layers with different thickness and different attenuation enabling a compensation of non-ideal real values by changing their thickness was computer analyzed (base on genetic algorithm). Firstly, three theoretical solutions were investigated. Namely, Chebyshev, Desilets and Souquet theories. However, the

  15. Quantitative assessment of impedance tomography for temperature measurements in hyperthermia.

    PubMed

    Blad, B; Persson, B; Lindström, K

    1992-01-01

    The objective of this study is a non-invasive assessment of the thermal dose in hyperthermia. Electrical impedance tomography (EIT) has previously been given a first trial as a temperature monitoring method together with microwave-induced hyperthermia treatment, but it has not been thoroughly investigated. In the present work we have examined this method in order to investigate the correlation in vitro between the true spatial temperature distribution and the corresponding measured relative resistivity changes. Different hyperthermia techniques, such as interstitial water tubings, microwave-induced, laser-induced and ferromagnetic seeds have been used. The results show that it is possible to find a correlation between the measured temperature values and the tomographically measured relative resistivity changes in tissue-equivalent phantoms. But the uncertainty of the temperature coefficients, which has been observed, shows that the method has to be improved before it can be applied to clinical in vivo applications.

  16. Detection of Chamber Conditioning Through Optical Emission and Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, Meyya

    2001-01-01

    During oxide etch processes, buildup of fluorocarbon residues on reactor sidewalls can cause run-to-run drift and will necessitate some time for conditioning and seasoning of the reactor. Though diagnostics can be applied to study and understand these phenomena, many of them are not practical for use in an industrial reactor. For instance, measurements of ion fluxes and energy by mass spectrometry show that the buildup of insulating fluorocarbon films on the reactor surface will cause a shift in both ion energy and current in an argon plasma. However, such a device cannot be easily integrated into a processing system. The shift in ion energy and flux will be accompanied by an increase in the capacitance of the plasma sheath. The shift in sheath capacitance can be easily measured by a common commercially available impedance probe placed on the inductive coil. A buildup of film on the chamber wall is expected to affect the production of fluorocarbon radicals, and thus the presence of such species in the optical emission spectrum of the plasma can be monitored as well. These two techniques are employed on a GEC (Gaseous Electronics Conference) Reference Cell to assess the validity of optical emission and impedance monitoring as a metric of chamber conditioning. These techniques are applied to experimental runs with CHF3 and CHF3/O2/Ar plasmas, with intermediate monitoring of pure argon plasmas as a reference case for chamber conditions.

  17. An Expendable Source for Measuring Shallow Water Acoustic Propagation and Geo-Acoustic Bottom Properties

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. An Expendable Source for Measuring Shallow Water Acoustic ...Propagation and Geo- Acoustic Bottom Properties Harry A DeFerrari RSMAS – University of Miami 4600 Rickenbacker Causeway Miami FL. 33149...broadband source is being developed that transmits high gain m-sequence to clandestinly measure pulse response of shallow water acoustic propagation

  18. Simultaneous backward data transmission and power harvesting in an ultrasonic transcutaneous energy transfer link employing acoustically dependent electric impedance modulation.

    PubMed

    Ozeri, Shaul; Shmilovitz, Doron

    2014-09-01

    The advancement and miniaturization of body implanted medical devices pose several challenges to Ultrasonic Transcutaneous Energy Transfer (UTET), such as the need to reduce the size of the piezoelectric resonator, and the need to maximize the UTET link power-transfer efficiency. Accordingly, the same piezoelectric resonator that is used for energy harvesting at the body implant, may also be used for ultrasonic backward data transfer, for instance, through impedance modulation. This paper presents physical considerations and design guidelines of the body implanted transducer of a UTET link with impedance modulation for a backward data transfer. The acoustic matching design procedure was based on the 2×2 transfer matrix chain analysis, in addition to the Krimholtz Leedom and Matthaei KLM transmission line model. The UTET power transfer was carried out at a frequency of 765 kHz, continuous wave (CW) mode. The backward data transfer was attained by inserting a 9% load resistance variation around its matched value (550 Ohm), resulting in a 12% increase in the acoustic reflection coefficient. A backward data transmission rate of 1200 bits/s was experimentally demonstrated using amplitude shift keying, simultaneously with an acoustic power transfer of 20 mW to the implant.

  19. Grinding process monitoring based on electromechanical impedance measurements

    NASA Astrophysics Data System (ADS)

    Marchi, Marcelo; Guimarães Baptista, Fabricio; de Aguiar, Paulo Roberto; Bianchi, Eduardo Carlos

    2015-04-01

    Grinding is considered one of the last processes in precision parts manufacturing, which makes it indispensable to have a reliable monitoring system to evaluate workpiece surface integrity. This paper proposes the use of the electromechanical impedance (EMI) method to monitor the surface grinding operation in real time, particularly the surface integrity of the ground workpiece. The EMI method stands out for its simplicity and for using low-cost components such as PZT (lead zirconate titanate) piezoelectric transducers. In order to assess the feasibility of applying the EMI method to the grinding process, experimental tests were performed on a surface grinder using a CBN grinding wheel and a SAE 1020 steel workpiece, with PZT transducers mounted on the workpiece and its holder. During the grinding process, the electrical impedance of the transducers was measured and damage indices conventionally used in the EMI method were calculated and compared with workpiece wear, indicating the surface condition of the workpiece. The experimental results indicate that the EMI method can be an efficient and cost-effective alternative for monitoring precision workpieces during the surface grinding process.

  20. Antenna impedance measurements in a magnetized plasma. I. Spherical antenna

    SciTech Connect

    Blackwell, David D.; Walker, David N.; Messer, Sarah J.; Amatucci, William E.

    2007-09-15

    The input impedance of a metal sphere immersed in a magnetized plasma is measured with a network analyzer at frequencies up to 1 GHz. The experiments were done in the Space Physics Simulation Chamber at the Naval Research Laboratory. The hot-filament argon plasma was varied between weakly ({omega}{sub ce}<{omega}{sub pe}) and strongly ({omega}{sub ce}>{omega}{sub pe}) magnetized plasma with electron densities in the range 10{sup 7}-10{sup 10} cm{sup -3}. It is observed that the lower-frequency resonance of the impedance characteristic previously associated with series sheath resonance {omega}{sub sh} in the unmagnetized plasma occurs at a hybrid sheath frequency of {omega}{sub r}{sup 2}={omega}{sub sh}{sup 2}+{kappa}{omega}{sub ce}{sup 2}, where {kappa} is a constant 0.5<{kappa}<1. As seen in previous experiments, the higher frequency resonance associated with the electron plasma frequency {omega}{sub pe} in the unmagnetized plasma is relocated to the upper hybrid frequency {omega}{sub uh}{sup 2}={omega}{sub pe}{sup 2}+{omega}{sub ce}{sup 2}. As with the unmagnetized plasma, the maximum power deposition occurs at the lower frequency resonance {omega}{sub r}.

  1. Measuring Acoustic Noise around Kahoolawe Island.

    DTIC Science & Technology

    1981-10-01

    NAVAL OCEAN SYSTEMS CENTER SAN DIEGO, CALIFORNIA 92152 C y 2 .V ANAVAL OCEAN SYSTEMS CENTER, SAN DIEGO, CA 92152 AN ACTIV IT Y OF THE NAVAL... Ocean Systems Center (NOSC), Code 512, on NSAP Project TH-1 -80, "Measurement of Acoustic Noise Around Kahoolawe". CDR J. W. Carlmark, USN, COMTHIRDFLT N...Bioacoustics & Bionics Division Biosciences Department ,or -.. .- ?---1 1 : ’" " "’ .... .-j UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data

  2. Improved multimodal method for the acoustic propagation in waveguides with a wall impedance and a uniform flow

    NASA Astrophysics Data System (ADS)

    Mercier, Jean-François; Maurel, Agnès

    2016-06-01

    We present an efficient multimodal method to describe the acoustic propagation in the presence of a uniform flow in a waveguide with locally a wall impedance treatment. The method relies on a variational formulation of the problem, which allows to derive a multimodal formulation within a rigorous mathematical framework, notably to properly account for the boundary conditions on the walls (being locally the Myers condition and the Neumann condition otherwise). Also, the method uses an enriched basis with respect to the usual cosine basis, able to absorb the less converging part of the modal series and thus, to improve the convergence of the method. Using the cosine basis, the modal method has a low convergence, 1/N, with N the order of truncation. Using the enriched basis, the improvement in the convergence is shown to depend on the Mach number, from 1/N5 to roughly 1/N1.5 for M=0 to M close to unity. The case of a continuously varying wall impedance is considered, and we discuss the limiting case of piecewise constant impedance, which defines pressure edge conditions at the impedance discontinuities.

  3. Measuring acoustic emissions in an avalanche slope

    NASA Astrophysics Data System (ADS)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

    Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

  4. Acoustic Doppler velocimeter-induced acoustic streaming and its implications for measurement

    NASA Astrophysics Data System (ADS)

    Poindexter, C. M.; Rusello, P. J.; Variano, E. A.

    2011-05-01

    The acoustic Doppler velocimeter (ADV) is widely used for the characterization of fluid flow. Secondary flows ("acoustic streaming") generated by the ADV's acoustic pulses may affect the accuracy of measurements in experiments with small velocities. We assessed the impact of acoustic streaming on flow measurement using particle image velocimetry. The probes of two different ADVs were successively mounted in a tank of quiescent water. The probes' ultrasound emitters were aligned with a laser light sheet. Observed flow was primarily in the axial direction, accelerating from the ultrasound emitter and peaking within centimeters of the velocimeter sampling volume before dropping off. We measured the dependence of acoustic streaming velocity on ADV configuration, finding that different settings induce streaming ranging from negligible to more than 2.0 cm s-1. From these results, we describe cases where acoustic streaming affects velocity measurements and also cases where ADVs accurately measure their own acoustic streaming.

  5. Measurements of acoustic sources in motion

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Norum, T. D.

    1978-01-01

    Results of the far-field pressures measured from three different types of moving sources are presented. These acoustic sources consist of a point monopole, a small model jet, and an aircraft. Results for the pressure time history produced by the point source show good agreement with those predicted analytically. Both actual and simulated forward motion of the model jet show reductions in noise levels with forward speed at all angles between the source and observer. Measurement with the aircraft over both an anechoic floor and over the ground yields a method for evaluating the transfer function for ground reflections at various angles between the moving aircraft and measurement position.

  6. Measured acoustic properties of variable and low density bulk absorbers

    NASA Technical Reports Server (NTRS)

    Dahl, M. D.; Rice, E. J.

    1985-01-01

    Experimental data were taken to determine the acoustic absorbing properties of uniform low density and layered variable density samples using a bulk absober with a perforated plate facing to hold the material in place. In the layered variable density case, the bulk absorber was packed such that the lowest density layer began at the surface of the sample and progressed to higher density layers deeper inside. The samples were placed in a rectangular duct and measurements were taken using the two microphone method. The data were used to calculate specific acoustic impedances and normal incidence absorption coefficients. Results showed that for uniform density samples the absorption coefficient at low frequencies decreased with increasing density and resonances occurred in the absorption coefficient curve at lower densities. These results were confirmed by a model for uniform density bulk absorbers. Results from layered variable density samples showed that low frequency absorption was the highest when the lowest density possible was packed in the first layer near the exposed surface. The layers of increasing density within the sample had the effect of damping the resonances.

  7. Hyperaemia evaluation in clinical diathermy by four-electrode impedance measurements.

    PubMed

    Olmi, R; Bini, M; Ignesti, A; Feroldi, P; Spiazzi, L; Bodini, G

    1997-01-01

    The four-electrode electrical impedance measurement technique is proposed for the evaluation of the hyperaemia variation in tissues treated by diathermic therapy. An impedance meter suitable for such measurements is described, and an electrical model of the heated tissues, concerning the impedance variation during diathermy and its relation with hyperaemia, is presented. The occurrence of the substantial contribution of blood to the overall transverse impedance is demonstrated by comparing the experimental results with those arising from a 2D electrical/thermal model of the treated tissues. A two-admittance model is proposed to explain the electrical behaviour of the tissues treated by diathermy. The model allows us to separate the impedance violation due to the temperature dependence of tissue conductivity from that due to the change of tissue blood content. The results of preliminary measurements of tissue impedance on healthy volunteers treated by electromagnetic diathermy are presented and discussed, showing the feasibility of impedance detection of hyperaemia variations inside tissues.

  8. Acoustic Treatment Design Scaling Methods. Volume 4; Numerical Simulation of the Nonlinear Acoustic Impedance of a Perforated Plate Single-Degree-of-Freedom Resonator Using a Time-Domain Finite Difference Method

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.

    1999-01-01

    Single-degree-of-freedom resonators consisting of honeycomb cells covered by perforated facesheets are widely used as acoustic noise suppression liners in aircraft engine ducts. The acoustic resistance and mass reactance of such liners are known to vary with the intensity of the sound incident upon the panel. Since the pressure drop across a perforated liner facesheet increases quadratically with the flow velocity through the facesheet, this is known as the nonlinear resistance effect. In the past, two different empirical frequency domain models have been used to predict the Sound Pressure Level effect of the incident wave on the perforated liner impedance, one that uses the incident particle velocity in isolated narrowbands, and one that models the particle velocity as the overall velocity. In the absence of grazing flow, neither frequency domain model is entirely accurate in predicting the nonlinear effect that is measured for typical perforated sheets. The time domain model is developed in an attempt to understand and improve the model for the effect of spectral shape and amplitude of multi-frequency incident sound pressure on the liner impedance. A computer code for the time-domain finite difference model is developed and predictions using the models are compared to current frequency-domain models.

  9. Acoustic measuring techniques for suspended sediment

    NASA Astrophysics Data System (ADS)

    Gruber, P.; Felix, D.; Storti, G.; Lattuada, M.; Fleckenstein, P.; Deschwanden, F.

    2016-11-01

    Acoustic signals can be used in various ways for suspended sediment monitoring. One possibility which lends itself particularly well in the context of hydropower plants (HPPs), is to use installations for acoustic discharge measurement (ADM). Such installations already exist at waterways of many HPPs. Similar to certain turbidimeters, the attenuation of the forward scattered signal travelling through the water-sediment mixture is correlated with suspended sediment concentration (SSC). This correlation can be based on reference SSCs, e.g. from gravimetric analyses of bottle samples. Without the need of additional sensors and practically maintenance-free, this method is used successfully in the HPP Fieschertal to warn the HPP operator of high SSC to prevent excessive turbine abrasion. Acoustic methods and systems that allow for estimating both SSC and particle size distribution (PSD) are under development. The simultaneous determination of SSC and PSD is not possible using a single frequency. Therefore, multi-frequency approaches are investigated for generally scattered signals. When backscattered signals are used, a stronger frequency dependency can be exploited. However, the reliable simultaneous determination of particle size (and distribution) and concentration is still a major challenge due to a low signal-to-noise ratio and an ill- posed problem of estimating concentration and size from recorded signals. The optimal setup configuration (angles, frequencies) for such a system is not unique and further investigations are recommended.

  10. Using impedance measurements for detecting pathogens trapped in an electric field

    DOEpatents

    Miles, Robin R.

    2004-07-20

    Impedance measurements between the electrodes in an electric field is utilized to detect the presence of pathogens trapped in the electric field. Since particles trapped in a field using the dielectiphoretic force changes the impedance between the electrodes by changing the dielectric material between the electrodes, the degree of particle trapping can be determined by measuring the impedance. This measurement is used to determine if sufficient pathogen have been collected to analyze further or potentially to identify the pathogen.

  11. Use of neural networks for prediction of lateral reservoir porosity from seismic acoustic impedance: A case study from Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Alamoudi, Waleed Ahmad

    Reservoir porosity controls the strategies for reservoir management. Porosity is the primary key to a reliable reservoir model. The most economic method of evaluating reservoir porosity on a foot-by-foot basis is from core and well log data analysis. Lateral reservoir porosity is estimated using geostatistical method from well log data or from the integration of well log data and seismic data. However, the petroleum industry needs more accurate, reliable methods to estimate porosity from seismic data. Neural network analysis is one of the latest technologies available to the petroleum industry. In this study, I report results of an investigation of the use of neural network to predict lateral reservoir porosity. The approach is based on using average seismic acoustic impedances extracted from a 3D seismic volume to predict lateral average porosity for 13 reservoir geological layers. A neural network was trained using different subsets of well log data from 9 hydrocarbon wells and validated using the reminder of the wells. Data from the Unayzah reservoir in CNR field located in central basin of Saudi Arabia was used in this study. Model-based post-stack seismic inversion was used to produce a seismic acoustic impedance volume. Average impedance maps were then created for 13 layers from the Unayzah reservoir interval in the CNR field. Back-propagation neural network technique successfully estimated lateral reservoir porosity from seismic acoustic impedance and density attributes. The neural network performance using data from 6 wells (C, D, F, G, I, J), more or less distributed along the field axis, provided a better correlation and less scatter than other well training geometries in the testing phase. The A, B, and H wells were used for validation. Goodness of fit was 0.9985. The good neural network prediction in the testing phase reflects the neural network capability to estimate average reservoir porosities. Predicted lateral porosity maps incorporate

  12. In-Vivo Electrical Impedance Measurement in Mastoid Bone.

    PubMed

    Wyss Balmer, Thomas; Ansó, Juan; Muntane, Enric; Gavaghan, Kate; Weber, Stefan; Stahel, Andreas; Büchler, Philippe

    2017-04-01

    Nerve monitoring is a safety mechanism to detect the proximity between surgical instruments and important nerves during surgical bone preparation. In temporal bone, this technique is highly specific and sensitive at distances below 0.1 mm, but remains unreliable for distances above this threshold. A deeper understanding of the patient-specific bone electric properties is required to improve this range of detection. A sheep animal model has been used to characterize bone properties in vivo. Impedance measurements have been performed at low frequencies (<1 kHz) between two electrodes placed inside holes drilled into the sheep mastoid bone. An electric circuit composed of a resistor and a Fricke constant phase element was able to accurately describe the experimental measurements. Bone resistivity was shown to be linearly dependent on the inter-electrode distance and the local bone density. Based on this model, the amount of bone material between the electrodes could be predicted with an error of 0.7 mm. Our results indicate that bone could be described as an ideal resistor while the electrochemical processes at the electrode-tissue interface are characterized by a constant phase element. These results should help increasing the safety of surgical drilling procedures by better predicting the distance to critical nerve structures.

  13. A multichannel continuously selectable multifrequency electrical impedance spectroscopy measurement system.

    PubMed

    Hartov, A; Mazzarese, R A; Reiss, F R; Kerner, T E; Osterman, K S; Williams, D B; Paulsen, K D

    2000-01-01

    There is increasing evidence that alterations in the electrical property spectrum of tissues below 10 MHz is diagnostic for tissue pathology and/or pathophysiology. Yet, the complexity associated with constructing a high-fidelity multichannel, multifrequency data acquisition instrument has limited widespread development of spectroscopic electrical impedance imaging concepts. To contribute to the relatively sparse experience with multichannel spectroscopy systems this paper reports on the design, realization and evaluation of a prototype 32-channel instrument. The salient features of the system include a continuously selectable driving frequency up to 1 MHz, either voltage or current source modes of operation and simultaneous measurement of both voltage and current on each channel in either of these driving configurations. Comparisons of performance with recently reported fixed-frequency systems is favorable. Volts dc (VDC) signal-to-noise ratios of 75-80 dB are achieved and the noise floor for ac signals is near 100 dB below the signal strength of interest at 10 kHz and 60 dB down at 1 MHz. The added benefit of being able to record multispectral information on source and sense signal amplitudes and phases has also been realized. Phase-sensitive detection schemes and multiperiod undersampling techniques have been deployed to ensure measurement fidelity over the full bandwidth of system operation.

  14. Impedance Measurement for the Analysis of Corrosion Induced Failures.

    DTIC Science & Technology

    1982-02-01

    for a C-Mn Steel (C1117) in 1 M Na3PO4 , pH=4, T-21 C and in 1.0 M NaHCO3/0.1 M Na CO, T=70 C at controlled potentials with continuous recording of the...Impedance Parameters for C1117 Steel in 1 N Na3PO4 , pH = 4.............................................. 25 IV A.C. Impedance Parameters for Al 7075...CERT with continuous recording of the ac impedance.........................5 2 Anodic potentiodynamic polarization curves for 1008 steel in 1N Na3PO4

  15. Local impedance measurement of an electrode/single-pentacene-grain interface by frequency-modulation scanning impedance microscopy

    SciTech Connect

    Kimura, Tomoharu; Yamada, Hirofumi; Kobayashi, Kei

    2015-08-07

    The device performances of organic thin film transistors are often limited by the metal–organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.

  16. Acoustics measurements in normal jet impingement

    NASA Technical Reports Server (NTRS)

    Kleis, S. J.

    1977-01-01

    The dependence of far field acoustic measurements for a uniform jet on nozzle to plate spacing for small dimensionless spacings (h/d - 0.75 to 3.0) was investigated. Spectra from a real time analyzer were read and processed by an HP 2116 minicomputer in on-line mode. Similar data was generated for a fully developed pipe flow exit condition jet to compare with other investigations. The data base for normal jet impingement was extended to smaller values of nozzle to plate spacing. The effects of slight noise heating (30 deg rise) of the jet on the far field noise produced by the impinging jet are demonstrated.

  17. Precision of Four Acoustic Bone Measurement Devices

    NASA Technical Reports Server (NTRS)

    Miller, Christopher; Rianon, Nahid; Feiveson, Alan; Shackelford, Linda; LeBlanc, Adrian

    2000-01-01

    Though many studies have quantified the precision of various acoustic bone measurement devices, it is difficult to directly compare the results among the studies, because they used disparate subject pools, did not specify the estimation methodology, or did not use consistent definitions for various precision characteristics. In this study, we used a repeated measures design protocol to directly determine the precision characteristics of four acoustic bone measurement devices: the Mechanical Response Tissue Analyzer (MRTA), the UBA-575+, the SoundScan 2000 (S2000), and the Sahara Ultrasound Bone Analyzer. Ten men and ten women were scanned on all four devices by two different operators at five discrete time points: Week 1, Week 2, Week 3, Month 3 and Month 6. The percent coefficient of variation (%CV) and standardized coefficient of variation were computed for the following precision characteristics: interoperator effect, operator-subject interaction, short-term error variance, and long-term drift. The MRTA had high interoperator errors for its ulnar and tibial stiffness measures and a large long-term drift in its tibial stiffness measurement. The UBA-575+ exhibited large short-term error variances and long-term drift for all three of its measurements. The S2000's tibial speed of sound measurement showed a high short-term error variance and a significant operator-subject interaction but very good values (less than 1%) for the other precision characteristics. The Sahara seemed to have the best overall performance, but was hampered by a large %CV for short-term error variance in its broadband ultrasound attenuation measure.

  18. Precision of Four Acoustic Bone Measurement Devices

    NASA Technical Reports Server (NTRS)

    Miller, Christopher; Feiveson, Alan H.; Shackelford, Linda; Rianon, Nahida; LeBlanc, Adrian

    2000-01-01

    Though many studies have quantified the precision of various acoustic bone measurement devices, it is difficult to directly compare the results among the studies, because they used disparate subject pools, did not specify the estimation methodology, or did not use consistent definitions for various precision characteristics. In this study, we used a repeated measures design protocol to directly determine the precision characteristics of four acoustic bone measurement devices: the Mechanical Response Tissue Analyzer (MRTA), the UBA-575+, the SoundScan 2000 (S2000), and the Sahara Ultrasound Done Analyzer. Ten men and ten women were scanned on all four devices by two different operators at five discrete time points: Week 1, Week 2, Week 3, Month 3 and Month 6. The percent coefficient of variation (%CV) and standardized coefficient of variation were computed for the following precision characteristics: interoperator effect, operator-subject interaction, short-term error variance, and long-term drift, The MRTA had high interoperator errors for its ulnar and tibial stiffness measures and a large long-term drift in its tibial stiffness measurement. The UBA-575+ exhibited large short-term error variances and long-term drift for all three of its measurements. The S2000's tibial speed of sound measurement showed a high short-term error variance and a significant operator-subject interaction but very good values ( < 1%) for the other precision characteristics. The Sahara seemed to have the best overall performance, but was hampered by a large %CV for short-term error variance in its broadband ultrasound attenuation measure.

  19. Lorentz force electrical impedance tomography using magnetic field measurements.

    PubMed

    Zengin, Reyhan; Gençer, Nevzat Güneri

    2016-08-21

    In this study, magnetic field measurement technique is investigated to image the electrical conductivity properties of biological tissues using Lorentz forces. This technique is based on electrical current induction using ultrasound together with an applied static magnetic field. The magnetic field intensity generated due to induced currents is measured using two coil configurations, namely, a rectangular loop coil and a novel xy coil pair. A time-varying voltage is picked-up and recorded while the acoustic wave propagates along its path. The forward problem of this imaging modality is defined as calculation of the pick-up voltages due to a given acoustic excitation and known body properties. Firstly, the feasibility of the proposed technique is investigated analytically. The basic field equations governing the behaviour of time-varying electromagnetic fields are presented. Secondly, the general formulation of the partial differential equations for the scalar and magnetic vector potentials are derived. To investigate the feasibility of this technique, numerical studies are conducted using a finite element method based software. To sense the pick-up voltages a novel coil configuration (xy coil pairs) is proposed. Two-dimensional numerical geometry with a 16-element linear phased array (LPA) ultrasonic transducer (1 MHz) and a conductive body (breast fat) with five tumorous tissues is modeled. The static magnetic field is assumed to be 4 Tesla. To understand the performance of the imaging system, the sensitivity matrix is analyzed. The sensitivity matrix is obtained for two different locations of LPA transducer with eleven steering angles from [Formula: see text] to [Formula: see text] at intervals of [Formula: see text]. The characteristics of the imaging system are shown with the singular value decomposition (SVD) of the sensitivity matrix. The images are reconstructed with the truncated SVD algorithm. The signal-to-noise ratio in measurements is assumed 80 d

  20. Lorentz force electrical impedance tomography using magnetic field measurements

    NASA Astrophysics Data System (ADS)

    Zengin, Reyhan; Güneri Gençer, Nevzat

    2016-08-01

    In this study, magnetic field measurement technique is investigated to image the electrical conductivity properties of biological tissues using Lorentz forces. This technique is based on electrical current induction using ultrasound together with an applied static magnetic field. The magnetic field intensity generated due to induced currents is measured using two coil configurations, namely, a rectangular loop coil and a novel xy coil pair. A time-varying voltage is picked-up and recorded while the acoustic wave propagates along its path. The forward problem of this imaging modality is defined as calculation of the pick-up voltages due to a given acoustic excitation and known body properties. Firstly, the feasibility of the proposed technique is investigated analytically. The basic field equations governing the behaviour of time-varying electromagnetic fields are presented. Secondly, the general formulation of the partial differential equations for the scalar and magnetic vector potentials are derived. To investigate the feasibility of this technique, numerical studies are conducted using a finite element method based software. To sense the pick-up voltages a novel coil configuration (xy coil pairs) is proposed. Two-dimensional numerical geometry with a 16-element linear phased array (LPA) ultrasonic transducer (1 MHz) and a conductive body (breast fat) with five tumorous tissues is modeled. The static magnetic field is assumed to be 4 Tesla. To understand the performance of the imaging system, the sensitivity matrix is analyzed. The sensitivity matrix is obtained for two different locations of LPA transducer with eleven steering angles from -{{25}\\circ} to {{25}\\circ} at intervals of {{5}\\circ} . The characteristics of the imaging system are shown with the singular value decomposition (SVD) of the sensitivity matrix. The images are reconstructed with the truncated SVD algorithm. The signal-to-noise ratio in measurements is assumed 80 dB. Simulation studies

  1. Flight Acoustics Measurement Techniques and Applications

    NASA Technical Reports Server (NTRS)

    Preisser, J. S.; Marcolini, M. A.

    1998-01-01

    Careful consideration must be given to data acquisition and analysis techniques in the design of experiments for the measurement of noise generated by flight vehicles. Although noise measurement locations and data reduction procedures are specified for aircraft certification by FAA and ICAO directives, for example, there are virtually no established procedures for aircraft noise measurement for other purposes. To optimize the quality and quantity of information obtained in a flight acoustics experiment, microphone layout, data acquisition, and analysis must be tailored to the specific test objective. This paper will review flight acoustics technology at NASA Langley Research Center developed over the past decade. In particular, the paper will focus on flight experiments performed for three diverse objectives: (1) research applications, such as noise prediction code validation, (2) noise impact modeling, and (3) noise abatement flight procedures. To best achieve these diverse objectives, different deployments of microphone systems on the ground are required, and different data analysis techniques are needed. In all cases, accurate positioning of the aircraft synchronized in time with the data recording is necessary. However, there are some restrictions on flight operations unique to each case for the methods to properly work.

  2. Theory and cardiac applications of electrical impedance measurements.

    PubMed

    Penney, B C

    1986-01-01

    The methodology of the two-electrode, four-electrode, and guard-ring techniques is presented following a brief history of impedance plethysmography. The theoretical basis for predicting the sampling fields for conductivity and volume changes is presented. Theoretical and experimental studies of the sampling field associated with various electrode arrays are reviewed. With this background, the use of impedance plethysmography for cardiac monitoring and diagnosis is reviewed. The basic methodology is presented and models used to interpret the signal are reviewed. Theoretical and experimental studies of what is sampled are summarized. The accuracy of impedance stroke volume estimates is evaluated by surveying the results of human studies and examining critical animal studies. The usefulness of impedance cardiography for ventricular performance evaluation is also reviewed. Additional uses for cardiopulmonary diagnosis are briefly presented.

  3. Acoustic systems for the measurement of streamflow

    USGS Publications Warehouse

    Laenen, Antonius; Smith, Winchell

    1982-01-01

    Very little information is available concerning acoustic velocity meter (AVM) operation, performance, and limitations. This report provides a better understanding about the application of AVM instrumentation to streamflow measurment. Operational U.S. Geological Survey systems have proven that AVM equipment is accurate and dependable. AVM equipment has no practical upper limit of measureable velocity if sonic transducers are securely placed and adequately protected, and will measure velocitites as low as 0.1 meter per second which is normally less than the threshold level for mechanical or head-loss meters. In some situations the performance of AVM equipment may be degraded by multipath interference, signal bending, signal attenuation, and variable streamline orientation. Smaller, less-expensive, more conveniently operable microprocessor equipment is now available which should increase use of AVM systems in streamflow applications. (USGS)

  4. Acoustic absorption measurement of human hair and skin within the audible frequency range.

    PubMed

    Katz, B F

    2000-11-01

    Utilizing the two-microphone impedance tube method, the acoustic absorption of human skin and hair is measured in the frequency range 1-6 kHz. Various locations on a number of human subjects are measured to determine if the presence of bone or an air pocket affects the acoustic absorption of human skin. The absorption coefficient of human hair is also measured. Additional techniques are utilized to minimize errors due to sample mounting methods. Techniques are employed to minimize potential errors in sensor and sample locations. The results of these measurements are compared to relevant historical papers on similar investigations. Results for skin measurements compare well with previous work. Measured hair absorption data do not agree with previous work in the area but do coincide with expected trends, which previous works do not.

  5. Measuring impedance in congestive heart failure: Current options and clinical applications

    PubMed Central

    Tang, W. H. Wilson; Tong, Wilson

    2011-01-01

    Measurement of impedance is becoming increasingly available in the clinical setting as a tool for assessing hemodynamics and volume status in patients with heart failure. The 2 major categories of impedance assessment are the band electrode method and the implanted device lead method. The exact sources of the impedance signal are complex and can be influenced by physiologic effects such as blood volume, fluid, and positioning. This article provides a critical review of our current understanding and promises of impedance measurements, the techniques that have evolved, as well as the evidence and limitations regarding their clinical applications in the setting of heart failure management. PMID:19249408

  6. Identification of fluids and an interface between fluids by measuring complex impedance

    DOEpatents

    Lee, David O.; Wayland, Jr., James R.

    1989-01-01

    Complex impedance measured over a predefined frequency range is used to determine the identity of different oils in a column. The location of an interface between the oils is determined from the percent frequency effects of the complex impedance measured across the interface.

  7. Identification of fluids and an interface between fluids by measuring complex impedance

    DOEpatents

    Lee, D.O.; Wayland, J.R. Jr.

    1989-12-05

    Complex impedance measured over a predefined frequency range is used to determine the identity of different oils in a column. The location of an interface between the oils is determined from the percent frequency effects of the complex impedance measured across the interface. 5 figs.

  8. Acoustic Measurements of Rectangular Nozzles With Bevel

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2012-01-01

    A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet.

  9. Acoustic Measurements of Rectangular Nozzles with Bevel

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2012-01-01

    A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet.

  10. Resin characterization by electro-acoustic measurements.

    PubMed

    Müller, Egbert; Mann, Christian

    2007-03-09

    The electro-acoustic effects, namely the ion vibration potential (IVP) and the colloidal vibration current (CVI), colloidal vibration potential (CVP) first described by P. Debye [P. Debye, J. Chem. Phys. 1 (1933) 13], are a result of charge separation of bound or free ions at different degrees by ultrasonic waves. Today commercial instruments are available to investigate liquid homogeneous and heterogeneous systems. In the present paper the application of this technique for the characterization of salts, protein solutions and resins for biochromatography is shown and valuable information about resins can be derived in a short time. Various resins were investigated with the following results: (1) the CVI magnitude is dependent of several parameters (such as particle size distribution, volume fraction, density difference); (2) the CVI is influenced by the surface modification of the resins. Polymeric modifications decrease the value of CVI. The CVI is generally lower for high capacity resins; (3) the measurement of the electro-acoustic effects can be used to detect small changes in resins. The CVI is dependent of the amount of adsorbed protein in "native" and denatured state.

  11. Evaluation for Electrochemical Impedance Measurement of Carbon Nanotube Taste Sensor

    NASA Astrophysics Data System (ADS)

    Takeda, Naoki; Hirata, Takamichi; Akiya, Masahiro

    In our laboratory, a nano-bio taste sensor based on carbon nanotubes has been developed. However, previous technique cannot separate elements such as CNT random network or electrode surface etc., because of sensor impedance change in fixed frequency. Electrochemical impedance spectroscopy (EIS) revealed CNT taste sensor with two R/C parallel circuits. Experimental complex plane plots were reproduced using a computer simulation program based upon the lumped equivalent circuit approach. It was found that the sensor has two relaxation times, and also that these circuits consist of two elements such as electrode surface and CNT random network.

  12. Measurement of acoustical characteristics of mosques in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Abdou, Adel A.

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  13. Measurement of acoustical characteristics of mosques in Saudi Arabia.

    PubMed

    Abdou, Adel A

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  14. Measuring aeolian sand transport using acoustic sensors

    NASA Astrophysics Data System (ADS)

    Poortinga, Ate; van Rheenen, Hans; Ellis, Jean T.; Sherman, Douglas J.

    2015-03-01

    Acoustic sensors are frequently used to measure aeolian saltation. Different approaches are used to process the signals from these instruments. The goal of this paper is to describe and discuss a method to measure aeolian saltation with acoustic sensors. In a laboratory experiment, we measured the output from an advanced signal processing scheme on the circuit board of the saltiphone. We use a software implementation of this processing scheme to re-analyse data from four miniphones obtained during a field experiment. It is shown that a set of filters remove background noise outside the frequency spectrum of aeolian saltation (at 8 kHz), whereas signals within this frequency spectrum are amplified. The resulting analogue signal is a proxy of the energy. Using an AC pulse convertor, this signal can be converted into a digital and analogue count signal or an analogue energy signal, using a rectifier and integrator. Spatio-temporal correlation between field deployed miniphones increases by using longer integration times for signal processing. To quantify aeolian grain impact, it is suggested to use the analogue energy output, as this mode is able to detect changes in frequency and amplitude. The analogue and digital count signals are able to detect an increase in frequency, but are not able to detect an increase in signal amplitude. We propose a two-stage calibration scheme consisting of (1) a factory calibration, to set the frequency spectrum of the sensor and (2) a standardized drop-test conducted before and after the experiment to evaluate the response of the sensor.

  15. Measuring Acoustic Nonlinearity by Collinear Mixing Waves

    NASA Astrophysics Data System (ADS)

    Liu, M.; Tang, G.; Jacobs, L. J.; Qu, J.

    2011-06-01

    It is well known that the acoustic nonlinearity parameter β is correlated to fatigue damage in metallic materials. Various methods have been developed to measure β. One of the most often used methods is the harmonic generation technique, in which β is obtained by measuring the magnitude of the second order harmonic waves. An inherent weakness of this method is the difficulty in distinguishing material nonlinearity from the nonlinearity of the measurement system. In this paper, we demonstrate the possibility of using collinear mixing waves to measure β. The wave mixing method is based on the interaction between two incident waves in a nonlinear medium. Under certain conditions, such interactions generate a third wave of different frequency. This generated third wave is also called resonant wave, because its amplitude is unbounded if the medium has no attenuation. Such resonant waves are less sensitive to the nonlinearity of the measurement system, and have the potential to identify the source location of the nonlinearity. In this work, we used a longitudinal wave and a shear wave as the incident waves. The resonant shear wave is measured experimentally on samples made of aluminum and steel, respectively. Numerical simulations of the tests were also performed using a finite difference method.

  16. Focused impedance measurement (FIM). A new technique with improved zone localization.

    PubMed

    Rabbani, K S; Sarker, M; Akond, M H; Akter, T

    1999-04-20

    Conventional four-electrode impedance measurements (FEIM) cannot localize a zone of interest in a volume conductor. On the other hand, the recently developed electrical impedance tomography (EIT) system offers an image with reasonable resolution, but is complex and needs many electrodes. By placing two FEIM systems perpendicular to each other over a common zone at the center and combining the two results, it is possible to obtain enhanced sensitivity over this central zone. This is the basis of the proposed new method of focused impedance measurement (FIM). Sensitivity maps in both 2D and 3D show the desired improvement. A comparison of stomach-emptying studies also indicates the improvement achieved. This new method may be useful for impedance measurements of large organs like stomach, heart, and lungs. Being much simpler in comparison to EIT, multifrequency systems can be simply built for FIM. Besides, FIM may have utility in other fields like geology where impedance measurements are performed.

  17. Ares I Scale Model Acoustic Tests Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas D.

    2011-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) was a development test performed at the Marshall Space Flight Center (MSFC) East Test Area (ETA) Test Stand 116. The test article included a 5% scale Ares I vehicle model and tower mounted on the Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments located throughout the test article. There were four primary ASMAT instrument suites: ignition overpressure (IOP), lift-off acoustics (LOA), ground acoustics (GA), and spatial correlation (SC). Each instrumentation suite incorporated different sensor models which were selected based upon measurement requirements. These requirements included the type of measurement, exposure to the environment, instrumentation check-outs and data acquisition. The sensors were attached to the test article using different mounts and brackets dependent upon the location of the sensor. This presentation addresses the observed effect of the sensors and mounts on the acoustic and pressure measurements.

  18. Extreme low frequency acoustic measurement system

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2013-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  19. Extreme Low Frequency Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2017-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  20. Electron density dependence of impedance probe plasma potential measurements

    SciTech Connect

    Walker, D. N.; Blackwell, D. D.; Amatucci, W. E.

