Science.gov

Sample records for pulse-wave velocity measurement

  1. Blood pulse wave velocity measured by photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Yeh, Chenghung; Hu, Song; Maslov, Konstantin; Wang, Lihong V.

    2013-03-01

    Blood pulse wave velocity (PWV) is an important indicator for vascular stiffness. In this letter, we present electrocardiogram-synchronized photoacoustic microscopy for in vivo noninvasive quantification of the PWV in the peripheral vessels of mice. Interestingly, strong correlation between blood flow speed and ECG were clearly observed in arteries but not in veins. PWV is measured by the pulse travel time and the distance between two spot of a chose vessel, where simultaneously recorded electrocardiograms served as references. Statistical analysis shows a linear correlation between the PWV and the vessel diameter, which agrees with known physiology. Keywords: photoacoustic microscopy, photoacoustic spectroscopy, bilirubin, scattering medium.

  2. Magnetic plethysmograph transducers for local blood pulse wave velocity measurement.

    PubMed

    Nabeel, P M; Joseph, Jayaraj; Sivaprakasam, Mohanasankar

    2014-01-01

    We present the design of magnetic plethysmograph (MPG) transducers for detection of blood pulse waveform and evaluation of local pulse wave velocity (PWV), for potential use in cuffless blood pressure (BP) monitoring. The sensors utilize a Hall effect magnetic field sensor to capture the blood pulse waveform. A strap based design is performed to enable reliable capture of large number of cardiac cycles with relative ease. The ability of the transducer to consistently detect the blood pulse is verified by in-vivo trials on few volunteers. A duality of such transducers is utilized to capture the local PWV at the carotid artery. The pulse transit time (PTT) between the two detected pulse waveforms, measured along a small section of the carotid artery, was evaluated using automated algorithms to ensure consistency of measurements. The correlation between the measured values of local PWV and BP was also investigated. The developed transducers provide a reliable, easy modality for detecting pulse waveform on superficial arteries. Such transducers, used for measurement of local PWV, could potentially be utilized for cuffless, continuous evaluation of BP at various superficial arterial sites.

  3. Noninvasive Method for Measuring Local Pulse Wave Velocity by Dual Pulse Wave Doppler: In Vitro and In Vivo Studies

    PubMed Central

    Wang, Zhen; Yang, Yong; Yuan, Li-jun; Liu, Jie; Duan, Yun-you; Cao, Tie-sheng

    2015-01-01

    Objectives To evaluate the validity and reproducibility of a noninvasive dual pulse wave Doppler (DPWD) method, which involves simultaneous recording of flow velocity of two independent sample volumes with a measurable distance, for measuring the local arterial pulse wave velocity (PWV) through in vitro and in vivo studies. Methods The DPWD mode of Hitachi HI Vision Preirus ultrasound system with a 5–13MHz transducer was used. An in vitro model was designed to compare the PWV of a homogeneous rubber tubing with the local PWV of its middle part measured by DPWD method. In the in vivo study, local PWV of 45 hypertensive patients (25 male, 49.8±3.1 years) and 45 matched healthy subjects (25 male, 49.3±3.0 years) were investigated at the left common carotid artery (LCCA) by DPWD method. Results In the in vitro study, the local PWV measured by DPWP method and the PWV of the homogeneous rubber tubing did not show statistical difference (5.16 ± 0.28 m/s vs 5.03 ± 0.15 m/s, p = 0.075). The coefficient of variation (CV) of the intra- and inter- measurements for local PWV were 3.46% and 4.96%, for the PWV of the homogeneous rubber tubing were 0.99% and 1.98%. In the in vivo study, a significantly higher local PWV of LCCA was found in the hypertensive patients as compared to that in healthy subjects (6.29±1.04m/s vs. 5.31±0.72m/s, P = 0.019). The CV of the intra- and inter- measurements in hypertensive patients were 2.22% and 3.94%, in healthy subjects were 2.07% and 4.14%. Conclusions This study demonstrated the feasibility of the noninvasive DPWD method to determine the local PWV, which was accurate and reproducible not only in vitro but also in vivo studies. This noninvasive echocardiographic method may be illuminating to clinical use. PMID:25786124

  4. Influence of timing algorithm on brachialankle pulse wave velocity measurement.

    PubMed

    Sun, Xin; Li, Ke; Ren, Hongwei; Li, Peng; Wang, Xinpei; Liu, Changchun

    2014-01-01

    The baPWV measurement is a non-invasive and convenient technique in an assessment of arterial stiffness. Despite its widespread application, the influence of different timing algorithms is still unclear. The present study was conducted to investigate the influence of six timing algorithms (MIN, MAX, D1, D2, MDP and INS) on the baPWV measurement and to evaluate the performance of them. Forty-five CAD patients and fifty-five healthy subjects were recruited in this study. A PVR acquisition apparatus was built up for baPWV measurement. The baPWV and other related parameters were calculated separately by the six timing algorithms. The influence and performance of the six algorithms was analyzed. The six timing algorithms generate significantly different baPWV values (left: F=29.036, P<0.001; right: F=40.076, P<0.001). In terms of reproducibility, the MAX has significantly higher CV value (≥ 18.6%) than the other methods, while the INS has the lowest CV value (≤ 2.7%). On the performance of classification, the INS produces the highest AUC values (left: 0.854; right: 0.872). The MIN and D2 also have a passable performance (AUC > 0.8). The choice of timing algorithm affects baPWV values and the quality of measurement. The INS method is recommended for baPWV measurement.

  5. Non-contact measurement of pulse wave velocity using RGB cameras

    NASA Astrophysics Data System (ADS)

    Nakano, Kazuya; Aoki, Yuta; Satoh, Ryota; Hoshi, Akira; Suzuki, Hiroyuki; Nishidate, Izumi

    2016-03-01

    Non-contact measurement of pulse wave velocity (PWV) using red, green, and blue (RGB) digital color images is proposed. Generally, PWV is used as the index of arteriosclerosis. In our method, changes in blood volume are calculated based on changes in the color information, and is estimated by combining multiple regression analysis (MRA) with a Monte Carlo simulation (MCS) model of the transit of light in human skin. After two pulse waves of human skins were measured using RGB cameras, and the PWV was calculated from the difference of the pulse transit time and the distance between two measurement points. The measured forehead-finger PWV (ffPWV) was on the order of m/s and became faster as the values of vital signs raised. These results demonstrated the feasibility of this method.

  6. A new method for measurement of pulse wave velocity in arterial wall

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoming; Kinnick, Randall R.; Fatemi, Mostafa; Greenleaf, James F.

    2003-10-01

    Arterial wall stiffness can be associated with various diseases. The stiffness of an artery can be assessed by measurement of the pulse wave velocity (PWV). PWV is directly related to the Youngs modulus by the well-known Moens-Korteweg equation. Usually, PWV is estimated using the foot-to-foot method. However, the foot of the pressure wave is not very clear due to reflected waves. Also, the pressure wave is normally at a low frequency, hence, the time resolution is low. PWV is an average indicator of artery stiffness between the two measuring points, therefore it is not easy to identify local stiffness. We propose producing a very short pulse wave in the arterial wall using ultrasound radiation force and measuring its propagation speed along the artery by laser. The temporal resolution of this method is in the range of microseconds, which allows PWV to be measured accurately over a few millimeters. Experiments were carried out on a silicone tube in gelatin. PWV was measured by two scanning methods: (1) fixed source and scanning detector, (2) scanning source and fixed detector. Results: PWV was measured at 2 mm/40 μs by both methods. The Doppler technique was also tested which is potentially suitable for clinical applications.

  7. Doppler ultrasound in the measurement of pulse wave velocity: agreement with the Complior method

    PubMed Central

    2011-01-01

    Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84-0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for the measurement of aortic PWV. PMID:21496271

  8. Pulse Wave Velocity and Cardiac Output vs. Heart Rate in Patients with an Implanted Pacemaker Based on Electric Impedance Method Measurement

    NASA Astrophysics Data System (ADS)

    Soukup, Ladislav; Vondra, Vlastimil; Viščor, Ivo; Jurák, Pavel; Halámek, Josef

    2013-04-01

    The methods and device for estimation of cardiac output and measurement of pulse wave velocity simultaneously is presented here. The beat-to-beat cardiac output as well as pulse wave velocity measurement is based on application of electrical impedance method on the thorax and calf. The results are demonstrated in a study of 24 subjects. The dependence of pulse wave velocity and cardiac output on heart rate during rest in patients with an implanted pacemaker was evaluated. The heart rate was changed by pacemaker programming while neither exercise nor drugs were applied. The most important result is that the pulse wave velocity, cardiac output and blood pressure do not depend significantly on heart rate, while the stroke volume is reciprocal proportionally to the heart rate.

  9. Measurement of spatial pulse wave velocity by using a clip-type pulsimeter equipped with a Hall sensor and photoplethysmography.

    PubMed

    Nam, Dong-Hyun; Lee, Woo-Beom; Hong, You-Sik; Lee, Sang-Suk

    2013-04-09

    A prototype of a clip-type pulsimeter equipped with a magnetic field-sensing semiconductor Hall sensor was developed. It has a permanent magnet attached in the "Chwan" position to the center of a radial artery. The clip-type pulsimeter is composed of a hardware system measuring voltage signals. To measure spatial pulse wave velocity (SPWV), the signal from the radial artery pulsimeter and that from the photoplethysmography (PPG) were simultaneously compared. The pulse wave data from a clinical test of 39 clinical participants (male:female = 25:14) with a mean age of 24.36 (±2.35) years was analyzed. The mean SPWV, which was simultaneously measured from the radial artery pulsimeter and PPG, was 0.8 m/s. We suggest the SPWV results were higher for men than women, because of the better vascularity of terminal tissue in men. The findings of this research may be useful for developing a biomedical signal storage device for a U-health-care system.

  10. Arterial pulse wave propagation velocity in healthy dogs by pulse wave Doppler ultrasound.

    PubMed

    Nogueira, Rodrigo B; Pereira, Lucas A; Basso, Alice F; da Fonseca, Ingrid S; Alves, Lorena A

    2017-03-01

    The aim of this study was to prospectively evaluate the carotid-femoral pulse wave velocity (PWV) values in healthy dogs using pulse wave Doppler ultrasound. A secondary aim was to determine the feasibility of this method and to report the intra- and interobserver reproducibilities of the PWV in conscious dogs. The data were studied in 30 healthy, adult, male (n = 15) and female (n = 15) dogs. The time interval marked between the R wave peak of the electrocardiogram and the intersection of the blood flow wave upstroke of the Doppler spectrum with the baseline of zero frequency was determined for the carotid (T1) and for the femoral (T2) arteries. The distance covered by the pulse wave (L) was determined. The PWV was then calculated using the following formula: L/T2 - T1. The mean values of PWV calculated from the total sample (n = 30) evaluated were 13.41 ± 2.20 m/s. No significant statistical difference was observed for the PWV measurements between males (14.82 ± 3.18 m/s) and females (12.64 ± 2.45 m/s). The analysis revealed no intra nor interobserver differences. A reasonable reproducibility of the PWV measurements was showed by intraclass correlation coefficients (ICC), and the coefficients of variation (CV). These data demonstrate that noninvasive vascular Doppler analysis is a feasible and reproducible method to determine the carotid-femoral PWV in dogs.

  11. A Fast Multimodal Ectopic Beat Detection Method Applied for Blood Pressure Estimation Based on Pulse Wave Velocity Measurements in Wearable Sensors

    PubMed Central

    Pflugradt, Maik; Geissdoerfer, Kai; Goernig, Matthias; Orglmeister, Reinhold

    2017-01-01

    Automatic detection of ectopic beats has become a thoroughly researched topic, with literature providing manifold proposals typically incorporating morphological analysis of the electrocardiogram (ECG). Although being well understood, its utilization is often neglected, especially in practical monitoring situations like online evaluation of signals acquired in wearable sensors. Continuous blood pressure estimation based on pulse wave velocity considerations is a prominent example, which depends on careful fiducial point extraction and is therefore seriously affected during periods of increased occurring extrasystoles. In the scope of this work, a novel ectopic beat discriminator with low computational complexity has been developed, which takes advantage of multimodal features derived from ECG and pulse wave relating measurements, thereby providing additional information on the underlying cardiac activity. Moreover, the blood pressure estimations’ vulnerability towards ectopic beats is closely examined on records drawn from the Physionet database as well as signals recorded in a small field study conducted in a geriatric facility for the elderly. It turns out that a reliable extrasystole identification is essential to unsupervised blood pressure estimation, having a significant impact on the overall accuracy. The proposed method further convinces by its applicability to battery driven hardware systems with limited processing power and is a favorable choice when access to multimodal signal features is given anyway. PMID:28098831

  12. Blood characteristics effect on pulse wave velocity.

    PubMed

    Kim, Jong Youn; Yoon, Jihyun; Cho, Minhee; Lee, Byoung-Kwon; Karimi, Ali; Shin, Sehyun

    2013-01-01

    PWV, a surrogate marker for vascular stiffness, can be also expressed by the Bramwell-Hill equation. The effect of blood density to PWV has been ignored, because variation of blood density is assumed to be negligible. In some clinical situation, blood density could be changed, and blood density as a mechanical property of blood flow might affect to PWV. While the elastic property plays an important role in determining the wave propagation in an elastic tube, our assumption is that there might be some relation between blood flow and vascular wall, and that the characteristics of blood flow might influence PWV. This study was objected to investigate the role of mechanical and hemorheologic parameters on PWV in subjects with cardiovascular disease. We have measured and analyzed the PWV, hemorheologic parameters, and other clinical parameters in 814 patients with coronary arterial disease scheduled for coronary angiography. There is no commercial method for measuring whole blood density. So, we defined the density score, which is sum of hemoglobin and total protein. And the hemorheologic parameters were measured within 4 hours after sampling by automated microfluidic hemorheometer. And the effect of all the clinical and hemorheologic parameter on PWV was analyzed by multiple linear regression analysis. Many clinical parameters including age and blood pressure, high shear WBV and ESR as hemorheologic parameters, and density score were correlated well with ba-PWV. However, many clinical variables, high shear WBV and ESR lost the independent significance on multivariable regression analysis. Only age, SBP, and density score were independent variables (p < 0.001). In conclusion, density score as a mechanical property of blood might be suggested as an independent variable influencing PWV in addition to age and blood pressure, but hemorheologic parameters, such as RBC deformability, aggregation, and whole blood viscosity do not affect PWV independently.

  13. Estimated Pulse Wave Velocity Calculated from Age and Mean Arterial Blood Pressure

    PubMed Central

    Greve, Sara V.; Laurent, Stephan; Olsen, Michael H.

    2017-01-01

    In a recently published paper, Greve et al [J Hypertens 2016;34:1279-1289] investigate whether the estimated carotid-femoral pulse wave velocity (ePWV), calculated using an equation derived from the relationship between carotid-femoral pulse wave velocity (cfPWV), age, and blood pressure, predicts cardiovascular disease (CVD) as good as the measured cfPWV. Because ePWV predicts CVD as good as cfPWV, some might wonder whether ePWV could be replaced by cfPWV, which is a time-consuming measurement requiring an expensive apparatus. This question is addressed in this mini-review. PMID:28229052

  14. [Velocity estimation of aortic propagation based on radial pulse wave analysis].

    PubMed

    Clara, Fernando; Blanco, Gustavo; Casarini, Alfredo; Corral, Pablo; Meschino, Gustavo; Scandurra, Adriana

    2011-01-01

    We analyzed the possibility of using the radial pulse wave morphology, obtained by a movement transducer, to evaluate the aortic pulse wave velocity. The radial pulse wave signals were obtained by using a transducer, located on the pulse palpation area, in 167 healthy normotensive male volunteers, ages 20 to 70. The reflected wave was identified in every case. Also, a speed coefficient was defined as the ratio between the individual's height and the time between the maximum systolic wave and the arrival time of the reflected wave. We found that the specified coefficient in normotensive individuals increased linearly with age, in a similar way to the increase in aortic propagation velocity measured by other methods. The procedure was repeated on another set of 125 individuals with hypertension, without other risk factors, aged between the 3rd and 7th decade. This time we found similar values to normotensive individuals only on the 3th decade, and a pronounced increase on the velocity coefficient at advanced ages was observed. These findings support the feasibility of using this type of signals to indirectly evaluate the propagation velocity together with the increase index, a parameter commonly used in pulse wave analysis.

  15. Noninvasive determination of pulse-wave velocity in mice.

    PubMed

    Hartley, C J; Taffet, G E; Michael, L H; Pham, T T; Entman, M L

    1997-07-01

    Some transgenic mice have abnormal vascular function, but arterial geometry and dynamics are difficult to evaluate. To examine whether ultrasonic velocimetry could be used to determine arterial pulse-wave velocity (PWV) in mice, a custom-made 20-MHz pulsed Doppler instrument was used to obtain blood flow velocity signals from the aortic arch and the abdominal aorta 4 cm downstream. The upstroke (foot) of the velocity wave was timed at each site with respect to the R wave of the electrocardiogram, and PWV was calculated by dividing the separation distance by the difference in R-foot times. Doppler determinations were compared with invasive tonometry, and PWV was altered pharmacologically. It was found that the upstrokes of pressure (by tonometry) and velocity were coincident (+/-1 ms) and that PWV could be calculated by either method on exposed vessels. With the use of Doppler methods, pulse transit time was determined noninvasively with +/-1-ms resolution in 140 of 142 attempts in 82 mice. The calculated PWV in mice ranged from 220 to 850 cm/s with vasodilating anesthetics producing the low values and vasoconstricting agents producing the higher values. Thus PWV can be determined noninvasively in mice, is similar to that in other mammals, and responds as expected to vasoactive agents.

  16. Imaging pulse wave velocity in mouse retina using swept-source OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Wei, Wei; Wang, Ruikang K.

    2016-03-01

    Blood vessel dynamics has been a significant subject in cardiology and internal medicine, and pulse wave velocity (PWV) on artery vessels is a classic evaluation of arterial distensibility, and has never been ascertained as a cardiovascular risk marker. The aim of this study is to develop a high speed imaging technique to capture the pulsatile motion on mouse retina arteries with the ability to quantify PWV on any arterial vessels. We demonstrate a new non-invasive method to assess the vessel dynamics on mouse retina. A Swept-source optical coherence tomography (SS-OCT) system is used for imaging micro-scale blood vessel motion. The phase-stabilized SS-OCT provides a typical displacement sensitivity of 20 nm. The frame rate of imaging is ~16 kHz, at A-line rate of ~1.62 MHz, which allows the detection of transient pulse waves with adequate temporal resolution. Imaging volumes with repeated B-scans are obtained on mouse retina capillary bed, and the mouse oxymeter signal is recorded simultaneously. The pulse wave on artery and vein are resolved, and with the synchronized heart beat signal, the temporal delay on different vessel locations is determined. The vessel specific measurement of PWV is achieved for the first time with SS-OCT, for pulse waves propagating more than 100 cm/s. Using the novel methodology of retinal PWV assessment, it is hoped that the clinical OCT scans can provide extended diagnostic information of cardiology functionalities.

  17. Left ventricular ejection time, not heart rate, is an independent correlate of aortic pulse wave velocity.

    PubMed

    Salvi, Paolo; Palombo, Carlo; Salvi, Giovanni Matteo; Labat, Carlos; Parati, Gianfranco; Benetos, Athanase

    2013-12-01

    Several studies showed a positive association between heart rate and pulse wave velocity, a sensitive marker of arterial stiffness. However, no study involving a large population has specifically addressed the dependence of pulse wave velocity on different components of the cardiac cycle. The aim of this study was to explore in subjects of different age the link between pulse wave velocity with heart period (the reciprocal of heart rate) and the temporal components of the cardiac cycle such as left ventricular ejection time and diastolic time. Carotid-femoral pulse wave velocity was assessed in 3,020 untreated subjects (1,107 men). Heart period, left ventricular ejection time, diastolic time, and early-systolic dP/dt were determined by carotid pulse wave analysis with high-fidelity applanation tonometry. An inverse association was found between pulse wave velocity and left ventricular ejection time at all ages (<25 years, r(2) = 0.043; 25-44 years, r(2) = 0.103; 45-64 years, r(2) = 0.079; 65-84 years, r(2) = 0.044; ≥ 85 years, r(2) = 0.022; P < 0.0001 for all). A significant (P < 0.0001) negative but always weaker correlation between pulse wave velocity and heart period was also found, with the exception of the youngest subjects (P = 0.20). A significant positive correlation was also found between pulse wave velocity and dP/dt (P < 0.0001). With multiple stepwise regression analysis, left ventricular ejection time and dP/dt remained the only determinant of pulse wave velocity at all ages, whereas the contribution of heart period no longer became significant. Our data demonstrate that pulse wave velocity is more closely related to left ventricular systolic function than to heart period. This may have methodological and pathophysiological implications.

  18. Estimation of local pulse wave velocity using arterial diameter waveforms: Experimental validation in sheep

    NASA Astrophysics Data System (ADS)

    Graf, S.; Craiem, D.; Barra, J. G.; Armentano, R. L.

    2011-12-01

    Increased arterial stiffness is associated with an increased risk of cardiovascular events. Estimation of arterial stiffness using local pulse wave velocity (PWV) promises to be very useful for noninvasive diagnosis of arteriosclerosis. In this work we estimated in an instrumented sheep, the local aortic pulse wave velocity using two sonomicrometry diameter sensors (separated 7.5 cm) according to the transit time method (PWVTT) with a sampling rate of 4 KHz. We simultaneously measured aortic pressure in order to determine from pressure-diameter loops (PWVPDLoop), the "true" local aortic pulse wave velocity. A pneumatic cuff occluder was implanted in the aorta in order to compare both methods under a wide range of pressure levels. Mean pressure values ranged from 47 to 101 mmHg and mean proximal diameter values from 12.5. to 15.2 mm. There were no significant differences between PWVTT and PWVPDLoop values (451±43 vs. 447±48 cm/s, p = ns, paired t-test). Both methods correlated significantly (R = 0.81, p<0.05). The mean difference between both methods was only -4±29 cm/s, whereas the range of the limits of agreement (mean ± 2 standard deviation) was -61 to +53 cm/s, showing no trend. In conclusion, the diameter waveforms transit time method was found to allow an accurate and precise estimation of the local aortic PWV.

  19. Robust segmentation methods with an application to aortic pulse wave velocity calculation.

    PubMed

    Babin, Danilo; Devos, Daniel; Pižurica, Aleksandra; Westenberg, Jos; Vansteenkiste, Ewout; Philips, Wilfried

    2014-04-01

    Aortic stiffness has proven to be an important diagnostic and prognostic factor of many cardiovascular diseases, as well as an estimate of overall cardiovascular health. Pulse wave velocity (PWV) represents a good measure of the aortic stiffness, while the aortic distensibility is used as an aortic elasticity index. Obtaining the PWV and the aortic distensibility from magnetic resonance imaging (MRI) data requires diverse segmentation tasks, namely the extraction of the aortic center line and the segmentation of aortic regions, combined with signal processing methods for the analysis of the pulse wave. In our study non-contrasted MRI images of abdomen were used in healthy volunteers (22 data sets) for the sake of non-invasive analysis and contrasted magnetic resonance (MR) images were used for the aortic examination of Marfan syndrome patients (8 data sets). In this research we present a novel robust segmentation technique for the PWV and aortic distensibility calculation as a complete image processing toolbox. We introduce a novel graph-based method for the centerline extraction of a thoraco-abdominal aorta for the length calculation from 3-D MRI data, robust to artifacts and noise. Moreover, we design a new projection-based segmentation method for transverse aortic region delineation in cardiac magnetic resonance (CMR) images which is robust to high presence of artifacts. Finally, we propose a novel method for analysis of velocity curves in order to obtain pulse wave propagation times. In order to validate the proposed method we compare the obtained results with manually determined aortic centerlines and a region segmentation by an expert, while the results of the PWV measurement were compared to a validated software (LUMC, Leiden, the Netherlands). The obtained results show high correctness and effectiveness of our method for the aortic PWV and distensibility calculation.

  20. Accurate measurement of the pulse wave delay with imaging photoplethysmography

    PubMed Central

    Kamshilin, Alexei A.; Sidorov, Igor S.; Babayan, Laura; Volynsky, Maxim A.; Giniatullin, Rashid; Mamontov, Oleg V.

    2016-01-01

    Assessment of the cardiovascular parameters using noncontact video-based or imaging photoplethysmography (IPPG) is usually considered as inaccurate because of strong influence of motion artefacts. To optimize this technique we performed a simultaneous recording of electrocardiogram and video frames of the face for 36 healthy volunteers. We found that signal disturbances originate mainly from the stochastically enhanced dichroic notch caused by endogenous cardiovascular mechanisms, with smaller contribution of the motion artefacts. Our properly designed algorithm allowed us to increase accuracy of the pulse-transit-time measurement and visualize propagation of the pulse wave in the facial region. Thus, the accurate measurement of the pulse wave parameters with this technique suggests a sensitive approach to assess local regulation of microcirculation in various physiological and pathological states. PMID:28018731

  1. The age‐dependent association between aortic pulse wave velocity and telomere length

    PubMed Central

    Yasmin; Butcher, Lee; Cockcroft, John R.; Wilkinson, Ian B.; Erusalimsky, Jorge D.; McEniery, Carmel M.

    2017-01-01

    Key points Age significantly modifies the relationship between aortic pulse wave velocity and telomere length.The differential relationships observed between aortic pulse wave velocity and telomere length in younger and older individuals suggest that the links between cellular and vascular ageing reflect a complex interaction between genetic and environmental factors acting over the life‐course. Abstract Ageing is associated with marked large artery stiffening. Telomere shortening, a marker of cellular ageing, is linked with arterial stiffening. However, the results of existing studies are inconsistent, possibly because of the confounding influence of variable exposure to cardiovascular risk factors. Therefore, we investigated the relationship between telomere length (TL) and aortic stiffness in well‐characterized, younger and older healthy adults, who were pre‐selected on the basis of having either low or high aortic pulse wave velocity (aPWV), a robust measure of aortic stiffness. Demographic, haemodynamic and biochemical data were drawn from participants in the Anglo‐Cardiff Collaborative Trial. Two age groups with an equal sex ratio were examined: those aged <30 years (younger) or >50 years (older). Separately for each age group and sex, DNA samples representing the highest (n = 125) and lowest (n = 125) extremes of aPWV (adjusted for blood pressure) were selected for analysis of leukocyte TL. Ultimately, this yielded complete phenotypic data on 904 individuals. In younger subjects, TL was significantly shorter in those with high aPWV vs. those with low aPWV (P = 0.017). By contrast, in older subjects, TL was significantly longer in those with high aPWV (P = 0.001). Age significantly modified the relationship between aPWV and TL (P < 0.001). Differential relationships are observed between aPWV and TL, with an inverse association in younger individuals and a positive association in older individuals. The links between cellular and vascular

  2. Ethnic Differences in and Childhood Influences on Early Adult Pulse Wave Velocity

    PubMed Central

    Silva, Maria J.; Molaodi, Oarabile R.; Enayat, Zinat E.; Cassidy, Aidan; Karamanos, Alexis; Read, Ursula M.; Faconti, Luca; Dall, Philippa; Stansfield, Ben; Harding, Seeromanie

    2016-01-01

    Early determinants of aortic stiffness as pulse wave velocity are poorly understood. We tested how factors measured twice previously in childhood in a multiethnic cohort study, particularly body mass, blood pressure, and objectively assessed physical activity affected aortic stiffness in young adults. Of 6643 London children, aged 11 to 13 years, from 51 schools in samples stratified by 6 ethnic groups with different cardiovascular risk, 4785 (72%) were seen again at aged 14 to 16 years. In 2013, 666 (97% of invited) took part in a young adult (21–23 years) pilot follow-up. With psychosocial and anthropometric measures, aortic stiffness and blood pressure were recorded via an upper arm calibrated Arteriograph device. In a subsample (n=334), physical activity was measured >5 days via the ActivPal. Unadjusted pulse wave velocities in black Caribbean and white UK young men were similar (mean±SD 7.9±0.3 versus 7.6±0.4 m/s) and lower in other groups at similar systolic pressures (120 mm Hg) and body mass (24.6 kg/m2). In fully adjusted regression models, independent of pressure effects, black Caribbean (higher body mass/waists), black African, and Indian young women had lower stiffness (by 0.5–0.8; 95% confidence interval, 0.1–1.1 m/s) than did white British women (6.9±0.2 m/s). Values were separately increased by age, pressure, powerful impacts from waist/height, time spent sedentary, and a reported racism effect (+0.3 m/s). Time walking at >100 steps/min was associated with reduced stiffness (P<0.01). Effects of childhood waist/hip were detected. By young adulthood, increased waist/height ratios, lower physical activity, blood pressure, and psychosocial variables (eg, perceived racism) independently increase arterial stiffness, effects likely to increase with age. PMID:27141061

  3. Reliability assessment for pulse wave measurement using artificial pulse generator.

    PubMed

    Chang, Chi-Wei; Wang, Wei-Kung

    2015-04-01

    This study aimed to assess intrinsic reliabilities of devices for pulse wave measurement (PWM). An artificial pulse generator system was constructed to create a periodic pulse wave. The stability of the periodic output was tested by the DP103 pressure transducer. The pulse generator system was then used to evaluate the TD01C system. Test-re-test and inter-device reliability assessments were conducted on the TD01C system. First, 11 harmonic components of the pulse wave were calculated using Fourier series analysis. For each harmonic component, coefficient of variation (CV), intra-class correlation coefficient (ICC) and Bland-Altman plot were used to determine the degree of reliability of the TD01C system. In addition, device exclusion criteria were pre-specified to improve consistency of devices. The artificial pulse generator system was stable to evaluate intrinsic reliabilities of devices for PWM (ICCs > 0.95, p < 0.001). TD01C was reliable for repeated measurements (ICCs of test-re-test reliability > 0.95, p < 0.001; CVs all < 3%). Device exclusion criteria successfully excluded the device with defect; therefore, the criteria reduced inter-device CVs of harmonics and improved consistency of the selected devices for all harmonic components. This study confirmed the feasibility of intrinsic reliability assessment of devices for PWM using an artificial pulse generator system. Moreover, potential novel findings on the assessment combined with device exclusion criteria could be a useful method to select the measuring devices and to evaluate the qualities of them in PWM.

  4. Effect of viscosity on the wave propagation: Experimental determination of compression and expansion pulse wave velocity in fluid-fill elastic tube.

    PubMed

    Stojadinović, Bojana; Tenne, Tamar; Zikich, Dragoslav; Rajković, Nemanja; Milošević, Nebojša; Lazović, Biljana; Žikić, Dejan

    2015-11-26

    The velocity by which the disturbance travels through the medium is the wave velocity. Pulse wave velocity is one of the main parameters in hemodynamics. The study of wave propagation through the fluid-fill elastic tube is of great importance for the proper biophysical understanding of the nature of blood flow through of cardiovascular system. The effect of viscosity on the pulse wave velocity is generally ignored. In this paper we present the results of experimental measurements of pulse wave velocity (PWV) of compression and expansion waves in elastic tube. The solutions with different density and viscosity were used in the experiment. Biophysical model of the circulatory flow is designed to perform measurements. Experimental results show that the PWV of the expansion waves is higher than the compression waves during the same experimental conditions. It was found that the change in viscosity causes a change of PWV for both waves. We found a relationship between PWV, fluid density and viscosity.

  5. An Experimental-Computational Study of Catheter Induced Alterations in Pulse Wave Velocity in Anesthetized Mice.

    PubMed

    Cuomo, Federica; Ferruzzi, Jacopo; Humphrey, Jay D; Figueroa, C Alberto

    2015-07-01

    Computational methods for solving problems of fluid dynamics and fluid-solid-interactions have advanced to the point that they enable reliable estimates of many hemodynamic quantities, including those important for studying vascular mechanobiology or designing medical devices. In this paper, we use a customized version of the open source code SimVascular to develop a computational model of central artery hemodynamics in anesthetized mice that is informed with experimental data on regional geometries, blood flows and pressures, and biaxial wall properties. After validating a baseline model against available data, we then use the model to investigate the effects of commercially available catheters on the very parameters that they are designed to measure, namely, murine blood pressure and (pressure) pulse wave velocity (PWV). We found that a combination of two small profile catheters designed to measure pressure simultaneously in the ascending aorta and femoral artery increased the PWV due to an overall increase in pressure within the arterial system. Conversely, a larger profile dual-sensor pressure catheter inserted through a carotid artery into the descending thoracic aorta decreased the PWV due to an overall decrease in pressure. In both cases, similar reductions in cardiac output were observed due to increased peripheral vascular resistance. As might be expected, therefore, invasive transducers can alter the very quantities that are designed to measure, yet advanced computational models offer a unique method to evaluate or augment such measurements.

  6. Assessment of aortic pulse wave velocity by ultrasound: a feasibility study in mice

    NASA Astrophysics Data System (ADS)

    Faita, Francesco; Di Lascio, Nicole; Stea, Francesco; Kusmic, Claudia; Sicari, Rosa

    2014-03-01

    Pulse wave velocity (PWV) is considered a surrogate marker of arterial stiffness and could be useful for characterizing cardiovascular disease progression even in mouse models. Aim of this study was to develop an image process algorithm for assessing arterial PWV in mice using ultrasound (US) images only and test it on the evaluation of age-associated differences in abdominal aorta PWV (aaPWV). US scans were obtained from six adult (7 months) and six old (19 months) wild type male mice (strain C57BL6) under gaseous anaesthesia. For each mouse, diameter and flow velocity instantaneous values were achieved from abdominal aorta B-mode and PW-Doppler images; all measurements were obtained using edge detection and contour tracking techniques. Single-beat mean diameter and velocity were calculated and time-aligned, providing the lnD-V loop. aaPWV values were obtained from the slope of the linear part of the loop (the early systolic phase), while relative distension (relD) measurements were calculated from the mean diameter signal. aaPWV values for young mice (3.5±0.52 m/s) were lower than those obtained for older ones (5.12±0.98 m/s) while relD measurements were higher in young (25%±7%) compared with older animals evaluations (15%±3%). All measurements were significantly different between the two groups (P<0.01 both). In conclusion, the proposed image processing technique well discriminate between age groups. Since it provides PWV assessment just from US images, it could represent a simply and useful system for vascular stiffness evaluation at any arterial site in the mouse, even in preclinical small animal models.

  7. Parametric estimation of pulse arrival time: a robust approach to pulse wave velocity.

    PubMed

    Solà, Josep; Vetter, Rolf; Renevey, Philippe; Chételat, Olivier; Sartori, Claudio; Rimoldi, Stefano F

    2009-07-01

    Pulse wave velocity (PWV) is a surrogate of arterial stiffness and represents a non-invasive marker of cardiovascular risk. The non-invasive measurement of PWV requires tracking the arrival time of pressure pulses recorded in vivo, commonly referred to as pulse arrival time (PAT). In the state of the art, PAT is estimated by identifying a characteristic point of the pressure pulse waveform. This paper demonstrates that for ambulatory scenarios, where signal-to-noise ratios are below 10 dB, the performance in terms of repeatability of PAT measurements through characteristic points identification degrades drastically. Hence, we introduce a novel family of PAT estimators based on the parametric modeling of the anacrotic phase of a pressure pulse. In particular, we propose a parametric PAT estimator (TANH) that depicts high correlation with the Complior(R) characteristic point D1 (CC = 0.99), increases noise robustness and reduces by a five-fold factor the number of heartbeats required to obtain reliable PAT measurements.

  8. An innovative numerical approach to resolve the pulse wave velocity in a healthy thoracic aorta model.

    PubMed

    Yang, An-Shik; Wen, Chih-Yung; Tseng, Li-Yu; Chiang, Chih-Chieh; Tseng, Wen-Yih Isaac; Yu, Hsi-Yu

    2014-04-01

    Aortic dissection and atherosclerosis are highly fatal diseases. The development of both diseases is closely associated with highly complex haemodynamics. Thus, in predicting the onset of cardiac disease, it is desirable to obtain a detailed understanding of the flowfield characteristics in the human cardiovascular circulatory system. Accordingly, in this study, a numerical model of a normal human thoracic aorta is constructed using the geometry information obtained from a phase-contrast magnetic resonance imaging (PC-MRI) technique. The interaction between the blood flow and the vessel wall dynamics is then investigated using a coupled fluid-structure interaction (FSI) analysis. The simulations focus specifically on the flowfield characteristics and pulse wave velocity (PWV) of the blood flow. Instead of using a conventional PC-MRI method to measure PWV, we present an innovative application of using the FSI approach to numerically resolve PWV for the assessment of wall compliance in a thoracic aorta model. The estimated PWV for a normal thoracic aorta agrees well with the results obtained via PC-MRI measurement. In addition, simulations which consider the FSI effect yield a lower predicted value of the wall shear stress at certain locations in the cardiac cycle than models which assume a rigid vessel wall. Consequently, the model provides a suitable basis for the future development of more sophisticated methods capable of performing the computer-aided analysis of aortic blood flows.

  9. Metabolomic study of carotid–femoral pulse-wave velocity in women

    PubMed Central

    Menni, Cristina; Mangino, Massimo; Cecelja, Marina; Psatha, Maria; Brosnan, Mary J.; Trimmer, Jeff; Mohney, Robert P.; Chowienczyk, Phil; Padmanabhan, Sandosh; Spector, Tim D.; Valdes, Ana M.

    2015-01-01

    Objective: Carotid–femoral pulse-wave velocity (PWV) is a measure of aortic stiffness that is strongly associated with increased risk of cardiovascular morbidity and mortality. The aim of the current study was to identify the molecular markers and the pathways involved in differences in PWV in women, in order to further understand the regulation of arterial stiffening. Methods: A total of 280 known metabolites were measured in 1797 female twins (age range: 18–84 years) not on any antihypertensive medication. Metabolites associated with PWV (after adjustment for age, BMI, metabolite batch, and family relatedness) were entered into a backward linear regression. Transcriptomic analyses were further performed on the top compounds identified. Results: Twelve metabolites were associated with PWV (P < 1.8 × 10−4). One of the most strongly associated metabolites was uridine, which was not associated with blood pressure (BP) and traditional risk factors but correlated significantly with the gene-expression levels of the purinergic receptor P2RY2 (Beta = −0.010, SE = 0.003, P = 0.007), suggesting that it may play a role in regulating endothelial nitric oxide synthase phosphorylation. On the other hand, phenylacetylglutamine was strongly associated with both PWV and BP. Conclusion: Circulating levels of uridine, phenylacetylglutamine, and serine appear strongly correlated with PWV in women. PMID:25490711

  10. High-intensity interval cycling exercise on wave reflection and pulse wave velocity.

    PubMed

    Kingsley, J Derek; Tai, Yu Lun; Vaughan, Jeremiah; Mayo, Xián

    2016-08-18

    The purpose of the present study was to assess the effects of high-intensity exercise on wave reflection and aortic stiffness. Nine young, healthy men (mean±SD: Age: 22±2 yrs) participated in the study. The high-intensity interval cycling exercise consisted of 3 sets of Wingate Anaerobic Tests (WAT) with 7.5% of bodyweight as resistance and 2 minutes of rest between each set. Measurements were taken at rest and 1 min after completion of the WATs. Brachial and aortic blood pressures, as well as wave reflection characteristics, were measured via pulse wave analysis. Aortic stiffness was assessed via carotid-femoral pulse wave velocity (cfPWV). A repeated-measures ANOVA was used to investigate the effects of the WATs on blood pressure and vascular function across time. There was no change in brachial or aortic systolic pressure from rest to recovery. There was a significant (p<0.05) decrease in brachial diastolic pressure (rest: 73±6 mmHg; recovery: 67±9 mmHg) and aortic diastolic pressure (rest: 75±6 mmHg; recovery: 70±9 mmHg) from rest to recovery. In addition, there was no significant change in the augmentation index (rest: 111.4±6.5%; recovery: 109.8±5.8%, p=0.65) from rest to recovery. However, there was a significant (p<0.05) increase in the augmentation index normalized at 75 bpm (rest: 3.29±9.82; recovery 21.21±10.87) during recovery compared to rest. There was no change in cfPWV (rest: 5.3±0.8 m/sec; recovery: 5.7±0.5m/sec; p=0.09) in response to the WAT. These data demonstrate that high-intensity interval cycling exercise with short rest periods has a non-significant effect on vascular function.

  11. Reference Values of Pulse Wave Velocity in Healthy People from an Urban and Rural Argentinean Population

    PubMed Central

    Díaz, Alejandro; Galli, Cintia; Tringler, Matías; Ramírez, Agustín; Cabrera Fischer, Edmundo Ignacio

    2014-01-01

    In medical practice the reference values of arterial stiffness came from multicenter registries obtained in Asia, USA, Australia and Europe. Pulse wave velocity (PWV) is the gold standard method for arterial stiffness quantification; however, in South America, there are few population-based studies. In this research PWV was measured in healthy asymptomatic and normotensive subjects without history of hypertension in first-degree relatives. Normal PWV and the 95% confidence intervals values were obtained in 780 subjects (39.8 ± 18.5 years) divided into 7 age groups (10–98 years). The mean PWV found was 6.84 m/s ± 1.65. PWV increases linearly with aging with a high degree of correlation (r2 = 0.61; P < 0.05) with low dispersion in younger subjects. PWV progressively increases 6–8% with each decade of life; this tendency is more pronounced after 50 years. A significant increase of PWV over 50 years was demonstrated. This is the first population-based study from urban and rural people of Argentina that provides normal values of the PWV in healthy, normotensive subjects without family history of hypertension. Moreover, the age dependence of PWV values was confirmed. PMID:25215227

  12. 24-h ambulatory recording of aortic pulse wave velocity and central systolic augmentation: a feasibility study.

    PubMed

    Luzardo, Leonella; Lujambio, Inés; Sottolano, Mariana; da Rosa, Alicia; Thijs, Lutgarde; Noboa, Oscar; Staessen, Jan A; Boggia, José

    2012-10-01

    We assessed the feasibility of ambulatory pulse wave analysis by comparing this approach with an established tonometric technique. We investigated 35 volunteers (45.6 years; 51.0% women) exclusively at rest (R study) and 83 volunteers (49.9 years; 61.4% women) at rest and during daytime (1000-2000 h) ambulatory monitoring (R+A study). We recorded central systolic (cSP), diastolic (cDP) and pulse (cPP) pressures, augmentation index (cAI) and pulse wave velocity (PWV) by brachial oscillometry (Mobil-O-Graph 24h PWA Monitor) and radial tonometry (SphygmoCor). We applied the Bland and Altman's statistics. In the R study, tonometric and oscillometric estimates of cSP (105.6 vs. 106.9 mm Hg), cDP (74.6 vs. 74.7 mm Hg), cPP (31.0 vs. 32.1 mm Hg), cAI (21.1 vs. 20.6%) and PWV (7.3 vs. 7.0 m s(-1)) were similar (P0.11). In the R+A study, tonometric vs. oscillometric assessment yielded similar values for cSP (115.4 vs. 113.9 mm Hg; P=0.19) and cAI (26.5 vs. 25.3%; P=0.54), but lower cDP (77.8 vs. 81.9 mm Hg; P<0.0001), so that cPP was higher (37.6 vs. 32.1 mm Hg; P<0.0001). PWV (7.9 vs. 7.4 m s(-1)) was higher (P=0.0002) on tonometric assessment. The differences between tonometric and oscillometric estimates increased (P0.004) with cSP (r=0.37), cAI (r=0.39) and PWV (r=0.39), but not (P0.17) with cDP (r=0.15) or cPP (r=0.13). Irrespective of measurement conditions, brachial oscillometry compared with an established tonometric method provided similar estimates for cSP and systolic augmentation, but slightly underestimated PWV. Pending further validation, ambulatory assessment of central hemodynamic variables is feasible.

  13. Association of pulse wave velocity with total lung capacity: A cross-sectional analysis of the BOLD London study

    PubMed Central

    Amaral, André F.S.; Patel, Jaymini; Gnatiuc, Louisa; Jones, Meinir; Burney, Peter G.J.

    2015-01-01

    Background Low lung function, measured using spirometry, has been associated with mortality from cardiovascular disease, but whether this is explained by airflow obstruction or restriction is a question that remains unanswered. Objectives To assess the association of total lung capacity (TLC), forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) with several cardio-metabolic and inflammatory markers. Methods In the follow up of the Burden of Lung Disease (BOLD) study in London, acceptable post-bronchodilator spirometric, pulse rate, pulse wave velocity and blood pressure data were obtained from 108 participants. Blood samples for measurement of cardio-metabolic and inflammatory markers were also collected from these participants. Association of lung function and volume with the different biomarkers was examined in multivariable linear regression models adjusted for potential confounders. Results Following adjustment for age, sex, height, and ethnicity, TLC (adjusted coefficient = −1.53; 95% CI: −2.57, −0.49) and FVC (adjusted coefficient = −2.66; 95% CI: −4.98, −0.34) were inversely associated with pulse wave velocity, and further adjustment for smoking status, pack-years and body mass index (BMI) did not materially change these results. FEV1 was inversely associated with systolic blood pressure, and adjustment for smoking status, pack-years and BMI made this association stronger (adjusted coefficient = −9.47; 95% CI: −15.62, −3.32). Conclusion The inverse association of pulse wave velocity, which is a marker of cardiovascular disease, with TLC suggests that the association of the former with low FVC is independent of airflow obstruction. The association between FEV1 with systolic blood pressure after adjustment for FVC suggests an association with airflow obstruction rather than with restricted spirometry. PMID:26553156

  14. Pilot Study: Estimation of Stroke Volume and Cardiac Output from Pulse Wave Velocity

    PubMed Central

    Nyhan, Daniel; Berkowitz, Dan E.; Steppan, Jochen; Barodka, Viachaslau

    2017-01-01

    Background Transesophageal echocardiography (TEE) is increasingly replacing thermodilution pulmonary artery catheters to assess hemodynamics in patients at high risk for cardiovascular morbidity. However, one of the drawbacks of TEE compared to pulmonary artery catheters is the inability to measure real time stroke volume (SV) and cardiac output (CO) continuously. The aim of the present proof of concept study was to validate a novel method of SV estimation, based on pulse wave velocity (PWV) in patients undergoing cardiac surgery. Methods This is a retrospective observational study. We measured pulse transit time by superimposing the radial arterial waveform onto the continuous wave Doppler waveform of the left ventricular outflow tract, and calculated SV (SVPWV) using the transformed Bramwell-Hill equation. The SV measured by TEE (SVTEE) was used as a reference. Results A total of 190 paired SV were measured from 28 patients. A strong correlation was observed between SVPWV and SVTEE with the coefficient of determination (R2) of 0.71. A mean difference between the two (bias) was 3.70 ml with the limits of agreement ranging from -20.33 to 27.73 ml and a percentage error of 27.4% based on a Bland-Altman analysis. The concordance rate of two methods was 85.0% based on a four-quadrant plot. The angular concordance rate was 85.9% with radial limits of agreement (the radial sector that contained 95% of the data points) of ± 41.5 degrees based on a polar plot. Conclusions PWV based SV estimation yields reasonable agreement with SV measured by TEE. Further studies are required to assess its utility in different clinical situations. PMID:28060961

  15. An ultrasound-based method for determining pulse wave velocity in superficial arteries.

    PubMed

    Rabben, Stein Inge; Stergiopulos, Nikos; Hellevik, Leif Rune; Smiseth, Otto A; Slørdahl, Stig; Urheim, Stig; Angelsen, Bjørn

    2004-10-01

    In this paper, we present a method for estimating local pulse wave velocity (PWV) solely from ultrasound measurements: the area-flow (QA) method. With the QA method, PWV is estimated as the ratio between change in flow and change in cross-sectional area (PWV = dQ/dA) during the reflection-free period of the cardiac cycle. In four anaesthetized dogs and 21 human subjects (age 23-74) we measured the carotid flow and cross-sectional area non-invasively by ultrasound. As a reference method we used the Bramwell-Hill (BH) equation which estimates PWV from pulse pressure and cross-sectional area. Additionally, we therefore measured brachial pulse pressure by oscillometry in the human subjects, and central aortic pulse pressure by micro-manometry in the dogs. As predicted by the pressure dependency of arterial stiffness, the estimated PWV decreased when the aortic pressure was lowered in two of the dogs. For the human subjects, the QA and BH estimates were correlated (R=0.43, p<0.05) and agreed on average (mean difference of -0.14 m/s). The PWV by the BH method increased with age (p<0.01) whereas the PWV by the QA method tended to increase with age (p<0.1). This corresponded to a larger residual variance (residual = deviation of the estimated PWV from the regression line) for the QA method than for the BH method, indicating different precisions for the two methods. This study illustrates that the simple equation PWV = dQ/dA gives estimates correlated to the PWV of the reference method. However, improvements in the basic measurements seem necessary to increase the precision of the method.