    2015-08-15

    In earlier works, we used spheres of various sizes as impedance probes in demonstrating a method of determining plasma potential, φ{sub p}, when the probe radius is much larger than the Debye length, λ{sub D}. The basis of the method in those works [Walker et al., Phys. Plasmas 13, 032108 (2006); ibid. 15, 123506 (2008); ibid. 17, 113503 (2010)] relies on applying a small amplitude signal of fixed frequency to a probe in a plasma and, through network analyzer-based measurements, determining the complex reflection coefficient, Γ, for varying probe bias, V{sub b}. The frequency range of the applied signal is restricted to avoid sheath resonant effects and ion contributions such that ω{sub pi} ≪ ω ≪ ω{sub pe}, where ω{sub pi} is the ion plasma frequency and ω{sub pe} is the electron plasma frequency. For a given frequency and applied bias, both Re(Z{sub ac}) and Im(Z{sub ac}) are available from Γ. When Re(Z{sub ac}) is plotted versus V{sub b}, a minimum predicted by theory occurs at φ{sub p} [Walker et al., Phys. Plasmas 17, 113503 (2010)]. In addition, Im(Z{sub ac}) appears at, or very near, a maximum at φ{sub p}. As n{sub e} decreases and the sheath expands, the minimum becomes harder to discern. The purpose of this work is to demonstrate that when using network analyzer-based measurements, Γ itself and Im(Z{sub ac}) and their derivatives are useful as accompanying indicators to Re(Z{sub ac}) in these difficult cases. We note the difficulties encountered by the most commonly used plasma diagnostic, the Langmuir probe. Spherical probe data is mainly used in this work, although we present limited data for a cylinder and a disk. To demonstrate the effect of lowered density as a function of probe geometry, we compare the cylinder and disk using only the indicator Re(Z{sub ac})

  1. Outdoor Synthetic Aperture Acoustic Ground Target Measurements

    DTIC Science & Technology

    2010-04-19

    1341 (2003). [11] C. A. Dimarzio, T. Shi, F. J. Blonigen et al., “ Laser -Induced Acoustic Landmine Detection,” The Journal Of The Acoustical Society...High Frequency A/S Coupling For Ap Buried Landmine Detection Using Laser Doppler Vibrometers,” Proc. SPIE 5415(1), 35-41 (2004). [16] Bishop, S... Dolphin Echolocation Clicks For Target Discrimination,” The Journal Of The Acoustical Society Of America 124(1), 657-666 (2008). [20] Y. Nakamura

  2. Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase angle measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Impedance (Z), and phase angle (') of a cylindrical parallel-plate capacitor with dry fruits between the plates was measured using a CI meter (Chari’s Impedance meter), at 1 and 9 MHz . Capacitance, C was derived from Z and ', and using the C, ', and Z values of a set of cherries whose moisture con...

  3. Hybrid system for magnetic and acoustic measurement.

    PubMed

    Bruno, A C; Baffa, O; Carneiro, A O

    2009-01-01

    In order to improve the spatial resolution of Biosusceptometry of Alternate Current (BAC), we are suggesting the coupling of a Doppler ultrasonic transducer with the BAC system. The Doppler transducer obtains information from the vibration of ferromagnetic particles immersed in a visco-elastic medium when it is excited by an alternating magnetic field. In this case, the same magnetic particles used as contrast for susceptometric measurement also will work as contrast for the Doppler measurement. In this work, we present the characterization of the hybrid system for susceptometric and acoustic measurements simultaneously. It was observed that the susceptometric and Doppler ultrasound signal have the same profile and maximum amplitude for frequency of magnetizing field about 200 Hz. When using ferrite particles as magnetic contrast mixed with yogurt as based material, the susceptometric and Doppler measurement have sensitivity for concentration of particles as low as 1%. The sensitivity of the Doppler is dependent of the gradient of magnetic field over the sample. In this work, the magnetic field 5 cm far from the face of the transducer was 70 microT/volts.

  4. Thick Films acoustic sensors devoted to MTR environment measurements. Thick Films acoustic sensors devoted to Material Testing Reactor environment measurements

    SciTech Connect

    Very, F.; Rosenkrantz, E.; Combette, P.; Ferrandis, J.Y.; Fourmentel, D.; Destouches, C.; Villard, J.F.

    2015-07-01

    The development of advanced instrumentation for in-pile experiments in Material Testing Reactor constitutes a main goal for the improvement of the nuclear fuel behavior knowledge. An acoustic method for fission gas release detection was tested with success during a first experiment called REMORA 3 in 2010 and 2011, and the results were used to differentiate helium and fission gas release kinetics under transient operating conditions. This experiment was lead at OSIRIS reactor (CEA Saclay, France). The maximal temperature on the sensor during the irradiation was about 150 deg. C. In this paper we present a thick film transducer produce by screen printing process. The screen printing of piezoelectric offers a wide range of possible applications for the development of acoustic sensors and piezoelectric structure for measurements in high temperature environment. We firstly produced a Lead Zirconate Titanate (PZT) based paste composed of Pz27 powder from Ferroperm, CF7575 glass, and organic solvent ESL 400. Likewise a Bismuth Titanate based paste synthesized in our laboratory was produced. With these inks we produced thick film up to 130 μm by screen printing process. Material properties characterizations of these thick-film resonators are essential for device design and applications. The piezoelectric coefficients d33 and pyro-electric P(T) coefficient are investigated. The highest P(T) and d33 are respectively 80 μC.m{sup -2}.K{sup -1} and 130 μC.N{sup -1} for the PZT transducer -which validates the fabrication process-. In view of the development of this transducer oriented for high temperature and irradiation environment, we investigated the electrical properties of the transducers for different ranges of frequencies and temperature - from 20 Hz up to 40 MHz between 30 and 400 deg. C. We highlight the evolution of the impedance response and piezoelectric parameters of screen printed piezoelectric structures on alumina. Shortly an irradiation will be realized in

  5. A model for the acoustic impedance of a perforated plate liner with multiple frequency excitation

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1971-01-01

    A nonlinear resistance model is used in the one-dimensional equations of motion with an arbitrary exciting pressure function. The effects of high amplitude fluid motion, grazing flow, and spectral excitation can be studied together. Sample calculations of acoustic resistances are presented using a high amplitude discrete tone superimposed upon a simulated white noise spectrum. The tone amplitude is varied and its effect is shown both with and without a grazing flow velocity.

  6. Acoustic systems for the measurement of streamflow

    USGS Publications Warehouse

    Laenen, Antonius; Smith, Winchell

    1983-01-01

    The acoustic velocity meter (AVM), also referred to as an ultrasonic flowmeter, has been an operational tool for the measurement of streamflow since 1965. Very little information is available concerning AVM operation, performance, and limitations. The purpose of this report is to consolidate information in such a manner as to provide a better understanding about the application of this instrumentation to streamflow measurement. AVM instrumentation is highly accurate and nonmechanical. Most commercial AVM systems that measure streamflow use the time-of-travel method to determine a velocity between two points. The systems operate on the principle that point-to-point upstream travel-time of sound is longer than the downstream travel-time, and this difference can be monitored and measured accurately by electronics. AVM equipment has no practical upper limit of measurable velocity if sonic transducers are securely placed and adequately protected. AVM systems used in streamflow measurement generally operate with a resolution of ?0.01 meter per second but this is dependent on system frequency, path length, and signal attenuation. In some applications the performance of AVM equipment may be degraded by multipath interference, signal bending, signal attenuation, and variable streamline orientation. Presently used minicomputer systems, although expensive to purchase and maintain, perform well. Increased use of AVM systems probably will be realized as smaller, less expensive, and more conveniently operable microprocessor-based systems become readily available. Available AVM equipment should be capable of flow measurement in a wide variety of situations heretofore untried. New signal-detection techniques and communication linkages can provide additional flexibility to the systems so that operation is possible in more river and estuary situations.

  7. Local transverse coupling impedance measurements in a synchrotron light source from turn-by-turn acquisitions

    NASA Astrophysics Data System (ADS)

    Carlà, Michele; Benedetti, Gabriele; Günzel, Thomas; Iriso, Ubaldo; Martí, Zeus

    2016-12-01

    Transverse beam coupling impedance is a source of beam instabilities that limits the machine performance in circular accelerators. Several beam based techniques have been used to measure the transverse impedance of an accelerator, usually based on the optics distortion produced by the impedance source itself. Beam position monitor turn-by-turn analysis for impedance characterization has been usually employed in large circumference machines, while synchrotron light sources have mainly used slow orbit based techniques. Instead, the work presented in this paper uses for the first time turn-by-turn data at ALBA to advance the measurement technique into the range of the typically small impedance values of modern light sources. We have measured local impedance contributions through the observation of phase advance versus bunch charge using the betatron oscillations excited with a fast dipole kicker. The ALBA beam position monitor system and the precision of the turn-by-turn analysis allowed to characterize the main sources of transverse impedance, in good agreement with the model values, including the impedance of an in-vacuum undulator.

  8. Anisotropy of human muscle via non invasive impedance measurements. Frequency dependence of the impedance changes during isometric contractions

    NASA Astrophysics Data System (ADS)

    Kashuri, Hektor

    In this thesis we present non invasive muscle impedance measurements using rotatable probes extending the work done by Aaron et al. (1997) by measuring not only the real part of the impedance but the imaginary part as well. The results reveal orientations of underlying muscle fibers via minima in resistance and reactance versus angle curves, suggesting this method as potentially useful for studying muscle properties in clinical and physiological research. Calculations of the current distribution for a slab of material with anisotropic conductivity show that the current distribution depends strongly on the separation of two current electrodes and as well as on its conducting anisotropy. Forearm muscle impedance measurements at 50 kHz done by Shiffman et al. (2003) had shown that both resistance (R) and reactance (X) increase during isometric contraction. We have extended these measurements in the 3 to 100 kHz range and we found that resistance (R) and reactance (X) both increase and their changes increased or decreased at frequency dependent rates. Analysis based on circuit models of changes in R and X during the short contraction pulses showed that the extra cellular fluid resistance increased by 3.9 +/- 1.4 %, while the capacitance increased by 5.6 +/- 2 %. For long contraction pulses at very low frequencies: (1) there was practically no change in R during contraction, which implies that these changes are due to cellular membrane or intracellular effects with the extra cellular water component not participating, and (2) in post contraction stage there were no morphological changes which means that drifts in R can only be due to physiological changes. Following Shiffman et al. (2003) we measured impedance changes of R and X during a triangular shaped pulse of force generated via isometric forearm muscle contraction at 50 kHz. We measured these changes in 3-100 kHz frequency range for a stair case pulse of forces and the results showed that they are frequency

  9. Insulator-based DEP with impedance measurements for analyte detection

    DOEpatents

    Davalos, Rafael V.; Simmons, Blake A.; Crocker, Robert W.; Cummings, Eric B.

    2010-03-16

    Disclosed herein are microfluidic devices for assaying at least one analyte specie in a sample comprising at least one analyte concentration area in a microchannel having insulating structures on or in at least one wall of the microchannel which provide a nonuniform electric field in the presence of an electric field provided by off-chip electrodes; and a pair of passivated sensing electrodes for impedance detection in a detection area. Also disclosed are assay methods and methods of making.

  10. Method and means for measuring acoustic emissions

    DOEpatents

    Renken, Jr., Claus J.

    1976-01-06

    The detection of acoustic emissions emanating from an object is achieved with a capacitive transducer coupled to the object. The capacitive transducer is charged and then allowed to discharge with the rate of discharge being monitored. Oscillations in the rate of discharge about the normally exponential discharge curve for the capacitive transducer indicate the presence of acoustic emissions.

  11. In situ measurement of tissue impedance using an inductive coupling interface circuit.

    PubMed

    Chiu, Hung-Wei; Chuang, Jia-min; Lu, Chien-Chi; Lin, Wei-Tso; Lin, Chii-Wann; Lin, Mu-Lien

    2013-06-01

    In this work, a method of an inductive coupling impedance measurement (ICIM) is proposed for measuring the nerve impedance of a dorsal root ganglion (DRG) under PRF stimulation. ICIM provides a contactless interface for measuring the reflected impedance by an impedance analyzer with a low excitation voltage of 7 mV. The paper develops a calibration procedure involving a 50-Ω reference resistor to calibrate the reflected resistance for measuring resistance of the nerve in the test. A de-embedding technique to build the equivalent transformer circuit model for the ICIM circuit is also presented. A batteryless PRF stimulator with ICIM circuit demonstrated good accuracy for the acute measurement of DRG impedance both in situ and in vivo. Besides, an in vivo animal experiment was conducted to show that the effectiveness of pulsed radiofrequency (PRF) stimulation in relieving pain gradually declined as the impedance of the stimulated nerve increased. The experiment also revealed that the excitation voltage for measuring impedance below 25 mV can prevent the excitation of a nonlinear response of DRG.

  12. Skin-electrode impedance measurement during ECG acquisition: method’s validation

    NASA Astrophysics Data System (ADS)

    Casal, Leonardo; La Mura, Guillermo

    2016-04-01

    Skm-electrode impedance measurement can provide valuable information prior. dunng and post electrocardiographic (ECG) or electroencephalographs (EEG) acquisitions. In this work we validate a method for skm-electrode impedance measurement using test circuits with known resistance and capacitor values, at different frequencies for injected excitation current. Finally the method is successfully used for impedance measurement during ECG acquisition on a subject usmg 125 Hz and 6 nA square wave excitation signal at instrumentation amplifier mput. The method can be used for many electrodes configuration.

  13. Coupling impedance of an in-vacuum undulator: Measurement, simulation, and analytical estimation

    NASA Astrophysics Data System (ADS)

    Smaluk, Victor; Fielder, Richard; Blednykh, Alexei; Rehm, Guenther; Bartolini, Riccardo

    2014-07-01

    One of the important issues of the in-vacuum undulator design is the coupling impedance of the vacuum chamber, which includes tapered transitions with variable gap size. To get complete and reliable information on the impedance, analytical estimate, numerical simulations and beam-based measurements have been performed at Diamond Light Source, a forthcoming upgrade of which includes introducing additional insertion device (ID) straights. The impedance of an already existing ID vessel geometrically similar to the new one has been measured using the orbit bump method. The measurement results in comparison with analytical estimations and numerical simulations are discussed in this paper.

  14. Coupling impedance of an in-vacuum undulator. Measurement, simulation, and analytical estimation

    SciTech Connect

    Simaluk, Victor; Blednykh, Alexei; Fielder, Richard; Rehm, Guenther; Bartolini, Riccardo

    2014-07-25

    One of the important issues of the in-vacuum undulator design is the coupling impedance of the vacuum chamber, which includes tapered transitions with variable gap size. In order to get complete and reliable information on the impedance, analytical estimate, numerical simulations and beam-based measurements have been performed at Diamond Light Source, a forthcoming upgrade of which includes introducing additional insertion device (ID) straights. Moreover, the impedance of an already existing ID vessel geometrically similar to the new one has been measured using the orbit bump method. The measurement results in comparison with analytical estimations and numerical simulations are discussed in this paper.

  15. A Spherically-Shaped PZT Thin Film Ultrasonic Transducer with an Acoustic Impedance Gradient Matching Layer Based on a Micromachined Periodically Structured Flexible Substrate

    PubMed Central

    Feng, Guo-Hua; Liu, Wei-Fan

    2013-01-01

    This paper presents the microfabrication of an acoustic impedance gradient matching layer on a spherically-shaped piezoelectric ultrasonic transducer. The acoustic matching layer can be designed to achieve higher acoustic energy transmission and operating bandwidth. Also included in this paper are a theoretical analysis of the device design and a micromachining technique to produce the novel transducer. Based on a design of a lead titanium zirconium (PZT) micropillar array, the constructed gradient acoustic matching layer has much better acoustic transmission efficiency within a 20–50 MHz operation range compared to a matching layer with a conventional quarter-wavelength thickness Parylene deposition. To construct the transducer, periodic microcavities are built on a flexible copper sheet, and then the sheet forms a designed curvature with a ball shaping. After PZT slurry deposition, the constructed PZT micropillar array is released onto a curved thin PZT layer. Following Parylene conformal coating on the processed PZT micropillars, the PZT micropillars and the surrounding Parylene comprise a matching layer with gradient acoustic impedance. By using the proposed technique, the fabricated transducer achieves a center frequency of 26 MHz and a −6 dB bandwidth of approximately 65%. PMID:24113683

  16. Field Measurement of the Acoustic Nonlinearity Parameter in Turbine Blades

    NASA Technical Reports Server (NTRS)

    Hinton, Yolanda L.; Na, Jeong K.; Yost, William T.; Kessel, Gregory L.

    2000-01-01

    Nonlinear acoustics techniques were used to measure fatigue in turbine blades in a power generation plant. The measurements were made in the field using a reference based measurement technique, and a reference sample previously measured in the laboratory. The acoustic nonlinearity parameter showed significant increase with fatigue in the blades, as indicated by service age and areas of increased stress. The technique shows promise for effectively measuring fatigue in field applications and predicting subsequent failures.

  17. Measurement of Single-Cell Deformability Using Impedance Analysis on Microfluidic Chip

    NASA Astrophysics Data System (ADS)

    Kim, Dongil; Choi, Eunpyo; Choi, Sung Sik; Lee, Sangho; Park, Jungyul; Yun, Kwang-Seok

    2010-12-01

    In this paper, we propose a microfluidic chip that measures the deformability of single cells by an impedance measurement method. The proposed chip is designed to differentiate the deformability of various cells by measuring the length of their stretched membrane indirectly according to the variation of the impedance after applying aspiration pressure to the cell membrane. The length of the stretched cell membrane is proportional to the applied pressure. Lengths of 18 and 21 µm were observed at the same suction pressure for human breast normal cells (MCF-10A) and caner cells (MCF-7), respectively. Electrical measurement was performed using an impedance analyzer at various frequencies. Results revealed that the impedance measurement method can be used to analyze the biomechanical characteristics of single cells, which indicates the state of malignancy of cells.

  18. In vivo impedance measurements on nerves and surrounding skeletal muscles in rats and human body.

    PubMed

    Prokhorov, E; Llamas, F; Morales-Sánchez, E; González-Hernández, J; Prokhorov, A

    2002-05-01

    The aim of the work was to use impedance measurements to find the location of nerves under the human skin. In vivo impedance measurements were performed on exposed nervous and muscular tissues of rats. Similarly, the impedance measurements were also performed on the skin of six men, over the median nerve at the wrist, as well as 4-5 mm away from this location. Results obtained with rats have shown that the relative permittivity and conductivity of nerves are larger (by almost two orders of magnitude) than those observed for the muscular tissues surrounding the nerve. The results obtained on human skin in the frequency range of 20-200 kHz, when the electrodes were placed over the nerve, show lower resistance and higher capacitance than in the other areas measured. These preliminary results indicate that it may be possible to use impedance measurements to find the location of exposed nerves and also nerves under the skin.

  19. Comparison of impedance measurements near the skin of newborns and adults.

    PubMed

    Amm, Bruce; Kao, Tzu-Jen; Newell, Jonathan; Isaacson, David; Saulnier, Gary; Shoudy, David; Boverman, Greg; Sahni, Rakesh; Weindler, Marilyn; Chong, David; DiBardino, David; Davenport, David; Ashe, Jeffrey

    2016-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technology that has been extensively studied for monitoring lung function of neonatal and adult subjects, especially in neonatal intensive care unit (NICU) and intensive care unit (ICU) environments. The sources of the total impedance in these applications include internal organs, near-boundary tissues, electrode-skin impedance, electrodes and conducting wires. This total impedance must be considered for system design and setting voltage gain since it will contribute to the measured voltage. To adapt a single instrument for use on infants and adults, we studied the difference between the impedance near the skin in both classes of patients. We used a simultaneous multi-source EIT (SMS-EIT) system to make impedance measurements. Characteristic resistance was calculated for two different current patterns: one that is more sensitive to boundary region impedance and another that is more sensitive to interior changes. We present ratios of these resistances to assess the relative contribution of near-skin effects to the overall impedance. Twenty adult ICU subjects (10 male, 10 female, age: 49.05  ±  16.32 years (mean  ±  standard deviation)) and 45 neonates (23 male, 22 female, gestational age: 37.67  ±  2.11 weeks, postnatal age, 2.56  ±  2.67 d) were studied at Columbia University Medical Center. Impedance measurements at 10 kHz were collected for approximately one hour from each subject. The characteristic resistance ratio for each subject was computed and analyzed. The result shows the impedance at or near the skin of newborns is significantly higher than in adult subjects.

  20. Transthoracic electrical impedance during external defibrillation: comparison of measured and modelled waveforms.

    PubMed

    Al Hatib, F; Trendafilova, E; Daskalov, I

    2000-02-01

    The transthoracic electrical impedance is an important defibrillation parameter, affecting the defibrillating current amplitude and energy, and therefore the defibrillation efficiency. A close relationship between transthoracic impedance and defibrillation success rate was observed. Pre-shock measurements (using low amplitude high frequency current) of the impedance were considered a solution for selection of adequate shock voltages or for current-based defibrillation dosage. A recent approach, called 'impedance-compensating defibrillation' was implemented, where the pulse duration was controlled with respect to the impedance measured during the initial phase of the shock. These considerations raised our interest in reassessment of the transthoracic impedance characteristics and the corresponding measurement methods. The purpose of this work is to study the variations of the transthoracic impedance by a continuous measurement technique during the defibrillation shock and comparing the data with results obtained by modelling. Voltage and current impulse waveforms were acquired during cardioversion of patients with atrial fibrillation or flutter. The same type of defibrillation pulse was taken from dogs after induction of fibrillation. The electrodes were located in the anterior position, for both the patients and animals.

  1. Applications of acoustics in the measurement of coal slab thickness

    NASA Technical Reports Server (NTRS)

    Hadden, W. J., Jr.; Mills, J. M.; Pierce, A. D.

    1980-01-01

    The determination of the possibility of employing acoustic waves at ultrasonic frequencies for measurements of thicknesses of slabs of coal backed by shale is investigated. Fundamental information concerning the acoustical properties of coal, and the relationship between these properties and the structural and compositional parameters used to characterize coal samples was also sought. The testing device, which utilizes two matched transducers, is described.

  2. Ares I Scale Model Acoustic Test Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas

    2011-01-01

    Ares I Scale Model Acoustic Test (ASMAT) is a 5% scale model test of the Ares I vehicle, launch pad and support structures conducted at MSFC to verify acoustic and ignition environments and evaluate water suppression systems Test design considerations 5% measurements must be scaled to full scale requiring high frequency measurements Users had different frequencies of interest Acoustics: 200 - 2,000 Hz full scale equals 4,000 - 40,000 Hz model scale Ignition Transient: 0 - 100 Hz full scale equals 0 - 2,000 Hz model scale Environment exposure Weather exposure: heat, humidity, thunderstorms, rain, cold and snow Test environments: Plume impingement heat and pressure, and water deluge impingement Several types of sensors were used to measure the environments Different instrument mounts were used according to the location and exposure to the environment This presentation addresses the observed effects of the selected sensors and mount design on the acoustic and pressure measurements

  3. Generation of optimum pseudorandom signals for respiratory impedance measurements.

    PubMed

    Daróczy, B; Hantos, Z

    1990-02-01

    Spontaneous breathing may impair the reliability of forced oscillatory impedance estimates at low frequencies, especially when the oscillatory power is distributed among many frequency values. Since the amplitude of the external forcing is limited to avoid non-linearities, it is suggested that the total energy of a composite electrical signal driving the loudspeaker be maximized at a given amplitude by finding the optimum phase relationships of the signal components, and that the low-frequency components increase in energy at the expense of the less disturbed high-frequency region. In healthy children and adults and in obstructed patients, the coherences and the coefficients of variation of the respiratory system impedance (Zrs) at 2 and 3 Hz were studied in the case of three test signals of 2-15 Hz bandwidth. Signals T1 and T2 had a flat power spectrum, whereas the components of T3 decreased sharply between 2 and 5 Hz; T1 was generated by simple random selection of phase angles, while optimization for maximum energy was done for T2 and T3. Optimization alone (T2) increased the reliability of the Zrs estimates at all frequencies, whereas enhancement of the low-frequency power (T3) resulted in a radical improvement of the estimates at 2 and 3 Hz, without loss in reliability at higher frequencies.

  4. Measuring Electrolyte Impedance and Noise Simultaneously by Triangular Waveform Voltage and Principal Component Analysis.

    PubMed

    Xu, Shanzhi; Wang, Peng; Dong, Yonggui

    2016-04-22

    In order to measure the impedance variation process in electrolyte solutions, a method of triangular waveform voltage excitation is investigated together with principal component analysis (PCA). Using triangular waveform voltage as the excitation signal, the response current during one duty cycle is sampled to construct a measurement vector. The measurement matrix is then constructed by the measurement vectors obtained from different measurements. After being processed by PCA, the changing information of solution impedance is contained in the loading vectors while the response current and noise information is contained in the score vectors. The measurement results of impedance variation by the proposed signal processing method are independent of the equivalent impedance model. The noise-induced problems encountered during equivalent impedance calculation are therefore avoided, and the real-time variation information of noise in the electrode-electrolyte interface can be extracted at the same time. Planar-interdigitated electrodes are experimentally tested for monitoring the KCl concentration variation process. Experimental results indicate that the measured impedance variation curve reflects the changing process of solution conductivity, and the amplitude distribution of the noise during one duty cycle can be utilized to analyze the contact conditions of the electrode and electrolyte interface.

  5. Measuring Electrolyte Impedance and Noise Simultaneously by Triangular Waveform Voltage and Principal Component Analysis

    PubMed Central

    Xu, Shanzhi; Wang, Peng; Dong, Yonggui

    2016-01-01

    In order to measure the impedance variation process in electrolyte solutions, a method of triangular waveform voltage excitation is investigated together with principal component analysis (PCA). Using triangular waveform voltage as the excitation signal, the response current during one duty cycle is sampled to construct a measurement vector. The measurement matrix is then constructed by the measurement vectors obtained from different measurements. After being processed by PCA, the changing information of solution impedance is contained in the loading vectors while the response current and noise information is contained in the score vectors. The measurement results of impedance variation by the proposed signal processing method are independent of the equivalent impedance model. The noise-induced problems encountered during equivalent impedance calculation are therefore avoided, and the real-time variation information of noise in the electrode-electrolyte interface can be extracted at the same time. Planar-interdigitated electrodes are experimentally tested for monitoring the KCl concentration variation process. Experimental results indicate that the measured impedance variation curve reflects the changing process of solution conductivity, and the amplitude distribution of the noise during one duty cycle can be utilized to analyze the contact conditions of the electrode and electrolyte interface. PMID:27110787

  6. Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators

    PubMed Central

    Kim, Pil-Jong; Kim, Hong-Gee

    2015-01-01

    Objectives The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). Materials and Methods The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC. PMID:25984472

  7. Cosmological implications of baryon acoustic oscillation measurements

    SciTech Connect

    Aubourg, Eric

    2015-12-01

    Here, we derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. Particularly, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibrated physical scale of the sound horizon, the combination of BAO and SN data into an “inverse distance ladder” yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. And while the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2–2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species,

  8. Cosmological implications of baryon acoustic oscillation measurements

    DOE PAGES

    Aubourg, Eric

    2015-12-01

    Here, we derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. Particularly, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibratedmore » physical scale of the sound horizon, the combination of BAO and SN data into an “inverse distance ladder” yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. And while the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2–2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species, Σmν<0.56 eV (95% confidence), improving to Σmν<0.25 eV if we include

  9. Comparison of segmental with whole-body impedance measurements in peritoneal dialysis patients.

    PubMed

    Nescolarde, Lexa; Doñate, Teresa; Piccoli, Antonio; Rosell, Javier

    2008-09-01

    Segmental impedance measurements were obtained using nine electrode configurations in 21 male patients undergoing peritoneal dialysis PD before and after the fluid drainage. For each segment we analyzed the impedance Z and the impedance divided by the height H of the patient Z/H. Our objective was to compare different segmental measurements with whole-body measurements in peritoneal dialysis. The Wilcoxon test was used to analyze the change in impedance produced by a PD session. Pearson or Spearman correlation coefficients were used for continuous or discrete variables, respectively. Statistical significance was set at P<0.05. Similar results were obtained for Z and Z/H. The correlation coefficients between the real R and imaginary X(c) parts of segmental impedances after drainage were within the expected range for healthy population (0.46-0.70), but not before drainage for the abdomen (0.34) and the upper part of the leg (0.24). The correlation between the real part of whole-body and the real part of longitudinal segments in the limbs was high (r=0.807-0.879). Furthermore, the imaginary part of whole-body showed a high correlation with the imaginary part of all longitudinal segments (r=0.856-0.931). The high contribution of arm and leg impedances in the whole-body impedance produced high correlation between whole-body and segmental measurements in legs and arms. In agreement with other previous studies, a significant increase of the arm resistance was detected after fluid drainage. The drainage of fluids in PD patients produced significant changes in the measured real parts of impedance in all measured segments, but only the measurement in the abdomen showed a significant positive correlation (r=0.533) with the extracted fluid volume. This low correlation indicates that the individual assessment of fluid volumes using segmental measurements will be highly inaccurate.

  10. Transvers Impedance Measurements of the Modified DARHT-2Accelerator Cell Design

    SciTech Connect

    Briggs, Dick; Waldron, Will

    2005-11-30

    The DARHT-2 accelerator cells have been redesigned to make their high voltage performance more robust. At the outset of the DARHT-2 development program about 8 years ago, an extensive campaign was mounted to minimize the transverse impedance of the original cell design. Since the initial spec on the machine was a beam current of 4 kA, the control of beam-breakup (BBU) amplification with a 2 microsecond pulse length was considered to be one the most critical issues in the design. Even after advances in detector technology allowed the beam current requirement to be lowered to 2 kA, the goal for the standard cell impedance was kept at {approx}300 ohms/meter to allow for the possibility of future beam current upgrades to 4 kA without any modifications in the cells. The results of this campaign to minimize the transverse impedance are described in detail in Reference 1. After several iterations in the design of ferrite dampers and the anode finger stock shape, the measured (peak) impedance of the original standard cell was determined to be about 280 ohms/meter. (As a reference point, the measured impedance of the DARHT-1 cell is about 880 ohms/meter). This impedance provided such a wide safety margin against BBU amplification at 2 kA that it was felt that the cell redesign could focus on voltage holding without any detailed considerations of impacts on the transverse impedance. Now that a baseline design for the DARHT-2 cell has been established and tested, however, it was felt that a measurement of its impedance would be prudent. The results of these impedance measurements are presented in this note. The objective was mainly to do a ''quick check'' to ensure that there were no surprises, and to provide an estimate of the BBU frequencies and growth rates to the experimental test program.

  11. Measurement and mathematical simulation of acoustic characteristics of an artificially lengthened vocal tract

    NASA Astrophysics Data System (ADS)

    Radolf, Vojtěch; Horáček, Jaromír; Dlask, Pavel; Otčenášek, Zdeněk; Geneid, Ahmed; Laukkanen, Anne-Maria

    2016-03-01

    Phonation into tubes is used for voice training and therapy. In the present study, the formant frequencies were estimated from measurements of the acoustic pressure and the acoustic input impedance for a plexiglass model of the vocal tract (VT) prolonged by a glass tube. Similar transfer function measurements were performed with a human VT in vivo. The experimental results matched the mathematical modelling and confirmed the legitimacy of assuming rigid walls in mathematical simulations of the acoustic characteristics of an artificial VT model prolonged by a tube. However, this study also proved a considerable influence from soft tissues in the yielding walls of human VT cavities on the first formant frequency, F1. The measured F1 for the VT model corresponded to the computed value of 78 Hz. The experiments in a human instead resulted in a much higher value of F1: about 200 Hz. The results confirm that a VT model with yielding walls must be considered for mathematical modelling of the occluded or semi-occluded human vocal tract, e.g. prolonged by tubes or straws. This is explained by an acoustic-structural interaction of the vocal tract cavities with a mechanical low-frequency resonance of the soft tissue in the larynx.

  12. Acoustic-velocity measurements in materials using a regenerative method

    DOEpatents

    Laine, E.F.

    1982-09-30

    Acoustic energy is propatated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

  13. Acoustic velocity measurements in materials using a regenerative method

    DOEpatents

    Laine, Edwin F.

    1986-01-01

    Acoustic energy is propagated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

  14. Evaluation of a novel correction procedure to remove electrode impedance effects from broadband SIP measurements

    NASA Astrophysics Data System (ADS)

    Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Treichel, Andrea; Vereecken, Harry

    2016-12-01

    Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements to improve the accuracy of broadband complex electrical resistivity measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference < 0.2 mrad) up to a frequency of 10 kHz after the effect of the different electrode impedances was removed. Finally, SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.

  15. Rapid Impedance Spectrum Measurements for Onboard State-of-Health Applications

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chinh D. Ho

    2012-06-01

    Rapid impedance measurements can provide a useful online tool for improved state-of-health estimation. A validation study has been initiated at the Idaho National Laboratory for a rapid impedance technique known as Harmonic Compensated Synchronous Detection. This technique enables capturing the impedance spectra over a broad frequency range within about ten seconds. Commercially available lithium-ion cells are being calendar-life aged at 50°C with reference performance tests at 30°C every 32.5 days to gauge degradation The cells have completed the first set of reference performance tests and preliminary results are presented. The spectra change as a function of temperature and depth-of-discharge condition, as expected. The data indicate that the rapid impedance measurement technique is a benign measurement tool that can be successfully used to gauge changes in the corresponding pulse resistance.

  16. Circuits and methods for impedance determination using active measurement cancelation

    DOEpatents

    Jamison, David K.

    2016-12-13

    A delta signal and opposite delta signal are generated such that a sum of the two signals is substantially zero. The delta signal is applied across a first set of electrochemical cells. The opposite delta signal is applied across a second set of electrochemical cells series connected to the first set. A first held voltage is established as the voltage across the first set. A second held voltage is established as the voltage across the second set. A first delta signal is added to the first held voltage and applied to the first set. A second delta signal is added to the second held voltage and applied to the second set. The current responses due to the added delta voltages travel only into the set associated with its delta voltage. The delta voltages and the current responses are used to calculate the impedances of their associated cells.

  17. Sensitive immunodetection through impedance measurements onto gold functionalized electrodes.

    PubMed

    Ameur, S; Martelet, C; Jaffrezic-Renault, N; Chovelon, J M

    2000-01-01

    This article deals with a direct electrochemical method of detecting antigens using new methods of functionalization of gold electrodes. Based on the reacting ability of gold with sulfhydryl groups, three protocols for the fixation of antibodies have been explored. They are based on either the self-assembling properties of functional thiols bearing long alkyl chains or the possibility of a direct coupling of antibody moieties. Coverage rates as high as 97% can be reached. The analysis of the electrochemical impedance behavior of such layers can lead to a sensitive method for the direct detection of the antibody/antigen interaction. The addition of a redox couple in the tested solution, acting as an amplifier, allowed detection limits for the antigens as low as a few picograms/milliliter to be reached.

  18. Measurements of Impedance and Attenuation at CENELEC Bands for Power Line Communications Systems

    PubMed Central

    Cavdar, I. Hakki; Karadeniz, Engin

    2008-01-01

    Power line impedance is a very important parameter on the design of power line communications (PLC) modem architecture. Variations on the impedance of the power line affect the communications circuit performance. In order to determine impedance of the power lines, measurements were carried out in Turkey at frequencies ranging from 10 to 170 kHz, (CENELEC A,B,C,D bands). Measurements were conducted in three categories: rural, urban and the industrial power lines. Experimental results are presented in graphical form. The measured impedances were determined as 3-17 ohms, 1-17 ohms, and 1-21 ohms for rural, urban and the industrial lines, respectively. A set of the formulas between impedance and frequency are developed on the power lines using the regression analysis from the obtained empirical data. Signal attenuations on the power lines in the CENELEC band are also measured for rural, urban and industrial regions. Attenuation measurements are repeated for phase-neutral, phase-ground and the neutral-ground conductors. Signal attenuations are found to be 4-30 dB, for different power lines. To establish validity of obtained results for the design of PLC systems, the results are compared with previous investigations. The effects of some household appliances such as TV, PC, UPS, lighting and cooling systems on the impedances and the attenuations for power line communications systems are observed. Some suggestions and proposals are presented for PLC modem designers. PMID:27873974

  19. Influence of measurement procedure on quality of impedance spectra on lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Budde-Meiwes, Heide; Kowal, Julia; Sauer, Dirk Uwe; Karden, Eckhard

    Many battery simulation models, but also electrochemical interpretations are based on impedance spectroscopy. However, the impedance of a battery is influenced by various factors, e.g. in the case of a lead-acid battery: state of charge (SOC), charging or discharging, superimposed dc current, short-term history or homogeneity of the electrolyte. This paper analyses the impact of those factors on impedance spectra of lead-acid batteries. The results show that very detailed information about the conditions during the measurement is crucial for the correct interpretation of a spectrum.

  20. Validation of a Numerical Method for Determining Liner Impedance

    NASA Technical Reports Server (NTRS)

    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.

  1. A new contactless impedance sensor for void fraction measurement of gas-liquid two-phase flow

    NASA Astrophysics Data System (ADS)

    Ji, Haifeng; Chang, Ya; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing

    2016-12-01

    With impedance elimination principle and phase sensitive demodulation (PSD) technique, this work aims to develop a new contactless impedance sensor, which is suitable for the void fraction measurement of gas-liquid two-phase flow. The impedance elimination principle is used to overcome the unfavorable influences of the coupling capacitances, i.e. the capacitive reactances of the coupling capacitances are eliminated by the inductive reactance of an introduced inductor. PSD technique is used to implement the impedance measurement. Unlike the conventional conductance/impedance sensors which use the equivalent conductance (the real part of the impedance) or the amplitude of the impedance of gas-liquid two-phase flow, the new contactless impedance sensor makes full use of the total impedance information of gas-liquid two-phase flow (including the amplitude, the real part and the imaginary part of the impedance, especially the imaginary part) to implement the void fraction measurement. As a preliminary study, to verify the effectiveness of the new contactless impedance sensor, two prototypes (with different inner diameters of 17.0 mm and 22.0 mm) are developed and experiments are carried out. Two typical flow patterns (bubble flow and stratified flow) of gas-liquid two-phase flow are investigated. The experimental results show that the new contactless impedance sensor is successful and effective. Compared with the conventional conductance/impedance sensors, the new contactless impedance sensor can avoid polarization effect and electrochemical erosion effect. The total impedance information is used and the void fraction measurement performance of the new sensor is satisfactory. The experimental results also indicate that the imaginary part of the impedance of gas-liquid two-phase flow is very useful for the void fraction measurement. Making full use of the total impedance information of gas-liquid two-phase flow can effectively improve the void fraction measurement

  2. Scale Model Thruster Acoustic Measurement Results

    NASA Technical Reports Server (NTRS)

    Vargas, Magda; Kenny, R. Jeremy

    2013-01-01

    The Space Launch System (SLS) Scale Model Acoustic Test (SMAT) is a 5% scale representation of the SLS vehicle, mobile launcher, tower, and launch pad trench. The SLS launch propulsion system will be comprised of the Rocket Assisted Take-Off (RATO) motors representing the solid boosters and 4 Gas Hydrogen (GH2) thrusters representing the core engines. The GH2 thrusters were tested in a horizontal configuration in order to characterize their performance. In Phase 1, a single thruster was fired to determine the engine performance parameters necessary for scaling a single engine. A cluster configuration, consisting of the 4 thrusters, was tested in Phase 2 to integrate the system and determine their combined performance. Acoustic and overpressure data was collected during both test phases in order to characterize the system's acoustic performance. The results from the single thruster and 4- thuster system are discussed and compared.

  3. Experimental investigation of microwave interaction with magnetoplasma in miniature multipolar configuration using impedance measurements

    SciTech Connect

    Dey, Indranuj Toyoda, Yuji; Yamamoto, Naoji; Nakashima, Hideki

    2014-09-15

    A miniature microwave plasma source employing both radial and axial magnetic fields for plasma confinement has been developed for micro-propulsion applications. Plasma is initiated by launching microwaves via a short monopole antenna to circumvent geometrical cutoff limitations. The amplitude and phase of the forward and reflected microwave power is measured to obtain the complex reflection coefficient from which the equivalent impedance of the plasma source is determined. Effect of critical plasma density condition is reflected in the measurements and provides insight into the working of the miniature plasma source. A basic impedance calculation model is developed to help in understanding the experimental observations. From experiment and theory, it is seen that the equivalent impedance magnitude is controlled by the coaxial discharge boundary conditions, and the phase is influenced primarily by the plasma immersed antenna impedance.

  4. A novel instrument to measure acoustic resonances of the vocal tract during phonation

    NASA Astrophysics Data System (ADS)

    Epps, J.; Smith, J. R.; Wolfe, J.

    1997-10-01

    Acoustic resonances of the vocal tract give rise to formants (broad bands of acoustic power) in the speech signal when the vocal tract is excited by a periodic signal from the vocal folds. This paper reports a novel instrument which uses a real-time, non-invasive technique to measure these resonances accurately during phonation. A broadband acoustic current source is located just outside the mouth of the subject and the resulting acoustic pressure is measured near the lips. The contribution of the speech signal to the pressure spectrum is then digitally suppressed and the resonances are calculated from the input impedance of the vocal tract as a function of the frequency. The external excitation signal has a much smaller harmonic spacing than does the periodic signal from the vocal folds and consequently the resonances are determined much more accurately due to the closer sampling. This is particularly important for higher pitched voices and we demonstrate that this technique can be markedly superior to the curve-fitting technique of linear prediction. The superior frequency resolution of this instrument which results from external vocal tract excitation can provide the precise, stable, effective, articulatory feedback considered essential for some language-learning and speech-therapy applications.

  5. Comparison of acoustic and mechanical excitation for modal response measurements

    NASA Astrophysics Data System (ADS)

    Musson, B. G.; Stevens, J. R.

    An acoustic field is examined as an alternate to mechanical excitation of a test specimen to measure modal response. A square, flat plate with clamped edges is used because classical analytical solutions to its modal analysis are readily available. A small hammer with a built-in force transducer is used to mechanically excite the plate, and the plate is excited with electro-pneumatic acoustic drivers coupled to a progressive-wave test fixture. Band limited random amplitude acoustic waves over a frequency range of 50 to 1000 Hz are applied at grazing incidence to the plate. The acoustic field is characterized and a microphone at a single fixed position is used to provide the reference forcing function. Results are compared with the analytical solutions and with the mechanically excited results. Conclusions are presented concerning the equivalence of acoustic and mechanical excitation for obtaining modal response.

  6. Acoustic Characterization of Grass-cover Ground

    DTIC Science & Technology

    2014-11-20

    ABSTRACT A custom designed acoustic impedance tube was used to measure acoustic properties ofnonconsolidated materials, specifically soils and grass...covered ground. The tube was config- ured vertically for studying acoustic properties of granular materials i.e. soil and dirt. Software was developed to...collect data and calibrate the impedance tube . An equivalent fluid model for describing sound propagation in rigid fi·ame porous media was used to

  7. Drilling electrode for real-time measurement of electrical impedance in bone tissues.

    PubMed

    Dai, Yu; Xue, Yuan; Zhang, Jianxun

    2014-03-01

    In order to prevent possible damages to soft tissues, reliable monitoring methods are required to provide valuable information on the condition of the bone being cut. This paper describes the design of an electrical impedance sensing drill developed to estimate the relative position between the drill and the bone being drilled. The two-electrode method is applied to continuously measure the electrical impedance during a drill feeding movement: two copper wire brushes are used to conduct electricity in the rotating drill and then the drill is one electrode; a needle is inserted into the soft tissues adjacent to the bone being drilled and acts as another electrode. Considering that the recorded electrical impedance is correlated with the insertion depth of the drill, we theoretically calculate the electrode-tissue contact impedance and prove that the rate of impedance change varies considerably when the drill bit crosses the boundary between two different bone tissues. Therefore, the rate of impedance change is used to determine whether the tip of the drill is located in one of cortical bone, cancellous bone, and cortical bone near a boundary with soft tissue. In vitro experiments in porcine thoracic spines were performed to demonstrate the feasibility of the impedance sensing drill. The experimental results indicate that the drill, used with the proposed data-processing method, can provide accurate and reliable breakthrough detection in the bone-drilling process.

  8. Sensing fluid viscosity and density through mechanical impedance measurement using a whisker transducer

    NASA Astrophysics Data System (ADS)

    Ju, Feng; Ling, Shih-Fu

    2013-05-01

    This paper presents a new technique for fluid viscosity and density sensing through measuring the mechanical impedance of the fluid load applied on a sphere. A piezoelectric whisker transducer (WT) is proposed which acts simultaneously as both the actuator to excite the sphere tip to oscillate in the fluid and the sensor to measure the force, velocity and mechanical impedance. The relationship between mechanical impedance of the fluid load and electrical impedance of the WT is derived based on a transduction matrix model which characterizes the electro-mechanical transduction process of the WT in both directions. The mechanical impedance is further related to the fluid viscosity and density using a theoretical model. The establishment of this fluid-mechanical-electrical relationship allows the WT to extract the fluid viscosity and density conveniently and accurately just from its electrical impedance. Experimental studies are carried out to calibrate the WT and test its performance using glycerol-water mixtures. It is concluded that the WT is capable of providing results comparable to those of standard viscometers within a wide measurement range due to its low working frequency and large vibration amplitude. Its unique self-actuation-and-sensing feature makes it a suitable solution for online fluid sensing.

  9. A microchip integrating cell array positioning with in situ single-cell impedance measurement.

    PubMed

    Guo, Xiaoliang; Zhu, Rong; Zong, Xianli

    2015-10-07

    This paper presents a novel microarray chip integrating cell positioning with in situ, real-time and long-time impedance measurement on a single cell. The microchip integrates a plurality of quadrupole-electrode units (termed positioning electrodes) patterned into an array with pairs of planar electrodes (termed measuring electrodes) located at the centers of each quadrupole-electrode unit. The positioning electrodes are utilized to trap and position living cells onto the measuring electrodes based on negative dielectrophoresis (nDEP), while the measuring electrodes are used to measure impedances of the trapped single cells. Each measuring electrode has a small footprint area of 7 × 7 μm(2) to ensure inhabiting only one single cell on it. However, the electrode with a small surface area has a low double-layer capacitance when it is immersed in a liquid solution, thus generating a large double-layer impedance, which reduces the sensitivity for impedance measurement on the single cell. To enlarge the effective surface areas of the measuring electrodes, a novel surface-modification process is proposed to controllably construct gold nanostructures on the surfaces of the measuring electrodes while the positioning electrodes are unstained. The double layer capacitances of the modified electrodes are increased by about one order after surface-modification. The developed microchip is used to monitor the adhering behavior of a single HeLa cell by measuring its impedance spectra in real time. The measured impedance is analyzed and used to extract cellular electrical parameters, which demonstrated that the cell compresses the electrical double layer in the process of adherence and adheres onto the measuring electrodes after 4-5 hours.

  10. Measurement of the Q value of an acoustic resonator.

    PubMed

    Biwa, Tetsushi; Ueda, Yuki; Nomura, Hiroshi; Mizutani, Uichiro; Yazaki, Taichi

    2005-08-01

    A cylindrical acoustic resonator was externally driven at the first resonance frequency by a compression driver. The acoustic energy stored in the resonator and the power dissipated per unit time were evaluated through the simultaneous measurements of acoustic pressure and velocity, in order to determine the Q value of the resonator. The resulting Q value, being employed as a measure of the damping in a resonator, was obtained as 36. However, the Q value determined from a frequency response curve known as a conventional technique turned out to be 25, which is 30% less than that obtained in the present method. By further applying these two methods in the case of a resonator having an acoustic load inside, we present an accurate measurement of the Q value of the resonator by making full use of its definition.

  11. Acoustic wayfinding: A method to measure the acoustic contrast of different paving materials for blind people.

    PubMed

    Secchi, Simone; Lauria, Antonio; Cellai, Gianfranco

    2017-01-01

    Acoustic wayfinding involves using a variety of auditory cues to create a mental map of the surrounding environment. For blind people, these auditory cues become the primary substitute for visual information in order to understand the features of the spatial context and orient themselves. This can include creating sound waves, such as tapping a cane. This paper reports the results of a research about the "acoustic contrast" parameter between paving materials functioning as a cue and the surrounding or adjacent surface functioning as a background. A number of different materials was selected in order to create a test path and a procedure was defined for the verification of the ability of blind people to distinguish different acoustic contrasts. A method is proposed for measuring acoustic contrast generated by the impact of a cane tip on the ground to provide blind people with environmental information on spatial orientation and wayfinding in urban places.

  12. Optimally tuned resonant negative capacitance for piezoelectric shunt damping based on measured electromechanical impedance

    NASA Astrophysics Data System (ADS)

    Salloum, Rogério; Heuss, Oliver; Götz, Benedict; Mayer, Dirk

    2015-04-01

    In this paper, a new tuning method for shunt damping with a series resistance, inductance and negative capacitance is proposed and its validity is investigated. It is based on the measured electromechanical impedance of a piezoelectric system, which is represented through an equivalent electrical circuit that takes into account the characteristics of the piezoelectric transducer and the host structure. Afterwards, an additional circuit representing the shunt is connected and the Norton equivalent impedance is obtained at the terminals that represent the mechanical mode of interest. During the tuning process, the optimal shunt parameters are found by minimizing the maximum absolute value of the Norton equivalent impedance over a defined frequency range through a numerical optimization. Taking benefit from the analogy between electrical impedance and mechanical admittance, the minimization of different mechanical responses (displacement, velocity or acceleration) is also proposed and the different optimum shunt parameters obtained are compared. In view of real technical applications, this method allows the integration of a real negative capacitance circuit, i.e., a negative impedance converter, rather than an ideal component. It is thus possible to use the impedance of this circuit and optimize the individual component values. Since this method is based on one simple measurement, it can be applied to arbitrary structures without the need of complex dynamic tests or expensive finite elements calculations. Finally, an experimental analysis is carried out in order to compare the damping performance of the proposed method and the conventional analytical method that minimizes a mechanical frequency response function.

  13. Measuring the multi-frequency electrical impedance of the mouse gastrocnemius muscle using a tetrapolar technique

    NASA Astrophysics Data System (ADS)

    Li, J.; Fogerson, P. M.; Rutkove, S. B.

    2010-04-01

    Electrical impedance methods can be used to evaluate and monitor neuromuscular disease states. Recently, we have applied tetrapolar surface electrical impedance methods to the gastrocnemius muscle of the rat for this purpose and substantial changes in the impedance parameters after sciatic nerve crush can be identified. In order to be able to study additional animal models of nerve and muscle disease, however, it would highly desirable to be able to perform such impedance measurements in the mouse. Yet the small size of the mouse presents a substantial technical challenge. In this study, we evaluate a basic approach for performing such measurements. A series of thin, stainless steel strip electrodes affixed to the gastrocnemius and interfaced via a separate connector to the Imp SFB7® (Impedimed, Inc), provided an effective means for obtaining impedance data in the 20-500 kHz range. After two weeks, test-retest reproducibility was good, with intra-class correlation coefficients as high 0.84 and variability as low as 12.86 ± 6.18% in the 15 mice studied. Using this approach, it may now be possible to study impedance changes in a variety of mouse models of neuromuscular disease, including amyotrophic lateral sclerosis, spinal muscular atrophy, muscular dystrophy and Charcot-Marie-Tooth disease.

  14. Acoustic temperature measurement in a rocket noise field.

    PubMed

    Giraud, Jarom H; Gee, Kent L; Ellsworth, John E

    2010-05-01

    A 1 μm diameter platinum wire resistance thermometer has been used to measure temperature fluctuations generated during a static GEM-60 rocket motor test. Exact and small-signal relationships between acoustic pressure and acoustic temperature are derived in order to compare the temperature probe output with that of a 3.18 mm diameter condenser microphone. After preliminary plane wave tests yielded good agreement between the transducers within the temperature probe's ∼2 kHz bandwidth, comparison between the temperature probe and microphone data during the motor firing show that the ±∼3 K acoustic temperature fluctuations are a significant contributor to the total temperature variations.

  15. Influence of sodium chloride content in electrolyte solution on electrochemical impedance measurements of human dentin

    PubMed Central

    Eldarrat, Aziza; High, Alec; Kale, Girish

    2017-01-01

    Background: The aim of this study was to investigate the influence of sodium chloride (NaCl) content in electrolyte solution on electrochemical impedance measurements of human dentin by employing electrochemical impedance spectroscopy. Materials and Methods: Dentin samples were prepared from extracted molars. Electrochemical impedance measurements were carried out over a wide frequency range (0.01Hz-10MHz). After measurements, samples were characterized using scanning electron microscopy. Results: Electrochemical impedance measurements showed that the mean values of dentin electrical resistance were 4284, 2062, 1336, 53 and 48kΩ at different NaCl contents in electrolyte solution. One-way ANOVA test of mean values of dentin electrical resistance revealed a significant difference (P < 0.0001) as a function of NaCl content in electrolyte solution. Comparing electrical resistance values of dentin samples at 0.05% w/v and 0.9% w/v concentrations were found to be significantly different (P < 0.05 at 95% confidence level). Scanning electron microscopy revealed structure of dentin sample with intertubular dentin matrix and distribution of patent dentinal tubules. Conclusion: This in vitro study indicated, through electrochemical impedance spectroscopy measurements, that electrical resistance of dentin was affected by the concentration of NaCl in electrolyte solution. It is clear from the current study that NaCl concentration in electrolyte solution has a marked influence on dentin electrical resistance. Therefore, this baseline data need to be considered in any future study on dental samples. PMID:28348614

  16. Non-invasive measurement of micro-area skin impedance in vivo

    NASA Astrophysics Data System (ADS)

    Li, Dachao; Liang, Wenshuai; Liu, Tongkun; Yu, Haixia; Xu, Kexin

    2011-12-01

    Volume measurement of interstitial fluid transdermally extracted is important in continuous glucose monitoring instrument. The volume of transdermally extracted interstitial fluid could be determined by a skin permeability coefficient. If the skin impedance which is the indicator of skin permeability coefficient can be accurately measured, the volume of interstitial fluid can be calculated based on the relationship between the indicator and the skin permeability coefficient. The possibility of using the skin impedance to indicate the skin permeability coefficient is investigated. A correlation model between the skin impedance and the skin permeability coefficient is developed. A novel non-invasive method for in vivo, real-time, and accurate measurement of skin impedance within a micro skin area is brought forward. The proposed measurement method is based on the theory that organisms saliva and interstitial fluid are equipotential. An electrode is put on the surface of a micro skin area and another one is put in the mouth to be fully contacted with saliva of an animal in the experiments. The electrode in mouth is used to replace the implantable subcutaneous electrode for non-invasive measurement of skin impedance in vivo. A biologically compatible AC current with amplitude of 100mv and frequency of 10Hz is applied to stimulate the micro skin area by the two electrodes. And then the voltage and current between the two electrodes are measured to calculate the skin impedance within a micro skin area. The measurement results by electrode in mouth are compared with the results by subcutaneous electrode in animal experiments and they are consistent so the proposed measurement method is verified well. The effect of moisture and pressure for the measurement is also studied in the paper.

  17. Temperature-stable parallel-plate dielectric cell for broadband liquid impedance measurements

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Chandra, Satyan; Mellor, Brett L.; Arellano, Jesus

    2010-12-01

    A liquid impedance cell for broadband impedance measurements up to 110 MHz is presented. The design incorporates temperature control and minimizes parasitic capacitance and inductance. The cell is simple to fabricate and uses chemically resistant materials, stainless steel, and Teflon. This dielectric cell can be used in a variety of liquid measurements, particularly those related to impedance measurements of biological objects in solution. Temperature control is illustrated in measurements of the permittivity of deionized water from 5 to 55 °C. Numerical fitting procedures employed on the relaxation curves indicate good agreement with previous studies on beta-lactoglobulin and hen lysozyme. Titration capability is demonstrated through dielectric titration of hen lysozyme and beta-lactoglobulin.

  18. Particle trapping and impedance measurement using bilayer electrodes integrated with microcavity structure

    NASA Astrophysics Data System (ADS)

    Chen, Guan-Ting; Liu, Chia-Feng; Jang, Ling-Sheng; Li, Shun-Lai; Wang, Min-Haw

    2017-03-01

    Traditional planar electrodes for single-particle impedance measurement have difficulty in trapping and positioning particles. This paper proposes a microfluidic device for single-particle trapping and impedance measurement with a microcavity configuration. A carbon dioxide (CO2) laser technique was used to fabricate the microcavity structure, which can capture 15 µm diameter particles without requiring additional trapping structures. The measurement electrodes on both sides of the microcavity were fabricated using electroplating and deposition techniques. The advantages of the microcavity structure and electrodes are discussed. The bottom electrode spreads into the microcavity to increase measurement sensitivity and shrink the exit aperture to around 10 µm for particle trapping. The experimental results show that the device successfully captured particles and distinguished the impedance of a particle from that of phosphate-buffered saline solution.

  19. The determination of the acoustic parameters of volcanic rocks from compressional velocity measurements

    USGS Publications Warehouse

    Carroll, R.D.

    1969-01-01

    A statistical analysis was made of the relationship of various acoustic parameters of volcanic rocks to compressional wave velocities for data obtained in a volcanic region in Nevada. Some additional samples, chiefly granitic rocks, were also included in the study to extend the range of parameters and the variety of siliceous rock types sampled. Laboratory acoustic measurements obtained on 62 dry core samples were grouped with similar measurements obtained from geophysical logging devices at several depth intervals in a hole from which 15 of the core samples had been obtained. The effects of lithostatic and hydrostatic load on changing the rock acoustic parameters measured in the hole were noticeable when compared with the laboratory measurements on the same core. The results of the analyses determined by grouping all of the data, however, indicate that dynamic Young's, shear and bulk modulus, shear velocity, shear and compressional characteristic impedance, as well as amplitude and energy reflection coefficients may be reliably estimated on the basis of the compressional wave velocities of the rocks investigated. Less precise estimates can be made of density based on the rock compressional velocity. The possible extension of these relationships to include many siliceous rocks is suggested. ?? 1969.

  20. New equivalent-electrical circuit model and a practical measurement method for human body impedance.

    PubMed

    Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

    2015-01-01

    Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.

  1. Classroom acoustics in Omaha, Nebraska: Measurements and outreach

    NASA Astrophysics Data System (ADS)

    Bowden, Erica E.; Wang, Lily M.; Bradley, David T.

    2002-11-01

    This project collected data detailing the current status of classroom acoustics while simultaneously increasing awareness of educational acoustics and exposure to acoustical engineering research in local schools. In 8 Omaha-area schools, 2 acoustical aspects which directly influence speech intelligibility were measured and studied: (1) background noise levels resulting from a building's mechanical systems; and (2) reverberation times within the classroom. Prior to each measurement session, a presentation on good classroom acoustic principles was presented to the teacher and students in that classroom. Subsequently, the teacher and students assisted the principal investigator and research assistants in the measurement of the acoustic data from their classroom. In total, 13 classrooms were studied, with the assistance of 425 middle and high school students in 14 different classes. The background noise results have been associated with commonly used noise criterion curves. Results are compared to recommended background noise levels and reverberation times suggested by ANSI standard S12.60-2002. The resulting database provides knowledge on the current status of classrooms in Omaha, and may be indicative of classroom situations across the midwestern United States.

  2. Crew Quarters (CQ) and Electromagnetic Interference (EMI) Measurement Facility Combined Impedance Study

    NASA Technical Reports Server (NTRS)

    Scully, Robert C.

    2011-01-01

    This report documents an investigation into observed failures associated with conducted susceptibility testing of Crew Quarters (CQ) hardware in the Johnson Space Center (JSC) Electromagnetic Interference (EMI) Measurement Facility, and the work accomplished to identify the source of the observed behavior. Investigation led to the conclusion that the hardware power input impedance was interacting with the facility power impedance leading to instability at the observed frequencies of susceptibility. Testing performed in other facilities did not show this same behavior, pointing back to the EMI Measurement Facility power as the potential root cause. A LISN emulating the Station power bus impedance was inserted into the power circuit, and the susceptibility was eliminated from the measurements.

  3. A Basic Study About Multi Channel Measurement of Skin Impedance Vector Loci on the Acupuncture Points

    DTIC Science & Technology

    2007-11-02

    Agency Name(s) and Address(es) US Army Research, Development & Standardization Group (UK) PSC 802 Box 15 FPO AE 09499-1500 Sponsor/Monitor’s Acronym(s...each measurement we perform. Additionally, we applied the results obtained to per- foming 4 channel measurments of skin impedance vector loci around

  4. The development of the miniaturized waveform receiver with the function measuring Antenna Impedance in space plasmas

    NASA Astrophysics Data System (ADS)

    Ishii, H.; Kojima, H.; Fukuhara, H.; Okada, S.; Yamakawa, H.

    2012-04-01

    Plasma wave is one of the most essential physical quantities in the solar terrestrial physics. The role of plasma wave receiver onboard satellites is to detect plasma waves in space with a good signal to noise ratio. There are two types of plasma wave receivers, the sweep frequency analyzer and the waveform capture. While the sweep frequency analyzer provides plasma wave spectra, the waveform capture obtains waveforms with phase information that is significant in studying nonlinear phenomena. Antenna sensors to observe electric fields of the plasma waves show different features in plasmas from in vacuum. The antenna impedances have specific characteristics in the frequency domain because of the dispersion of plasmas. These antenna impedances are expressed with complex number. We need to know not only the antenna impedances but also the transfer functions of plasma wave receiver's circuits in order to calibrate observed waveforms precisely. The impedances of the electric field antennas are affected by a state of surrounding plasmas. Since satellites run through various regions with different plasma parameters, we precisely should measure the antenna impedances onboard spacecraft. On the contrary, we can obtain the plasma density and by measuring the antenna impedances. Several formulas of the antenna impedance measurement system were proposed. A synchronous detection method is used on the BepiColombo Mercury Magnetospheric Orbiter (MMO), which will be launched in 2014. The digital data are stored in the onboard memory. They are read out and converted to the analog waveforms by D/A converter. They are fed into the input of the preamplifiers of antenna sensors through a resistor. We can calculate a transfer function of the circuit by applying the synchronous detection method to the output waveform from waveform receivers and digital data as a signal source. The size of this system is same as an A5 board. In recent years, Application Specific Integrated Circuit (ASIC

  5. Rapid Impedance Spectrum Measurements for State-of-Health Assessment of Energy Storage Devices

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chester G. Motloch; William H. Morrison

    2012-04-01

    Harmonic compensated synchronous detection (HCSD) is a technique that can be used to measure wideband impedance spectra within seconds based on an input sum-of-sines signal having a frequency spread separated by harmonics. The battery (or other energy storage device) is excited with a sum-of-sines current signal that has a duration of at least one period of the lowest frequency. The voltage response is then captured and synchronously detected at each frequency of interest to determine the impedance spectra. This technique was successfully simulated using a simplified battery model and then verified with commercially available Sanyo lithium-ion cells. Simulations revealed the presence of a start-up transient effect when only one period of the lowest frequency is included in the excitation signal. This transient effect appears to only influence the low-frequency impedance measurements and can be reduced when a longer input signal is used. Furthermore, lithium-ion cell testing has indicated that the transient effect does not seem to impact the charge transfer resistance in the mid-frequency region. The degradation rates for the charge transfer resistance measured from the HCSD technique were very similar to the changes observed from standardized impedance spectroscopy methods. Results from these studies, therefore, indicate that HCSD is a viable, rapid alternative approach to acquiring impedance spectra.

  6. An Analysis of Electrical Impedance Measurements Applied for Plant N Status Estimation in Lettuce (Lactuca sativa)

    PubMed Central

    Muñoz-Huerta, Rafael F.; de J. Ortiz-Melendez, Antonio; Guevara-Gonzalez, Ramon G.; Torres-Pacheco, Irineo; Herrera-Ruiz, Gilberto; Contreras-Medina, Luis M.; Prado-Olivarez, Juan; Ocampo-Velazquez, Rosalia V.

    2014-01-01

    Nitrogen plays a key role in crop yields. Hence, farmers may apply excessive N fertilizers to crop fields, inducing environmental pollution. Crop N monitoring methods have been developed to improve N fertilizer management, most of them based on leaf or canopy optical-property measurements. However, sensitivity to environmental interference remains an important drawback. Electrical impedance has been applied to determine the physiological and nutritional status of plant tissue, but no studies related to plant-N contents are reported. The objective of this article is to analyze how the electrical impedance response of plants is affected by their N status. Four sets of lettuce (Lactuca sativa L.) with a different N-source concentrations per set were used. Total nitrogen and electrical impedance spectra (in a 1 to 100 kHz frequency range) were measured five times per set, three times every other day. Minimum phase angles of impedance spectra were detected and analyzed, together with the frequency value in which they occurred, and their magnitude at that frequency. High and positive correlation was observed between plant N content and frequency values at minimum phase angle with no significant variations detected between days of measurement. These results suggest that electrical impedance can be sensitive to plant N status. PMID:25057134

  7. An analysis of electrical impedance measurements applied for plant N status estimation in lettuce (Lactuca sativa).

    PubMed

    Muñoz-Huerta, Rafael F; Ortiz-Melendez, Antonio de J; Guevara-Gonzalez, Ramon G; Torres-Pacheco, Irineo; Herrera-Ruiz, Gilberto; Contreras-Medina, Luis M; Prado-Olivarez, Juan; Ocampo-Velazquez, Rosalia V

    2014-06-27

    Nitrogen plays a key role in crop yields. Hence, farmers may apply excessive N fertilizers to crop fields, inducing environmental pollution. Crop N monitoring methods have been developed to improve N fertilizer management, most of them based on leaf or canopy optical-property measurements. However, sensitivity to environmental interference remains an important drawback. Electrical impedance has been applied to determine the physiological and nutritional status of plant tissue, but no studies related to plant-N contents are reported. The objective of this article is to analyze how the electrical impedance response of plants is affected by their N status. Four sets of lettuce (Lactuca sativa L.) with a different N-source concentrations per set were used. Total nitrogen and electrical impedance spectra (in a 1 to 100 kHz frequency range) were measured five times per set, three times every other day. Minimum phase angles of impedance spectra were detected and analyzed, together with the frequency value in which they occurred, and their magnitude at that frequency. High and positive correlation was observed between plant N content and frequency values at minimum phase angle with no significant variations detected between days of measurement. These results suggest that electrical impedance can be sensitive to plant N status.

  8. Studies of longitudinal profile of electron bunches and impedance measurements at Indus-2 synchrotron radiation source

    NASA Astrophysics Data System (ADS)

    Garg, Akash Deep; Yadav, S.; Kumar, Mukesh; Shrivastava, B. B.; Karnewar, A. K.; Ojha, A.; Puntambekar, T. A.

    2016-04-01

    Indus-2 is a 3rd generation synchrotron radiation source at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We study the longitudinal profile of electrons in Indus-2 by using dual sweep synchroscan streak camera at visible diagnostic beamline. In this paper, the longitudinal profiles of electron bunch are analyzed by filling beam current in a single bunch mode. These studies are carried at injection energy (550 MeV) and at ramped beam energy (2.5 GeV). The effects of the wakefield generated interactions between the circulating electrons and the surrounding vacuum chamber are analyzed in terms of measured effects on longitudinal beam distribution. The impedance of the storage ring is obtained by fitting the solutions of Haissinski equation to the measured bunch lengthening with different impedance models. The impedance of storage ring obtained by a series R+L impedance model indicates a resistance (R) of 1350±125 Ω, an inductance (L) of 180±25 nH and broadband impedance of 2.69 Ω. These results are also compared with the values obtained from measured synchronous phase advancing and scaling laws. These studies are very useful in better understanding and control of the electromagnetic interactions.

  9. Shock wave interaction with interfaces between materials having different acoustic impedances

    NASA Astrophysics Data System (ADS)

    Hosseini, H.; Moosavi-Nejad, S.; Akiyama, H.; Menezes, V.

    2014-03-01

    We experimentally examined interaction of blast waves with water-air/air-water interfaces through high-speed-real-time visualization and measurement of pressure across the waves. The underwater shock wave, which was expected to reflect totally at the water-air interface, was observed transmitting a shock front to air. Transmission of a blast wave from air to water was also visualized and evaluated. Underwater shock waves are used in several medical/biological procedures, where such unforeseen transmissions can result in detriments. The details provide a guideline to evaluate blast wave transmissions, which can induce tissue and brain injuries. The results explain mechanisms behind blast-induced traumatic brain injury.

  10. Relation between near field and far field acoustic measurements

    NASA Technical Reports Server (NTRS)

    Bies, D. A.; Scharton, T. D.

    1974-01-01

    Several approaches to the problem of determining the far field directivity of an acoustic source located in a reverberant environment, such as a wind tunnel, are investigated analytically and experimentally. The decrease of sound pressure level with distance is illustrated; and the spatial extent of the hydrodynamic and geometric near fields, the far field, and the reverberant field are described. A previously-prosposed analytical technique for predicting the far field directivity of the acoustic source on the basis of near field data is investigated. Experiments are conducted with small acoustic sources and an analysis is performed to determine the variation with distance from the source of the directionality of the sound field. A novel experiment is conducted in which the sound pressure measured at various distances from an acoustic driver located in the NASA Ames 40 x 80 ft wind tunnel is crosscorrelated with the driver excitation voltage.

  11. In vivo measurement of mechanical impedance of bone

    NASA Technical Reports Server (NTRS)

    Young, D. R.; Thompson, G.

    1974-01-01

    System of measurement provides indications of ulnar properties independent of characteristics of surrounding soft tissue and other bones. Mechanical modal approximated ulnar response so average bending rigidity could be determined to provide direct index of bone resistance to bending loading.

  12. UNIVERSAL AUTO-CALIBRATION FOR A RAPID BATTERY IMPEDANCE SPECTRUM MEASUREMENT DEVICE

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; William H. Morrison

    2014-03-01

    Electrochemical impedance spectroscopy has been shown to be a valuable tool for diagnostics and prognostics of energy storage devices such as batteries and ultra-capacitors. Although measurements have been typically confined to laboratory environments, rapid impedance spectrum measurement techniques have been developed for on-line, embedded applications as well. The prototype hardware for the rapid technique has been validated using lithium-ion batteries, but issues with calibration had also been identified. A new, universal automatic calibration technique was developed to address the identified issues while also enabling a more simplified approach. A single, broad-frequency range is used to calibrate the system and then scaled to the actual range and conditions used when measuring a device under test. The range used for calibration must be broad relative to the expected measurement conditions for the scaling to be successful. Validation studies were performed by comparing the universal calibration approach with data acquired from targeted calibration ranges based on the expected range of performance for the device under test. First, a mid-level shunt range was used for calibration and used to measure devices with lower and higher impedance. Next, a high excitation current level was used for calibration, followed by measurements using lower currents. Finally, calibration was performed over a wide frequency range and used to measure test articles with a lower set of frequencies. In all cases, the universal calibration approach compared very well with results acquired following a targeted calibration. Additionally, the shunts used for the automated calibration technique were successfully characterized such that the rapid impedance measurements compare very well with laboratory-scale measurements. These data indicate that the universal approach can be successfully used for onboard rapid impedance spectra measurements for a broad set of test devices and range of

  13. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion.

    PubMed

    Bartholomew, Paul D; Guthrie, W Spencer; Mazzeo, Brian A

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  14. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion

    NASA Astrophysics Data System (ADS)

    Bartholomew, Paul D.; Guthrie, W. Spencer; Mazzeo, Brian A.

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  15. Measuring the Six dof Driving Point Impedance Function and AN Application to RB Inertia Property Estimation

    NASA Astrophysics Data System (ADS)

    Witter, M. C.; Brown, D. L.; Blough, J. R.

    2000-01-01

    An accurate driving point measurement is imperative in structural dynamic testing. For example, it is used to derive modal scaling, for experimental correlation of finite element models, impedance modelling and extracting the rigid body (RB) inertia properties of an object. A typical driving point measurement gives the linear force/displacement relationship at a single degree of freedom (dof), but any point on an object actually has rotational dofs as well. For example these rotational dofs must be measured in an impedance model where moments are transmitted at the connection point of two substructures. By ignoring the rotations, an inaccurate model will result. In the past, dynamic sensing technology has been limited to the accurate measurement of translational dofs. While rotational sensors do exist, their accuracy is called into question for certain applications. Rotational dofs have tended to be ignored in the measurement process. Applications, which require their use, such as impedance modelling and RB inertia property estimation, have suffered as a result. A process/sensor is being developed to accurately measure the driving point impedance function in all six dofs. The sensor as well as a calibration procedure will be presented here. In order to verify the validity of the calibration and measurement procedure, a new method for measuring the RB inertia properties of an object will be presented. This new method requires an accurate six dof driving point impedance measurement to provide accurate results. The inertia properties of an automotive brake rotor will be measured and compared with the results of a traditional pendulous swing test.

  16. Longitudinal impedance measurement of an RK-TBA induction accelerating gap

    SciTech Connect

    Eylon, S.; Henestroza, E.; Kim, J.-S.; Houck, T.L.; Westenskow, G.A.; Yu, S.S.

    1997-05-01

    Induction accelerating gap designs are being studied for Relativistic Klystron Two-Beam Accelerator (RK-TBA) applications. The accelerating gap has to satisfy the following major requirements: hold-off of the applied accelerating voltage pulse, low transverse impedance to limit beam breakup, low longitudinal impedance at the beam-modulation frequency to minimize power loss. Various gap geometries, materials and novel insulating techniques were explored to optimize the gap design. We report on the experimental effort to evaluate the rf properties of the accelerating gaps in a simple pillbox cavity structure. The experimental cavity setup was designed using the AMOS, MAFIA and URMEL numerical codes. Longitudinal impedance measurements above beam-tube cut-off frequency using a single-wire measuring system are presented.

  17. Broadband electrical impedance matching for piezoelectric ultrasound transducers.

    PubMed

    Huang, Haiying; Paramo, Daniel

    2011-12-01

    This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.

  18. Acoustic harmonic generation measurement applications: Detection of tight cracks in powder metallurgy compacts

    NASA Astrophysics Data System (ADS)

    Barnard, D. J.; Foley, J. C.

    2000-05-01

    Standard linear ultrasonic testing techniques have long been employed for locating and characterizing relatively open cracks in a wide variety of materials, from metallic alloys and ceramics to composites. In all these materials, the detection of open cracks easily accomplished because the void between the two crack surfaces provides sufficient acoustic impedance mismatch to reflect the incident energy. Closed or partially closed cracks, however, may often go undetected because contacting interfaces allow transmission of ultrasound. In the green (unsintered) state, powder metallurgy compacts typically contain high residual stresses that have the ability to close cracks formed during the compaction process, a result of oxide films, improper powder lubricant, mold design, etc. After sintering, the reduction of residual stresses may no longer be sufficient to close the crack. Although the crack may be more easily detected, it is obvious most desirable to discover defects prior to sintering. It has been shown that the displacements of an interface may be highly nonlinear if a stress wave of sufficient intensity propagates across it, a result of the stress wave either opening or closing the interface. Current efforts involve the application of nonlinear acoustic techniques, in particular acoustic harmonic generation measurements, for the detection and characterization of tightly closed cracks in powder metallurgy parts. A description of the equipment and the measurement technique will be discussed and initial experimental results on sintered and green compacts will be presented.—This work was performed at the Ames Laboratory, Iowa State University under USDOE Contract No. W-7405-ENG-82.

  19. An Electronic Measurement Instrumentation of the Impedance of a Loaded Fuel Cell or Battery

    PubMed Central

    Aglzim, El-Hassane; Rouane, Amar; El-Moznine, Reddad

    2007-01-01

    In this paper we present an inexpensive electronic measurement instrumentation developed in our laboratory, to measure and plot the impedance of a loaded fuel cell or battery. Impedance measurements were taken by using the load modulation method. This instrumentation has been developed around a VXI system stand which controls electronic cards. Software under Hpvee® was developed for automatic measurements and the layout of the impedance of the fuel cell on load. The measurement environment, like the ambient temperature, the fuel cell temperature, the level of the hydrogen, etc…, were taken with several sensors that enable us to control the measurement. To filter the noise and the influence of the 50Hz, we have implemented a synchronous detection which filters in a very narrow way around the useful signal. The theoretical result obtained by a simulation under Pspice® of the method used consolidates the choice of this method and the possibility of obtaining correct and exploitable results. The experimental results are preliminary results on a 12V vehicle battery, having an inrush current of 330A and a capacity of 40Ah (impedance measurements on a fuel cell are in progress, and will be the subject of a forthcoming paper). The results were plotted at various nominal voltages of the battery (12.7V, 10V, 8V and 5V) and with two imposed currents (0.6A and 4A). The Nyquist diagram resulting from the experimental data enable us to show an influence of the load of the battery on its internal impedance. The similitude in the graph form and in order of magnitude of the values obtained (both theoretical and practical) enables us to validate our electronic measurement instrumentation. One of the future uses for this instrumentation is to integrate it with several control sensors, on a vehicle as an embedded system to monitor the degradation of fuel cell membranes.

  20. On acoustic intensity measurements in the presence of mean flow

    NASA Technical Reports Server (NTRS)

    Munro, D. H.; Ingard, K. U.

    1979-01-01

    A theoretical analysis demonstrates that the technique of measuring acoustic intensity by means of cross correlation between nearby microphones cannot, in general, be extended to situations in which there is mean flow. However, it may be possible to use this technique to measure intensities in ducts with mean flow at frequencies below their cutoff frequencies.

  1. Approach to Eliminate Couplant-Effect in Acoustic Nonlinearity Measurements

    SciTech Connect

    Sun, L.; Kulkarni, S. S.; Achenbach, J. D.; Krishnaswamy, S.

    2006-03-06

    An approach to eliminate couplant-effect in acoustic nonlinearity measurements for fatigued components is proposed in this paper. Measurements are performed on a fatigued steel 4340 specimen using both the conventional and proposed techniques. It is observed that the coefficients of variation of the nonlinearity parameter obtained using the proposed technique is approximately half of that obtained using the conventional technique.

  2. Piezo-sensor self-diagnostics using electrical impedance measurements.

    SciTech Connect

    Park, G. H.; Farrar, C. R.; Rutherford, A. C.; Robertson, A. N.

    2004-01-01

    This paper present the piezoelectric sensor self-diagnostic procedure that performs in-situ monitoring of the operational status of piezoelectric materials (PZT) used for sensors and actuators in structural health monitoring (SHM) applications. The use of active-sensing piezoelectric materials has received considerable attention in the SHM community. A critical aspect of the piezoelectric active-sensing technologies is that usually large numbers of distributed sensors and actuators are needed to perform the required monitoring process. The sensor/actuator self-diagnostic procedure, where the sensors/actuators are confirmed to be functioning properly during operation, is therefore a critical component to successfully complete the SHM process and to minimize the false indication regarding the structural health. The basis of this procedure is to track the changes in the capacitive value of piezoelectric materials resulting from the sensor failure, which is manifested in the imaginary part of the measured electrical admittances. Furthermore, through the analytical and experimental investigation, it is confirmed that the bonding layer between the PZT and a host structure significantly contributes to the measured capacitive values. Therefore, by monitoring the imaginary part of the admittances, one can quantitatively assess the degradation of the mechanical/electrical properties of the PZT and its attachment to a host structure. This paper concludes with an experimental example to demonstrate the feasibility of the proposed sensor-diagnostic procedure.