  16. Prediction of Coronary Artery Disease Extent and Severity Using Pulse Wave Velocity

    PubMed Central

    Chiha, Joseph; Mitchell, Paul; Gopinath, Bamini; Burlutsky, George; Plant, Adam; Kovoor, Pramesh; Thiagalingam, Aravinda

    2016-01-01

    Background Pulse-wave velocity (PWV) measures aortic stiffness. It is an independent predictor of cardiovascular events and mortality, yet there is paucity in the literature on its association with the severity and extent of coronary artery disease (CAD). Methods To examine the utility of PWV in predicting CAD burden in men and women the PWV was determined in 344 patients (Men = 266, Women = 78) presenting for invasive coronary angiography for the assessment of suspected CAD. Pearson correlations and multivariate analysis were used to evaluate the relationship between these coronary scores, PWV and traditional cardiovascular risk factors. Results Compared to men, women with chest pain had lower mean Extent scores (19.2 vs. 35.6; p = 0.0001) and Gensini scores (23.6 vs. 41.9; p = 0.0001). PWV was similar between men and women (12.35 ± 3.74 vs. 12.43 ± 4.58; p = 0.88) and correlated with Extent score (r = 0.21, p = 0.0001) but not Gensini or vessel score (r = 0.03, p = 0.64 and r = 0.06, p = 0.26, respectively). PWV was associated with Extent score in men (B = 2.25 ± 0.78, p = 0.004 for men and B = 1.50 ± 0.88, p = 0.09 for women). It was not a predictor of Gensini score (B = -0.10, P = 0.90). Conclusion PWV correlates with the extent of CAD, as measured by the ‘Extent’ score in men more than women. However, it does not correlate with the severity of obstructive CAD in either gender. PMID:28005967

  17. The 24-hour pulse wave velocity, aortic augmentation index, and central blood pressure in normotensive volunteers.

    PubMed

    Kuznetsova, Tatyana Y; Korneva, Viktoria A; Bryantseva, Evgeniya N; Barkan, Vitaliy S; Orlov, Artemy V; Posokhov, Igor N; Rogoza, Anatoly N

    2014-01-01

    The purpose of this study was to examine the pulse wave velocity, aortic augmentation index corrected for heart rate 75 (AIx@75), and central systolic and diastolic blood pressure during 24-hour monitoring in normotensive volunteers. Overall, 467 subjects (206 men and 261 women) were recruited in this study. Participants were excluded from the study if they were less than 19 years of age, had blood test abnormalities, had a body mass index greater than 2 7.5 kg/m(2), had impaired glucose tolerance, or had hypotension or hypertension. Ambulatory blood pressure monitoring (ABPM) with the BPLab(®) device was performed in each subject. ABPM waveforms were analyzed using the special automatic Vasotens(®) algorithm, which allows the calculation of pulse wave velocity, AIx@75, central systolic and diastolic blood pressure for "24-hour", "awake", and "asleep" periods. Circadian rhythms and sex differences in these indexes were identified. Pending further validation in prospective outcome-based studies, our data may be used as preliminary diagnostic values for the BPLab ABPM additional index in adult subjects.

  18. Atorvastatin Treatment Does Not Alter Pulse Wave Velocity in Healthy Adults

    PubMed Central

    Ballard, Kevin D.; Taylor, Beth A.; Capizzi, Jeffrey A.; Grimaldi, Adam S.; White, C. Michael; Thompson, Paul D.

    2014-01-01

    Introduction. Both statins and regular physical activity (PA) reduce arterial stiffness. The present post hoc analysis examined if arterial stiffness was improved with high-dose atorvastatin treatment in healthy adults and whether PA levels magnified this response. We utilized data from a double-blind, random-assignment clinical trial investigating the effects of atorvastatin 80 mg/d for 6 mo on skeletal muscle symptoms. Methods. Central and peripheral arterial pulse wave velocity (PWV) were measured and PA levels assessed at baseline and 6 mo in subjects randomized to atorvastatin (n = 21, 9 men) or placebo (n = 29, 16 men). Results. Baseline participant characteristics, PWV, and PA levels were not different between treatments. Central (means ± SD; 8.7 ± 2.6 to 9.0 ± 2.5 m/sec) and peripheral PWV (9.9 ± 1.3 to 9.8 ± 1.6 m/sec) were unchanged from baseline following atorvastatin treatment (time × drug interaction: P ≥ 0.13). Similarly, PA levels were unaffected by time or treatment. In sex and age adjusted models, baseline levels of PA were not related to changes in PWV with atorvastatin treatment. Conclusion. These data indicate that high-dose atorvastatin treatment for 6 mo does not influence arterial stiffness in healthy adults. Participation in habitual PA did not magnify the vascular effects of statin therapy. This study was registered with ClinicalTrials.gov NCT00609063. PMID:27351006

  19. Comparison of an Oscillometric Method with Cardiac Magnetic Resonance for the Analysis of Aortic Pulse Wave Velocity

    PubMed Central

    Feistritzer, Hans-Josef; Reinstadler, Sebastian J.; Klug, Gert; Kremser, Christian; Seidner, Benjamin; Esterhammer, Regina; Schocke, Michael F.; Franz, Wolfgang-Michael; Metzler, Bernhard

    2015-01-01

    Objectives Pulse wave velocity (PWV) is the proposed gold-standard for the assessment of aortic elastic properties. The aim of this study was to compare aortic PWV determined by a recently developed oscillometric device with cardiac magnetic resonance imaging (CMR). Methods PWV was assessed in 40 volunteers with two different methods. The oscillometric method (PWVOSC) is based on a transfer function from the brachial pressure waves determined by oscillometric blood pressure measurements with a common cuff (Mobil-O-Graph, I.E.M. Stolberg, Germany). CMR was used to determine aortic PWVCMR with the use of the transit time method based on phase-contrast imaging at the level of the ascending and abdominal aorta on a clinical 1.5 Tesla scanner (Siemens, Erlangen, Germany). Results The median age of the study population was 34 years (IQR: 24–55 years, 11 females). A very strong correlation was found between PWVOSC and PWVCMR (r = 0.859, p < 0.001). Mean PWVOSC was 6.7 ± 1.8 m/s and mean PWVCMR was 6.1 ± 1.8 m/s (p < 0.001). Analysis of agreement between the two measurements using Bland-Altman method showed a bias of 0.57 m/s (upper and lower limit of agreement: 2.49 m/s and -1.34 m/s). The corresponding coefficient of variation between both measurements was 15%. Conclusion Aortic pulse wave velocity assessed by transformation of the brachial pressure waveform showed an acceptable agreement with the CMR-derived transit time method. PMID:25612307

  20. Effects of beam steering in pulsed-wave ultrasound velocity estimation.

    PubMed

    Steinman, Aaron H; Yu, Alfred C H; Johnston, K Wayne; Cobbold, Richard S C

    2005-08-01

    Experimental and computer simulation methods have been used to investigate the significance of beam steering as a potential source of error in pulsed-wave flow velocity estimation. By simulating a typical linear-array transducer system as used for spectral flow estimation, it is shown that beam steering can cause an angle offset resulting in a change in the effective beam-flow angle. This offset primarily depends on the F-number and the nominal steering angle. For example, at an F-number of 3 and a beam-flow angle of 70 degrees , the velocity error changed from -5% to + 5% when the steering angle changed from -20 degrees to + 20 degrees . Much higher errors can occur at higher beam-flow angles, with smaller F-numbers and greater steering. Our experimental study used a clinical ultrasound system, a tissue-mimicking phantom and a pulsatile waveform to determine peak flow velocity errors for various steering and beam-flow angles. These errors were found to be consistent with our simulation results.

  1. Pulse Wave Velocity at Early Adulthood: Breastfeeding and Nutrition during Pregnancy and Childhood

    PubMed Central

    Gigante, Denise Petrucci; de Barros, Fernando Celso Lopes Fernandes

    2016-01-01

    Background Pulse wave velocity (PWV) is an early marker of arterial stiffness. Low birthweight, infant feeding and childhood nutrition have been associated with cardiovascular disease in adulthood. In this study, we evaluated the association of PWV at 30 years of age with birth condition and childhood nutrition, among participants of the 1982 Pelotas birth cohort. Methods In 1982, the hospital births in Pelotas, southern Brazil, were identified just after delivery. Those liveborn infants whose family lived in the urban area of the city were examined and have been prospectively followed. At 30 years of age, we tried to follow the whole cohort and PWV was assessed in 1576 participants. Results Relative weight gain from 2 to 4 years was positively associated with PWV. Regarding nutritional status in childhood, PWV was higher among those whose weight-for-age z-score at 4 years was >1 standard deviation above the mean. On the other hand, height gain, birthweight and duration of breastfeeding were not associated with PWV. Conclusion Relative weight gain after 2 years of age is associated with increased PWV, while birthweight and growth in the first two years of life were not associated. These results suggest that the relative increase of weight later in childhood is associated with higher cardiovascular risk. PMID:27073916

  2. Regulation of vascular tone and pulse wave velocity in human muscular conduit arteries: selective effects of nitric oxide donors to dilate muscular arteries relative to resistance vessels.

    PubMed

    Fok, Henry; Jiang, Benyu; Clapp, Brian; Chowienczyk, Phil

    2012-11-01

    Arterial tone in muscular conduit arteries may influence pressure wave reflection through changes in diameter and pulse wave velocity. We examined the relative specificity of vasodilator drugs for radial artery and forearm resistance vessels during intrabrachial arterial infusion. The nitric oxide (NO) donors, nitroglycerine and nitroprusside, and brain natriuretic peptide were compared with the α-adrenergic antagonist phentolamine, calcium-channel antagonist verapamil, and hydralazine. Radial artery diameter was measured by high resolution ultrasound, forearm blood flow by strain gauge plethysmography, and pulse wave velocity by pressure recording cuffs placed over the distal brachial and radial arteries. Norepinephrine was used to constrict the radial artery to generate a greater range of vasodilator tone when examining pulse wave velocity. Despite dilating resistance vasculature, phentolamine and verapamil had little effect on radial artery diameter (mean dilation <9%). By contrast, for comparable actions on resistance vessels, nitroglycerine and nitroprusside but not brain natriuretic peptide had powerful actions to dilate the radial artery (dilations of 31.3 ± 3.6%, 23.6 ± 3.1%, and 9.8 ± 2.0% for nitroglycerine, nitroprusside, and brain natriuretic peptide, respectively). Changes in pulse wave velocity followed those in arterial diameter irrespective of the signaling pathway used to modulate arterial tone (R=-0.89, P<0.05). Basal tone in human muscular arteries is relatively unaffected by α-adrenergic or calcium-channel blockade, but is functionally or directly antagonized by NO donors. The differential response to NO donors suggests that there is potential to manipulate the downstream pathway to confer greater specificity for large arteries with a resultant decrease in pressure wave reflection and systolic blood pressure.

  3. [A calibrated method for blood pressure measurement based on volume pulse wave].

    PubMed

    Youde, Ding; Qinkai, Deng; Feixue, Liang; Jinseng, Guo

    2010-01-01

    Physiology parameters measurement based on volume pulse wave is suitable for the monitoring blood pressure continuously. This paper described that the systolic blood pressure (SBP) and diastolic blood pressure (DBP) can be calibrated by measuring the pulse propagation time, just on one point of finger tip. The volume pulse wave was acquired by lighting the red and infrared LED alternately, and after signal processing, an accelerated pulse wave was obtained. Then by measuring the pulse wave propagation time between the progressive wave and reflected wave, we can find the relationship of the time and the blood pressure, and establish the related systolic blood pressure measurement equation. At the same time, based on the relationship between alternating current and direct current components in the volume pulse waveforms and through regression analysising, the relevant diastolic blood pressure measurement equation can be established. 33 clinical experimentation cases have been worked by dividing them into two groups: training group (18 cases) and control group (15 cases), by comparing with the measuring results of the OMRON electronic sphygmomanometer. The results indicated that the two methods had good coherence. The measurement described is simple and reliable, and may be served as a new method for noninvasively and continuously measurement of blood pressure.

  4. Direct Measurement of Basilar Membrane Motion Using Pulsed-Wave Doppler High-Frequency Ultrasound

    NASA Astrophysics Data System (ADS)

    Torbatian, Z.; Garland, P.; Adamson, R. B. A.; Bance, M.; Brown, J. A.

    2011-11-01

    We present a preliminary report on the use of a new technique for measuring the motion of the basilar membrane, high-frequency ultrasound Doppler vibrometry. Using a custom-built, 1 mm diameter probe, we collected ultrasonic reflections from intracochlear structures and applied pulsed-wave Doppler vibrometry to measure the basilar membrane response to pressure applied in the ear canal.

  5. Independent associations of circulating galectin-3 concentrations with aortic pulse wave velocity and wave reflection in a community sample.

    PubMed

    Libhaber, Elena; Woodiwiss, Angela J; Raymond, Andrew; Gomes, Monica; Maseko, Muzi J; Sareli, Pinhas; Norton, Gavin R

    2015-06-01

    Although the profibrotic inflammatory substance galectin-3 predicts outcomes in the general population, the mechanisms responsible for this effect are uncertain. We aimed to determine whether circulating galectin-3 concentrations are associated with carotid femoral (aortic) pulse wave velocity and aortic reflective wave index (applanation tonometry and SphygmoCor software) in 966 randomly selected participants from a community sample. Galectin-3 concentrations were not independently associated with office (n=966) or 24-hour (n=661) systolic (P=0.88-0.92) or diastolic (P=0.65-0.94) blood pressure. In contrast, with adjustments for age, sex (in all participants), office or 24-hour mean arterial pressure (or systolic blood pressure and pulse pressure), pulse rate, body mass index, regular smoking, regular alcohol intake, total cholesterol concentrations, diabetes mellitus or an glycohemoglobin >6.1%, treatment for hypertension, and estimated glomerular filtration rate, galectin-3 was independently associated with aortic pulse wave velocity in all participants (partial r=0.15, P<0.0001) and reflective wave index in men (partial r=0.13, P<0.02). In 745 participants who had never received antihypertensive therapy, galectin-3 concentrations were similarly independently associated with pulse wave velocity in all participants (partial=0.16, P<0.0001) and reflective wave index in men (partial r=0.15, P<0.02). The blood pressure-independent relations between galectin-3 concentrations and aortic hemodynamics persisted with further adjustments for C-reactive protein concentrations (pulse wave velocity in all participants: partial r=0.14, P<0.0001; reflective wave index in men: partial r=0.12, P<0.05). In conclusion, despite a lack of independent association with brachial blood pressure, the profibrotic inflammatory substance galectin-3 may contribute toward adverse outcomes through an effect on aortic stiffness, an effect that cannot be attributed to general inflammatory

  6. Increased Pulse Wave Velocity Reflecting Arterial Stiffness in Patients with Colorectal Adenomas

    PubMed Central

    Lim, Yun Jeong; Kwack, Won Gun; Lee, Youg-Sup; Hahm, Ki Baik; Kim, Young-Kwon

    2010-01-01

    The obese patients with diabetes or cardiovascular risk factors are associated with increased risk of colorectal cancer as well as adenomas under the shared pathogenesis related to atherosclerosis. Here we determined the association between increased arterial stiffness and colorectal adenomas incorporating parameters including age, gender, waist circumference, body mass index, lipid profiles, fasting glucose, and blood pressure. Subjects who simultaneously underwent colonoscopies and pulse wave velocity (PWV) determinations between July 2005 and September 2006 were analyzed, based on which the subjects were classified into two groups as patients group with colorectal adenomas (n = 49) and control group (n = 200) with normal, non-polypoid benign lesions or hyperplastic polyps. Uni- and multi-variate analyses were performed to calculate the odd ratio for colon adenomas. Based on uni-variate analysis, age, waist circumference, body mass index, heart-femoral PWV (hfPWV), and brachial-ankle PWV were significantly associated with adenomas (p<0.05) and multiple logistic regression analysis showed that the heart-femoral PWV, waist circumference, and the levels of LDL-C were significant risk factor for colorectal adenoma. However, arterial stiffness did not affect the progression of colon adenoma. The finding that hfPWV, reflecting aortic stiffness, was increased in patients with colorectal adenomas lead to conclusion that patients who have prominently increased arterial stiffness can be recommended to undergo colonoscopic examinations and at the same time we also recommend counseling about the risk for atherosclerosis in those who have colorectal adenomas. PMID:21103036

  7. Noninvasive Assessment of Pulse-Wave Velocity and Flow-Mediated Vasodilation in Anesthetized Göttingen Minipigs

    PubMed Central

    Ludvigsen, Trine P; Wiinberg, Niels; Jensen, Christina J; Callesen, Annemette T; Andersen, Regitze W; Jørgensen, Anne Sofie H; Christoffersen, Berit Ø; Pedersen, Henrik D; Moesgaard, Sophia G; Olsen, Lisbeth H

    2014-01-01

    Few methods for noninvasive assessment of arterial stiffness and endothelial dysfunction in porcine models are available. The aim of this study was to evaluate methods for assessment of arterial stiffness and endothelial dysfunction in anesthetized Göttingen minipigs. Pulse-wave velocity (PWV) was assessed in male Göttingen minipigs (n = 8; age approximately 60 wk) by using applanation tonometry of the carotid and femoral arteries. In addition, flow-mediated vasodilation (FMD) was assessed by using vascular ultrasonography of the brachial artery to evaluate endothelial dysfunction. To evaluate the reproducibility of the methods, minipigs were anesthetized by intravenous infusion of ketamine and midazolam and examined every other day for a total of 3 trials. Neither examination day nor systolic, diastolic, or mean arterial blood pressure statistically influenced PWV or FMD. The median interexamination coefficient of variation was 17% for PWV and 59% for FMD. Measured values of PWV corresponded largely to those in clinically healthy humans, but FMD values were lower than expected for lean, young animals. Although the ketamine–midazolam anesthesia we used has been associated with minor hemodynamic effects in vivo, in vitro studies suggest that both drugs are vasodilatory. Therefore anesthesia might have influenced the endothelial response, contributing to the modest FMD response and the concurrent high coefficients of variation that we noted. We conclude that PWV—but not FMD—showed acceptable interexamination variation for its potential application in porcine models. PMID:25527028

  8. Effect of Aerobic versus Resistance Exercise on Pulse Wave Velocity, Intima Media Thickness and Left Ventricular Mass in Obese Adolescents.

    PubMed

    Horner, Katy; Kuk, Jennifer L; Barinas-Mitchell, Emma; Drant, Stacey; DeGroff, Curt; Lee, SoJung

    2015-11-01

    A cardiovascular comorbidity in obese adolescents is increased aortic pulse wave velocity (aPWV), carotid intima-media thickness (cIMT) and left ventricular mass (LVM). We investigated in obese adolescents 1) the risk factors associated with aPWV, cIMT and LVM, and 2) the effects of aerobic (AE) versus resistance (RE) exercise alone (without calorie restriction) on aPWV, cIMT, LVM index (LVMI) and cardiometabolic risk factors. Eighty-one obese adolescents (12-18 yrs, BMI ≥95th percentile) were randomized to 3 months of AE (n = 30), RE (n = 27) or a control group (n = 24). Outcome measures included aPWV, cIMT, LVMI, body composition, cardiorespiratory fitness (CRF), blood pressure (BP) and lipids. At baseline, the strongest correlates of aPWV were body weight (r = .31) and diastolic BP (r = .28); of cIMT were body weight (r=0.26) and CRF (r=-0.25); and of LVMI was CRF (r=0.32) after adjusting for sex and race (p < .05 for all). Despite significant reductions in total fat and improvements in CRF in the AE and RE groups, aPWV, cIMT, LVMI, BP, lipids and body weight did not change as compared with controls (p > .05 for all). Interventions of longer duration or together with weight loss may be required to improve these early biomarkers of CVD in obese adolescents.

  9. The effect of workplace smoking bans on heart rate variability and pulse wave velocity of non-smoking hospitality workers

    PubMed Central

    Rajkumar, Sarah; Schmidt-Trucksäss, Arno; Wellenius, Gregory A.; Bauer, Georg F.; Huynh, Cong Khanh; Moeller, Alexander; Röösli, Martin

    2014-01-01

    Objectives To investigate the effect of a change in second hand smoke (SHS) exposure on heart rate variability (HRV) and pulse wave velocity (PWV), this study utilized a quasi-experimental setting when a smoking ban was introduced. Methods HRV, a quantitative marker of autonomic activity of the nervous system, and PWV, a marker of arterial stiffness, were measured in 55 non-smoking hospitality workers before and 3 to 12 months after a smoking ban and compared to a control group that did not experience an exposure change. SHS exposure was determined with a nicotine specific badge and expressed as inhaled cigarette equivalents per day (CE/d). Results PWV and HRV parameters significantly changed in a dose dependent manner in the intervention group compared to the control group. A one CE/d decrease was associated with a 2.3% (95% CI: 0.2, 4.4; p=0.031) higher root mean square of successive differences (RMSSD), a 5.7 % (95% CI: 0.9, 10.2; p=0.02) higher high frequency component and a 0.72% (95 % CI: 0.40–1.05; p<0.001) lower PWV. Conclusions PWV and HRV significantly improved after introducing smoke-free workplaces indicating a decreased cardiovascular risk. PMID:24504155

  10. Pulse wave transit time measured by imaging photoplethysmography in upper extremities

    NASA Astrophysics Data System (ADS)

    Volynsky, M. A.; Mamontov, O. V.; Sidorov, I. S.; Kamshilin, A. A.

    2016-08-01

    We describe highly reliable measurement method of the pulse wave transit time (PWTT) to human limbs by using simultaneous recordings of imaging photoplethysmography and electrocardiography. High accuracy of measurements was achieved by access to a larger number of statistically independent data obtained simultaneously in different points. The method is characterized by higher diagnostic reliability because of automatic selection of the regions less affected by environmental noise. The technique was tested in the group of 12 young healthy subjects aged from 21 to 33 years. Even though PWTT in right and left hands was comparable after averaging over the whole group of subjects, significant difference in the time delay of pulse wave between the hands was found in several individuals. The technique can be used for early-stage diagnostics of various vascular diseases.

  11. Integrated multiomics approach identifies calcium and integrin-binding protein-2 as a novel gene for pulse wave velocity

    PubMed Central

    Mangino, Massimo; Cecelja, Marina; Menni, Cristina; Tsai, Pei-Chien; Yuan, Wei; Small, Kerrin; Bell, Jordana; Mitchell, Gary F.; Chowienczyk, Phillip; Spector, Tim D.

    2016-01-01

    Background: Carotid-femoral pulse wave velocity (PWV) is an important measure of arterial stiffness, which is an independent predictor of cardiovascular morbidity and mortality. In this study, we used an integrated genetic, epigenetic and transcriptomics approach to uncover novel molecular mechanisms contributing to PWV. Methods and results: We measured PWV in 1505 healthy twins of European descendent. A genomewide association analysis was performed using standardized residual of the inverse of PWV. We identified one single-nucleotide polymorphism (rs7164338) in the calcium and integrin-binding protein-2 (CIB2) gene on chromosome 15q25.1 associated with PWV [β = −0.359, standard error (SE) = 0.07, P = 4.8 × 10–8]. The same variant was also associated with increased CIB2 expression in leucocytes (β = 0.034, SE = 0.008, P = 4.95 × 10–5) and skin (β = 0.072, SE = 0.01, P = 2.35 × 10–9) and with hypomethylation of the gene promoter (β = −0.899, SE = 0.098, P = 3.63 × 10–20). Conclusion: Our data indicate that reduced methylation of the CIB2 promoter in individuals carrying rs7164338 may lead to increased CIB2 expression. Given that CIB2 is thought to regulate intracellular calcium levels, an increase in protein levels may prevent the accumulation of serum calcium and phosphate, ultimately slowing down the process of vascular calcification. This study shows the power of integrating multiple omics to discover novel cardiovascular mechanisms. PMID:26378684

  12. Gene-Diet Interaction between SIRT6 and Soybean Intake for Different Levels of Pulse Wave Velocity

    PubMed Central

    Sun, Kexin; Xiang, Xiao; Li, Na; Huang, Shaoping; Qin, Xueying; Wu, Yiqun; Tang, Xun; Gao, Pei; Li, Jing; Wu, Tao; Chen, Dafang; Hu, Yonghua

    2015-01-01

    Soybean is a common food for the Chinese people. We aimed to investigate the risk for brachial ankle pulse wave velocity (baPWV) with inflammatory-related SNPs and soybean. baPWV was measured, and 16 inflammatory-related SNPs located on ADIPOQ, CDH13, SIRT3, SIRT6, CXCL12, CXCR4, NOS1, PON1 and CDKN2B were genotyped in 1749 Chinese participants recruited from various communities. ADIPOQ rs12495941 (GT/TT vs. GG: crude OR = 1.27, p = 0.044) and SIRT6 rs107251 (CT/TT vs. CC: crude OR = 0.74, p = 0.009) were associated with abnormal baPWV (baPWV ≥ 1700 cm/s). After adjustment for conventional environmental risk factors, rs12495941 was associated with abnormal baPWV (GT/TT vs. GG: adjusted OR = 1.43, p = 0.011), but the association between rs107251 and abnormal baPWV was not significant (CT/TT vs. CC: adjusted OR = 0.83, p = 0.173). The interaction between rs107251 and soybean intake for different levels of baPWV was statistically significant (p = 0.017). Compared with a high level of soybean intake, a low level of soybean intake can significantly decrease the risk of abnormal baPWV in individuals of rs107251 CT/TT genotypes (≤100 vs. >100 g/week: adjusted OR = 0.542, p = 0.003). In this study, associations between ADIPOQ rs12495941, SIRT6 rs107251 and baPWV, as well as an interaction between SIRT6 rs107251 and soybean intake for different levels of baPWV were found. PMID:26114387

  13. Effect of salt intake and potassium supplementation on brachial-ankle pulse wave velocity in Chinese subjects: an interventional study

    PubMed Central

    Wang, Y.; Mu, J.J.; Geng, L.K.; Wang, D.; Ren, K.Y.; Guo, T.S.; Chu, C.; Xie, B.Q.; Liu, F.Q.; Yuan, Z.Y.

    2014-01-01

    Accumulating evidence has suggested that high salt and potassium might be associated with vascular function. The aim of this study was to investigate the effect of salt intake and potassium supplementation on brachial-ankle pulse wave velocity (PWV) in Chinese subjects. Forty-nine subjects (28-65 years of age) were selected from a rural community of northern China. All subjects were sequentially maintained on a low-salt diet for 7 days (3.0 g/day NaCl), a high-salt diet for an additional 7 days (18.0 g/day NaCl), and a high-salt diet with potassium supplementation for a final 7 days (18.0 g/day NaCl+4.5 g/day KCl). Brachial-ankle PWV was measured at baseline and on the last day of each intervention. Blood pressure levels were significantly increased from the low-salt to high-salt diet, and decreased from the high-salt diet to high-salt plus potassium supplementation. Baseline brachial-ankle PWV in salt-sensitive subjects was significantly higher than in salt-resistant subjects. There was no significant change in brachial-ankle PWV among the 3 intervention periods in salt-sensitive, salt-resistant, or total subjects. No significant correlations were found between brachial-ankle PWV and 24-h sodium and potassium excretions. Our study indicates that dietary salt intake and potassium supplementation, at least in the short term, had no significant effect on brachial-ankle PWV in Chinese subjects. PMID:25493387

  14. Detection of cerebral ischemia using the power spectrum of the pulse wave measured by near-infrared spectroscopy.

    PubMed

    Ebihara, Akira; Tanaka, Yuichi; Konno, Takehiko; Kawasaki, Shingo; Fujiwara, Michiyuki; Watanabe, Eiju

    2013-10-01

    The diagnosis and medical treatment of cerebral ischemia are becoming more important due to the increase in the prevalence of cerebrovascular disease. However, conventional methods of evaluating cerebral perfusion have several drawbacks: they are invasive, require physical restraint, and the equipment is not portable, which makes repeated measurements at the bedside difficult. An alternative method is developed using near-infrared spectroscopy (NIRS). NIRS signals are measured at 44 positions (22 on each side) on the fronto-temporal areas in 20 patients with cerebral ischemia. In order to extract the pulse-wave component, the raw total hemoglobin data recorded from each position are band-pass filtered (0.8 to 2.0 Hz) and subjected to a fast Fourier transform to obtain the power spectrum of the pulse wave. The ischemic region is determined by single-photon emission computed tomography. The pulse-wave power in the ischemic region is compared with that in the symmetrical region on the contralateral side. In 17 cases (85%), the pulse-wave power on the ischemic side is significantly lower than that on the contralateral side, which indicates that the transmission of the pulse wave is attenuated in the region with reduced blood flow. Pulse-wave power might be useful as a noninvasive marker of cerebral ischemia.

  15. Consistency of aortic distensibility and pulse wave velocity estimates with respect to the Bramwell-Hill theoretical model: a cardiovascular magnetic resonance study

    PubMed Central

    2011-01-01

    Background Arterial stiffness is considered as an independent predictor of cardiovascular mortality, and is increasingly used in clinical practice. This study aimed at evaluating the consistency of the automated estimation of regional and local aortic stiffness indices from cardiovascular magnetic resonance (CMR) data. Results Forty-six healthy subjects underwent carotid-femoral pulse wave velocity measurements (CF_PWV) by applanation tonometry and CMR with steady-state free-precession and phase contrast acquisitions at the level of the aortic arch. These data were used for the automated evaluation of the aortic arch pulse wave velocity (Arch_PWV), and the ascending aorta distensibility (AA_Distc, AA_Distb), which were estimated from ascending aorta strain (AA_Strain) combined with either carotid or brachial pulse pressure. The local ascending aorta pulse wave velocity AA_PWVc and AA_PWVb were estimated respectively from these carotid and brachial derived distensibility indices according to the Bramwell-Hill theoretical model, and were compared with the Arch_PWV. In addition, a reproducibility analysis of AA_PWV measurement and its comparison with the standard CF_PWV was performed. Characterization according to the Bramwell-Hill equation resulted in good correlations between Arch_PWV and both local distensibility indices AA_Distc (r = 0.71, p < 0.001) and AA_Distb (r = 0.60, p < 0.001); and between Arch_PWV and both theoretical local indices AA_PWVc (r = 0.78, p < 0.001) and AA_PWVb (r = 0.78, p < 0.001). Furthermore, the Arch_PWV was well related to CF_PWV (r = 0.69, p < 0.001) and its estimation was highly reproducible (inter-operator variability: 7.1%). Conclusions The present work confirmed the consistency and robustness of the regional index Arch_PWV and the local indices AA_Distc and AA_Distb according to the theoretical model, as well as to the well established measurement of CF_PWV, demonstrating the relevance of the regional and local CMR indices. PMID

  16. Impact of seasonality and air pollutants on carotid-femoral pulse wave velocity and wave reflection in hypertensive patients

    PubMed Central

    Stea, Francesco; Massetti, Luciano; Taddei, Stefano; Ghiadoni, Lorenzo; Modesti, Pietro Amedeo

    2017-01-01

    Objective The effects of seasonality on blood pressure (BP) and cardiovascular (CV) events are well established, while the influence of seasonality and other environmental factors on arterial stiffness and wave reflection has never been analyzed. This study evaluated whether seasonality (daily number of hours of light) and acute variations in outdoor temperature and air pollutants may affect carotid-femoral pulse wave velocity (PWV) and pressure augmentation. Design and method 731 hypertensive patients (30–88 years, 417 treated) were enrolled in a cross-sectional study during a 5-year period. PWV, central BP, Augmentation Index (AIx) and Augmentation Pressure (AP) were measured in a temperature-controlled (22–24°C) room. Data of the local office of the National Climatic Data Observatory were used to estimate meteorological conditions and air pollutants (PM10, O3, CO, N2O) exposure on the same day. Results PWV (mean value 8.5±1.8 m/s) was related to age (r = 0.467, p<0.001), body mass index (r = 0.132, p<0.001), central systolic (r = 0.414, p<0.001) and diastolic BP (r = 0.093, p = 0.013), daylight hours (r = -0.176, p<0.001), mean outdoor temperature (r = -0.082, p = 0.027), O3 (r = -0.135, p<0.001), CO (r = 0.096, p = 0.012), N2O (r = 0.087, p = 0.022). In multiple linear regression analysis, adjusted for confounders, PWV remained independently associated only with daylight hours (β = -0.170; 95% CI: -0.273 to -0.067, p = 0.001). No significant correlation was found between pressure augmentation and daylight hours, mean temperature or air pollutants. The relationship was stronger in untreated patients and women. Furthermore, a positive, independent association between O3 levels and PWV emerged in untreated patients (β: 0.018; p = 0.029; CI: 0.002 to 0.034) and in women (β: 0.027; p = 0.004; CI: 0.009 to 0.045). Conclusions PWV showed a marked seasonality in hypertensive patients. Environmental O3 levels may acutely reduce arterial stiffness in

  17. Ethnic Differences in and Childhood Influences on Early Adult Pulse Wave Velocity: The Determinants of Adolescent, Now Young Adult, Social Wellbeing, and Health Longitudinal Study.

    PubMed

    Cruickshank, J Kennedy; Silva, Maria J; Molaodi, Oarabile R; Enayat, Zinat E; Cassidy, Aidan; Karamanos, Alexis; Read, Ursula M; Faconti, Luca; Dall, Philippa; Stansfield, Ben; Harding, Seeromanie

    2016-06-01

    Early determinants of aortic stiffness as pulse wave velocity are poorly understood. We tested how factors measured twice previously in childhood in a multiethnic cohort study, particularly body mass, blood pressure, and objectively assessed physical activity affected aortic stiffness in young adults. Of 6643 London children, aged 11 to 13 years, from 51 schools in samples stratified by 6 ethnic groups with different cardiovascular risk, 4785 (72%) were seen again at aged 14 to 16 years. In 2013, 666 (97% of invited) took part in a young adult (21-23 years) pilot follow-up. With psychosocial and anthropometric measures, aortic stiffness and blood pressure were recorded via an upper arm calibrated Arteriograph device. In a subsample (n=334), physical activity was measured >5 days via the ActivPal. Unadjusted pulse wave velocities in black Caribbean and white UK young men were similar (mean±SD 7.9±0.3 versus 7.6±0.4 m/s) and lower in other groups at similar systolic pressures (120 mm Hg) and body mass (24.6 kg/m(2)). In fully adjusted regression models, independent of pressure effects, black Caribbean (higher body mass/waists), black African, and Indian young women had lower stiffness (by 0.5-0.8; 95% confidence interval, 0.1-1.1 m/s) than did white British women (6.9±0.2 m/s). Values were separately increased by age, pressure, powerful impacts from waist/height, time spent sedentary, and a reported racism effect (+0.3 m/s). Time walking at >100 steps/min was associated with reduced stiffness (P<0.01). Effects of childhood waist/hip were detected. By young adulthood, increased waist/height ratios, lower physical activity, blood pressure, and psychosocial variables (eg, perceived racism) independently increase arterial stiffness, effects likely to increase with age.

  18. A database of virtual healthy subjects to assess the accuracy of foot-to-foot pulse wave velocities for estimation of aortic stiffness

    PubMed Central

    Chowienczyk, Phil; Alastruey, Jordi

    2015-01-01

    While central (carotid-femoral) foot-to-foot pulse wave velocity (PWV) is considered to be the gold standard for the estimation of aortic arterial stiffness, peripheral foot-to-foot PWV (brachial-ankle, femoral-ankle, and carotid-radial) are being studied as substitutes of this central measurement. We present a novel methodology to assess theoretically these computed indexes and the hemodynamics mechanisms relating them. We created a database of 3,325 virtual healthy adult subjects using a validated one-dimensional model of the arterial hemodynamics, with cardiac and arterial parameters varied within physiological healthy ranges. For each virtual subject, foot-to-foot PWV was computed from numerical pressure waveforms at the same locations where clinical measurements are commonly taken. Our numerical results confirm clinical observations: 1) carotid-femoral PWV is a good indicator of aortic stiffness and correlates well with aortic PWV; 2) brachial-ankle PWV overestimates aortic PWV and is related to the stiffness and geometry of both elastic and muscular arteries; and 3) muscular PWV (carotid-radial, femoral-ankle) does not capture the stiffening of the aorta and should therefore not be used as a surrogate for aortic stiffness. In addition, our analysis highlights that the foot-to-foot PWV algorithm is sensitive to the presence of reflected waves in late diastole, which introduce errors in the PWV estimates. In this study, we have created a database of virtual healthy subjects, which can be used to assess theoretically the efficiency of physiological indexes based on pulse wave analysis. PMID:26055792

  19. Genetically elevated levels of circulating triglycerides and brachial-ankle pulse wave velocity in a Chinese population.

    PubMed

    Yao, W-M; Zhang, H-F; Zhu, Z-Y; Zhou, Y-L; Liang, N-X; Xu, D-J; Zhou, F; Sheng, Y-H; Yang, R; Gong, L; Yin, Z-J; Chen, F-K; Cao, K-J; Li, X-L

    2013-04-01

    Elevated levels of circulating triglycerides and increased arterial stiffness are associated with cardiovascular disease. Numerous studies have reported an association between levels of circulating triglycerides and arterial stiffness. We used Mendelian randomization to test whether this association is causal. We investigated the association between circulating triglyceride levels, the apolipoprotein A-V (ApoA5) -1131T>C single nucleotide polymorphism and brachial-ankle pulse wave velocity (baPWV) by examining data from 4421 subjects aged 18-74 years who were recruited from the Chinese population. baPWV was significantly associated with the levels of circulating triglycerides after adjusting for age, sex, body mass index (BMI), systolic blood pressure, heart rate, waist-to-hip ratio, antihypertensive treatment and diabetes mellitus status. The -1131C allele was associated with a 5% (95% confidence interval 3-8%) increase in circulating triglycerides (adjusted for age, sex, BMI, waist-to-hip ratio, diabetes mellitus and antihypertensive treatment). Instrumental variable analysis showed that genetically elevated levels of circulating triglycerides were not associated with increased baPWV. These results do not support the hypothesis that levels of circulating triglycerides have a causal role in the development of arterial stiffness.

  20. Photoacoustic microscopy of blood pulse wave

    NASA Astrophysics Data System (ADS)

    Yeh, Chenghung; Hu, Song; Maslov, Konstantin; Wang, Lihong V.

    2012-07-01

    Blood pulse wave velocity (PWV) is an important physiological parameter that characterizes vascular stiffness. In this letter, we present electrocardiogram-synchronized, photoacoustic microscopy for noninvasive quantification of the PWV in the peripheral vessels of living mice. Interestingly, blood pulse wave-induced fluctuations in blood flow speed were clearly observed in arteries and arterioles, but not in veins or venules. Simultaneously recorded electrocardiograms served as references to measure the travel time of the pulse wave between two cross sections of a chosen vessel and vessel segmentation analysis enabled accurate quantification of the travel distance. PWVs were quantified in ten vessel segments from two mice. Statistical analysis shows a linear correlation between the PWV and the vessel diameter which agrees with known physiology.

  1. Carotid-Femoral Pulse Wave Velocity Is Associated With Cerebral White Matter Lesions in Type 2 Diabetes

    PubMed Central

    Laugesen, Esben; Høyem, Pernille; Stausbøl-Grøn, Brian; Mikkelsen, Anders; Thrysøe, Samuel; Erlandsen, Mogens; Christiansen, Jens S.; Knudsen, Søren T.; Hansen, Klavs W.; Kim, Won Y.; Hansen, Troels K.; Poulsen, Per L.

    2013-01-01

    OBJECTIVE Patients with type 2 diabetes have a high incidence of cardiovascular events including stroke. Increased arterial stiffness (AS) predicts cardiovascular events in the general population. Cerebral white matter lesions (WMLs) are associated with an increased risk of stroke. It is unknown whether AS in patients with type 2 diabetes is associated with WMLs. RESEARCH DESIGN AND METHODS We examined 89 patients recently diagnosed with type 2 diabetes (<5 years) and 89 sex- and age-matched controls. AS was assessed with carotid-femoral pulse wave velocity (PWV). WMLs were identified using magnetic resonance imaging and graded qualitatively with the Breteler scale (no/slight changes = 0, moderate changes = 1, severe changes = 2) and semiquantitatively. RESULTS The diabetic population had excellent glycemic control (HbA1c, 6.5% [6.2–6.8]; median [interquartile range {IQR}]) and had, compared with the controls, lower office blood pressure (BP) (127 ± 12/79 ± 8 vs. 132 ± 14/84 ± 10 mmHg) and total cholesterol (4.3[3.9–4.7] vs. 5.6 [5.1–6.4]; mmol/L; median [IQR]), (P < 0.01 for all). Despite this, PWV was higher in the patients with diabetes compared with controls (9.3 ± 2.0 vs. 8.0 ± 1.6 m/s; P < 0.0001). PWV was associated with Breteler score (OR 1.36 [95% CI 1.17–1.58]; P < 0.001) and WML volume (OR 1.32 [95% CI 1.16–1.51]; P < 0.001) per 1 m/s increase in PWV. These associations remained significant when adjusted for age, sex, diabetes, 24-h mean arterial BP, BMI, heart rate, and use of antihypertensives and statins (Breteler score: OR 1.28 [95% CI 1.03–1.60]; P < 0.05 and WML volume: OR 1.30 [95% CI 1.06–1.58]; P < 0.05). CONCLUSIONS PWV was higher among patients with well-controlled type 2 diabetes compared with controls and was independently associated with WMLs. PWV may represent a clinically relevant parameter in the evaluation of cerebrovascular disease risk in type 2 diabetes. PMID:23129135

  2. Carotid femoral pulse wave velocity in type 2 diabetes and hypertension: capturing arterial health effects of step counts

    PubMed Central

    Dasgupta, Kaberi; Rosenberg, Ellen; Joseph, Lawrence; Trudeau, Luc; Garfield, Natasha; Chan, Deborah; Sherman, Mark; Rabasa-Lhoret, Rémi; Daskalopoulou, Stella S.

    2017-01-01

    Objective: Optimal medication use obscures the impact of physical activity on traditional cardiometabolic risk factors. We evaluated the relationship between step counts and carotid-femoral pulse wave velocity (cfPWV), a summative risk indicator, in patients with type 2 diabetes and/or hypertension. Research design and methods: Three hundred and sixty-nine participants were recruited (outpatient clinics; Montreal, Quebec; 2011–2015). Physical activity (pedometer/accelerometer), cfPWV (applanation tonometry), and risk factors (A1C, Homeostatic Model Assessment–Insulin Resistance, blood pressure, lipid profiles) were evaluated. Linear regression models were constructed to quantify the relationship of steps/day with cfPWV. Results: The study population comprised 191 patients with type 2 diabetes and hypertension, 39 with type 2 diabetes, and 139 with hypertension (mean ± SD: age 59.6 ± 11.2 years; BMI 31.3 ± 4.8 kg/m2; 54.2% women). Blood pressure (125/77 ± 15/9 mmHg), A1C (diabetes: 7.7 ± 1.3%; 61 mmol/mol), and low-density lipoprotein cholesterol (diabetes: 2.19 ± 0.8 mmol/l; without diabetes: 3.13 ± 1.1mmol/l) were close to target. Participants averaged 5125 ± 2722 steps/day. Mean cfPWV was 9.8 ± 2.2 m/s. Steps correlated with cfPWV, but not with other risk factors. A 1000 steps/day increment was associated with a 0.1 m/s cfPWV decrement across adjusted models and in subgroup analysis by diabetes status. In a model adjusted for age, sex, BMI, ethnicity, immigrant status, employment, education, diabetes, hypertension, medication classes, the mean cfPWV decrement was 0.11 m/s (95% confidence interval −0.2, −0.02). Conclusions: cfPWV is responsive to step counts in patients who are well controlled on cardioprotective medications. This ability to capture the ‘added value’ of physical activity supports the emerging role of cfPWV in arterial health monitoring. PMID:28129250

  3. Brachial-Ankle Pulse Wave Velocity is Associated with Composite Carotid and Coronary Atherosclerosis in a Middle-Aged Asymptomatic Population

    PubMed Central

    Joo, Hyung Joon; Cho, Sang-A; Cho, Jae-Young; Lee, Seunghun; Park, Jae Hyoung; Hwang, Sung Ho; Hong, Soon Jun; Yu, Cheol Woong

    2016-01-01

    Aim: Although arterial stiffness has been associated with the development of atherosclerosis, the role of brachial-ankle pulse wave velocity (baPWV) for diagnosing composite coronary and carotid atherosclerosis has not been completely elucidated. Method: We enrolled 773 asymptomatic individuals who were referred from 25 public health centers in Seoul and who underwent carotid ultrasonography and coronary computed tomography. Noninvasive hemodynamic parameters, including baPWV, were also measured. Composite coronary and carotid atherosclerosis was defined as follows: 1) coronary artery calcium (CAC) score ≥ 100, 2) coronary artery stenosis (CAS) ≥ 50% of diameter stenosis, 3) carotid intima medial thickness (CIMT) ≥ 0.9 mm, or 4) presence of carotid artery plaque (CAP). Results: The incidence of composite coronary and carotid atherosclerosis was 28.2%. Coronary atherosclerosis (CAC and CAS) was significantly associated with carotid atherosclerosis (CIMT and CAP). Subjects with higher baPWV (highest quartile) had a higher prevalence of composite coronary and carotid atherosclerosis (p < .001). Although multivariate analysis failed to show baPWV as an independent predictor for composite atherosclerosis, baPWV had moderate diagnostic power to detect a subject with more than two positive subclinical atherosclerosis exams [area under the curve (AUC), 0.692]. Conclusion: baPWV was associated with the composite coronary and carotid atherosclerotic burden in a community-based asymptomatic population. PMID:27251176

  4. Robot-assisted gait training improves brachial–ankle pulse wave velocity and peak aerobic capacity in subacute stroke patients with totally dependent ambulation

    PubMed Central

    Han, Eun Young; Im, Sang Hee; Kim, Bo Ryun; Seo, Min Ji; Kim, Myeong Ok

    2016-01-01

    Abstract Objective: Brachial–ankle pulse wave velocity (baPWV) evaluates arterial stiffness and also predicts early outcome in stroke patients. The objectives of this study were to investigate arterial stiffness of subacute nonfunctional ambulatory stroke patients and to compare the effects of robot-assisted gait therapy (RAGT) combined with rehabilitation therapy (RT) on arterial stiffness and functional recovery with those of RT alone. Method: The RAGT group (N = 30) received 30 minutes of robot-assisted gait therapy and 30 minutes of conventional RT, and the control group (N = 26) received 60 minutes of RT, 5 times a week for 4 weeks. baPWV was measured and calculated using an automated device. The patients also performed a symptom-limited graded exercise stress test using a bicycle ergometer, and parameters of cardiopulmonary fitness were recorded. Clinical outcome measures were categorized into 4 categories: activities of daily living, balance, ambulatory function, and paretic leg motor function and were evaluated before and after the 4-week intervention. Results: Both groups exhibited significant functional recovery in all clinical outcome measures after the 4-week intervention. However, peak aerobic capacity, peak heart rate, exercise tolerance test duration, and baPWV improved only in the RAGT group, and the improvements in baPWV and peak aerobic capacity were more noticeable in the RAGT group than in the control group. Conclusion: Robot-assisted gait therapy combined with conventional rehabilitation therapy represents an effective method for reversing arterial stiffness and improving peak aerobic capacity in subacute stroke patients with totally dependent ambulation. However, further large-scale studies with longer term follow-up periods are warranted to measure the effects of RAGT on secondary prevention after stroke. PMID:27741123

  5. Numerical validation of a new method to assess aortic pulse wave velocity from a single recording of a brachial artery waveform with an occluding cuff.

    PubMed

    Trachet, B; Reymond, P; Kips, J; Swillens, A; De Buyzere, M; Suys, B; Stergiopulos, N; Segers, P

    2010-03-01

    Recently a new method has been proposed as a tool to measure arterial pulse wave velocity (PWV), a measure of the stiffness of the large arteries and an emerging parameter used as indicator of clinical cardiovascular risk. The method is based on measurement of brachial blood pressure during supra-systolic pressure inflation of a simple brachial cuff [the device is known as the Arteriograph (Tensiomed, Budapest, Hungary)]. This occlusion yields pronounced first and secondary peaks in the pressure waveform, the latter ascribed to a reflection from the aortic bifurcation, and PWV is calculated as the ratio of twice the jugulum-symphysis distance and the time difference between the two peaks. To test the validity of this working principle, we used a numerical model of the arterial tree to simulate pressures and flows in the normal configuration, and in a configuration with an occluded brachial artery. A pronounced secondary peak was indeed found in the brachial pressure signal of the occluded model, but its timing was only related to brachial stiffness and not to aortic stiffness. We also compared PWV's calculated with three different methods: PWVATG (approximately Arteriograph principle), PWVcar-fem (approximately carotid-femoral PWV, the current clinical gold standard method), and PWVtheor (approximately Bramwell-Hill equation). Both PWVATG (R2=0.94) and PWVcar-fem (R2=0.95) correlated well with PWVtheor, but their numerical values were lower (by 2.17+/-0.42 and 1.08+/-0.70 m/s for PWVATG and PWVcar-fem, respectively). In conclusion, our simulations question the working principle of the Arteriograph. Our data indicate that the method picks up wave reflection phenomena confined to the brachial artery, and derived values of PWV rather reflect the stiffness of the brachial arteries.