  3. Tissue electrical properties measured by bioelectrical impedance analysis among healthy and sportsmen population

    NASA Astrophysics Data System (ADS)

    Kapica, Dominik; Warchulińska, Joanna; Jakubiak, Monika; Teter, Mariusz; Mlak, Radosław; Hałabiś, Magdalena; Wójcik, Waldemar; Małecka-Massalska, Teresa

    2015-09-01

    Introduction: Bioelectrical impedance analysis (BIA) is a useful tool to asses human body composition and nutrition status; multi-frequency BIA has a higher accuracy than single-frequency BIA. In our study a difference of impedance values (Z) at 5, 100 and 200 kHz and Z200/Z5 index between professional athletes and control group were determined. Methods: In this research 105 people were tested, divided into control group (72 people: 35 males and 37 females) and professional athletes (33 people: 16 males and 17 females). Impedance was measured at three frequency values - 5, 100 and 200 kHz; with received values the Z200/Z5 index was calculated. Results: In most compared subgroups impedance values showed significantly lower values in athletes than in control group (5 kHz - males: p=0.136, females: p=0.001, 100 kHz - males: p=0.039, females: p<0.0001, 200 kHz - males: p=0.047, females: p<0.0001) Z200/Z5 index also showed lower value in athletes than in control group (p=0.016 for males, p<0.0001 for females). Conclusion: Lower values of impedance and Z200/Z5 index indicates a better nutrition status and general health condition of athletes than in control group.

  4. Tissue type determination by impedance measurement: A bipolar and monopolar comparison

    PubMed Central

    Sharp, Jack; Bouazza-Marouf, Kaddour; Noronha, Dorita; Gaur, Atul

    2017-01-01

    Background: In certain medical applications, it is necessary to be able to determine the position of a needle inside the body, specifically with regards to identifying certain tissue types. By measuring the electrical impedance of specific tissue types, it is possible to determine the type of tissue the tip of the needle (or probe) is at. Materials and Methods: Two methods have been investigated for electric impedance detection; bipolar and monopolar. Commercially available needle electrodes are of a monopolar type. Although many patents exist on the bipolar setups, these have not as yet been commercialized. This paper reports a comparison of monopolar and bipolar setups for tissue type determination. In vitro experiments were carried out on pork to compare this investigation with other investigations in this field. Results: The results show that both monopolar and bipolar setups are capable of determining tissue type. However, the bipolar setup showed slightly better results; the difference between the different soft tissue type impedances was greater compared to the monopolar method. Conclusion: Both monopolar and bipolar electrical impedance setups work very similarly in inhomogeneous volumes such as biological tissue. There is a clear potential for clinical applications with impedance-based needle guidance, with both the monopolar and bipolar setups. It is, however, worth noting that the bipolar setup is more versatile. PMID:28217047

  5. Electrode-Skin contact impedance: In vivo measurements on an ovine model

    NASA Astrophysics Data System (ADS)

    Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Jin, C.; Oh, T. I.; Thiagalingam, A.; McEwan, A.

    2013-04-01

    The problem of electrical impedance between the skin and the electrode is an on-going challenge in bio-electronics. This is particularly true in the case of Electrical Impedance Tomography (EIT), which uses a large number of skin-contact electrodes and is very sensitive to noise. In the present article, contact impedance is measured and compared for a range of electrodes placed on the thorax of an ovine model. The study has been approved by the Westmead Hospital Animal Ethics Committee. The electrode models that were employed in the research are Ag/AgCl electrodes (E1), commonly used for ECG and EIT measurements in both humans and animal models, stainless steel crocodile clips (E2), typically used on animal models, and novel multi-point dry electrodes in two modifications: bronze plated (E3) and nickel plated (E4). Further, since the contact impedance is mostly attributed to the acellular outer layer of the skin, in our experiment, we attempted to study the effect of this layer by comparing the results when the skin is intact and when electrodes are introduced underneath the skin through small cuts. This boundary effect was assessed by comparison of measurements obtained during E2 skin surface contact, and sub-cutaneous contact (E5). Twelve gauge intradermal needles were also tested as an electrode (E6). The full impedance spectrum, from 500 Hz to 300 kHz, was recorded, analysed and compared. As expected, the contact impedance in the more invasive cases, i.e the electrodes under the skin, is significantly lower than in the non-invasive cases. At the frequency of 50 kHz which is commonly used in lung EIT acquisition, electrodes E3, E4 and E6 demonstrated contact impedance of less than 200 Ω, compared to more than 400 Ω measured for electrodes E1, E2 and E5. In conclusion, the novel multipoint electrodes proved to be best suited for EIT purposes, because they are non-invasive and have lower contact impedance than Ag/AgCl and crocodile clips, in both invasive and

  6. Acoustic measurement study 40 by 80 foot subsonic wind tunnel

    NASA Technical Reports Server (NTRS)

    1974-01-01

    An acoustical study conducted during the period from September 1, 1973 to April 30, 1974 measured sound pressure levels and vibration amplitudes inside and outside of the subsonic tunnel and on the tunnel structure. A discussion of the technical aspects of the study, the field measurement and data reduction procedures, and results are presentd, and conclusions resulting from the study which bear upon near field and far field tunnel noise, upon the tunnel as an acoustical enclosure, and upon the sources of noise within the tunnel drive system are given.

  7. An optoacoustic point source for acoustic scale model measurements.

    PubMed

    Bolaños, Javier Gómez; Pulkki, Ville; Karppinen, Pasi; Hæggström, Edward

    2013-04-01

    A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

  8. Non-Contact Measurement of the Electrical Impedance of Biological Tissue

    DTIC Science & Technology

    2007-11-02

    NON-CONTACT MEASUREMENT OF THE ELECTRICAL IMPEDANCE OF BIOLOGICAL TISSUE C.H. Riedel and O.Dössel Institute of Biomedical Engineering, Universität...currents. Keywords—contact-free measurement, electrical im- pedance, coil systems I. Introduction The non-invasive method of measuring the impe- dance...can give information of the electrical characte- ristics of tissue. In some cases the conductivity gra- dient can be an important value. The

  9. Measurement of Peak Esophageal Luminal Cross Sectional Area Utilizing Nadir Intraluminal Impedance

    PubMed Central

    Zifan, Ali; Ledgerwood-Lee, Melissa; Mittal, Ravinder K

    2015-01-01

    BACKGROUND Multichannel intraluminal impedance (MII) is currently used to monitor gastroesophageal reflux and esophageal bolus clearance. We describe a novel methodology to measure maximal luminal CSA during bolus transport from MII measurements. METHODS Studies were conducted in-vitro (test tubes) and in-vivo (healthy subjects). Concurrent MII, HRM, and intraluminal ultrasound (US) were recorded 7 cm above the lower esophageal sphincter. Swallows with two concentrations of saline, 0.1N and 0.5N, of bolus volumes 5cc, 10cc and 15cc were performed. The CSA was estimated by solving two algebraic Ohm’s law equations, resulting from the two saline solutions. The CSA calculated from impedance method was compared with the CSA measured from the intraluminal US images. KEY RESULTS The CSA measured in duplicate from B-mode US images showed a mean difference between the two manual delineations to be near zero, and the repeatability coefficient was within 7.7% of the mean of the two CSA measurements. The calculated CSA from the impedance measurements strongly correlated with the US measured CSA (R2 ≅ 0.98). A detailed statistical analysis of the impedance and US measured CSA data indicated that the 95% limits of agreement between the two methods ranged from −9.1 to 13mm2. The root mean square error (RMS) of the two measurements was 4.8% of the mean US-measured CSA. CONCLUSIONS We describe a novel methodology to measure peak esophageal luminal CSA during peristalsis. Further studies are needed to determine if it is possible to measure patterns of luminal distension during peristalsis across the entire length of the esophagus. PMID:25930157

  10. Bench-Top Impedance Measurements for a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade

    SciTech Connect

    Smith, Jeffrey Claiborne; Bane, Karl; Doyle, Eric; Keller, Lew; Lundgren, Steve; Markiewicz, Tom; Ng, Cho-Kuen; Xiao, Liling; /SLAC

    2010-08-26

    Simulations have been performed in Omega3P to study both trapped modes and impedance contributions of a rotatable collimator for the LHC phase II collimation upgrade. Bench-top stretched coil probe impedance methods are also being implemented for measurements on prototype components to directly measure the low frequency impedance contributions. The collimator design also calls for a RF contact interface at both jaw ends with contact resistance much less than a milliohm in order to limit transverse impedance. DC resistance measurements in a custom built test chamber have been performed to test the performance of this interface.

  11. End tidal carbon dioxide measurement using an electro acoustic sensor.

    PubMed

    Folke, M; Hok, B; Ekstrom, M; Backlund, Y

    2004-01-01

    End tidal carbon dioxide measurement with an electro-acoustic sensor is demonstrated. The sensor consists of an acoustic resonator coupled to a low cost electro-acoustic element. By simultaneous measurements with a reference sensor, the new device was tested on subjects performing exercise, hypo- and hyperventilation whereby the CO2concentration ranged from 2.1 to 7.0 kPa. The output from the experimental device correlated well with the reference CO2readings with a correlation coefficient of 0.976. Response time for expiration less than 0.8 seconds was noted. The new device could be useful in situations where selectivity to other gases is not important.

  12. Error correction algorithm for high accuracy bio-impedance measurement in wearable healthcare applications.

    PubMed

    Kubendran, Rajkumar; Lee, Seulki; Mitra, Srinjoy; Yazicioglu, Refet Firat

    2014-04-01

    Implantable and ambulatory measurement of physiological signals such as Bio-impedance using miniature biomedical devices needs careful tradeoff between limited power budget, measurement accuracy and complexity of implementation. This paper addresses this tradeoff through an extensive analysis of different stimulation and demodulation techniques for accurate Bio-impedance measurement. Three cases are considered for rigorous analysis of a generic impedance model, with multiple poles, which is stimulated using a square/sinusoidal current and demodulated using square/sinusoidal clock. For each case, the error in determining pole parameters (resistance and capacitance) is derived and compared. An error correction algorithm is proposed for square wave demodulation which reduces the peak estimation error from 9.3% to 1.3% for a simple tissue model. Simulation results in Matlab using ideal RC values show an average accuracy of for single pole and for two pole RC networks. Measurements using ideal components for a single pole model gives an overall and readings from saline phantom solution (primarily resistive) gives an . A Figure of Merit is derived based on ability to accurately resolve multiple poles in unknown impedance with minimal measurement points per decade, for given frequency range and supply current budget. This analysis is used to arrive at an optimal tradeoff between accuracy and power. Results indicate that the algorithm is generic and can be used for any application that involves resolving poles of an unknown impedance. It can be implemented as a post-processing technique for error correction or even incorporated into wearable signal monitoring ICs.

  13. Method and device for bio-impedance measurement with hard-tissue applications.

    PubMed

    Guimerà, A; Calderón, E; Los, P; Christie, A M

    2008-06-01

    Bio-impedance measurements can be used to detect and monitor several properties of living hard-tissues, some of which include bone mineral density, bone fracture healing or dental caries detection. In this paper a simple method and hardware architecture for hard tissue bio-impedance measurement is proposed. The key design aspects of such architecture are discussed and a commercial handheld ac impedance device is presented that is fully certified to international medical standards. It includes a 4-channel multiplexer and is capable of measuring impedances from 10 kOmega to 10 MOmega across a frequency range of 100 Hz to 100 kHz with a maximum error of 5%. The device incorporates several user interface methods and a Bluetooth link for bi-directional wireless data transfer. Low-power design techniques have been implemented, ensuring the device exceeds 8 h of continuous use. Finally, bench test results using dummy cells consisting of parallel connected resistors and capacitors, from 10 kOmega to 10 MOmega and from 20 pF to 100 pF, are discussed.

  14. End-point impedance measurements across dominant and nondominant hands and robotic assistance with directional damping.

    PubMed

    Erden, Mustafa Suphi; Billard, Aude

    2015-06-01

    The goal of this paper is to perform end-point impedance measurements across dominant and nondominant hands while doing airbrush painting and to use the results for developing a robotic assistance scheme. We study airbrush painting because it resembles in many ways manual welding, a standard industrial task. The experiments are performed with the 7 degrees of freedom KUKA lightweight robot arm. The robot is controlled in admittance using a force sensor attached at the end-point, so as to act as a free-mass and be passively guided by the human. For impedance measurements, a set of nine subjects perform 12 repetitions of airbrush painting, drawing a straight-line on a cartoon horizontally placed on a table, while passively moving the airbrush mounted on the robot's end-point. We measure hand impedance during the painting task by generating sudden and brief external forces with the robot. The results show that on average the dominant hand displays larger impedance than the nondominant in the directions perpendicular to the painting line. We find the most significant difference in the damping values in these directions. Based on this observation, we develop a "directional damping" scheme for robotic assistance and conduct a pilot study with 12 subjects to contrast airbrush painting with and without robotic assistance. Results show significant improvement in precision with both dominant and nondominant hands when using robotic assistance.

  15. Measurement of respiratory impedance by impulse oscillometry--effects of endotracheal tubes.

    PubMed

    Kuhnle, G E; Brandt, T; Roth, U; Goetz, A E; Smith, H J; Peter, K

    2000-12-01

    Impulse Oscillometry is a new, noninvasive method to measure respiratory impedance, i.e. airway resistance and reactance at different oscillation frequencies. These parameters are potentially useful for the monitoring of respiratory mechanics in the critically ill patent with respiratory dysfunction. The endotracheal tube, used to mechanically ventilate these patients, however, represents an additional nonlinear impedance that introduces artifacts into the measurements. The objective of this work was therefore to investigate the effects of clinically available endotracheal tubes on resistance and reactance of an in vitro analogue of the respiratory system. Additionally, the effects of decreasing the compressible gas volume in this experimental model, as a simulation of decreased lung capacity and compliance, was investigated. Impulse oscillometric measurements of the test analogue gave highly reproducible results with and without an endotracheal tube. The tubes had significant influence on the measurement of the test object at all frequencies investigated. Changes of low frequent reactance were negligible - at least if repetitive measurements of the same system are performed - for realistic measurement of airway resistance, a correction of the tube impedance or measurement of the pressure distal of the tube is required. Resistance increased and low frequent reactance decreased significantly with decreasing gas volume. These changes were of magnitudes higher than the variations due to the introduction of the endotracheal tubes. Our results suggest that changes of respiratory reactance measured with impulse oscillometry may be used as a monitoring parameter in intubated patients.

  16. Measurements of Middle Ear Pressure Gain and Cochlear Input Impedance in the Chinchilla

    NASA Astrophysics Data System (ADS)

    Slama, Michael C. C.; Ravicz, Michael E.; Nakajima, Hideko H.; Dong, Wei; Rosowski, John J.

    2009-02-01

    Measurements of middle ear conducted sound pressure in the cochlear vestibule PV have been performed in only a few species. Simultaneous measurements of sound-induced stapes velocity Vs are even more rare. We report simultaneous measurements of VS and PV in chinchillas. The VS measurements are performed using single-beam laser-Doppler vibrometry; PV is measured with fiber-optic pressure sensors like those described by Olson [1]. PV and VS have been measured in six animals, and the middle ear pressure gain (ratio of PV to the sound pressure in the ear canal) and the cochlear input impedance (ratio of PV to the product of VS and area of the footplate) computed. Our measurements of middle ear pressure gain are similar to published data in the chinchilla at stimulus frequencies of 500 Hz to 3 kHz, but are different at other frequencies. Our measurements of cochlear input impedance differ somewhat from previous estimates in the chinchilla and show a resistive input impedance up to at least 10 kHz.

  17. Measurement of Plasma Clotting Using Shear Horizontal Surface Acoustic Wave Sensor

    NASA Astrophysics Data System (ADS)

    Nagayama, Tatsuya; Kondoh, Jun; Oonishi, Tomoko; Hosokawa, Kazuya

    2013-07-01

    The monitoring of blood coagulation is important during operation. In this study, a shear horizontal surface acoustic wave (SH-SAW) sensor is applied to monitor plasma clotting. An SH-SAW sensor with a metallized surface for mechanical perturbation detection can detect plasma clotting. As plasma clotting is a gel formation reaction, the SH-SAW sensor detects viscoelastic property changes. On the other hand, an SH-SAW sensor with a free surface for electrical perturbation detection detects only the liquid mixing effect. No electrical property changes due to plasma clotting are obtained using this sensor. A planar electrochemical sensor is also used to monitor plasma clotting. In impedance spectral analysis, plasma clotting is measured. However, in the measurement of time responses, no differences between clotting and nonclotting are obtained. Therefore, the SH-SAW sensor is useful for monitoring plasma clotting.

  18. Comparison of impedance cardiography and dye dilution method for measuring cardiac output

    PubMed Central

    Spiering, W; van Es, P N; de Leeuw, P W

    1998-01-01

    Objective—To assess the degree of agreement between impedance cardiography, using the NCCOM3-R7 device, and the gold standard—the dye dilution method—both under basal conditions and after stimulation of cardiac output.
Patients—35 paired measurements in five healthy male volunteers.
Interventions—To obtain higher levels of cardiac output, cardiac performance was stimulated with a dopamine infusion.
Results—In 35 paired measurements, the mean of all the impedance values was higher than that of the dye dilution values, at 10.2 v 7.4 l/min (p < 0.0001). The mean discrepancy between the two methods was 3.3 l/min, and the mean bias −2.9 l/min, with limits of agreement of −9.0 and 3.2 l/min. A change in cardiac output could not adequately be predicted by the NCCOM3-R7. In 20 of 25 measurements obtained during continuous intravenous dopamine infusions there was a rise in dye dilution cardiac output (range 0.2 to 5.9 l/min). Neither the magnitude nor the direction of the change in dye dilution values corresponded with the change measured by impedance cardiography. The mean discrepancy here between the two methods was 1.8 l/min, and the mean bias −0.8 l/min, with limits of agreement of −4.9 and 3.3 l/min.
Conclusions—In healthy volunteers, impedance cardiography with NCCOM3-R7 is inadequate for assessing cardiac output when compared with the dye dilution method.

 Keywords: cardiac output;  impedance cardiography;  dye dilution PMID:9659188

  19. Wire Measurement of Impedance of an X-Band Accelerating Structure

    SciTech Connect

    Baboi, N

    2004-09-02

    Several tens of thousands of accelerator structures will be needed for the next generation of normal conducting linear colliders known as the GLC/NLC (Global Linear Collider/Next Linear Collider). To prevent the beam being driven into a disruptive BBU (Beam Break-Up) mode or at the very least, the emittance being significantly diluted, it is important to damp down the wakefield left by driving bunches to a manageable level. Manufacturing errors and errors in design need to be measured and compared with prediction. In this paper a bench-top method of measuring transverse impedances in X-band accelerating structures is described. Utilizing an off-axis wire the S parameters are measured and converted to impedance. Measurements in a damped and detuned structure built for GLC/NLC are presented and the results are discussed.

  20. Battery-powered portable instrument system for single-cell trapping, impedance measurements, and modeling analyses.

    PubMed

    Tsai, Sung-Lin; Chiang, Yang; Wang, Min-Haw; Chen, Ming-Kun; Jang, Ling-Sheng

    2014-08-01

    A battery-powered portable instrument system for the single-HeLa-cell trapping and analyses is developed. A method of alternating current electrothermal (ACET) and DEP are employed for the cell trapping and the method of impedance spectroscopy is employed for cell characterizations. The proposed instrument (160 mm × 170 mm × 110 mm, 1269 g) equips with a highly efficient energy-saving design that promises approximately 120 h of use. It includes an impedance analyzer performing an excitation voltage of 0.2-2 Vpp and a frequency sweep of 11-101 kHz, function generator with the sine wave output at an operating voltage of 1-50 Vpp with a frequency of 4-12 MHz, cell-trapping biochip, microscope, and input/output interface. The biochip for the single cell trapping is designed and simulated based on a combination of ACET and DEP forces. In order to improve measurement accuracy, the curve fitting method is adopted to calibrate the proposed impedance spectroscopy. Measurement results from the proposed system are compared with results from a precision impedance analyzer. The trapped cell can be modeled for numerical analyses. Many advantages are offered in the proposed instrument such as the small volume, real-time monitoring, rapid analysis, low cost, low-power consumption, and portable application.

  1. Interpulse multifrequency electrical impedance measurements during electroporation of adherent differentiated myotubes.

    PubMed

    García-Sánchez, Tomás; Azan, Antoine; Leray, Isabelle; Rosell-Ferrer, Javier; Bragós, Ramon; Mir, Lluis M

    2015-10-01

    In this study, electrical impedance spectroscopy measurements are performed during electroporation of monolayers of differentiated myotubes. The time resolution of the system (1 spectrum/ms) enable 860 full spectra (21 frequencies from 5 kHz to 1.3 MHz) to be acquired during the time gap between consecutive pulses (interpulse) of a classical electroporation treatment (8 pulses, 100 μs, 1 Hz). Additionally, the characteristics of the custom microelectrode assembly used allow the experiments to be performed directly in situ in standard 24 multi-well plates. The impedance response dynamics are studied for three different electric field intensities (400, 800 and 1200 V/cm). The multifrequency information, analysed with the Cole model, reveals a short-term impedance recovery after each pulse in accordance with the fast resealing of the cell membrane, and a long-term impedance decay over the complete treatment in accordance with an accumulated effect pulse after pulse. The analysis shows differences between the lowest electric field condition and the other two, suggesting that different mechanisms that may be related with the reversibility of the process are activated. As a result of the multifrequency information, the system is able to measure simultaneously the conductivity variations due to ion diffusion during electroporation. Finally, in order to reinforce the physical interpretation of the results, a complementary electrical equivalent model is used.

  2. Advances in non-invasive measures of vocal acoustics.

    PubMed

    LaBlance, G R; Steckol, K F; Cooper, M H

    1991-10-01

    Objective assessment of vocal pitch, loudness, and quality is a crucial adjunct to endoscopy in the diagnosis and treatment of vocal pathology. Historically, this assessment was made through subjective, perceptual measures that were questionable in terms of validity and reliability. Recent advances in electronic technology now permit objective analysis of the acoustic characteristics of voice. Kay Elemetric's Visi-Pitch, DSP 5500 Digital Spectrograph, and Nasometer are representative of these new instruments and are used as illustrations in the discussion of the assessment of speech acoustics.

  3. Acoustic ship signature measurements by cross-correlation method.

    PubMed

    Fillinger, Laurent; Sutin, Alexander; Sedunov, Alexander

    2011-02-01

    Cross-correlation methods were applied for the estimation of the power spectral density and modulation spectrum of underwater noise generated by moving vessels. The cross-correlation of the signal from two hydrophones allows the separation of vessel acoustic signatures in a busy estuary. Experimental data recorded in the Hudson River are used for demonstration that cross-correlation method measured the same ship noise and ship noise modulation spectra as conventional methods. The cross-correlation method was then applied for the separation of the acoustic signatures of two ships present simultaneously. Presented methods can be useful for ship traffic monitoring and small ship classification, even in noisy harbor environments.

  4. High-frequency attenuation measurements using an acoustic microscope.

    PubMed

    Gracewski, S M; Waag, R C; Schenk, E A

    1988-06-01

    An acoustic microscope was used to measure excess attenuation of aqueous solutions of sugars and proteins at 1.0 GHz. Interference pattern spacing and peak amplitude reduction of V(z) curves, obtained with these solutions as the acoustic microscope coupling liquid, were related to the solution wavespeed and attenuation, respectively. Consistent with published results for lower frequencies, solutions with molecular weight greater than 10,000 had a higher specific absorption than those with a molecular weight less than 1000 and within these two molecular weight ranges specific absorption was independent of concentration.

  5. A Comparative Study of Two Acoustic Measures of Hypernasality

    ERIC Educational Resources Information Center

    Vogel, Adam P.; Ibrahim, Hasherah M.; Reilly, Sheena; Kilpatrick, Nicky

    2009-01-01

    Purpose: This study aimed to compare 2 quantitative acoustic measures of nasality in children with cleft lip and palate (CLP) and healthy controls using formalized perceptual assessment as a guide. Method: Fifty participants (23 children with CLP and 27 age- and gender-matched healthy controls) aged between 4 and 12 years produced a variety of…

  6. Measuring acoustic properties of materials and jet nozzles

    NASA Technical Reports Server (NTRS)

    Dean, P. D.; Plumblee, H. E.; Salikuddin, M.

    1980-01-01

    Method measures acoustic properties of sound-absorbent materials and jet-nozzle system. Advantages of impulse method over other methods are that test time and complication are reduced. Results obtained from impulse method have been compared with those from existing methods, both experimental and theoretical, and show excellent agreement.

  7. Measurement of the total acoustic output power of HITU transducers

    NASA Astrophysics Data System (ADS)

    Jenderka, Klaus-V.; Beissner, Klaus

    2010-03-01

    The majority of High Intensity Therapeutic Ultrasound (HITU) applications use strongly focused ultrasound fields generating very high local intensities in the focal region. The metrology of these high-power ultrasound fields is a challenge for the established measurement procedures and devices. This paper describes the results of measurements by means of the radiation force for a total acoustic output power up to 400 W at 1.5 MHz and up to 200 W at 2.45 MHz. For this purpose, a radiation force balance set-up was adapted for the determination of large acoustic output powers. For two types of HITU transducers, the relationship between the total acoustic output power and the applied net electrical power was determined at close transducer-target distance. Further, dependence of the measured electro-acoustic radiation conductance on the transducer-target distance was investigated at reduced power levels, considering the appearance of focal anomalies. Concluding, a list of the main uncertainty contributions, and an estimate of the uncertainty for the used radiation force balance set-up is given for measurements at high power levels.

  8. Laboratory comparisons of acoustic and optical sensors for microbubble measurement

    NASA Technical Reports Server (NTRS)

    Su, Ming Yang; Todoroff, Douglas; Cartmill, John

    1994-01-01

    This paper presents the results of a recent comparison between three microbubble size spectrum measurement systems. These systems are the light-scattering bubble counter, the photographic bubble-imaging system, and the acoustic resonator array. Good agreement was formed among these three systems over the bubble size range appropriate for each system.

  9. Voice Acoustical Measurement of the Severity of Major Depression

    ERIC Educational Resources Information Center

    Cannizzaro, Michael; Harel, Brian; Reilly, Nicole; Chappell, Phillip; Snyder, Peter J.

    2004-01-01

    A number of empirical studies have documented the relationship between quantifiable and objective acoustical measures of voice and speech, and clinical subjective ratings of severity of Major Depression. To further explore this relationship, speech samples were extracted from videotape recordings of structured interviews made during the…

  10. Impedance Measurements as a Tool for the Detection of Endocrine Disrupting Chemicals

    DTIC Science & Technology

    2007-11-02

    endocrine disruptors on human health has created a need for screening systems to detect xenoestrogens, a diverse group of chemicals that mimic...Impedance Measurements as a Tool for the Detection of Endocrine Disrupting Chemicals V. Sacks, J. Rishpon* Department of Molecular...sensitive and amenable to use on-site, providing an efficient and economic tool for measuring minuscule amounts of endocrine disrupting chemicals

  11. Measurement of acoustic shielding by a turbulent jet

    NASA Technical Reports Server (NTRS)

    Yu, J. C.; Fratello, D. J.

    1985-01-01

    The acoustic shielding properties of a turbulent jet have been investigated experimentally. The experimental arrangement consisted of an acoustic point source and a turbulent shielding jet. The source and jet parameters investigated include the source frequency, source spectrum, jet velocity, jet heating by simulation and the lateral and longitudinal source positions with respect to the shielding jet. It is found that the maximum sound attenuation provided by the shielding jet depends on the balance between refraction and diffraction. Over the frequency range investigated, the redistribution of sound by the shielding air jet is power conserving. Comparison between measurement and prediction based on an idealized cylindrical uniform jet model indicates that the spreading and decay of the flow field in real jets are important. Comparisons between the present data trends and those reported for jet-by-jet shielding suggest that the major effects observed in the latter are acoustical rather than aerodynamical.

  12. Acoustic measurements of air entrainment by breaking waves

    NASA Astrophysics Data System (ADS)

    Terrill, Eric James

    1998-11-01

    Wave breaking at the surface of the ocean plays an important role in air-sea interaction processes. Bubbles entrained by breaking waves not only enhance the transfer of atmospheric gases to the ocean, but also modify the phase speed and attenuation of acoustic waves propagating through the bubbly medium. The development of acoustic instruments to measure bubbles and the results obtained from a number of field and laboratory experiments are presented. The first part of this dissertation addresses sound speed measurements made in the North Atlantic as part of the Acoustic Surface Reverberation Experiment (ASREX). An autonomous buoy system that directly measures the sound speed in the surface wave layer was developed. Data obtained with the instrument spanned several storm cycles with wind speeds and significant wave heights reaching 20 m/s and 8 m, respectively. The use of Wood's relation (1946) allows the calculation of the void fraction of air based on the low-frequency sound speed measurements. The highly variable near-surface sound speed/void fraction field is analyzed with respect to wind and surface wave- breaking parameters. The second part of this dissertation presents the development of a broadband acoustic technique which simultaneously measures the phase speed and attenuation at acoustic frequencies ranging from 4-100 kHz. The acoustic data is inverted for the size distribution of bubbles using algorithms that are based upon the physics of sound propagation through a bubbly mixture. This acoustic technique was evaluated in the large wave channel at the Hydraulics Laboratory, Scripps Institution of Oceanography, using mechanically generated breaking waves in seawater. Field measurements of bubble concentrations that result from wave breaking were made in both shallow water off Scripps Pier, California and in deep water near Point Conception, California using the broadband technique. Significant variability is observed in the bubble field, characterized by

  13. Electrical impedance string probes for two-phase void and velocity measurements. [PWR

    SciTech Connect

    Hardy, J E; Hylton, J O

    1982-05-01

    An instrumentation scheme has been developed to measure two-phase flow velocity and void fraction during the refill/reflood stages of a loss-of-coolant accident in experimental test facilities. The instrumentation's principle of operation was based on measurement of the electrical impedance of two-phase mixtures. Two-phase velocity is estimated by time-of-flight analysis of signals from two spatially separate sensors. A relative capacitive technique was employed to measure void fraction. The impedance sensor consists of a pair of stainless steel wires strung back and forth across a stainless steel frame. This sensor was dubbed string probe for this reason. The string probe was designed to withstand temperatures of 350/sup 0/C, thermal transients of approx. 300/sup 0/C/s, and severe fluid- and condensation-induced shocks.

  14. A compact wideband precision impedance measurement system based on digital auto-balancing bridge

    NASA Astrophysics Data System (ADS)

    Hu, Binxin; Wang, Jinyu; Song, Guangdong; Zhang, Faxiang

    2016-05-01

    The ac impedance spectroscopy measurements are predominantly taken by using impedance analyzers based on analog auto-balancing bridge. However, those bench-top analyzers are generally complicated, bulky and expensive, thus limiting their usage in industrial field applications. This paper presents the development of a compact wideband precision measurement system based on digital auto-balancing bridge. The methods of digital auto-balancing bridge and digital lock-in amplifier are analyzed theoretically. The overall design and several key sections including null detector, direct digital synthesizer-based sampling clock, and digital control unit are introduced in detail. The results show that the system achieves a basic measurement accuracy of 0.05% with a frequency range of 20 Hz-2 MHz. The advantages of versatile measurement capacity, fast measurement speed, small size and low cost make it quite suitable for industrial field applications. It is demonstrated that this system is practical and effective by applying in determining the impedance-temperature characteristic of a motor starter PTC thermistor.

  15. New Opportunities for Fracture Healing Detection: Impedance Spectroscopy Measurements Correlate to Tissue Composition in Fractures.

    PubMed

    Lin, Monica C; Yang, Frank; Herfat, Safa T; Bahney, Chelsea S; Marmor, Meir; Maharbiz, Michel M

    2017-04-06

    Accurate evaluation of fracture healing is important for clinical decisions on when to begin weight-bearing and when early intervention is necessary in cases of fracture nonunion. While the stages of healing involving hematoma, cartilage, trabecular bone, and cortical bone have been well characterized histologically, physicians typically track fracture healing by using subjective physical examinations and radiographic techniques that are only able to detect mineralized stages of bone healing. This exposes the need for a quantitative, reliable technique to monitor fracture healing, and particularly to track healing progression during the early stages of repair. The goal of this study was to validate the use of impedance spectroscopy to monitor fracture healing and perform comprehensive evaluation comparing measurements with histological evidence. Here we show that impedance spectroscopy not only can distinguish between cadaver tissues involved throughout fracture repair, but also correlates to fracture callus composition over the middle stages of healing in wild-type C57BL/6 mice. Specifically, impedance magnitude has a positive relationship with % trabecular bone and a negative relationship with % cartilage, and the opposite relationships are found when comparing phase angle to these same volume fractions of tissues. With this information, we can quantitatively evaluate how far a fracture has progressed through the healing stages. Our results demonstrate the feasibility of impedance spectroscopy for detection of fracture callus composition and reveals its potential as a method for early detection of bone healing and fracture nonunion. This article is protected by copyright. All rights reserved.

  16. Studies of acoustical properties of bulk porous flexible materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1984-01-01

    Acoustic prediction and measurement of bulk porous materials with flexible frames is investigated. The acoustic properties of Kevlar 29 are examined. Various acoustic tests are employed to determine impedance, sound wave propagation, and wave pressure equations for the highly porous fiber composites. The derivation of design equations and future research goals are included.

  17. TECHNICAL NOTE: Portable audio electronics for impedance-based measurements in microfluidics

    NASA Astrophysics Data System (ADS)

    Wood, Paul; Sinton, David

    2010-08-01

    We demonstrate the use of audio electronics-based signals to perform on-chip electrochemical measurements. Cell phones and portable music players are examples of consumer electronics that are easily operated and are ubiquitous worldwide. Audio output (play) and input (record) signals are voltage based and contain frequency and amplitude information. A cell phone, laptop soundcard and two compact audio players are compared with respect to frequency response; the laptop soundcard provides the most uniform frequency response, while the cell phone performance is found to be insufficient. The audio signals in the common portable music players and laptop soundcard operate in the range of 20 Hz to 20 kHz and are found to be applicable, as voltage input and output signals, to impedance-based electrochemical measurements in microfluidic systems. Validated impedance-based measurements of concentration (0.1-50 mM), flow rate (2-120 µL min-1) and particle detection (32 µm diameter) are demonstrated. The prevailing, lossless, wave audio file format is found to be suitable for data transmission to and from external sources, such as a centralized lab, and the cost of all hardware (in addition to audio devices) is ~10 USD. The utility demonstrated here, in combination with the ubiquitous nature of portable audio electronics, presents new opportunities for impedance-based measurements in portable microfluidic systems.

  18. Use of low-frequency electrical impedance measurements to determine phospholipid content in amniotic fluid

    NASA Astrophysics Data System (ADS)

    DeLuca, F.; Cametti, C.; Zimatore, G.; Maraviglia, B.; Pachi', A.

    1996-09-01

    In this report we propose a new method for an in vitro test of the foetal lung maturity based on the measurement of the electrical conductivity of the overall amniotic fluid obtained from transabdominal amniocentesis, since this quantity can be linked to a first approximation in a very simple way to the phospholipid content. We have carried out measurements of 85 different samples of amniotic fluid as a function of gestation weeks and we have observed a pronounced change of the electrical conductivity that reflects the increase in the phospholipid concentration occurring at the end of normal pregnancies. The method could be further developed to obtain similar information on in vivo experiments by means of bioelectric impedance tomography, taking advantage of the frequency dependence of the tissue electrical impedance.

  19. Long-term measurement of impedance in chronically implanted depth and subdural electrodes during responsive neurostimulation in humans.

    PubMed

    Sillay, Karl A; Rutecki, Paul; Cicora, Kathy; Worrell, Greg; Drazkowski, Joseph; Shih, Jerry J; Sharan, Ashwini D; Morrell, Martha J; Williams, Justin; Wingeier, Brett

    2013-09-01

    Long-term stability of the electrode-tissue interface may be required to maintain optimal neural recording with subdural and deep brain implants and to permit appropriate delivery of neuromodulation therapy. Although short-term changes in impedance at the electrode-tissue interface are known to occur, long-term changes in impedance have not previously been examined in detail in humans. To provide further information about short- and long-term impedance changes in chronically implanted electrodes, a dataset from 191 persons with medically intractable epilepsy participating in a trial of an investigational responsive neurostimulation device (the RNS(®) System, NeuroPace, Inc.) was reviewed. Monopolar impedance measurements were available for 391 depth and subdural leads containing a total of 1564 electrodes; measurements were available for median 802 days post-implant (range 28-1634). Although there were statistically significant short-term impedance changes, long-term impedance was stable after one year. Impedances for depth electrodes transiently increased during the third week after lead implantation and impedances for subdural electrodes increased over 12 weeks post-implant, then were stable over the subsequent long-term follow-up. Both depth and subdural electrode impedances demonstrated long-term stability, suggesting that the quality of long-term electrographic recordings (the data used to control responsive brain stimulation) can be maintained over time.

  20. Equivalent circuit simulation of cylindrical monopole impedance measurements in ionospheric electron plasma

    NASA Astrophysics Data System (ADS)

    Kiraga, A.

    Several common problems occur in measurement techniques and interpretation of plasma natural emissions and impedance data. Antenna characteristics are of prime importance in equivalent circuit analysis. Spacecraft - plasma interaction contributes to variability of equivalent circuit impedances and e.m.f. components and imposes constrains on usefulness of experimental data. In order to have independent, built in estimate of local plasma frequency and to get deeper insight into properties of equivalent circuit for wave diagnostics, impedance measurement was integrated with radio receivers on the ACTIVE, APEX and CORONAS satellites. Impedance measurements of 7.5m long monopole were performed in frequency range .1-10MHz with the frequency step of 50kHz, in voltage divider configuration. Due to high inclination of 82.5deg and altitude range of 500-3000km, data from very different plasmas were collected. Data can be split into quasi normal, disturbed and very disturbed measurements. Equivalent circuit structure evolved in attempt to m tcha even very disturbed measurements. For quasi normal measurements, satisfactory matching is obtained with computed gyrofrequency fc and fitted plasma frequency fn, stray capacitance Cs and capacitance Cv of phenomenological vacuum sheath. With Balmain formula for monopole impedance in cold magnetoplasma, two basic spectral structures are explained. For sufficiently magnetized plasma (roughly fn/fc<2 if Cs=20pF), circuit parallel resonance frequency Fr falls into upper hybrid band (max(fn,fc),fu), resonance amplitude is reduced by high antenna resistance and horn like absolute maximum points fu. For values of fn/fc ratio, greater then critical, Fr is less than fn and broad absolute maximum at Fr follows from low antenna resistance. Further increase of fn/fc results in increasing lag of Fr behind fn. Critical rati o fn/fc increases with decreasing stray capacitance Cs. It follows from data analysis that stray capacitance may change in

  1. Phase angle and impedance measurements for nondestructive moisture content determination of in-shell peanuts using a cylindrical sample holder

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple, low cost instrument that measures impedance and phase angle was used along with a parallel-plate capacitance system to estimate the moisture content (MC) of yellow corn. A sample of corn weighing about 100g was placed between the parallel-plate electrodes and the impedance and phase angle...

  2. Field Assessment of Acoustic-Doppler Based Discharge Measurements

    USGS Publications Warehouse

    Mueller, D.S.; ,

    2002-01-01

    The use of equipment based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun a field validation of the instruments currently (2002) available for making discharge measurements from a moving boat in streams of various sizes. Instruments manufactured by SonTek/YSI2 and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made by the use of a Price AA current meter and standard USGS procedures with the acoustic instruments at each site during data collection. The discharges measured with the acoustic instruments were compared with the discharges measured with Price AA meters and the current USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating. Additional analysis of the data collected indicates that the coefficient of variation of the discharge measurements consistently was less for the RD Instruments, Inc. Rio Grandes than it was for the SonTek/YSI RiverSurveyors. The bottom-tracking referenced measurement had a lower coefficient of variation than the differentially corrected global positioning system referenced measurements. It was observed that the higher frequency RiverSurveyors measured a moving bed more often than the lower frequency Rio Grandes. The detection of a moving bed caused RiverSurveyors to be consistently biased low when referenced to bottom tracking. Differentially corrected global positioning system data may be used to remove the bias observed in the bottom-tracking referenced measurements.

  3. Measurements of complex impedance in microwave high power systems with a new bluetooth integrated circuit.

    PubMed

    Roussy, Georges; Dichtel, Bernard; Chaabane, Haykel

    2003-01-01

    By using a new integrated circuit, which is marketed for bluetooth applications, it is possible to simplify the method of measuring the complex impedance, complex reflection coefficient and complex transmission coefficient in an industrial microwave setup. The Analog Devices circuit AD 8302, which measures gain and phase up to 2.7 GHz, operates with variable level input signals and is less sensitive to both amplitude and frequency fluctuations of the industrial magnetrons than are mixers and AM crystal detectors. Therefore, accurate gain and phase measurements can be performed with low stability generators. A mechanical setup with an AD 8302 is described; the calibration procedure and its performance are presented.

  4. Nonlinear acoustic measurements ahead of a notch during fatigue

    NASA Astrophysics Data System (ADS)

    Martin, R. W.; Mooers, R. D.; Hutson, A. L.; Sathish, S.; Blodgett, M. P.

    2013-01-01

    This paper presents measurements of relative nonlinear acoustic parameter (βrel), ahead of a notch in Al 7075-T651 dog bone samples, subjected to fatigue. It is compared with crack growth measurements on the same samples. Measurements performed on two samples subjected to identical fatigue conditions that failed at vastly different number of fatigue cycles are described. The βrel measurement for both samples as a function of fatigue cycles was fit a Boltzmann curve. The role of changing βrel ahead of a notch is explored as a possible approach for remain life evaluation.

  5. Acoustic property measurements in a photoacoustic imager

    NASA Astrophysics Data System (ADS)

    Willemink, René G. H.; Manohar, Srirang; Slump, Cornelis H.; van der Heijden, Ferdi; van Leeuwen, Ton

    2007-07-01

    Photoacoustics is a hybrid imaging technique that combines the contrast available to optical imaging with the resolution that is possessed by ultrasound imaging. The technique is based on generating ultrasound from absorbing structures in tissue using pulsed light. In photoacoustic (PA) computerized tomography (CT) imaging, reconstruction of the optical absorption in a subject, is performed for example by filtered backprojection. The backprojection is performed along circular paths in image space instead of along straight lines as in X-ray CT imaging. To achieve this, the speed-of-sound through the subject is usually assumed constant. An unsuitable speed-of-sound can degrade resolution and contrast. We discuss here a method of actually measuring the speed-of- sound distribution using ultrasound transmission through the subject under photoacoustic investigation. This is achieved in a simple approach that does not require any additional ultrasound transmitter. The method uses a passive element (carbon fiber) that is placed in the imager in the path of the illumination which generates ultrasound by the photoacoustic effect and behaves as an ultrasound source. Measuring the time-of-flight of this ultrasound transient by the same detector used for conventional photoacoustics, allows a speed-of-sound image to be reconstructed. This concept is validated on phantoms.

  6. Acoustics and Surface Pressure Measurements from Tandem Cylinder Configurations

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Brooks, Thomas F.; Lockard, David P.; Choudhari, Meelan M.; Stead, Daniel J.

    2014-01-01

    Acoustic and unsteady surface pressure measurements from two cylinders in tandem configurations were acquired to study the effect of spacing, surface trip and freestream velocity on the radiated noise. The Reynolds number ranged from 1.15x10(exp 5) to 2.17x10(exp 5), and the cylinder spacing varied between 1.435 and 3.7 cylinder diameters. The acoustic and surface pressure spectral characteristics associated with the different flow regimes produced by the cylinders' wake interference were identified. The dependence of the Strouhal number, peak Sound Pressure Level and spanwise coherence on cylinder spacing and flow velocity was examined. Directivity measurements were performed to determine how well the dipole assumption for the radiation of vortex shedding noise holds for the largest and smallest cylinder spacing tested.

  7. Atypical prosody in Asperger syndrome: perceptual and acoustic measurements.

    PubMed

    Filipe, Marisa G; Frota, Sónia; Castro, São Luís; Vicente, Selene G

    2014-08-01

    It is known that individuals with Asperger syndrome (AS) may show no problems with regard to what is said (e.g., lexical content) but tend to have difficulties in how utterances are produced, i.e., they may show prosodic impairments. In the present study, we focus on the use of prosodic features to express grammatical meaning. Specifically, we explored the sentence type difference between statements and questions that is conveyed by intonation, using perceptual and acoustic measurements. Children aged 8 and 9 years with AS (n = 12) were matched according to age and nonverbal intelligence with typically developing peers (n = 17). Although children with AS could produce categorically accurate prosodic patterns, their prosodic contours were perceived as odd by adult listeners, and acoustic measurements showed alterations in duration and pitch. Additionally, children with AS had greater variability in fundamental frequency contours compared to typically developing peers.

  8. Determining Transmission Loss from Measured External and Internal Acoustic Environments

    NASA Technical Reports Server (NTRS)

    Scogin, Tyler; Smith, A. M.

    2012-01-01

    An estimate of the internal acoustic environment in each internal cavity of a launch vehicle is needed to ensure survivability of Space Launch System (SLS) avionics. Currently, this is achieved by using the noise reduction database of heritage flight vehicles such as the Space Shuttle and Saturn V for liftoff and ascent flight conditions. Marshall Space Flight Center (MSFC) is conducting a series of transmission loss tests to verify and augment this method. For this test setup, an aluminum orthogrid curved panel representing 1/8th of the circumference of a section of the SLS main structure was mounted in between a reverberation chamber and an anechoic chamber. Transmission loss was measured across the panel using microphones. Data measured during this test will be used to estimate the internal acoustic environments for several of the SLS launch vehicle internal spaces.

  9. Dependence of Impedance Measurement Sensitivity of Cell Growth on Sensing Area of Circular Interdigitated Electrode.

    PubMed

    Park, Jinsoo; Hwang, Kyo Seon; Cho, Sungbo

    2015-10-01

    A circular interdigitated electrode (IDE) array for label-free and real-time impedance monitoring of cell growth was fabricated and evaluated. Both the width and spacing of fingers were 50 μm, and the exposed sensing area of the circular IDE was 1.3~3.4 mm. The electrical characteristics of the fabricated circular IDE were modeled as an equivalent circuit, and the values of the circuit parameters extrapolated from the fitting to the measured spectra in different concentrations of NaCl or sensing areas of the circular IDE were analyzed. During cell growth, the resistance of cells extrapolated from the fitting was increased and the maximum rate of change in the real part of the impedance was observed at frequencies of 10 to 22 kHz. The normalized real part of the impedance measured at 10 kHz during cell growth was increased more with decreasing the electrode sensing area, albeit the number of cells to be investigated showed a corresponding increase.

  10. Microwave Surface Impedance Measurements of SrFe2(As,P)2 Single Crystals

    NASA Astrophysics Data System (ADS)

    Takahashi, Hideyuki; Imai, Yoshinori; Maeda, Atsutaka; Kitagawa, Kentaro; Matsubayashi, Kazuyuki; Takigawa, Masashi; Uwatoko, Yoshiya

    2012-02-01

    Various pairing symmetries have been proposed concerning Fe-based superconductors both theoretically and experimentally. It was reported that LaFePO[1] and BaFe2(As,P)2[2] have line nodes in their superconducting gap. It is in sharp contrast to other Fe-based compounds such as LiFeAs[3] and Fe(Se,Te)[4]. To confirm whether line nodes in gap function is a common feature among P doped systems, we measured the microwave surface impedances of SrFe2(As,P)2 single crystals (Tc˜30K). Single crystals were grown by self-flux method. The surface impedances were measured using a cavity perturbation technique. The imaginary part of surface impedance, which is proportional to London penetration depth in the superconducting state, shows a power law, λ(T)-λ(0)T^n. The power law indicates low-energy quasiparticle excitation, and an exponent slightly smaller than 2 does not exclude the possibility of the existence of line nodes. [ 1 ] J. D. Fletcher et al., Phys. Rev. Lett. 102 (2009) 147001.[ 2 ] K. Hashimoto et al., Phys. Rev. B 81 (2010) 220501(R).[ 3 ] Y. Imai et al., J. Phys. Soc. Jpn. 80 (2011) 013704.[ 4 ] H. Takahashi et al., Phys. Rev. B 84. (2011) 132503.

  11. Evaluation of indirect impedance for measuring microbial growth in complex food matrices.

    PubMed

    Johnson, N; Chang, Z; Bravo Almeida, C; Michel, M; Iversen, C; Callanan, M

    2014-09-01

    The suitability of indirect impedance to accurately measure microbial growth in real food matrices was investigated. A variety of semi-solid and liquid food products were inoculated with Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Lactobacillus plantarum, Pseudomonas aeruginosa, Escherichia coli, Salmonella enteriditis, Candida tropicalis or Zygosaccharomyces rouxii and CO2 production was monitored using a conductimetric (Don Whitely R.A.B.I.T.) system. The majority (80%) of food and microbe combinations produced a detectable growth signal. The linearity of conductance responses in selected food products was investigated and a good correlation (R(2) ≥ 0.84) was observed between inoculum levels and times to detection. Specific growth rate estimations from the data were sufficiently accurate for predictive modeling in some cases. This initial evaluation of the suitability of indirect impedance to generate microbial growth data in complex food matrices indicates significant potential for the technology as an alternative to plating methods.

  12. Measurement of the coupling impedances of the kickers in the SIS and ESR at GSI.

    NASA Astrophysics Data System (ADS)

    Blell, U.

    1997-05-01

    At high particle intensities coherent transverse beam oscillations may be excited due to the coupling of the beam to individual accelerators structures. The characteristic values to describe these beam instabilities are the longitudinal- and transverse coupling impedances. One reason for this beam instability is the inductive interaction between the beam and the kicker magnets. The type of the magnet, e.g. window-frame magnet or C-magnet, and its external electrical network are the most important quantities to identify the coupling impedances below the cut-off frequency of the beam pipe. For the kicker modules in the SIS and ESR accelerators at GSI the mathematical basis, theory and measured results will be presented.

  13. Validation of streamflow measurements made with acoustic doppler current profilers

    USGS Publications Warehouse

    Oberg, K.; Mueller, D.S.

    2007-01-01

    The U.S. Geological Survey and other international agencies have collaborated to conduct laboratory and field validations of acoustic Doppler current profiler (ADCP) measurements of streamflow. Laboratory validations made in a large towing basin show that the mean differences between tow cart velocity and ADCP bottom-track and water-track velocities were -0.51 and -1.10%, respectively. Field validations of commercially available ADCPs were conducted by comparing streamflow measurements made with ADCPs to reference streamflow measurements obtained from concurrent mechanical current-meter measurements, stable rating curves, salt-dilution measurements, or acoustic velocity meters. Data from 1,032 transects, comprising 100 discharge measurements, were analyzed from 22 sites in the United States, Canada, Sweden, and The Netherlands. Results of these analyses show that broadband ADCP streamflow measurements are unbiased when compared to the reference discharges regardless of the water mode used for making the measurement. Measurement duration is more important than the number of transects for reducing the uncertainty of the ADCP streamflow measurement. ?? 2007 ASCE.

  14. Acoustic temperature profile measurement technique for large combustion chambers

    NASA Technical Reports Server (NTRS)

    Venkateshan, S. P.; Shakkottai, P.; Kwack, E. Y.; Back, L. H.

    1989-01-01

    Measurement of times of flight of sound waves can be used to determine temperatures in a gas. This paper describes a system, based on this principle, that is capable of giving the temperature profile in a nonisothermal gas volume, for example, prevalent in a large furnace. The apparatus is simple, rugged, accurate, and capable of being automated for process control applications. It is basically an acoustic waveguide where the outside temperature profile is transferred to a chosen gas contained inside the guide.

  15. Effect of diffusion on impedance measurements in a hydrodynamic flow focusing sensor.

    PubMed

    Nasir, Mansoor; Price, Dorielle T; Shriver-Lake, Lisa C; Ligler, Frances

    2010-10-21

    This paper investigated the effects of diffusion between non-conductive sheath and conductive sample fluids in an impedance-based biosensor. Impedance measurements were made with 2- and 4-electrode configurations. The 4-electrode design offers the advantage of impedance measurements at low frequencies (<1 kHz) without the deleterious effects of double layer impedance which are present in the 2-electrode design. Hydrodynamic flow focusing was achieved with a modified T-junction design with a smaller cross-section for the sample channel than for the focusing channel, which resulted in 2D focusing of the sample stream with just one sheath stream. By choosing a non-conductive sheath fluid and a conductive sample fluid, the electric field was confined to the focused stream. In order to utilize this system for biosensing applications, we characterized it for electrical and flow parameters. In particular, we investigated the effects of varying flow velocities and flow-rate ratios on the focused stream. Increasing flow-rate ratios reduced the cross-sectional area of the focused streams as was verified by finite element modeling and confocal microscopy. Antibody mediated binding of Escherichia coli to the electrode surface caused an increase in solution resistance at low frequencies. The results also showed that the diffusion mass transport at the interface of the two streams limited the benefits of increased flow focusing. Increasing flow velocities could be used to offset the diffusion effect. To optimize detection sensitivity, flow parameters and mass transport must be considered in conjunction, with the goal of reducing diffusion of conducting species out of the focused stream while simultaneously minimizing its cross-sectional area.

  16. Continuous Non-Invasive Monitoring of Tidal Volumes by Measurement of Tidal Impedance in Neonatal Piglets

    PubMed Central

    Kurth, Florian; Zinnow, Fabienne; Prakapenia, Alexandra; Dietl, Sabrina; Winkler, Stefan; Ifflaender, Sascha; Rüdiger, Mario; Burkhardt, Wolfram

    2011-01-01

    Background Electrical Impedance measurements can be used to estimate the content of intra-thoracic air and thereby give information on pulmonary ventilation. Conventional Impedance measurements mainly indicate relative changes, but no information concerning air-volume is given. The study was performed to test whether a 3-point-calibration with known tidal volumes (VT) during conventional mechanical ventilation (CMV) allows subsequent calculation of VT from total Tidal-Impedance (tTI) measurements using Quadrant Impedance Measurement (QIM). In addition the distribution of TI in different regions of the thorax was examined. Methodology and Principal Findings QIM was performed in five neonatal piglets during volume-controlled CMV. tTI values at three different VT (4, 6, 8 ml/kg) were used to establish individual calibration curves. Subsequently, each animal was ventilated with different patterns of varying VT (2–10 ml/kg) at different PEEP levels (0, 3, 6, 9, 12 cmH2O). VT variation was repeated after surfactant depletion by bronchoalveolar lavage. VT was calculated from tTI values (VTcalc) and compared to the VT delivered by the ventilator (VTPNT). Bland-Altman analysis revealed good agreement between VTcalc and VTPNT before (bias −0.08 ml; limits of agreement −1.18 to 1.02 ml at PEEP = 3 cmH2O) and after surfactant depletion (bias −0.17 ml; limits of agreement −1.57 to 1.22 ml at PEEP = 3 cmH2O). At higher PEEP levels VTcalc was lower than VTPNT, when only one fixed calibration curve (at PEEP 3 cmH2O) was used. With a new calibration curve at each PEEP level the method showed similar accuracy at each PEEP level. TI showed a homogeneous distribution over the four assessed quadrants with a shift toward caudal regions of the thorax with increasing VT. Conclusion Tidal Impedance values could be used for precise and accurate calculation of VT during CMV in this animal study, when calibrated at each PEEP level. PMID:21687746

  17. Procedure for the semi-automatic detection of gastro-oesophageal reflux patterns in intraluminal impedance measurements in infants.

    PubMed

    Trachterna, M; Wenzl, T G; Silny, J; Rau, G; Heimann, G

    1999-04-01

    The diagnosis of gastro-oesophageal reflux (GOR) is of great interest for paediatric gastroenterologists. pH monitoring is the commonly used procedure for GOR diagnosis but a major amount of postprandial GOR is missed due to the mostly non-acidic gastric contents in infants. The multiple intraluminal impedance technique is based on the recording of the impedance changes during bolus transport inside the oesophagus. It is the first method which allows the pH-independent, long-term registration of GOR. The use of the impedance technology in clinical practice has been limited so far by the time-consuming, visual evaluation of the impedance traces. The new approach of a semi-automatic analysis of the impedance measurements allows the automated detection of reflux patterns. It is based on event marking and an optimised feature description of the impedance traces combined with a fuzzy system for pattern recognition. The classifier is developed and tested on 50 investigations in infants. Compared to the comprehensive, multiple visual evaluation the achieved precision is 75% sensitivity and 48% positive prediction. In comparison to a single visual evaluation the analysis of the automatically proposed patterns corresponds to a 96% reduction of the evaluation time with no loss of precision. Thus the applicability of the impedance technology is enhanced significantly. A combined measurement of pH and impedance gives evidence about the occurrence of GOR, its pH and the acidic exposure of the oesophagus.

  18. Flow velocity measurement with the nonlinear acoustic wave scattering

    SciTech Connect

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  19. Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

    SciTech Connect

    Ranjbar, V.H.; Tan, C.Y.; /Fermilab

    2011-08-01

    The combined effect of impedance and higher order chromaticity can act on the beam in a nontrivial manner which can cause a tune shift which depends on the relative momenta with respect to the 'on momentum' particle ({Delta}p/p). Experimentally, this tune shift affects the measurement of the linear chromaticity which is traditionally measured with a change of {Delta}p/p. The theory behind this effect will be derived in this paper. Computer simulations and experimental data from the Tevatron will be used to support the theory.

  20. Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn-Mn ferrites

    SciTech Connect

    Hankare, P.P.; Patil, R.P.; Garadkar, K.M.; Sasikala, R.; Chougule, B.K.

    2011-03-15

    Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

  1. Current density distribution in cylindrical Li-Ion cells during impedance measurements

    NASA Astrophysics Data System (ADS)

    Osswald, P. J.; Erhard, S. V.; Noel, A.; Keil, P.; Kindermann, F. M.; Hoster, H.; Jossen, A.

    2016-05-01

    In this work, modified commercial cylindrical lithium-ion cells with multiple separate current tabs are used to analyze the influence of tab pattern, frequency and temperature on electrochemical impedance spectroscopy. In a first step, the effect of different current tab arrangements on the impedance spectra is analyzed and possible electrochemical causes are discussed. In a second step, one terminal is used to apply a sinusoidal current while the other terminals are used to monitor the local potential distribution at different positions along the electrodes of the cell. It is observed that the characteristic decay of the voltage amplitude along the electrode changes non-linearly with frequency, where high-frequent currents experience a stronger attenuation along the current collector than low-frequent currents. In further experiments, the decay characteristic is controlled by the cell temperature, driven by the increasing resistance of the current collector and the enhanced kinetic and transport properties of the active material and electrolyte. Measurements indicate that the ac current distribution depends strongly on the frequency and the temperature. In this context, the challenges for electrochemical impedance spectroscopy as cell diagnostic technique for commercial cells are discussed.

  2. Method of utility-system source-impedance measurement for the industrial power engineer

    SciTech Connect

    Corvin, W C

    1982-05-24

    In general, the power company that delivers energy to an industrial power system will supply, upon request, information describing the utility source impedance at the point of interconnection with the industrial customer. this information is usually expressed as the maximum available short-circuit MVA (megavolt amperes) that the utility can deliver at some nominal voltage. For sizing the interrupting ratings of protective equipment, this number is important. However, better information is required for modeling the utility system under all conditions of system switching, generation, and loading. In this paper a method is described for measuring the utility source impedance that gives a more realistic representation of the utility at the point of interconnection. It is increasingly important that the industrial power engineer accurately view the power company as a power source of variable impedance. Industrial loads may operate and interact differently, depending on the relative stiffness of their power source. Electric utilities increasingly experience planned voltage reductions, brownouts, and temporary line-switching configurations that can leave the industrial customer with a power source far different from the one normally expected.

  3. Electrochemical impedance measurement of prostate cancer cells using carbon nanotube array electrodes in a microfluidic channel

    NASA Astrophysics Data System (ADS)

    Heung Yun, Yeo; Dong, Zhongyun; Shanov, Vesselin N.; Schulz, Mark J.

    2007-11-01

    Highly aligned multi-wall carbon nanotubes were synthesized in the shape of towers and embedded into fluidic channels as electrodes for impedance measurement of LNCaP human prostate cancer cells. Tower electrodes up to 8 mm high were grown and easily peeled off a silicon substrate. The nanotube electrodes were then successfully soldered onto patterned printed circuit boards and cast into epoxy under pressure. After polishing the top of the tower electrodes, RF plasma was used to enhance the electrocatalytic effect by removing excess epoxy and activating the open end of the nanotubes. Electrodeposition of Au particles on the plasma-treated tower electrodes was done at a controlled density. Finally, the nanotube electrodes were embedded into a polydimethylsiloxane (PDMS) channel and electrochemical impedance spectroscopy was carried out with different conditions. Preliminary electrochemical impedance spectroscopy results using deionized water, buffer solution, and LNCaP prostate cancer cells showed that nanotube electrodes can distinguish the different solutions and could be used in future cell-based biosensor development.

  4. High throughput and automatic colony formation assay based on impedance measurement technique.

    PubMed

    Lei, Kin Fong; Kao, Chich-Hao; Tsang, Ngan-Ming

    2017-03-02

    To predict the response of in vivo tumors, in vitro culture of cell colonies was suggested to be a standard assay to achieve high clinical relevance. To describe the responses of cell colonies, the most widely used quantification method is to count the number and size of cell colonies under microscope. That makes the colony formation assay infeasible to be high throughput and automated. In this work, in situ analysis of cell colonies suspended in soft hydrogel was developed based on impedance measurement technique. Cell colonies cultured between a pair of parallel plate electrodes were successfully analyzed by coating a layer of base hydrogel on one side of electrode. Real-time and label-free monitoring of cell colonies was realized during the culture course. Impedance magnitude and phase angle respectively represented the summation effect of colony responses and size of colonies. In addition, dynamic response of drug-treated colonies was demonstrated. High throughput and automatic colony formation assay was realized to facilitate more objective assessments in cancer research. Graphical Abstract High throughput and automatic colony formation assay was realized by in situ impedimetric analysis across a pair of parallel plate electrodes in a culture chamber. Cell colonies suspended in soft hydrogel were cultured under the tested substance and their dynamic response was represented by impedance data.

  5. Damage detection in plates using the electromechanical impedance technique based on decoupled measurements of piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Tinoco, Hector A.; Robledo-Callejas, Leonardo; Marulanda, Dairon J.; Serpa, Alberto L.

    2016-12-01

    Electromechanical impedance (EMI) technique plays an important role in the monitoring of structures with piezoelectric transducers (PT). According to the EMI technique, diagnosis and prognosis can be carried out to detect structural modifications in an operative state. However, to develop an efficient methodology for damage detection; damage metrics and patterns should be defined using indices to quantify changes in the signals. In this study, a new approach is proposed considering the electrical impedance (EI) of PT as an array of coupled electrical impedances. It means that when a PT is bonded to a structure, the EI is governed by an electrical circuit that is assumed to be parallel and composed by electrical contributions of both, the structure and the PT. In our perspective, each free PT presents unique mechanical characteristics and those differences may influence the measured electrical signals, therefore the electrical contributions generated by each piezo-transducer are taken into account. To evaluate the electrical decoupling, two methodologies of damage detection are proposed to identify and locate an induced damage. In these methodologies, the damage metrics are based on ellipses of Gaussian confidence. Four experimental tests were performed to evaluate the methodologies, applying two damage intensities. The results show that the partial process of identification of a damage type is a feasible and applicable procedure, moreover the proposed method was able to evidence the damage location..

  6. Determining low-frequency source location from acoustic phase measurements

    NASA Astrophysics Data System (ADS)

    Poole, Travis L.; Frisk, George V.

    2002-11-01

    For low-frequency cw sound sources in shallow water, the time rate-of-change of the measured acoustic phase is well approximated by the time rate-of-change of the source-receiver separation distance. An algorithm for determining a locus of possible source locations based on this idea has been developed. The locus has the general form of a hyperbola, which can be used to provide a bearing estimation at long ranges, and an estimate of source location at short ranges. The algorithm uses only acoustic phase data and receiver geometry as input, and can be used even when the source frequency is slightly unstable and/or imprecisely known. The algorithm has been applied to data from low-frequency experiments (20-300 Hz), both for stable and unstable source frequencies, and shown to perform well. [Work supported by ONR and WHOI Academic Programs Office.

  7. A GR/Impedance probe proves unsuitable for measuring GR depth in Australian lamb carcases.

    PubMed

    Fowler, Stephanie M; Hoban, Jordan M; van de Ven, Remy; Boyce, Mal; Williams, Andrew; Pethick, David W; Hopkins, David L

    2017-02-27

    Multiple studies were conducted at 3 abattoirs to determine the potential of a dual function GR/Impedance probe to measure GR soft- tissue depth (depth at the 12th rib, 110mm from the mid line of the carcase) of typical lamb carcases processed in Australia. Lamb carcases (1016) were measured approximately 25min post slaughter with the probe and a GR knife as the most commonly used measurement. Modelling indicated that variation in the measurement using the probe compared to the measurement using the knife occurred with increasing carcase weight and fatness as well as between different abattoirs. Consequently, the probe in its current design cannot provide the repeatable measurement required by industry.

  8. Electrical impedance spectroscopy device for measurement of moisture gradients in wood

    NASA Astrophysics Data System (ADS)

    Tiitta, M.; Olkkonen, H.

    2002-08-01

    A prototype of the electrical impedance spectroscopy (EIS) device for the measurement of internal moisture gradients in wood was developed. The EIS device consists of a hand-held probe connected to a control unit interfaced with a portable personal computer and a power unit. In the measurement, parallel flat electrodes of the measuring probe are laid against the wood specimen and the sine wave excitation is applied in the frequency range 1-100 kHz. The measured amplitude and phase spectral data were analyzed using the model based on constant phase elements. A spectral analysis software package was designed for measurement of subsurface transverse moisture gradients. The EIS device was tested with many types of uniform, desorption, and absorption gradients in lumber, pulpwood, and log specimens from spruce, pine, and birch. The EIS device can be easily transferred in a small case allowing field measurements.

  9. On chip droplet characterization: a practical, high-sensitivity measurement of droplet impedance in digital microfluidics.

    PubMed

    Sadeghi, Saman; Ding, Huijiang; Shah, Gaurav J; Chen, Supin; Keng, Pei Yuin; Kim, Chang-Jin; van Dam, R Michael

    2012-02-21

    We demonstrate a new approach to impedance measurement on digital microfluidics chips for the purpose of simple, sensitive, and accurate volume and liquid composition measurement. Adding only a single series resistor to existing AC droplet actuation circuits, the platform is simple to implement and has negligible effect on actuation voltage. To accurately measure the complex voltage across the resistor (and hence current through the device and droplet), the designed system is based on software-implemented lock-in amplification detection of the voltage drop across the resistor which filters out noise, enabling high-resolution and low-limit signal recovery. We observe picoliter sensitivity with linear correlation of voltage to volume extending to the microliter volumes that can be handled by digital microfluidic devices. Due to the minimal hardware, the system is robust and measurements are highly repeatable. The detection technique provides both phase and magnitude information of the real-time current flowing through the droplet for a full impedance measurement. The sensitivity and resolution of this platform enables it to distinguish between various liquids which, as demonstrated in this paper, could potentially be extended to quantify solute concentrations, liquid mixtures, and presence of analytes.

  10. Visualized Multiprobe Electrical Impedance Measurements with STM Tips Using Shear Force Feedback Control

    PubMed Central

    Botaya, Luis; Coromina, Xavier; Samitier, Josep; Puig-Vidal, Manel; Otero, Jorge

    2016-01-01

    Here we devise a multiprobe electrical measurement system based on quartz tuning forks (QTFs) and metallic tips capable of having full 3D control over the position of the probes. The system is based on the use of bent tungsten tips that are placed in mechanical contact (glue-free solution) with a QTF sensor. Shear forces acting in the probe are measured to control the tip-sample distance in the Z direction. Moreover, the tilting of the tip allows the visualization of the experiment under the optical microscope, allowing the coordination of the probes in X and Y directions. Meanwhile, the metallic tips are connected to a current–voltage amplifier circuit to measure the currents and thus the impedance of the studied samples. We discuss here the different aspects that must be addressed when conducting these multiprobe experiments, such as the amplitude of oscillation, shear force distance control, and wire tilting. Different results obtained in the measurement of calibration samples and microparticles are presented. They demonstrate the feasibility of the system to measure the impedance of the samples with a full 3D control on the position of the nanotips. PMID:27231911

  11. Vertical impedance measurements of concrete bridge deck cover condition without a direct electrical connection to the reinforcing steel

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Baxter, Jared; Barton, Jeffrey; Guthrie, W. Spencer

    2017-02-01

    Vertical impedance measurements provide significant quantitative information about the ability of concrete cover to slow the penetration of chloride ions that can corrode steel reinforcement in a bridge deck. The primary limitations preventing the widespread adoption of vertical impedance for assessment of concrete bridge decks are (1) the necessity to have a direct electrical connection to the embedded steel reinforcement and (2) the low speeds of data acquisition. This work presents solutions to both limitations. A method using a large-area electrode as a reference electrode for vertical impedance testing is validated using both simulations and measurements in the field.

  12. Acoustic force measurement in a dual-temperature resonant chamber

    NASA Technical Reports Server (NTRS)

    Robey, Judith L.; Trinh, Eugene H.; Wang, Taylor G.

    1987-01-01

    The acoustic radiation force was measured for a dual-temperature resonant chamber. This rectangular chamber has its long dimension approximately 8.5 times the square cross-sectional dimension, and the opposite ends are at widely different temperatures. Force profiles were obtained for two hot end temperatures of 520 C and 760 C, while the cool end remained at approximately room temperature. Force magnitudes as high as 17 dyn for a sample 1.2 cm in diameter at 760 C and at 162-dB input level were measured.

  13. Measuring acoustic nonlinearity parameter using collinear wave mixing

    NASA Astrophysics Data System (ADS)

    Liu, Minghe; Tang, Guangxin; Jacobs, Laurence J.; Qu, Jianmin

    2012-07-01

    This study introduces a new acoustic nonlinearity parameter βT. It is shown that βT is associated with the interaction between a longitudinal wave and a shear wave in isotropic elastic solids with quadratic nonlinearity. Experimental measurements are conducted to demonstrate that the collinear wave mixing technique is capable of measuring βT nondestructively. Further, it is shown that βT is well-correlated with the plastic deformation in Al-6061 alloys. These results indicate that collinear wave mixing is a promising method for nondestructive assessment of plastic deformation, and possibly, fatigue damage in metallic materials.

  14. Evaluation of disfluent speech by means of automatic acoustic measurements.

    PubMed

    Lustyk, Tomas; Bergl, Petr; Cmejla, Roman

    2014-03-01

    An experiment was carried out to determine whether the level of the speech fluency disorder can be estimated by means of automatic acoustic measurements. These measures analyze, for example, the amount of silence in a recording or the number of abrupt spectral changes in a speech signal. All the measures were designed to take into account symptoms of stuttering. In the experiment, 118 audio recordings of read speech by Czech native speakers were employed. The results indicate that the human-made rating of the speech fluency disorder in read speech can be predicted on the basis of automatic measurements. The number of abrupt spectral changes in the speech segments turns out to be the most appropriate measure to describe the overall speech performance. The results also imply that there are measures with good results describing partial symptoms (especially fixed postures without audible airflow).

  15. Velocity measurements in whole blood using acoustic resolution photoacoustic Doppler

    PubMed Central

    Brunker, Joanna; Beard, Paul

    2016-01-01

    Acoustic resolution photoacoustic Doppler velocimetry promises to overcome the spatial resolution and depth penetration limitations of current blood flow measuring methods. Despite successful implementation using blood-mimicking fluids, measurements in blood have proved challenging, thus preventing in vivo application. A common explanation for this difficulty is that whole blood is insufficiently heterogeneous relative to detector frequencies of tens of MHz compatible with deep tissue photoacoustic measurements. Through rigorous experimental measurements we provide new insight that refutes this assertion. We show for the first time that, by careful choice of the detector frequency and field-of-view, and by employing novel signal processing methods, it is possible to make velocity measurements in whole blood using transducers with frequencies in the tens of MHz range. These findings have important implications for the prospects of making deep tissue measurements of blood flow relevant to the study of microcirculatory abnormalities associated with cancer, diabetes, atherosclerosis and other conditions. PMID:27446707

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

    NASA Astrophysics Data System (ADS)

    Shuai, Q.; Zhou, K.; Zhou, Shiyu; Tang, J.

    2017-04-01

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

  17. Investigation of potential artefactual changes in measurements of impedance changes during evoked activity: implications to electrical impedance tomography of brain function.

    PubMed

    Aristovich, Kirill Y; Dos Santos, Gustavo S; Holder, David S

    2015-06-01

    Electrical impedance tomography (EIT) could provide images of fast neural activity in the adult human brain with a resolution of 1 ms and 1 mm by imaging impedance changes which occur as ion channels open during neuronal depolarization. The largest changes occur at dc and decrease rapidly over 100 Hz. Evoked potentials occur in this bandwidth and may cause artefactual apparent impedance changes if altered by the impedance measuring current. These were characterized during the compound action potential in the walking leg nerves of Cancer pagurus, placed on Ag/AgCl hook electrodes, to identify how to avoid artefactual changes during brain EIT. Artefact-free impedance changes (δZ) decreased with frequency from -0.045 ± 0.01% at 225 Hz to -0.02 ± 0.01% at 1025 Hz (mean ± 1 SD, n = 24 in 12 nerves) which matched changes predicted by a finite element model. Artefactual δZ reached c.300% and 50% of the genuine membrane impedance change at 225 Hz and 600 Hz respectively but decreased with frequency of the applied current and was negligible above 1 kHz. The proportional amplitude (δZ (%)) of the artefact did not vary significantly with the amplitude of injected current of 5-20 µA pp. but decreased significantly from -0.09 ± 0.024 to -0.03 ± 0.023% with phase of 0 to 45°. For fast neural EIT of evoked activity in the brain, artefacts may arise with applied current of >10 µA. Independence of δZ with respect to phase but not the amplitude of applied current controls for them; they can be minimized by randomizing the phase of the applied measuring current and excluded by recording at >1 kHz.

  18. Comparison of multi-microphone transfer matrix measurements with acoustic network models of swirl burners

    NASA Astrophysics Data System (ADS)

    Fischer, A.; Hirsch, C.; Sattelmayer, T.

    2006-11-01

    Utilizing the close analogy between electronic circuits and ducted acoustic systems, mathematical methods originally developed for the characterization of electronic networks are applied to the experimental acoustic plane wave characterization of swirl burners with complex geometries. The experiments presented in the paper show that the acoustic behavior of swirl generators can be quantitatively evaluated treating them as acoustic two-ports. Such acoustic two-ports are presented in forms of transfer-, scattering- and mobility matrices of the element. In the acoustic burner study dynamic pressure measurements were made at several locations of a tubular combustor test rig for two acoustically independent states, which were generated by forcing with sirens at the opposite ends of the setup. The technique for the experimental evaluation of acoustic transfer matrices of complex geometries on the basis of these dynamic pressure measurements is illustrated. As an alternative to the experiment, the evaluation of the acoustic behavior of acoustic systems is assessed using acoustic networks consisting of simple acoustic elements like ducts, bends, junctions and sudden area changes with transfer matrices, which are derived from first principles. In the paper, a network model representing the transfer characteristics of swirl burners is presented and compared with the previously measured transfer matrices. Although the burner geometry is rather complex, its acoustic behavior can be successfully mapped to a network consisting of a serial connection of nine elements with only minor adjustment of one parameter.

  19. Age effects in the human middle ear: Wideband acoustical measures

    NASA Astrophysics Data System (ADS)

    Feeney, M. Patrick; Sanford, Chris A.

    2004-12-01

    Studies that have examined age effects in the human middle ear using either admittance measures at 220 or 660 Hz or multifrequency tympanometry from 200 to 2000 Hz have had conflicting results. Several studies have suggested an increase in admittance with age, while several others have suggested a decrease in admittance with age. A third group of studies found no significant age effect. This study examined 226 Hz tympanometry and wideband energy reflectance and impedance at ambient pressure in a group of 40 young adults and a group of 30 adults with age >=60 years. The groups did not differ in admittance measures of the middle ear at 226 Hz. However, significant age effects were found in wideband energy reflectance and impedance. In particular, in older adults there was a comparative decrease in reflectance from 800 to 2000 Hz but an increase near 4000 Hz. The results suggest a decrease in middle-ear stiffness with age. The findings of this study hold relevance for understanding the aging process in the auditory system, for the establishment of normative data for wideband energy reflectance, for the possibility of a conductive component to presbycusis, and for the interpretation of otoacoustic emission measurements. .

  20. An Acoustic Measure for Word Prominence in Spontaneous Speech

    PubMed Central

    Wang, Dagen; Narayanan, Shrikanth

    2010-01-01

    An algorithm for automatic speech prominence detection is reported in this paper. We describe a comparative analysis on various acoustic features for word prominence detection and report results using a spoken dialog corpus with manually assigned prominence labels. The focus is on features such as spectral intensity and speech rate that are directly extracted from speech based on a correlation-based approach without requiring explicit linguistic or phonetic knowledge. Additionally, various pitch-based measures are studied with respect to their discriminating ability for prominence detection. A parametric scheme for modeling pitch plateau is proposed and this feature alone is found to outperform the traditional local pitch statistics. Two sets of experiments are used to explore the usefulness of the acoustic score generated using these features. The first set focuses on a more traditional way of word prominence detection based on a manually-tagged corpus. A 76.8% classification accuracy was achieved on a corpus of role-playing spoken dialogs. Due to difficulties in manually tagging speech prominence into discrete levels (categories), the second set of experiments focuses on evaluating the score indirectly. Specifically, through experiments on the Switchboard corpus, it is shown that the proposed acoustic score can discriminate between content word and function words in a statistically significant way. The relation between speech prominence and content/function words is also explored. Since prominent words tend to be predominantly content words, and since content words can be automatically marked from text-derived part of speech (POS) information, it is shown that the proposed acoustic score can be indirectly cross-validated through POS information. PMID:20454538

  1. Impedance simulations and measurements on the LHC collimators with embedded beam position monitors

    NASA Astrophysics Data System (ADS)

    Biancacci, N.; Caspers, F.; Kuczerowski, J.; Métral, E.; Mounet, N.; Salvant, B.; Mostacci, A.; Frasciello, O.; Zobov, M.

    2017-01-01

    The LHC collimation system is a critical element for the safe operation of the LHC machine. The necessity of fast accurate positioning of the collimator's jaws, recently introduced the need to have button beam position monitors directly embedded in the jaws extremities of the LHC tertiary collimators and some secondary collimators. This addition led to a new design of these collimators including ferrites to damp higher order modes instead of rf fingers. In this work we will present the impedance bench measurements and simulations on a TCT (Transverse Tertiary Collimator) prototype including estimations for beam stability for the LHC.