  6. Pressure dependency of aortic pulse wave velocity in vivo is not affected by vasoactive substances that alter aortic wall tension ex vivo.

    PubMed

    Butlin, Mark; Lindesay, George; Viegas, Kayla D; Avolio, Alberto P

    2015-05-15

    Aortic stiffness, a predictive parameter in cardiovascular medicine, is blood pressure dependent and experimentally requires isobaric measurement for meaningful comparison. Vasoactive drug administration to change peripheral resistance and blood pressure allows such isobaric comparison but may alter large conduit artery wall tension, directly changing aortic stiffness. This study quantifies effects of sodium nitroprusside (SNP, vasodilator) and phenylephrine (PE, vasoconstrictor) on aortic stiffness measured by aortic pulse wave velocity (aPWV) assessed by invasive pressure catheterization in anaesthetized Sprague-Dawley rats (n = 7). This was compared with nondrug-dependent alteration of blood pressure through reduced venous return induced by partial vena cava occlusion. In vivo drug concentration was estimated by modeling clearance rates. Ex vivo responses of excised thoracic and abdominal aortic rings to drugs was measured using myography. SNP administration did not alter aPWV compared with venous occlusion (P = 0.21-0.87). There was a 5% difference in aPWV with PE administration compared with venous occlusion (P < 0.05). The estimated in vivo maximum concentration of PE (7.0 ± 1.8 ×10(-7) M) and SNP (4.2 ± 0.6 ×10(-7) M) caused ex vivo equivalent contraction of 52 mmHg (thoracic) and 112 mmHg (abdominal) and relaxation of 96% (both abdominal and thoracic), respectively, despite having a negligible effect on aPWV in vivo. This study demonstrates that vasoactive drugs administered to alter systemic blood pressure have a negligible effect on aPWV and provide a useful tool to study pressure-normalized and pressure-dependent aPWV in large conduit arteries in vivo. However, similar drug concentrations affect aortic ring wall tension ex vivo. Future studies investigating in vivo and ex vivo kinetics will need to elucidate mechanisms for this marked difference.

  7. Central blood pressure and pulse wave velocity: relationship to target organ damage and cardiovascular morbidity-mortality in diabetic patients or metabolic syndrome. An observational prospective study. LOD-DIABETES study protocol

    PubMed Central

    2010-01-01

    Background Diabetic patients show an increased prevalence of non-dipping arterial pressure pattern, target organ damage and elevated arterial stiffness. These alterations are associated with increased cardiovascular risk. The objectives of this study are the following: to evaluate the prognostic value of central arterial pressure and pulse wave velocity in relation to the incidence and outcome of target organ damage and the appearance of cardiovascular episodes (cardiovascular mortality, myocardial infarction, chest pain and stroke) in patients with type 2 diabetes mellitus or metabolic syndrome. Methods/Design Design: This is an observational prospective study with 5 years duration, of which the first year corresponds to patient inclusion and initial evaluation, and the remaining four years to follow-up. Setting: The study will be carried out in the urban primary care setting. Study population: Consecutive sampling will be used to include patients diagnosed with type 2 diabetes between 20-80 years of age. A total of 110 patients meeting all the inclusion criteria and none of the exclusion criteria will be included. Measurements: Patient age and sex, family and personal history of cardiovascular disease, and cardiovascular risk factors. Height, weight, heart rate and abdominal circumference. Laboratory tests: hemoglobin, lipid profile, creatinine, microalbuminuria, glomerular filtration rate, blood glucose, glycosylated hemoglobin, blood insulin, fibrinogen and high sensitivity C-reactive protein. Clinical and 24-hour ambulatory (home) blood pressure monitoring and self-measured blood pressure. Common carotid artery ultrasound for the determination of mean carotid intima-media thickness. Electrocardiogram for assessing left ventricular hypertrophy. Ankle-brachial index. Retinal vascular study based on funduscopy with non-mydriatic retinography and evaluation of pulse wave morphology and pulse wave velocity using the SphygmoCor system. The medication used for

  8. The relationship of brachial-ankle pulse wave velocity to future cardiovascular disease events in the general Japanese population: the Takashima Study.

    PubMed

    Takashima, N; Turin, T C; Matsui, K; Rumana, N; Nakamura, Y; Kadota, A; Saito, Y; Sugihara, H; Morita, Y; Ichikawa, M; Hirose, K; Kawakani, K; Hamajima, N; Miura, K; Ueshima, H; Kita, Y

    2014-05-01

    Brachial-ankle pulse wave velocity (baPWV) is a non-invasive measure of arterial stiffness obtained using an automated system. Although baPWVs have been widely used as a non-invasive marker for evaluation of arterial stiffness, evidence for the prognostic value of baPWV in the general population is scarce. In this study, we assessed the association between baPWV and future cardiovascular disease (CVD) incidence in a Japanese population. From 2002 to 2009, baPWV was measured in a total of 4164 men and women without a history of CVD, and they were followed up until the end of 2009 with a median follow-up period of 6.5 years. Hazard ratios (HRs) for CVD incidence according to baPWV levels were calculated using a Cox proportional hazards model adjusted for potential confounding factors, including seated or supine blood pressure (BP). During the follow-up period, we observed 40 incident cases of CVD. In multivariable-adjusted model, baPWV as a continuous variable was not significantly associated with future CVD risk after adjustment for supine BP. However, compared with lower baPWV category (<18 m s(-1)), higher baPWV (< or = 18.0 m s(-1)) was significantly associated with an increased CVD risk (HR: 2.70, 95% confidence interval: 1.18-6.19). Higher baPWV (< or = 18.0 m s(-1)) would be an independent predictor of future CVD event in the general Japanese population.

  9. Independent and Joint Effect of Brachial-Ankle Pulse Wave Velocity and Blood Pressure Control on Incident Stroke in Hypertensive Adults.

    PubMed

    Song, Yun; Xu, Benjamin; Xu, Richard; Tung, Renee; Frank, Eric; Tromble, Wayne; Fu, Tong; Zhang, Weiyi; Yu, Tao; Zhang, Chunyan; Fan, Fangfang; Zhang, Yan; Li, Jianping; Bao, Huihui; Cheng, Xiaoshu; Qin, Xianhui; Tang, Genfu; Chen, Yundai; Yang, Tianlun; Sun, Ningling; Li, Xiaoying; Zhao, Lianyou; Hou, Fan Fan; Ge, Junbo; Dong, Qiang; Wang, Binyan; Xu, Xiping; Huo, Yong

    2016-07-01

    Pulse wave velocity (PWV) has been shown to influence the effects of antihypertensive drugs in the prevention of cardiovascular diseases. Data are limited on whether PWV is an independent predictor of stroke above and beyond hypertension control. This longitudinal analysis examined the independent and joint effect of brachial-ankle PWV (baPWV) with hypertension control on the risk of first stroke. This report included 3310 hypertensive adults, a subset of the China Stroke Primary Prevention Trial (CSPPT) with baseline measurements for baPWV. During a median follow-up of 4.5 years, 111 participants developed first stroke. The risk of stroke was higher among participants with baPWV in the highest quartile than among those in the lower quartiles (6.3% versus 2.4%; hazard ratio, 1.66; 95% confidence interval, 1.06-2.60). Similarly, the participants with inadequate hypertension control had a higher risk of stroke than those with adequate control (5.1% versus 1.8%; hazard ratio, 2.32; 95% confidence interval, 1.49-3.61). When baPWV and hypertension control were examined jointly, participants in the highest baPWV quartile and with inadequate hypertension control had the highest risk of stroke compared with their counterparts (7.5% versus 1.3%; hazard ratio, 3.57; 95% confidence interval, 1.88-6.77). There was a significant and independent effect of high baPWV on stroke as shown among participants with adequate hypertension control (4.2% versus 1.3%; hazard ratio, 2.29, 95% confidence interval, 1.09-4.81). In summary, among hypertensive patients, baPWV and hypertension control were found to independently and jointly affect the risk of first stroke. Participants with high baPWV and inadequate hypertension control had the highest risk of stroke compared with other groups.

  10. Local versus global aortic pulse wave velocity in early atherosclerosis: An animal study in ApoE-/--mice using ultrahigh field MRI

    PubMed Central

    Gotschy, Alexander; Bauer, Wolfgang R.; Winter, Patrick; Nordbeck, Peter; Rommel, Eberhard; Jakob, Peter M.; Herold, Volker

    2017-01-01

    Increased aortic stiffness is known to be associated with atherosclerosis and has a predictive value for cardiovascular events. This study aims to investigate the local distribution of early arterial stiffening due to initial atherosclerotic lesions. Therefore, global and local pulse wave velocity (PWV) were measured in ApoE-/- and wild type (WT) mice using ultrahigh field MRI. For quantification of global aortic stiffness, a new multi-point transit-time (TT) method was implemented and validated to determine the global PWV in the murine aorta. Local aortic stiffness was measured by assessing the local PWV in the upper abdominal aorta, using the flow/area (QA) method. Significant differences between age matched ApoE-/- and WT mice were determined for global and local PWV measurements (global PWV: ApoE-/-: 2.7±0.2m/s vs WT: 2.1±0.2m/s, P<0.03; local PWV: ApoE-/-: 2.9±0.2m/s vs WT: 2.2±0.2m/s, P<0.03). Within the WT mouse group, the global PWV correlated well with the local PWV in the upper abdominal aorta (R2 = 0.75, P<0.01), implying a widely uniform arterial elasticity. In ApoE-/- animals, however, no significant correlation between individual local and global PWV was present (R2 = 0.07, P = 0.53), implying a heterogeneous distribution of vascular stiffening in early atherosclerosis. The assessment of global PWV using the new multi-point TT measurement technique was validated against a pressure wire measurement in a vessel phantom and showed excellent agreement. The experimental results demonstrate that vascular stiffening caused by early atherosclerosis is unequally distributed over the length of large vessels. This finding implies that assessing heterogeneity of arterial stiffness by multiple local measurements of PWV might be more sensitive than global PWV to identify early atherosclerotic lesions. PMID:28207773

  11. Modification over time of pulse wave velocity parallel to changes in aortic BP, as well as in 24-h ambulatory brachial BP.

    PubMed

    Oliveras, A; Segura, J; Suarez, C; García-Ortiz, L; Abad-Cardiel, M; Vigil, L; Gómez-Marcos, M A; Sans Atxer, L; Martell-Claros, N; Ruilope, L M; de la Sierra, A

    2016-03-01

    Arterial stiffness as assessed by carotid-femoral pulse wave velocity (cfPWV) is a marker of preclinical organ damage and a predictor of cardiovascular outcomes, independently of blood pressure (BP). However, limited evidence exists on the association between long-term variation (Δ) on aortic BP (aoBP) and ΔcfPWV. We aimed to evaluate the relationship of ΔBP with ΔcfPWV over time, as assessed by office and 24-h ambulatory peripheral BP, and aoBP. AoBP and cfPWV were evaluated in 209 hypertensive patients with either diabetes or metabolic syndrome by applanation tonometry (Sphygmocor) at baseline(b) and at 12 months of follow-up(fu). Peripheral BP was also determined by using validated oscillometric devices (office(o)-BP) and on an outpatient basis by using a validated (Spacelabs-90207) device (24-h ambulatory BP). ΔcfPWV over time was calculated as follows: ΔcfPWV=[(cfPWVfu-cfPWVb)/cfPWVb] × 100. ΔBP over time resulted from the same formula applied to BP values obtained with the three different measurement techniques. Correlations (Spearman 'Rho') between ΔBP and ΔcfPWV were calculated. Mean age was 62 years, 39% were female and 80% had type 2 diabetes. Baseline office brachial BP (mm Hg) was 143±20/82±12. Follow-up (12 months later) office brachial BP (mm Hg) was 136±20/79±12. ΔcfPWV correlated with ΔoSBP (Rho=0.212; P=0.002), Δ24-h SBP (Rho=0.254; P<0.001), Δdaytime SBP (Rho=0.232; P=0.001), Δnighttime SBP (Rho=0.320; P<0.001) and ΔaoSBP (Rho=0.320; P<0.001). A multiple linear regression analysis included the following independent variables: ΔoSBP, Δ24-h SBP, Δdaytime SBP, Δnighttime SBP and ΔaoSBP. ΔcfPWV was independently associated with Δ24-h SBP (β-coefficient=0.195; P=0.012) and ΔaoSBP (β-coefficient= 0.185; P=0.018). We conclude that changes in both 24-h SBP and aoSBP more accurately reflect changes in arterial stiffness than do office BP measurements.

  12. Laser speckle contrast imaging: age-related changes in microvascular blood flow and correlation with pulse-wave velocity in healthy subjects

    NASA Astrophysics Data System (ADS)

    Khalil, Adil; Humeau-Heurtier, Anne; Mahé, Guillaume; Abraham, Pierre

    2015-05-01

    In the cardiovascular system, the macrocirculation and microcirculation-two subsystems-can be affected by aging. Laser speckle contrast imaging (LSCI) is an emerging noninvasive optical technique that allows the monitoring of microvascular function and can help, using specific data processing, to understand the relationship between the subsystems. Using LSCI, the goals of this study are: (i) to assess the aging effect over microvascular parameters (perfusion and moving blood cells velocity, MBCV) and macrocirculation parameters (pulse-wave velocity, PWV) and (ii) to study the relationship between these parameters. In 16 healthy subjects (20 to 62 years old), perfusion and MBCV computed from LSCI are studied in three physiological states: rest, vascular occlusion, and post-occlusive reactive hyperaemia (PORH). MBCV is computed from a model of velocity distribution. During PORH, the experimental results show a relationship between perfusion and age (R2=0.67) and between MBCV and age (R2=0.72), as well as between PWV and age at rest (R2=0.91). A relationship is also found between perfusion and MBCV for all physiological states (R2=0.98). Relationships between microcirculation and macrocirculation (perfusion-PWV or MBCV-PWV) are found only during PORH with R2=0.76 and R2=0.77, respectively. This approach may prove useful for investigating dysregulation in blood flow.

  13. Effects of first myocardial infarction on left ventricular systolic and diastolic function with the use of mitral annular velocity determined by pulsed wave doppler tissue imaging.

    PubMed

    Alam, M; Wardell, J; Andersson, E; Samad, B A; Nordlander, R

    2000-05-01

    This study was undertaken to assess the effect of a first myocardial infarction (MI) on the systolic and diastolic velocity profiles of the mitral annulus determined by pulsed wave Doppler tissue imaging and thereby evaluate left ventricular (LV) function after MI. Seventy-eight patients with a first MI were examined before discharge. Peak systolic, peak early diastolic, and peak late diastolic velocities were recorded at 4 different sites on the mitral annulus corresponding to the septum, anterior, lateral, and inferior sites of the left ventricle. In addition, the amplitude of mitral annular motion at the 4 above LV sites, the ejection fraction, and conventional Doppler diastolic parameters were recorded. Nineteen age-matched healthy subjects served as controls. Compared with healthy subjects, the MI patients had a significantly reduced peak systolic velocity at the mitral annulus, especially at the infarction sites. A relatively good linear correlation was found between the ejection fraction and the mean systolic velocity from the 4 LV sites (r = 0.74, P <.001). The correlation was also good when the mean peak systolic mitral annular velocity was tested against the magnitude of the mean mitral annular motion (r = 0.77, P <.001). When the patients were divided into 2 different groups with respect to an ejection fraction > or =0.50 or <0.50, a cutoff point of mean systolic mitral annular velocity of > or =7.5 cm/s had a sensitivity of 79% and a specificity of 88% in predicting a preserved global LV systolic function. Similar to systolic velocities, the early diastolic velocity was also reduced, especially at the infarction sites. The peak mitral annular early diastolic velocity correlated well with both LV ejection fraction (r =.66, P <.001) and mean systolic mitral annular motion (r = 0.68, P <.001). However, no correlation existed between the early diastolic velocity and conventional diastolic Doppler parameters. The reduced peak systolic mitral annular velocity

  14. Effect of modest salt reduction on blood pressure, urinary albumin, and pulse wave velocity in white, black, and Asian mild hypertensives.

    PubMed

    He, Feng J; Marciniak, Maciej; Visagie, Elisabeth; Markandu, Nirmala D; Anand, Vidya; Dalton, R Neil; MacGregor, Graham A

    2009-09-01

    A reduction in salt intake lowers blood pressure. However, most previous trials were in whites with few in blacks and Asians. Salt reduction may also reduce other cardiovascular risk factors (eg, urinary albumin excretion, arterial stiffness). However, few well-controlled trials have studied these effects. We carried out a randomized double-blind crossover trial of salt restriction with slow sodium or placebo, each for 6 weeks, in 71 whites, 69 blacks, and 29 Asians with untreated mildly raised blood pressure. From slow sodium to placebo, urinary sodium was reduced from 165+/-58 (+/-SD) to 110+/-49 mmol/24 hours (9.7 to 6.5 g/d salt). With this reduction in salt intake, there was a significant decrease in blood pressure from 146+/-13/91+/-8 to 141+/-12/88+/-9 mm Hg (P<0.001), urinary albumin from 10.2 (IQR: 6.8 to 18.9) to 9.1 (6.6 to 14.0) mg/24 hours (P<0.001), albumin/creatinine ratio from 0.81 (0.47 to 1.43) to 0.66 (0.44 to 1.22) mg/mmol (P<0.001), and carotid-femoral pulse wave velocity from 11.5+/-2.3 to 11.1+/-1.9 m/s (P<0.01). Subgroup analysis showed that the reductions in blood pressure and urinary albumin/creatinine ratio were significant in all groups, and the decrease in pulse wave velocity was significant in blacks only. These results demonstrate that a modest reduction in salt intake, approximately the amount of the current public health recommendations, causes significant falls in blood pressure in all 3 ethnic groups. Furthermore, it reduces urinary albumin and improves large artery compliance. Although both could be attributable to the falls in blood pressure, they may carry additional benefits on reducing cardiovascular disease above that obtained from the blood pressure falls alone.

  15. The impact of ankle brachial index and pulse wave velocity on cardiovascular risk according to SCORE and Framingham scales and sex differences.

    PubMed

    Woźnicka-Leśkiewicz, L; Posadzy-Małaczyńska, A; Juszkat, R

    2015-08-01

    The aim of the study was to evaluate the usefulness of ankle brachial index (ABI) and pulse wave velocity (PWV) in patients with or without coronary artery disease (CAD) and hypertension (HT) in cardiovascular risk prediction. We studied 200 patients randomized to one of four groups: CAD+HT+; CAD+HT-; CAD-HT+; CAD-HT- (Department of Hypertensiology, Angiology and Internal Diseases, Poznan, Poland: 2009-2012). We evaluated: patient age, lipids profile, ABI and PWV. The cardiovascular risks according to SCORE and Framingham scales were assessed. Statistical calculations were performed in StatSoft Statistica 10. The most interesting aspects of this study were: logistic regression model evaluated the simultaneously influence of ABI and PWV on cardiovascular risk by the SCORE scale and logistic regression model evaluated the influence of ABI and PWV on cardiovascular risk according to the Framingham scale. They showed the possibility (SCORE) of more accurate estimation of cardiovascular risk in an individual patient and graduation of this risk in the exemplary patients. Analysis of the assessment of both: ABI and PWV in predicting of cardiovascular risk according to SCORE and Framingham scales using a logistic regression model indicates that the Framingham scale is less precise than the SCORE scale because it underestimates the real high cardiovascular risk.

  16. Measurement of the contrast agent intrinsic and native harmonic response with single transducer pulse waved ultrasound systems.

    PubMed

    Verbeek, X A; Willigers, J M; Brands, P J; Ledoux, L A; Hoeks, A P

    1999-01-01

    Ultrasound contrast agents, i.e., small gas filled microbubbles, enhance the echogenicity of blood and have the potential to be used for tissue perfusion assessment. The contrast agents scatter ultrasound in a nonlinear manner and thereby introduce harmonics in the ultrasound signal. This property is exploited in new ultrasound techniques like harmonic imaging, which aims to display only the contrast agent presence. Much attention has already been given to the physical properties of the contrast agent. The present study focuses on practical aspects of the measurement of the intrinsic harmonic response of ultrasound contrast agents with single transducer pulse waved ultrasound systems. Furthermore, the consequences of two other sources of harmonics are discussed. These sources are the nonlinear distortion of ultrasound in a medium generating native harmonics, and the emitted signal itself which might contain contaminating harmonics. It is demonstrated conceptually and by experiments that optimization of the contrast agent harmonic response measured with a single transducer is governed by the transducer spectral sensitivity distribution rather than the resonance properties of the contrast agent. Both native and contaminating harmonics may be of considerable strength and can be misinterpreted as intrinsic harmonics of the contrast agent. Practical difficulties to filter out the harmonic component selectively, without deteriorating the image, may cause misinterpretation of the fundamental as a harmonic.

  17. The association of 25(OH)D with blood pressure, pulse pressure and carotid-radial pulse wave velocity in African women.

    PubMed

    Kruger, Iolanthé M; Kruger, Marlena C; Doak, Colleen M; Schutte, Aletta E; Huisman, Hugo W; Van Rooyen, Johannes M; Schutte, Rudolph; Malan, Leoné; Malan, Nicolaas T; Fourie, Carla M T; Kruger, Annamarie

    2013-01-01

    High susceptibility of the African population to develop cardiovascular disease obliges us to investigate possible contributing risk factors. Our aim was to determine whether low 25(OH)D status is associated with increased blood pressure and carotid-radial pulse wave velocity in black South African women. We studied 291 urban women (mean age: 57.56±9.00 yrs.). 25(OH)D status was determined by serum 25(OH)D levels. Women were stratified into sufficient (>30 ng/ml), and insufficient/deficient (<30 ng/ml) groups. Cardiovascular variables were compared between groups. Women with low 25(OH)D levels had significantly higher SBP (150.8±27.1 vs. 137.6±21.0), DBP (94.7±14.5 vs. 89.3±12.3) and PP (53.15(50.7;55.7) vs. 46.3(29.4;84.6)) compared to women with sufficient levels. No significant difference was observed with regards to c-rPWV. ANCOVA analyses still revealed significant differences between the two groups with regards to SBP, DBP as well as PP. Partial correlations revealed significant inverse association between SBP and 25(OH)D (p = .04;r = -.12). Women with low 25(OH)D levels were ∼2 times more likely to have high SBP (95% CI: 3.23;1.05). To conclude, women with deficient/insufficient 25(OH)D had significantly higher SBP compared to women with a sufficient 25(OH) status.

  18. Pulse-wave propagation in straight-geometry vessels for stiffness estimation: theory, simulations, phantoms and in vitro findings.

    PubMed

    Shahmirzadi, Danial; Li, Ronny X; Konofagou, Elisa E

    2012-11-01

    Pulse wave imaging (PWI) is an ultrasound-based method for noninvasive characterization of arterial stiffness based on pulse wave propagation. Reliable numerical models of pulse wave propagation in normal and pathological aortas could serve as powerful tools for local pulse wave analysis and a guideline for PWI measurements in vivo. The objectives of this paper are to (1) apply a fluid-structure interaction (FSI) simulation of a straight-geometry aorta to confirm the Moens-Korteweg relationship between the pulse wave velocity (PWV) and the wall modulus, and (2) validate the simulation findings against phantom and in vitro results. PWI depicted and tracked the pulse wave propagation along the abdominal wall of canine aorta in vitro in sequential Radio-Frequency (RF) ultrasound frames and estimates the PWV in the imaged wall. The same system was also used to image multiple polyacrylamide phantoms, mimicking the canine measurements as well as modeling softer and stiffer walls. Finally, the model parameters from the canine and phantom studies were used to perform 3D two-way coupled FSI simulations of pulse wave propagation and estimate the PWV. The simulation results were found to correlate well with the corresponding Moens-Korteweg equation. A high linear correlation was also established between PWV² and E measurements using the combined simulation and experimental findings (R² =  0.98) confirming the relationship established by the aforementioned equation.

  19. Ambulatory aortic blood pressure, wave reflections and pulse wave velocity are elevated during the third in comparison to the second interdialytic day of the long interval in chronic haemodialysis patients

    PubMed Central

    Koutroumbas, Georgios; Georgianos, Panagiotis I.; Sarafidis, Pantelis A.; Protogerou, Athanase; Karpetas, Antonios; Vakianis, Pantelis; Raptis, Vassilios; Liakopoulos, Vassilios; Panagoutsos, Stylianos; Syrganis, Christos; Passadakis, Ploumis

    2015-01-01

    Background Increased arterial stiffness and aortic blood pressure (BP) are independent predictors of cardiovascular outcomes in end-stage renal disease. The 3-day interdialytic interval is associated with elevated risk of cardiovascular morbidity and mortality in haemodialysis. This study investigated differences in ambulatory aortic BP and arterial stiffness between the second and third day of the long interdialytic interval. Methods Ambulatory BP monitoring with Mobil-O-Graph monitor (IEM, Stolberg, Germany) was performed in 55 haemodialysis patients during a 3-day interval. Mobil-O-Graph records oscillometric brachial BP and pulse waves and calculates aortic BP and augmentation index (AIx) as measure of wave reflections, and pulse wave velocity (PWV) as measure of arterial stiffness. Results Ambulatory aortic systolic blood pressure (SBP) and diastolic blood pressure (DBP) were higher during the third versus second interdialytic day (123.6 ± 17.0 versus 118.5 ± 17.1 mmHg, P < 0.001; 81.5 ± 11.8 versus 78 ± 11.9 mmHg, P < 0.001, respectively). Similar differences were noted for brachial BP. Ambulatory AIx and PWV were also significantly increased during the third versus second day (30.5 ± 9.9 versus 28.8 ± 9.9%, P < 0.05; 9.6 ± 2.3 versus 9.4 ± 2.3 m/s, P < 0.001, respectively). Differences between Days 2 and 3 remained significant when day-time and night-time periods were compared separately. Aortic SBP and DBP, AIx and PWV showed gradual increases from the end of dialysis session onwards. Interdialytic weight gain was a strong determinant of the increase in the above parameters. Conclusions This study showed significantly higher ambulatory aortic BP, AIx and PWV levels during the third compared with the second interdialytic day. These findings support a novel pathway for increased cardiovascular risk during the third interdialytic day in haemodialysis. PMID:25920919

  20. Long-term pulse wave velocity outcomes with aerobic and resistance training in kidney transplant recipients – A pilot randomised controlled trial

    PubMed Central

    Koufaki, Pelagia; Mercer, Thomas H.; Lindup, Herolin; Nugent, Eilish; Goldsmith, David; Macdougall, Iain C.; Greenwood, Sharlene A.

    2017-01-01

    Background This pilot study examined long-term pulse wave velocity (PWV) and peak oxygen uptake (VO2peak) outcomes following a 12-week moderate-intensity aerobic or resistance training programme in kidney transplant recipients. Method Single-blind, bi-centre randomised controlled parallel trial. 42 out of 60 participants completed a 9-month follow-up assessment (Aerobic training = 12, Resistance training = 10 and usual care = 20). Participants completed 12 weeks of twice-weekly supervised aerobic or resistance training. Following the 12-week exercise intervention, participants were transitioned to self-managed community exercise activity using motivational interviewing techniques. Usual care participants received usual encouragement for physical activity during routine clinical appointments in the transplant clinic. PWV, VO2peak, blood pressure and body weight were assessed at 12 weeks and 12 months, and compared to baseline. Results ANCOVA analysis, covarying for baseline values, age, and length of time on dialysis pre-transplantation, revealed a significant mean between-group difference in PWV of -1.30 m/sec (95%CI -2.44 to -0.17, p = 0.03) between resistance training and usual care groups. When comparing the aerobic training and usual care groups at 9-month follow-up, there was a mean difference of -1.05 m/sec (95%CI -2.11 to 0.017, p = 0.05). A significant mean between-group difference in relative VO2peak values of 2.2 ml/kg/min (95% CI 0.37 to 4.03, p = 0.02) when comparing aerobic training with usual care was revealed. There was no significant between group differences in body weight or blood pressure. There were no significant adverse effects associated with the interventions. Conclusions Significant between-group differences in 9-month follow-up PWV existed when comparing resistance exercise intervention with usual care. A long-term between-group difference in VO2peak was only evident when comparing aerobic intervention with usual care. This pilot study

  1. Pulsed-wave Doppler tissue imaging velocities in normal geriatric cats and geriatric cats with primary or systemic diseases linked to specific cardiomyopathies in humans, and the influence of age and heart rate upon these velocities.

    PubMed

    Simpson, Kerry E; Gunn-Moore, Danièlle A; Shaw, Darren J; French, Anne T; Dukes-McEwan, Joanna; Moran, Carmel M; Corcoran, Brendan M

    2009-04-01

    Pulsed-wave Doppler tissue imaging (pw-DTI) techniques allow the non-invasive assessment of myocardial dynamics. pw-DTI has demonstrated regional and global diastolic impairment in various forms of human and feline cardiomyopathy. We hypothesise that in geriatric cats with systemic diseases that have been linked to specific cardiomyopathies in human beings, the myocardial velocity profile will be altered when compared to either normal or hypertrophic cardiomyopathy (HCM) cats; and that both age and heart rate have a significant affect upon pw-DTI velocities. The aims of this study were to determine whether the feline M-mode or myocardial velocity profile is altered in geriatric cats with disease states that have been linked to specific cardiomyopathies in humans when compared to normal geriatric cats or geriatric cats with HCM and to determine whether age or heart rate has a significant effect upon pw-DTI velocities within these groups of cats. Sixty-six cats aged 8 years or above were included in the study, and were divided as follows: Unaffected (n=8), basilar septal bulge (BSB) (17), HCM (14), hyperthyroid (HiT(4)) (12) and chronic renal failure (CRF) (15). Systolic blood pressure was normal in all the cats. pw-DTI systolic (S'), early (E') and late diastolic (A') velocities were assessed from standardised sites within the myocardium, and the relationships between these and disease group, age and heart rate were then assessed. In cats with HCM, the E' velocity was decreased at various sites. Conversely, the HiT(4) cats demonstrated increased S' velocities. The only site at which the age of the cat was significantly related to myocardial velocities was the S' velocity from the apical mid-septum. There were also significant positive relationships between heart rate and the magnitude of myocardial S', E' and A' velocities of radial motion and S' and A' velocities of longitudinal motion. pw-DTI detected diastolic dysfunction in untreated cats with HCM and increased

  2. Interferometric phase velocity measurements

    NASA Technical Reports Server (NTRS)

    Kintner, P. M.; Labelle, J.; Kelley, M. C.; Cahill, L. J., Jr.; Moore, T.; Arnoldy, R.

    1984-01-01

    Phase velocities of plasma waves near the lower hybrid frequency were measured with an interferometer composed of two spatially separated electron-density probes. The plasma waves were produced in the F-region ionosphere by an argon ion beam. By calculating the normalized cross spectrum of the plasma waves a coherency of .98 was estimated along with a maximum phase difference of pi/3 radians between the two probes. This implies that the wavelength was 6 meters compared to an O(+) gyroradius of 3.8 meters, and that the phase velocity was 45 km/sec compared to an ion-beam velocity of 12.4 km/sec. These numbers compare favorably with recent predictions of a nonresonant mode produced by a dense ion beam.

  3. Pulse wave imaging in normal, hypertensive and aneurysmal human aortas in vivo: a feasibility study

    NASA Astrophysics Data System (ADS)

    Li, Ronny X.; Luo, Jianwen; Balaram, Sandhya K.; Chaudhry, Farooq A.; Shahmirzadi, Danial; Konofagou, Elisa E.

    2013-07-01

    Arterial stiffness is a well-established biomarker for cardiovascular risk, especially in the case of hypertension. The progressive stages of an abdominal aortic aneurysm (AAA) have also been associated with varying arterial stiffness. Pulse wave imaging (PWI) is a noninvasive, ultrasound imaging-based technique that uses the pulse wave-induced arterial wall motion to map the propagation of the pulse wave and measure the regional pulse wave velocity (PWV) as an index of arterial stiffness. In this study, the clinical feasibility of PWI was evaluated in normal, hypertensive, and aneurysmal human aortas. Radiofrequency-based speckle tracking was used to estimate the pulse wave-induced displacements in the abdominal aortic walls of normal (N = 15, mean age 32.5 ± 10.2 years), hypertensive (N = 13, mean age 60.8 ± 15.8 years), and aneurysmal (N = 5, mean age 71.6 ± 11.8 years) human subjects. Linear regression of the spatio-temporal variation of the displacement waveform in the anterior aortic wall over a single cardiac cycle yielded the slope as the PWV and the coefficient of determination r2 as an approximate measure of the pulse wave propagation uniformity. The aortic PWV measurements in all normal, hypertensive, and AAA subjects were 6.03 ± 1.68, 6.69 ± 2.80, and 10.54 ± 6.52 m s-1, respectively. There was no significant difference (p = 0.15) between the PWVs of the normal and hypertensive subjects while the PWVs of the AAA subjects were significantly higher (p < 0.001) compared to those of the other two groups. Also, the average r2 in the AAA subjects was significantly lower (p < 0.001) than that in the normal and hypertensive subjects. These preliminary results suggest that the regional PWV and the pulse wave propagation uniformity (r2) obtained using PWI, in addition to the PWI images and spatio-temporal maps that provide qualitative visualization of the pulse wave, may potentially provide valuable information for the clinical characterization of aneurysms

  4. Common Genetic Variation in the 3-BCL11B Gene Desert Is Associated With Carotid-Femoral Pulse Wave Velocity and Excess Cardiovascular Disease Risk The AortaGen Consortium

    PubMed Central

    Mitchell, Gary F.; Verwoert, Germaine C.; Tarasov, Kirill V.; Isaacs, Aaron; Smith, Albert V.; Yasmin; Rietzschel, Ernst R.; Tanaka, Toshiko; Liu, Yongmei; Parsa, Afshin; Najjar, Samer S.; O’Shaughnessy, Kevin M.; Sigurdsson, Sigurdur; De Buyzere, Marc L.; Larson, Martin G.; Sie, Mark P.S.; Andrews, Jeanette S.; Post, Wendy S.; Mattace-Raso, Francesco U.S.; McEniery, Carmel M.; Eiriksdottir, Gudny; Segers, Patrick; Vasan, Ramachandran S.; van Rijn, Marie Josee E.; Howard, Timothy D.; McArdle, Patrick F.; Dehghan, Abbas; Jewell, Elizabeth; Newhouse, Stephen J.; Bekaert, Sofie; Hamburg, Naomi M.; Newman, Anne B.; Hofman, Albert; Scuteri, Angelo; De Bacquer, Dirk; Ikram, Mohammad Arfan; Psaty, Bruce; Fuchsberger, Christian; Olden, Matthias; Wain, Louise V.; Elliott, Paul; Smith, Nicholas L.; Felix, Janine F.; Erdmann, Jeanette; Vita, Joseph A.; Sutton-Tyrrell, Kim; Sijbrands, Eric J.G.; Sanna, Serena; Launer, Lenore J.; De Meyer, Tim; Johnson, Andrew D.; Schut, Anna F.C.; Herrington, David M.; Rivadeneira, Fernando; Uda, Manuela; Wilkinson, Ian B.; Aspelund, Thor; Gillebert, Thierry C.; Van Bortel, Luc; Benjamin, Emelia J.; Oostra, Ben A.; Ding, Jingzhong; Gibson, Quince; Uitterlinden, André G.; Abecasis, Gonçalo R.; Cockcroft, John R.; Gudnason, Vilmundur; De Backer, Guy G.; Ferrucci, Luigi; Harris, Tamara B.; Shuldiner, Alan R.; van Duijn, Cornelia M.; Levy, Daniel; Lakatta, Edward G.; Witteman, Jacqueline C.M.

    2012-01-01

    Background Carotid-femoral pulse wave velocity (CFPWV) is a heritable measure of aortic stiffness that is strongly associated with increased risk for major cardiovascular disease events. Methods and Results We conducted a meta-analysis of genome-wide association data in 9 community-based European ancestry cohorts consisting of 20,634 participants. Results were replicated in 2 additional European ancestry cohorts involving 5,306 participants. Based on a preliminary analysis of 6 cohorts, we identified a locus on chromosome 14 in the 3′-BCL11B gene desert that is associated with CFPWV (rs7152623, minor allele frequency = 0.42, beta=−0.075±0.012 SD/allele, P = 2.8 x 10−10; replication beta=−0.086±0.020 SD/allele, P = 1.4 x 10−6). Combined results for rs7152623 from 11 cohorts gave beta=−0.076±0.010 SD/allele, P=3.1x10−15. The association persisted when adjusted for mean arterial pressure (beta=−0.060±0.009 SD/allele, P = 1.0 x 10−11). Results were consistent in younger (<55 years, 6 cohorts, N=13,914, beta=−0.081±0.014 SD/allele, P = 2.3 x 10−9) and older (9 cohorts, N=12,026, beta=−0.061±0.014 SD/allele, P=9.4x10−6) participants. In separate meta-analyses, the locus was associated with increased risk for coronary artery disease (hazard ratio [HR]=1.05, confidence interval [CI]=1.02 to 1.08, P=0.0013) and heart failure (HR=1.10, CI=1.03 to 1.16, P=0.004). Conclusions Common genetic variation in a locus in the BCL11B gene desert that is thought to harbor one or more gene enhancers is associated with higher CFPWV and increased risk for cardiovascular disease. Elucidation of the role this novel locus plays in aortic stiffness may facilitate development of therapeutic interventions that limit aortic stiffening and related cardiovascular disease events. PMID:22068335

  5. Laboratory model of the cardiovascular system for experimental demonstration of pulse wave propagation

    NASA Astrophysics Data System (ADS)

    Stojadinović, Bojana; Nestorović, Zorica; Djurić, Biljana; Tenne, Tamar; Zikich, Dragoslav; Žikić, Dejan

    2017-03-01

    The velocity by which a disturbance moves through the medium is the wave velocity. Pulse wave velocity is among the key parameters in hemodynamics. Investigation of wave propagation through the fluid-filled elastic tube has a great importance for the proper biophysical understanding of the nature of blood flow through the cardiovascular system. Here, we present a laboratory model of the cardiovascular system. We have designed an experimental setup which can help medical and nursing students to properly learn and understand basic fluid hemodynamic principles, pulse wave and the phenomenon of wave propagation in blood vessels. Demonstration of wave propagation allowed a real time observation of the formation of compression and expansion waves by students, thus enabling them to better understand the difference between the two waves, and also to measure the pulse wave velocity for different fluid viscosities. The laboratory model of the cardiovascular system could be useful as an active learning methodology and a complementary tool for understanding basic principles of hemodynamics.

  6. Early intervention of long-acting nifedipine GITS reduces brachial–ankle pulse wave velocity and improves arterial stiffness in Chinese patients with mild hypertension: a 24-week, single-arm, open-label, prospective study

    PubMed Central

    Zhang, Jidong; Wang, Yan; Hu, Haijuan; Yang, Xiaohong; Tian, Zejun; Liu, Demin; Gu, Guoqiang; Zheng, Hongmei; Xie, Ruiqin; Cui, Wei

    2016-01-01

    Background Nifedipine gastrointestinal therapeutic system (GITS) is used to treat angina and hypertension. The authors aimed to study the early intervention impact on arterial stiffness and pulse wave velocity (PWV) independent of its blood-pressure-(BP) lowering effect in mild hypertensive patients. Methods This single-center, single-arm, open-label, prospective, Phase IV study recruited patients with mild hypertension and increased PWV from December 2013 to December 2014 (N=138; age, 18–75 years; systolic blood pressure, 140–160 mmHg; diastolic BP, 90–100 mmHg; increased brachial–ankle pulse wave velocity [baPWV, ≥12 m/s]). Nifedipine GITS (30 mg/d) was administered for 24 weeks to achieve target BP of <140/90 mmHg. The dose was uptitrated at 60 mg/d in case of unsatisfactory BP reduction after 4 weeks. Primary study end point was the change in baPWV after nifedipine GITS treatment. Hemodynamic parameters (office BP, 24-hour ambulatory BP monitoring, and heart rate and adverse events) were evaluated at baseline and followed-up at 2, 4, 8, 12, 18, and 24 weeks. Results Majority of patients (n=117; 84.8%) completed the study. baPWV decreased significantly at 4 weeks compared with baseline (1,598.87±239.82 vs 1,500.89±241.15 cm/s, P<0.001), was stable at 12 weeks (1,482.24±215.14 cm/s, P<0.001), and remained steady through 24 weeks (1,472.58±205.01 cm/s, P<0.001). Office BP reduced from baseline to week 4 (154/95 vs 136/85 mmHg) and remained steady until 24 weeks. Nifedipine GITS significantly decreased 24-hour ambulatory BP monitoring (P<0.001) after 24 weeks from baseline. Mean arterial pressure and pulse pressure were lowered significantly after 4, 12, and 24 weeks of treatment (P<0.001). These changes in baPWV were significantly correlated with changes in systolic blood pressure, diastolic BP, and mean arterial pressure (P<0.05), but not with changes in pulse pressure (P>0.05). There were no other drug-related serious adverse events. Conclusion

  7. Pulse wave propagation in a model human arterial network: Assessment of 1-D visco-elastic simulations against in vitro measurements

    PubMed Central

    Alastruey, Jordi; Khir, Ashraf W.; Matthys, Koen S.; Segers, Patrick; Sherwin, Spencer J.; Verdonck, Pascal R.; Parker, Kim H.; Peiró, Joaquim

    2011-01-01

    The accuracy of the nonlinear one-dimensional (1-D) equations of pressure and flow wave propagation in Voigt-type visco-elastic arteries was tested against measurements in a well-defined experimental 1:1 replica of the 37 largest conduit arteries in the human systemic circulation. The parameters required by the numerical algorithm were directly measured in the in vitro setup and no data fitting was involved. The inclusion of wall visco-elasticity in the numerical model reduced the underdamped high-frequency oscillations obtained using a purely elastic tube law, especially in peripheral vessels, which was previously reported in this paper [Matthys et al., 2007. Pulse wave propagation in a model human arterial network: Assessment of 1-D numerical simulations against in vitro measurements. J. Biomech. 40, 3476–3486]. In comparison to the purely elastic model, visco-elasticity significantly reduced the average relative root-mean-square errors between numerical and experimental waveforms over the 70 locations measured in the in vitro model: from 3.0% to 2.5% (p<0.012) for pressure and from 15.7% to 10.8% (p<0.002) for the flow rate. In the frequency domain, average relative errors between numerical and experimental amplitudes from the 5th to the 20th harmonic decreased from 0.7% to 0.5% (p<0.107) for pressure and from 7.0% to 3.3% (p<10−6) for the flow rate. These results provide additional support for the use of 1-D reduced modelling to accurately simulate clinically relevant problems at a reasonable computational cost. PMID:21724188

  8. High resolution wavenumber analysis for investigation of arterial pulse wave propagation

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hideyuki; Sato, Masakazu; Irie, Takasuke

    2016-07-01

    The propagation of the pulse wave along the artery is relatively fast (several m/s), and a high-temporal resolution is required to measure pulse wave velocity (PWV) in a regional segment of the artery. High-frame-rate ultrasound enables the measurement of the regional PWV. In analyses of wave propagation phenomena, the direction and propagation speed are generally identified in the frequency-wavenumber space using the two-dimensional Fourier transform. However, the wavelength of the pulse wave is very long (1 m at a propagation velocity of 10 m/s and a temporal frequency of 10 Hz) compared with a typical lateral field of view of 40 mm in ultrasound imaging. Therefore, PWV cannot be identified in the frequency-wavenumber space owing to the low resolution of the two-dimensional Fourier transform. In the present study, PWV was visualized in the wavenumber domain using phases of arterial wall acceleration waveforms measured by high-frame-rate ultrasound.

  9. Investigation on the generation characteristic of pressure pulse wave signal during the measurement-while-drilling process

    NASA Astrophysics Data System (ADS)

    Changqing, Zhao; Kai, Liu; Tong, Zhao; Takei, Masahiro; Weian, Ren

    2014-04-01

    The mud-pulse logging instrument is an advanced measurement-while-drilling (MWD) tool and widely used by the industry in the world. In order to improve the signal transmission rate, ensure the accurate transmission of information and address the issue of the weak signal on the ground of oil and gas wells, the signal generator should send out the strong mud-pulse signals with the maximum amplitude. With the rotary valve pulse generator as the study object, the three-dimensional Reynolds NS equations and standard k - ɛ turbulent model were used as a mathematical model. The speed and pressure coupling calculation was done by simple algorithms to get the amplitudes of different rates of flow and axial clearances. Tests were done to verify the characteristics of the pressure signals. The pressure signal was captured by the standpiece pressure monitoring system. The study showed that the axial clearances grew bigger as the pressure wave amplitude value decreased and caused the weakening of the pulse signal. As the rate of flow got larger, the pressure wave amplitude would increase and the signal would be enhanced.

  10. High aortic pulse-wave velocity may be responsible for elevated red blood cell distribution width in overweight and obese people: a community-based, cross-sectional study

    PubMed Central

    Altiparmak, Ibrahim Halil; Erkus, Muslihittin Emre; Gunebakmaz, Ozgur; Yusuf, Sezen; Zekeriya, Kaya; Demirbag, Recep; Kocarslan, Aydemir; Sezen, Hatice; Yildiz, Ali

    2016-01-01

    Summary Background: Obesity and overweight are risk factors for atherosclerosis. Red blood cell distribution width (RDW) is associated with subclinical cardiac diseases. The aim of this study was to investigate the association between RDW and aortic stiffness in overweight or obese subjects. Methods: A total of 101 overweight or obese subjects without overt cardiovascular disorders, and 48 healthy controls were enrolled. RDW, aortic pulse-wave velocity (PWV) and augmentation index 75 (Aix75) were evaluated. The case subjects were divided into two sub-groups according to PWV values; ≥ 10 m/s in group I, and < 10 m/s in group II. Bivariate correlation and multiple regression analyses (stepwise) were performed. Results RDW and PWV were considerably increased in the case groups compared with the controls. RDW was significantly increased in group I compared with group II and the controls [median 12.0 m/s, interquartile range (IQR): 10.5–17.5; median 11.7 m/s, IQR: 10.2–14.2, and median 11.4 m/s, IQR: 9.6–15.5, p < 0.05, respectively]. Resting heart rate and age were higher in group I than group II (81 ± 11 vs 74 ± 12 beats/min and 41 ± 120 vs 36 ± 9 years, respectively, p < 0.05). Regression analyses revealed that while log-RDW, age and resting heart rate were independent predictors for aortic PWV, log-RDW was the most important predictor in the final model. Conclusions: RDW, resting heart rate and age independently predicted arterial stiffness, and RDW may be useful to provide an early recognition of subclinical atherosclerosis in overweight and obese individuals. PMID:26895298

  11. Pulse Wave Well Development Demonstration

    SciTech Connect

    Burdick, S.

    2001-02-23

    Conventional methods of well development at the Savannah River Site generate significant volumes of investigative derived waste (IDW) which must be treated and disposed of at a regulated Treatment, Storage, or Disposal (TSD) facility. Pulse Wave technology is a commercial method of well development utilizing bursts of high pressure gas to create strong pressure waves through the well screen zone, extending out into the formation surrounding the well. The patented process is intended to reduce well development time and the amount of IDW generated as well as to micro-fracture the formation to improve well capacity.

  12. Particle Velocity Measuring System

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey (Inventor); Carl, James R. (Inventor)

    1998-01-01

    Method and apparatus are provided for determining the velocity of individual food particles within a liquid/solid food mixture that is cooked by an aseptic cooking method whereby the food mixture is heated as it flows through a flowline. At least one upstream and at least one downstream microwave transducer are provided to determine the minimum possible travel time of the fastest food particle through the flowline. In one embodiment, the upstream detector is not required. In another embodiment, a plurality of small dipole antenna markers are secured to a plurality of food particles to provide a plurality of signals as the markers pass the upstream and downstream transducers. The dipole antenna markers may also include a non-linear element to reradiate a harmonic frequency of a transmitter frequency. Upstream and downstream transducers include dipole antennas that are matched to the impedance of the food slurry and a signal transmission cable by various impedance matching means including unbalanced feed to the antennas.

  13. The pioneer in hemodynamics and pulse-wave analysis, Otto Frank.

    PubMed

    Middeke, Martin

    2016-04-01

    Arterial pulse-wave velocity is a noninvasive index of arterial distensibility now generally advocated to assess cardiovascular health above-and-beyond merely measuring blood pressure. A host of recent findings supports its use. This evidence draws attention to the fact that vascular stiffness precedes the increase in blood pressure with age and that even nonpharmacological lifestyle interventions can improve distensibility independent of blood pressure. Where do these ingeniously modern ideas come from, and who defined the principles we embrace today? A worthwhile lesson in physiology and exercise in humility is the effort to revisit the origins of these concepts and the man to whom gratitude should be directed.