  2. Measurement of lung function using Electrical Impedance Tomography (EIT) during mechanical ventilation

    NASA Astrophysics Data System (ADS)

    Nebuya, Satoru; Koike, Tomotaka; Imai, Hiroshi; Noshiro, Makoto; Brown, Brian H.; Soma, Kazui

    2010-04-01

    The consistency of regional lung density measurements as estimated by Electrical Impedance Tomography (EIT), in eleven patients supported by a mechanical ventilator, was validated to verify the feasibility of its use in intensive care medicine. There were significant differences in regional lung densities between the normal lung and diseased lungs associated with pneumonia, atelectasis and pleural effusion (Steel-Dwass test, p < 0.05). Temporal changes in regional lung density of patients with atelectasis were observed to be in good agreement with the results of clinical diagnosis. These results indicate that it is feasible to obtain a quantitative value for regional lung density using EIT.

  3. Diffraction correction for precision surface acoustic wave velocity measurements

    NASA Astrophysics Data System (ADS)

    Ruiz M., Alberto; Nagy, Peter B.

    2002-09-01

    Surface wave dispersion measurements can be used to nondestructively characterize shot-peened, laser shock-peened, burnished, and otherwise surface-treated specimens. In recent years, there have been numerous efforts to separate the contribution of surface roughness from those of near-surface material variations, such as residual stress, texture, and increased dislocation density. As the accuracy of the dispersion measurements was gradually increased using state-of-the-art laser-ultrasonic scanning and sophisticated digital signal processing methods, it was recognized that a perceivable dispersive effect, similar to the one found on rough shot-peened specimens, is exhibited by untreated smooth surfaces as well. This dispersion effect is on the order of 0.1%, that is significantly higher than the experimental error associated with the measurements and comparable to the expected velocity change produced by near-surface compressive residual stresses in metals below their yield point. This paper demonstrates that the cause of this apparent dispersion is the diffraction of the surface acoustic wave (SAW) as it travels over the surface of the specimen. The results suggest that a diffraction correction may be introduced to increase the accuracy of surface wave dispersion measurements. A simple diffraction correction model was developed for surface waves and this correction was subsequently validated by laser-interferometric velocity measurements on aluminum specimens. copyright 2002 Acoustical Society of America.

  4. Impedance measurements on a spiral-wound nickel/metal hydride cell cycled in a simulated Leo orbit

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1993-01-01

    A spiral-wound size C cell was cycled at 25 C in a low earth orbit (LEO) regime at 50 percent depth of discharge (DOD) with approximately five percent over-charge. The nominal capacity was 3.5 AH. The cell was cycled for 2000 cycles. Capacity checks and impedance measurements over the complete range of state of charge were made upon receipt and after 500, 1000, and 2000 cycles. The capacity of the cell was essentially unchanged until after the impedance measurements at 2000 cycles. Only small changes in the impedance parameters were observed, but there was somewhat more scatter in the data after 2000 cycles. When the cell was returned to LEO cycling after 2000 cycles, only 38 percent of the capacity could be obtained. It is believed that the cell failed because of an equipment failure at the end of the final impedance measurements which allowed an over-discharge.

  5. Considerations on electrical impedance measurements of electrolyte solutions in a four-electrode cell

    NASA Astrophysics Data System (ADS)

    Chaparro, C. V.; Herrera, L. V.; Meléndez, A. M.; Miranda, D. A.

    2016-02-01

    A tetrapolar probe to measure the electrical properties of electrolyte solutions was implemented with gold electrodes according to the van der Pauw method. Electrical impedance spectroscopy (EIS) measurements of different concentrations of phosphate buffer saline (PBS) solution and an oral mucosal tissue sample dispersed in PBS were performed in the galvanostatic mode using a four-electrode cell (tetrapolar probe). Taking advantage of using a potentiostat/galvanostat for carrying out the electrical measurements, a simple and rapid method using a three-electrode electrochemical cell is described for: a) cleaning of electrodes, b) verification of surface chemical state of electrode material and c) choice of current supplied to electrodes for EIS measurements. Results of this research shown a depolarization effect due to the addition of oral mucosa tissue cells into the PBS solution.

  6. Validation of bioelectrical-impedance analysis as a measurement of change in body composition in obesity

    SciTech Connect

    Kushner, R.F.; Kunigk, A.; Alspaugh, M.; Andronis, P.T.; Leitch, C.A.; Schoeller, D.A. )

    1990-08-01

    The bioelectrical-impedance-analysis (BIA) method accurately measures body composition in weight-stable subjects. This study validates the use of BIA to measure change in body composition. Twelve obese females underwent weight loss at a mean rate of 1.16 kg/wk. Body composition was measured by deuterium oxide dilution (D2O), BIA, and skinfold anthropometry (SFA) at baseline and at 5% decrements in weight. Highly significant correlations were obtained between D2O and BIA (r = 0.971) and between D2O and SFA (r = 0.932). Overall, BIA predicted change in fat-free mass with greater accuracy (to 0.4 kg) and precision (+/- 1.28 kg) than did anthropometry (to 0.8 kg and +/- 2.58 kg, respectively). We conclude that BIA is a useful clinical method for measuring change in body composition.

  7. Multifrequency impedance measurement technique for wireless characterization of microbiological cell cultures

    NASA Astrophysics Data System (ADS)

    Wissenwasser, J.; Vellekoop, M. J.; Kapferer, W.; Lepperdinger, G.; Heer, R.

    2011-11-01

    An impedance measurement system with probe signal frequencies up to 50 kHz with AC-probe voltages below 30 mV rms was integrated for wireless and battery-free monitoring of microbiological cell cultures. The here presented modular design and the use of state-of-the-art components greatly eases adoptions to a wide range of biotechnological applications without the need of bulky LCR-meters or potentiostats. The device had a power consumption of less than 2.5 mA at a 3.3 V single power supply and worked trouble-free within the humid environment of a cell culture incubator. Measurements on lumped RC-elements showed an error of less than 1% for absolute values and less than 1° regarding the phase of the complex impedance. The performance of sensor devices with interdigitated electrode structures for the measurement of adherent cell cultures was tested in the presence of phosphate-buffered saline solution in the humid atmosphere of an incubator for biological cell cultures.

  8. Multifrequency impedance measurement technique for wireless characterization of microbiological cell cultures.

    PubMed

    Wissenwasser, J; Vellekoop, M J; Kapferer, W; Lepperdinger, G; Heer, R

    2011-11-01

    An impedance measurement system with probe signal frequencies up to 50 kHz with AC-probe voltages below 30 mV rms was integrated for wireless and battery-free monitoring of microbiological cell cultures. The here presented modular design and the use of state-of-the-art components greatly eases adoptions to a wide range of biotechnological applications without the need of bulky LCR-meters or potentiostats. The device had a power consumption of less than 2.5 mA at a 3.3 V single power supply and worked trouble-free within the humid environment of a cell culture incubator. Measurements on lumped RC-elements showed an error of less than 1% for absolute values and less than 1° regarding the phase of the complex impedance. The performance of sensor devices with interdigitated electrode structures for the measurement of adherent cell cultures was tested in the presence of phosphate-buffered saline solution in the humid atmosphere of an incubator for biological cell cultures.

  9. Photo-acoustic tomography in a rotating measurement setting

    NASA Astrophysics Data System (ADS)

    Bal, Guillaume; Moradifam, Amir

    2016-10-01

    Photo-acoustic tomography (PAT) aims to leverage the photo-acoustic coupling between optical absorption of light sources and ultrasound (US) emission to obtain high contrast reconstructions of optical parameters with the high resolution of sonic waves. Quantitative PAT often involves a two-step procedure: first the map of sonic emission is reconstructed from US boundary measurements; and second optical properties of biological tissues are evaluated. We consider here a practical measurement setting in which such a separation does not apply. We assume that the optical source and an array of ultrasonic transducers are mounted on a rotating frame (in two or three dimensions) so that the light source rotates at the same time as the US measurements are acquired. As a consequence, we no longer have the option to reconstruct a map of sonic emission corresponding to a given optical illumination. We propose here a framework where the two steps are combined into one and an absorption map is directly reconstructed from the available US measurements.

  10. Compensating for ear-canal acoustics when measuring otoacoustic emissions.

    PubMed

    Charaziak, Karolina K; Shera, Christopher A

    2017-01-01

    Otoacoustic emissions (OAEs) provide an acoustic fingerprint of the inner ear, and changes in this fingerprint may indicate changes in cochlear function arising from efferent modulation, aging, noise trauma, and/or exposure to harmful agents. However, the reproducibility and diagnostic power of OAE measurements is compromised by the variable acoustics of the ear canal, in particular, by multiple reflections and the emergence of standing waves at relevant frequencies. Even when stimulus levels are controlled using methods that circumvent standing-wave problems (e.g., forward-pressure-level calibration), distortion-product otoacoustic emission (DPOAE) levels vary with probe location by 10-15 dB near half-wave resonant frequencies. The method presented here estimates the initial outgoing OAE pressure wave at the eardrum from measurements of the conventional OAE, allowing one to separate the emitted OAE from the many reflections trapped in the ear canal. The emitted pressure level (EPL) represents the OAE level that would be recorded were the ear canal replaced by an infinite tube with no reflections. When DPOAEs are expressed using EPL, their variation with probe location decreases to the test-retest repeatability of measurements obtained at similar probe positions. EPL provides a powerful way to reduce the variability of OAE measurements and improve their ability to detect cochlear changes.

  11. Acoustic measurement of the Deepwater Horizon Macondo well flow rate

    PubMed Central

    Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M.; Techet, Alexandra H.; Yoerger, Dana R.; Whitcomb, Louis L.; Seewald, Jeffrey S.; Sylva, Sean P.; Fenwick, Judith

    2012-01-01

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well’s two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well’s oil flow rate was approximately 0.10 ± 0.017 m3 s-1 at seafloor conditions, or approximately 85 ± 15 kg s-1 (7.4 ± 1.3 Gg d-1), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s-1 (2.1 ± 0.37 Gg d-1) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s-1 (9.5 ± 1.6 Gg d-1). PMID:21903931

  12. Acoustic measurement of the Deepwater Horizon Macondo well flow rate.

    PubMed

    Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M; Techet, Alexandra H; Yoerger, Dana R; Whitcomb, Louis L; Seewald, Jeffrey S; Sylva, Sean P; Fenwick, Judith

    2012-12-11

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well's two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well's oil flow rate was approximately 0.10 ± 0.017 m(3) s(-1) at seafloor conditions, or approximately 85 ± 15 kg s(-1) (7.4 ± 1.3 Gg d(-1)), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s(-1) (2.1 ± 0.37 Gg d(-1)) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s(-1) (9.5 ± 1.6 Gg d(-1)).

  13. Measurement of stiffness of standing trees and felled logs using acoustics: A review.

    PubMed

    Legg, Mathew; Bradley, Stuart

    2016-02-01

    This paper provides a review on the use of acoustics to measure stiffness of standing trees, stems, and logs. An outline is given of the properties of wood and how these are related to stiffness and acoustic velocity throughout the tree. Factors are described that influence the speed of sound in wood, including the different types of acoustic waves which propagate in tree stems and lumber. Acoustic tools and techniques that have been used to measure the stiffness of wood are reviewed. The reasons for a systematic difference between direct and acoustic measurements of stiffness for standing trees, and methods for correction, are discussed. Other techniques, which have been used in addition to acoustics to try to improve stiffness measurements, are also briefly described. Also reviewed are studies which have used acoustic tools to investigate factors that influence the stiffness of trees. These factors include different silvicultural practices, geographic and environmental conditions, and genetics.

  14. Measurement of food texture by an acoustic vibration method

    NASA Astrophysics Data System (ADS)

    Sakurai, Naoki; Taniwaki, Mitsuru; Iwatani, Shin-ichiro; Akimoto, Hidemi

    2011-09-01

    Food texture was measured by a new acoustic vibration method. A piezoelectric sensor sandwiched between a probe and piston was inserted into a food sample by delivery of silicon oil to a cylinder by a pump. Vibration emitted from the food sample on insertion of the probe was monitored by voltage outputs of the sensor. The voltage signals were passed through 19 half octave bands to calculate texture index for each band. The texture index was defined as vibration energy of the probe caused by the food rupture and/or breakage per unit time.

  15. Passive Wake Acoustics Measurements at Denver International Airport

    NASA Technical Reports Server (NTRS)

    Wang, Frank Y.; Wassaf, Hadi; Dougherty, Robert P.; Clark, Kevin; Gulsrud, Andrew; Fenichel, Neil; Bryant, Wayne H.

    2004-01-01

    From August to September 2003, NASA conducted an extensive measurement campaign to characterize the acoustic signal of wake vortices. A large, both spatially as well as in number of elements, phased microphone array was deployed at Denver International Airport for this effort. This paper will briefly describe the program background, the microphone array, as well as the supporting ground-truth and meteorological sensor suite. Sample results to date are then presented and discussed. It is seen that, in the frequency range processed so far, wake noise is generated predominantly from a very confined area around the cores.

  16. Body fat measurement by bioelectrical impedance and air displacement plethysmography: a cross-validation study to design bioelectrical impedance equations in Mexican adults

    PubMed Central

    Macias, Nayeli; Alemán-Mateo, Heliodoro; Esparza-Romero, Julián; Valencia, Mauro E

    2007-01-01

    Background The study of body composition in specific populations by techniques such as bio-impedance analysis (BIA) requires validation based on standard reference methods. The aim of this study was to develop and cross-validate a predictive equation for bioelectrical impedance using air displacement plethysmography (ADP) as standard method to measure body composition in Mexican adult men and women. Methods This study included 155 male and female subjects from northern Mexico, 20–50 years of age, from low, middle, and upper income levels. Body composition was measured by ADP. Body weight (BW, kg) and height (Ht, cm) were obtained by standard anthropometric techniques. Resistance, R (ohms) and reactance, Xc (ohms) were also measured. A random-split method was used to obtain two samples: one was used to derive the equation by the "all possible regressions" procedure and was cross-validated in the other sample to test predicted versus measured values of fat-free mass (FFM). Results and Discussion The final model was: FFM (kg) = 0.7374 * (Ht2 /R) + 0.1763 * (BW) - 0.1773 * (Age) + 0.1198 * (Xc) - 2.4658. R2 was 0.97; the square root of the mean square error (SRMSE) was 1.99 kg, and the pure error (PE) was 2.96. There was no difference between FFM predicted by the new equation (48.57 ± 10.9 kg) and that measured by ADP (48.43 ± 11.3 kg). The new equation did not differ from the line of identity, had a high R2 and a low SRMSE, and showed no significant bias (0.87 ± 2.84 kg). Conclusion The new bioelectrical impedance equation based on the two-compartment model (2C) was accurate, precise, and free of bias. This equation can be used to assess body composition and nutritional status in populations similar in anthropometric and physical characteristics to this sample. PMID:17697388

  17. Wide-Range Filter-Based Sinusoidal Wave Synthesizer for Electrochemical Impedance Spectroscopy Measurements.

    PubMed

    Chia-Ling Wei; Yi-Wen Wang; Bin-Da Liu

    2014-06-01

    A filter-based wide-range programmable sinusoidal wave synthesizer for electrochemical impedance spectroscopy measurement is proposed. The adopted filter is implemented with switched-capacitor circuits, so its corner frequency is accurate and adjustable by changing its switching frequency. The proposed sine wave synthesizer is implemented by using a 0.35 μm 2P4M 3.3 V mixed-signal polycide process. According to the measured results, the output frequency of the proposed synthesizer is 40 mHz-40 kHz . The measured total harmonic distortion is 0.073% at 10 Hz and 0.075% at 10 kHz, both of which are better than that of a typical function generator.

  18. AN ADVANCED CALIBRATION PROCEDURE FOR COMPLEX IMPEDANCE SPECTRUM MEASUREMENTS OF ADVANCED ENERGY STORAGE DEVICES

    SciTech Connect

    William H. Morrison; Jon P. Christophersen; Patrick Bald; John L. Morrison

    2012-06-01

    With the increasing demand for electric and hybrid electric vehicles and the explosion in popularity of mobile and portable electronic devices such as laptops, cell phones, e-readers, tablet computers and the like, reliance on portable energy storage devices such as batteries has likewise increased. The concern for the availability of critical systems in turn drives the availability of battery systems and thus the need for accurate battery health monitoring has become paramount. Over the past decade the Idaho National Laboratory (INL), Montana Tech of the University of Montana (Tech), and Qualtech Systems, Inc. (QSI) have been developing the Smart Battery Status Monitor (SBSM), an integrated battery management system designed to monitor battery health, performance and degradation and use this knowledge for effective battery management and increased battery life. Key to the success of the SBSM is an in-situ impedance measurement system called the Impedance Measurement Box (IMB). One of the challenges encountered has been development of an accurate, simple, robust calibration process. This paper discusses the successful realization of this process.

  19. Simultaneous Measurements of Ossicular Velocity and Intracochlear Pressure Leading to the Cochlear Input Impedance in Gerbil

    PubMed Central

    Decraemer, W. F.; Khanna, S. M.; Olson, E. S.

    2008-01-01

    Recent measurements of three-dimensional stapes motion in gerbil indicated that the piston component of stapes motion was the primary contributor to intracochlear pressure. In order to make a detailed correlation between stapes piston motion and intracochlear pressure behind the stapes, simultaneous pressure and motion measurements were undertaken. We found that the scala vestibuli pressure followed the piston component of the stapes velocity with high fidelity, reinforcing our previous finding that the piston motion of the stapes was the main stimulus to the cochlea. The present data allowed us to calculate cochlear input impedance and power flow into the cochlea. Both the amplitude and phase of the impedance were quite flat with frequency from 3 kHz to at least 30 kHz, with a phase that was primarily resistive. With constant stimulus pressure in the ear canal the intracochlear pressure at the stapes has been previously shown to be approximately flat with frequency through a wide range, and coupling that result with the present findings indicates that the power that flows into the cochlea is quite flat from about 3 to 30 kHz. The observed wide-band intracochlear pressure and power flow are consistent with the wide-band audiogram of the gerbil. PMID:18459001

  20. Electrical-Impedance Tomography for Measuring Material Distributions of Multiphase Flows in Conducting Vessels

    NASA Astrophysics Data System (ADS)

    Liter, S. G.; Torczynski, J. R.; Shollenberger, K. A.; Ceccio, S. L.

    2001-11-01

    An implementation of resistive electrical-impedance tomography (EIT) for measuring material distributions of two-phase flows in vessels with electrically conducting walls is presented. A thin nonconducting rod, with N-1 ring electrodes wrapped around its exterior at equally-spaced axial positions, is inserted into the vessel (i.e., into the interior of the flow). The vessel wall is grounded and serves as the N-th electrode. Current is injected from a ring electrode and exits to the vessel wall, and the resulting voltages at all ring electrodes are recorded. Each ring electrode is used in turn for current injection, and the collection of all measured voltages comprises a data set. Multiple data sets are used to numerically reconstruct the time-averaged impedance distribution within the vessel, from which the material distribution is inferred. Design issues, including the size, spacing, and number of the ring electrodes, are considered. An experiment in which the rod is inserted coaxially into a vertical pipe is presented, and bubble-column applications are discussed. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

  1. Simulation method for cardiac stroke volume estimation by intracardiac electrical impedance measurement.

    PubMed

    Barak, C; Leviatan, Y; Inbar, G F; Hoekstein, K N

    1992-09-01

    Using the electrical impedance measurement technique to investigate stroke volume estimation, three models of the ventricle were simulated. A four-electrode impedance catheter was used; two electrodes to set up an electric field in the model and the other two to measure the potential difference. A new approach, itself an application of the quasi-static case of a method used to solve electromagnetic field problems, was used to solve the electric field in the model. The behaviour of the estimation is examined with respect to the electrode configuration on the catheter and to catheter location with respect to the ventricle walls. Cardiac stroke volume estimation was found to be robust to catheter location generating a 10 per cent error for an offset of 40 per cent of the catheter from the chamber axis and rotation of 20 degrees with respect to the axis. The electrode configuration has a dominant effect on the sensitivity and accuracy of the estimation. Certain configurations gave high accuracy, whereas in others high sensitivity was found with lower accuracy. This led to the conclusion that the electrode configuration should be carefully chosen according to the desired criteria.

  2. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

    2004-06-16

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 0.1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002, Tseng et al., 2003). Electric and magnetic sensors are being tested and calibrated on sea water and in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  3. High Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Framgos, William

    1999-06-01

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  4. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

    2002-11-20

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  5. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen; Choi, Youngki

    2001-06-10

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  6. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring, and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex

    2000-06-01

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach (Song et al., 1997). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  7. Intracellular Impedance Measurements Reveal Non-ohmic Properties of the Extracellular Medium around Neurons

    PubMed Central

    Gomes, Jean-Marie; Bédard, Claude; Valtcheva, Silvana; Nelson, Matthew; Khokhlova, Vitalia; Pouget, Pierre; Venance, Laurent; Bal, Thierry; Destexhe, Alain

    2016-01-01

    Determining the electrical properties of the extracellular space around neurons is important for understanding the genesis of extracellular potentials, as well as for localizing neuronal activity from extracellular recordings. However, the exact nature of these extracellular properties is still uncertain. Here, we introduce a method to measure the impedance of the tissue, one that preserves the intact cell-medium interface using whole-cell patch-clamp recordings in vivo and in vitro. We find that neural tissue has marked non-ohmic and frequency-filtering properties, which are not consistent with a resistive (ohmic) medium, as often assumed. The amplitude and phase profiles of the measured impedance are consistent with the contribution of ionic diffusion. We also show that the impact of such frequency-filtering properties is possibly important on the genesis of local field potentials, as well as on the cable properties of neurons. These results show non-ohmic properties of the extracellular medium around neurons, and suggest that source estimation methods, as well as the cable properties of neurons, which all assume ohmic extracellular medium, may need to be reevaluated. PMID:26745426

  8. Determination of rotor harmonic blade loads from acoustic measurements

    NASA Technical Reports Server (NTRS)

    Kasper, P. K.

    1975-01-01

    The magnitude of discrete frequency sound radiated by a rotating blade is strongly influenced by the presence of a nonuniform distribution of aerodynamic forces over the rotor disk. An analytical development and experimental results are provided for a technique by which harmonic blade loads are derived from acoustic measurements. The technique relates, on a one-to-one basis, the discrete frequency sound harmonic amplitudes measured at a point on the axis of rotation to the blade-load harmonic amplitudes. This technique was applied to acoustic data from two helicopter types and from a series of test results using the NASA-Langley Research Center rotor test facility. The inferred blade-load harmonics for the cases considered tended to follow an inverse power law relationship with harmonic blade-load number. Empirical curve fits to the data showed the harmonic fall-off rate to be in the range of 6 to 9 db per octave of harmonic order. These empirical relationships were subsequently used as input data in a compatible far field rotational noise prediction model. A comparison between predicted and measured off-axis sound harmonic levels is provided for the experimental cases considered.

  9. Analysis of acoustic reduction using spectral similarity measures.

    PubMed

    Hämäläinen, Annika; Gubian, Michele; ten Bosch, Louis; Boves, Lou

    2009-12-01

    Articulatory and acoustic reduction can manifest itself in the temporal and spectral domains. This study introduces a measure of spectral reduction, which is based on the speech decoding techniques commonly used in automatic speech recognizers. Using data for four frequent Dutch affixes from a large corpus of spontaneous face-to-face conversations, it builds on an earlier study examining the effects of lexical frequency on durational reduction in spoken Dutch [Pluymaekers, M. et al. (2005). J. Acoust. Soc. Am. 118, 2561-2569], and compares the proposed measure of spectral reduction with duration as a measure of reduction. The results suggest that the spectral reduction scores capture other aspects of reduction than duration. While duration can--albeit to a moderate degree--be predicted by a number of linguistically motivated variables (such as word frequency, segmental context, and speech rate), the spectral reduction scores cannot. This suggests that the spectral reduction scores capture information that is not directly accounted for by the linguistically motivated variables. The results also show that the spectral reduction scores are able to predict a substantial amount of the variation in duration that the linguistically motivated variables do not account for.

  10. Ionosphere plasma electron parameters from radio frequency sweeping impedance probe measurements

    NASA Astrophysics Data System (ADS)

    Spencer, E.; Patra, S.

    2015-09-01

    In this work we will describe the technique of using an RF sweeping impedance probe (SIP) to measure the AC impedance of an electrically short monopole immersed in a plasma. We analyze the SIP measurements which are taken from the payload of the Storms sounding rocket, launched from Wallops Island, Virginia, in 2007. The scientific objective of the Storms mission was to concentrate on whether density irregularities observed in midlatitude spread F could arise from ionospheric coupling to terrestrial weather. As such, independent measurements of the electron density profile are crucial. Since the inherent nature of the SIP technique makes it relatively insensitive to errors introduced through spacecraft charging, probe contamination, and other DC effects, it is an ideal instrument to employ under disturbed plasma conditions. The instrument measures both the magnitude and phase of the AC impedance from 100 kHz to 20 MHz in 128 frequency steps, performing 45,776 sweeps over the entire flight. From these measurements we infer both the absolute electron density ne and the electron neutral collision frequencies νen throughout the flight trajectory. The SIP data can be approximately analyzed using a fluid formulation and thin sheath approximation particularly at altitudes below 200 km, which allows us to match the measurements to quasi-static analytical formulas. At about 265 km on the upleg, the magnitude data transitioned to a highly damped response with increasing altitude. The phase data, on the other hand, continued to indicate increased plasma density and reduced collisionality as expected. For a large portion of the flight, the payload of the Storms mission exhibited an uncontrolled coning motion, making the local magnetic field orientation with respect to the dipole difficult to decipher. Despite these difficulties, we were able to obtain robust estimates of the electron density profile, using the phase information from each sweep. In addition, the electron

  11. Effects of metoclopramide on gastric motility measured by short-term bio-impedance

    PubMed Central

    Huerta-Franco, María-Raquel; Vargas-Luna, Miguel; Capaccione, Kathleen M; Yañez-Roldán, Etna; Hernández-Ledezma, Ulises; Morales-Mata, Ismael; Córdova-Fraga, Teodoro

    2009-01-01

    AIM: To analyze the accuracy of short-term bio-impedance as a means of measuring gastric motility. METHODS: We evaluated differences in the short-term electrical bio-impedance signal from the gastric region in the following conditions: (1) fasting state, (2) after the administration of metoclopramide (a drug that induces an increase in gastric motility) and (3) after food ingestion in 23 healthy volunteers. We recorded the real component of the electrical impedance signal from the gastric region for 1000 s. We performed a Fast Fourier Transform (FFT) on this data and then compared the signal among the fasting, medicated, and postprandial conditions using the median of the area under the curve, the relative area under the curve and the main peak activity. RESULTS: The median of the area under the curve of the frequency range in the region between 2-8 cycles per minute (cpm) decreased from 4.7 cpm in the fasting condition to 4.0 cpm in the medicated state (t = 3.32, P = 0.004). This concurred with the decrease seen in the relative area under the FFT curve in the region from 4 to 8 cpm from 38.3% to 26.6% (t = 2.81, P = 0.012) and the increase in area in the region from 2 to 4 cpm from 22.4% to 27.7%, respectively (t = -2.5, P = 0.022). Finally the main peak position also decreased in the region from 2 to 8 cpm. Main peak activity in the fasting state was 4.72 cpm and declined to 3.45 cpm in the medicated state (t = 2.47, P = 0.025). There was a decrease from the fasting state to the postprandial state at 3.02 cpm (t = 4.0, P = 0.0013). CONCLUSION: Short-term electrical bio-impedance can assess gastric motility changes in individuals experiencing gastric stress by analyzing the area medians and relative areas under the FFT curve. PMID:19824108

  12. Wideband acoustic immittance measures: developmental characteristics (0 to 12 months).

    PubMed

    Kei, Joseph; Sanford, Chris A; Prieve, Beth A; Hunter, Lisa L

    2013-07-01

    Rapid developmental changes of the peripheral auditory system in normal infants occur in the first year of life. Specifically, the postnatal development of the external and middle ear affects all measures of external and middle ear function including wideband acoustic immittance(WAI). This article provides an overview of WAI studies in newborns and infants from a developmental perspective. Normative WAI data in newborns are fairly consistent across studies. However, there are discrepancies in some WAI measures between studies, possibly due to differences in sampling, methodology, and instrumentation. Accuracy of WAI measurements is compromised when a good probe seal cannot be maintained during testing or an inaccurate estimate of the cross-sectional area of the ear canal of newborns occurs. Comparison of WAI data between age groups from 0 to 12 months reveals maturation effects. Additional age-specific longitudinal and cross-sectional normative WAI data for infants from birth to 12 months are required to validate and consolidate existing data.

  13. Classification of heart valve condition using acoustic measurements

    SciTech Connect

    Clark, G.

    1994-11-15

    Prosthetic heart valves and the many great strides in valve design have been responsible for extending the life spans of many people with serious heart conditions. Even though the prosthetic valves are extremely reliable, they are eventually susceptible to long-term fatigue and structural failure effects expected from mechanical devices operating over long periods of time. The purpose of our work is to classify the condition of in vivo Bjork-Shiley Convexo-Concave (BSCC) heart valves by processing acoustic measurements of heart valve sounds. The structural failures of interest for Bscc valves is called single leg separation (SLS). SLS can occur if the outlet strut cracks and separates from the main structure of the valve. We measure acoustic opening and closing sounds (waveforms) using high sensitivity contact microphones on the patient`s thorax. For our analysis, we focus our processing and classification efforts on the opening sounds because they yield direct information about outlet strut condition with minimal distortion caused by energy radiated from the valve disc.

  14. Turbulent Diffusivity under High Winds from Acoustic Measurements of Bubbles

    NASA Astrophysics Data System (ADS)

    Wang, D. W.; Wijesekera, H. W.; Jarosz, E.; Teague, W. J.; Pegau, W. S.

    2015-12-01

    Breaking surface waves generate layers of bubble clouds as air parcels entrain into the upper-ocean by the action of turbulent motions. The turbulent diffusivity in the bubble cloud layer was investigated by combining measurements of surface winds, waves, bubble acoustic backscatter, currents, and hydrography. These measurements were made at water depths of 60-90 m on the shelf of the Gulf of Alaska near Kayak Island during late December 2012, a period where the ocean was experiencing winds and significant wave heights up to 22 m s-1 and 9 m, respectively. Vertical profiles of acoustic backscatter decayed exponentially from the wave surface with e-folding lengths of about 0.6 to 6 m, while the bubble penetration depths were about 3 to 30 m. Both e-folding lengths and bubble depths were highly correlated with surface wind and wave conditions. The turbulent diffusion coefficients, inferred from e-folding length and bubble depth, varied from about 0.01 m2 s-1 to 0.4 m2 s-1. Our analysis suggests that the turbulent diffusivity in the bubble layer can be parameterized as a function of the cube of the wind friction velocity with a proportionality coefficient that depends weakly on wave age. Furthermore, in the bubble layer, on average, the shear production of the turbulent kinetic energy estimated by the diffusion coefficients was a similar order magnitude as the dissipation rate predicted by the wall boundary-layer theory.

  15. Measurements of Low-Frequency Acoustic Attenuation in Soils.

    DTIC Science & Technology

    2007-11-02

    Engineering Research Laboratory to design an acoustic subsurface imaging system, a set of experiments was conducted in which the attenuation and the velocity...support of the U.S. Army Construction Engineering Research Laboratory’s efforts to design an acoustic subsurface imaging system which would ideally be...of acoustic waves such as those generated by a subsurface imaging system. An experiment reported in the literature characterized the acoustic

  16. Traveling-wave electrokinetic micropumps: velocity, electrical current, and impedance measurements.

    PubMed

    García-Sánchez, P; Ramos, A; Green, N G; Morgan, H

    2008-09-02

    An array of microelectrodes covered in an electrolyte and energized by a traveling-wave potential produces net movement of the fluid. Arrays of platinum microelectrodes of two different characteristic sizes have been studied. For both sizes of arrays, at low voltages (<2 V pp) the electrolyte flow is in qualitative agreement with the linear theory of ac electroosmosis. At voltages above a threshold, the direction of fluid flow is reversed. The electrical impedance of the electrode-electrolyte system was measured after the experiments, and changes in the electrical properties of the electrolyte were observed. Measurements of the electrical current during pumping of the electrolyte are also reported. Transient behaviors in both electrical current and fluid velocity were observed. The Faradaic currents probably generate conductivity gradients in the liquid bulk, which in turn give rise to electrical forces. These effects are discussed in relation to the fluid flow observations.

  17. Biological impedance cross evaluation and imaging from composite measurements of magnetic and electrical methods.

    PubMed

    Ran, Peng; Xiao, Xiaoming; He, Wei; Li, Zhangyong

    2015-01-01

    Because of the need for rapid detection and location of diseases in clinical applications, this work proposes a composite measurement of magnetic induction tomography (MIT) and electrical impedance tomography (EIT). This paper is composed of the following aspects: portable and integral hardware design, stable dual constant-current sources, the composite detection method, cross-plane data acquirement, 3-dimensional image reconstruction and so on. A qualitative evaluation of conductivity, resolution and relative position error were taken by combining the EIT and MIT methods via the experiment model. The sensitivities of both methods were analyzed to improve the imaging results. The reconstruction results reveal that the system is capable of obtaining better physiological measurements, which is very useful in clinical monitoring, quick medical diagnosing and preliminary screening of community health.

  18. Estimation of Metabolism Characteristics for Heat-Injured Bacteria Using Dielectrophoretic Impedance Measurement Method

    NASA Astrophysics Data System (ADS)

    Amako, Eri; Enjoji, Takaharu; Uchida, Satoshi; Tochikubo, Fumiyoshi

    Constant monitoring and immediate control of fermentation processes have been required for advanced quality preservation in food industry. In the present work, simple estimation of metabolic states for heat-injured Escherichia coli (E. coli) in a micro-cell was investigated using dielectrophoretic impedance measurement (DEPIM) method. Temporal change in the conductance between micro-gap (ΔG) was measured for various heat treatment temperatures. In addition, the dependence of enzyme activity, growth capacity and membrane situation for E. coli on heat treatment temperature was also analyzed with conventional biological methods. Consequently, a correlation between ΔG and those biological properties was obtained quantitatively. This result suggests that DEPIM method will be available for an effective monitoring technique for complex change in various biological states of microorganisms.

  19. Focused Impedance Method (FIM) and Pigeon Hole Imaging (PHI) for localized measurements - a review

    NASA Astrophysics Data System (ADS)

    Siddique-e Rabbani, K.

    2010-04-01

    This paper summarises up to date development in Focused Impedance Method (FIM) initiated by us. It basically involves taking the sum of two orthogonal tetra-polar impedance measurements around a common central region, giving a localized enhanced sensitivity. Although the basic idea requires 8 electrodes, versions with 6- and 4-electrodes were subsequently conceived and developed. The focusing effect has been verified in 2D and 3D phantoms and through numerical analysis. Dynamic stomach emptying, and ventilation of localized lung regions have been studied successfully suggesting further applications in monitoring of gastric acid secretion, artificial respiration, bladder emptying, etc. Multi-frequency FIM may help identify some diseases and disorders including certain cancers. FIM, being much simpler and having less number of electrodes, appears to have the potential to replace EIT for applications involving large and shallow organs. An enhancement of 6-electrode FIM led to Pigeon Hole Imaging (PHI) in a square matrix through backprojection in two orthogonal directions, good for localising of one or two well separated objects.

  20. Measurement of lean body mass using bioelectrical impedance analysis: a consideration of the pros and cons.

    PubMed

    Sergi, Giuseppe; De Rui, Marina; Stubbs, Brendon; Veronese, Nicola; Manzato, Enzo

    2016-08-27

    The assessment of body composition has important applications in the evaluation of nutritional status and estimating potential health risks. Bioelectrical impedance analysis (BIA) is a valid method for the assessment of body composition. BIA is an alternative to more invasive and expensive methods like dual-energy X-ray absorptiometry, computerized tomography, and magnetic resonance imaging. Bioelectrical impedance analysis is an easy-to-use and low-cost method for the estimation of fat-free mass (FFM) in physiological and pathological conditions. The reliability of BIA measurements is influenced by various factors related to the instrument itself, including electrodes, operator, subject, and environment. BIA assumptions beyond its use for body composition are the human body is empirically composed of cylinders, FFM contains virtually all the water and conducting electrolytes in the body, and its hydration is constant. FFM can be predicted by BIA through equations developed using reference methods. Several BIA prediction equations exist for the estimation of FFM, skeletal muscle mass (SMM), or appendicular SMM. The BIA prediction models differ according to the characteristics of the sample in which they have been derived and validated in addition to the parameters included in the multiple regression analysis. In choosing BIA equations, it is important to consider the characteristics of the sample in which it has been developed and validated, since, for example, age- and ethnicity-related differences could sensitively affect BIA estimates.

  1. Precision stress measurements in severe shock-wave environments with low-impedance manganin gauges

    NASA Astrophysics Data System (ADS)

    Vantine, H.; Chan, J.; Erickson, L.; Janzen, J.; Weingart, R.; Lee, R.

    1980-01-01

    New techniques that permit the use of low-impedance manganin stress gauges in chemically reacting shock waves in the 1.0-40.0 GPa range are described. The rugged, small, and fast response gauge has reproducibility better than 2% when used in conjunction with a pulsed bridge circuit and adjustable, current-regulated power supplies. Techniques are presented for fabricating the transducer package, calibrating the bridge circuit and oscilloscopes, designing the drive system, and reducing the data. Data are presented for planar impact experiments performed with a 102-mm gas gun on high-explosive samples. In particular, the Chapman-Jouguet pressure in the explosive RX03-BB /92.5% triaminotrinitrobenzene (TATB)/7.5% polychlorotrifluoroethylene (Kel-F binder)/ was directly measured to be 28.2 plus or minus 0.6 GPa. These new developments open the possibility of applying low-impedance manganin gauges in chemically reactive hydrodynamic flows such as the evolution of a shock wave into a detonation wave.

  2. Modeling and Measuring Acoustic Backscatter from Fish Aggregations

    DTIC Science & Technology

    1999-09-30

    of the abundance, spatial distribution, schooling behaviour and acoustic backscatter of the Namibian pilchard. Cruise Report 99-4, Dr. Fridtjof ... Nansen . 103 pp. Rudstam, L, Horne, J., Fleischer, G. Report from the Great Lakes Acoustic Workshop III: Translation of acoustic data to fish abundance

  3. A new application of electrical impedance spectroscopy for measuring glucose metabolism: a phantom study

    NASA Astrophysics Data System (ADS)

    Dhurjaty, Sreeram; Qiu, Yuchen; Tan, Maxine; Liu, Hong; Zheng, Bin

    2015-03-01

    Glucose metabolism relates to biochemical processes in living organisms and plays an important role in diabetes and cancer-metastasis. Although many methods are available for measuring glucose metabolism-activities, from simple blood tests to positron emission tomography, currently there is no robust and affordable device that enables monitoring of glucose levels in real-time. In this study we tested feasibility of applying a unique resonance-frequency based electronic impedance spectroscopy (REIS) device that has been, recently developed to measure and monitor glucose metabolism levels using a phantom study. In this new testing model, a multi-frequency electrical signal sequence is applied and scanned through the subject. When the positive reactance of an inductor inside the device cancels out the negative reactance of the capacitance of the subject, the electrical impedance reaches a minimum value and this frequency is defined as the resonance frequency. The REIS system has a 24-bit analog-to-digital signal convertor and a frequency-resolution of 100Hz. In the experiment, two probes are placed inside a 100cc container initially filled with distilled water. As we gradually added liquid-glucose in increments of 1cc (250mg), we measured resonance frequencies and minimum electrical signal values (where A/D was normalized to a full scale of 1V). The results showed that resonance frequencies monotonously decreased from 243kHz to 178kHz, while the minimum voltages increased from 405mV to 793mV as the added amount of glucose increased from 0 to 5cc. The study demonstrated the feasibility of applying this new REIS technology to measure and/or monitor glucose levels in real-time in future.