  14. Measurement of retinal blood velocity

    NASA Astrophysics Data System (ADS)

    Winchester, Leonard W., Jr.; Chou, Nee-Yin

    2006-02-01

    A fundus camera was modified to illuminate the retina of a rabbit model with low power laser light in order to obtain laser speckle images. A fast-exposure charge-coupled device (CCD) camera was used to capture laser speckle images of the retina. Image acquisition was synchronized with the arterial pulses of the rabbit to ensure that all images are obtained at the same point in the cardiac cycle. The rabbits were sedated and a speculum was inserted to prevent the eyelid from closing. Both albino (New Zealand; pigmented (Dutch belted) rabbits were used in the study. The rabbit retina is almost avascular. The measurements are obtained for choroidal tissue as well as retinal tissue. Because the retina is in a region of high metabolism, blood velocity is strongly affected by blood oxygen saturation. Measurements of blood velocity obtained over a wide range of O II saturations (58%-100%) showed that blood velocity increases with decreasing O II saturation. For most experiments, the left eye of the rabbit was used for laser measurements whereas the right eye served as a control. No observable difference between pre- and post-experimented eye was noted. Histological examinations of retinal tissue subjected to repeated laser measurements showed no indication of tissue damage.

  15. Tangential Velocity Measurement Using Interferometric MTI Radar

    SciTech Connect

    DOERRY, ARMIN W.; MILESHOSKY, BRIAN P.; BICKEL, DOUGLAS L.

    2002-11-01

    An Interferometric Moving Target Indicator radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity vector of a target.

  16. Measuring mean velocities with Pogo

    SciTech Connect

    Rossby, T.; Fontaine, J.; Hummon, J. )

    1991-10-01

    Pogo is a sample technique for measuring water transport between the surface and some preselected depth. Equipped with a 12-kHz pinger for tracking and range measurements, a xenon flasher for nighttime relocation, and a VHF beacon for daytime recovery, it has been used over 200 times in the Gulf Stream to measure volume transport and to provide a reference velocity (transport) for geostrophic calculations from pairs of hydrographic stations. This note gives a brief technical description of Pogo and how it is used. Loran C was used for navigation in this study, but with the advent of the Global Positioning System (GPS), Pogo can be used worldwide. 6 refs.

  17. Pulse wave imaging using coherent compounding in a phantom and in vivo.

    PubMed

    Apostolakis, Iason Zacharias; McGarry, Matthew D J; Bunting, Ethan A; Konofagou, Elisa E

    2017-03-07

    Pulse wave velocity (PWV) is a surrogate marker of arterial stiffness linked to cardiovascular morbidity. Pulse wave imaging (PWI) is a technique developed by our group for imaging the pulse wave propagation in vivo. PWI requires high temporal and spatial resolution, which conventional ultrasonic imaging is unable to simultaneously provide. Coherent compounding is known to address this tradeoff and provides full aperture images at high frame rates. This study aims to implement PWI using coherent compounding within a GPU-accelerated framework. The results of the implemented method were validated using a silicone phantom against static mechanical testing. Reproducibility of the measured PWVs was assessed in the right common carotid of six healthy subjects (n  =  6) approximately 10-15 mm before the bifurcation during two cardiac cycles over the course of 1-3 d. Good agreement of the measured PWVs (3.97  ±  1.21 m s(-1), 4.08  ±  1.15 m s(-1), p  =  0.74) was obtained. The effects of frame rate, transmission angle and number of compounded plane waves on PWI performance were investigated in the six healthy volunteers. Performance metrics such as the reproducibility of the PWVs, the coefficient of determination (r (2)), the SNR of the PWI axial wall velocities ([Formula: see text]) and the percentage of lateral positions where the pulse wave appears to arrive at the same time-point, indicating inadequacy of the temporal resolution (i.e. temporal resolution misses) were used to evaluate the effect of each parameter. Compounding plane waves transmitted at 1° increments with a linear array yielded optimal performance, generating significantly higher r (2) and [Formula: see text] values (p  ⩽  0.05). Higher frame rates (⩾1667 Hz) produced improvements with significant gains in the r (2) coefficient (p  ⩽  0.05) and significant increase in both r (2) and [Formula: see text] from single plane wave imaging to 3-plane

  18. Pulse wave imaging using coherent compounding in a phantom and in vivo

    NASA Astrophysics Data System (ADS)

    Zacharias Apostolakis, Iason; McGarry, Matthew D. J.; Bunting, Ethan A.; Konofagou, Elisa E.

    2017-03-01

    Pulse wave velocity (PWV) is a surrogate marker of arterial stiffness linked to cardiovascular morbidity. Pulse wave imaging (PWI) is a technique developed by our group for imaging the pulse wave propagation in vivo. PWI requires high temporal and spatial resolution, which conventional ultrasonic imaging is unable to simultaneously provide. Coherent compounding is known to address this tradeoff and provides full aperture images at high frame rates. This study aims to implement PWI using coherent compounding within a GPU-accelerated framework. The results of the implemented method were validated using a silicone phantom against static mechanical testing. Reproducibility of the measured PWVs was assessed in the right common carotid of six healthy subjects (n  =  6) approximately 10–15 mm before the bifurcation during two cardiac cycles over the course of 1–3 d. Good agreement of the measured PWVs (3.97  ±  1.21 m s‑1, 4.08  ±  1.15 m s‑1, p  =  0.74) was obtained. The effects of frame rate, transmission angle and number of compounded plane waves on PWI performance were investigated in the six healthy volunteers. Performance metrics such as the reproducibility of the PWVs, the coefficient of determination (r 2), the SNR of the PWI axial wall velocities (\\text{SN}{{\\text{R}}{{\\text{v}_{\\text{PWI}}}}} ) and the percentage of lateral positions where the pulse wave appears to arrive at the same time-point, indicating inadequacy of the temporal resolution (i.e. temporal resolution misses) were used to evaluate the effect of each parameter. Compounding plane waves transmitted at 1° increments with a linear array yielded optimal performance, generating significantly higher r 2 and \\text{SN}{{\\text{R}}{{\\text{v}_{\\text{PWI}}}}} values (p  ⩽  0.05). Higher frame rates (⩾1667 Hz) produced improvements with significant gains in the r 2 coefficient (p  ⩽  0.05) and significant increase in both r 2 and

  19. Pulse Wave Variation during the Menstrual Cycle in Women with Menstrual Pain

    PubMed Central

    Jeon, Soo Hyung; Kim, Kyu Kon; Lee, In Seon; Lee, Yong Tae; Kim, Gyeong Cheol; Chi, Gyoo Yong; Cho, Hye Sook; Kang, Hee Jung

    2016-01-01

    Objective. This study is performed to obtain objective diagnostic indicators associated with menstrual pain using pulse wave analysis. Methods. Using a pulse diagnostic device, we measured the pulse waves of 541 women aged between 19 and 30 years, placed in either an experimental group with menstrual pain (n = 329) or a control group with little or no menstrual pain (n = 212). Measurements were taken during both the menstrual and nonmenstrual periods, and comparative analysis was performed. Results. During the nonmenstrual period, the experimental group showed a significantly higher value in the left radial artery for the radial augmentation index (RAI) (p = 0.050) but significantly lower values for pulse wave energy (p = 0.021) and time to first peak from baseline (T1) (p = 0.035) in the right radial artery. During the menstrual period, the experimental group showed significantly lower values in the left radial artery for cardiac diastole and pulse wave area during diastole and significantly higher values for pulse wave area during systole, ratio of systolic phase to the full heartbeat, and systolic-diastolic ratio. Conclusion. We obtained indicators of menstrual pain in women during the menstrual period, including prolonged systolic and shortened diastolic phases, increases in pulse wave energy and area of representative pulse wave, and increased blood vessel resistance. PMID:27579304

  20. Engineering studies of vectorcardiographs in blood pressure measuring systems, appendix 2

    NASA Technical Reports Server (NTRS)

    Mark, R. G.

    1975-01-01

    The development of a cardiovascular monitoring system to noninvasively monitor the blood pressure and heart rate using pulse wave velocity was described. The following topics were covered: (1) pulse wave velocity as a measure of arterial blood pressure, (2) diastolic blood pressure and pulse wave velocity in humans, (3) transducer development for blood pressure measuring device, and (4) cardiovascular monitoring system. It was found, in experiments on dogs, that the pulse wave velocity is linearly related to diastolic blood pressure over a wide range of blood pressure and in the presence of many physiological perturbations. A similar relationship was observed in normal, young human males over a moderate range of pressures. Past methods for monitoring blood pressure and a new method based on pulse wave velocity determination were described. Two systems were tested: a Doppler ultrasonic transducer and a photoelectric plethysmograph. A cardiovascular monitoring system was described, including operating instructions.

  1. Alterations in pulse wave propagation reflect the degree of outflow tract banding in HH18 chicken embryos

    PubMed Central

    Shi, Liang; Goenezen, Sevan; Haller, Stephen; Hinds, Monica T.; Thornburg, Kent L.

    2013-01-01

    Hemodynamic conditions play a critical role in embryonic cardiovascular development, and altered blood flow leads to congenital heart defects. Chicken embryos are frequently used as models of cardiac development, with abnormal blood flow achieved through surgical interventions such as outflow tract (OFT) banding, in which a suture is tightened around the heart OFT to restrict blood flow. Banding in embryos increases blood pressure and alters blood flow dynamics, leading to cardiac malformations similar to those seen in human congenital heart disease. In studying these hemodynamic changes, synchronization of data to the cardiac cycle is challenging, and alterations in the timing of cardiovascular events after interventions are frequently lost. To overcome this difficulty, we used ECG signals from chicken embryos (Hamburger-Hamilton stage 18, ∼3 days of incubation) to synchronize blood pressure measurements and optical coherence tomography images. Our results revealed that, after 2 h of banding, blood pressure and pulse wave propagation strongly depend on band tightness. In particular, while pulse transit time in the heart OFT of control embryos is ∼10% of the cardiac cycle, after banding (35% to 50% band tightness) it becomes negligible, indicating a faster OFT pulse wave velocity. Pulse wave propagation in the circulation is likewise affected; however, pulse transit time between the ventricle and dorsal aorta (at the level of the heart) is unchanged, suggesting an overall preservation of cardiovascular function. Changes in cardiac pressure wave propagation are likely contributing to the extent of cardiac malformations observed in banded hearts. PMID:23709601

  2. Hydrokinetic canal measurements: inflow velocity, wake flow velocity, and turbulence

    SciTech Connect

    Gunawan, Budi

    2014-06-11

    The dataset consist of acoustic Doppler current profiler (ADCP) velocity measurements in the wake of a 3-meter diameter vertical-axis hydrokinetic turbine deployed in Roza Canal, Yakima, WA, USA. A normalized hub-centerline wake velocity profile and two cross-section velocity contours, 10 meters and 20 meters downstream of the turbine, are presented. Mean velocities and turbulence data, measured using acoustic Doppler velocimeter (ADV) at 50 meters upstream of the turbine, are also presented. Canal dimensions and hydraulic properties, and turbine-related information are also included.

  3. Inexpensive Time-of-Flight Velocity Measurements.

    ERIC Educational Resources Information Center

    Everett, Glen E.; Wild, R. L.

    1979-01-01

    Describes a circuit designed to measure time-of-flight velocity and shows how to use it to determine bullet velocity in connection with the ballistic pendulum demonstration of momentum conservation. (Author/GA)

  4. Tangential velocity measurement using interferometric MTI radar

    SciTech Connect

    Doerry, Armin W.; Mileshosky, Brian P.; Bickel, Douglas L.

    2006-01-03

    Radar systems use time delay measurements between a transmitted signal and its echo to calculate range to a target. Ranges that change with time cause a Doppler offset in phase and frequency of the echo. Consequently, the closing velocity between target and radar can be measured by measuring the Doppler offset of the echo. The closing velocity is also known as radial velocity, or line-of-sight velocity. Doppler frequency is measured in a pulse-Doppler radar as a linear phase shift over a set of radar pulses during some Coherent Processing Interval (CPI). An Interferometric Moving Target Indicator (MTI) radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity of a target.

  5. Three-dimensional velocity measurements using LDA

    NASA Astrophysics Data System (ADS)

    Buchhave, Preben

    The design requirements for and development of an LDA that measures the three components of the fluid velocity vector are described. The problems encountered in LDA measurements in highly turbulent flows, multivariate response, velocity bias, spatial resolution, temporal resolution, and dynamic range, are discussed. The use of the fringe and/or the reference beam methods to measure the three velocity components, and the use of color, frequency shift, and polarization to separate three velocity projections are examined. Consideration is given to the coordinate transformation, the presentation of three-dimensional LDA data, and the possibility of three-dimensional bias correction. Procedures for conducting three-dimensional LDA measurements are proposed.

  6. Pulsed-wave Doppler ultrasonographic evaluation of hepatic vein in dogs with tricuspid regurgitation

    PubMed Central

    Kim, Jaehwan; Kim, Soyoung

    2017-01-01

    This study was performed to identify the relationships between hepatic vein (HV) measurements, including flow velocity and waveform, using pulsed-wave (PW) Doppler ultrasonography, and the severity of tricuspid regurgitation (TR) in dogs. The study included 22 dogs with TR and 7 healthy dogs. The TR group was subdivided into 3 groups according to TR jet profile obtained by echocardiography. The hepatic venous waveform was obtained and classified into 3 types. A variety of HV measurements, including the maximal velocities of the atrial systolic, systolic (S), end ventricular systolic, and diastolic (D) waves and the ratio of the S- and D- wave velocities (S/D ratio), were acquired. TR severity was significantly correlated with the S- (r = −0.380, p = 0.042) and D- (r = 0.468, p = 0.011) wave velocities and the S/D ratio (r = −0.747, p < 0.001). Receiver operating characteristic curve analysis revealed the highest sensitivity and specificity for the S/D ratio (89% and 75%, respectively) at a threshold of 0.97 with excellent accuracy (AUC = 0.911, p < 0.001). In conclusion, PW Doppler ultrasonography of the HV can be used to identify the presence of significant TR and to classify TR severity in dogs. PMID:27515264

  7. Modeling measured glottal volume velocity waveforms.

    PubMed

    Verneuil, Andrew; Berry, David A; Kreiman, Jody; Gerratt, Bruce R; Ye, Ming; Berke, Gerald S

    2003-02-01

    The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use.

  8. Achromatic Emission Velocity Measurements in Luminous Flows

    NASA Technical Reports Server (NTRS)

    Schneider, S. J.; Fulghum, S. F.; Rostler, P. S.

    1997-01-01

    A new velocity measurement instrument for luminous flows was developed by Science Research Laboratory for NASA. The SIEVE (Segmented Image Emission VElocimeter) instrument uses broadband light emitted by the flow for the velocity measurement. This differs from other velocimetry techniques in that it does not depend on laser illumination and/or light scattering from particles in the flow. The SIEVE is a passive, non-intrusive diagnostic. By moving and adjusting the imaging optics, the SIEVE can provide three-dimensional mapping of a flow field and determine turbulence scale size. A SIEVE instrument was demonstrated on an illuminated rotating disk to evaluate instrument response and noise and on an oxy-acetylene torch to measure flame velocities. The luminous flow in rocket combustors and plumes is an ideal subject for the SIEVE velocity measurement technique.

  9. Spall velocity measurements from laboratory impact craters

    NASA Technical Reports Server (NTRS)

    Polanskey, Carol A.; Ahrens, Thomas J.

    1986-01-01

    Spall velocities were measured for a series of impacts into San Marcos gabbro. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles varied in material and size with a maximum mass of 4g for a lead bullet to a minimum of 0.04 g for an aluminum sphere. The spall velocities were calculated both from measurements taken from films of the events and from estimates based on range measurements of the spall fragments. The maximum spall velocity observed was 27 m/sec, or 0.5 percent of the impact velocity. The measured spall velocities were within the range predicted by the Melosh (1984) spallation model for the given experimental parameters. The compatability between the Melosh model for large planetary impacts and the results of these small scale experiments is considered in detail. The targets were also bisected to observe the internal fractures. A series of fractures were observed whose location coincided with the boundary of the theoretical near surface zone predicted by Melosh. Above this boundary the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.

  10. Spall velocity measurements from laboratory impact craters

    NASA Astrophysics Data System (ADS)

    Polanskey, Carol A.; Ahrens, Thomas J.

    Spall velocities were measured for a series of impacts into San Marcos gabbro. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles varied in material and size with a maximum mass of 4g for a lead bullet to a minimum of 0.04 g for an aluminum sphere. The spall velocities were calculated both from measurements taken from films of the events and from estimates based on range measurements of the spall fragments. The maximum spall velocity observed was 27 m/sec, or 0.5 percent of the impact velocity. The measured spall velocities were within the range predicted by the Melosh (1984) spallation model for the given experimental parameters. The compatability between the Melosh model for large planetary impacts and the results of these small scale experiments is considered in detail. The targets were also bisected to observe the internal fractures. A series of fractures were observed whose location coincided with the boundary of the theoretical near surface zone predicted by Melosh. Above this boundary the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.

  11. Internal Detonation Velocity Measurements Inside High Explosives

    SciTech Connect

    Benterou, J; Bennett, C V; Cole, G; Hare, D E; May, C; Udd, E

    2009-01-16

    In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation models and detonation models of high explosives, the ability to continuously measure the detonation velocity within an explosive is required. Progress on an embedded velocity diagnostic using a 125 micron diameter optical fiber containing a chirped fiber Bragg grating is reported. As the chirped fiber Bragg grating is consumed by the moving detonation wave, the physical length of the unconsumed Bragg grating is monitored with a fast InGaAs photodiode. Experimental details of the associated equipment and data in the form of continuous detonation velocity records within PBX-9502 are presented. This small diameter fiber sensor has the potential to measure internal detonation velocities on the order of 10 mm/{micro}sec along path lengths tens of millimeters long.

  12. Measurement of the velocity of a quantum object: a role of group velocity

    NASA Astrophysics Data System (ADS)

    Rostovtsev, Yuri V.

    2013-03-01

    We consider a free motion of a quantum particle. Introducing an explicit measurement procedure for velocity, we demonstrate that the measured velocity is related to the group and phase velocities of the corresponding matter waves. We show that for long distances the measured velocity coincides with the matter wave group velocity.

  13. Antarctica: measuring glacier velocity from satellite images

    SciTech Connect

    Lucchitta, B.K.; Ferguson, H.M.

    1986-11-28

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  14. Velocity and turbulence measurements in combustion systems

    NASA Astrophysics Data System (ADS)

    Goldstein, R. J.; Lau, K. Y.; Leung, C. C.

    1983-06-01

    A laser-Doppler velocimeter is used in the measurement of high-temperature gas flows. A two-stage fluidization particle generator provides magnesium oxide particles to serve as optical scattering centers. The one-dimensional dual-beam system is frequency shifted to permit measurements of velocities up to 300 meters per second and turbulence intensities greater than 100 percent. Exiting flows from can-type gas turbine combustors and burners with pre-mixed oxy-acetylene flames are described in terms of the velocity, turbulence intensity, and temperature profiles. The results indicate the influence of the combustion process on turbulence.

  15. Wave measurements using GPS velocity signals.

    PubMed

    Doong, Dong-Jiing; Lee, Beng-Chun; Kao, Chia Chuen

    2011-01-01

    This study presents the idea of using GPS-output velocity signals to obtain wave measurement data. The application of the transformation from a velocity spectrum to a displacement spectrum in conjunction with the directional wave spectral theory are the core concepts in this study. Laboratory experiments were conducted to verify the accuracy of the inversed displacement of the surface of the sea. A GPS device was installed on a moored accelerometer buoy to verify the GPS-derived wave parameters. It was determined that loss or drifting of the GPS signal, as well as energy spikes occurring in the low frequency band led to erroneous measurements. Through the application of moving average skill and a process of frequency cut-off to the GPS output velocity, correlations between GPS-derived, and accelerometer buoy-measured significant wave heights and periods were both improved to 0.95. The GPS-derived one-dimensional and directional wave spectra were in agreement with the measurements. Despite the direction verification showing a 10° bias, this exercise still provided useful information with sufficient accuracy for a number of specific purposes. The results presented in this study indicate that using GPS output velocity is a reasonable alternative for the measurement of ocean waves.

  16. 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…

  17. Optoelectronic System for Measuring Warhead Fragments Velocity

    NASA Astrophysics Data System (ADS)

    Liu, Ji; Zhao, Donge; Li, Yangjun; Zhou, Hanchang

    2011-02-01

    High-speed warhead fragments velocity measurement is one of the key technologies in investigating damage efficiency of warhead. We have designed and constructed a system to accurately determine the velocity of warhead fragments by measuring the time of flight between two parallel laser screens is presented. Each screen is formed by a laser source, a large photodetector and a retro-reflector. Optical output of the laser source is a collimated beam. The beam passes through cylindrical lens and the slit of photodetector reach to retro-reflector .The energy, reflected by retro-reflector; focus on the active area of photodetector. The system utilizes reflected ray by scotchlite retro-reflector as the start and end signal. And utilizes wideband circuit and data acquiring system to condition and sample signals. Experimental results show the system can measurement velocity are within the range from 20m/s to 2000m/s on target area of 1m2 and can perform satisfactorily with a wide range from 2000 lx to100,000lx. The measurement system also can be used to test velocity of projectile.

  18. Algal Cell Response to Pulsed Waved Stimulation and Its Application to Increase Algal Lipid Production

    PubMed Central

    Savchenko, Oleksandra; Xing, Jida; Yang, Xiaoyan; Gu, Quanrong; Shaheen, Mohamed; Huang, Min; Yu, Xiaojian; Burrell, Robert; Patra, Prabir; Chen, Jie

    2017-01-01

    Generating renewable energy while sequestering CO2 using algae has recently attracted significant research attention, mostly directing towards biological methods such as systems biology, genetic engineering and bio-refining for optimizing algae strains. Other approaches focus on chemical screening to adjust culture conditions or culture media. We report for the first time the physiological changes of algal cells in response to a novel form of mechanical stimulation, or a pulsed wave at the frequency of 1.5 MHz and the duty cycle of 20%. We studied how the pulsed wave can further increase algal lipid production on top of existing biological and chemical methods. Two commonly used algal strains, fresh-water Chlorella vulgaris and seawater Tetraselmis chuii, were selected. We have performed the tests in shake flasks and 1 L spinner-flask bioreactors. Conventional Gravimetric measurements show that up to 20% increase for algal lipid could be achieved after 8 days of stimulation. The total electricity cost needed for the stimulations in a one-liter bioreactor is only one-tenth of a US penny. Gas liquid chromatography shows that the fatty acid composition remains unchanged after pulsed-wave stimulation. Scanning electron microscope results also suggest that pulsed wave stimulation induces shear stress and thus increases algal lipid production. PMID:28186124

  19. Algal Cell Response to Pulsed Waved Stimulation and Its Application to Increase Algal Lipid Production

    NASA Astrophysics Data System (ADS)

    Savchenko, Oleksandra; Xing, Jida; Yang, Xiaoyan; Gu, Quanrong; Shaheen, Mohamed; Huang, Min; Yu, Xiaojian; Burrell, Robert; Patra, Prabir; Chen, Jie

    2017-02-01

    Generating renewable energy while sequestering CO2 using algae has recently attracted significant research attention, mostly directing towards biological methods such as systems biology, genetic engineering and bio-refining for optimizing algae strains. Other approaches focus on chemical screening to adjust culture conditions or culture media. We report for the first time the physiological changes of algal cells in response to a novel form of mechanical stimulation, or a pulsed wave at the frequency of 1.5 MHz and the duty cycle of 20%. We studied how the pulsed wave can further increase algal lipid production on top of existing biological and chemical methods. Two commonly used algal strains, fresh-water Chlorella vulgaris and seawater Tetraselmis chuii, were selected. We have performed the tests in shake flasks and 1 L spinner-flask bioreactors. Conventional Gravimetric measurements show that up to 20% increase for algal lipid could be achieved after 8 days of stimulation. The total electricity cost needed for the stimulations in a one-liter bioreactor is only one-tenth of a US penny. Gas liquid chromatography shows that the fatty acid composition remains unchanged after pulsed-wave stimulation. Scanning electron microscope results also suggest that pulsed wave stimulation induces shear stress and thus increases algal lipid production.

  20. Algal Cell Response to Pulsed Waved Stimulation and Its Application to Increase Algal Lipid Production.

    PubMed

    Savchenko, Oleksandra; Xing, Jida; Yang, Xiaoyan; Gu, Quanrong; Shaheen, Mohamed; Huang, Min; Yu, Xiaojian; Burrell, Robert; Patra, Prabir; Chen, Jie

    2017-02-10

    Generating renewable energy while sequestering CO2 using algae has recently attracted significant research attention, mostly directing towards biological methods such as systems biology, genetic engineering and bio-refining for optimizing algae strains. Other approaches focus on chemical screening to adjust culture conditions or culture media. We report for the first time the physiological changes of algal cells in response to a novel form of mechanical stimulation, or a pulsed wave at the frequency of 1.5 MHz and the duty cycle of 20%. We studied how the pulsed wave can further increase algal lipid production on top of existing biological and chemical methods. Two commonly used algal strains, fresh-water Chlorella vulgaris and seawater Tetraselmis chuii, were selected. We have performed the tests in shake flasks and 1 L spinner-flask bioreactors. Conventional Gravimetric measurements show that up to 20% increase for algal lipid could be achieved after 8 days of stimulation. The total electricity cost needed for the stimulations in a one-liter bioreactor is only one-tenth of a US penny. Gas liquid chromatography shows that the fatty acid composition remains unchanged after pulsed-wave stimulation. Scanning electron microscope results also suggest that pulsed wave stimulation induces shear stress and thus increases algal lipid production.

  1. Shear wave velocity measurements in marine sediments

    NASA Astrophysics Data System (ADS)

    Matthews, J. E.

    1982-09-01

    Pulsed ultrasonic techniques for the measurement of sound speed are reliable and well documented. Extension of these techniques to the measurement of shear wave velocities in marine sediments, generally was unsuccessful. Recently developed shear wave transducers, based upon piezoelectric benders operated at sonic frequencies, provide significantly improved transducer-sample mechanical coupling. This improved coupling allows the application of pulsed techniques to the measurement of shear wave velocities in marine sediments, and the rapid determination of sediment dynamic elastic properties. Two types of bender-based shear wave transducer and preliminary data are described: 1) a probe configuration for box core samples, and 2) a modification to the Hamilton Frame Velocimeter for cut samples.

  2. Dust Particle Velocity Measurement in Shock Tubes.

    DTIC Science & Technology

    1985-12-08

    00. . .. 0 . 37 21 Photography of Electronic System for CERF 6’ Shock Tubeo..o..... 38 22 Record of a Typical Doppler Burst...2.1 PRINCIPLE OF OPERATION. Direct measurement of the particle velocity was obtained using Laser Doppler Velocimetry (LDV) [Ref. 2 and 3]. The...and transforms it into an electri- cal signal, known as Doppler burst. The period of the burst (T) is a function of the fringe spacing and the

  3. Measurement of neutrino masses from relative velocities.

    PubMed

    Zhu, Hong-Ming; Pen, Ue-Li; Chen, Xuelei; Inman, Derek; Yu, Yu

    2014-09-26

    We present a new technique to measure neutrino masses using their flow field relative to dark matter. Present day streaming motions of neutrinos relative to dark matter and baryons are several hundred km/s, comparable with their thermal velocity dispersion. This results in a unique dipole anisotropic distortion of the matter-neutrino cross power spectrum, which is observable through the dipole distortion in the cross correlation of different galaxy populations. Such a dipole vanishes if not for this relative velocity and so it is a clean signature for neutrino mass. We estimate the size of this effect and find that current and future galaxy surveys may be sensitive to these signature distortions.

  4. Relationship between radial and central arterial pulse wave and evaluation of central aortic pressure using the radial arterial pulse wave.

    PubMed

    Takazawa, Kenji; Kobayashi, Hideyuki; Shindo, Naohisa; Tanaka, Nobuhiro; Yamashina, Akira

    2007-03-01

    Since a decrease of central aortic pressure contributes to the prevention of cardiovascular events, simple measurement of not only brachial blood pressure but also central aortic pressure may be useful in the prevention and treatment of cardiovascular diseases. In this study, we simultaneously measured radial artery pulse waves non-invasively and ascending aortic pressure invasively, before and after the administration of nicorandil. We then compared changes in central aortic pressure and radial arterial blood pressure calibrated with brachial blood pressure in addition to calculating the augmentation index (AI) at the aorta and radial artery. After nicorandil administration, the reduction in maximal systolic blood pressure in the aorta (Deltaa-SBP) was -14+/-15 mmHg, significantly larger than that in early systolic pressure in the radial artery (Deltar-SBP) (-9+/-12 mmHg). The reduction in late systolic blood pressure in the radial artery (Deltar-SBP2) was -15+/-14 mmHg, significantly larger than Deltar-SBP, but not significantly different from Deltaa-SBP. There were significant relationships between Deltaa-SBP and Deltar-SBP (r=0.81, p<0.001), and between Deltaa-SBP and Deltar-SBP2 (r=0.91, p<0.001). The slope of the correlation regression line with Deltar-SBP2 (0.83) was larger and closer to 1 than that with Deltar-SBP (0.63), showing that the relationship was close to 1:1. Significant correlations were obtained between aortic AI (a-AI) and radial AI (r-AI) (before nicorandil administration: r=0.91, p<0.001; after administration: r=0.70, p<0.001). These data suggest that the measurement of radial artery pulse wave and observation of changes in the late systolic blood pressure in the radial artery (r-SBP2) in addition to the ordinary measurement of brachial blood pressure may enable a more accurate evaluation of changes in maximal systolic blood pressure in the aorta (a-SBP).

  5. Tomographic Particle Localization and Velocity Measurement

    NASA Astrophysics Data System (ADS)

    Kirner, S.; Forster, G.; Schein, J.

    2015-01-01

    Wire arc spraying is one of the most common and elementary thermal spray processes. Due to its easy handling, high deposition rate, and relative low process costs, it is a frequently used coating technology for the production of wear and corrosion resistant coatings. In order to produce reliable and reproducible coatings, it is necessary to be able to control the coating process. This can be achieved by analyzing the parameters of the particles deposited. Essential for the coating quality are, for example, the velocity, the size, and the temperature of the particles. In this work, an innovative diagnostic for particle velocity and location determination is presented. By the use of several synchronized CMOS-Cameras positioned around the particle jet, a series of images from different directions is simultaneously taken. The images contain the information that is necessary to calculate the 3D-location-vector of the particles and finally with the help of the exposure time the trajectory can be determined. In this work, the experimental setup of the tomographic diagnostic is presented, the mathematical method of the reconstruction is explained, and first measured velocity distributions are shown.

  6. Radionuclide counting technique for measuring wind velocity

    SciTech Connect

    Singh, J.J.; Khandelwal, G.S.

    1981-12-01

    A technique for measuring wind velocities of meteorological interest is described. It is based on inverse-square-law variation of the counting rates as the radioactive source-to-counter distance is changed by wind drag on the source ball. Results of a feasibility study using a weak bismuth 207 radiation source and three Geiger-Muller radiation counters are reported. The use of the technique is not restricted to Martian or Mars-like environments. A description of the apparatus, typical results, and frequency response characteristics are included. A discussion of a double-pendulum arrangement is presented. Measurements reported herein indicate that the proposed technique may be suitable for measuring wind speeds up to 100 m/sec, which are either steady or whose rates of fluctuation are less than 1 kHz.

  7. Pulse wave analysis for the prediction of preeclampsia.

    PubMed

    Carty, D M; Neisius, U; Rooney, L K; Dominiczak, A F; Delles, C

    2014-02-01

    Preeclampsia is associated with a number of changes to maternal vascular function. Assessment of arterial stiffness using pulse wave analysis (PWA) has been proposed as a means of predicting preeclampsia before the onset of clinically detectable disease. One hundred and eighty women with 2 risk factors for preeclampsia were examined at gestational weeks 16 and 28, of whom 17 (9.4%) developed preeclampsia. To study the effects of pregnancy itself women were also examined at 6-9 months post-natally; an additional 30 healthy non-pregnant women were also examined. PWA was performed using SphygmoCor; augmentation index (AIx), a marker of arterial wave reflection, was also measured using EndoPAT-2000. Women who developed preeclampsia were more likely to be overweight and had a higher brachial and central diastolic BP at gestational week 16 than those who remained normotensive. There was no difference in any parameter of arterial wave reflection between non-pregnant and pregnant women, nor between those who developed preeclampsia and those who remained normotensive, when examined at weeks 16 and 28 or post-natally. In this cohort of women with risk factors for preeclampsia, PWA did not provide additional information beyond brachial blood pressure and maternal risk factor profile about the risk of future development of preeclampsia.

  8. Velocity Gradient Maps Directly Measured by PLF

    NASA Astrophysics Data System (ADS)

    Quintella, Cristina M.; Gonçalves, Cristiane C.; Lima, Angelo Mv; Pepe, Iuri M.

    2000-11-01

    Flows are macroscopically classified as laminar or turbulent due to their velocity distributions, nevertheless most chemical and biological phenomena are yield or enhanced by intermolecular orientation and microscopic turbulence. Here was studied a 100micra liquid sheet produced by a slit nozzle, both flowing freely into air and over a borosilicate surface (roughness bellow 5nm), ranging from 17 to 36Re (143 to 297cm/s, similar to muscles and brain blood flow). Mono ethylene glycol was used either pure, or with sodium alkyl benzene sulfated (ABS) surfactant (24.5mol/L, submicellar), or with poly(ethylene oxide) (PEO) (1409ppm, 4millions aw). Velocity gradients were directly measured by 514nm polarized laser induced fluorescence (PLF) with R6G as probe. Intermolecular alignment (IA) maps were obtained all over the flow (about 1,950 points, 0.02mm2 precision). The free jet average IA has increased 57% when flowing over borosilicate. With ABS, the IA increased, suggesting wall drag reduction. With PEO the IA decreases due to solvent intermolecular forces attenuation, generating wider turbulent areas. PLF proved to be an excellent method to evaluate IA within liquid thin flows. Chosen solute additions permits IA control over wide regions.

  9. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  10. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  11. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  12. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  13. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

  14. Quantification of ultrasound correlation-based flow velocity mapping and edge velocity gradient measurement.

    PubMed

    Park, Dae Woo; Kruger, Grant H; Rubin, Jonathan M; Hamilton, James; Gottschalk, Paul; Dodde, Robert E; Shih, Albert J; Weitzel, William F

    2013-10-01

    This study investigated the use of ultrasound speckle decorrelation- and correlation-based lateral speckle-tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation-based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame-to-frame decorrelation. In this research, both decorrelation and lateral speckle-tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation-based lateral speckle-tracking method. The novelty of this study is that speckle decorrelation-based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decorrelation-based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.

  15. [A quick algorithm of dynamic spectrum photoelectric pulse wave detection based on LabVIEW].

    PubMed

    Lin, Ling; Li, Na; Li, Gang

    2010-02-01

    Dynamic spectrum (DS) detection is attractive among the numerous noninvasive blood component detection methods because of the elimination of the main interference of the individual discrepancy and measure conditions. DS is a kind of spectrum extracted from the photoelectric pulse wave and closely relative to the artery blood. It can be used in a noninvasive blood component concentration examination. The key issues in DS detection are high detection precision and high operation speed. The precision of measure can be advanced by making use of over-sampling and lock-in amplifying on the pick-up of photoelectric pulse wave in DS detection. In the present paper, the theory expression formula of the over-sampling and lock-in amplifying method was deduced firstly. Then in order to overcome the problems of great data and excessive operation brought on by this technology, a quick algorithm based on LabVIEW and a method of using external C code applied in the pick-up of photoelectric pulse wave were presented. Experimental verification was conducted in the environment of LabVIEW. The results show that by the method pres ented, the speed of operation was promoted rapidly and the data memory was reduced largely.

  16. Spectrographs for the Measurement of Radial Velocities

    NASA Astrophysics Data System (ADS)

    Baranne, A.

    A radial-velocity measurement derives from a shift in position of spectral features at the focus of a spectrographic instrument. We do not often think about how small these shifts are. It is not generally appreciated that the accuracy to which this shift must be measured is a tiny fraction of a pixel. Or, if we prefer to calculate in microns a surprising minuteness. What precautions should we be taking for the measurement of such small shifts? It is true that, thanks to computers, modern reduction methods allows us to correct for a wide variety of pertubations, provided that these are foreseen and understood; but such reduction procedures will give the best results if such pertubations are kept very small. We must therefore analyse these pertubations and think about how we can control them. The correlation method initiated in its modern form by Roger Griffin, and which we developed further with an optical mask in CORAVEL twenty-five years ago and more recently with a numerical mask in ELODIE, has demonstrated its power. In terms of these methods, the problem of high precision is to improve the correlation peak. Can this be done? Does the correlation method allow us to distinguish the overall radial velocity of the object from possible distortions of the lines? This is certainly a major problem which must be solved. The luminous efficiency of high-precision spectrographs is low. If the use of an optical fibre with scrambling for feeding the spectrograph seems inevitable to us today, it seems to me that the transmission of this system can be considerably improved by a better choice of the F-ratio of the image beam of the telescope which is to be matched with that of the spectrograph. This problem, common to all spectrographs, could be resolved with a specialised focal-plane instrument, giving a much greater than usual F-ratio, resulting in a simplification of the spectrograph optics, and hence an improvement in transmission and a serious decrease in size (which is

  17. Out-of-plane ultrasonic velocity measurement

    DOEpatents

    Hall, M.S.; Brodeur, P.H.; Jackson, T.G.

    1998-07-14

    A method for improving the accuracy of measuring the velocity and time of flight of ultrasonic signals through moving web-like materials such as paper, paperboard and the like, includes a pair of ultrasonic transducers disposed on opposing sides of a moving web-like material. In order to provide acoustical coupling between the transducers and the web-like material, the transducers are disposed in fluid-filled wheels. Errors due to variances in the wheel thicknesses about their circumference which can affect time of flight measurements and ultimately the mechanical property being tested are compensated by averaging the ultrasonic signals for a predetermined number of revolutions. The invention further includes a method for compensating for errors resulting from the digitization of the ultrasonic signals. More particularly, the invention includes a method for eliminating errors known as trigger jitter inherent with digitizing oscilloscopes used to digitize the signals for manipulation by a digital computer. In particular, rather than cross-correlate ultrasonic signals taken during different sample periods as is known in the art in order to determine the time of flight of the ultrasonic signal through the moving web, a pulse echo box is provided to enable cross-correlation of predetermined transmitted ultrasonic signals with predetermined reflected ultrasonic or echo signals during the sample period. By cross-correlating ultrasonic signals in the same sample period, the error associated with trigger jitter is eliminated. 20 figs.

  18. Out-of-plane ultrasonic velocity measurement

    DOEpatents

    Hall, Maclin S.; Brodeur, Pierre H.; Jackson, Theodore G.

    1998-01-01

    A method for improving the accuracy of measuring the velocity and time of flight of ultrasonic signals through moving web-like materials such as paper, paperboard and the like, includes a pair of ultrasonic transducers disposed on opposing sides of a moving web-like material. In order to provide acoustical coupling between the transducers and the web-like material, the transducers are disposed in fluid-filled wheels. Errors due to variances in the wheel thicknesses about their circumference which can affect time of flight measurements and ultimately the mechanical property being tested are compensated by averaging the ultrasonic signals for a predetermined number of revolutions. The invention further includes a method for compensating for errors resulting from the digitization of the ultrasonic signals. More particularly, the invention includes a method for eliminating errors known as trigger jitter inherent with digitizing oscilloscopes used to digitize the signals for manipulation by a digital computer. In particular, rather than cross-correlate ultrasonic signals taken during different sample periods as is known in the art in order to determine the time of flight of the ultrasonic signal through the moving web, a pulse echo box is provided to enable cross-correlation of predetermined transmitted ultrasonic signals with predetermined reflected ultrasonic or echo signals during the sample period. By cross-correlating ultrasonic signals in the same sample period, the error associated with trigger jitter is eliminated.

  19. A fast algorithm for the simulation of arterial pulse waves

    NASA Astrophysics Data System (ADS)

    Du, Tao; Hu, Dan; Cai, David

    2016-06-01

    One-dimensional models have been widely used in studies of the propagation of blood pulse waves in large arterial trees. Under a periodic driving of the heartbeat, traditional numerical methods, such as the Lax-Wendroff method, are employed to obtain asymptotic periodic solutions at large times. However, these methods are severely constrained by the CFL condition due to large pulse wave speed. In this work, we develop a new numerical algorithm to overcome this constraint. First, we reformulate the model system of pulse wave propagation using a set of Riemann variables and derive a new form of boundary conditions at the inlet, the outlets, and the bifurcation points of the arterial tree. The new form of the boundary conditions enables us to design a convergent iterative method to enforce the boundary conditions. Then, after exchanging the spatial and temporal coordinates of the model system, we apply the Lax-Wendroff method in the exchanged coordinate system, which turns the large pulse wave speed from a liability to a benefit, to solve the wave equation in each artery of the model arterial system. Our numerical studies show that our new algorithm is stable and can perform ∼15 times faster than the traditional implementation of the Lax-Wendroff method under the requirement that the relative numerical error of blood pressure be smaller than one percent, which is much smaller than the modeling error.

  20. Effects of horizontal velocity variations on ultrasonic velocity measurements in open channels

    USGS Publications Warehouse

    Swain, E.D.

    1992-01-01

    Use of an ultrasonic velocity meter to determine discharge in open channels involves measuring the velocity in a line between transducers in the stream and relating that velocity to the average velocity in the stream. The standard method of calculating average velocity in the channel assumes that the velocity profile in the channel can be represented by the one-dimensional von Karman universal velocity profile. However, the velocity profile can be described by a two-dimensional equation that accounts for the horizontal velocity variations induced by the channel sides. An equation to calculate average velocity accounts for the two-dimensional variations in velocity within a stream. The use of this new equation to calculate average velocity was compared to the standard method in theoretical trapezoidal cross sections and in the L-31N and Snapper Creek Extension Canals near Miami, Florida. These comparisons indicate that the two-dimensional variations have the most significant effect in narrow, deep channels. Also, the two-dimensional effects may be significant in some field situations and need to be considered when determining average velocity and discharge with an ultrasonic velocity meter.

  1. Compressional velocity measurements for a highly fractured lunar anorthosite

    NASA Technical Reports Server (NTRS)

    Sondergeld, C. H.; Granryd, L. A.; Spetzler, H. A.

    1979-01-01

    The compressional wave (V sub p) velocities in three mutually perpendicular directions have been measured in lunar sample 60025,174, lunar anorthosite. V sub p measurements were made at ambient temperature and pressure and a new technique was developed to measure the velocities because of the tremendous acoustic wave attenuation of the lunar sample. The measured velocities were all less than 1 km/sec and displayed up to a 21% departure from the mean value of the three directions. The velocities agree with seismic wave velocities determined for the lunar surface at the collection site.

  2. The comparison of a novel continuous cardiac output monitor based on pulse wave transit time and echo Doppler during exercise.

    PubMed

    Sugo, Yoshihiro; Sakai, Tomoyuki; Terao, Mami; Ukawa, Teiji; Ochiai, Ryoichi

    2012-01-01

    A new technology called estimated continuous cardiac output (esCCO) uses pulse wave transit time (PWTT) obtained from an electrocardiogram and pulse oximeter to measure cardiac output (CO) non-invasively and continuously. This study was performed to evaluate the accuracy of esCCO during exercise testing. We compared esCCO with CO measured by the echo Doppler aortic velocity-time integral (VTIao_CO). The correlation coefficient between esCCO and VTIao_CO was r= 0.87 (n= 72). Bias and precision were 0.33 ± 0.95 L/min and percentage error was 31%. The esCCO could detect change in VTIao_CO larger than 1 L/min with a concordance rate of 88%. In polar plot, 83% of data are within 0.5 L/min, and 100% of data are within 1 L/min. Those results show the acceptable accuracy and trend ability of esCCO. Change in pre-ejection period (PEP) measured by using M-mode of Diagnostic Ultrasound System accounted for approximately half of change in PWTT. This indicates that PEP included in PWTT has an impact on the accuracy of esCCO measurement. In this study, the validity of esCCO during exercise testing was assessed and shown to be acceptable. The result of this study suggests that we can expand its application.

  3. FSI Simulations of Pulse Wave Propagation in Human Abdominal Aortic Aneurysm: The Effects of Sac Geometry and Stiffness

    PubMed Central

    Li, Han; Lin, Kexin; Shahmirzadi, Danial

    2016-01-01

    This study aims to quantify the effects of geometry and stiffness of aneurysms on the pulse wave velocity (PWV) and propagation in fluid–solid interaction (FSI) simulations of arterial pulsatile flow. Spatiotemporal maps of both the wall displacement and fluid velocity were generated in order to obtain the pulse wave propagation through fluid and solid media, and to examine the interactions between the two waves. The results indicate that the presence of abdominal aortic aneurysm (AAA) sac and variations in the sac modulus affect the propagation of the pulse waves both qualitatively (eg, patterns of change of forward and reflective waves) and quantitatively (eg, decreasing of PWV within the sac and its increase beyond the sac as the sac stiffness increases). The sac region is particularly identified on the spatiotemporal maps with a region of disruption in the wave propagation with multiple short-traveling forward/reflected waves, which is caused by the change in boundary conditions within the saccular region. The change in sac stiffness, however, is more pronounced on the wall displacement spatiotemporal maps compared to those of fluid velocity. We conclude that the existence of the sac can be identified based on the solid and fluid pulse waves, while the sac properties can also be estimated. This study demonstrates the initial findings in numerical simulations of FSI dynamics during arterial pulsations that can be used as reference for experimental and in vivo studies. Future studies are needed to demonstrate the feasibility of the method in identifying very mild sacs, which cannot be detected from medical imaging, where the material property degradation exists under early disease initiation. PMID:27478394

  4. Measuring global monopole velocities, one by one

    NASA Astrophysics Data System (ADS)

    Lopez-Eiguren, Asier; Urrestilla, Jon; Achúcarro, Ana

    2017-01-01

    We present an estimation of the average velocity of a network of global monopoles in a cosmological setting using large numerical simulations. In order to obtain the value of the velocity, we improve some already known methods, and present a new one. This new method estimates individual global monopole velocities in a network, by means of detecting each monopole position in the lattice and following the path described by each one of them. Using our new estimate we can settle an open question previously posed in the literature: velocity-dependent one-scale (VOS) models for global monopoles predict two branches of scaling solutions, one with monopoles moving at subluminal speeds and one with monopoles moving at luminal speeds. Previous attempts to estimate monopole velocities had large uncertainties and were not able to settle that question. Our simulations find no evidence of a luminal branch. We also estimate the values of the parameters of the VOS model. With our new method we can also study the microphysics of the complicated dynamics of individual monopoles. Finally we use our large simulation volume to compare the results from the different estimator methods, as well as to asses the validity of the numerical approximations made.

  5. Acceleration and Velocity Sensing from Measured Strain

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi; Truax, Roger

    2016-01-01

    A simple approach for computing acceleration and velocity of a structure from the strain is proposed in this study. First, deflection and slope of the structure are computed from the strain using a two-step theory. Frequencies of the structure are computed from the time histories of strain using a parameter estimation technique together with an Autoregressive Moving Average model. From deflection, slope, and frequencies of the structure, acceleration and velocity of the structure can be obtained using the proposed approach. shape sensing, fiber optic strain sensor, system equivalent reduction and expansion process.

  6. Radial velocity measurements in the F corona

    NASA Astrophysics Data System (ADS)

    Beavers, W. I.; Eitter, J. J.; Carr, P. H.; Cook, B. C.

    1980-05-01

    A photoelectric radial velocity spectrometer was employed at the February 26, 1979 total solar eclipse in an attempt to detect motion in the F corona. Multiple dip features were recorded in scans made at points 3.2 and 4.3 solar radii west of the sun. By employing simple dynamic models these observations may be interpreted as evidence of the following two separate components of dust in the inner regions of the solar system: dust moving in prograde orbits outside the region beginning at about four solar radii from the sun, and dust falling into the sun with velocities from about 50 to 250 km/s.

  7. Flexible pulse-wave sensors from oriented aluminum nitride nanocolumns

    NASA Astrophysics Data System (ADS)

    Akiyama, Morito; Ueno, Naohiro; Nonaka, Kazuhiro; Tateyama, Hiroshi

    2003-03-01

    Flexible pulse-wave sensors were fabricated from density-packed oriented aluminum nitride nanocolumns prepared on aluminum foils. The nanocolumns were prepared by the rf magnetron sputtering method and were perpendicularly oriented to the aluminum foil surfaces. The sensor structure is laminated, and the structure contributes to avoiding unexpected leakage of an electric charge. The resulting sensor thickness is 50 μm. The sensor is flexible like aluminum foil and can respond to frequencies from 0.1 to over 100 Hz. The sensitivity of the sensor to pressure is proportional to the surface area. The sensor sensitively causes reversible charge signals that correlate with the pulse wave form, which contains significant information on arteriosclerosis and cardiopathy of a man sitting on it.

  8. Acceleration and Velocity Sensing from Measured Strain

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi; Truax, Roger

    2015-01-01

    A simple approach for computing acceleration and velocity of a structure from the strain is proposed in this study. First, deflection and slope of the structure are computed from the strain using a two-step theory. Frequencies of the structure are computed from the time histories of strain using a parameter estimation technique together with an autoregressive moving average model. From deflection, slope, and frequencies of the structure, acceleration and velocity of the structure can be obtained using the proposed approach. Simple harmonic motion is assumed for the acceleration computations, and the central difference equation with a linear autoregressive model is used for the computations of velocity. A cantilevered rectangular wing model is used to validate the simple approach. Quality of the computed deflection, acceleration, and velocity values are independent of the number of fibers. The central difference equation with a linear autoregressive model proposed in this study follows the target response with reasonable accuracy. Therefore, the handicap of the backward difference equation, phase shift, is successfully overcome.

  9. Accurate Sound Velocity Measurement in Ocean Near-Surface Layer

    NASA Astrophysics Data System (ADS)

    Lizarralde, D.; Xu, B. L.

    2015-12-01

    Accurate sound velocity measurement is essential in oceanography because sound is the only wave that can propagate in sea water. Due to its measuring difficulties, sound velocity is often not measured directly but instead calculated from water temperature, salinity, and depth, which are much easier to obtain. This research develops a new method to directly measure the sound velocity in the ocean's near-surface layer using multi-channel seismic (MCS) hydrophones. This system consists of a device to make a sound pulse and a long cable with hundreds of hydrophones to record the sound. The distance between the source and each receiver is the offset. The time it takes the pulse to arrive to each receiver is the travel time.The errors of measuring offset and travel time will affect the accuracy of sound velocity if we calculated with just one offset and one travel time. However, by analyzing the direct arrival signal from hundreds of receivers, the velocity can be determined as the slope of a straight line in the travel time-offset graph. The errors in distance and time measurement result in only an up or down shift of the line and do not affect the slope. This research uses MCS data of survey MGL1408 obtained from the Marine Geoscience Data System and processed with Seismic Unix. The sound velocity can be directly measured to an accuracy of less than 1m/s. The included graph shows the directly measured velocity verses the calculated velocity along 100km across the Mid-Atlantic continental margin. The directly measured velocity shows a good coherence to the velocity computed from temperature and salinity. In addition, the fine variations in the sound velocity can be observed, which is hardly seen from the calculated velocity. Using this methodology, both large area acquisition and fine resolution can be achieved. This directly measured sound velocity will be a new and powerful tool in oceanography.

  10. The shock Hugoniot of 316 ss and sound velocity measurements

    SciTech Connect

    Hixson, R.S.; McQueen, R.G.; Fritz, J.N.

    1993-01-01

    Type 316 stainless steel has been characterized for its high-pressure, shock-wave response. Measurements have been made of shock-wave and particle velocity, and of sound velocity. Our preliminary results for shock and particle velocity have been combined with previously unpublished results, and an overall fit made. Sound velocity results show a discontinuity that is attributed to shock-induced melting.

  11. The shock Hugoniot of 316 ss and sound velocity measurements

    SciTech Connect

    Hixson, R.S.; McQueen, R.G.; Fritz, J.N.

    1993-07-01

    Type 316 stainless steel has been characterized for its high-pressure, shock-wave response. Measurements have been made of shock-wave and particle velocity, and of sound velocity. Our preliminary results for shock and particle velocity have been combined with previously unpublished results, and an overall fit made. Sound velocity results show a discontinuity that is attributed to shock-induced melting.

  12. [A mathematical model of hemodynamic processes for distal pulse wave formation].

    PubMed

    Fedotov, A A

    2015-01-01

    A mathematical model of the formation of distal arterial pulse wave signal in the blood vessels of the upper limbs was considered. The formation of distal arterial pulse wave is represented as a composition of forward and reverse pulse waves propagating along the human arterial system. The system of formal analogy between pulse waves propagation along the human arterial system and the propagation of electrical oscillations in electrical transmission lines with distributed parameters was proposed. Dependencies of pulse wave propagation along the human arterial system were obtained by solving the one-dimensional Navier-Stokes equations for a few special cases.

  13. Shared velocity encoding: a method to improve the temporal resolution of phase-contrast velocity measurements.

    PubMed

    Lin, Hung-Yu; Bender, Jacob A; Ding, Yu; Chung, Yiu-Cho; Hinton, Alice M; Pennell, Michael L; Whitehead, Kevin K; Raman, Subha V; Simonetti, Orlando P

    2012-09-01

    Phase-contrast magnetic resonance imaging (PC-MRI) is used routinely to measure fluid and tissue velocity with a variety of clinical applications. Phase-contrast magnetic resonance imaging methods require acquisition of additional data to enable phase difference reconstruction, making real-time imaging problematic. Shared Velocity Encoding (SVE), a method devised to improve the effective temporal resolution of phase-contrast magnetic resonance imaging, was implemented in a real-time pulse sequence with segmented echo planar readout. The effect of SVE on peak velocity measurement was investigated in computer simulation, and peak velocities and total flow were measured in a flow phantom and in volunteers and compared with a conventional ECG-triggered, segmented k-space phase-contrast sequence as a reference standard. Computer simulation showed a 36% reduction in peak velocity error from 8.8 to 5.6% with SVE. A similar reduction of 40% in peak velocity error was shown in a pulsatile flow phantom. In the phantom and volunteers, volume flow did not differ significantly when measured with or without SVE. Peak velocity measurements made in the volunteers using SVE showed a higher concordance correlation (0.96) with the reference standard than non-SVE (0.87). The improvement in effective temporal resolution with SVE reconstruction has a positive impact on the precision and accuracy of real-time phase-contrast magnetic resonance imaging peak velocity measurements.

  14. A Skin-attachable Flexible Piezoelectric Pulse Wave Energy Harvester

    NASA Astrophysics Data System (ADS)

    Yoon, Sunghyun; Cho, Young-Ho

    2014-11-01

    We present a flexible piezoelectric generator, capable to harvest energy from human arterial pulse wave on the human wrist. Special features and advantages of the flexible piezoelectric generator include the multi-layer device design with contact windows and the simple fabrication process for the higher flexibility with the better energy harvesting efficiency. We have demonstrated the design effectiveness and the process simplicity of our skin- attachable flexible piezoelectric pulse wave energy harvester, composed of the sensitive P(VDF-TrFE) piezoelectric layer on the flexible polyimide support layer with windows. We experimentally characterize and demonstrate the energy harvesting capability of 0.2~1.0μW in the Human heart rate range on the skin contact area of 3.71cm2. Additional physiological and/or vital signal monitoring devices can be fabricated and integrated on the skin attachable flexible generator, covered by an insulation layer; thus demonstrating the potentials and advantages of the present device for such applications to the flexible multi-functional selfpowered artificial skins, capable to detect physiological and/or vital signals on Human skin using the energy harvested from arterial pulse waves.

  15. Laser Doppler anemometer signal processing for blood flow velocity measurements

    SciTech Connect

    Borozdova, M A; Fedosov, I V; Tuchin, V V

    2015-03-31

    A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (laser applications and other topics in quantum electronics)

  16. Mean velocities measured with the double pulse technique

    NASA Astrophysics Data System (ADS)

    Nielsen, E.

    2004-10-01

    It was recently observed that double-pulse measurements of the mean velocities of a wide asymmetric spectrum are a function of the time lag between the pulses (Uspensky et al., 2004). Here we demonstrate that the observed relationship probably is influenced by the measurement technique in a way that is consistent with theoretical prediction. It is further shown that for small time lags the double pulse velocity is a good approximation to the mean Doppler velo-city.

  17. Effects of Acupuncture Stimulation on the Radial artery’s Pressure Pulse Wave in Healthy Young Participants: Protocol for a prospective, single-Arm, Exploratory, Clinical Study

    PubMed Central

    Shin, Jae-Young; Lee, Jun-Hwan; Ku, Boncho; Bae, Jang Han; un, Min-Ho; Kim, Jaeuk U.; Kim, Tae-Hun

    2016-01-01

    Introduction: This study aims to investigate the effects of acupuncture stimulation on the radial artery’s pressure pulse wave, along with various hemodynamic parameters, and to explore the possible underlying mechanism of pulse diagnosis in healthy participants in their twenties. Methods and analysis: This study is a prospective, single-arm, exploratory clinical study. A total of 25 healthy participants, without regard to gender, in their twenties will be recruited by physicians. Written informed consent will be obtained from all participants. The participants will receive acupuncture once at ST36 on both sides. The radial arterial pulse waves will be measured on the left arm of the subjects by using an applicable pulse tonometric device (KIOM-PAS). On the right arm (appearing twice), electrocardiogram (ECG), photoplethysmogram (PPG), respiration and cardiac output (CO) signals, will be measured using a physiological data acquisition system (Biopac module), while the velocity of blood flow, and the diameter and the depth of the blood vessel will be measured using an ultrasonogram machine on the right arm (appearing twice). All measurements will be conducted before, during, and after acupuncture. The primary outcome will be the spectral energy at high frequencies above 10 Hz (SE10-30Hz) calculated from the KIOM-PAS device signal. Secondary outcomes will be various variables obtained from the KIOM-PAS device, ECG, PPG, impedance cardiography modules, and an ultrasonogram machine. Discussion: The results of this trial will provide information regarding the physiological and the hemodynamic mechanisms underlying acupuncture stimulation and clinical evidence for the influence of acupuncture on the pressure pulse wave in the radial artery. Ethics and dissemination: This study was approved by the Institutional Review Board (IRB) of Kyung Hee University’s Oriental Medical Center, Seoul, Korea (KOMCIRB-150818-HR-030). The study findings will be published in peer

  18. A Distinguishing Arterial Pulse Waves Approach by Using Image Processing and Feature Extraction Technique.

    PubMed

    Chen, Hsing-Chung; Kuo, Shyi-Shiun; Sun, Shen-Ching; Chang, Chia-Hui

    2016-10-01

    Traditional Chinese Medicine (TCM) is based on five main types of diagnoses methods consisting of inspection, auscultation, olfaction, inquiry, and palpation. The most important one is palpation also called pulse diagnosis which is to measure wrist artery pulse by doctor's fingers for detecting patient's health state. In this paper, it is carried out by using a specialized pulse measuring instrument to classify one's pulse type. The measured pulse waves (MPWs) were segmented into the arterial pulse wave curve (APWC) by image proposing method. The slopes and periods among four specific points on the APWC were taken to be the pulse features. Three algorithms are proposed in this paper, which could extract these features from the APWCs and compared their differences between each of them to the average feature matrix, individually. These results show that the method proposed in this study is superior and more accurate than the previous studies. The proposed method could significantly save doctors a large amount of time, increase accuracy and decrease data volume.

  19. Free-surface velocity measurements using an optically recording velocity interferometer

    NASA Astrophysics Data System (ADS)

    Lu, Jian-xin; Wang, Zhao; Liang, Jing; Shan, Yu-sheng; Zhou, Chuang-zhi; Xiang, Yi-huai; Lu, Ze; Tang, Xiu-zhang

    2007-01-01

    An optically recording velocity interferometer system (ORVIS) was developed for the free-surface velocity measurements in the equation of state experiments. The time history of free-surface velocity and the particle velocity in laser deduced shockwaves experiments can be recorded by the electronic streak camera in ORVIS. The interference fringe shifts recorded by the ORVIS is proportional to the Doppler shift of a laser beam induced by being reflected from the back suface of the monitored target. In the experiments, ORVIS got an 179 ps time resolution, and a higher time resolution could be got by minimizing the delay time. The equation of state experiments were carried out on the high power excimer laser system called "Heaven I", the velocity of iron and aluminium was researched.

  20. Velocity precision measurements using laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Dopheide, D.; Taux, G.; Narjes, L.

    1985-07-01

    A Laser Doppler Anemometer (LDA) was calibrated to determine its applicability to high pressure measurements (up to 10 bars) for industrial purposes. The measurement procedure with LDA and the experimental computerized layouts are presented. The calibration procedure is based on absolute accuracy of Doppler frequency and calibration of interference strip intervals. A four-quadrant detector allows comparison of the interference strip distance measurements and computer profiles. Further development of LDA is recommended to increase accuracy (0.1% inaccuracy) and to apply the method industrially.

  1. Laser Doppler anemometer measurements using nonorthogonal velocity components - Error estimates

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Snyder, P. K.

    1982-01-01

    Laser Doppler anemometers (LDAs) that are arranged to measure nonorthogonal velocity components (from which orthogonal components are computed through transformation equations) are more susceptible to calibration and sampling errors than are systems with uncoupled channels. In this paper uncertainty methods and estimation theory are used to evaluate, respectively, the systematic and statistical errors that are present when such devices are applied to the measurement of mean velocities in turbulent flows. Statistical errors are estimated for two-channel LDA data that are either correlated or uncorrelated. For uncorrelated data the directional uncertainty of the measured velocity vector is considered for applications where mean streamline patterns are desired.

  2. Laser Doppler anemometer measurements using nonorthogonal velocity components: error estimates.

    PubMed

    Orloff, K L; Snyder, P K

    1982-01-15

    Laser Doppler anemometers (LDAs) that are arranged to measure nonorthogonal velocity components (from which orthogonal components are computed through transformation equations) are more susceptible to calibration and sampling errors than are systems with uncoupled channels. In this paper uncertainty methods and estimation theory are used to evaluate, respectively, the systematic and statistical errors that are present when such devices are applied to the measurement of mean velocities in turbulent flows. Statistical errors are estimated for two-channel LDA data that are either correlated or uncorrelated. For uncorrelated data the directional uncertainty of the measured velocity vector is considered for applications where mean streamline patterns are desired.

  3. Measuring Stellar Radial Velocities with a LISA Spectrograph

    NASA Astrophysics Data System (ADS)

    Boyd, David

    2016-05-01

    Conventional wisdom says it should not be possible to measure stellar radial velocities with a useful degree of precision with a spectrograph having spectral resolution of 1000. This paper will demonstrate that with a combination of careful observational technique and the use of cross correlation it is possible to far exceed initial expectations. This is confirmed by reproducing the known radial velocity of a catalogued SB1 star with a precision of 5.2 km/s. To demonstrate the scientific potential of such a spectrograph, we use radial velocity measurements to confirm the binary nature and measure the orbital period and parameters of a suspected post common envelope binary.

  4. Unsteady Pressure and Velocity Measurements in Pumps

    DTIC Science & Technology

    2006-11-01

    to reproduce the data with controlled experiments . For example, the rotor exit flow measured by means of a stationary high response probe will be...Turbomachinery by Means of High-Frequency Pressure Transducers. ASME, J. of Turbomachinery, Vol. 114, pp. 100-107. [3] Castorph, D. (1975): Messung ...Dreiß, A.; Kosyna, G. (1997): Experimental Investigations of Cavitation-States in a Radial Pump Impeller. JSME CENTENNIAL GRAND CONGRESS Proceedings of

  5. Three Component Velocity and Acceleration Measurement Using FLEET

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Bathel, Brett F.; Calvert, Nathan; Dogariu, Arthur; Miles, Richard P.

    2014-01-01

    The femtosecond laser electronic excitation and tagging (FLEET) method has been used to measure three components of velocity and acceleration for the first time. A jet of pure N2 issuing into atmospheric pressure air was probed by the FLEET system. The femtosecond laser was focused down to a point to create a small measurement volume in the flow. The long-lived lifetime of this fluorescence was used to measure the location of the tagged particles at different times. Simultaneous images of the flow were taken from two orthogonal views using a mirror assembly and a single intensified CCD camera, allowing two components of velocity to be measured in each view. These different velocity components were combined to determine three orthogonal velocity components. The differences between subsequent velocity components could be used to measure the acceleration. Velocity accuracy and precision were roughly estimated to be +/-4 m/s and +/-10 m/s respectively. These errors were small compared to the approx. 100 m/s velocity of the subsonic jet studied.

  6. Measuring the Stellar Halo Velocity Anisotropy With 3D Kinematics

    NASA Astrophysics Data System (ADS)

    Cunningham, Emily C.; Deason, Alis J.; Guhathakurta, Puragra; Rockosi, Constance M.; van der Marel, Roeland P.; Sohn, S. Tony

    2016-08-01

    We present the first measurement of the anisotropy parameter β using 3D kinematic information outside of the solar neighborhood. Our sample consists of 13 Milky Way halo stars with measured proper motions and radial velocities in the line of sight of M31. Proper motions were measured using deep, multi-epoch HST imaging, and radial velocities were measured from Keck II/DEIMOS spectra. We measure β = -0.3-0.9 +0.4, which is consistent with isotropy, and inconsistent with measurements in the solar neighborhood. We suggest that this may be the kinematic signature of a relatively early, massive accretion event, or perhaps several such events.

  7. Near-wall velocity profile measurement for nanofluids

    NASA Astrophysics Data System (ADS)

    Kanjirakat, Anoop; Sadr, Reza

    2016-01-01

    We perform near-wall velocity measurements of a SiO2-water nanofluid inside a microchannel. Nanoparticle image velocimetry measurements at three visible depths within 500 nm of the wall are conducted. We evaluate the optical properties of the nanofluid and their effect on the measurement technique. The results indicate that the small effect of the nanoparticles on the optical properties of the suspension have a negligible effect on the measurement technique. Our measurements show an increase in nanofluid velocity gradients near the walls, with no measurable slip, relative to the equivalent basefluid flow. We conjecture that particle migration induced by shear may have caused this increase. The effect of this increase in the measured near wall velocity gradient has implications on the viscosity measurement for these fluids.

  8. Exploratory Meeting on Airborne Doppler Lidar Wind Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Fichtel, G. H. (Editor); Kaufman, J. W. (Editor); Vaughan, W. W. (Editor)

    1980-01-01

    The scientific interests and applications of the Airborne Doppler Lidar Wind Velocity Measurement System to severe storms and local weather are discussed. The main areas include convective phenomena, local circulation, atmospheric boundary layer, atmospheric dispersion, and industrial aerodynamics.

  9. 33. BENTZEL TUBE. A CURRENT VELOCITY MEASURING DEVICE DEVELOPED AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    33. BENTZEL TUBE. A CURRENT VELOCITY MEASURING DEVICE DEVELOPED AT WES IN 1932 BY CARL E. BENTZEL. - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

  10. Tip vortex core pressure estimates derived from velocity field measurements

    NASA Astrophysics Data System (ADS)

    Sinding, Kyle; Krane, Michael

    2016-11-01

    We present estimates of tip vortex core pressure derived from velocity field measurements of a high Reynolds number flow over a lifting surface. Tip vortex cavitation decreases propulsor efficiency and contributes to both unwanted noise and surface damage. Coordinated load cell, pressure, and velocity measurements were performed in the 12-inch tunnel at the Applied Research Laboratory at Penn State University, over a range of angles of attack and flow speeds. Stereo PIV imaging planes were oriented normal to the tunnel axis. Pressure estimates in each measurement plane were estimated from the velocity field. Visual cavitation calls were performed over the same range of conditions as the optical velocity measurements, by varying the tunnel pressure until tip vortex cavitation was observed to initiate. The pressure differences between the tip vortex and the tunnel ambient pressure obtained with these two methods were then compared.

  11. In-situ application of Ultrasonic Pulse Velocity measurements to determine the degree of zeolitic alteration of ignimbrites

    NASA Astrophysics Data System (ADS)

    Evren Çubukçu, H.; Yurdakul, Yasin; Erkut, Volkan; Akkaş, Efe; Akın, Lütfiye; Ulusoy, İnan; Şen, Erdal

    2016-04-01

    -wave velocities are positively correlated with the degree of zeolitization, where the highest velocities correspond to the intensely zeolitized ignimbrites. In-situ application of UPV measurements in the field can be utilized for revealing the spatial variation in zeolitization and for locating the probable sources responsible for hydrothermal alteration. Keywords: ultrasonic pulse wave, in-situ, ignimbrite, hydrothermal alteration, zeolitization

  12. Continuous measurements of in-bore projectile velocity

    SciTech Connect

    Asay, J.R.; Konrad, C.H.; Hall, C.A.; Shahinpoor, M.; Hickman, R.

    1988-01-01

    The application of velocity interferometry to the continuous measurement of in-bore projectile velocity in a small-bore three-stage railgun is described. These measurements are useful for determining projectile acceleration and for evaluating gun performance. The launcher employed in these studies consists of a two-stage light gas gun used to inject projectiles into a railgun for additional acceleration. Results obtained for projectile velocities to 7.4 km/s with the two-stage injector are reported and potential improvements for railgun applications are discussed. 12 refs., 7 figs.

  13. Velocity field measurements of a laminar starting plume

    NASA Astrophysics Data System (ADS)

    Tanny, J.; Shlien, D. J.

    1985-04-01

    The region of buoyant fluid resulting from the initiation of heating of an infinite fluid is called the starting plume. Here, velocity field measurements of this flow pattern are presented for the first time. The measurements were carried out by processing digitized tracer particle path photographs. Similarity of the velocity field of the starting plume as it rises was found to exist in the limited range of heat injection rates investigated. The vorticity computed from the velocity field was diffuse, there being no evidence of a distinctive core. Additional flow visualization experiments show the spiral structure in the starting plume cap.

  14. Measurement of Poloidal Velocity on the National Spherical Torus Experiment

    SciTech Connect

    Ronald E. Bell and Russell Feder

    2010-06-04

    A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  15. Measurement of angular velocity in the perception of rotation.

    PubMed

    Barraza, José F; Grzywacz, Norberto M

    2002-09-01

    Humans are sensitive to the parameters of translational motion, namely, direction and speed. At the same time, people have special mechanisms to deal with more complex motions, such as rotations and expansions. One wonders whether people may also be sensitive to the parameters of these complex motions. Here, we report on a series of experiments that explore whether human subjects can use angular velocity to evaluate how fast a rotational motion is. In four experiments, subjects were required to perform a task of speed-of-rotation discrimination by comparing two annuli of different radii in a temporal 2AFC paradigm. Results showed that humans could rely on a sensitive measurement of angular velocity to perform this discrimination task. This was especially true when the quality of the rotational signal was high (given by the number of dots composing the annulus). When the signal quality decreased, a bias towards linear velocity of 5-80% appeared, suggesting the existence of separate mechanisms for angular and linear velocity. This bias was independent from the reference radius. Finally, we asked whether the measurement of angular velocity required a rigid rotation, that is, whether the visual system makes only one global estimate of angular velocity. For this purpose, a random-dot disk was built such that all the dots were rotating with the same tangential speed, irrespectively of radius. Results showed that subjects do not estimate a unique global angular velocity, but that they perceive a non-rigid disk, with angular velocity falling inversely proportionally with radius.

  16. Velocity measurement by coherent x-ray heterodyning

    SciTech Connect

    Lhermitte, Julien R. M.; Rogers, Michael C.; Manet, Sabine; Sutton, Mark

    2017-01-01

    We present a small-angle coherent x-ray scattering technique used for measuring flow velocities in slow moving materials. The technique is an extension of X-ray Photon Correlation Spectroscopy (XPCS): It involves mixing the scattering from moving tracer particles with a static reference that heterodynes the signal. This acts to elongate temporal effects caused by flow in homodyne measurements, allowing for a more robust measurement of flow properties. Using coherent x-ray heterodyning, velocities ranging from 0.1 to 10 μm/s were measured for a viscous fluid pushed through a rectangular channel. We describe experimental protocols and theory for making these Poiseuille flow profile measurements and also develop the relevant theory for using heterodyne XPCS to measure velocities in uniform and Couette flows.

  17. Development of a Standard Protocol for the Harmonic Analysis of Radial Pulse Wave and Assessing Its Reliability in Healthy Humans.

    PubMed

    Chang, Chi-Wei; Chen, Jiang-Ming; Wang, Wei-Kung

    2015-01-01

    This study was aimed to establish a standard protocol and to quantitatively assess the reliability of harmonic analysis of the radial pulse wave measured by a harmonic wave analyzer (TD01C system). Both intraobserver and interobserver assessments were conducted to investigate whether the values of harmonics are stable in successive measurements. An intraclass correlation coefficient (ICC) and a Bland-Altman plot were used for this purpose. For the reliability assessments of the intraobserver and the interobserver, 22 subjects (mean age 45 ± 14 years; 14 males and 8 females) were enrolled. The first eleven harmonics of the radial pulse wave presented excellent repeatability ([Formula: see text] and [Formula: see text]) for the intraobserver assessment and high reproducibility (ICCs range from 0.83 to 0.96 and [Formula: see text]) for the interobserver assessment. The Bland-Altman plot indicated that more than 90% of harmonic values fell within two standard deviations of the mean difference. Thus, we concluded that the harmonic analysis of the radial pulse wave using the TD01C system is a feasible and reliable method to assess a hemodynamic characteristic in clinical trial.

  18. Pulse wave analysis in a 180-degree curved artery model: Implications under physiological and non-physiological inflows

    NASA Astrophysics Data System (ADS)

    Bulusu, Kartik V.; Plesniak, Michael W.

    2013-11-01

    Systolic and diastolic blood pressures, pulse pressures, and left ventricular hypertrophy contribute to cardiovascular risks. Increase of arterial stiffness due to aging and hypertension is an important factor in cardiovascular, chronic kidney and end-stage-renal-diseases. Pulse wave analysis (PWA) based on arterial pressure wave characteristics, is well established in clinical practice for evaluation of arterial distensibility and hypertension. The objective of our exploratory study in a rigid 180-degree curved artery model was to evaluate arterial pressure waveforms. Bend upstream conditions were measured using a two-component, two-dimensional, particle image velocimeter (2C-2D PIV). An ultrasonic transit-time flow meter and a catheter with a MEMS-based solid state pressure sensor, capable of measuring up to 20 harmonics of the observed pressure waveform, monitored flow conditions downstream of the bend. Our novel continuous wavelet transform algorithm (PIVlet 1.2), in addition to detecting coherent secondary flow structures is used to evaluate arterial pulse wave characteristics subjected to physiological and non-physiological inflows. Results of this study will elucidate the utility of wavelet transforms in arterial function evaluation and pulse wave speed. Supported by NSF Grant No. CBET- 0828903 and GW Center for Biomimetics and Bioinspired Engineering.

  19. Measuring the equatorial plasma bubble drift velocities over Morroco

    NASA Astrophysics Data System (ADS)

    Lagheryeb, Amine; Benkhaldoun, Zouhair; Makela, Jonathan J.; Harding, Brian; Kaab, Mohamed; Lazrek, Mohamed; Fisher, Daniel J.; Duly, Timothy M.; Bounhir, Aziza; Daassou, Ahmed

    2015-08-01

    In this work, we present a method to measure the drift velocities of equatorial plasma bubbles (EPBs) in the low latitude ionosphere. To calculate the EPB drift velocity, we use 630.0-nm airglow images collected by the Portable Ionospheric Camera and Small Scale Observatory (PICASSO) system deployed at the Oukkaimden observatory in Morocco. To extract the drift velocity, the individual images were processed by first spatially registering the images using the star field. After this, the stars were removed from the images using a point suppression methodology, the images were projected into geographic coordinates assuming an airglow emission altitude of 250 km. Once the images were projected into geographic coordinates, the intensities of the airglow along a line of constant geomagnetic latitude (31°) are used to detect the presence of an EPB, which shows up as a depletion in airglow intensity. To calculate the EPB drift velocity, we divide the spatial lag between depletions found in two images (found by the application of correlation analysis) by the time difference between these two images. With multiple images, we will have several velocity values and consequently we can draw the EPB drift velocity curve. Future analysis will compare the estimates of the plasma drift velocity with the thermospheric neutral wind velocity estimated by a collocated Fabry-Perot interferometer (FPI) at the observatory.

  20. Measuring discharge with ADCPs: Inferences from synthetic velocity profiles

    USGS Publications Warehouse

    Rehmann, C.R.; Mueller, D.S.; Oberg, K.A.

    2009-01-01

    Synthetic velocity profiles are used to determine guidelines for sampling discharge with acoustic Doppler current profilers (ADCPs). The analysis allows the effects of instrument characteristics, sampling parameters, and properties of the flow to be studied systematically. For mid-section measurements, the averaging time required for a single profile measurement always exceeded the 40 s usually recommended for velocity measurements, and it increased with increasing sample interval and increasing time scale of the large eddies. Similarly, simulations of transect measurements show that discharge error decreases as the number of large eddies sampled increases. The simulations allow sampling criteria that account for the physics of the flow to be developed. ?? 2009 ASCE.

  1. Measurements of velocity and discharge, Grand Canyon, Arizona, May 1994

    USGS Publications Warehouse

    Oberg, Kevin A.; Fisk, Gregory G.; ,

    1995-01-01

    The U.S. Geological Survey (USGS) evaluated the feasibility of utilizing an acoustic Doppler current profiler (ADCP) to collect velocity and discharge data in the Colorado River in Grand Canyon, Arizona, in May 1994. An ADCP is an instrument that can be used to measure water velocity and discharge from a moving boat. Measurements of velocity and discharge were made with an ADCP at 54 cross sections along the Colorado River between the Little Colorado River and Diamond Creek. Concurrent measurements of discharge with an ADCP and a Price-AA current meter were made at three U.S. Geological Survey streamflow-gaging stations: Colorado River above the Little Colorado River near Desert View, Colorado River near Grand Canyon, and Colorado River above Diamond Creek near Peach Springs. Discharges measured with an ADCP were within 3 percent of the rated discharge at each streamflow-gaging station. Discharges measured with the ADCP were within 4 percent of discharges measured with a Price-AA meter, except at the Colorado River above Diamond Creek. Vertical velocity profiles were measured with the ADCP from a stationary position at four cross sections along the Colorado River. Graphs of selected vertical velocity profiles collected in a cross section near National Canyon show considerable temporal variation among profile.

  2. Corrections on LIFPA velocity measurements in microchannel with moderate velocity fluctuations

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Yang, Fang; Khan, Jamil; Reifsnider, Ken; Wang, Guiren

    2015-02-01

    Laser-induced fluorescence photobleaching anemometer (LIFPA) has been developed in order to measure velocity fluctuations of the unsteady micro electrokinetic turbulent flows in microfluidics. The statistical errors of LIFPA measurement, because of 3-D flows and Taylor's hypothesis (compared with local Taylor's hypothesis Pinton and Labbé in J Phys II 4:1461-1468, 1994), are theoretically estimated and compared to hot-wire anemometer (HWA) measurement that is used for conventional turbulence measurement. The correction factor in the direction parallel to the laser beam is estimated, and the influence of directional correction factors of LIFPA is also investigated. It is found that in our investigation, the error due to Taylor's hypothesis is negligible. The influence of 3-D flows on the first derivative variance of velocity fluctuations in LIFPA is smaller than that in HWA measurement.

  3. Pulse wave transit time for monitoring respiration rate.

    PubMed

    Johansson, A; Ahlstrom, C; Lanne, T; Ask, P

    2006-06-01

    In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring.

  4. Accurately measuring volcanic plume velocity with multiple UV spectrometers

    USGS Publications Warehouse

    Williams-Jones, Glyn; Horton, Keith A.; Elias, Tamar; Garbeil, Harold; Mouginis-Mark, Peter J; Sutton, A. Jeff; Harris, Andrew J. L.

    2006-01-01

    A fundamental problem with all ground-based remotely sensed measurements of volcanic gas flux is the difficulty in accurately measuring the velocity of the gas plume. Since a representative wind speed and direction are used as proxies for the actual plume velocity, there can be considerable uncertainty in reported gas flux values. Here we present a method that uses at least two time-synchronized simultaneously recording UV spectrometers (FLYSPECs) placed a known distance apart. By analyzing the time varying structure of SO2 concentration signals at each instrument, the plume velocity can accurately be determined. Experiments were conducted on Kīlauea (USA) and Masaya (Nicaragua) volcanoes in March and August 2003 at plume velocities between 1 and 10 m s−1. Concurrent ground-based anemometer measurements differed from FLYSPEC-measured plume speeds by up to 320%. This multi-spectrometer method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic or industrial gas flux measurements.

  5. A technique for measuring hypersonic flow velocity profiles

    NASA Technical Reports Server (NTRS)

    Gartrell, L. R.

    1973-01-01

    A technique for measuring hypersonic flow velocity profiles is described. This technique utilizes an arc-discharge-electron-beam system to produce a luminous disturbance in the flow. The time of flight of this disturbance was measured. Experimental tests were conducted in the Langley pilot model expansion tube. The measured velocities were of the order of 6000 m/sec over a free-stream density range from 0.000196 to 0.00186 kg/cu m. The fractional error in the velocity measurements was less than 5 percent. Long arc discharge columns (0.356 m) were generated under hypersonic flow conditions in the expansion-tube modified to operate as an expansion tunnel.

  6. Solenoidal filtering of volumetric velocity measurements using Gaussian process regression

    NASA Astrophysics Data System (ADS)

    Azijli, Iliass; Dwight, Richard P.

    2015-11-01

    Volumetric velocity measurements of incompressible flows contain spurious divergence due to measurement noise, despite mass conservation dictating that the velocity field must be divergence-free (solenoidal). We investigate the use of Gaussian process regression to filter spurious divergence, returning analytically solenoidal velocity fields. We denote the filter solenoidal Gaussian process regression (SGPR) and formulate it within the Bayesian framework to allow a natural inclusion of measurement uncertainty. To enable efficient handling of large data sets on regular and near-regular grids, we propose a solution procedure that exploits the Toeplitz structure of the system matrix. We apply SGPR to two synthetic and two experimental test cases and compare it with two other recently proposed solenoidal filters. For the synthetic test cases, we find that SGPR consistently returns more accurate velocity, vorticity and pressure fields. From the experimental test cases, we draw two important conclusions. Firstly, it is found that including an accurate model for the local measurement uncertainty further improves the accuracy of the velocity field reconstructed with SGPR. Secondly, it is found that all solenoidal filters result in an improved reconstruction of the pressure field, as verified with microphone measurements. The results obtained with SGPR are insensitive to correlation length, demonstrating the robustness of the filter to its parameters.

  7. Velocity Measurements of Turbulent Wake Flow Over a Circular Cylinder

    NASA Astrophysics Data System (ADS)

    Shih, Chang-Lung; Chen, Wei-Cheng; Chang, Keh-Chin; Wang, Muh-Rong

    2016-06-01

    There are two general concerns in the velocity measurements of turbulence. One is the temporal characteristics which governs the turbulent mixing process. Turbulence is rotational and is characterized by high levels of fluctuating vorticity. In order to obtain the information of vorticity dynamics, the spatial characteristics is the other concern. These varying needs can be satisfied by using a variety of diagnostic techniques such as invasive physical probes and non-invasive optical instruments. Probe techniques for the turbulent measurements are inherently simple and less expensive than optical methods. However, the presence of a physical probe may alter the flow field, and velocity measurements usually become questionable when probing recirculation zones. The non-invasive optical methods are mostly made of the foreign particles (or seeding) instead of the fluid flow and are, thus, of indirect method. The difference between the velocities of fluid and foreign particles is always an issue to be discussed particularly in the measurements of complicated turbulent flows. Velocity measurements of the turbulent wake flow over a circular cylinder will be made by using two invasive instruments, namely, a cross-type hot-wire anemometry (HWA) and a split-fiber hot-film anemometry (HFA), and a non-invasive optical instrument, namely, particle image velocimetry (PIV) in this study. Comparison results show that all three employed diagnostic techniques yield similar measurements in the mean velocity while somewhat deviated results in the root-mean-squared velocity, particularly for the PIV measurements. It is demonstrated that HFA possesses more capability than HWA in the flow measurements of wake flow. Wake width is determined in terms of either the flatness factor or shear-induced vorticity. It is demonstrated that flow data obtained with the three employed diagnostic techniques are capable of yielding accurate determination of wake width.

  8. Estimating Radar Velocity using Direction of Arrival Measurements

    SciTech Connect

    Doerry, Armin Walter; Horndt, Volker; Bickel, Douglas Lloyd; Naething, Richard M.

    2014-09-01

    Direction of Arrival (DOA) measurements, as with a monopulse antenna, can be compared against Doppler measurements in a Synthetic Aperture Radar ( SAR ) image to determine an aircraft's forward velocity as well as its crab angle, to assist the aircraft's navigation as well as improving high - performance SAR image formation and spatial calibration.

  9. Using embedded fibers to measure explosive detonation velocities

    SciTech Connect

    Podsednik, Jason W.; Parks, Shawn Michael; Navarro, Rudolfo J.

    2012-07-01

    Single-mode fibers were cleverly embedded into fixtures holding nitromethane, and used in conjunction with a photonic Doppler velocimeter (PDV) to measure the associated detonation velocity. These measurements have aided us in our understanding of energetic materials and enhanced our diagnostic capabilities.

  10. Measurement of turbulent wind velocities using a rotating boom apparatus

    SciTech Connect

    Sandborn, V.A.; Connell, J.R.

    1984-04-01

    The present report covers both the development of a rotating-boom facility and the evaluation of the spectral energy of the turbulence measured relative to the rotating boom. The rotating boom is composed of a helicopter blade driven through a pulley speed reducer by a variable speed motor. The boom is mounted on a semiportable tower that can be raised to provide various ratios of hub height to rotor diameter. The boom can be mounted to rotate in either the vertical or horizontal plane. Probes that measure the three components of turbulence can be mounted at any location along the radius of the boom. Special hot-film sensors measured two components of the turbulence at a point directly in front of the rotating blade. By using the probe rotated 90/sup 0/ about its axis, the third turbulent velocity component was measured. Evaluation of the spectral energy distributions for the three components of velocity indicates a large concentration of energy at the rotational frequency. At frequencies slightly below the rotational frequency, the spectral energy is greatly reduced over that measured for the nonrotating case measurements. Peaks in the energy at frequencies that are multiples of the rotation frequency were also observed. We conclude that the rotating boom apparatus is suitable and ready to be used in experiments for developing and testing sensors for rotational measurement of wind velocity from wind turbine rotors. It also can be used to accurately measure turbulent wind for testing theories of rotationally sampled wind velocity.

  11. Laboratory Measurements of Velocity and Attenuation in Sediments

    SciTech Connect

    Zimmer, M A; Berge, P A; Bonner, B P; Prasad, M

    2004-06-08

    Laboratory measurements are required to establish relationships between the physical properties of unconsolidated sediments and P- and S-wave propagation through them. Previous work has either focused on measurements of compressional wave properties at depths greater than 500 m for oil industry applications or on measurements of dynamic shear properties at pressures corresponding to depths of less than 50 m for geotechnical applications. Therefore, the effects of lithology, fluid saturation, and compaction on impedance and P- and S-wave velocities of shallow soils are largely unknown. We describe two state-of-the-art laboratory experiments. One setup allows us to measure ultrasonic P-wave velocities at very low pressures in unconsolidated sediments (up to 0.1 MPa). The other experiment allows P- and S-wave velocity measurements at low to medium pressures (up to 20 MPa). We summarize the main velocity and attenuation results on sands and sand - clay mixtures under partially saturated and fully saturated conditions in two ranges of pressures (0 - 0.1 MPa and 0.1 - 20 MPa) representative of the top few meters and the top 1 km, respectively. Under hydrostatic pressures of 0.1 to 20 MPa, our measurements demonstrate a P- and S-wave velocity-dependence in dry sands around a fourth root (0.23 -0.26) with the pressure dependence for S-waves being slightly lower. The P- velocity-dependence in wet sands lies around 0.4. The Vp-Vs and the Qp-Qs ratios together can be useful tools to distinguish between different lithologies and between pressure and saturation effects. These experimental velocities at the frequency of measurement (200 kHz) are slightly higher that Gassmann's static result. For low pressures under uniaxial stress, Vp and Vs were a few hundred meters per second with velocities showing a strong dependence on packing, clay content, and microstructure. We provide a typical shallow soil scenario in a clean sand environment and reconstruct the velocity profile of

  12. Simulated O VI Doppler dimming measurements of coronal outflow velocities

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard; Gardner, L. D.; Kohl, John L.

    1992-01-01

    The possibility of determining O(5+) outflow velocities by using a Doppler dimming analysis of the resonantly scattered intensities of O VI lambda 1031.9 and lambda 1037.6 is addressed. The technique is sensitive to outflow velocities, W, in the range W greater than 30 and less than 250 km/s and can be used for probing regions of the inner solar corona, where significant coronal heating and solar wind acceleration may be occurring. These velocity measurements, when combined with measurements of other plasma parameters (temperatures and densities of ions and electrons) can be used to estimate the energy and mass flux of O(5+). In particular, it may be possible to locate where the flow changes from subsonic to supersonic and to identify source regions for the high and low speed solar wind. The velocity diagnostic technique is discussed with emphasis placed on the requirements needed for accurate outflow velocity determinations. Model determinations of outflow velocities based on simulated Doppler observations are presented.

  13. Normalized velocity profiles of field-measured turbidity currents

    USGS Publications Warehouse

    Xu, Jingping

    2010-01-01

    Multiple turbidity currents were recorded in two submarine canyons with maximum speed as high as 280 cm/s. For each individual turbidity current measured at a fixed station, its depth-averaged velocity typically decreased over time while its thickness increased. Some turbidity currents gained in speed as they traveled downcanyon, suggesting a possible self-accelerating process. The measured velocity profiles, first in this high resolution, allowed normalizations with various schemes. Empirical functions, obtained from laboratory experiments whose spatial and time scales are two to three orders of magnitude smaller, were found to represent the field data fairly well. The best similarity collapse of the velocity profiles was achieved when the streamwise velocity and the elevation were normalized respectively by the depth-averaged velocity and the turbidity current thickness. This normalization scheme can be generalized to an empirical function Y = exp(–αXβ) for the jet region above the velocity maximum. Confirming theoretical arguments and laboratory results of other studies, the field turbidity currents are Froude-supercritical.

  14. Sound field separation with sound pressure and particle velocity measurements.

    PubMed

    Fernandez-Grande, Efren; Jacobsen, Finn; Leclère, Quentin

    2012-12-01

    In conventional near-field acoustic holography (NAH) it is not possible to distinguish between sound from the two sides of the array, thus, it is a requirement that all the sources are confined to only one side and radiate into a free field. When this requirement cannot be fulfilled, sound field separation techniques make it possible to distinguish between outgoing and incoming waves from the two sides, and thus NAH can be applied. In this paper, a separation method based on the measurement of the particle velocity in two layers and another method based on the measurement of the pressure and the velocity in a single layer are proposed. The two methods use an equivalent source formulation with separate transfer matrices for the outgoing and incoming waves, so that the sound from the two sides of the array can be modeled independently. A weighting scheme is proposed to account for the distance between the equivalent sources and measurement surfaces and for the difference in magnitude between pressure and velocity. Experimental and numerical studies have been conducted to examine the methods. The double layer velocity method seems to be more robust to noise and flanking sound than the combined pressure-velocity method, although it requires an additional measurement surface. On the whole, the separation methods can be useful when the disturbance of the incoming field is significant. Otherwise the direct reconstruction is more accurate and straightforward.

  15. Absolute blood velocity measured with a modified fundus camera

    NASA Astrophysics Data System (ADS)

    Duncan, Donald D.; Lemaillet, Paul; Ibrahim, Mohamed; Nguyen, Quan Dong; Hiller, Matthias; Ramella-Roman, Jessica

    2010-09-01

    We present a new method for the quantitative estimation of blood flow velocity, based on the use of the Radon transform. The specific application is for measurement of blood flow velocity in the retina. Our modified fundus camera uses illumination from a green LED and captures imagery with a high-speed CCD camera. The basic theory is presented, and typical results are shown for an in vitro flow model using blood in a capillary tube. Subsequently, representative results are shown for representative fundus imagery. This approach provides absolute velocity and flow direction along the vessel centerline or any lateral displacement therefrom. We also provide an error analysis allowing estimation of confidence intervals for the estimated velocity.

  16. Near bottom velocity measurements in San Francisco Bay, California

    USGS Publications Warehouse

    Gartner, Jeffrey W.; Cheng, Ralph T.; ,

    1996-01-01

    The ability to accurately measure long-term time-series of tidal currents in bays and estuaries is critical in estuarine hydrodynamic studies. Accurate measurements of tidal currents near the air-water interface and in the bottom boundary layer remain difficult in spite of the significant advances in technology for measuring tidal currents which have been achieved in recent years. One of the objectives of this study is to demonstrate that turbulent mean velocity distribution within the bottom boundary layer can be determined accurately by using a broad-band acoustic Doppler current profiler (BB-ADCP). A suite of instruments, including two BB-ADCPs and four electromagnetic (EM) current meters was deployed in San Francisco Bay, California in an investigation of resuspension and transport of sediment during March 1995. The velocity measurements obtained in the bottom boundary layer by BB-ADCP were highly coherent (r2>0.94) with the velocity measurements obtained by EM current meters. During early March 1995, both BB-ADCPs and EM current meters recorded a very unusual flow event. Agreement among independent measurements by these instruments in describing such an atypical hydrodynamic occurrence further validates the velocity measurements obtained by BB-ADCP in the bottom boundary layer.

  17. Sensors for Using Times of Flight to Measure Flow Velocities

    NASA Technical Reports Server (NTRS)

    Fralick, Gutave; Wrbanek, John D.; Hwang, Danny; Turso, James

    2006-01-01

    Thin-film sensors for measuring flow velocities in terms of times of flight are undergoing development. These sensors are very small and can be mounted flush with surfaces of airfoils, ducts, and other objects along which one might need to measure flows. Alternatively or in addition, these sensors can be mounted on small struts protruding from such surfaces for acquiring velocity measurements at various distances from the surfaces for the purpose of obtaining boundary-layer flow-velocity profiles. These sensors are related to, but not the same as, hot-wire anemometers. Each sensor includes a thin-film, electrically conductive loop, along which an electric current is made to flow to heat the loop to a temperature above that of the surrounding fluid. Instantaneous voltage fluctuations in segments of the loop are measured by means of electrical taps placed at intervals along the loop. These voltage fluctuations are caused by local fluctuations in electrical resistance that are, in turn, caused by local temperature fluctuations that are, in turn, caused by fluctuations in flow-induced cooling and, hence, in flow velocity. The differential voltage as a function of time, measured at each pair of taps, is subjected to cross-correlation processing with the corresponding quantities measured at other pairs of taps at different locations on the loop. The cross-correlations yield the times taken by elements of fluid to travel between the pairs of taps. Then the component of velocity along the line between any two pairs of taps is calculated simply as the distance between the pairs of taps divided by the travel time. Unlike in the case of hot-wire anemometers, there is no need to obtain calibration data on voltage fluctuations versus velocity fluctuations because, at least in principle, the correlation times are independent of the calibration data.

  18. Velocity measurements by laser resonance fluorescence. [single atom diffusional motion

    NASA Technical Reports Server (NTRS)

    She, C. Y.; Fairbank, W. M., Jr.

    1980-01-01

    The photonburst correlation method was used to detect single atoms in a buffer gas. Real time flow velocity measurements with laser induced resonance fluorescence from single or multiple atoms was demonstrated and this method was investigated as a tool for wind tunnel flow measurement. Investigations show that single atoms and their real time diffusional motion on a buffer gas can be measured by resonance fluorescence. By averaging over many atoms, flow velocities up to 88 m/s were measured in a time of 0.5 sec. It is expected that higher flow speeds can be measured and that the measurement time can be reduced by a factor of 10 or more by careful experimental design. The method is clearly not ready for incorporation in high speed wind tunnels because it is not yet known whether the stray light level will be higher or lower, and it is not known what detection efficiency can be obtained in a wind tunnel situation.

  19. Optic-microwave mixing velocimeter for superhigh velocity measurement

    SciTech Connect

    Weng Jidong; Wang Xiang; Tao Tianjiong; Liu Cangli; Tan Hua

    2011-12-15

    The phenomenon that a light beam reflected off a moving object experiences a Doppler shift in its frequency underlies practical interferometric techniques for remote velocity measurements, such as velocity interferometer system for any reflector (VISAR), displacement interferometer system for any reflector (DISAR), and photonic Doppler velocimetry (PDV). While VISAR velocimeters are often bewildered by the fringe loss upon high-acceleration dynamic process diagnosis, the optic-fiber velocimeters such as DISAR and PDV, on the other hand, are puzzled by high velocity measurement over 10 km/s, due to the demand for the high bandwidth digitizer. Here, we describe a new optic-microwave mixing velocimeter (OMV) for super-high velocity measurements. By using currently available commercial microwave products, we have constructed a simple, compact, and reliable OMV device, and have successfully obtained, with a digitizer of bandwidth 6 GH only, the precise velocity history of an aluminum flyer plate being accelerated up to 11.2 km/s in a three stage gas-gun experiment.

  20. Brachial vs. central systolic pressure and pulse wave transmission indicators: a critical analysis.

    PubMed

    Izzo, Joseph L

    2014-12-01

    This critique is intended to provide background for the reader to evaluate the relative clinical utilities of brachial cuff systolic blood pressure (SBP) and its derivatives, including pulse pressure, central systolic pressure, central augmentation index (AI), and pulse pressure amplification (PPA). The critical question is whether the newer indicators add sufficient information to justify replacing or augmenting brachial cuff blood pressure (BP) data in research and patient care. Historical context, pathophysiology of variations in pulse wave transmission and reflection, issues related to measurement and model errors, statistical limitations, and clinical correlations are presented, along with new comparative data. Based on this overview, there is no compelling scientific or practical reason to replace cuff SBP with any of the newer indicators in the vast majority of clinical situations. Supplemental value for central SBP may exist in defining patients with exaggerated PPA ("spurious systolic hypertension"), managing cardiac and aortic diseases, and in studies of cardiovascular drugs, but there are no current standards for these possibilities.