  4. Real-time gastric motility monitoring using transcutaneous intraluminal impedance measurements (TIIM).

    PubMed

    Poscente, M D; Wang, G; Filip, D; Ninova, P; Yadid-Pecht, O; Andrews, C N; Mintchev, M P

    2014-02-01

    The stomach plays a critical role in digestion, processing ingested food mechanically and breaking it up into particles, which can be effectively and efficiently processed by the intestines. When the motility of the stomach is compromised, digestion is adversely affected. This can lead to a variety of disorders. Current diagnostic techniques for gastric motility disorders are seriously lacking, and are based more on eliminating other possibilities rather than on specific tests. Presently, gastric motility can be assessed by monitoring gastric emptying, food transit, intragastric pressures, etc. The associated tests are usually stationary and of relatively short duration. The present study proposes a new method of measuring gastric motility, utilizing the attenuation of an oscillator-induced electrical signal across the gastric tissue, which is modulated by gastric contractions. The induced high-frequency oscillator signal is generated within the stomach, and is picked up transluminally by cutaneous electrodes positioned on the abdominal area connected to a custom-designed data acquisition instrument. The proposed method was implemented in two different designs: first a transoral catheter was modified to emit the signal inside the stomach; and second, a gastric retentive pill was designed to emit the signal. Both implementations were applied in vivo on two mongrel dogs (25.50 kg and 25.75 kg). Gastric contractions were registered and quantitatively compared to recordings from force transducers sutured onto the serosa of the stomach. Gastric motility indices were calculated for each minute, with transluminal impedance measurements and the measurements from the force transducers showing statistically significant (p < 0.05) Pearson correlation coefficients (0.65 ± 0.08 for the catheter-based design and 0.77 ± 0.03 for the gastric retentive pill design). These results show that transcutaneous intraluminal impedance measurement has the potential with further research

  5. Measurement of the acoustic reflectivity of sirenia (Florida manatees) at 171 kHz.

    PubMed

    Jaffe, Jules S; Simonet, Fernando; Roberts, Paul L D; Bowles, Ann E

    2007-01-01

    The Florida manatee (Trichechus manatus latirostris) is an endangered sirenian. At present, its adult population (approximately 2200) seems stable, but tenuous. Manatee-boat collisions are a significant proportion (approximately 25%) of mortalities. Here, the potential use of active sonar for detecting manatees by quantifying sonic reflectivity is explored. In order to estimate reflectivity two methods were used. One method measured live reflections from captive animals using a carefully calibrated acoustic and co-registered optical system. The other method consisted of the analysis of animal tissue in order to obtain estimates of the sound speed and density and to predict reflectivity. The impedance measurement predicts that for a lateral view, the tissue reflectivity is close to 0.13, with a critical grazing angle of 28 degrees. Data measured from live animals indicate that substantial reflections can be recorded, however in many instances observed "empirical target strengths" were less than an experimentally dependent -48-dB threshold. Conclusions favor the hypothesis that the animals reflect substantial amounts of sound; however, the reflections can often be specular, and therefore impractical for observation by a manatee detection sonar operating at 171 kHz.

  6. A re-expansion method for determining the acoustical impedance and the scattering matrix for the waveguide discontinuity problem

    PubMed Central

    Homentcovschi, Dorel; Miles, Ronald N.

    2010-01-01

    The paper gives a new method for analyzing planar discontinuities in rectangular waveguides. The method consists of a re-expansion of the normal modes in the two ducts at the junction plane into a system of functions accounting for the velocity singularities at the corner points. As the new expansion has an exponential convergence, only a few terms have to be considered for obtaining the solution of most practical problems. To see how the method works some closed form solutions, obtained by the conformal mapping method, are used to discuss the convergence of the re-expanded series when the number of retained terms increases. The equivalent impedance accounting for nonplanar waves into a plane-wave analysis is determined. Finally, the paper yields the scattering matrix which describes the coupling of arbitrary modes at each side of the discontinuity valid in the case of many propagating modes in both parts of the duct. PMID:20707432

  7. Relationship between acoustic measures and speech naturalness ratings in Parkinson's disease: A within-speaker approach.

    PubMed

    Klopfenstein, Marie

    2015-01-01

    This study investigated the acoustic basis of across-utterance, within-speaker variation in speech naturalness for four speakers with dysarthria secondary to Parkinson's disease (PD). Speakers read sentences and produced spontaneous speech. Acoustic measures of fundamental frequency, phrase-final syllable lengthening, intensity and speech rate were obtained. A group of listeners judged speech naturalness using a nine-point Likert scale. Relationships between judgements of speech naturalness and acoustic measures were determined for individual speakers with PD. Relationships among acoustic measures also were quantified. Despite variability between speakers, measures of mean F0, intensity range, articulation rate, average syllable duration, duration of final syllables, vocalic nucleus length of final unstressed syllables and pitch accent of final syllables emerged as possible acoustic variables contributing to within-speaker variations in speech naturalness. Results suggest that acoustic measures correlate with speech naturalness, but in dysarthric speech they depend on the speaker due to the within-speaker variation in speech impairment.

  8. Development of impedance/external field potential dual measurement system for evaluation of electrophysiological properties of cells on microelectrodes

    NASA Astrophysics Data System (ADS)

    Nomura, Fumimasa; Matsuura, Kenji; Hattori, Akihiro; Odaka, Masao; Sugio, Yoshihiro; Kurotobi, Hiromi; Terazono, Hideyuki; Yasuda, Kenji

    2015-06-01

    A combination of extracellular field potential (FP) and impedance measurement technologies for multielectrode array (MEA) chip architecture is developed for the simultaneous evaluation of information on the ion current and resistance of cells and microelectrodes. The simultaneous measurement system can not only evaluate the time course changes of characteristics in the MEAs but also clarification of the origin of the difference in the waveform of the field potentials of each cell on an microelectrode whether it is caused by the changes in the electrophysiological properties of cells or by the changes in the performance of an microelectrode (and cell-to-electrode contacts). The automatic impedance measurement technology in the system exploited the swiping of the wide frequency range of impedances of microelectrodes and calculated the true impedance of each microelectrode without significant effects on the cells on the MEA chip. Hence, the system can give us invisible cell-to-electrode contact information and its change, and also information on the degradation of the performance of microelectrodes during long-term cultivation and after the application of compounds into the MEA chip. The impedance spectrum measurement showed that (1) the increase in the impedance of microelectrodes correlated with its area decrease from 10-7 to 10-10 m2, (2) even the area of microelectrodes decreased from 10-8 to 10-10 m2, the noise level of field potential signals was independent and did not change, and (3) the attachment of cells on the microelectrode surface can be determined by a significant increase in impedance at 1 kHz corresponding to the width of the depolarization peak on the field potential recordings. These results indicate the potential to evaluate the cell-to-electrode contact and degradation of microelectrodes, which was not evaluated in conventional FP measurements only. These results also indicate that this method should be used for the evaluation of the changes in

  9. Acoustic measurement of the surface tension of levitated drops

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Marston, P. L.; Robey, J. L.

    1988-01-01

    The measurement of the frequency of the fundamental mode of shape oscillation of acoustically levitated drops has been carried out to determine the surface tension of the drop material. Sound fields of about 20 kHz in frequency allow the suspension of drops a few millimeters in size, as well as the necessary drive for oscillations. The surface tension of water, hexadecane, silicone oil, and aqueous solutions of glycerin levitated in air has been measured, and the results have been compared with those obtained with standard ring tensiometry. The two sets of data are in good agreement, the largest discrepancy being about 10 percent. Uncertainties in the effects of the nonspherical static shape of drops levitated in the earth's gravitational field and the rotation state of the sample are the major contributors to the experimental error. A decrease of the resonance frequency of the fundamental mode indicates a soft nonlinearity as the oscillation amplitude increases.

  10. Measurement and Characterization of Space Shuttle Solid Rocket Motor Plume Acoustics

    NASA Technical Reports Server (NTRS)

    Kenny, Robert Jeremy

    2009-01-01

    NASA's current models to predict lift-off acoustics for launch vehicles are currently being updated using several numerical and empirical inputs. One empirical input comes from free-field acoustic data measured at three Space Shuttle Reusable Solid Rocket Motor (RSRM) static firings. The measurements were collected by a joint collaboration between NASA - Marshall Space Flight Center, Wyle Labs, and ATK Launch Systems. For the first time NASA measured large-thrust solid rocket motor plume acoustics for evaluation of both noise sources and acoustic radiation properties. Over sixty acoustic free-field measurements were taken over the three static firings to support evaluation of acoustic radiation near the rocket plume, far-field acoustic radiation patterns, plume acoustic power efficiencies, and apparent noise source locations within the plume. At approximately 67 m off nozzle centerline and 70 m downstream of the nozzle exit plan, the measured overall sound pressure level of the RSRM was 155 dB. Peak overall levels in the far field were over 140 dB at 300 m and 50-deg off of the RSRM thrust centerline. The successful collaboration has yielded valuable data that are being implemented into NASA's lift-off acoustic models, which will then be used to update predictions for Ares I and Ares V liftoff acoustic environments.

  11. Acoustic Environment of Admiralty Inlet: Broadband Noise Measurements

    SciTech Connect

    Xu, Jinshan; Deng, Zhiqun; Martinez, Jayson J.; Carlson, Thomas J.; Myers, Joshua R.; Weiland, Mark A.; Jones, Mark E.

    2011-09-30

    Admiralty Inlet has been selected as a potential tidal energy site. It is located near shipping lanes, is a highly variable acoustic environment, and is frequented by the highly endangered southern resident killer whale (SRKW). Resolving environmental impacts is the first step to receiving approval to deploy tidal turbines at Admiralty Inlet. Of particular concern is the potential for blade strike or other negative interactions between the SRKW and the tidal turbine. A variety of technologies including passive and active monitoring systems are being considered as potential tools to determine the presence of SRKW in the vicinity of the turbines. Broadband noise level measurements are critical for the determination of design and operation specifications of all marine and hydrokinetic energy capture technologies. Acoustic environment data at the proposed site was acquired at different depths using a cabled vertical line array (VLA) with four calibrated hydrophones. The sound pressure level (SPL) power spectrum density was estimated based on the fast Fourier transform. This study describes the first broadband SPL measurements for this site at different depths with frequency ranging from 10 kHz to 480 kHz in combination with other information. To understand the SPL caused by this bedload transport, three different pressure sensors with temperature and conductivity were also assembled on the VLA to measure the conditions at the hydrophone deployment depth. The broadband SPL levels at frequency ranges of 3 kHz to 7 kHz as a function of depth were estimated. Only the hydrophone at an average depth of 40 m showed the strong dependence of SPL with distance from the bottom, which was possibly caused by the cobbles shifting on the seabed. Automatic Identification System data were also studied to understand the SPL measurements.

  12. Radio frequency current-voltage probe for impedance and power measurements in multi-frequency unmatched loads.

    PubMed

    Lafleur, T; Delattre, P A; Booth, J P; Johnson, E V; Dine, S

    2013-01-01

    A broad-band, inline current-voltage probe, with a characteristic impedance of 50 Ω, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1-100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms.

  13. Magnetic resonance electrical impedance tomography for measuring electrical conductivity during electroporation.

    PubMed

    Kranjc, M; Bajd, F; Serša, I; Miklavčič, D

    2014-06-01

    The electroporation effect on tissue can be assessed by measurement of electrical properties of the tissue undergoing electroporation. The most prominent techniques for measuring electrical properties of electroporated tissues have been voltage-current measurement of applied pulses and electrical impedance tomography (EIT). However, the electrical conductivity of tissue assessed by means of voltage-current measurement was lacking in information on tissue heterogeneity, while EIT requires numerous additional electrodes and produces results with low spatial resolution and high noise. Magnetic resonance EIT (MREIT) is similar to EIT, as it is also used for reconstruction of conductivity images, though voltage and current measurements are not limited to the boundaries in MREIT, hence it yields conductivity images with better spatial resolution. The aim of this study was to investigate and demonstrate the feasibility of the MREIT technique for assessment of conductivity images of tissues undergoing electroporation. Two objects were investigated: agar phantoms and ex vivo liver tissue. As expected, no significant change of electrical conductivity was detected in agar phantoms exposed to pulses of all used amplitudes, while a considerable increase of conductivity was measured in liver tissue exposed to pulses of different amplitudes.

  14. An impedance bridge measuring the capacitance ratio in the high frequency range up to 1 MHz

    NASA Astrophysics Data System (ADS)

    Bee Kim, Dan; Kew Lee, Hyung; Kim, Wan-Seop

    2017-02-01

    This paper describes a 2-terminal-pair impedance bridge, measuring the capacitance ratio in the high frequency range up to 1 MHz. The bridge was configured with two voltage sources and a phase control unit which enabled the bridge balance by synchronizing the voltage sources with an enhanced phase resolution. Without employing the transformers such as inductive voltage divider, injection and detection transformers, etc, the bridge system is quite simple to set up, and the balance procedure is quick and easy. Using this dual-source coaxial bridge, the 1:1 and 10:1 capacitance ratios were measured with 1 pF-1 nF capacitors in the frequency range from 1 kHz to 1 MHz. The measurement values obtained by the dual-source bridge were then compared with reference values measured using a commercial precision capacitance bridge of AH2700A, the Z-matrix method developed by ourselves, and the 4-terminal-pair coaxial bridge by the Czech Metrological Institute. All the measurements agreed within the reference uncertainty range of an order of 10-6-10-5, proving the bridge ability as a trustworthy tool for measuring the capacitance ratio in the high frequency range.

  15. Evaluation of Grounding Impedance of a Complex Lightning Protective System Using Earth Ground Clamp Measurements and ATP Modeling

    NASA Technical Reports Server (NTRS)

    Mata, Carlos T.; Rakov, V. A.; Mata, Angel G.

    2010-01-01

    A new Lightning Protection System (LPS) was designed and built at Launch Complex 39B (LC39B), at the Kennedy Space Center (KSC), Florida, which consists of a catenary wire system (at a height of about 181 meters above ground level) supported by three insulators installed atop three towers in a triangular configuration. A total of nine downconductors (each about 250 meters long, on average) are connected to the catenary wire system. Each of the nine downconductors is connected to a 7.62-meter radius circular counterpoise conductor with six equally spaced 6-meter long vertical grounding rods. Grounding requirements at LC39B call for all underground and above ground metallic piping, enclosures, raceways, and cable trays, within 7.62 meters of the counterpoise, to be bounded to the counterpoise, which results in a complex interconnected grounding system, given the many metallic piping, raceways, and cable trays that run in multiple direction around LC39B. The complexity of this grounding system makes the fall of potential method, which uses multiple metallic rods or stakes, unsuitable for measuring the grounding impedances of the downconductors. To calculate the downconductors grounding impedance, an Earth Ground Clamp (a stakeless grounding resistance measuring device) and a LPS Alternative Transient Program (ATP) model are used. The Earth Ground Clamp is used to measure the loop impedance plus the grounding impedance of each downconductor and the ATP model is used to calculate the loop impedance of each downconductor circuit. The grounding impedance of the downconductors is then calculated by subtracting the ATP calculated loop impedances from the Earth Ground Clamp measurements.

  16. An Ultrasonic Caliper Device for Measuring Acoustic Nonlinearity

    NASA Astrophysics Data System (ADS)

    Hunter, Christopher; Sapozhnikov, Oleg A.; Maxwell, Adam D.; Khokhlova, Vera A.; Wang, Yak-Nam; MacConaghy, Brian; Kreider, Wayne

    In medical and industrial ultrasound, it is often necessary to measure the acoustic properties of a material. A specific medical application requires measurements of sound speed, attenuation, and nonlinearity to characterize livers being evaluated for transplantation. For this application, a transmission-mode caliper device is proposed in which both transmit and receive transducers are directly coupled to a test sample, the propagation distance is measured with an indicator gage, and receive waveforms are recorded for analysis. In this configuration, accurate measurements of nonlinearity present particular challenges: diffraction effects can be considerable while nonlinear distortions over short distances typically remain small. To enable simple estimates of the nonlinearity coeffcient from a quasi-linear approximation to the lossless Burgers' equation, the calipers utilize a large transmitter and plane waves are measured at distances of 15-50 mm. Waves at 667 kHz and pressures between 0.1 and 1 MPa were generated and measured in water at different distances; the nonlinearity coeffcient of water was estimated from these measurements with a variability of approximately 10%. Ongoing efforts seek to test caliper performance in other media and improve accuracy via additional transducer calibrations.

  17. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  18. Explanation of Anomalous Behavior Observed in Impedance Eduction Techniques Using Measured Data

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Jones, Michael G.

    2010-01-01

    Several enhancements that improve the accuracy and robustness of an impedance eduction technique that use an automatic optimizer are presented. These enhancements are then used to launch an intensive investigation into the cause of anomalous behavior that occurs for a small number of test conditions. This anomalous behavior is investigated for both a hardwall insert and a conventional liner. The primary conclusions of the study are that: (1) for the hard wall insert, the anomalies are due to narrow peaks in the objective function, (2) For the conventional liner, the anomalies are due to the presence of an extremely flat objective function, and (3) the anomalies appear to be triggered by inconsistencies between the duct propagation model and the measured data. At high frequencies, the duct propagation model may need to include the effects of higher-order duct modes, whereas at low frequencies, the effects of the mean boundary layer may have to be included.

  19. Prediction and Measurement of the Vibration and Acoustic Radiation of Panels Subjected to Acoustic Loading

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Rizzi, Stephen A.

    1995-01-01

    Interior noise and sonic fatigue are important issues in the development and design of advanced subsonic and supersonic aircraft. Conventional aircraft typically employ passive treatments, such as constrained layer damping and acoustic absorption materials, to reduce the structural response and resulting acoustic levels in the aircraft interior. These techniques require significant addition of mass and only attenuate relatively high frequency noise transmitted through the fuselage. Although structural acoustic coupling is in general very important in the study of aircraft fuselage interior noise, analysis of noise transmission through a panel supported in an infinite rigid baffle (separating two semi-infinite acoustic domains) can be useful in evaluating the effects of active/adaptive materials, complex loading, etc. Recent work has been aimed at developing adaptive and/or active methods of controlling the structural acoustic response of panels to reduce the transmitted noise1. A finite element formulation was recently developed to study the dynamic response of shape memory alloy (SMA) hybrid composite panels (conventional composite panel with embedded SMA fibers) subject to combined acoustic and thermal loads2. Further analysis has been performed to predict the far-field acoustic radiation using the finite element dynamic panel response prediction3. The purpose of the present work is to validate the panel vibration and acoustic radiation prediction methods with baseline experimental results obtained from an isotropic panel, without the effect of SMA.

  20. Electrical properties of rat muscle after sciatic nerve injury: Impact on surface impedance measurements assessed via finite element analysis

    NASA Astrophysics Data System (ADS)

    Ahad, M. A.; Rutkove, S. B.

    2010-04-01

    Tetrapolar surface electrical impedance methods are sensitive to changes in muscle status and can therefore provide a means for studying neuromuscular disease noninvasively. In order to better understand the relationship between surface impedance measurements and the actual muscle electrical properties, we performed measurements on 20 adult Wistar rats, 8 of which underwent sciatic nerve crush. Surface impedance measurements were performed on the left hind limb both before injury and out to 2 weeks after injury. In addition, both normal and sciatic crush animals were sacrificed and the dielectric properties of the extracted gastrocnemius muscle measured. We found that 50 kHz conductivities were greater in the animals that underwent crush than in the animals that did not. The permittivities in both directions, however, showed non-significant differences. In order to analyze the effect of these changes as well as the accompanying reduction in muscle volume, a finite element model of the hind limb was developed based on computerized tomographic imaging. The model successfully predicted the surface impedance values in the animals after crush injury and, by its inverse application, may be used to help determine the underlying electrical properties of muscle in various neuromuscular diseases based on surface impedance data.

  1. Biomedical engineering meets acupuncture - development of a miniaturized 48-channel skin impedance measurement system for needle and laser acupuncture

    PubMed Central

    2010-01-01

    Background Due to controversially discussed results in scientific literature concerning changes of electrical skin impedance before and during acupuncture a new measurement system has been developed. Methods The prototype measures and analyzes the electrical skin impedance computer-based and simultaneously in 48 channels within a 2.5×3.5 cm matrix. Preliminary measurements in one person were performed using metal needle and violet laser (405 nm) acupuncture at the acupoint Kongzui (LU6). The new system is an improvement on devices previously developed by other researchers for this purpose. Results Skin impedance in the immediate surroundings of the acupoint was lowered reproducibly following needle stimulation and also violet laser stimulation. Conclusions A new instrumentation for skin impedance measurements is presented. The following hypotheses suggested by our results will have to be tested in further studies: Needle acupuncture causes significant, specific local changes of electrical skin impedance parameters. Optical stimulation (violet laser) at an acupoint causes direct electrical biosignal changes. PMID:21092296

  2. High frequency electromagnetic impedance measurements for characterization, monitoring and verification efforts. 1998 annual progress report

    SciTech Connect

    Lee, K.H.; Pellerin, L.; Becker, A.

    1998-06-01

    'Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small due, and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. The authors are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach, known as the magnetotelluric (MT) method at low frequencies. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques. The summary of the work to date is divided into three sections: equipment procurement, instrumentation, and theoretical developments. For most earth materials, the frequency range from 1 to 100 MHz encompasses a very difficult transition zone between the wave propagation of displacement currents and the diffusive behavior of conduction currents. Test equipment, such as signal generators and amplifiers, does not cover the entire range except at great expense. Hence the authors have divided the range of investigation into three sub-ranges: 1--10 MHz, 10--30 MHz, and 30--100 MHz. Results to date are in the lowest frequency range of 1--10 MHz. Even though conduction currents

  3. Parametric electrical impedance tomography for measuring bone mineral density in the pelvis using a computational model.

    PubMed

    Kimel-Naor, Shani; Abboud, Shimon; Arad, Marina

    2016-08-01

    Osteoporosis is defined as bone microstructure deterioration resulting a decrease of bone's strength. Measured bone mineral density (BMD) constitutes the main tool for Osteoporosis diagnosis, management, and defines patient's fracture risk. In the present study, parametric electrical impedance tomography (pEIT) method was examined for monitoring BMD, using a computerized simulation model and preliminary real measurements. A numerical solver was developed to simulate surface potentials measured over a 3D computerized pelvis model. Varying cortical and cancellous BMD were simulated by changing bone conductivity and permittivity. Up to 35% and 16% change was found in the real and imaginary modules of the calculated potential, respectively, while BMD changes from 100% (normal) to 60% (Osteoporosis). Negligible BMD relative error was obtained with SNR>60 [dB]. Position changes errors indicate that for long term monitoring, measurement should be taken at the same geometrical configuration with great accuracy. The numerical simulations were compared to actual measurements that were acquired from a healthy male subject using a five electrodes belt bioimpedance device. The results suggest that pEIT may provide an inexpensive easy to use tool for frequent monitoring BMD in small clinics during pharmacological treatment, as a complementary method to DEXA test.

  4. A new method for the precise multiband microwave dielectric measurement using stepped impedance stub

    NASA Astrophysics Data System (ADS)

    Sandhu, M. Y.; Ali, A.; Hunter, I. C.; Roberts, N. S.

    2016-11-01

    This article presents a new method of wideband dielectric measurement at microwave frequencies. This method can be used to determine the complex dielectric properties of solid and semisolid materials from 0.9 GHz to 4.5 GHz, including the ISM bands of 915 MHz and 2450 MHz. The new method is based on the scattering parameter measurement of a stepped impedance open circuited micro-strip stub, partly loaded with dielectric test material. Current microwave wideband spectroscopy techniques generally measure dielectric materials over a wide range of frequencies but their accuracy is limited. In contrast, narrowband techniques generally measure dielectric properties to a high accuracy but only at a single frequency. This new technique is capable of measuring dielectric properties over a wide range of frequencies to a high accuracy. The technique has been verified by the empirical characterisation of the dielectric properties of Teflon and Duroid 5880 materials. Empirical results were in good agreement with values in the manufacturer’s Data Sheets. The complex permittivity data will be useful for further microwave processing of the materials.

  5. Application of acoustic doppler velocimeters for streamflow measurements

    USGS Publications Warehouse

    Rehmel, M.

    2007-01-01

    The U.S. Geological Survey (USGS) principally has used Price AA and Price pygmy mechanical current meters for measurement of discharge. New technologies have resulted in the introduction of alternatives to the Price meters. One alternative, the FlowTracker acoustic Doppler velocimeter, was designed by SonTek/YSI to make streamflow measurements in wadeable conditions. The device measures a point velocity and can be used with standard midsection method algorithms to compute streamflow. The USGS collected 55 quality-assurance measurements with the FlowTracker at 43 different USGS streamflow-gaging stations across the United States, with mean depths from 0.05to0.67m, mean velocities from 13 to 60 cm/s, and discharges from 0.02 to 12.4m3/s. These measurements were compared with Price mechanical current meter measurements. Analysis of the comparisons shows that the FlowTracker discharges were not statistically different from the Price meter discharges at a 95% confidence level. ?? 2007 ASCE.

  6. High Frequency Electromagnetic Impedance Measurements For Characterization, Monitoring And Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex

    2000-12-31

    Electromagnetic methods in exploration geophysics include many technologies capable of imaging the subsurface. The electromagnetic geophysical spectrum for shallow subsurface imaging is roughly 1 Hz to 500 MHz, with electrical resistivity and other geometric sounding methods located at the low frequency end and the familiar GPR method at the high end of the spectrum. Baseline studies (Pellerin et al., 1997) show that electromagnetic instrumentation in the mid- and low-frequencies (< 300 kHz) and GPR systems (> 30 MHz) are well developed in the commercial sector. In the high-frequency range of 300 kHz to 100 MHz developments have been quite recent and reside within the research community. Accurate theoretical numerical modeling algorithms are available for simulations and interpretation across the entire spectrum (Mackie and Madden, 1993; Pellerin et al., 1995; Pellerin et al., 1997; Alumbaugh and Newman, 1995; Lee et al., 1995, Newmann and Alumbaugh, 1997; Newmann, 1999; Sasaki, 1999, etc.), but instrumentation suitable for collecting calibrated field data in the important high-frequency range is critically lacking. Several attempts to develop reliable, accurate and calibrated instruments (Sternberg and Poulton, 1996; Stewart et al., 1994; Wright et el., 1996) have produced mixed results. We proposed to exploit the concept of electromagnetic impedance, the ratio of orthogonal horizontal electric to horizontal magnetic fields, to provide the necessary technology in the high-frequency band described above. The effective depth of investigation for surface impedance measurements depends on the frequency, and is commonly expressed in terms of the skin depth, the distance into the conductive half space at which the amplitude of the incoming wave has decreased to e-1 of its surface value. In order to achieve skin depths between 0.5 and 10 meters in material of resistivity between 1 and 100 ohm-m and relative permittivity between 1 and 30, frequencies bet ween about 300 k

  7. Measurement of ultrasonic power and electro-acoustic efficiency of high power transducers.

    PubMed

    Lin, S; Zhang, F

    2000-01-01

    In this paper, an improved method for the measurement of acoustic power and electro-acoustic efficiency of high power ultrasonic transducers is presented. The measuring principle is described, the experimental results are given. In comparison with traditional methods, the method presented in this paper has the advantages of simplicity, economy and practicality. The most important is that it can measure the output acoustic power and the electro-acoustic efficiency of the transducer under the condition of high power and practical applications, such as ultrasonic cleaning and soldering.

  8. A theoretical study of the acoustic impedance of orifices in the presence of a steady grazing flow

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1976-01-01

    An analysis of the oscillatory fluid flow in the vicinity of a circular orifice with a steady grazing flow is presented. The study is similar to that of Hersh and Rogers but with the addition of the grazing flow. Starting from the momentum and continuity equations, a considerably simplified system of partial differential equations is developed with the assumption that the flow can be described by an oscillatory motion superimposed upon the known steady flow. The equations are seen to be linear in the region where the grazing flow effects are dominant, and a solution and the resulting orifice impedance are presented for this region. The nonlinearity appears to be unimportant for the usual conditions found in aircraft noise suppressors. Some preliminary conclusions of the study are that orifice resistance is directly proportional to grazing flow velocity (known previously from experimental data) and that the orifice inductive (mass reactance) end correction is not a function of grazing flow. This latter conclusion is contrary to the widely held notion that grazing flow removes the effect of the orifice inductive end correction. This conclusion also implies that the experimentally observed total inductance reduction with grazing flow might be in the flow within the orifice rather than in the end correction.

  9. Validation of an Impedance Education Method in Flow

    NASA Technical Reports Server (NTRS)

    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

  10. Inhibition of neuronal cell-cell adhesion measured by the microscopic aggregation assay and impedance sensing

    NASA Astrophysics Data System (ADS)

    Wiertz, R. W. F.; Marani, E.; Rutten, W. L. C.

    2010-10-01

    Microscopic aggregation assay and impedance sensing (IS) were used to monitor a change in in vitro neuron-neuron adhesion in response to blocking of cell adhesion molecules. By blocking neuron-neuron adhesion, migration and aggregation of neuronal cells can be inhibited. This leads to better control of spatial arrangement of cells in culture. In the literature N-CAM, L1 and N-cadherin proteins are pointed out as main regulators of neuronal adhesion. In this study, these three main cell adhesion molecules were used to inhibit neuron-to-neuron adhesion and aggregation. Both soluble extracellular domains and antigen antibodies were added to these adhesion molecules. They were investigated for their blocking ability in neuronal cultures. First, in a 96 h aggregation assay on a low-adhesive substrate, the effect of inhibition of the three proteins on aggregation of cortical neurons was investigated optically. Both L1 antibody and L1 protein had no effect on the degree of aggregation. An N-cadherin antibody however was shown to be effective in aggregation inhibition at concentrations of 1 and 3 µg ml-1. Up to 96 h no aggregation occurred. A similar effect was achieved by the N-cadherin protein, although less distinct. N-CAM blocking revealed no inhibition of aggregation. Second, results from IS corresponded to those of the aggregation assays. In these experiments neuron-neuron adhesion was also inhibited by blocking N-CAM L1 and N-cadherin. Cortical neurons were cultured in small wells containing circular 100 µm diameter gold electrodes, so small changes in cell-cell interactions in monolayers of neurons could be monitored by IS. Impedances of neuron-covered electrodes were significantly lower in the presence of the N-cadherin antibody and protein at concentrations of 1, 3 and 10 µg ml-1, indicating a less profound binding between adjacent neurons. Results from the aggregation assays and impedance measurements demonstrate the applicability of blocking cell adhesion

  11. Acoustic measurements of a full-scale coaxial helicopter

    NASA Technical Reports Server (NTRS)

    Mosher, M.; Peterson, R. L.

    1983-01-01

    Acoustic data were obtained during a full-scale test of the XH-59A Advancing Blade Concept (ABC) Technology Demonstrator in the NASA Ames 40- by 80-Foot Wind Tunnel. The XH-59A is a research helicopter with two coaxial rotors and hingeless blades. Performance, vibration, noise at various forward speeds, rotor lift coefficients, and rotor shaft angles of attack were investigated. In general, the noise level is shown to increase with rotor lift coefficient except under certain operating conditions where it is increased by significant impulsive blade/vortex interactions. The impulsivity appears to depend upon how the lift is distributed between the two rotors. The noise levels measured are shown to be slightly higher than on a modern conventional rotor tested in the same facility.

  12. Determination of particle size distributions from acoustic wave propagation measurements

    SciTech Connect

    Spelt, P.D.; Norato, M.A.; Sangani, A.S.; Tavlarides, L.L.

    1999-05-01

    The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley [J. Acoust. Soc. Am. {bold 51}, 1545 (1972)] for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations. {copyright} {ital 1999 American Institute of Physics.}

  13. Effects of ingested atmospheric turbulence on measured tail rotor acoustics

    NASA Technical Reports Server (NTRS)

    Signor, David B.; Yamauchi, Gloria K.; Mosher, Marianne; Hagen, Martin J.; George, Albert R.

    1992-01-01

    Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustics of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simultaneous rotor performance, noise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of turbulence ingestion on rotor noise are quantified. Turbulence ingestion noise is found to be the dominant noise mechanism at locations near the rotor axis. At these locations, the sound radiated by the hovering rotor increases with both increasing atmospheric wind speed and ingested rms turbulent velocity.

  14. Measurements of atmospheric turbulence effects on tail rotor acoustics

    NASA Technical Reports Server (NTRS)

    Hagen, Martin J.; Yamauchi, Gloria K.; Signor, David B.; Mosher, Marianne

    1994-01-01

    Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustics of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simultaneous rotor performance, noise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of atmospheric turbulence ingestion on rotor noise are quantified. In contradiction to current theories, increasing rotor inflow and rotor thrust were found to increase turbulence ingestion noise. This is the final report of Task 13A--Helicopter Tail Rotor Noise, of the NASA/United Kingdom Defense Research Agency cooperative Aeronautics Research Program.

  15. Pulsed electro-acoustic (PEA) measurements of embedded charge distributions

    NASA Astrophysics Data System (ADS)

    Dennison, J. R.; Pearson, Lee H.

    2013-09-01

    Knowledge of the spatial distribution and evolution of embedded charge in thin dielectric materials has important applications in semiconductor, high-power electronic device, high-voltage DC power cable insulation, high-energy and plasma physics apparatus, and spacecraft industries. Knowing how, where, and how much charge accumulates and how it redistributes and dissipates can predict destructive charging effects. Pulsed Electro-acoustic (PEA) measurements— and two closely related methods, Pressure Wave Propagation (PWP) and Laser Intensity Modulation (LIMM)— nondestructively probe such internal charge distributions. We review the instrumentation, methods, theory and signal processing of simple PEA experiments, as well as the related PPW and LIMM methods. We emphasize system improvements required to achieve high spatial resolution for in vacuo measurements of thin dielectrics charged using electron beam injection.

  16. Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

    NASA Technical Reports Server (NTRS)

    Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

    2016-01-01

    Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

  17. Picosecond Acoustic Measurement of Anisotropic Properties of Thin Films

    SciTech Connect

    Perton, M.; Rossignol, C.; Chigarev, N.; Audoin, B.

    2007-03-21

    Properties of thin metallic films have been studied extensively by means of laser-picosecond ultrasonics. Generation of longitudinal and shear waves via thermoelastic mechanism and large source has been only demonstrated for waves vectors along the normal to the interface. However, such measurements cannot provide complete information about elastic properties of films. As it has been already shown for nanosecond ultrasonics, the knowledge of group or phase velocities in several directions for sources with small lateral size allows determining the stiffness tensor coefficients of a sample. The experimental set-up was prepared to obtain the thinnest size for the source to achieve acoustic diffraction. The identification of the stiffness tensor components, based on the inversion of the bulk waves phase velocities, is applied to signals simulated and experimentally recorded for a material with hexagonal properties. First estimation of stiffness tensor coefficients for thin metallic film 2.1 {mu}m has been performed.

  18. Non-contact multi-frequency magnetic induction spectroscopy system for industrial-scale bio-impedance measurement

    NASA Astrophysics Data System (ADS)

    O'Toole, M. D.; Marsh, L. A.; Davidson, J. L.; Tan, Y. M.; Armitage, D. W.; Peyton, A. J.

    2015-03-01

    Biological tissues have a complex impedance, or bio-impedance, profile which changes with respect to frequency. This is caused by dispersion mechanisms which govern how the electromagnetic field interacts with the tissue at the cellular and molecular level. Measuring the bio-impedance spectra of a biological sample can potentially provide insight into the sample’s properties and its cellular structure. This has obvious applications in the medical, pharmaceutical and food-based industrial domains. However, measuring the bio-impedance spectra non-destructively and in a way which is practical at an industrial scale presents substantial challenges. The low conductivity of the sample requires a highly sensitive instrument, while the demands of industrial-scale operation require a fast high-throughput sensor of rugged design. In this paper, we describe a multi-frequency magnetic induction spectroscopy (MIS) system suitable for industrial-scale, non-contact, spectroscopic bio-impedance measurement over a bandwidth of 156 kHz-2.5 MHz. The system sensitivity and performance are investigated using calibration and known reference samples. It is shown to yield rapid and consistently sensitive results with good long-term stability. The system is then used to obtain conductivity spectra of a number of biological test samples, including yeast suspensions of varying concentration and a range of agricultural produce, such as apples, pears, nectarines, kiwis, potatoes, oranges and tomatoes.

  19. Measurement of the Acoustic Nonlinearity Parameter for Biological Media.

    NASA Astrophysics Data System (ADS)

    Cobb, Wesley Nelson

    In vitro measurements of the acoustic nonlinearity parameter are presented for several biological media. With these measurements it is possible to predict the distortion of a finite amplitude wave in biological tissues of current diagnostic and research interest. The measurement method is based on the finite amplitude distortion of a sine wave that is emmitted by a piston source. The growth of the second harmonic component of this wave is measured by a piston receiver which is coaxial with and has the same size as the source. The experimental measurements and theory are compared in order to determine the nonlinearity parameter. The density, sound speed, and attenuation for the medium are determined in order to make this comparison. The theory developed for this study accounts for the influence of both diffraction and attenuation on the experimental measurements. The effects of dispersion, tissue inhomogeneity and gas bubbles within the excised tissues are studied. To test the measurement method, experimental results are compared with established values for the nonlinearity parameter of distilled water, ethylene glycol and glycerol. The agreement between these values suggests that the measurement uncertainty is (+OR-) 5% for liquids and (+OR-) 10% for solid tissues. Measurements are presented for dog blood and bovine serum albumen as a function of concentration. The nonlinearity parameters for liver, kidney and spleen are reported for both human and canine tissues. The values for the fresh tissues displayed little variation (6.8 to 7.8). Measurements for fixed, normal and cirrhotic tissues indicated that the nonlinearity parameter does not depend strongly on pathology. However, the values for fixed tissues were somewhat higher than those of the fresh tissues.

  20. Measuring the dielectric properties of soil-organic mixtures using coaxial impedance dielectric reflectometry

    NASA Astrophysics Data System (ADS)

    Francisca, Franco M.; Montoro, Marcos A.

    2012-05-01

    Contamination of soils with non-aqueous phase liquids (NAPLs) is frequently produced by accidental spills and storage tanks or pipes leakage. The main goals dealing with soil and groundwater contamination include determining the extension of the affected zone, monitoring the contaminant plume and quantifying the pollution degree. The objective of this work is to evaluate the potential of dielectric permittivity measurements to detect the presence of NAPLs in sands. Tested samples were fine, medium, coarse and silty sand with different volumetric contents of water and paraffin oil. The dielectric permittivity was measured by means of a Coaxial Impedance Dielectric Reflectometry method in specimens with either known fluid content or at different stages during immiscible displacement tests. A simplified method was developed to quantify the amount of oil from dielectric permittivity measurements and effective mixture media models. Obtained results showed that groundwater contamination with NAPL and the monitoring of immiscible fluid displacement in saturated porous media can be clearly identified from dielectric measurements. Finally, very accurate results can be obtained when computing the contamination degree with the proposed method in comparison with the real volumetric content of NAPL (r2 > 90%).

  1. Measurements of the impedance matrix of a thermoacoustic core: applications to the design of thermoacoustic engines.

    PubMed

    Bannwart, Flávio C; Penelet, Guillaume; Lotton, Pierrick; Dalmont, Jean-Pierre

    2013-05-01

    The successful design of a thermoacoustic engine depends on the appropriate description of the processes involved inside the thermoacoustic core (TAC). This is a difficult task when considering the complexity of both the heat transfer phenomena and the geometry of the porous material wherein the thermoacoustic amplification process occurs. An attempt to getting round this difficulty consists in measuring the TAC transfer matrix under various heating conditions, the measured transfer matrices being exploited afterward into analytical models describing the complete apparatus. In this paper, a method based on impedance measurements is put forward, which allows the accurate measurement of the TAC transfer matrix, contrarily to the classical two-load method. Four different materials are tested, each one playing as the porous element allotted inside the TAC, which is submitted to different temperature gradients to promote thermoacoustic amplification. The experimental results are applied to the modeling of basic standing-wave and traveling-wave engines, allowing the prediction of the engine operating frequency and thermoacoustic amplification gain, as well as the optimum choice of the components surrounding the TAC.