  1. Bubbly flow velocity measurements near a heated cylindrical conductor

    SciTech Connect

    Canaan, R.E.; Hassan, Y.A. )

    1990-01-01

    The objective of this study is to apply recent advances and improvements in the digital pulsed laser velocimetry (DPLV) technique to the analysis of two-phase bubbly flow about a cylindrical conductor emitting a constant heat flux within a transparent rectangular enclosure. Pulsed laser velocimetry is a rapidly advancing fluid flow visualization technique that determines full-field instantaneous velocity vectors of a quantitative nature such that the flow field remains undisturbed by the measurement. The DPLV method offers several significant advantages over more traditional fluid velocity measurement techniques such as hot wire/film anemometry and laser Doppler anemometry because reliable instantaneous velocity data may be acquired over substantial flow areas in a single experiment.

  2. Rayleigh Scattering Diagnostic for Dynamic Measurement of Velocity and Temperature

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, J.

    2001-01-01

    A new technique for measuring dynamic gas velocity and temperature is described. The technique is based on molecular Rayleigh scattering of laser light, so no seeding of the flow is necessary. The Rayleigh scattered light is filtered with a fixed cavity, planar mirror Fabry-Perot interferometer. A minimum number of photodetectors were used in order to allow the high data acquisition rate needed for dynamic measurements. One photomultiplier tube (PMT) was used to measure the total Rayleigh scattering, which is proportional to the gas density. Two additional PMTs were used to detect light that passes through two apertures in a mask located in the interferometer fringe plane. An uncertainty analysis was used to select the optimum aperture parameters and to predict the measurement uncertainty due to photon shot-noise. Results of an experiment to measure the velocity of a subsonic free jet are presented.

  3. Adaptive interferometric velocity measurements using a laser guide star

    NASA Astrophysics Data System (ADS)

    Czarske, J.; Radner, H.; Büttner, L.

    2015-07-01

    We have harnessed the power of programmable photonics devices for an interferometric measurement technique. Laser interferometers are widely used for flow velocity measurements, since they offer high temporal and spatial resolutions. However, often optical wavefront distortions deteriorate the measurement properties. In principle, adaptive optics enables the correction of these disturbances. One challenge is to generate a suitable reference signal for the closed loop operation of the adaptive optics. An adaptive Mach Zehnder interferometer is presented to measure through a dynamic liquid-gas phase boundary, which can lead to a misalignment of the interfering laser beams. In order to generate the reference signal for the closed loop control, the Fresnel reflex of the phase boundary is used as Laser Guide Star (LGS) for the first time to the best of the authors' knowledge. The concept is related to the generation of artificial stars in astronomy, where the light transmitted by the atmosphere is evaluated. However, the adaptive interferometric flow velocity measurements at real world experiments require a different concept, since only the reflected light can be evaluated. The used LGS allows to measure the wavefront distortions induced by the dynamic phase boundary. Two biaxial electromagnetically driven steering mirrors are employed to correct the wavefront distortions. This opens up the possibility for accurate flow measurements through a dynamic phase boundary using only one optical access. Our work represents a paradigm shift in interferometric velocity measurement techniques from using static to dynamic optical elements.

  4. Results on fibre scrambling for high accuracy radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Avila, Gerardo; Singh, Paul; Chazelas, Bruno

    2010-07-01

    We present in this paper experimental data on fibres and scramblers to increase the photometrical stability of the spectrograph PSF. We have used round, square, octagonal fibres and beam homogenizers. This study is aimed to enhance the accuracy measurements of the radial velocities for ESO ESPRESSO (VLT) and CODEX (E-ELT) instruments.

  5. Precise Measurement of Drift Velocities in Active-Target Detectors

    NASA Astrophysics Data System (ADS)

    Jensen, Louis

    2016-09-01

    Nuclear experiments with radioactive beams are needed to improve our understanding of nuclei structure far from stability. Radioactive beams typically have low beam rates, but active-target detectors can compensate for these low beam rates. In active-target detectors that are also Time-Projection Chambers (TPC), ionized electrons drift through an electric fieldto a detection device to imagethe trajectory of charged-particle ionization tracks within the chamber's gas volume. The measurement of the ionized electrons' drift velocity is crucial for the accurate imaging of these tracks. In order to measure this drift velocity, we will use a UV laser and photo-sensitive foil in a the ND-Cubedetector we are developing, periodically releasingelectrons from the foil at a known timesand a known distance from the electron detector, thereby precisely measuring the drift velocity in situ. We have surveyed several materials to find a material that will work well with typical solid-state UV lasers on the market. We plan to determine the best material and thickness of the foil to maximize the number of photoelectrons. The precision that will be afforded by this measurement of the drift velocity will allow us to eliminate a source of systematic uncertainty.

  6. FPGA-based design and implementation of arterial pulse wave generator using piecewise Gaussian-cosine fitting.

    PubMed

    Wang, Lu; Xu, Lisheng; Zhao, Dazhe; Yao, Yang; Song, Dan

    2015-04-01

    Because arterial pulse waves contain vital information related to the condition of the cardiovascular system, considerable attention has been devoted to the study of pulse waves in recent years. Accurate acquisition is essential to investigate arterial pulse waves. However, at the stage of developing equipment for acquiring and analyzing arterial pulse waves, specific pulse signals may be unavailable for debugging and evaluating the system under development. To produce test signals that reflect specific physiological conditions, in this paper, an arterial pulse wave generator has been designed and implemented using a field programmable gate array (FPGA), which can produce the desired pulse waves according to the feature points set by users. To reconstruct a periodic pulse wave from the given feature points, a method known as piecewise Gaussian-cosine fitting is also proposed in this paper. Using a test database that contains four types of typical pulse waves with each type containing 25 pulse wave signals, the maximum residual error of each sampling point of the fitted pulse wave in comparison with the real pulse wave is within 8%. In addition, the function for adding baseline drift and three types of noises is integrated into the developed system because the baseline occasionally wanders, and noise needs to be added for testing the performance of the designed circuits and the analysis algorithms. The proposed arterial pulse wave generator can be considered as a special signal generator with a simple structure, low cost and compact size, which can also provide flexible solutions for many other related research purposes.

  7. Evaluation of mean velocity and turbulence measurements with ADCPs

    USGS Publications Warehouse

    Nystrom, E.A.; Rehmann, C.R.; Oberg, K.A.

    2007-01-01

    To test the ability of acoustic Doppler current profilers (ADCPs) to measure turbulence, profiles measured with two pulse-to-pulse coherent ADCPs in a laboratory flume were compared to profiles measured with an acoustic Doppler velocimeter, and time series measured in the acoustic beam of the ADCPs were examined. A four-beam ADCP was used at a downstream station, while a three-beam ADCP was used at a downstream station and an upstream station. At the downstream station, where the turbulence intensity was low, both ADCPs reproduced the mean velocity profile well away from the flume boundaries; errors near the boundaries were due to transducer ringing, flow disturbance, and sidelobe interference. At the upstream station, where the turbulence intensity was higher, errors in the mean velocity were large. The four-beam ADCP measured the Reynolds stress profile accurately away from the bottom boundary, and these measurements can be used to estimate shear velocity. Estimates of Reynolds stress with a three-beam ADCP and turbulent kinetic energy with both ADCPs cannot be computed without further assumptions, and they are affected by flow inhomogeneity. Neither ADCP measured integral time scales to within 60%. ?? 2007 ASCE.

  8. Improved Measurement of Ejection Velocities From Craters Formed in Sand

    NASA Technical Reports Server (NTRS)

    Cintala, Mark J.; Byers, Terry; Cardenas, Francisco; Montes, Roland; Potter, Elliot E.

    2014-01-01

    A typical impact crater is formed by two major processes: compression of the target (essentially equivalent to a footprint in soil) and ejection of material. The Ejection-Velocity Measurement System (EVMS) in the Experimental Impact Laboratory has been used to study ejection velocities from impact craters formed in sand since the late 1990s. The original system used an early-generation Charge-Coupled Device (CCD) camera; custom-written software; and a complex, multicomponent optical system to direct laser light for illumination. Unfortunately, the electronic equipment was overtaken by age, and the software became obsolete in light of improved computer hardware.

  9. An inexpensive instrument for measuring wave exposure and water velocity

    USGS Publications Warehouse

    Figurski, J.D.; Malone, D.; Lacy, J.R.; Denny, M.

    2011-01-01

    Ocean waves drive a wide variety of nearshore physical processes, structuring entire ecosystems through their direct and indirect effects on the settlement, behavior, and survivorship of marine organisms. However, wave exposure remains difficult and expensive to measure. Here, we report on an inexpensive and easily constructed instrument for measuring wave-induced water velocities. The underwater relative swell kinetics instrument (URSKI) is a subsurface float tethered by a short (<1 m) line to the seafloor. Contained within the float is an accelerometer that records the tilt of the float in response to passing waves. During two field trials totaling 358 h, we confirmed the accuracy and precision of URSKI measurements through comparison to velocities measured by an in situ acoustic Doppler velocimeter and those predicted by a standard swell model, and we evaluated how the dimensions of the devices, its buoyancy, and sampling frequency can be modified for use in a variety of environments.

  10. Inter-laboratory comparison of wave velocity measures.

    USGS Publications Warehouse

    Waite, William F.; Santamarina, J.C.; Rydzy, M.; Chong, S.H.; Grozic, J.L.H.; Hester, K.; Howard, J.; Kneafsey, T.J.; Lee, J.Y.; Nakagawa, S.; Priest, J.; Reese, E.; Koh, H.; Sloan, E.D.; Sultaniya, A.

    2011-01-01

     This paper presents an eight-laboratory comparison of compressional and shear wave velocities measured in F110 Ottawa sand. The study was run to quantify the physical property variations one should expect in heterogeneous, multiphase porous materials by separately quantifying the variability inherent in the measurement techniques themselves. Comparative tests were run in which the sand was dry, water-saturated, partially water-saturated, partially ice-saturated and partially hydrate-saturated. Each test illustrates a collection of effects that can be classified as inducing either specimen-based or measurement-based variability. The most significant variability is due to void ratio variations between samples. Heterogeneous pore-fill distributions and differences in measurement techniques also contribute to the observed variability, underscoring the need to provide detailed sample preparation and system calibration information when reporting wave velocities in porous media. 

  11. Pulse Wave Amplitude Drops during Sleep are Reliable Surrogate Markers of Changes in Cortical Activity

    PubMed Central

    Delessert, Alexandre; Espa, Fabrice; Rossetti, Andrea; Lavigne, Gilles; Tafti, Mehdi; Heinzer, Raphael

    2010-01-01

    Background: During sleep, sudden drops in pulse wave amplitude (PWA) measured by pulse oximetry are commonly associated with simultaneous arousals and are thought to result from autonomic vasoconstriction. In the present study, we determine whether PWA drops were associated with changes in cortical activity as determined by EEG spectral analysis. Methods: A 20% decrease in PWA was chosen as a minimum for a drop. A total of 1085 PWA drops from 10 consecutive sleep recordings were analyzed. EEG spectral analysis was performed over 5 consecutive epochs of 5 seconds: 2 before, 1 during, and 2 after the PWA drop. EEG spectral analysis was performed over delta, theta, alpha, sigma, and beta frequency bands. Within each frequency band, power density was compared across the five 5-sec epochs. Presence or absence of visually scored EEG arousals were adjudicated by an investigator blinded to the PWA signal and considered associated with PWA drop if concomitant. Results: A significant increase in EEG power density in all EEG frequency bands was found during PWA drops (P < 0.001) compared to before and after drop. Even in the absence of visually scored arousals, PWA drops were associated with a significant increase in EEG power density (P < 0.001) in most frequency bands. Conclusions: Drops in PWA are associated with a significant increase in EEG power density, suggesting that these events can be used as a surrogate for changes in cortical activity during sleep. This approach may prove of value in scoring respiratory events on limited-channel (type III) portable monitors. Citation: Delessert A; Espa F; Rossetti A; Lavigne G; Tafti M; Heinzer R. Pulse wave amplitude drops during sleep are reliable surrogate markers of changes in cortical activity. SLEEP 2010;33(12):1687-1692. PMID:21120131

  12. Velocity measurements in the plume of an arcjet engine

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.; Deininger, W. D.

    1987-01-01

    A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail.

  13. Velocity measurements in the plume of an arcjet engine

    SciTech Connect

    Pivirotto, T.J.; Deininger, W.D.

    1987-05-01

    A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail. 19 references.

  14. Visualization of turbulent flows with simultaneous velocity and vorticity measurements

    NASA Astrophysics Data System (ADS)

    Ong, Lawrence

    1992-09-01

    An experimental study of the turbulent boundary layer at Re(sub theta) approx. equals 1070 was conducted. This study combines velocity and vorticity measurements using a nine-sensor hot-wire probe with simultaneously obtained flow visualization images. Detailed measurements within the boundary layer with and without smoke marking of the wall layer fluid were performed at various distances from the wall, ranging from approximately y(+) approx. equals 14 to y(+) approx. equals 156, and at three axial locations downstream from the smoke injection slot. The mean statistical properties of the fluctuating velocity and vorticity components agree well with previous experimental and numerically simulated data. These boundary layer measurements were used in a joint probability analysis of the various instantaneous velocity, velocity gradient and vorticity correlations that appear in the vorticity and enstrophy transport equations. Substantial evidence supporting postulated inclined vortex models was found. Conditional analysis based on the detection of strong Reynolds stress and enstrophy events was carried out. The combined visual and hot-wire data provide evidence showing that these smoke marked regions in the flow field, which indicate vertical mass flux, are also regions of high vertical momentum flux.

  15. Velocity measurement of flow over random soft porous media

    NASA Astrophysics Data System (ADS)

    Selkirk, Isreal; Mirbod, Parisa

    2016-11-01

    The aim of this work is to experimentally examine the flow over random soft porous media in a three-dimensional channel. Various combination of fibrous material and the morphology of the fibers were chosen to achieve void volume fraction (ɛ) ranging from 0.4 to 0.7. Care has been taken to keep the Reynolds number low so that the flow was laminar. The channel height was constant, however the thickness of the fibrous media was varied to achieve different filling fraction. Before starting the tests in the duct with fiber arrays, a series of tests in an empty duct (i.e., without fibers) conducted to validate the experimental measurements. We also discussed the error and uncertainty sources in the experiments and described the techniques to improve their impact. We studied detailed velocity measurements of the flow over fibrous material inside a rectangular duct using a planar particle image velocimetry (PIV) technique. Using these measurements, we determined the values of the slip velocity at the interface between the fibrous media and the flow. It was found that values of the slip velocity normalized by the maximum velocity in the flow depend on solid volume fraction, pore spaces, and fraction of channel filled by the fiber layers.

  16. High resolved velocity measurements using Laser Cantilever Anemometry

    NASA Astrophysics Data System (ADS)

    Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim

    2016-11-01

    We have developed a new anemometer, namely the 2d-LCA (2d-Laser-Cantilever-Anemometer), that is capable of performing high resolved velocity measurements in fluids. The anemometer uses a micostructured cantilever made of silicon as a sensing element. The specific shape and the small dimensions (about 150µm) of the cantilever allow for precise measurements of two velocity component at a temporal resolution of about 150kHz. The angular acceptance range is 180° in total. The 2d-LCA is a simple to use alternative to x-wires and can be used in many areas of operation including measurements in liquids or in particle-laden flows. Unlike hot-wires, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high-speed flows. In the recent past new cantilever designs were implemented with the goal to further improve the angular resolution and increase the stability. In addition, we have designed more robust cantilevers for measurements in rough environments such as offshore areas. Successful comparative measurements with hot-wires have been carried out in order to assess the performance of the 2d-LCA.

  17. Nonintrusive Temperature and Velocity Measurements in a Hypersonic Nozzle Flow

    NASA Technical Reports Server (NTRS)

    OByrne, S.; Danehy, P. M.; Houwing, A. F. P.

    2002-01-01

    Distributions of nitric oxide vibrational temperature, rotational temperature and velocity have been measured in the hypersonic freestream at the exit of a conical nozzle, using planar laser-induced fluorescence. Particular attention has been devoted to reducing the major sources of systematic error that can affect fluorescence tempera- ture measurements, including beam attenuation, transition saturation effects, laser mode fluctuations and transition choice. Visualization experiments have been performed to improve the uniformity of the nozzle flow. Comparisons of measured quantities with a simple one-dimensional computation are made, showing good agreement between measurements and theory given the uncertainty of the nozzle reservoir conditions and the vibrational relaxation rate.

  18. Nonintrusive measurement of temperature and velocity in free convection

    NASA Astrophysics Data System (ADS)

    Koch, Stefan

    1993-12-01

    A technique for simultaneously measuring the temperature and velocity in liquid flows is developed. Small droplets of thermochromic liquid crystals, suspended in the liquid, serve as tracer particles. The color of the light reflected by the crystals yields the temperature, while their velocity was measured via PIV (particle image velocimetry) from their displacement in a time interval. The measurement and evaluation are performed by digital image processing of color video images. By shifting the plane of observation, a three dimensional flow field can be scanned. The technique was applied to the convective flow in a box with two differentially heated opposite side walls. Two cases were considered: the influence of the thermal boundary conditions on a stationary flow and the onset of convection in a fluid initially at rest after imposing a temperature difference on the heated walls. The results were compared with numerical simulations.

  19. Dwarf galaxies in the Coma cluster - I. Velocity dispersion measurements

    NASA Astrophysics Data System (ADS)

    Kourkchi, E.; Khosroshahi, H. G.; Carter, D.; Karick, A. M.; Mármol-Queraltó, E.; Chiboucas, K.; Tully, R. B.; Mobasher, B.; Guzmán, R.; Matković, A.; Gruel, N.

    2012-03-01

    We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for which the velocity dispersion can be reliably measured, 26 of which were studied for the first time. The magnitude range of our sample is -21 < MR < -15 mag. This paper (Paper I) focuses on the measurement of the velocity dispersion and their error estimates. The measurements were performed using penalized pixel fitting (PPXF) and using the calcium triplet absorption lines. We use Monte Carlo bootstrapping to study various sources of uncertainty in our measurements, namely statistical uncertainty, template mismatch and other systematics. We find that the main source of uncertainty is the template mismatch effect which is reduced by using templates with a range of spectral types. Combining our measurements with those from the literature, we study the Faber-Jackson relation (L∝σα) and find that the slope of the relation is α= 1.99 ± 0.14 for galaxies brighter than MR≃-16 mag. A comprehensive analysis of the results combined with the photometric properties of these galaxies is reported in Paper II.

  20. Research on the photoelectric measuring method of warhead fragment velocity

    NASA Astrophysics Data System (ADS)

    Liu, Ji; Yu, Lixia; Zhang, Bin; Liu, Xiaoyan

    2016-09-01

    The velocity of warhead fragment is the key criteria to determine its mutilation efficiency. But owing to the small size, larger quantity, irregular shape, high speed, arbitrary direction, large dispersion of warhead fragment and adverse environment, the test of fragment velocity parameter is very difficult. The paper designed an optoelectronic system to measure the average velocity of warhead fragments accurately. The apparatus included two parallel laser screens spaced apart at a known fixed distance for providing time measurement between start and stop signals. The large effective screen area was composed of laser source, retro-reflector and large area photo-diode. Whenever a moving fragment interrupted two optical screens, the system would generate a target signal. Due to partial obscuration of the incident energy and the poor test condition of the explosion, fragment target signal is easily disturbed. Therefore, fragments signal processing technology has become a key technology of the system. The noise of signal was reduced by employing wavelet decomposition and reconstruction. The time of fragment passing though the target was obtained by adopting peak detection algorithm. Based on the method of search peak in different width scale and waveform trend by using optima wavelet, the problem of rolling waveform was solved. Lots of fragments experiments of the different types of the warheads were conducted. Experimental results show that: warhead fragments capture rate of system is better than 98%, which can give velocity of each fragment in the density of less than 20 pieces per m2.

  1. 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.

  2. 3-D Velocity Measurement of Natural Convection Using Image Processing

    NASA Astrophysics Data System (ADS)

    Shinoki, Masatoshi; Ozawa, Mamoru; Okada, Toshifumi; Kimura, Ichiro

    This paper describes quantitative three-dimensional measurement method for flow field of a rotating Rayleigh-Benard convection in a cylindrical cell heated below and cooled above. A correlation method for two-dimensional measurement was well advanced to a spatio-temporal correlation method. Erroneous vectors, often appeared in the correlation method, was successfully removed using Hopfield neural network. As a result, calculated 3-D velocity vector distribution well corresponded to the observed temperature distribution. Consequently, the simultaneous three-dimensional measurement system for temperature and flow field was developed.

  3. Electric field measurements during the Condor critical velocity experiment

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.; Pfaff, R. F.; Haerendel, G.

    1986-01-01

    The instrumentation of the Condor critical velocity Ba experiment (Wescott et al., 1986) for the measurements of the energetic particles and the electric field associated with a Ba explosion is described. The Ba explosion created a complex electric field pulse detected in situ by a single-axis double electric-field probe on a separate spacecraft. The measurements provide evidence of several important links in the critical-velocity chain, and are consistent with two hypotheses. The first hypothesis involves the creation of large polarization electric field due to charge separation; the second hypothesis implies a polarization of the beam by currents flowing across it. The chain of physical processes inferred from the observations is in agreement with most theories for the Alfven process.

  4. Measuring velocity and temperature profile sectional pipeline behind confuser

    NASA Astrophysics Data System (ADS)

    Siažik, Ján; Malcho, Milan; Lenhard, Richard; Novomestský, Marcel

    2016-06-01

    The article deals with the measuring of temperature and velocity profile in area behind confuser in real made scale model of bypass. For proper operation of the equipment it is necessary to know the actual flow in the pipe. Bypasses have wide application and can be also associated with devices for heat recovery, heat exchangers different designs in which may be used in certain circumstances. In the present case, the heat that would otherwise has not been used is used for heating of insulators, and heating the air in the spray-dryer. The measuring principle was verify how the above-mentioned temperature and velocity profile decomposition above confuser on real made scale model.

  5. High-speed velocity measurements on an EFI-system

    NASA Astrophysics Data System (ADS)

    Prinse, W. C.; van't Hof, P. G.; Cheng, L. K.; Scholtes, J. H. G.

    2007-01-01

    For the development of an Exploding Foil Initiator for Insensitive Munitions applications the following topics are of interest: the electrical circuit, the exploding foil, the velocity of the flyer, the driver explosive, the secondary flyer and the acceptor explosive. Several parameters of the EFI have influences on the velocity of the flyer. To investigate these parameters a Fabry-Perot Velocity Interferometer System (F-PVIS) has been used. The light to and from the flyer is transported by a multimode fibre terminated with a GRIN-lens. By this method the velocity of very tiny objects (0.1 mm), can be measured. The velocity of flyer can be recorded with nanosecond resolution, depending on the Fabry-Perot etalon and the streak camera. With this equipment the influence of the dimensions of the exploding foil and the flyer on the velocity and the acceleration of the flyer are investigated. Also the integrity of the flyer during flight can be analyzed. To characterize the explosive material, to be used as driver explosive in EFI's, the initiation behaviour of the explosive has been investigated by taking pictures of the explosion with a high speed framing and streak camera. From these pictures the initiation distance and the detonation behaviour of the explosive has been analyzed. Normally, the driver explosive initiates the acceptor explosive (booster) by direct contact. This booster explosive is embedded in the main charge of the munitions. The combination of initiator, booster explosive and main charge explosive is called the detonation train. In this research the possibility of initiation of the booster by an intermediate flyer is investigated. This secondary flyer can be made of different materials, like aluminium, steel and polyester with different sizes. With the aid of the F-PVIS the acceleration of the secondary flyer is investigated. This reveals the influence of the thickness and density of the flyer on the acceleration and final velocity. Under certain

  6. Estimation of Arterial Stiffness by Time-Frequency Analysis of Pulse Wave

    NASA Astrophysics Data System (ADS)

    Saito, Masashi; Yamamoto, Yuya; Shibayama, Yuka; Matsukawa, Mami; Watanabe, Yoshiaki; Furuya, Mio; Asada, Takaaki

    2011-07-01

    Evaluation of a pulse wave is effective for the early diagnosis of arteriosclerosis because the pulse wave contains the reflected wave that is the age- and stiffness-dependent component. In this study, we attempted to extract the parameter reflecting the component by pulse wave analysis using continuous wavelet transform. The Morlet wavelet was used as the mother wavelet. We then investigated the relationship between the parameter and the reflected wave that was extracted from the pulse wave by our previously reported separation technique. Consequently, the result of wavelet transform of the differentiated pulse waveform changed markedly owing to age and had medium correlation with the peak of the reflected wave (R=0.68).

  7. Ventricular septal defect after myocardial infarction: assessment by cross sectional echocardiography with pulsed wave Doppler scanning.

    PubMed Central

    MacLeod, D; Fananapazir, L; de Bono, D; Bloomfield, P

    1987-01-01

    Eight patients who developed a ventricular septal defect after myocardial infarction were assessed by cross sectional echocardiography and pulsed wave Doppler scanning. Cross sectional echocardiography visualised the defect in four patients and gave an accurate assessment of global and regional left ventricular function in all eight. In all patients pulsed wave Doppler scanning detected turbulent flow at the apex of the right ventricle or adjacent to a wall motion abnormality affecting the interventricular septum. Pulsed wave Doppler detected coexisting mitral regurgitation in one patient and tricuspid regurgitation in another two. In all patients a left to right shunt was confirmed by oximetry and the location of the defect was identified by angiography or at operation or necropsy. Cross sectional echocardiography in combination with pulsed wave Doppler scanning is useful in the rapid bedside evaluation of patients with ventricular septal defect after myocardial infarction. Images Fig PMID:3663420

  8. Uncertainty quantification of inflow boundary condition and proximal arterial stiffness-coupled effect on pulse wave propagation in a vascular network.

    PubMed

    Brault, Antoine; Dumas, Laurent; Lucor, Didier

    2016-12-10

    This work aims at quantifying the effect of inherent uncertainties from cardiac output on the sensitivity of a human compliant arterial network response based on stochastic simulations of a reduced-order pulse wave propagation model. A simple pulsatile output form is used to reproduce the most relevant cardiac features with a minimum number of parameters associated with left ventricle dynamics. Another source of significant uncertainty is the spatial heterogeneity of the aortic compliance, which plays a key role in the propagation and damping of pulse waves generated at each cardiac cycle. A continuous representation of the aortic stiffness in the form of a generic random field of prescribed spatial correlation is then considered. Making use of a stochastic sparse pseudospectral method, we investigate the sensitivity of the pulse pressure and waves reflection magnitude over the arterial tree with respect to the different model uncertainties. Results indicate that uncertainties related to the shape and magnitude of the prescribed inlet flow in the proximal aorta can lead to potent variation of both the mean value and standard deviation of blood flow velocity and pressure dynamics due to the interaction of different wave propagation and reflection features. Lack of accurate knowledge in the stiffness properties of the aorta, resulting in uncertainty in the pulse wave velocity in that region, strongly modifies the statistical response, with a global increase in the variability of the quantities of interest and a spatial redistribution of the regions of higher sensitivity. These results will provide some guidance in clinical data acquisition and future coupling of arterial pulse wave propagation reduced-order model with more complex beating heart models.

  9. Thermodynamic properties of nitrogen gas from sound velocity measurements

    NASA Technical Reports Server (NTRS)

    Younglove, B. A.

    1979-01-01

    Thermodynamic properties of nitrogen gas have been calculated from 80 K to 350 K and at pressures to 10 bar from sound velocity measurements and existing P-V-T data using multiproperty fitting techniques. These new data are intended to improve existing predictive capability of the equation of state in the low density region needed for use with the NASA-Langley National Transonics Facility.

  10. Radionuclide counting technique for measuring wind velocity and direction

    NASA Technical Reports Server (NTRS)

    Singh, J. J. (Inventor)

    1984-01-01

    An anemometer utilizing a radionuclide counting technique for measuring both the velocity and the direction of wind is described. A pendulum consisting of a wire and a ball with a source of radiation on the lower surface of the ball is positioned by the wind. Detectors and are located in a plane perpendicular to pendulum (no wind). The detectors are located on the circumferene of a circle and are equidistant from each other as well as the undisturbed (no wind) source ball position.

  11. Velocity measurements in a boundary layer with a density gradient

    SciTech Connect

    Neuwald, P.; Reichenbach, H.; Kuhl, A.L.

    1992-11-01

    A number of experiments were performed at the EMI shock tube facility on shock waves propagating in a stratified atmosphere with density gradient modelled by air layered above Freon (C Cl{sub 2} F{sub 2}). This report presents streamwise velocity data for the flow behind the shock front. Additional information from measurements of overpressure history and shadowgraphs of the flow will be presented in a future EMI-report.

  12. Arterial Stiffness and Pulse Wave Reflection Are Increased in Patients Suffering from Severe Periodontitis

    PubMed Central

    Jockel-Schneider, Yvonne; Harks, Inga; Haubitz, Imme; Fickl, Stefan; Eigenthaler, Martin; Schlagenhauf, Ulrich; Baulmann, Johannes

    2014-01-01

    Aim This single blind cross-sectional study compared the vascular health of subjects suffering from severe chronic periodontitis, severe aggressive periodontitis and periodontal healthy controls by evaluating pulse wave velocity (PWV), augmentation index (AIx) and pulse pressure amplification (PPA). Material and Methods In a total of 158 subjects, 92 suffering from severe periodontitis and 66 matched periodontal healthy controls, PWV, AIx, central and peripheral blood pressure were recorded using an oscillometric device (Arteriograph). Results Subjects suffering from severe chronic or aggressive periodontitis exhibited significantly higher PWV (p = 0.00004), higher AIx (p = 0.0049) and lower PPA (p = 0.028) than matched periodontal healthy controls. Conclusions The results of this study confirm the association between periodontal inflammation and increased cardiovascular risk shown by impaired vascular health in case of severe periodontitis. As impaired vascular health is a common finding in patients suffering from severe periodontal disease a concomitant routine cardiovascular evaluation may be advised. PMID:25084111

  13. Velocity Measurements of Thermoelectric Driven Flowing Liquid Lithium

    NASA Astrophysics Data System (ADS)

    Szott, Matthew; Xu, Wenyu; Fiflis, Peter; Haehnlein, Ian; Kapat, Aveek; Kalathiparambil, Kishor; Ruzic, David N.

    2014-10-01

    Liquid lithium has garnered additional attention as a PFC due to its several advantages over solid PFCs, including reduced erosion and thermal fatigue, increased heat transfer, higher device lifetime, and enhanced plasma performance due to the establishment of low recycling regimes at the wall. The Lithium Metal Infused Trenches concept (LiMIT) has demonstrated thermoelectric magnetohydrodynamic flow of liquid lithium through horizontal open-faced metal trenches with measured velocities varying from 3.7+/-0.5 cm/s in the 1.76 T field of HT-7 to 22+/-3 cm/s in the SLiDE facility at UIUC at 0.059 T. To demonstrate the versatility of the concept, a new LiMIT design using narrower trenches shows steady state, thermoelectric-driven flow at an arbitrary angle from horizontal. Velocity characteristics are measured and discussed. Based on this LiMIT concept, a new limiter design has been developed to be tested on the mid-plane of the EAST plasma. Preliminary modelling suggests lithium flow of 6 cm/s in this device. Additionally, recent testing at the Magnum-PSI facility has given encouraging results, and velocity measurements in relation to magnetic field strength and plasma flux are also presented.

  14. ELODIE: A spectrograph for accurate radial velocity measurements.

    NASA Astrophysics Data System (ADS)

    Baranne, A.; Queloz, D.; Mayor, M.; Adrianzyk, G.; Knispel, G.; Kohler, D.; Lacroix, D.; Meunier, J.-P.; Rimbaud, G.; Vin, A.

    1996-10-01

    The fibre-fed echelle spectrograph of Observatoire de Haute-Provence, ELODIE, is presented. This instrument has been in operation since the end of 1993 on the 1.93 m telescope. ELODIE is designed as an updated version of the cross-correlation spectrometer CORAVEL, to perform very accurate radial velocity measurements such as needed in the search, by Doppler shift, for brown-dwarfs or giant planets orbiting around nearby stars. In one single exposure a spectrum at a resolution of 42000 (λ/{DELTA}λ) ranging from 3906A to 6811A is recorded on a 1024x1024 CCD. This performance is achieved by using a tanθ=4 echelle grating and a combination of a prism and a grism as cross-disperser. An automatic on-line data treatment reduces all the ELODIE echelle spectra and computes cross-correlation functions. The instrument design and the data reduction algorithms are described in this paper. The efficiency and accuracy of the instrument and its long term instrumental stability allow us to measure radial velocities with an accuracy better than 15m/s for stars up to 9th magnitude in less than 30 minutes exposure time. Observations of 16th magnitude stars are also possible to measure velocities at about 1km/s accuracy. For classic spectroscopic studies (S/N>100) 9th magnitude stars can be observed in one hour exposure time.

  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. Estimating organic chain length through sound velocity measurements.

    PubMed

    Povey, Malcolm J W; Stec, Zoe; Hindle, Scott A; Kennedy, John D; Taylor, Richard G

    2005-02-01

    The ability to measure the length of polymers while monitoring their production is evidently extremely valuable, but is also a useful tool for chemical identification purposes at other times, e.g. the analysis of waste water. A study of the relationship between velocity of sound and chain length has been carried out. Initial studies were performed on two model systems; a series of pure liquid n-alkanes (pentane to hexadecane) and 1-alcohols (methanol to 1-dodecanol). This study was extended to look at an industrially significant system of dimethylsiloxanes 200 fluid (L2, 0.65 cSt) to 200 fluid (5000 cSt). Corresponding density data have been taken from the literature and the adiabatic compressibility determined. The measured adiabatic compressibility has been compared with two molecular models of wound velocity, the Schaaffs model and a development of the Urick equation. The Urick equation approach is based on a determination of the compressibility of the methylene or siloxane repeat units which make up the chains in these linear molecules. We show that the Urick equation approach accurately predicts sound velocity and compressibility for the higher members of each series, whilst the Schaaffs approach fails for the 1-alcohols. We suggest that this is because of the influence of the hydroxyl end group through hydrogen bonding with methylene groups within the chain. This interaction modifies the derived compressibility of the methylene groups, so reducing their compressibility relative to that of the n-alkanes. The technique described provides valuable new insights into end-group, intermolecular and intra-molecular interactions in liquid linear-chain molecules. From this detailed analysis of the mechanisms involved, a model is derived. This model can give very precise estimations of the composition of a pure liquid. In the case of mixtures of polymers, it is necessary to use the modified Urick equation and then, in addition, the concentration dependence of both the

  17. A novel technique to measure subsurface flow velocity

    NASA Astrophysics Data System (ADS)

    Bachmair, S.; Weiler, M.

    2010-12-01

    To better understand subsurface flow (SSF) processes at the hillslope scale, measuring subsurface flow velocity should be of great interest. However, due to the large heterogeneity in time and space, we are faced with the need to continuously measure SSF velocity at several locations within a hillslope over a distance being representative for certain hillslope segments. At present, SSF velocity is either measured by tracer tests over larger distances or via centimeter-scale measurements using heat dissipation or other tracers. This calls for a cheap and easily applicable method to continuously detect subsurface flow velocity in the field over a distance representative for certain hillslope segments. We currently develop a novel technique, which has shown promising results in the laboratory. The technique is based on an automatic salt tracer injection into a small-diameter borehole once the soil matrix has reached saturation. The tracer signal is captured by a 5TE probe (Decagon Devices) measuring soil moisture, electrical conductivity, and temperature every two minutes, which is inserted a few decimetres downslope of the injection point into the soil. The automatic injection is also controlled by the 5TE probe, which is connected to a CR1000 Logger (Campbell Scientific). Once saturated conditions have been established, a plug valve attached to an above-mounted bottle with NaCl solution is opened for 2 seconds and the tracer is injected into the borehole via a small steel tube screened at the bottom. Under saturated conditions the automatic injection is conducted every two hours and the breakthrough curves are analyzed for the mean effective velocity. In a first step, the technique was tested in a sand filled box with constant in- and outflow conditions representing a homogeneous miniature hillslope. Several experimental set-ups differing in hydraulic gradient, distance from injection point to 5TE probe, orientation of 5TE probe, and amount and concentration of

  18. Coherent Laser Instrument Would Measure Range and Velocity

    NASA Technical Reports Server (NTRS)

    Chang, Daniel; Cardell, Greg; San Martin, Alejandro; Spiers, Gary

    2005-01-01

    A proposed instrument would project a narrow laser beam that would be frequency-modulated with a pseudorandom noise (PN) code for simultaneous measurement of range and velocity along the beam. The instrument performs these functions in a low mass, power, and volume package using a novel combination of established techniques. Originally intended as a low resource- footprint guidance sensor for descent and landing of small spacecraft onto Mars or small bodies (e.g., asteroids), the basic instrument concept also lends itself well to a similar application guiding aircraft (especially, small unmanned aircraft), and to such other applications as ranging of topographical features and measuring velocities of airborne light-scattering particles as wind indicators. Several key features of the instrument s design contribute to its favorable performance and resource-consumption characteristics. A laser beam is intrinsically much narrower (for the same exit aperture telescope or antenna) than a radar beam, eliminating the need to correct for the effect of sloping terrain over the beam width, as is the case with radar. Furthermore, the use of continuous-wave (CW), erbium-doped fiber lasers with excellent spectral purity (narrow line width) permits greater velocity resolution, while reducing the laser s power requirement compared to a more typical pulsed solid-state laser. The use of CW also takes proper advantage of the increased sensitivity of coherent detection, necessary in the first place for direct measurement of velocity using the Doppler effect. However, measuring range with a CW beam requires modulation to "tag" portions of it for time-of-flight determination; typically, the modulation consists of a PN code. A novel element of the instrument s design is the use of frequency modulation (FM) to accomplish both the PN-modulation and the Doppler-bias frequency shift necessary for signed velocity measurements. This permits the use of a single low-power waveguide electrooptic

  19. Measured and modeled dry deposition velocities over the ESCOMPTE area

    NASA Astrophysics Data System (ADS)

    Michou, M.; Laville, P.; Serça, D.; Fotiadi, A.; Bouchou, P.; Peuch, V.-H.

    2005-03-01

    Measurements of the dry deposition velocity of ozone have been made by the eddy correlation method during ESCOMPTE (Etude sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d'Emissions). The strong local variability of natural ecosystems was sampled over several weeks in May, June and July 2001 for four sites with varying surface characteristics. The sites included a maize field, a Mediterranean forest, a Mediterranean shrub-land, and an almost bare soil. Measurements of nitrogen oxide deposition fluxes by the relaxed eddy correlation method have also been carried out at the same bare soil site. An evaluation of the deposition velocities computed by the surface module of the multi-scale Chemistry and Transport Model MOCAGE is presented. This module relies on a resistance approach, with a detailed treatment of the stomatal contribution to the surface resistance. Simulations at the finest model horizontal resolution (around 10 km) are compared to observations. If the seasonal variations are in agreement with the literature, comparisons between raw model outputs and observations, at the different measurement sites and for the specific observing periods, are contrasted. As the simulated meteorology at the scale of 10 km nicely captures the observed situations, the default set of surface characteristics (averaged at the resolution of a grid cell) appears to be one of the main reasons for the discrepancies found with observations. For each case, sensitivity studies have been performed in order to see the impact of adjusting the surface characteristics to the observed ones, when available. Generally, a correct agreement with the observations of deposition velocities is obtained. This advocates for a sub-grid scale representation of surface characteristics for the simulation of dry deposition velocities over such a complex area. Two other aspects appear in the discussion. Firstly, the strong influence of the soil water content to the plant

  20. Method and apparatus for measuring flow velocity using matched filters

    SciTech Connect

    Raptis, A.C.

    1981-07-17

    An apparatus and method for measuring the flow velocities of individual phase flow components of a multiphase flow is disclosed. Signals arising from flow noise disturbance are extracted from the flow, at upstream and downstream locations. The signals are processed through pairs of matched filters which are matched to the flow disturbance frequency characteristics of the phase flow component to be measured. The processed signals are then cross-correlated to determine the transit delay time of the phase flow component between sensing positions.

  1. Method and apparatus for measuring flow velocity using matched filters

    DOEpatents

    Raptis, Apostolos C.

    1983-01-01

    An apparatus and method for measuring the flow velocities of individual phase flow components of a multiphase flow utilizes matched filters. Signals arising from flow noise disturbance are extracted from the flow, at upstream and downstream locations. The signals are processed through pairs of matched filters which are matched to the flow disturbance frequency characteristics of the phase flow component to be measured. The processed signals are then cross-correlated to determine the transit delay time of the phase flow component between sensing positions.

  2. Method and apparatus for measuring flow velocity using matched filters

    DOEpatents

    Raptis, A.C.

    1983-09-06

    An apparatus and method for measuring the flow velocities of individual phase flow components of a multiphase flow utilizes matched filters. Signals arising from flow noise disturbance are extracted from the flow, at upstream and downstream locations. The signals are processed through pairs of matched filters which are matched to the flow disturbance frequency characteristics of the phase flow component to be measured. The processed signals are then cross-correlated to determine the transit delay time of the phase flow component between sensing positions. 8 figs.

  3. Las Vegas Basin Seismic Response Project: Measured Shallow Soil Velocities

    NASA Astrophysics Data System (ADS)

    Luke, B. A.; Louie, J.; Beeston, H. E.; Skidmore, V.; Concha, A.

    2002-12-01

    The Las Vegas valley in Nevada is a deep (up to 5 km) alluvial basin filled with interlayered gravels, sands, and clays. The climate is arid. The water table ranges from a few meters to many tens of meters deep. Laterally extensive thin carbonate-cemented lenses are commonly found across parts of the valley. Lenses range beyond 2 m in thickness, and occur at depths exceeding 200 m. Shallow seismic datasets have been collected at approximately ten sites around the Las Vegas valley, to characterize shear and compression wave velocities in the near surface. Purposes for the surveys include modeling of ground response to dynamic loads, both natural and manmade, quantification of soil stiffness to aid structural foundation design, and non-intrusive materials identification. Borehole-based measurement techniques used include downhole and crosshole, to depths exceeding 100 m. Surface-based techniques used include refraction and three different methods involving inversion of surface-wave dispersion datasets. This latter group includes two active-source techniques, the Spectral Analysis of Surface Waves (SASW) method and the Multi-Channel Analysis of Surface Waves (MASW) method; and a new passive-source technique, the Refraction Mictrotremor (ReMi) method. Depths to halfspace for the active-source measurements ranged beyond 50 m. The passive-source method constrains shear wave velocities to 100 m depths. As expected, the stiff cemented layers profoundly affect local velocity gradients. Scale effects are evident in comparisons of (1) very local measurements typified by borehole methods, to (2) the broader coverage of the SASW and MASW measurements, to (3) the still broader and deeper resolution made possible by the ReMi measurements. The cemented layers appear as sharp spikes in the downhole datasets and are problematic in crosshole measurements due to refraction. The refraction method is useful only to locate the depth to the uppermost cemented layer. The surface

  4. Measuring the Spin Period of a High-Velocity Pulsar

    NASA Astrophysics Data System (ADS)

    Tomsick, John

    2012-10-01

    X-ray observations of IGR J11014-6103 show that it has a complex morphology with a point source and two components of extended emission. Its properties indicate that it is very likely to be a pulsar wind nebula (PWN). Chandra and radio observations strongly suggest that the compact object is moving away from SNR MSH 11-61A. Based on the evolution of this supernova remnant, an association would indicate that IGR J11014-6103 has a transverse velocity of 2,400 to 2,900 km/s. The possibility of such a high kick velocity makes the proposed timing study important for proving that the compact object is a pulsar, determining its period (P), and measuring dP/dt to determine if the characteristic age is consistent with the pulsar originating in MSH 11-61A.

  5. In-situ measurements of velocity structure within turbidity currents

    USGS Publications Warehouse

    Xu, J. P.; Noble, M.A.; Rosenfeld, L.K.

    2004-01-01

    Turbidity currents are thought to be the main mechanism to move ???500,000 m3 of sediments annually from the head of the Monterey Submarine Canyon to the deep-sea fan. Indirect evidence has shown frequent occurrences of such turbidity currents in the canyon, but the dynamic properties of the turbidity currents such as maximum speed, duration, and dimensions are still unknown. Here we present the first-ever in-situ measurements of velocity profiles of four turbidity currents whose maximum along-canyon velocity reached 190 cm/s. Two turbidity currents coincided with storms that produced the highest swells and the biggest stream flows during the year-long deployment. Copyright 2004 by the American Geophysical Union.

  6. 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.

  7. Ice Velocity Map of Antarctica measured with ALOS PALSAR

    NASA Astrophysics Data System (ADS)

    Mouginot, J.; Scheuchl, B.; Rignot, E. J.

    2010-12-01

    Ice velocity is fundamental characteristic of the dynamics of ice sheet and is essential to know for measuring the mass budget of ice sheet and for controlling ice sheet numerical models with realistic boundary conditions. Until recently, data were mostly available on a discrete basis over small areas with variable precision. Here, we report on our results of processing ice velocity from he interferometric synthetic-aperture radar data acquired by ALOS PALSAR in 2007, 2008 and 2009 by the Japan Aerospace Exploration Agency (JAXA) and distributed by NASA's Alaska Satellite Facility (ASF). The goal of our project is to produce a new set of Earth Science Data Record (ESDR): high-resolution digital maps of ice velocity of the Antarctic ice sheet. This new ESDR will be based on spaceborne Synthetic Aperture Radar (SAR) data from multiple missions. It will be distributed to the scientific community via institutional links already in place at the National Snow and Ice Data Center (NSIDC). The EDSR will benefit glaciologists and ice sheet modelers, but also climate modelers interested in how ice sheets are evolving, physical oceanographers studying sea level change and changes in oceanic circulation, solid earth scientists interested in post-glacial rebound, atmospheric scientists interested in surface mass balance in Antarctica. This effort will establish a long-term legacy for quantitative measurements of the dynamics of polar ice sheets. Areas north of 78 degrees south were first covered by RADARSAT-1 during the RAMP campaign. ALOS PALSAR and ENVISAT ASAR were tasked to cover the area in 2007, 2008 and 2009. PALSAR 46-day speckle tracking works well even in areas where C-band sensors lose signal coherence, which helps us to complete a full coverage of Antarctica's coastal regions. One challenge for L-band data is the sensitivity to ionosphere disturbances and another is to lower data noise in vast interior where flow velocities drop to below a few meters per year. We

  8. Unsteady velocity measurements in a realistic intracranial aneurysm model

    NASA Astrophysics Data System (ADS)

    Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György

    2012-01-01

    The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.

  9. Spatiotemporal Dynamics of the Wind Velocity from Minisodar Measurement Data

    NASA Astrophysics Data System (ADS)

    Simakhin, V. A.; Cherepanov, O. S.; Shamanaeva, L. G.

    2016-04-01

    The spatiotemporal dynamics of the three wind velocity components in the atmospheric boundary layer is analyzed on the basis of Doppler minisodar measurements. The data were processed and analyzed with the help of robust nonparametric methods based on the weighted maximum likelihood method and classical methods. Distribution laws were obtained for each wind velocity component. There are outliers in the distribution functions; both right and left asymmetry of the distributions are observed. For the x- and ycomponents, the width of the distribution increases as the observation altitude is increased, but the maximum of the distribution function decreases, which is in agreement with the data available in the literature. For the zcomponents the width of the distribution remains practically constant, but the value of the maximum also decreases with altitude. Analysis of the hourly semidiurnal dynamics showed that all three components have maxima in the morning and evening hours. For the y- and z-components the maxima in the evening hours are more strongly expressed than in the morning hours. For the x- and y-components the horizontal wind shear is closely tracked in the evening hours. It is shown that adaptive estimates on the efficiency significantly exceed the classical parametric estimates and allow one to analyze the spatiotemporal dynamics of the wind velocity, and reveal jets and detect wind shears.