  2. Assessing risk of thyroid cancer using resonance-frequency based electrical impedance measurements

    NASA Astrophysics Data System (ADS)

    Zheng, Bin; Tublin, Mitchell E.; Lederman, Dror; Klym, Amy H.; Brown, Erica D.; Gur, David

    2011-03-01

    The incidence of thyroid cancer has risen faster than many malignancies and has nearly doubled in the USA over the past 30 years. Palpable nodules and subclinical nodules detected by imaging are found in a large percentage of the USA population. Most of these (.>95%) are fortunately benign. This vast reservoir of nodules makes the detection and diagnosis of thyroid cancer a diagnostic dilemma. Ultrasound guided Fine Needle Aspiration Biopsy (FNAB) is excellent for triaging patients but up to 25% of FNABs are inconclusive. As a result, definitive diagnosis is often only possible with a diagnostic lobectomy; many thousands of these are performed in the USA annually for ultimately benign disease. It would be extremely beneficial if we could develop a non-invasive procedure that could assist the diagnostician in reliably predicting the likelihood of malignancy of otherwise indeterminate thyroid nodules, thereby reducing the number of these "exploratory/diagnostic" lobectomies performed under general anesthesia. Electrical Impedance Spectroscopy (EIS) was considered as a possible approach to address this problem. However, the diagnostic accuracy of EIS is too low for routine clinical use to date. In our group, we developed a substantially modified technology termed Resonance-frequency Electrical Impedance Spectroscopy (REIS), which yields usable information for classifying risk of having breast abnormalities. We preliminarily applied REIS to measure signals on participants having thyroid nodules aiming to assess whether we can assist in improving diagnosis of indeterminate thyroid nodules. In this study we present a new multi-probe based REIS device specifically designed for the assessment of indeterminate thyroid nodules. Our preliminary assessment presented here demonstrates the feasibility of using this proposed REIS device in a busy tertiary care center.

  3. Method to detect the end-point for PCR DNA amplification using an ionically labeled probe and measuring impedance change

    DOEpatents

    Miles, Robin R.; Belgrader, Phillip; Fuller, Christopher D.

    2007-01-02

    Impedance measurements are used to detect the end-point for PCR DNA amplification. A pair of spaced electrodes are located on a surface of a microfluidic channel and an AC or DC voltage is applied across the electrodes to produce an electric field. An ionically labeled probe will attach to a complementary DNA segment, and a polymerase enzyme will release the ionic label. This causes the conductivity of the solution in the area of the electrode to change. This change in conductivity is measured as a change in the impedance been the two electrodes.

  4. Determination of ammonium in Kjeldahl digests by gas-diffusion flow-injection analysis with a bulk acoustic wave-impedance sensor.

    PubMed

    Su, X L; Nie, L H; Yao, S Z

    1997-11-01

    A novel flow-injection analysis (FIA) system has been developed for the rapid and direct determination of ammonium in Kjeldahl digests. The method is based on diffusion of ammonia across a PTFE gas-permeable membrane from an alkaline (NaOH/EDTA) stream into a stream of diluted boric acid. The trapped ammonium in the acceptor is determined on line by a bulk acoustic wave (BAW)-impedance sensor and the signal is proportional to the ammonium concentration present in the digests. The proposed system exhibits a favorable frequency response to 5.0 x 10(-6)-4.0 x 10(-3) mol l(-1) ammonium with a detection limit of 1.0 x 10(-6) mol l(-1), and the precision was better than 1% (RSD) for 0.025-1.0 mM ammonium at a through-put of 45-50 samples h(-1). Results obtained for nitrogen determination in amino acids and for proteins determination in blood products are in good agreement with those obtained by the conventional distillation/titration method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail.

  5. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    NASA Astrophysics Data System (ADS)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  6. Acoustic measurements of F-16 aircraft operating in hush house, NSN 4920-02-070-2721

    NASA Astrophysics Data System (ADS)

    Miller, V. R.; Plzak, G. A.; Chinn, J. M.

    1981-09-01

    The purpose of this test program was to measure the acoustic environment in the hush house facility located at Kelly Air Force Base, Texas, during operation of the F-16 aircraft to ensure that aircraft structural acoustic design limits were not exceeded. The acoustic measurements showed that no sonic fatigue problems are anticipated with the F-16 aircraft aft fuselage structure during operation in the hush house. The measured acoustic levels were less than those measured in an F-16 aircraft water cooled hush house at Hill AFB, but were increased over that measured during ground run up. It was recommended that the acoustic loads measured in this program should be specified in the structural design criteria for aircraft which will be subjected to hush house operation or defining requirements for associated equipment.

  7. Measurement of fluid viscosity at microliter volumes using quartz impedance analysis.

    PubMed

    Saluja, Atul; Kalonia, Devendra S

    2004-08-05

    The purpose of this work was to measure viscosity of fluids at low microliter volumes by means of quartz crystal impedance analysis. To achieve this, a novel setup was designed that allowed for measurement of viscosity at volumes of 8 to 10 microL. The technique was based on the principle of electromechanical coupling of piezoelectric quartz crystals. The arrangement was simple with measurement times ranging from 2 to 3 minutes. The crystal setup assembly did not impose any unwanted initial stress on the unloaded quartz crystal. Quartz crystals of 5- and 10-MHz fundamental frequency were calibrated with glycerol-water mixtures of known density and viscosity prior to viscosity measurements. True frequency shifts, for the purpose of this work, were determined followed by viscosity measurement of aqueous solutions of sucrose, urea, PEG-400, glucose, and ethylene glycol at 25 degrees C +/- 0.5 degrees C. The measured viscosities were found to be reproducible and consistent with the values reported in the literature. Minor inconsistencies in the measured resistance and frequency shifts did not affect the results significantly, and were found to be experimental in origin rather than due to electrode surface roughness. Besides, as expected for a viscoelastic fluid, PEG 8000 solutions, the calculated viscosities were found to be less than the reported values due to frequency dependence of storage and loss modulus components of complex viscosity. From the results, it can be concluded that the present setup can provide accurate assessment of viscosity of Newtonian fluids and also shows potential for analyzing non-Newtonian fluids at low microliter volumes.

  8. Measurement of nutritional status in simulated microgravity by bioelectrical impedance spectroscopy

    NASA Technical Reports Server (NTRS)

    Bartok, Cynthia; Atkinson, Richard L.; Schoeller, Dale A.

    2003-01-01

    The potential of bioelectrical impedance spectroscopy (BIS) for assessing nutritional status in spaceflight was tested in two head-down-tilt bed-rest studies. BIS-predicted extracellular water (ECW), intracellular water (ICW), and total body water (TBW) measured using knee-elbow electrode placement were compared with deuterium and bromide dilution (DIL) volumes in healthy, 19- to 45-yr-old subjects. BIS was accurate during 44 h of head-down tilt with mean differences (BIS - DIL) of 0-0.1 kg for ECW, 0.3-0.5 for ICW, and 0.4-0.6 kg for TBW (n = 28). At 44 h, BIS followed the within-individual change in body water compartments with a relative prediction error (standard error of the estimate/baseline volume) of 2.0-3.6% of water space. In the second study, BIS did not detect an acute decrease (-1.41 +/- 0.91 kg) in ICW secondary to 48 h of a protein-free, 800 kcal/day diet (n = 18). BIS's insensitivity to ICW losses may be because they were predominantly (65%) localized to the trunk and/or because there was a general failure of BIS to measure ICW independently of ECW and TBW. BIS may have potential for measuring nutritional status during spaceflight, but its limitations in precision and insensitivity to acute ICW changes warrant further validation studies.

  9. Transcutaneous Intraluminal Impedance Measurement for Minimally Invasive Monitoring of Gastric Motility: Validation in Acute Canine Models

    PubMed Central

    Poscente, Michael D.; Wang, Gang; Filip, Dobromir; Ninova, Polya; Muench, Gregory; Yadid-Pecht, Orly; Mintchev, Martin P.; Andrews, Christopher N.

    2014-01-01

    Transcutaneous intraluminal impedance measurement (TIIM) is a new method to cutaneously measure gastric contractions by assessing the attenuation dynamics of a small oscillating voltage emitted by a battery-powered ingestible capsule retained in the stomach. In the present study, we investigated whether TIIM can reliably assess gastric motility in acute canine models. Methods. Eight mongrel dogs were randomly divided into 2 groups: half received an active TIIM pill and half received an identically sized sham capsule. After 24-hour fasting and transoral administration of the pill (active or sham), two force transducers (FT) were sutured onto the antral serosa at laparotomy. After closure, three standard cutaneous electrodes were placed on the abdomen, registering the transluminally emitted voltage. Thirty-minute baseline recordings were followed by pharmacological induction of gastric contractions using neostigmine IV and another 30-minute recording. Normalized one-minute baseline and post-neostigmine gastric motility indices (GMIs) were calculated and Pearson correlation coefficients (PCCs) between cutaneous and FT GMIs were obtained. Statistically significant GMI PCCs were seen in both baseline and post-neostigmine states. There were no significant GMI PCCs in the sham capsule test. Further chronic animal studies of this novel long-term gastric motility measurement technique are needed before testing it on humans. PMID:25574163

  10. Investigation of critical shear stress with simultaneous measurement of electrical impedance, capacitance and light backscattering.

    PubMed

    Lee, Byoung-Kwon; Ko, Jae-yong; Lim, Hyun-jung; Nam, Jeong-Hun; Shin, Sehyun

    2012-01-01

    Recent electrical investigation of hemorheology provided useful information on the kinetics of red blood cell (RBC) aggregation. However, because of the inconsistent results in the electrical measurements, we need to understand the electrical characteristics of RBC aggregation at various flow conditions. In the present study, AC electrical-capacitance (EC) and -impedance (EI) and light backscattering (LB) were simultaneously measured for transient shear-decreasing blood flow in a microchannel. EI, EC and LB signals of RBCs in plasma show similar time-varying curves, both yielding either a peak or a minimal point in the optimal frequency range (10~500 kHz). Critical shear stress (CSS) determined from EC showed the nearly same results as that determined from LB, with yielding hematocrits-independence and dextran-concentration dependence. However, the high concentration of fibrinogen caused electrical saturation, which resulted in different results of CSS determined from between LB and EC. These results suggest that electrical properties of RBC suspensions should be further examined to replace the optical method of measurement of RBC aggregation.

  11. Thermal diffusivity measurement using thermographic method and performance evaluation by impedance spectroscopy for thermoelectric module

    NASA Astrophysics Data System (ADS)

    Otsuka, Mioko; Terakado, Hiroki; Homma, Ryoei; Hasegawa, Yasuhiro; Zahidul Islam, Md.; Bastian, Georg; Stuck, Alexander

    2016-12-01

    The thermal diffusivity of two bulk thermoelectric elements and a thermoelectric module was measured by an infrared camera using a thermographic method without any contact in air at room temperature. The estimated values for the elements (3.45 × 10-6 m2/s for a BiSb sample and 1.60 × 10-6 m2/s for a BiTe sample) were slightly larger than those measured in vacuum. The difference was explained as the effect of heat convection on the surface of the samples by solving the one-dimensional heat conduction equation numerically. The thermal diffusivity of thermoelectric elements in a thermoelectric module was also estimated using the thermographic method, and values of (1.1-1.7) × 10-6 m2/s in air were obtained, depending on the element. On the basis of the measurement results, the performance of the module was estimated using impedance spectroscopy, which can estimate not only the dimensionless figure of merit but also the thermal loss and response. The thermal response and thermal loss in air were similar to those in vacuum; however, the dimensionless figure of merit was 0.82 in vacuum and 0.70 in air.

  12. High-Frequency and Very-high-Frequency (HF&VHF) above-groundelectromagnetic impedance measurements

    SciTech Connect

    Frangos, William; Becker, Alex; Lee, K.H.

    2002-09-20

    We have field-tested an apparatus for measuring the electromagnetic impedance above the ground at a plurality of frequencies in the 0.3 - 30 MHz range. This window in the frequency spectrum, which lies between frequencies used for GPR and those used for conventional loop-loop EM soundings, has not been used because of difficulties in fielding equipment for making absolute and accurate measurements. Model and physical parameter studies however confirm that data in this frequency band can be used to construct high-resolution maps of electrical conductivity and permittivity of near-surface material. Our equipment was assembled using commercial electric and magnetic antennas. The magnetic loop source is excited by a conventional signal generator - power amplifier assembly. Signal detection is accomplished using RF lock-in amplifiers. All system elements are appropriately isolated by optic - fiber links. We estimate a measurement accuracy of about {+-} 10% for an 8-m separation between source and detector. Field tests were done at the University of California Richmond Field Station where the near surface electrical structure is well known. The experimental data at this site are mainly a function of electrical conductivity. In this context, we have obtained good agreement with the known local variations in resistivity both with depth and with position along a 35-m traverse. Additional tests in more resistive regimes where dielectric permittivity is not negligible yield spectral data compatible with the less well known near-surface electrical properties.

  13. Velocity measurements of laser driven flyers backed by high impedance windows

    NASA Astrophysics Data System (ADS)

    Sheffield, S. A.; Rogers, J. W., Jr.; Castaneda, J. N.

    The response of free-standing foils to laser intensity levels of 1,000 to 1,000000 Gw/sq cm was characterized. The response of free-standing and backed foils at much lower intensities, i.e., in the region of 1 to 20 GW/sq cm, was characterized and these flyers are used to initiate insensitive secondary high explosives. The output of a 3.5-J Nd:glass laser with a 16 ns pulse was used to drive 1.5-mm-diameter aluminum flyers. The velocities of both free-standing flyers and flyers backed on the driven side by windows of water, fused silica, or sapphire were measured using optically recording velocity interferometer system (ORVIS). Intensities were on the order of 10 GW/sq cm and velocities as high as 5 km/s were measured for 13-micron/thick, Al flyers. Velocity and acceleration varied only slightly with the shock impedance of the window. Preliminary measurements indicate that pentaerythritol tetranitrate (PETN) at a density of 1.4 grams/cu cm, and HNS-FP (hexanitrostilbene-fine particle) at a density of 1.6 grams/cu cm, can be promptly detonated by 66-micron m-thick, Al flyers impacting at a velocity of near 2.5 km/s.

  14. Velocity measurements of laser driven flyers backed by high impedance windows

    SciTech Connect

    Sheffield, S.A.; Rogers, J.W. Jr.; Castaneda, J.N.

    1985-01-01

    Because of possible applications to inertial confinement fusion, the response of free-standing foils to laser intensity levels of 10/sup 3/ to 10/sup 6/ GW/cm/sup 2/ has been well characterized. Our interest is in characterizing the response of free-standing and backed foils at much lower intensities, i.e., in the region of 1 to 20 GW/cm/sup 2/, and using these flyers to initiate insensitive secondary high explosives. The output of a 3.5-J Nd:glass laser with a 16 ns pulse was used to drive 1.5-mm-diameter aluminum (Al) flyers. The velocities of both free-standing flyers and flyers backed on the driven side by windows of water, fused silica, or sapphire were measured using ORVIS (Optically Recording Velocity Interferometer System). Intensities were on the order of 10 GW/cm/sup 2/ and velocities as high as 5 km/s were measured for 13-..mu..m/thick, Al flyers. Velocity and acceleration were observed to vary only slightly with the shock impedance of the window. Preliminary measurements indicate that PETN (pentaerythritol tetranitrate) at a density of 1.4 grams/cm/sup 3/, and HNS-FP (hexanitrostilbene-fine particle) at a density of 1.6 grams/cm/sup 3/, can be promptly detonated by 66-..mu..m-thick, Al flyers impacting at a velocity of near 2.5 km/s.

  15. Outcomes Measurement in Voice Disorders: Application of an Acoustic Index of Dysphonia Severity

    ERIC Educational Resources Information Center

    Awan, Shaheen N.; Roy, Nelson

    2009-01-01

    Purpose: The purpose of this experiment was to assess the ability of an acoustic model composed of both time-based and spectral-based measures to track change following voice disorder treatment and to serve as a possible treatment outcomes measure. Method: A weighted, four-factor acoustic algorithm consisting of shimmer, pitch sigma, the ratio of…

  16. Model helicopter rotor high-speed impulsive noise: Measured acoustics and blade pressures

    NASA Technical Reports Server (NTRS)

    Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; Schultz, K. J.

    1983-01-01

    A 1/17-scale research model of the AH-1 series helicopter main rotor was tested. Model-rotor acoustic and simultaneous blade pressure data were recorded at high speeds where full-scale helicopter high-speed impulsive noise levels are known to be dominant. Model-rotor measurements of the peak acoustic pressure levels, waveform shapes, and directively patterns are directly compared with full-scale investigations, using an equivalent in-flight technique. Model acoustic data are shown to scale remarkably well in shape and in amplitude with full-scale results. Model rotor-blade pressures are presented for rotor operating conditions both with and without shock-like discontinuities in the radiated acoustic waveform. Acoustically, both model and full-scale measurements support current evidence that above certain high subsonic advancing-tip Mach numbers, local shock waves that exist on the rotor blades ""delocalize'' and radiate to the acoustic far-field.

  17. Acoustics of the piezo-electric pressure probe

    NASA Technical Reports Server (NTRS)

    Dutt, G. S.

    1974-01-01

    Acoustical properties of a piezoelectric device are reported for measuring the pressure in the plasma flow from an MPD arc. A description and analysis of the acoustical behavior in a piezoelectric probe is presented for impedance matching and damping. The experimental results are presented in a set of oscillographic records.

  18. Study of piezo based sensors for acoustic particle detection

    NASA Astrophysics Data System (ADS)

    Anton, G.; Graf, K.; Hößl, J.; Kappes, A.; Karg, T.; Katz, U.; Kretschmer, W.; Kuch, S.; Lahmann, R.; Naumann, C.; Salomon, K.

    2006-11-01

    We present a characterisation of piezo sensors for acoustic particle detection. Electrical impedance, mechanical displacement and the sensitivity of piezo sensors were measured and modelled using a simple equivalent circuit diagram. In addition, finite element simulations were performed to describe the behaviour of the sensors. Their application for acoustic particle detection is discussed.

  19. Passive Acoustic Tomography Tested for Measuring Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Kleppe, John

    2004-01-01

    The requirements of higher performance, better fuel economy, and lower emissions place an increasing premium on knowing the internal operating parameters of jet engines. One of the most important is the gas temperature in the post combustor section of the engine. Typically the gas temperature is measured with a thermocouple probe or by some optical technique such as Rayleigh scattering. Probes, while providing valuable information, have several limitations. The probe signal must be corrected for radiation and conduction losses, probes provide only a point measurement, and probes must be constructed of materials whose melting points are lower than the temperature of the environment into which they are inserted. Some of the disadvantages of probes are overcome by various optical techniques. Nothing needs to be inserted into the flow, and the temperature can be directly related to the signal by known physical laws. However, optical techniques require optical access (i.e., a window) and a light source (such as a laser), and they are very sensitive to the presence of particles in the flow. To overcome these problems, researchers from the NASA Glenn Research Center and The University of Nevada are developing a technique that uses sound instead of light to measure gas temperature. Like optical techniques, it is nonintrusive--no probe need be exposed to the combustion environment--and the temperature is directly related to a measured quantity--the speed of sound, which is proportional to the square root of the absolute temperature. The temperature profile inside the engine is constructed from the differences in arrival time between correlated signals from an array of microphones placed around the circumference of the engine. In much the same way as a complete picture of the inside of your body can be constructed from an array of x-ray photographs taken at different angles, the temperature profile in the engine is constructed from the angular array of microphones. It is

  20. Acoustic Measurements of an Uninstalled Spacecraft Cabin Ventilation Fan Prototype

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle; Brown, Clifford A.; Shook, Tony D.; Winkel, James; Kolacz, John S.; Podboy, Devin M.; Loew, Raymond A.; Mirecki, Julius H.

    2012-01-01

    Sound pressure measurements were recorded for a prototype of a spacecraft cabin ventilation fan in a test in the NASA Glenn Acoustical Testing Laboratory. The axial fan is approximately 0.089 m (3.50 in.) in diameter and 0.223 m (9.00 in.) long and has nine rotor blades and eleven stator vanes. At design point of 12,000 rpm, the fan was predicted to produce a flow rate of 0.709 cu m/s (150 cfm) and a total pressure rise of 925 Pa (3.72 in. of water) at 12,000 rpm. While the fan was designed to be part of a ducted atmospheric revitalization system, no attempt was made to throttle the flow or simulate the installed configuration during this test. The fan was operated at six speeds from 6,000 to 13,500 rpm. A 13-microphone traversing array was used to collect sound pressure measurements along two horizontal planes parallel to the flow direction, two vertical planes upstream of the fan inlet and two vertical planes downstream of the fan exhaust. Measurements indicate that sound at blade passing frequency harmonics contribute significantly to the overall audible noise produced by the fan at free delivery conditions.

  1. Unrestrained acoustic plethysmograph for measuring tidal volume in mice.

    PubMed

    Reynolds, Jeffrey S; Frazer, David G

    2006-09-01

    The traditional method for measurement of tidal volume in unrestrained mice relies on pressure changes induced by a freely respiring animal in a whole body plethysmograph. These changes have been assumed to be the result of thermo-hygrometric differences between respired air and gas within the chamber. It is known, however, that gas compression in the lung can also contribute significantly to changes in plethysmograph pressure. This study describes an acoustic plethysmograph for mice that is capable of measuring the tidal volume time series without the errors associated with the traditional method. The plethysmograph was designed as a resonating cavity at a fixed frequency. It had a sharp resonant peak and was tuned so that changes in body volume produced nearly linear changes in sound amplitude. The plethysmograph was tested with a water filled balloon connected to a syringe pump. The volume of the balloon was varied as a triangle wave with an amplitude of 250 microL. The RMS error between measured and delivered volume was 4.43 microL. A volume step test, performed to assess the response time of the system, showed that the plethysmograph responded in less than one millisecond.

  2. The application of acoustic emission technique to fatigue crack measurement. [in aluminum alloys

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Davis, W. T.; Crews, J. H., Jr.

    1974-01-01

    The applicability of acoustic emission technique to measure fatigue cracks in aluminum alloy specimens was investigated. There are several variables, such as the metallurgical and the physical treatment of the specimen, that can affect the level of acoustic activity of a fatigue specimen. It is therefore recommended that the acoustic emission technique be supplemented by other nondestructive evaluation methods to obtain quantitative data on crack growth.

  3. Experimental and Theoretical Measurements of Concentration Distributions in Acoustic Focusing Devices

    SciTech Connect

    Rose, K A; Fisher, K; Jung, B; Ness, K; Mariella Jr., R P

    2008-06-16

    We describe a modeling approach to capture the particle motion within an acoustic focusing microfluidic device. Our approach combines finite element models for the acoustic forces with analytical models for the fluid motion and uses these force fields to calculate the particle motion in a Brownian dynamics simulation. We compare results for the model with experimental measurements of the focusing efficiency within a microfabricated device. The results show good qualitative agreement over a range of acoustic driving voltages and particle sizes.

  4. Evaluation of acoustic emission technique for crack growth measurement in aeronautical structures

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Davis, W. T.

    1974-01-01

    An investigation has been conducted concerning the possibility to use the acoustic emission technique for the measurement of fatigue crack growth in aluminum alloy specimens. Two types of aluminum alloys were tested in the investigation. It was found that the acoustic emission technique provides a reliable indication of changes in the crack dimensions over relatively short periods of time. The level of acoustic activity serves as an indicator of the size of the cracks.

  5. Measuring The Electric Properties of Planetary Surface Materials With Mutual Impedance (mi) Probes

    NASA Astrophysics Data System (ADS)

    Trautner, R.; Grard, R.

    Mutual Impedance Probes have been developed for a number of ongoing space mis- sions. The HASI/PWA MI probe will determine the electric properties of the atmo- sphere and surface of Saturn's largest moon, Titan, in 2004. The Permittivity Probe of the SESAME instrument package on the Rosetta Lander will attempt to measure the conductivity and permittivity of the cometary surface material. While both instruments have similar objectives, their architecture (design and integration into the spacecraft, electrode geometry) and properties (measurement range and precision) differ signif- icantly. The main features of the Huygens PWA and Rosetta Lander SESAME MI probes are first recapitulated and their expected performances are assessed. A new MI probe prototype employing a linear electrode array for application on mobile platforms or penetrator devices is then described. Results from a recent field test campaign in the Australian desert are presented and the prototype performance is evaluated. New application areas for future MI probes and relevant technology requirements are dis- cussed.

  6. Validity of Four Commercial Bioelectrical Impedance Scales in Measuring Body Fat among Chinese Children and Adolescents.

    PubMed

    Wang, Lin; Hui, Stanley Sai-Chuen

    2015-01-01

    The aim of the study is to examine the validity in predicting body fat percentage (%BF) of different bioelectrical impedance (BIA) devices among Chinese children and adolescents. A total of 255 Chinese children and adolescents aged 9-19 years old participated in the study. %BF was assessed by BIA scales, namely, Biodynamics-310 (Model A), Tanita TBF-543 (Model B), Tanita BC-545 (Model C), and InBody 520 (Model D). Dual-energy X-ray absorptiometry (DXA) was used as the criterion measurement. Lin's concordance correlation coefficients of estimated %BF between Model A, Model B, Model C, and DXA showed poor agreements for both genders. Moderate agreements for %BF were found between DXA and Model D measurements. In boys, differences in %BF were found between DXA and Model B and Model C. No significant %BF differences were found between Model A, Model D, and DXA. However, the two BIA analyzers showed a significant positive correlation between the bias and average %BF between BIA and DXA. In girls, differences in %BF were observed between Model B, Model C, Model D, and DXA. Model A and DXA showed no significant differences of %BF; however, the bias and the average %BF between the BIA and DXA had a significant positive correlation. Using embedded equations in BIA devices should be validated in assessing the %BF of Chinese children and adolescents.

  7. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch.

    PubMed

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H W

    2015-10-23

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves.

  8. RF impedance measurements on the DARHT-II accelerator intercell assembly

    SciTech Connect

    Fawley, William M.; Eylon, Shmuel; Briggs, Richard

    2003-05-05

    We report upon recent experimental measurements made of RF properties of the intercell assembly of the second axis accelerator[1] of Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at LANL. The intercells provide both pumping and diagnostic access to the main DARHT-II beamline. Their design includes a pumping plenum separated from the main beam pipe by return current rods together with RF shielding provided by a copper-coated stainless steel mesh. Measurements using the twin lead technique (see Ref. [2]) at low frequencies (f < 200 MHz) suggest a constant value for the ratio h of the radial and azimuthal magnetic field components to which the transverse impedance is linearly related. We find that these results compare favorably to predictions from a simple analytic, lumped circuit model which includes the effects of the mesh and return current rods. We also present RF loop-to-loop frequency scans above beam pipe cutoff ({approx}600 MHz) showing the existence of many RF modes with relatively high Q's.

  9. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

    PubMed Central

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  10. Measurement of transmission loss characteristics using acoustic intensity techniques at the KU-FRL Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Roskam, J.

    1983-01-01

    The transmission loss characteristics of panels using the acoustic intensity technique is presented. The theoretical formulation, installation of hardware, modifications to the test facility, and development of computer programs and test procedures are described. A listing of all the programs is also provided. The initial test results indicate that the acoustic intensity technique is easily adapted to measure transmission loss characteristics of panels. Use of this method will give average transmission loss values. The fixtures developed to position the microphones along the grid points are very useful in plotting the intensity maps of vibrating panels.

  11. Determining electron temperature for small spherical probes from network analyzer measurements of complex impedance

    NASA Astrophysics Data System (ADS)

    Walker, D. N.; Fernsler, R. F.; Blackwell, D. D.; Amatucci, W. E.

    2008-12-01

    In earlier work, using a network analyzer, it was shown that collisionless resistance (CR) exists in the sheath of a spherical probe when driven by a small rf signal. The CR is inversely proportional to the plasma density gradient at the location where the applied angular frequency equals the plasma frequency ωpe. Recently, efforts have concentrated on a study of the low-to-intermediate frequency response of the probe to the rf signal. At sufficiently low frequencies, the CR is beyond cutoff, i.e., below the plasma frequency at the surface of the probe. Since the electron density at the probe surface decreases as a function of applied (negative) bias, the CR will extend to lower frequencies as the magnitude of negative bias increases. Therefore to eliminate both CR and ion current contributions, the frequencies presently being considered are much greater than the ion plasma frequency, ωpi, but less than the plasma frequency, ωpe(r0), where r0 is the probe radius. It is shown that, in this frequency regime, the complex impedance measurements made with a network analyzer can be used to determine electron temperature. An overview of the theory is presented along with comparisons to data sets made using three stainless steel spherical probes of different sizes in different experimental environments and different plasma parameter regimes. The temperature measurements made by this method are compared to those made by conventional Langmuir probe sweeps; the method shown here requires no curve fitting as is the usual procedure with Langmuir probes when a Maxwell-Boltzmann electron distribution is assumed. The new method requires, however, a solution of the Poisson equation to determine the approximate sheath dimensions and integrals to determine approximate plasma and sheath inductances. The solution relies on the calculation of impedance for a spherical probe immersed in a collisionless plasma and is based on a simple circuit analogy for the plasma. Finally, the

  12. Resonant Acoustic Measurement of Vapor Phase Transport Phenomenon

    NASA Astrophysics Data System (ADS)

    Schuhmann, R. J.; Garrett, S. L.; Matson, J. V.

    2002-12-01

    A major impediment to accurate non steady-state diffusion measurements is the ability to accurately measure and track a rapidly changing gas concentration without disturbing the system. Non-destructive methods that do not interfere with system dynamics have been developed in the past. These methods, however, have tended to be cumbersome or inaccurate at low concentrations. A new experimental approach has been developed to measure gaseous diffusion in free air and through porous materials. The method combines the traditional non steady-state laboratory methodology with resonant acoustic gas analysis. A phase-locked-loop (PLL) resonance frequency tracker is combined with a thermally insulated copper resonator. A piston sealed with a metal bellows excites the fundamental standing wave resonance of the resonator. The PLL maintains a constant phase difference (typically 90§) between the accelerometer mounted on the piston and a microphone near the piston to track the resonance frequency in real time. A capillary or glass bead filled core is fitted into an o-ring sealed opening at the end of the resonator opposite the bellows. The rate at which the tracer gas is replaced by air within the resonator is controlled by the diffusion coefficient of the gas in free air through the capillary (DA) or by the effective diffusion coefficient of the gas through the core (De). The mean molecular weight of the gas mixture in the resonator is directly determined six times each minute from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Average system stability (temperature divided by frequency squared) is better than 350 ppm. DA values for a 0.3-inch diameter capillary were in excellent agreement with published values. De values for porous media samples (0.5 mm glass beads) of four different lengths (1 through 4 inches) using three different tracer gases (He, CH4, Kr) will be reported. Comments will be offered regarding tracer gas

  13. Effect of Electrode Belt and Body Positions on Regional Pulmonary Ventilation- and Perfusion-Related Impedance Changes Measured by Electric Impedance Tomography.

    PubMed

    Ericsson, Elin; Tesselaar, Erik; Sjöberg, Folke

    2016-01-01

    Ventilator-induced or ventilator-associated lung injury (VILI/VALI) is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT) can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion.

  14. Relationship between acoustic measures and judgments of intelligibility in Parkinson's disease: a within-speaker approach.

    PubMed

    Feenaughty, Lynda; Tjaden, Kris; Sussman, Joan

    2014-11-01

    This study investigated the acoustic basis of within-speaker, across-utterance variation in sentence intelligibility for 12 speakers with dysarthria secondary to Parkinson's disease (PD). Acoustic measures were also obtained for 12 healthy controls for comparison to speakers with PD. Speakers read sentences using their typical speech style. Acoustic measures of speech rate, articulatory rate, fundamental frequency, sound pressure level and F2 interquartile range (F2 IQR) were obtained. A group of listeners judged sentence intelligibility using a computerized visual-analog scale. Relationships between judgments of intelligibility and acoustic measures were determined for individual speakers with PD. Relationships among acoustic measures were also quantified. Although considerable variability was noted, articulatory rate, fundamental frequency and F2 IQR were most frequently associated with within-speaker variation in sentence intelligibility. Results suggest that diversity among speakers with PD should be considered when interpreting results from group analyses.

  15. Easy method for measurement of environmental impedance and superconducting phase fluctuations in one-dimensional arrays of Josephson junctions

    NASA Astrophysics Data System (ADS)

    Chien, Wei-Chen; Lin, Kuan-Yu; Liou, Saxon; Ho, I.-Lin; Kuo, Watson

    2017-04-01

    We conduct microwave impedance measurements on a one-dimensional (1D) array of Josephson junctions to experimentally determine the Josephson inductance and shunt resistance of the constituent junctions. The effective Josephson energy provides an estimate of the environmental impedance, which is greatly increased due to phase fluctuations in the neighboring junctions. This enhancement is attributed to the charge solitons in the 1D system. In general, the environmental impedance is dominated by the junction’s normal resistance in the superconducting phase coherent regime, but overwhelmed by zero-bias resistance and differential resistance, respectively, in the Coulomb blockaded regime and in the phase fluctuating regime. The change in phase fluctuations owing to a dc bias agrees with the finite temperature phase diffusion model.

  16. A wideband high common mode rejection ratio amplifier and phase-locked loop demodulator for multifrequency impedance measurement.

    PubMed

    Goovaerts, H G; Faes, T J; Raaijmakers, E; Heethaar, R M

    1998-11-01

    Design considerations and implementation of a multifrequency measuring channel for application in the field of bio-impedance measurement are discussed in this paper. The input amplifier has a differential configuration which is electrically isolated from the remaining circuits. Transformer coupling provides improved common mode rejection when compared to non-isolated input stages. The frequency characteristic of the section between input and demodulator is flat within +/- 0.1 dB between 4 kHz and 1024 kHz. The synchronous demodulator is based on a wideband switched video amplifier. In contrast to commonly used lock--in techniques, the carrier for demodulation is recovered from the input signal by means of a phase-locked loop. This method ensures zero phase shift with respect to the input signal and improves the accuracy of measurement. The system has been developed primarily for thoracic impedance cardiography (TIC) but has also successfully been applied in the field of total body bio-impedance analysis (BIA). At present an electrical impedance tomograph is under development based on the instrumentation described. Results regarding the measurement range and accuracy are given and some recordings of patient data are shown.

  17. Acoustic measurements of a liquefied cohesive sediment bed under waves

    NASA Astrophysics Data System (ADS)

    Mosquera, R.; Groposo, V.; Pedocchi, F.

    2014-04-01

    In this article the response of a cohesive sediment deposit under the action of water waves is studied with the help of laboratory experiments and an analytical model. Under the same regular wave condition three different bed responses were observed depending on the degree of consolidation of the deposit: no bed motion, bed motion of the upper layer after the action of the first waves, and massive bed motion after several waves. The kinematic of the upper 3 cm of the deposit were measured with an ultrasound acoustic profiler, while the pore-water pressure inside the bed was simultaneously measured using several pore pressure sensors. A poro-elastic model was developed to interpret the experimental observations. The model showed that the amplitude of the shear stress increased down into the bed. Then it is possible that the lower layers of the deposit experience plastic deformations, while the upper layers present just elastic deformations. Since plastic deformations in the lower layers are necessary for pore pressure build-up, the analytical model was used to interpret the experimental results and to state that liquefaction of a self consolidated cohesive sediment bed would only occur if the bed yield stress falls within the range defined by the amplitude of the shear stress inside the bed.

  18. On the Use of Experimental Methods to Improve Confidence in Educed Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie R.

    2011-01-01

    Results from impedance eduction methods developed by NASA Langley Research Center are used throughout the acoustic liner community. In spite of recent enhancements, occasional anomalies persist with these methods, generally at frequencies where the liner produces minimal attenuation. This investigation demonstrates an experimental approach to educe impedance with increased confidence over a desired frequency range, by combining results from successive tests with different cavity depths. A series of tests is conducted with three wire-mesh facesheets, for which the results should be weakly dependent on source sound pressure level and mean grazing flow speed. First, a raylometer is used to measure the DC flow resistance of each facesheet. These facesheets are then mounted onto a frame and a normal incidence tube is used to determine their respective acoustic impedance spectra. A comparison of the acoustic resistance component with the DC flow resistance for each facesheet is used to validate the measurement process. Next, each facesheet is successively mounted onto three frames with different cavity depths, and a grazing flow impedance tube is used to educe their respective acoustic impedance spectra with and without mean flow. The no-flow results are compared with those measured in the normal incidence tube to validate the impedance eduction method. Since the anti-resonance frequency varies with cavity depth, each sample provides robust results over a different frequency range. Hence, a combination of results can be used to determine the facesheet acoustic resistance. When combined with the acoustic reactance, observed to be weakly dependent on the source sound pressure level and grazing flow Mach number, the acoustic impedance can be educed with increased confidence. Representative results of these tests are discussed, and the complete database is available in electronic format upon request.

  19. Cold vacuum chamber for diagnostics: Analysis of the measurements at the Diamond Light Source and impedance bench measurements

    NASA Astrophysics Data System (ADS)

    Voutta, R.; Gerstl, S.; Casalbuoni, S.; Grau, A. W.; Holubek, T.; Saez de Jauregui, D.; Bartolini, R.; Cox, M. P.; Longhi, E. C.; Rehm, G.; Schouten, J. C.; Walker, R. P.; Migliorati, M.; Spataro, B.

    2016-05-01

    The beam heat load is an important input parameter needed for the cryogenic design of superconducting insertion devices. Theoretical models taking into account the different heating mechanisms of an electron beam to a cold bore predict smaller values than the ones measured with several superconducting insertion devices installed in different electron storage rings. In order to measure and possibly understand the beam heat load to a cold bore, a cold vacuum chamber for diagnostics (COLDDIAG) has been built. COLDDIAG is equipped with temperature sensors, pressure gauges, mass spectrometers as well as retarding field analyzers which allow to measure the beam heat load, total pressure, and gas content as well as the flux of particles hitting the chamber walls. COLDDIAG was installed in a straight section of the Diamond Light Source (DLS). In a previous paper the experimental equipment as well as the installation of COLDDIAG in the DLS are described [S. Gerstl et al., Phys. Rev. ST Accel. Beams 17, 103201 (2014)]. In this paper we present an overview of all the measurements performed with COLDDIAG at the DLS and their detailed analysis, as well as impedance bench measurements of the cold beam vacuum chamber performed at the Karlsruhe Institute of Technology after removal from the DLS. Relevant conclusions for the cryogenic design of superconducting insertion devices are drawn from the obtained results.

  20. Experimental study of coaxial nozzle exhaust noise. [acoustic measurements

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J. H.; Stone, J. R.

    1979-01-01

    Experimental results are presented for static acoustic model tests of various geometrical configurations of coaxial nozzles operating over a range of flow conditions. The geometrical configurations consisted of nozzles with coplanar and non-coplanar exit planes and various exhaust area ratios. Primary and secondary nozzle flows were varied independently over a range of nozzle pressure ratios from 1.4 to 3.0 and gas temperatures from 280 to 1100 K. Acoustic data are presented for the conventional mode of coaxial nozzle operation as well as for the inverted velocity profile mode. Comparisons are presented to show the effect of configuration and flow changes on the acoustic characteristics of the nozzles.