  10. An ultrasonic transducer array for velocity measurement in underwater vehicles.

    PubMed

    Boltryk, P; Hill, M; Keary, A; Phillips, B; Robinson, H; White, P

    2004-04-01

    A correlation velocity log (CVL) is an ultrasonic navigation aid for marine applications, in which velocity is estimated using an acoustic transmitter and a receiver array. CVLs offer advantages over Doppler velocity logs (DVLs) in many autonomous underwater vehicle (AUV) applications, since they can achieve high accuracy at low velocities even during hover manoeuvres. DVLs require narrow beam widths, whilst ideal CVL transmitters have wide beam widths. This gives CVLs the potential to use lower frequencies thus permitting operation in deeper water, reducing power requirements for the same depth, or allowing the use of smaller transducers. Moving patterns in the wavefronts across a 2D receiver array are detected by calculating correlation coefficients between bottom reflections from consecutive transmitted pulses, across all combinations of receiver pairings. The position of the peak correlation value, on a surface representing receiver-pairing separations, is proportional to the vessel's displacement between pulses. A CVL aimed primarily for AUVs has been developed. Its acoustical and signal processing design has been optimised through sea trials and computer modelling of the sound field. This computer model is also used to predict how the distribution of the correlation coefficients varies with distance from the peak position. Current work seeks to increase the resolution of the peak estimate using surface fitting methods. Numerical simulations suggest that peak estimation methods significantly improve system precision when compared with simply identifying the position of the maximum correlation coefficient in the dataset. The peak position may be estimated by fitting a quadratic model to the measured data using least squares or maximum likelihood estimation. Alternatively, radial basis functions and Gaussian processes successfully predict the peak position despite variation between individual correlation datasets. This paper summarises the CVL's main acoustical

  11. Measurement of surface recombination velocity on heavily doped indium phosphide

    NASA Technical Reports Server (NTRS)

    Jenkins, Phillip; Ghalla-Goradia, Manju; Faur, Mircea; Faur, Maria; Bailey, Sheila

    1990-01-01

    Surface recombination velocity (SRV) on heavily doped n-type and p-type InP was measured as a function of surface treatment. For the limited range of substrates and surface treatments studied, SRV and surface stability depend strongly on the surface treatment. SRVs of 100,000 cm/sec in both p-type and n-type InP are obtainable, but in n-type the low-SRV surfaces were unstable, and the only stable surfaces on n-type had SRVs of more than 10to the 6th cm/sec.

  12. Phase Velocity Method for Guided Wave Measurements in Composite Plates

    NASA Astrophysics Data System (ADS)

    Moreno, E.; Galarza, N.; Rubio, B.; Otero, J. A.

    Carbon Fiber Reinforced Polymer is a well-recognized material for aeronautic applications. Its plane structure has been widely used where anisotropic characteristics should be evaluated with flaw detection. A phase velocity method of ultrasonic guided waves based on a pitch-catch configuration is presented for this purpose. Both shear vertical (SV) and shear horizontal (SH) have been studied. For SV (Lamb waves) the measurements were done at different frequencies in order to evaluate the geometrical dispersion and elastic constants. The results for SV are discussed with an orthotropic elastic model. Finally experiments with lamination flaws are presented.

  13. Measurements of parallel electron velocity distributions using whistler wave absorption

    SciTech Connect

    Thuecks, D. J.; Skiff, F.; Kletzing, C. A.

    2012-08-15

    We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense ({omega}{sub pe} > {omega}{sub ce}). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency {omega}{sub ce}. As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation {omega}-k{sub ||v||} = {omega}{sub ce}. The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

  14. Full field gas phase velocity measurements in microgravity

    NASA Technical Reports Server (NTRS)

    Griffin, Devon W.; Yanis, William

    1995-01-01

    Measurement of full-field velocities via Particle Imaging Velocimetry (PIV) is common in research efforts involving fluid motion. While such measurements have been successfully performed in the liquid phase in a microgravity environment, gas-phase measurements have been beset by difficulties with seeding and laser strength. A synthesis of techniques developed at NASA LeRC exhibits promise in overcoming these difficulties. Typical implementation of PIV involves forming the light from a pulsed laser into a sheet that is some fraction of a millimeter thick and 50 or more millimeters wide. When a particle enters this sheet during a pulse, light scattered from the particle is recorded by a detector, which may be a film plane or a CCD array. Assuming that the particle remains within the boundaries of the sheet for the second pulse and can be distinguished from neighboring particles, comparison of the two images produces an average velocity vector for the time between the pulses. If the concentration of particles in the sampling volume is sufficiently large but the particles remain discrete, a full field map may be generated.

  15. A radionuclide counting technique for measuring wind velocity

    NASA Astrophysics Data System (ADS)

    Singh, J. J.; Khandelwal, G. S.; Mall, G. H.

    1981-12-01

    A technique for measuring wind velocities of meteorological interest is described. It is based on inverse-square-law variation of the counting rates as the radioactive source-to-counter distance is changed by wind drag on the source ball. Results of a feasibility study using a weak bismuth 207 radiation source and three Geiger-Muller radiation counters are reported. The use of the technique is not restricted to Martian or Mars-like environments. A description of the apparatus, typical results, and frequency response characteristics are included. A discussion of a double-pendulum arrangement is presented. Measurements reported herein indicate that the proposed technique may be suitable for measuring wind speeds up to 100 m/sec, which are either steady or whose rates of fluctuation are less than 1 kHz.

  16. Double-path acquisition of pulse wave transit time and heartbeat using self-mixing interferometry

    NASA Astrophysics Data System (ADS)

    Wei, Yingbin; Huang, Wencai; Wei, Zheng; Zhang, Jie; An, Tong; Wang, Xiulin; Xu, Huizhen

    2017-06-01

    We present a technique based on self-mixing interferometry for acquiring the pulse wave transit time (PWTT) and heartbeat. A signal processing method based on Continuous Wavelet Transform and Hilbert Transform is applied to extract potentially useful information in the self-mixing interference (SMI) signal, including PWTT and heartbeat. Then, some cardiovascular characteristics of the human body are easily acquired without retrieving the SMI signal by complicated algorithms. Experimentally, the PWTT is measured on the finger and the toe of the human body using double-path self-mixing interferometry. Experimental statistical data show the relation between the PWTT and blood pressure, which can be used to estimate the systolic pressure value by fitting. Moreover, the measured heartbeat shows good agreement with that obtained by a photoplethysmography sensor. The method that we demonstrate, which is based on self-mixing interferometry with significant advantages of simplicity, compactness and non-invasion, effectively illustrates the viability of the SMI technique for measuring other cardiovascular signals.

  17. Intraglottal geometry and velocity measurements in canine larynges

    PubMed Central

    Oren, Liran; Khosla, Sid; Gutmark, Ephraim

    2014-01-01

    Previous flow velocity measurements during phonation in canine larynges were done above the glottal exit. These studies found that vortical structures are present in the flow above the glottis at different phases of the glottal cycle. Some vortices were observed to leave the glottis during the closing phase and assumptions were proposed regarding their formation mechanism. In the current study, intraglottal velocity measurements are performed using PIV, and the intraglottal flow characteristics are determined. Results from five canine larynges show that at low subglottal pressure the glottis assumes a minimal divergence angle during closing and the flow separates at the glottal exit. Vortical structures are observed above the glottis but not inside. As the subglottal pressure is increased, the divergence angle between the folds during closing increases and the location of the flow separation moves upstream into the glottis. Entrainment flow enters the glottis to fill the void that is formed between the glottal jet and the fold. Vortical structures develop near the superior edge at medium and high subglottal pressures from the flow separation. The magnitude of their swirling strength changes as a function of the wall dynamics. PMID:24437778

  18. Improved technique for blood flow velocity measurement using Doppler effect

    NASA Astrophysics Data System (ADS)

    Valadares Oliveira, Eduardo J.; Nantes Button, Vera L. d. S.; Maia, Joaquim M.; Costa, Eduardo T.

    2002-04-01

    The Doppler velocimeter developed allows to determine the angle between the ultrasonic beam and the velocity vector of the flow, and to calculate the precise blood flow in a vessel. Four piezoelectric transducers constitute the Doppler velocimeter. Three of these transducers are positioned to form an equilateral triangle (base of a pyramid). When these transducers move simultaneously, backward or forward from the initial position, the emitted ultrasonic beams focalize on a position (peak of the pyramid) closer or farther from the transducers faces, according to the depth of the vessel where we intend to measure de flow. The angle between the transducers allows adjusting the height of this pyramid and the position of the focus (where the three beams meet). A forth transducer is used to determine the diameter of the vessel and monitor the position of the Doppler velocimeter relative to the vessel. Simulation results showed that with this technique is possible to accomplish precise measurement of blood flow.

  19. 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.

  20. 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.

  1. Ultrasound Velocity Measurement in a Liquid Metal Electrode.

    PubMed

    Perez, Adalberto; Kelley, Douglas H

    2015-08-05

    A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within ±2 °C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

  2. Magnetic induction system for two-stage gun projectile velocity measurements

    SciTech Connect

    Moody, R L; Konrad, C H

    1984-05-01

    A magnetic induction technique for measuring projectile velocities has been implemented on Sandia's two-stage light gas gun. The system has been designed to allow for projectile velocity measurements to an accuracy of approx. 0.2 percent. The velocity system has been successfully tested in a velocity range of 3.5 km/s to 6.5 km/s.

  3. Multifractal structures in radial velocity measurements for exoplanets

    NASA Astrophysics Data System (ADS)

    Del Sordo, Fabio; Sahil Agarwal, Debra A. Fischer, John S. Wettlaufer

    2015-01-01

    The radial velocity method is a powerful way to search for exoplanetary systems and it led to many discoveries of exoplanets in the last 20 years.Nevertheless, in order observe Earth-like planets, such method needs to be refined, i.e. one needs to improve the signal-to-noise ratio.On one hand this can be achieved by building spectrographs with better performances, but on the other hand it is also central to understand the noise present in the data.Radial-velocity data are time-series which contains the effect of planets as well as of stellar disturbances. Therefore, they are the result of different physical processes which operate on different time-scales, acting in a not always periodic fashionI present here a possible approach to such problem, which consists in looking for multifractal structures in the time-series coming from radial velocity measurements, identifying the underlying long-range correlations and fractal scaling properties, and connecting them to the underlying physical processes, like stellar oscillation, granulation, rotation, and magnetic activity.This method has been previously applied to satellite data related to Arctic sea albedo, relevant for identify trends and noise in the Arctic sea ice (Agarwal, Moon and Wettlaufer, Proc. R. Soc., 2012).Here we use such analysis for exoplanetary data related to possible Earth-like planets.Moreover, we apply the same procedure to synthetic data from numerical simulation of stellar dynamos, which give insight on the mechanism responsible for the noise. In such way we can therefore raise the signal-to-noise ratio in the data using the synthetic data as predicted noise to be subtracted from the observations.

  4. Force-Velocity Measurements of a Few Growing Actin Filaments

    PubMed Central

    Brangbour, Coraline; du Roure, Olivia; Helfer, Emmanuèle; Démoulin, Damien; Mazurier, Alexis; Fermigier, Marc; Carlier, Marie-France; Bibette, Jérôme; Baudry, Jean

    2011-01-01

    The polymerization of actin in filaments generates forces that play a pivotal role in many cellular processes. We introduce a novel technique to determine the force-velocity relation when a few independent anchored filaments grow between magnetic colloidal particles. When a magnetic field is applied, the colloidal particles assemble into chains under controlled loading or spacing. As the filaments elongate, the beads separate, allowing the force-velocity curve to be precisely measured. In the widely accepted Brownian ratchet model, the transduced force is associated with the slowing down of the on-rate polymerization. Unexpectedly, in our experiments, filaments are shown to grow at the same rate as when they are free in solution. However, as they elongate, filaments are more confined in the interspace between beads. Higher repulsive forces result from this higher confinement, which is associated with a lower entropy. In this mechanism, the production of force is not controlled by the polymerization rate, but is a consequence of the restriction of filaments' orientational fluctuations at their attachment point. PMID:21541364

  5. Velocity field measurements in the wake of a propeller model

    NASA Astrophysics Data System (ADS)

    Mukund, R.; Kumar, A. Chandan

    2016-10-01

    Turboprop configurations are being revisited for the modern-day regional transport aircrafts for their fuel efficiency. The use of laminar flow wings is an effort in this direction. One way to further improve their efficiency is by optimizing the flow over the wing in the propeller wake. Previous studies have focused on improving the gross aerodynamic characteristics of the wing. It is known that the propeller slipstream causes early transition of the boundary layer on the wing. However, an optimized design of the propeller and wing combination could delay this transition and decrease the skin friction drag. Such a wing design would require the detailed knowledge of the development of the slipstream in isolated conditions. There are very few studies in the literature addressing the requirements of transport aircraft having six-bladed propeller and cruising at a high propeller advance ratio. Low-speed wind tunnel experiments have been conducted on a powered propeller model in isolated conditions, measuring the velocity field in the vertical plane behind the propeller using two-component hot-wire anemometry. The data obtained clearly resolved the mean velocity, the turbulence, the ensemble phase averages and the structure and development of the tip vortex. The turbulence in the slipstream showed that transition could be close to the leading edge of the wing, making it a fine case for optimization. The development of the wake with distance shows some interesting flow features, and the data are valuable for flow computation and optimization.

  6. Upper Mississippi embayment shallow seismic velocities measured in situ

    USGS Publications Warehouse

    Liu, Huaibao P.; Hu, Y.; Dorman, J.; Chang, T.-S.; Chiu, J.-M.

    1997-01-01

    Vertical seismic compressional- and shear-wave (P- and S-wave) profiles were collected from three shallow boreholes in sediment of the upper Mississippi embayment. The site of the 60-m hole at Shelby Forest, Tennessee, is on bluffs forming the eastern edge of the Mississippi alluvial plain. The bluffs are composed of Pleistocene loess, Pliocene-Pleistocene alluvial clay and sand deposits, and Tertiary deltaic-marine sediment. The 36-m hole at Marked Tree, Arkansas, and the 27-m hole at Risco, Missouri, are in Holocene Mississippi river floodplain sand, silt, and gravel deposits. At each site, impulsive P- and S-waves were generated by man-made sources at the surface while a three-component geophone was locked downhole at 0.91-m intervals. Consistent with their very similar geology, the two floodplain locations have nearly identical S-wave velocity (VS) profiles. The lowest VS values are about 130 m s-1, and the highest values are about 300 m s-1 at these sites. The shear-wave velocity profile at Shelby Forest is very similar within the Pleistocene loess (12m thick); in deeper, older material, VS exceeds 400 m s-1. At Marked Tree, and at Risco, the compressional-wave velocity (VP) values above the water table are as low as about 230 m s-1, and rise to about 1.9 km s-1 below the water table. At Shelby Forest, VP values in the unsaturated loess are as low as 302 m s-1. VP values below the water table are about 1.8 km s-1. For the two floodplain sites, the VP/VS ratio increases rapidly across the water table depth. For the Shelby Forest site, the largest increase in the VP/VS ratio occurs at ???20-m depth, the boundary between the Pliocene-Pleistocene clay and sand deposits and the Eocene shallow-marine clay and silt deposits. Until recently, seismic velocity data for the embayment basin came from earthquake studies, crustal-scale seismic refraction and reflection profiles, sonic logs, and from analysis of dispersed earthquake surface waves. Since 1991, seismic data

  7. Pulse wave detection method based on the bio-impedance of the wrist

    NASA Astrophysics Data System (ADS)

    He, Jianman; Wang, Mengjun; Li, Xiaoxia; Li, Gang; Lin, Ling

    2016-05-01

    The real-time monitoring of pulse rate can evaluate the heart health to some extent, and the measurement of bio-impedance has the potential in wearable health monitoring system. In this paper, an effective method, which contains self-balancing bridge, flexible electrode, and high-speed digital lock-in algorithm (DLIA) with over-sampling, was designed to detect the impedance pulse wave at the wrist. By applying the self-balancing bridge, the basic impedance can be compensated as much as possible, and the low amplitude of impedance variation related to heart pulse can be obtained more easily. And the flexible conductive rubber electrode used in our experiment is human-friendly. Besides, the over-sampling method and high-speed DLIA are used to enhance the effective resolution of the existing data sampled by analog to digital converter. With the high-speed data process and simple circuit above, this proposed method has the potential in wrist-band wearable systems and it can satisfy quests of small volume and low power consumption.

  8. A novel continuous cardiac output monitor based on pulse wave transit time.

    PubMed

    Sugo, Yoshihiro; Ukawa, Teiji; Takeda, Sunao; Ishihara, Hironori; Kazama, Tomiei; Takeda, Junzo

    2010-01-01

    Monitoring cardiac output (CO) is important for the management of patient circulation in an operation room (OR) or intensive care unit (ICU). We assumed that the change in pulse wave transit time (PWTT) obtained from an electrocardiogram (ECG) and a pulse oximeter wave is correlated with the change in stroke volume (SV), from which CO is derived. The present study reports the verification of this hypothesis using a hemodynamic analysis theory and animal study. PWTT consists of a pre-ejection period (PEP), the pulse transit time through an elasticity artery (T(1)), and the pulse transit time through peripheral resistance arteries (T(2)). We assumed a consistent negative correlation between PWTT and SV under all conditions of varying circulatory dynamics. The equation for calculating SV from PWTT was derived based on the following procedures. 1. Approximating SV using a linear equation of PWTT. 2. The slope and y-intercept of the above equation were determined under consideration of vessel compliance (SV was divided by Pulse Pressure (PP)), animal type, and the inherent relationship between PP and PWTT. Animal study was performed to verify the above-mentioned assumption. The correlation coefficient of PWTT and SV became r = -0.710 (p 〈 0.001), and a good correlation was admitted. It has been confirmed that accurate continuous CO and SV measurement is only possible by monitoring regular clinical parameters (ECG, SpO2, and NIBP).

  9. Simultaneous Temperature and Velocity Measurements in a Large-Scale, Supersonic, Heated Jet

    NASA Technical Reports Server (NTRS)

    Danehy, P. M.; Magnotti, G.; Bivolaru, D.; Tedder, S.; Cutler, A. D.

    2008-01-01

    Two laser-based measurement techniques have been used to characterize an axisymmetric, combustion-heated supersonic jet issuing into static room air. The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) measurement technique measured temperature and concentration while the interferometric Rayleigh scattering (IRS) method simultaneously measured two components of velocity. This paper reports a preliminary analysis of CARS-IRS temperature and velocity measurements from selected measurement locations. The temperature measurements show that the temperature along the jet axis remains constant while dropping off radially. The velocity measurements show that the nozzle exit velocity fluctuations are about 3% of the maximum velocity in the flow.

  10. Radio-controlled boat for measuring water velocities and bathymetry

    NASA Astrophysics Data System (ADS)

    Vidmar, Andrej; Bezak, Nejc; Sečnik, Matej

    2016-04-01

    Radio-controlled boat named "Hi3" was designed and developed in order to facilitate water velocity and bathymetry measurements. The boat is equipped with the SonTek RiverSurveyor M9 instrument that is designed for measuring open channel hydraulics (discharge and bathymetry). Usually channel cross sections measurements are performed either from a bridge or from a vessel. However, these approaches have some limitations such as performing bathymetry measurements close to the hydropower plant turbine or downstream from a hydropower plant gate where bathymetry changes are often the most extreme. Therefore, the radio-controlled boat was designed, built and tested in order overcome these limitations. The boat is made from a surf board and two additional small balance support floats. Additional floats are used to improve stability in fast flowing and turbulent parts of rivers. The boat is powered by two electric motors, steering is achieved with changing the power applied to left and right motor. Furthermore, remotely controlled boat "Hi3" can be powered in two ways, either by a gasoline electric generator or by lithium batteries. Lithium batteries are lighter, quieter, but they operation time is shorter compared to an electrical generator. With the radio-controlled boat "Hi3" we can perform measurements in potentially dangerous areas such as under the lock gates at hydroelectric power plant or near the turbine outflow. Until today, the boat "Hi3" has driven more than 200 km in lakes and rivers, performing various water speed and bathymetry measurements. Moreover, in future development the boat "Hi3" will be upgraded in order to be able to perform measurements automatically. The future plans are to develop and implement the autopilot. With this approach the user will define the route that has to be driven by the boat and the boat will drive the pre-defined route automatically. This will be possible because of the very accurate differential GPS from the Sontek River

  11. Velocity difference measurement with a fiber-optic coupler.

    PubMed

    Du, Y; Ackerson, B J; Tong, P

    1998-09-01

    Two single-mode fibers collect light with the same scattered wave vector from two spatially separated regions in a sample. These regions are illuminated by a single coherent laser beam, so that the collected signals interfere when combined by means of a fiber-optic coupler, before they are directed to a photomultiplier tube. The fibers and the coupler are polarization preserving to guarantee a high signal-to-noise ratio. The measured intensity fluctuations are used to determine the velocity difference omega v(L) for spatial separations L in the sample. Specifically, an intensity autocorrelation function is calculated theoretically for rigid body rotation and is tested experimentally. Experimental results span two orders of magnitude in L and agree with theoretical predictions with an error of less than 5%. This new technique will be very useful in the study of turbulent flow and particle settling dynamics.

  12. Monolithic interferometer for high precision radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Wan, Xiaoke; Ge, Jian; Wang, Ji; Lee, Brian

    2009-08-01

    In high precision radial velocity (RV) measurements for extrasolar planets searching and studies, a stable wide field Michelson interferometer is very critical in Exoplanet Tracker (ET) instruments. Adopting a new design, monolithic interferometers are homogenous and continuous in thermal expansion, and field compensation and thermal compensation are both satisfied. Interferometer design and fabrication are decrypted in details. In performance evaluations, field angle is typically 22° and thermal sensitivity is typically -1.7 x 10-6/°C, which corresponds to ~500 m/s /°C in RV scale. In interferometer stability monitoring using a wavelength stabilized laser source, phase shift data was continuously recorded for nearly seven days. Appling a frequent calibration every 30 minutes as in typical star observations, the interferometer instability contributes less than 1.4 m/s in RV error, in a conservative estimation.

  13. The symbiosis of photometry and radial-velocity measurements

    NASA Technical Reports Server (NTRS)

    Cochran, William D.

    1994-01-01

    The FRESIP mission is optimized to detect the inner planets of a planetary system. According to the current paradigm of planet formation, these planets will probably be small Earth-sized objects. Ground-based radial-velocity programs now have the sensitivity to detect Jovian-mass planets in orbit around bright solar-type stars. We expect the more massive planets to form in the outer regions of a proto-stellar nebula. These two types of measurements will very nicely complement each other, as they have highest detection probability for very different types of planets. The combination of FRESIP photometry and ground-based spectra will provide independent confirmation of the existence of planetary systems in orbit around other stars. Such detection of both terrestrial and Jovian planets in orbit around the same star is essential to test our understanding of planet formation.

  14. HUBBLE MEASURES VELOCITY OF GAS ORBITING BLACK HOLE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A schematic diagram of velocity measurements of a rotating disk of hot gas in the core of active galaxy M87. The measurement was made by studying how the light from the disk is redshifted and blueshifted -- as part of the swirling disk spins in earth's direction and the other side spins away from earth. The gas on one side of the disk is speeding away from Earth, at a speed of about 1.2 million miles per hour (550 kilometers per second). The gas on the other side of the disk is orbiting around at the same speed, but in the opposite direction, as it approaches viewers on Earth. This high velocity is the signature of the tremendous gravitational field at the center of M87. This is clear evidence that the region harbors a massive black hole, since it contains only a fraction of the number of stars that would be necessary to create such a powerful attraction. A black hole is an object that is so massive yet compact nothing can escape its gravitational pull, not even light. The object at the center of M87 fits that description. It weights as much as three billion suns, but is concentrated into a space no larger than our solar system. The observations were made with HST's Faint Object Spectrograph. Credit: Holland Ford, Space Telescope Science Institute/Johns Hopkins University; Richard Harms, Applied Research Corp.; Zlatan Tsvetanov, Arthur Davidsen, and Gerard Kriss at Johns Hopkins; Ralph Bohlin and George Hartig at Space Telescope Science Institute; Linda Dressel and Ajay K. Kochhar at Applied Research Corp. in Landover, Md.; and Bruce Margon from the University of Washington in Seattle. NASA PHOTO CAPTION STScI-PR94-23b

  15. Low Velocity Difference Thermal Shear Layer Mixing Rate Measurements

    NASA Technical Reports Server (NTRS)

    Bush, Robert H.; Culver, Harry C. M.; Weissbein, Dave; Georgiadis, Nicholas J.

    2013-01-01

    Current CFD modeling techniques are known to do a poor job of predicting the mixing rate and persistence of slot film flow in co-annular flowing ducts with relatively small velocity differences but large thermal gradients. A co-annular test was devised to empirically determine the mixing rate of slot film flow in a constant area circular duct (D approx. 1ft, L approx. 10ft). The axial rate of wall heat-up is a sensitive measure of the mixing rate of the two flows. The inflow conditions were varied to simulate a variety of conditions characteristic of moderate by-pass ratio engines. A series of air temperature measurements near the duct wall provided a straightforward means to measure the axial temperature distribution and thus infer the mixing rate. This data provides a characterization of the slot film mixing rates encountered in typical jet engine environments. The experimental geometry and entrance conditions, along with the sensitivity of the results as the entrance conditions vary, make this a good test for turbulence models in a regime important to modern air-breathing propulsion research and development.

  16. Design and Implementation of High Frequency Ultrasound Pulsed-Wave Doppler Using FPGA

    PubMed Central

    Hu, Chang-hong; Zhou, Qifa; Shung, K. Kirk

    2009-01-01

    The development of a field-programmable gate array (FPGA)-based pulsed-wave Doppler processing approach in pure digital domain is reported in this paper. After the ultrasound signals are digitized, directional Doppler frequency shifts are obtained with a digital-down converter followed by a low-pass filter. A Doppler spectrum is then calculated using the complex fast Fourier transform core inside the FPGA. In this approach, a pulsed-wave Doppler implementation core with reconfigurable and real-time processing capability is achieved. PMID:18986909

  17. Estimation of Arterial Pulse Wave Velocity With a New Improved Tissue Doppler Method

    DTIC Science & Technology

    2007-11-02

    the value found in human muscular arteries [15]. PWV estimation is still possible but the variance tends to increase. CONCLUSION The described... distensibility in populations with high and low prevalence of hypertension: comparison between urban and rural communites in china. Circulation, 71:202

  18. Effects of Mechanical Pumping on the Arterial Pulse Wave Velocity: Peripheral Artery and Micro-Vessels

    DTIC Science & Technology

    2007-11-02

    The venous pump of the human foot : preliminary report,” Bristol Med Chir J, vol. 98, pp.109-14. 1983. [3] A.M.N. Gardner, R.H. Fox, C. Lawrence...A.M.N Gardner, R.H. Fox, “The venous pump of the human foot : preliminary report,” Bristol Med Chir J, vol. 98, pp.109-14. 1983. [10] GARDNER, A. M

  19. Complete velocity distribution in river cross-sections measured by acoustic instruments

    USGS Publications Warehouse

    Cheng, R.T.; Gartner, J.W.; ,

    2003-01-01

    To fully understand the hydraulic properties of natural rivers, velocity distribution in the river cross-section should be studied in detail. The measurement task is not straightforward because there is not an instrument that can measure the velocity distribution covering the entire cross-section. Particularly, the velocities in regions near the free surface and in the bottom boundary layer are difficult to measure, and yet the velocity properties in these regions play the most significant role in characterizing the hydraulic properties. To further characterize river hydraulics, two acoustic instruments, namely, an acoustic Doppler current profiler (ADCP), and a "BoogieDopp" (BD) were used on fixed platforms to measure the detailed velocity profiles across the river. Typically, 20 to 25 stations were used to represent a river cross-section. At each station, water velocity profiles were measured independently and/or concurrently by an ADCP and a BD. The measured velocity properties were compared and used in computation of river discharge. In a tow-tank evaluation of a BD, it has been confirmed that BD is capable of measuring water velocity at about 11 cm below the free-surface. Therefore, the surface velocity distribution across the river was extracted from the BD velocity measurements and used to compute the river discharge. These detailed velocity profiles and the composite velocity distribution were used to assess the validity of the classic theories of velocity distributions, conventional river discharge measurement methods, and for estimates of channel bottom roughness.

  20. On the Extraction of Angular Velocity from Attitude Measurements

    NASA Technical Reports Server (NTRS)

    Bar-Itzhack, I. Y.; Harman, Richard R.; Thienel, Julie K.

    2006-01-01

    In this paper we research the extraction of the angular rate vector from attitude information without differentiation, in particular from quaternion measurements. We show that instead of using a Kalman filter of some kind, it is possible to obtain good rate estimates, suitable for spacecraft attitude control loop damping, using simple feedback loops, thereby eliminating the need for recurrent covariance computation performed when a Kalman filter is used. This considerably simplifies the computations required for rate estimation in gyro-less spacecraft. Some interesting qualities of the Kalman filter gain are explored, proven and utilized. We examine two kinds of feedback loops, one with varying gain that is proportional to the well known Q matrix, which is computed using the measured quaternion, and the other type of feedback loop is one with constant coefficients. The latter type includes two kinds; namely, a proportional feedback loop, and a proportional-integral feedback loop. The various schemes are examined through simulations and their performance is compared. It is shown that all schemes are adequate for extracting the angular velocity at an accuracy suitable for control loop damping.

  1. Video Measurement of the Muzzle Velocity of a Potato Gun

    ERIC Educational Resources Information Center

    Jasperson, Christopher; Pollman, Anthony

    2011-01-01

    Using first principles, a theoretical equation for the maximum and actual muzzle velocities for a pneumatic cannon was recently derived. For a fixed barrel length, this equation suggests that the muzzle velocity can be enhanced by maximizing the product of the initial pressure and the volume of the propellant gas and decreasing the projectile…

  2. Measurement of the shock front velocity produced in a T-tube

    SciTech Connect

    Djurović, S.; Mijatović, Z.; Vujičić, B.; Kobilarov, R.; Savić, I.; Gavanski, L.

    2015-01-15

    A set of shock front velocity measurements is described in this paper. The shock waves were produced in a small electromagnetically driven shock T-tube. Most of the measurements were performed in hydrogen. The shock front velocity measurements in other gases and the velocity of the gas behind the shock front were also analyzed, as well as the velocity dependence on applied input energy. Some measurements with an applied external magnetic field were also performed. The used method of shock front velocity is simple and was shown to be very reliable. Measured values were compared with the calculated ones for the incident and reflected shock waves.

  3. Shock wave velocity measuring system based on vernier VISAR-type interferometers

    NASA Astrophysics Data System (ADS)

    Gubskii, K. L.; Koshkin, D. S.; Antonov, A. S.; Mikhailuk, A. V.; Pirog, V. A.; Kuznetsov, A. P.

    2015-11-01

    The paper presents a multi-line diagnostic system for measuring the surface velocity in shock physics experiments. This system is designed for simultaneous measurement of surface velocity at multiple points. It is free from ambiguity caused by harmonic dependence of interference signals on the velocity and has a time resolution of 0.8 ns.

  4. [Design and implementation of the pulse wave generator with field programmable gate array based on windkessel model].

    PubMed

    Wang, Hao; Fu, Quanhai; Xu, Lisheng; Liu, Jia; He, Dianning; Li, Qingchun

    2014-10-01

    Pulse waves contain rich physiological and pathological information of the human vascular system. The pulse wave diagnosis systems are very helpful for the clinical diagnosis and treatment of cardiovascular diseases. Accurate pulse waveform is necessary to evaluate the performances of the pulse wave equipment. However, it is difficult to obtain accurate pulse waveform due to several kinds of physiological and pathological conditions for testing and maintaining the pulse wave acquisition devices. A pulse wave generator was designed and implemented in the present study for this application. The blood flow in the vessel was simulated by modeling the cardiovascular system with windkessel model. Pulse waves can be generated based on the vascular systems with four kinds of resistance. Some functional models such as setting up noise types and signal noise ratio (SNR) values were also added in the designed generator. With the need of portability, high speed dynamic response, scalability and low power consumption for the system, field programmable gate array (FPGA) was chosen as hardware platform, and almost all the works, such as developing an algorithm for pulse waveform and interfacing with memory and liquid crystal display (LCD), were implemented under the flow of system on a programmable chip (SOPC) development. When users input in the key parameters through LCD and touch screen, the corresponding pulse wave will be displayed on the LCD and the desired pulse waveform can be accessed from the analog output channel as well. The structure of the designed pulse wave generator is simple and it can provide accurate solutions for studying and teaching pulse waves and the detection of the equipments for acquisition and diagnosis of pulse wave.

  5. A study of the river velocity measurement techniques and analysis methods

    NASA Astrophysics Data System (ADS)

    Chung Yang, Han; Lun Chiang, Jie

    2013-04-01

    Velocity measurement technology can be traced back to the pitot tube velocity measurement method in the 18th century and today's velocity measurement technology use the acoustic and radar technology, with the Doppler principle developed technology advances, in order to develop the measurement method is more suitable for the measurement of velocity, the purpose is to get a more accurate measurement data and with the surface velocity theory, the maximum velocity theory and the indicator theory to obtain the mean velocity. As the main research direction of this article is to review the literature of the velocity measurement techniques and analysis methods, and to explore the applicability of the measurement method of the velocity measurement instruments, and then to describe the advantages and disadvantages of the different mean velocity profiles analysis method. Adequate review of the references of this study will be able to provide a reference for follow-up study of the velocity measurement. Review velocity measurement literature that different velocity measurement is required to follow the different flow conditions measured be upgraded its accuracy, because each flow rate measurement method has its advantages and disadvantages. Traditional velocity instrument can be used at low flow and RiverRAD microwave radar or imaging technology measurement method may be applied in high flow. In the tidal river can use the ADCP to quickly measure river vertical velocity distribution. In addition, urban rivers may be used the CW radar to set up on the bridge, and wide rivers can be used RiverRAD microwave radar to measure the velocities. Review the relevant literature also found that using Ultrasonic Doppler Current Profiler with the Chiu's theory to the velocity of observing automation work can save manpower and resources to improve measurement accuracy, reduce the risk of measurement, but the great variability of river characteristics in Taiwan and a lot of drifting floating

  6. Cosmological constraints from type ia supernovae peculiar velocity measurements.

    PubMed

    Gordon, C; Land, K; Slosar, A

    2007-08-24

    We detect the correlated peculiar velocities of nearby type Ia supernovae (SNe), while highlighting an error in some of the literature. We find sigma8 = 0.79 +/- 0.22 from SNe, and examine the potential of this method to constrain cosmological parameters in the future. We demonstrate that a survey of 300 low-z SNe (such as the nearby SNfactory) will underestimate the errors on w by approximately 35% if the coherent peculiar velocities are not included.

  7. General review of maximal aerobic velocity measurement at laboratory. Proposition of a new simplified protocol for maximal aerobic velocity assessment.

    PubMed

    Berthon, P; Fellmann, N

    2002-09-01

    The maximal aerobic velocity concept developed since eighties is considered as either the minimal velocity which elicits the maximal aerobic consumption or as the "velocity associated to maximal oxygen consumption". Different methods for measuring maximal aerobic velocity on treadmill in laboratory conditions have been elaborated, but all these specific protocols measure V(amax) either during a maximal oxygen consumption test or with an association of such a test. An inaccurate method presents a certain number of problems in the subsequent use of the results, for example in the elaboration of training programs, in the study of repeatability or in the determination of individual limit time. This study analyzes 14 different methods to understand their interests and limits in view to propose a general methodology for measuring V(amax). In brief, the test should be progressive and maximal without any rest period and of 17 to 20 min total duration. It should begin with a five min warm-up at 60-70% of the maximal aerobic power of the subjects. The beginning of the trial should be fixed so that four or five steps have to be run. The duration of the steps should be three min with a 1% slope and an increasing speed of 1.5 km x h(-1) until complete exhaustion. The last steps could be reduced at two min for a 1 km x h(-1) increment. The maximal aerobic velocity is adjusted in relation to duration of the last step.

  8. Calibration of Instruments for Measuring Wind Velocity and Direction

    NASA Technical Reports Server (NTRS)

    Vogler, Raymond D.; Pilny, Miroslav J.

    1950-01-01

    Signal Corps wind equipment AN/GMQ-1 consisting of a 3-cup anemometer and wind vane was calibrated for wind velocities from 1 to 200 miles per hour. Cup-shaft failure prevented calibration at higher wind velocities. The action of the wind vane was checked and found to have very poor directional accuracy below a velocity of 8 miles per hour. After shaft failure was reported to the Signal Corps, the cup rotors were redesigned by strengthening the shafts for better operation at high velocities. The anemometer with the redesigned cup rotors was recalibrated, but cup-shaft failure occurred again at a wind velocity of approximately 220 miles per hour. In the course of this calibration two standard generators were checked for signal output variation, and a wind-speed meter was calibrated for use with each of the redesigned cup rotors. The variation of pressure coefficient with air-flow direction at four orifices on a disk-shaped pitot head was obtained for wind velocities of 37.79 53.6, and 98.9 miles per hour. A pitot-static tube mounted in the nose of a vane was calibrated up to a dynamic pressure of 155 pounds per square foot, or approximately 256 miles per hour,

  9. Simultaneous velocity and concentration measurements of a turbulent jet mixing flow.

    PubMed

    Hu, Hui; Saga, Tetsuo; Kobayashi, Toshio; Taniguchi, Nobuyuki

    2002-10-01

    A method for the simultaneous measurement of velocity and passive scalar concentration fields by means of particle image velocimetry (PIV) and planar laser induced florescence (PLIF) techniques is described here. An application of the combined PIV-PLIF system is demonstrated by performing simultaneous velocity and concentration measurements in the near field of a turbulent jet mixing flow. The distributions of the ensemble-averaged velocity and concentration, turbulent velocity fluctuation, concentration standard deviation, and the correlation terms between the fluctuating velocities and concentration in the near field of the turbulent jet flow are presented as the measurement results of the simultaneous PIV-PLIF system.

  10. Video measurement of the muzzle velocity of a potato gun

    NASA Astrophysics Data System (ADS)

    Jasperson, Christopher; Pollman, Anthony

    2011-09-01

    Using first principles, a theoretical equation for the maximum and actual muzzle velocities for a pneumatic cannon was recently derived. For a fixed barrel length, this equation suggests that the muzzle velocity can be enhanced by maximizing the product of the initial pressure and the volume of the propellant gas and decreasing the projectile mass. The present paper describes the results of experiments conducted to verify the validity of this theoretical equation. A high-speed video camera was used to quantify muzzle velocity for potatoes of varying mass exiting a pneumatic cannon for gauge pressures ranging from 310 to 830 kPa. The experiments verified that a friction modified version of the theoretical equation is qualitatively and quantitatively accurate for potato masses above 100 g.

  11. Frequency dependence of laser ultrasonic SAW phase velocities measurements.

    PubMed

    Li, Chunhui; Song, Shaozhen; Guan, Guangying; Wang, Ruikang K; Huang, Zhihong

    2013-01-01

    Advances in the field of laser ultrasonics have opened up new possibilities in applications in many areas. This paper verifies the relationship between phase velocities of different materials, including hard solid and soft solid, and the frequency range of SAW signal. We propose a novel approach that utilizes a low coherence interferometer to detect the laser-induced surface acoustic waves (SAWs). A Nd:YAG focused laser line-source is applied to steel, iron, plastic plates and a 3.5% agar-agar phantom. The generated SAW signals are detected by a time domain low coherence interferometry system. SAW phase velocity dispersion curves were calculated, from which the elasticity of the specimens was evaluated. The relationship between frequency content and phase velocities was analyzed. We show that the experimental results agreed well with those of the theoretical expectations.

  12. Optical fiber-based system for continuous measurement of in-bore projectile velocity

    NASA Astrophysics Data System (ADS)

    Wang, Guohua; Sun, Jinglin; Li, Qiang

    2014-08-01

    This paper reports the design of an optical fiber-based velocity measurement system and its application in measuring the in-bore projectile velocity. The measurement principle of the implemented system is based on Doppler effect and heterodyne detection technique. The analysis of the velocity measurement principle deduces the relationship between the projectile velocity and the instantaneous frequency (IF) of the optical fiber-based system output signal. To extract the IF of the fast-changing signal carrying the velocity information, an IF extraction algorithm based on the continuous wavelet transforms is detailed. Besides, the performance of the algorithm is analyzed by performing corresponding simulation. At last, an in-bore projectile velocity measurement experiment with a sniper rifle having a 720 m/s muzzle velocity is performed to verify the feasibility of the optical fiber-based velocity measurement system. Experiment results show that the measured muzzle velocity is 718.61 m/s, and the relative uncertainty of the measured muzzle velocity is approximately 0.021%.

  13. Optical fiber-based system for continuous measurement of in-bore projectile velocity.

    PubMed

    Wang, Guohua; Sun, Jinglin; Li, Qiang

    2014-08-01

    This paper reports the design of an optical fiber-based velocity measurement system and its application in measuring the in-bore projectile velocity. The measurement principle of the implemented system is based on Doppler effect and heterodyne detection technique. The analysis of the velocity measurement principle deduces the relationship between the projectile velocity and the instantaneous frequency (IF) of the optical fiber-based system output signal. To extract the IF of the fast-changing signal carrying the velocity information, an IF extraction algorithm based on the continuous wavelet transforms is detailed. Besides, the performance of the algorithm is analyzed by performing corresponding simulation. At last, an in-bore projectile velocity measurement experiment with a sniper rifle having a 720 m/s muzzle velocity is performed to verify the feasibility of the optical fiber-based velocity measurement system. Experiment results show that the measured muzzle velocity is 718.61 m/s, and the relative uncertainty of the measured muzzle velocity is approximately 0.021%.

  14. Continuous flow measurements using ultrasonic velocity meters - an update

    USGS Publications Warehouse

    Oltmann, Rick

    1995-01-01

    An article in the summer 1993 Newsletter described USGS work to continously monitor tidal flows in the delta using ultrasonic velocity meters.  This article updates progress since 1993, including new installations, results of data analysis, damage during this year's high flows, and the status of each site.

  15. Doppler velocity measurements using a phase-stabilized michelson spectrometer

    NASA Astrophysics Data System (ADS)

    Smeets, G.

    1993-10-01

    Laser Doppler systems have become classical means of nonintrusively recording velocities in all kinds of flow fields. With the system mostly used, the so-called Doppler differential velocimeter, tracer particles incorporated in the flow are illuminated by two laser beams from slightly different directions, and the velocity is derived from the beating frequency of the two scattered light waves on the cathode of a photomultiplier. As the intersecting beams form equidistant light sheets within the probe volume by their interference, it is desirable, as is the case with any technique creating light barriers in space, that particles should pass the grid individually. The particles should be of a suitable size: large enough to scatter sufficient light for a good signal-to-noise ratio but small enough for negligible velocity relaxation and true indication of the turbulent velocity fluctuations. In most applications of this technique, e.g. in wind tunnel experiments, particles of controlled size and number density are seeded into the upstream flow.

  16. Mathematical Relationships Between Two Sets of Laser Anemometer Measurements for Resolving the Total Velocity Vector

    NASA Technical Reports Server (NTRS)

    Owen, Albert K.

    1993-01-01

    The mathematical relations between the measured velocity fields for the same compressor rotor flow field resolved by two fringe type laser anemometers at different observational locations are developed in this report. The relations allow the two sets of velocity measurements to be combined to produce a total velocity vector field for the compressor rotor. This report presents the derivation of the mathematical relations, beginning with the specification of the coordinate systems and the velocity projections in those coordinate systems. The vector projections are then transformed into a common coordinate system. The transformed vector coordinates are then combined to determine the total velocity vector. A numerical example showing the solution procedure is included.

  17. MR measurement of cerebrospinal fluid velocity wave speed in the spinal canal.

    PubMed

    Kalata, Wojciech; Martin, Bryn A; Oshinski, John N; Jerosch-Herold, Michael; Royston, Thomas J; Loth, Francis

    2009-06-01

    Noninvasive measurement of the speed with which the cerebrospinal fluid (CSF) velocity wave travels through the spinal canal is of interest as a potential indicator of CSF system pressure and compliance, both of which may play a role in the development of craniospinal diseases. However, measurement of CSF velocity wave speed (VWS) has eluded researchers primarily due to either a lack of access to CSF velocity measurements or poor temporal resolution. Here, we present a CSF VWS measurement methodology using a novel MR sequence that acquires unsteady velocity measurements during the cardiac cycle with a time interval < 10 ms. Axial CSF velocity measurements were obtained in the sagittal plane of the cervical spinal region on three subjects referred for an MRI scan without craniospinal disorders. CSF VWS was estimated by using the time shift identified by the maximum velocity and maximum temporal velocity gradient during the cardiac cycle. Based on the maximum velocity gradient, the mean VWS in the three cases was calculated to be 4.6 m/s (standard deviation 1.7 m/s, p < 0.005) during systolic acceleration. VWS computed using maximum velocity alone was not statistically significant for any of the three cases. The measurements of VWS are close in magnitude to previously published values. The methodology represents a new technique that can be used to measure VWS in the spinal canal noninvasively. Further research is required to both validate the measurements and determine clinical significance.

  18. Laser Doppler velocity measurement without directional ambiguity by using frequency shifted incident beams

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.

    1970-01-01

    Laser Doppler heterodyning system for velocity measurements without directional ambiguity, employing incident beams of different frequencies through rotating diffraction grating or Bragg cell application

  19. Ultrasonic velocity and attenuation measurements at the metamagnetic transition in UPt3

    NASA Astrophysics Data System (ADS)

    Lin, S. W.; Kouroudis, I.; Jansen, A. G. M.; Wyder, P.; Luthi, B.; Hinks, D. G.; Ketterson, J. B.; Levy, M.; Sarma, Bimal K.

    1995-11-01

    The longitudinal ultrasonic attenuation and velocity were measured on a single crystal of UPt3 in a high magnetic field of up to 23T. Earlier ultrasonic measurements had seen a softening of the lattice as evidenced by a huge drop in the velocity at a field of 20T. Both the attenuation and velocity have been measured in field sweeps. Accompanying the large dip in the velocity is a large attenuation peak at this metamagnetic transition. Measurements were also done at several frequencies.

  20. STARSPOT JITTER IN PHOTOMETRY, ASTROMETRY, AND RADIAL VELOCITY MEASUREMENTS

    SciTech Connect

    Makarov, V. V.; Beichman, C. A.; Lebreton, J.; Malbet, F.; Catanzarite, J. H.; Shao, M.; Fischer, D. A.

    2009-12-10

    Analytical relations are derived for the amplitude of astrometric, photometric, and radial velocity (RV) perturbations caused by a single rotating spot. The relative power of the starspot jitter is estimated and compared with the available data for kappa{sup 1} Ceti and HD 166435, as well as with numerical simulations for kappa{sup 1} Ceti and the Sun. A Sun-like star inclined at i = 90 deg. at 10 pc is predicted to have an rms jitter of 0.087 muas in its astrometric position along the equator, and 0.38 m s{sup -1} in radial velocities. If the presence of spots due to stellar activity is the ultimate limiting factor for planet detection, the sensitivity of SIM Lite to Earth-like planets in habitable zones is about an order of magnitude higher than the sensitivity of prospective ultra-precise RV observations of nearby stars.

  1. Measuring In-Situ Mdf Velocity Of Detonation

    DOEpatents

    Horine, Frank M.; James, Jr., Forrest B.

    2005-10-25

    A system for determining the velocity of detonation of a mild detonation fuse mounted on the surface of a device includes placing the device in a predetermined position with respect to an apparatus that carries a couple of sensors that sense the passage of a detonation wave at first and second spaced locations along the fuse. The sensors operate a timer and the time and distance between the locations is used to determine the velocity of detonation. The sensors are preferably electrical contacts that are held spaced from but close to the fuse such that expansion of the fuse caused by detonation causes the fuse to touch the contact, causing an electrical signal to actuate the timer.

  2. New measurements of radial velocities in clusters of galaxies. II

    NASA Astrophysics Data System (ADS)

    Proust, D.; Mazure, A.; Sodre, L.; Capelato, H.; Lund, G.

    1988-03-01

    Heliocentric radial velocities are determined for 100 galaxies in five clusters, on the basis of 380-518-nm observations obtained using a CCD detector coupled by optical fibers to the OCTOPUS multiobject spectrograph at the Cassegrain focus of the 3.6-m telescope at ESO La Silla. The data-reduction procedures and error estimates are discussed, and the results are presented in tables and graphs and briefly characterized.

  3. Measurements of atomic beam velocities with phase choppers and precision measurements of alkali atomic polarizabilities

    NASA Astrophysics Data System (ADS)

    Hromada, Ivan, Jr.

    Atom interferometers, in which de Broglie waves are coherently split and recombined to make interference fringes, now serve as precision measurement tools for several quantities in physics. Examples include measurements of Newton's constant, the fine structure constant, van der Waals potentials, and atomic polarizabilities. To make next-generation measurements of static electric dipole atomic polarizabilities with an atom beam interferometer, I worked on new methods to precisely measure the velocity distribution for atom beams. I will explain how I developed and used phase choppers to measure lithium, sodium, potassium, and cesium atomic beam velocities with 0.07% accuracy. I also present new measurements of polarizability for these atoms. I classify systematic errors into two broad categories: (1) fractional errors that are similar for all different types of atoms in our experiments, and (2), errors that scale with de Broglie wavelength or inverse atomic momentum in our experiments. This distinction is important for estimating the uncertainty in our measurements of ratios of atomic polarizabilities, e.g., alpha Cs/alphaNa = 2.488(12).

  4. Bulk velocity measurements by video analysis of dye tracer in a macro-rough channel

    NASA Astrophysics Data System (ADS)

    Ghilardi, T.; Franca, M. J.; Schleiss, A. J.

    2014-03-01

    Steep mountain rivers have hydraulic and morphodynamic characteristics that hinder velocity measurements. The high spatial variability of hydraulic parameters, such as water depth (WD), river width and flow velocity, makes the choice of a representative cross-section to measure the velocity in detail challenging. Additionally, sediment transport and rapidly changing bed morphology exclude the utilization of standard and often intrusive velocity measurement techniques. The limited technical choices are further reduced in the presence of macro-roughness elements, such as large, relatively immobile boulders. Tracer tracking techniques are among the few reliable methods that can be used under these conditions to evaluate the mean flow velocity. However, most tracer tracking techniques calculate bulk flow velocities between two or more fixed cross-sections. In the presence of intense sediment transport resulting in an important temporal variability of the bed morphology, dead water zones may appear in the few selected measurement sections. Thus a technique based on the analysis of an entire channel reach is needed in this study. A dye tracer measurement technique in which a single camcorder visualizes a long flume reach is described and developed. This allows us to overcome the problem of the presence of dead water zones. To validate this video analysis technique, velocity measurements were carried out on a laboratory flume simulating a torrent, with a relatively gentle slope of 1.97% and without sediment transport, using several commonly used velocity measurement instruments. In the absence of boulders, salt injections, WD and ultrasonic velocity profiler measurements were carried out, along with dye injection technique. When boulders were present, dye tracer technique was validated only by comparison with salt tracer. Several video analysis techniques used to infer velocities were developed and compared, showing that dye tracking is a valid technique for bulk velocity

  5. Embedded Fiber Optic Probes to Measure Detonation Velocities Using the Photonic Doppler Velocimeter

    SciTech Connect

    Hare, D E; Holtkamp, D B; Strand, O T

    2010-03-02

    Detonation velocities for high explosives can be in the 7 to 8 km/s range. Previous work has shown that these velocities may be measured by inserting an optical fiber probe into the explosive assembly and recording the velocity time history using a Fabry-Perot velocimeter. The measured velocity using this method, however, is the actual velocity multiplied times the refractive index of the fiber core, which is on the order of 1.5. This means that the velocimeter diagnostic must be capable of measuring velocities as high as 12 km/s. Until recently, a velocity of 12 km/s was beyond the maximum velocity limit of a homodyne-based velocimeter. The limiting component in a homodyne system is usually the digitizer. Recently, however, digitizers have come on the market with 20 GHz bandwidth and 50 GS/s sample rate. Such a digitizer coupled with high bandwidth detectors now have the total bandwidth required to make velocity measurements in the 12 km/s range. This paper describes measurements made of detonation velocities using a high bandwidth homodyne system.

  6. Non-Invasive Pulse Wave Analysis in a Thrombus-Free Abdominal Aortic Aneurysm after Implantation of a Nitinol Aortic Endograft

    PubMed Central

    Georgakarakos, Efstratios; Argyriou, Christos; Georgiadis, George S.; Lazarides, Miltos K.

    2016-01-01

    Endovascular aneurysm repair has been associated with changes in arterial stiffness, as estimated by pulse wave velocity (PWV). This marker is influenced by the medical status of the patient, the elastic characteristics of the aneurysm wall, and the presence of intraluminal thrombus. Therefore, in order to delineate the influence of the endograft implantation in the early post-operative period, we conducted non-invasively pulse wave analysis in a male patient with an abdominal aortic aneurysm containing no intraluminal thrombus, unremarkable past medical history, and absence of peripheral arterial disease. The estimated parameters were the systolic and diastolic pressure calculated at the aortic level (central pressures), PWV, augmentation pressure (AP) and augmentation index (AI), pressure wave reflection magnitude (RM), and peripheral resistance. Central systolic and diastolic pressure decreased post-operatively. PWV showed subtle changes from 11.6 to 10.6 and 10.9 m/s at 1-week and 1-month, respectively. Accordingly, the AI decreased from 28 to 14% and continued to drop to 25%. The AP decreased gradually from 15 to 6 and 4 mmHg. The wave RM dropped from 68 to 52% at 1-month. Finally, the peripheral resistance dropped from 1.41 to 0.99 and 0.85 dyn × s × cm−5. Our example shows that the implantation of an aortic endograft can modify the pressure wave reflection over the aortic bifurcation without causing significant alterations in PWV. PMID:26793712

  7. Spray drop size and velocity measurements using the Phase/Doppler Particle Analyzer

    NASA Technical Reports Server (NTRS)

    Bachalo, W. D.; Houser, M. J.

    1987-01-01

    Detailed measurements of the drop size and velocity distributions were obtained for a swirl chamber pressure atomizer. These data were obtained with the Phase/Doppler Particle Analyzer manufactured by Aerometrics, Inc. Direct measurements of the size distributions revealed the evolving characteristics of the spray. Size velocity correlations were used to evaluate the effect of velocity relaxation on the size distributions. The simultaneous measurement of drop size and velocity was of major importance in accurately describing the changes in the local drop size distributions and mass flux.

  8. Measurement of shear-wave velocity by ultrasound critical-angle reflectometry (UCR)

    NASA Technical Reports Server (NTRS)

    Mehta, S.; Antich, P.; Blomqvist, C. G. (Principal Investigator)

    1997-01-01

    There exists a growing body of research that relates the measurement of pressure-wave velocity in bone to different physiological conditions and treatment modalities. The shear-wave velocity has been less studied, although it is necessary for a more complete understanding of the mechanical properties of bone. Ultrasound critical-angle reflectometry (UCR) is a noninvasive and nondestructive technique previously used to measure pressure-wave velocities both in vitro and in vivo. This note describes its application to the measurement of shear-wave velocity in bone, whether directly accessible or covered by soft tissue.

  9. Speckle correlation method used to measure object's in-plane velocity.

    PubMed

    Smíd, Petr; Horváth, Pavel; Hrabovský, Miroslav

    2007-06-20

    We present a measurement of an object's in-plane velocity in one direction by the use of the speckle correlation method. Numerical correlations of speckle patterns recorded periodically during motion of the object under investigation give information used to evaluate the object's in-plane velocity. The proposed optical setup uses a detection plane in the image field and enables one to detect the object's velocity within the interval (10-150) microm x s(-1). Simulation analysis shows a way of controlling the measuring range. The presented theory, simulation analysis, and setup are verified through an experiment of measurement of the velocity profile of an object.

  10. Speckle correlation method used to measure object's in-plane velocity

    SciTech Connect

    Schmid, Petr; Horvath, Pavel; Hrabovsky, Miroslav

    2007-06-20

    We present a measurement of an object's in-plane velocity in onedirection by the use of the speckle correlation method. Numerical correlationsof speckle patterns recorded periodically during motion of the object underinvestigation give information used to evaluate the object's in-plane velocity.The proposed optical setup uses a detection plane in the image field and enablesone to detect the object's velocity within the interval(10-150) {mu}m ? s-1.Simulation analysis shows a way of controlling the measuring range. Thepresented theory, simulation analysis, and setup are verified through anexperiment of measurement of the velocity profile of an object.

  11. Measurement of velocity of air flow in the sinus maxillaris.

    PubMed

    Müsebeck, K; Rosenberg, H

    1979-03-01

    Anemometry with the hot wire and hot film technique previously described, enables the rhinologist to record slow and rapidly changing air flow in the maxillary sinus. The advantages and disadvantages of this method are considered. Anemometry together with manometry may be designated sinumetry and used as a diagnostic procedure following sinuscopy in chronic maxillary sinus disease. The value of the function from velocity of time allows the estimation of flow-volume in the sinus. Furthermore, the method is useful to evaluate the optimal therapy to restore ventilation in the case of an obstructed ostium demonstrated before and after surgical opening in the inferior meatus.

  12. Velocity measurements of low Reynolds number tube flow using fiber-optic technology

    SciTech Connect

    Bianchi, J. Christopher

    1993-03-01

    In 1988 Nielsen started work to measure the spatial variability of the mass flux vector being transported in a porous medium. To measure the spatial variability of the mass flux vector, the spatial variability of its components(velocity, concentration) must be measured. Nielsen was successful in measuring the pore level concentration at many different pores and in verifying the assumption that a nonuniform concentration field exists within the mixing zone between two miscible fluids. However, Nielsen was unable to conduct the necessary pore level velocity measurements needed. Nielsen`s work is being continued and a probe is being developed that will measure both velocity and concentration components at pore level. The probe is essentially the same probe used to make the pore level concentration measurements with added capabilities needed to make the velocity measurements. This probe has several design variables, dealing primarily with the velocity component, that need further investigation. The research presented in this thesis investigates these parameters by performing experiments in a capillary tube. The tube is a controlled system where the velocity of the fluid can be determined from the volumetric flow rate using Poiseuille`s solution for viscous flow. Also, a statistically based relationship between the velocity measured with the probe and the velocity determined from the volumetric flow rate has been developed.

  13. Velocity measurements of low Reynolds number tube flow using fiber-optic technology

    SciTech Connect

    Bianchi, J.C.

    1993-03-01

    In 1988 Nielsen started work to measure the spatial variability of the mass flux vector being transported in a porous medium. To measure the spatial variability of the mass flux vector, the spatial variability of its components(velocity, concentration) must be measured. Nielsen was successful in measuring the pore level concentration at many different pores and in verifying the assumption that a nonuniform concentration field exists within the mixing zone between two miscible fluids. However, Nielsen was unable to conduct the necessary pore level velocity measurements needed. Nielsen's work is being continued and a probe is being developed that will measure both velocity and concentration components at pore level. The probe is essentially the same probe used to make the pore level concentration measurements with added capabilities needed to make the velocity measurements. This probe has several design variables, dealing primarily with the velocity component, that need further investigation. The research presented in this thesis investigates these parameters by performing experiments in a capillary tube. The tube is a controlled system where the velocity of the fluid can be determined from the volumetric flow rate using Poiseuille's solution for viscous flow. Also, a statistically based relationship between the velocity measured with the probe and the velocity determined from the volumetric flow rate has been developed.

  14. Calibration of a system for measuring low air flow velocity in a wind tunnel

    NASA Astrophysics Data System (ADS)

    Krach, Andrzej; Kruczkowski, Janusz

    2016-08-01

    This article presents the calibration of a system for measuring air flow velocity in a wind tunnel with a multiple-hole orifice. The comparative method was applied for the calibration. The method consists in equalising the air flow velocity in a test section of the tunnel with that of the hot-wire anemometer probe which should then read zero value. The hot-wire anemometer probe moves reciprocally in the tunnel test section with a constant velocity, aligned and opposite to the air velocity. Air velocity in the tunnel test section is adjusted so that the minimum values of a periodic hot-wire anemometer signal displayed on an oscilloscope screen reach the lowest position (the minimum method). A sinusoidal component can be superimposed to the probe constant velocity. Then, the air flow velocity in the tunnel test section is adjusted so that, when the probe moves in the direction of air flow, only the second harmonic of the periodically variable velocity superimposed on the constant velocity (second harmonic method) remains at the output of the low-pass filter to which the hot-wire anemometer signal, displayed on the oscilloscope screen, is supplied. The velocity of the uniform motion of the hot-wire anemometer probe is measured with a magnetic linear encoder. The calibration of the system for the measurement of low air velocities in the wind tunnel was performed in the following steps: 1. Calibration of the linear encoder for the measurement of the uniform motion velocity of the hot-wire anemometer probe in the test section of the tunnel. 2. Calibration of the system for measurement of low air velocities with a multiple-hole orifice for the velocities of 0.1 and 0.25 m s-1: - (a) measurement of the probe movement velocity setting; - (b) measurement of air velocity in the tunnel test section with comparison according to the second harmonic method; - (c) measurement of air velocity in the tunnel with comparison according to the minimum method. The calibration

  15. Development of ultrasonic pulse-train Doppler method for velocity profile and flowrate measurement

    NASA Astrophysics Data System (ADS)

    Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

    2016-11-01

    We present a novel technique for measuring the velocity profile and flowrate in a pipe. This method, named the ultrasonic pulse-train Doppler method (UPTD), has the advantages of expanding the velocity range and setting the smaller measurement volume with low calculation and instrument costs in comparison with the conventional ultrasonic pulse Doppler method. The conventional method has limited measurement of the velocity range due to the Nyquist sampling theorem. In addition, previous reports indicate that a smaller measurement volume increases the accuracy of the measurement. In consideration of the application of the conventional method to actual flow fields, such as industrial facilities and power plants, the issues of velocity range and measurement volume are important. The UPTD algorithm, which exploits two pulses of ultrasound with a short interval and envelope detection, is proposed. Velocity profiles calculated by this algorithm were examined through simulations and excellent agreement was found in all cases. The influence of the signal-to-noise ratio (SNR) on the algorithm was also estimated. The result indicates that UPTD can measure velocity profiles with high accuracy, even under a small SNR. Experimental measurements were conducted and the results were evaluated at the national standard calibration facility of water flowrate in Japan. Every detected signal forms a set of two pulses and the enveloped line can be observed clearly. The results show that UPTD can measure the velocity profiles over the pipe diameter, even if the velocities exceed the measurable velocity range. The measured flowrates were under 0.6% and the standard deviations for all flowrate conditions were within  ±0.38%, which is the uncertainty of the flowrate measurement estimated in the previous report. In conclusion, UPTD provides superior accuracy and expansion of the velocity range.

  16. Two-dimensional time resolved measurements of toroidal velocity correlated with density blobs in magnetized plasmas

    SciTech Connect

    Labit, B.; Furno, I.; Fasoli, A.; Podesta, M.

    2008-08-15

    A new method for toroidal velocity measurements with Mach probes is presented. This technique is based on the conditional sampling technique, the triggering events being density blobs. A reconstruction of the time resolved two-dimensional profile of electron density, electron temperature, plasma potential, and toroidal velocity is possible with a single point measurement on a shot-to-shot basis.

  17. Method of optical self-mixing for pulse wave transit time in comparison with other methods and correlation with blood pressure

    NASA Astrophysics Data System (ADS)

    Meigas, Kalju; Lass, Jaanus; Kattai, Rain; Karai, Deniss; Kaik, Juri

    2004-07-01

    This paper is a part of research to develop convenient method for continuous monitoring of arterial blood pressure by non-invasive and non-oscillometric way. A simple optical method, using self-mixing in a diode laser, is used for detection of skin surface vibrations near the artery. These vibrations, which can reveal the pulsate propagation of blood pressure waves along the vasculature, are used for pulse wave registration. The registration of the Pulse Wave Transit Time (PWTT) is based on computing the time delay in different regions of the human body using an ECG as a reference signal. In this study, the comparison of method of optical self-mixing with other methods as photoplethysmographic (PPG) and bioimpedance (BI) for PWTT is done. Also correlation of PWTT, obtained with different methods, with arterial blood pressure is calculated. In our study, we used a group of volunteers (34 persons) who made the bicycle exercise test. The test consisted of cycling sessions of increasing workloads during which the HR changed from 60 to 180 beats per minute. In addition, a blood pressure (NIBP) was registered with standard sphygmomanometer once per minute during the test and all NIBP measurement values were synchronized to other signals to find exact time moments where the systolic blood pressure was detected (Korotkoff sounds starting point). Computer later interpolated the blood pressure signal in order to get individual value for every heart cycle. The other signals were measured continuously during all tests. At the end of every session, a recovery period was included until person's NIBP and heart rate (HR) normalized. As a result of our study it turned out that time intervals that were calculated from plethysmographic (PPG) waveforms were in the best correlation with systolic blood pressure. The diastolic pressure does not correlate with any of the parameters representing PWTT. The pulse wave signals measured by laser and piezoelectric transducer are very similar

  18. Errors in acoustic doppler profiler velocity measurements caused by flow disturbance

    USGS Publications Warehouse

    Mueller, D.S.; Abad, J.D.; Garcia, C.M.; Gartner, J.W.; Garcia, M.H.; Oberg, K.A.

    2007-01-01

    Acoustic Doppler current profilers (ADCPs) are commonly used to measure streamflow and water velocities in rivers and streams. This paper presents laboratory, field, and numerical model evidence of errors in ADCP measurements caused by flow disturbance. A state-of-the-art three-dimensional computational fluid dynamic model is validated with and used to complement field and laboratory observations of flow disturbance and its effect on measured velocities. Results show that near the instrument, flow velocities measured by the ADCP are neither the undisturbed stream velocity nor the velocity of the flow field around the ADCP. The velocities measured by the ADCP are biased low due to the downward flow near the upstream face of the ADCP and upward recovering flow in the path of downstream transducer, which violate the flow homogeneity assumption used to transform beam velocities into Cartesian velocity components. The magnitude of the bias is dependent on the deployment configuration, the diameter of the instrument, and the approach velocity, and was observed to range from more than 25% at 5cm from the transducers to less than 1% at about 50cm from the transducers for the scenarios simulated. ?? 2007 ASCE.

  19. Experimental Acoustic Velocity Measurements in a Tidally Affected Stream

    USGS Publications Warehouse

    Storm, J.B.; ,

    2002-01-01

    The U.S. Geological Survey (USGS) constructed a continuous steamgaging station on the tidally affected Escatawpa River at Interstate 10 near Orange Grove, Mississippi, in August 2001. The gage collects water quantity parameters of stage and stream velocity, and water quality parameters of water temperature, specific conductance, and salinity. Data are transmitted to the local USGS office via the GOES satellite and are presented on a near real-time web page. Due to tidal effects, the stream has multiple flow regimes which include downstream, bi-directional, and reverse flows. Advances in acoustic technology have made it possible to gage streams of this nature where conventional methods have been unsuccessful. An experimental mount was designed in an attempt to recognize, describe, and quantify these flow regimes by using acoustic Doppler equipment.

  20. A Device for Measuring Sonic Velocity and Compressor Mach Number

    DTIC Science & Technology

    1948-07-01

    resonator (the only 4 NACA TN No. 1664 accurate measurement required) is measured, as shomn in figure 1, by means of a mercury manometer . The compressor Mach...tube vs not connected to the ccmpressor inlet until after calibration. The pressure in the device was measured by means of the mercury manometer . Fram

  1. Surface recombination velocity and lifetime in InP measured by transient microwave reflectance

    NASA Technical Reports Server (NTRS)

    Bothra, S.; Tyagi, S. D.; Ghandhi, S. K.; Borrego, J. M.

    1990-01-01

    Minority carrier lifetime and surface recombination velocity are determined in organometallic vapor-phase epitaxy (OMVPE)-grown InP by a contactless microwave technique. For lightly doped n-type InP, a surface recombination velocity of 5000 cm/s is measured. However, in solar cells with a heavily doped n-type emitter a surface recombination velocity of 1 x 10 to the 6th cm/s is observed. Possible reasons for this due to surface pinning are discussed. The effects of various chemical treatments and SiO on the surface recombination velocity are measured.

  2. Pulse transit time differential measurement by fiber Bragg grating pulse recorder.

    PubMed

    Umesh, Sharath; Padma, Srivani; Ambastha, Shikha; Kalegowda, Anand; Asokan, Sundarrajan

    2015-05-01

    The present study reports a noninvasive technique for the measurement of the pulse transit time differential (PTTD) from the pulse pressure waveforms obtained at the carotid artery and radial artery using fiber Bragg grating pulse recorders (FBGPR). PTTD is defined as the time difference between the arrivals of a pulse pressure waveform at the carotid and radial arterial sites. The PTTD is investigated as an indicator of variation in the systolic blood pressure. The results are validated against blood pressure variation obtained from a Mindray Patient Monitor. Furthermore, the pulse wave velocity computed from the obtained PTTD is compared with the pulse wave velocity obtained from the color Doppler ultrasound system and is found to be in good agreement. The major advantage of the PTTD measurement via FBGPRs is that the data acquisition system employed can simultaneously acquire pulse pressure waveforms from both FBGPRs placed at carotid and radial arterial sites with a single time scale, which eliminates time synchronization complexity.

  3. Intracavity Rayleigh/Mie Scattering for Multipoint, Two-Component Velocity Measurement

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel; Danehy, Paul M.; Lee, Joseph W.

    2006-01-01

    A simultaneous multi-point two-component Doppler velocimeter is described. The system uses two optical cavities: a Fabry-Perot etalon and an optical cavity for collecting and re-circulating the Rayleigh/Mie scattered light that is collected from the measurement volume in two parallel, but opposite directions. Single-pulse measurements of two orthogonal components of the velocity vector in a supersonic free jet were performed to demonstrate the technique. The re-circulation of the light rejected by the interferometer input mirror also increased the signal intensity by a factor of 3.5. 2005 Optical Society of America Interferometric Rayleigh scattering has previously been used for single-point velocity measurements in unseeded gas flow. However, this past work has generally been limited to probing with continuous-wave lasers resulting in time-averaged measurements of velocity. Multiple velocity components have been measured simultaneously by separate instruments.1,2 It has also been demonstrated that two orthogonal velocity components can be measured simultaneously at one point using one interferometer by reflecting back the probing laser beam, although this approach results in directional ambiguity of the flow velocity vector.3 This measurement ambiguity was removed by prior knowledge of the approximate magnitude and sign of the velocity components. Furthermore, it was shown that multiple points could be measured simultaneously with a Rayleigh scattering interferometric approach, but only one component of velocity was measured.4 Another method of performing multiple component velocity measurements with Rayleigh scattering uses a pair of cameras to image the flow, one of which views the flow through an iodine gas filter. This iodine-filter technique has the advantage of allowing high-resolution velocity imaging, but it generally has a lower dynamic range.

  4. Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cantrell, John H.; Kushnick, Peter W.

    1991-01-01

    A new instrument based on a constant-frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonic wave velocity in liquids and changes in ultrasonic wave velocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques. Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measure velocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10 to the 7th.

  5. Laser-Induced Fluorescence Velocity Measurements in Supersonic Underexpanded Impinging Jets

    NASA Technical Reports Server (NTRS)

    Inman, Jennifer A.; Danehy, Paul M.; Barthel, Brett; Alderfer, David W.; Novak, Robert J.

    2010-01-01

    We report on an application of nitric oxide (NO) flow-tagging velocimetry to impinging underexpanded jet flows issuing from a Mach 2.6 nozzle. The technique reported herein utilizes a single laser, single camera system to obtain planar maps of the streamwise component of velocity. Whereas typical applications of this technique involve comparing two images acquired at different time delays, this application uses a single image and time delay. The technique extracts velocity by assuming that particular regions outside the jet flowfield have negligible velocity and may therefore serve as a stationary reference against which to measure motion of the jet flowfield. By taking the average of measurements made in 100 single-shot images for each flow condition, streamwise velocities of between -200 and +1,000 m/s with accuracies of between 15 and 50 m/s are reported within the jets. Velocity measurements are shown to explain otherwise seemingly anomalous impingement surface pressure measurements.

  6. Seismic Velocity Measurements at Expanded Seismic Network Sites

    SciTech Connect

    Woolery, Edward W; Wang, Zhenming

    2005-01-01

    Structures at the Paducah Gaseous Diffusion Plant (PGDP), as well as at other locations in the northern Jackson Purchase of western Kentucky may be subjected to large far-field earthquake ground motions from the New Madrid seismic zone, as well as those from small and moderate-sized local events. The resultant ground motion a particular structure is exposed from such event will be a consequence of the earthquake magnitude, the structures' proximity to the event, and the dynamic and geometrical characteristics of the thick soils upon which they are, of necessity, constructed. This investigation evaluated the latter. Downhole and surface (i.e., refraction and reflection) seismic velocity data were collected at the Kentucky Seismic and Strong-Motion Network expansion sites in the vicinity of the Paducah Gaseous Diffusion Plant (PGDP) to define the dynamic properties of the deep sediment overburden that can produce modifying effects on earthquake waves. These effects are manifested as modifications of the earthquake waves' amplitude, frequency, and duration. Each of these three ground motion manifestations is also fundamental to the assessment of secondary earthquake engineering hazards such as liquefaction.

  7. Optimization of an algorithm for measurements of velocity vector components using a three-wire sensor.

    PubMed

    Ligeza, P; Socha, K

    2007-10-01

    Hot-wire measurements of velocity vector components use a sensor with three orthogonal wires, taking advantage of an anisotropic effect of wire sensitivity. The sensor is connected to a three-channel anemometric circuit and a data acquisition and processing system. Velocity vector components are obtained from measurement signals, using a modified algorithm for measuring velocity vector components enabling the minimization of measurement errors described in this paper. The standard deviation of the relative error was significantly reduced in comparison with the classical algorithm.

  8. Electronic frequency modulation for the increase of maximum measurable velocity in a heterodyne laser interferometer

    SciTech Connect

    Choi, Hyunseung; La, Jongpil; Park, Kyihwan

    2006-10-15

    A Zeeman-type He-Ne laser is frequently used as a heterodyne laser due to the simple construction and the small loss of a light. However, the low beat frequency of the Zeeman-type laser limits the maximum measurable velocity. In this article, an electronic frequency modulation algorithm is proposed to overcome the drawback of the low velocity measurement capability by increasing the beat frequency electronically. The brief analysis, the measurement scheme of the proposed algorithm, and the experimental results are presented. It is demonstrated that the proposed algorithm is proven to enhance the maximum measurable velocity.

  9. Laser transit anemometer measurements of a JANNAF nozzle base velocity flow field

    NASA Technical Reports Server (NTRS)

    Hunter, William W., Jr.; Russ, C. E., Jr.; Clemmons, J. I., Jr.

    1990-01-01

    Velocity flow fields of a nozzle jet exhausting into a supersonic flow were surveyed. The measurements were obtained with a laser transit anemometer (LTA) system in the time domain with a correlation instrument. The LTA data is transformed into the velocity domain to remove the error that occurs when the data is analyzed in the time domain. The final data is shown in velocity vector plots for positions upstream, downstream, and in the exhaust plane of the jet nozzle.

  10. Measurement of rectus femoris muscle velocities during patellar tendon jerk using vector tissue doppler imaging.

    PubMed

    Sikdar, Siddhartha; Lebiedowska, Maria; Eranki, Avinash; Garmirian, Lindsay; Damiano, Diane

    2009-01-01

    We have developed a vector tissue Doppler imaging (TDI) system based on a clinical scanner that can be used to measure muscle velocities independent of the direction of motion. This method overcomes the limitations of conventional Doppler ultrasound, which can only measure velocity components along the ultrasound beam. In this study, we utilized this method to investigate the rectus femoris muscle velocities during a patellar tendon jerk test. Our goal was to investigate whether the muscle elongation velocities during a brisk tendon tap fall within the normal range of velocities that are expected due to rapid stretch of limb segments. In a preliminary study, we recruited six healthy volunteers (three men and three women) following informed consent. The stretch reflex response to tendon tap was evaluated by measuring: (1) the tapping force using an accelerometer instrumented to the neurological hammer (2) the angular velocities of the knee extension and flexion using a electrogoniometer (3) reflex activation using electromyography (EMG) and (4) muscle elongation, extension and flexion velocities using vector TDI. The passive joint angular velocity was linearly related to the passive muscle elongation velocity (R(2)=0.88). The maximum estimated joint angular velocity corresponding to muscle elongation due to tendon tap was less than 8.25 radians/s. This preliminary study demonstrates the feasibility of vector TDI for measuring longitudinal muscle velocities and indicates that the muscle elongation velocities during a clinical tendon tap test are within the normal range of values for rapid limb stretch encountered in daily life. With further refinement, vector TDI could become a powerful method for quantitative evaluation of muscle motion in musculoskeletal disorders.

  11. High precision UTDR measurements by sonic velocity compensation with reference transducer.

    PubMed

    Stade, Sam; Kallioinen, Mari; Mänttäri, Mika; Tuuva, Tuure

    2014-07-02

    An ultrasonic sensor design with sonic velocity compensation is developed to improve the accuracy of distance measurement in membrane modules. High accuracy real-time distance measurements are needed in membrane fouling and compaction studies. The benefits of the sonic velocity compensation with a reference transducer are compared to the sonic velocity calculated with the measured temperature and pressure using the model by Belogol'skii, Sekoyan et al. In the experiments the temperature was changed from 25 to 60 °C at pressures of 0.1, 0.3 and 0.5 MPa. The set measurement distance was 17.8 mm. Distance measurements with sonic velocity compensation were over ten times more accurate than the ones calculated based on the model. Using the reference transducer measured sonic velocity, the standard deviations for the distance measurements varied from 0.6 to 2.0 µm, while using the calculated sonic velocity the standard deviations were 21-39 µm. In industrial liquors, not only the temperature and the pressure, which were studied in this paper, but also the properties of the filtered solution, such as solute concentration, density, viscosity, etc., may vary greatly, leading to inaccuracy in the use of the Belogol'skii, Sekoyan et al. model. Therefore, calibration of the sonic velocity with reference transducers is needed for accurate distance measurements.

  12. Higher Resolution Neutron Velocity Spectrometer Measurements of Enriched Uranium

    DOE R&D Accomplishments Database

    Rainwater, L. J.; Havens, W. W. Jr.

    1950-08-09

    The slow neutron transmission of a sample of enriched U containing 3.193 gm/cm2 was investigated with a resolution width of 1 microsec/m. Results of transmission measurements are shown graphically. (B.J.H.)

  13. Predicting stroke outcome using DCE-CT measured blood velocity

    NASA Astrophysics Data System (ADS)

    Oosterbroek, Jaap; Bennink, Edwin; Dankbaar, Jan Willem; Horsch, Alexander D.; Viergever, Max A.; Velthuis, Birgitta K.; de Jong, Hugo W. A. M.

    2015-03-01

    CT plays an important role in the diagnosis of acute stroke patients. Dynamic contrast enhanced CT (DCE-CT) can estimate local tissue perfusion and extent of ischemia. However, hemodynamic information of the large intracranial vessels may also be obtained from DCE-CT data and may contain valuable diagnostic information. We describe a novel method to estimate intravascular blood velocity (IBV) in large cerebral vessels using DCE-CT data, which may be useful to help predict stroke outcome. DCE-CT scans from 34 patients with isolated M1 occlusions were included from a large prospective multi-center cohort study of patients with acute ischemic stroke. Gaussians fitted to the intravascular data yielded the time-to-peak (TTP) and cerebral-blood-volume (CBV). IBV was computed by taking the inverse of the TTP gradient magnitude. Voxels with a CBV of at least 10% of the CBV found in the arterial input function were considered part of a vessel. Mid-sagittal planes were drawn manually and averages of the IBV over all vessel-voxels (arterial and venous) were computed for each hemisphere. Mean-hemisphere IBV differences, mean-hemisphere TTP differences, and hemisphere vessel volume differences were used to differentiate between patients with good and bad outcome (modified Rankin Scale score <3 versus ≥3 at 90 days) using ROC analysis. AUCs from the ROC for IBV, TTP, and vessel volume were 0.80, 0.67 and 0.62 respectively. In conclusion, IBV was found to be a better predictor of patient outcome than the parameters used to compute it and may be a promising new parameter for stroke outcome prediction.

  14. A simple measuring technique of surface flow velocity to analyze the behavior of velocity fields in hydraulic engineering applications.

    NASA Astrophysics Data System (ADS)

    Tellez, Jackson; Gomez, Manuel; Russo, Beniamino; Redondo, Jose M.

    2015-04-01

    An important achievement in hydraulic engineering is the proposal and development of new techniques for the measurement of field velocities in hydraulic problems. The technological advances in digital cameras with high resolution and high speed found in the market, and the advances in digital image processing techniques now provides a tremendous potential to measure and study the behavior of the water surface flows. This technique was applied at the Laboratory of Hydraulics at the Technical University of Catalonia - Barcelona Tech to study the 2D velocity fields in the vicinity of a grate inlet. We used a platform to test grate inlets capacity with dimensions of 5.5 m long and 4 m wide allowing a zone of useful study of 5.5m x 3m, where the width is similar of the urban road lane. The platform allows you to modify the longitudinal slopes from 0% to 10% and transversal slope from 0% to 4%. Flow rates can arrive to 200 l/s. In addition a high resolution camera with 1280 x 1024 pixels resolution with maximum speed of 488 frames per second was used. A novel technique using particle image velocimetry to measure surface flow velocities has been developed and validated with the experimental data from the grate inlets capacity. In this case, the proposed methodology can become a useful tools to understand the velocity fields of the flow approaching the inlet where the traditional measuring equipment have serious problems and limitations. References DigiFlow User Guide. (2012), (June). Russo, B., Gómez, M., & Tellez, J. (2013). Methodology to Estimate the Hydraulic Efficiency of Nontested Continuous Transverse Grates. Journal of Irrigation and Drainage Engineering, 139(10), 864-871. doi:10.1061/(ASCE)IR.1943-4774.0000625 Teresa Vila (1), Jackson Tellez (1), Jesus Maria Sanchez (2), Laura Sotillos (1), Margarita Diez (3, 1), and J., & (1), M. R. (2014). Diffusion in fractal wakes and convective thermoelectric flows. Geophysical Research Abstracts - EGU General Assembly 2014

  15. Diagnostic value of mitral annular velocity for constrictive pericarditis in the absence of respiratory variation in mitral inflow velocity.

    PubMed

    Ha, Jong-Won; Oh, Jae K; Ommen, Steve R; Ling, Lieng H; Tajik, A Jamil

    2002-12-01

    Respiratory variation of 25% or more in transmitral early diastolic filling (E) velocity is a well-recognized diagnostic feature of constrictive pericarditis (CP) that is useful for distinguishing it from restrictive cardiomyopathy. However, a subset of patients with CP do not exhibit the typical respiratory change. Recent data showed that mitral annular (E') velocity measured by Doppler tissue echocardiography (DTE) is markedly reduced in patients with restrictive cardiomyopathy whereas E' velocity is well-preserved in CP. This study evaluated the role of DTE for the diagnosis of CP when there is no characteristic respiratory variation of E velocity. From September 1999 to March 2001, 19 patients (17 men, 2 women; mean age, 57 +/- 13 years) with surgically confirmed CP underwent comprehensive echocardiography preoperatively, including pulsed wave and DTE examination with simultaneous recording of respiration. Nine (47%) of the 19 patients had less than 25% respiratory variation in E velocity. There was no significant difference in mitral inflow peak velocity, deceleration time, early-to-late ventricular filling ratio, and E' velocity between patients with and patients without respiratory variation of E velocity of 25% or more. Regardless of the presence or absence of a significant respiratory variation of E velocity, E' velocity was relatively normal (mean, 12 +/- 4 cm/s) in all patients with CP. In conclusion, E' velocity is well preserved in patients with isolated CP even when there is no characteristic respiratory variation of E velocity. Thus, when the respiratory variation in Doppler E velocity is blunted or absent during the evaluation of suspected CP in patients with restrictive mitral inflow velocity, preserved E' velocity shown by DTE should support the diagnosis of CP over a primary myocardial disease.

  16. Measuring the velocity field from type Ia supernovae in an LSST-like sky survey

    NASA Astrophysics Data System (ADS)

    Odderskov, Io; Hannestad, Steen

    2017-01-01

    In a few years, the Large Synoptic Survey Telescope will vastly increase the number of type Ia supernovae observed in the local universe. This will allow for a precise mapping of the velocity field and, since the source of peculiar velocities is variations in the density field, cosmological parameters related to the matter distribution can subsequently be extracted from the velocity power spectrum. One way to quantify this is through the angular power spectrum of radial peculiar velocities on spheres at different redshifts. We investigate how well this observable can be measured, despite the problems caused by areas with no information. To obtain a realistic distribution of supernovae, we create mock supernova catalogs by using a semi-analytical code for galaxy formation on the merger trees extracted from N-body simulations. We measure the cosmic variance in the velocity power spectrum by repeating the procedure many times for differently located observers, and vary several aspects of the analysis, such as the observer environment, to see how this affects the measurements. Our results confirm the findings from earlier studies regarding the precision with which the angular velocity power spectrum can be determined in the near future. This level of precision has been found to imply, that the angular velocity power spectrum from type Ia supernovae is competitive in its potential to measure parameters such as σ8. This makes the peculiar velocity power spectrum from type Ia supernovae a promising new observable, which deserves further attention.

  17. A FBG pulse wave demodulation method based on PCF modal interference filter

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Xu, Shan; Shen, Ziqi; Zhao, Junfa; Miao, Changyun; Bai, Hua

    2016-10-01

    Fiber optic sensor embedded in textiles has been a new direction of researching smart wearable technology. Pulse signal which is generated by heart beat contains vast amounts of physio-pathological information about the cardiovascular system. Therefore, the research for textile-based fiber optic sensor which can detect pulse wave has far-reaching effects on early discovery and timely treatment of cardiovascular diseases. A novel wavelength demodulation method based on photonic crystal fiber (PCF) modal interference filter is proposed for the purpose of developing FBG pulse wave sensing system embedded in smart clothing. The mechanism of the PCF modal interference and the principle of wavelength demodulation based on In-line Mach-Zehnder interferometer (In-line MZI) are analyzed in theory. The fabricated PCF modal interferometer has the advantages of good repeatability and low temperature sensitivity of 3.5pm/°C from 25°C to 60°C. The designed demodulation system can achieve linear demodulation in the range of 2nm, with the wavelength resolution of 2.2pm and the wavelength sensitivity of 0.055nm-1. The actual experiments' result indicates that the pulse wave can be well detected by this demodulation method, which is in accordance with the commercial demodulation instrument (SM130) and more sensitive than the traditional piezoelectric pulse sensor. This demodulation method provides important references for the research of smart clothing based on fiber grating sensor embedded in textiles and accelerates the developments of wearable fiber optic sensors technology.

  18. Multipoint Vernier VISAR Interferometer System for Measuring Mass Velocity in Shock Wave Experiments

    NASA Astrophysics Data System (ADS)

    Gubskii, K. L.; Koshkin, D. S.; Mikhaylyuk, A. V.; Korolev, A. M.; Pirog, V. A.; Kuznetsov, A. P.

    The results of development of a laser interferometer designed to measure the mass velocity of condensed substances in shock wave experiments in the field of high energy density physics are presented. The developed laser system allows measurements of the velocity of free surfaces of samples in shockwave experiments with accuracy no worse than 10 m/s for the entire range of velocities attained experimentally. The time resolution of measurements is limited by the response speed of the used PMTs and amounts to 2.5 ns.

  19. A Tool and a Method for Obtaining Hydrologic Flow Velocity Measurements in Geothermal Reservoirs

    SciTech Connect

    Carrigan, C.R.; Dunn, J.C.; Hardee, H.C.

    1986-01-21

    Downhole instruments based on a thermal perturbation principle are being developed to measure heat flow in permeable formations where convective transport of heat is important. To make heat flow measurements in these regions, the ground water velocity vector must be determined. A downhole probe has been designed to measure the local ground water velocity vector. The probe is a cylindrical heat source operated at a constant heat flux. In a convecting environment, surface temperatures on the probe are perturbed from those values of a purely conductive environment. With the aid of analytical and numerical models, these temperature differences can be related to the local velocity vector.

  20. Tool and a method for obtaining hydrologic flow velocity measurements in geothermal reservoirs

    SciTech Connect

    Carrigan, C.R.; Dunn, J.C.; Hardee, H.C.

    1986-01-01

    Downhole instruments based on a thermal perturbation principle are being developed to measure heat flow in permeable formations where convective transport of heat is important. To make heat flow measurements in these regions, the ground water velocity vector must be determined. A downhole probe has been designed to measure the local ground water velocity vector. The probe is a cylindrical heat source operated at a constant heat flux. In a convecting environment, surface temperatures on the probe are perturbed from those values of a purely conductive environment. With the aid of analytical and numerical models, these temperature differences can be related to the local velocity vector. 4 refs., 2 figs.

  1. A Pedagogical Measurement of the Velocity of Light

    ERIC Educational Resources Information Center

    Tyler, Charles E.

    1969-01-01

    Describes an inexpensive, easily constructed device for demonstrating that the speed of light is finite, and for measuring its value. The main components are gallium arsenide light emitting diodes, a light pulser, transistors, and an oscilloscope. Detailed instructions of procedure and experimental results are given. (LC)

  2. Temperature Sensitive Particle for Velocity and Temperature Measurement.

    NASA Astrophysics Data System (ADS)

    Someya, Satoshi; Okamoto, Koji; Iida, Masao

    2007-11-01

    Phosphorescence and fluorescence are often applied to measure the temperature and the concentration of oxygen. The intensity and the lifetime of phosphor depend on the temperature and the oxygen concentration, due to the quenching effect of the phosphor. The present study clarified the effects of temperature on the lifetime of phosphorescence of Porphyrins, Ru(bpy)3^2+ and the europium complex. The phosphorescence lifetime of oil solution / water solution / painted wall were measured with changing temperature and oxygen concentration. In addition, the optical property of the small particles incorporated with the europium complex was investigated in the oil/water. The lifetime was strongly affected by temperature. Then, the temperature sensitive particle (TSParticle) with metal complex was applied to measure temperature in Silicone oil (10cSt) two-dimensionally. Present study is the result of ?High speed three-dimensional direct measurement technology development for the evaluation of heat flux and flow of liquid metal? entrusted to the University of Tokyo by the Ministry of Education, Culture, Sports, Science and Technology of Japan(MEXT).

  3. Velocity and drop size measurements in a swirl-stabilized, combusting spray

    NASA Technical Reports Server (NTRS)

    Bulzan, Daniel L.

    1993-01-01

    Velocity and drop size measurements are reported for a swirl-stabilized, combusting spray. For the gas phase, three components of mean and fluctuating velocity are reported. For the droplets, three components of mean and fluctuating velocity, diameter, and number flux are reported. The liquid fuel utilized for all the tests was heptane. The fuel was injected using an air-assist atomizer. The combustor configuration consisted of a center-mounted, air-assist atomizer surrounded by a coflowing air stream. Both the coflow and the atomizing air streams were passed through 45 degree swirlers. The swirl was imparted to both streams in the same direction. The combustion occurred unconfined in stagnant surroundings. The nonintrusive measurements were obtained using a two-component phase/Doppler particle analyzer. The laser-based instrument measured two components of velocity as well as droplet size at a particular point. Gas phase measurements were obtained by seeding the air streams with nominal 1 micron size aluminum-oxide particles and using the measured velocity from that size to represent the gas phase velocity. The atomizing air, coflow air, and ambient surroundings were all seeded with the aluminum-oxide particles to prevent biasing. Measurements are reported at an axial distance of 5 mm from the nozzle. Isothermal single-phase gas velocities are also reported for comparison with the combusting case.

  4. Techniques for measurement of velocity in liquid-metal MHD flows

    SciTech Connect

    Reed, C.B.; Picologlou, B.F.; Dauzvardis, P.V.; Bailey, J.L.

    1986-01-01

    Three instruments for measuring local velocities in liquid-metal MHD experiments for fusion blanket applications are being evaluated. The devices are used in room-temperature NaK experiments to measure three-dimensional flow field patterns anticipated in complex blanket geometries. Hot film anemometry, a standard technique in ordinary fluids, is being used, as well as two developmental devices. One is called the Liquid Metal Electromagnetic Velocity Instrument (LEVI), and performs essentially as a local dc electromagnetic flow meter. The third device, a Thermal Transient Anemometer (TTA) is a rugged, yet relatively simple device, which measures local velocity through the mechanism of convective heat transfer, in some ways similar to hot-film anemometry. Results are presented showing the kinds of data collected this far with each instrument. Measurements include both local velocity measurements and some preliminary frequency analyses of the fluctuating signals from both a hot-film sensor and the LEVI device.

  5. Techniques for measurement of velocity in liquid-metal MHD flows

    SciTech Connect

    Reed, C.B.; Picologlou, B.F.; Dauzvardis, P.V.; Bailey, J.L.

    1986-11-01

    Three instruments for measuring local velocities in liquid-metal MHD experiments for fusion blanket applications are being evaluated. The devices are used in room-temperature NaK experiments to measure three-dimensional flow field patterns anticipated in complex blanket geometries. Hot film anemometry, a standard technique in ordinary fluids, is being used, as well as two developmental devices. One is called the Liquid Metal Electromagnetic Velocity Instrument (LEVI), and performs essentially as a local DC electromagnetic flow meter. The third device, a Thermal Transient Anemometer (TTA) is a rugged, yet relatively simple device, which measures local velocity through the mechanism of convective heat transfer, in some ways similar to hot-film anemometry. Results are presented showing the kinds of data collected thus far with each instrument. Measurements include both local velocity measurements and some preliminary frequency analyses of the fluctuating signals from both a hot-film sensor and the LEVI device.

  6. Angular velocity estimation from measurement vectors of star tracker.

    PubMed

    Liu, Hai-bo; Yang, Jun-cai; Yi, Wen-jun; Wang, Jiong-qi; Yang, Jian-kun; Li, Xiu-jian; Tan, Ji-chun

    2012-06-01

    In most spacecraft, there is a need to know the craft's angular rate. Approaches with least squares and an adaptive Kalman filter are proposed for estimating the angular rate directly from the star tracker measurements. In these approaches, only knowledge of the vector measurements and sampling interval is required. The designed adaptive Kalman filter can filter out noise without information of the dynamic model and inertia dyadic. To verify the proposed estimation approaches, simulations based on the orbit data of the challenging minisatellite payload (CHAMP) satellite and experimental tests with night-sky observation are performed. Both the simulations and experimental testing results have demonstrated that the proposed approach performs well in terms of accuracy, robustness, and performance.

  7. Dynamic temperature and velocity measurements using neutron resonance spectroscopy

    SciTech Connect

    Yuan, V.W.; Asay, B.W.; Boat, R.

    1997-08-01

    The use of Doppler broadening in neutron resonances as a quantitative way to measure temperatures has been proposed and investigated for cases of static or quasi-static temperature measurements. Neutrons are temperature probes that can penetrate a sample to view its interior. At the same time products that may shield a sample optically are not opaque to neutrons so that temperature measurements can be made in their presence. When neutrons are attenuated by a sample material, the time-of-flight (TOF) spectrum of the transmitted neutrons exhibits a series of characteristic dips or resonances. These resonances appear when neutrons are captured from the beam in the formation of excited states in the A + 1 nucleus (n + A {ge} (A + 1){sup *}). Subsequent de-excitation of these states, by gamma emission or particle emission into 4{pi} steradians, effectively eliminates the captured neutrons from the transmitted beam. The resonance locations and lineshapes which appear in the TOF spectrum are unique to each isotopic element, and temperature determinations can be localized through the positioning of resonant tags.

  8. Fast measurements of average flow velocity by Low-Field ¹H NMR.

    PubMed

    Osán, T M; Ollé, J M; Carpinella, M; Cerioni, L M C; Pusiol, D J; Appel, M; Freeman, J; Espejo, I

    2011-04-01

    In this paper, we describe a method for measuring the average flow velocity of a sample by means of Nuclear Magnetic Resonance. This method is based on the Carr-Purcell-Meiboom-Gill (CPMG) sequence and does not require the application of any additional static or pulsed magnetic field gradients to the background magnetic field. The technique is based on analyzing the early-time behavior of the echo amplitudes of the CPMG sequence. Measurements of average flow velocity of water are presented. The experimental results show a linear relationship between the slope/y-intercept ratio of a linear fit of the first echoes in the CPMG sequence, and the average flow velocity of the flowing fluid. The proposed method can be implemented in low-cost Low-Field NMR spectrometers allowing a continuous monitoring of the average velocity of a fluid in almost real-time, even if the flow velocity changes rapidly.

  9. Laser induced fluorescence measurements of axial velocity, velocity shear, and parallel ion temperature profiles during the route to plasma turbulence in a linear magnetized plasma device

    NASA Astrophysics Data System (ADS)

    Chakraborty Thakur, S.; Adriany, K.; Gosselin, J. J.; McKee, J.; Scime, E. E.; Sears, S. H.; Tynan, G. R.

    2016-11-01

    We report experimental measurements of the axial plasma flow and the parallel ion temperature in a magnetized linear plasma device. We used laser induced fluorescence to measure Doppler resolved ion velocity distribution functions in argon plasma to obtain spatially resolved axial velocities and parallel ion temperatures. We also show changes in the parallel velocity profiles during the transition from resistive drift wave dominated plasma to a state of weak turbulence driven by multiple plasma instabilities.

  10. Temperature and stress dependence of ultrasonic velocity: Further measurements

    NASA Astrophysics Data System (ADS)

    Weaver, Richard; Lobkis, Oleg

    2002-05-01

    Large and erratic values for the material parameter d ln[dV/dT]/dσ have been reported in the past, including (our own) values indistinguishable from zero. Naive theoretical estimates for the parameter suggest that it should be of the order of an inverse Young's modulus, but some groups have reported values as much as 100 times greater, as high as an inverse Yield modulus. This suggests that an explanation for the anomalously high and variable coefficient is that it depends on plastic history. In an effort to resolve the discrepancies we revisit the measurements, but now on specimens with different plastic histories. The times-of-flight of multiply reflected 10 MHz ultrasound pulses in aluminum bars were resolved to within 1 nanosecond. Variations in natural wavespeeds were measured to within by cross-correlating late echoes received at different temperatures and stresses. Compressive elastic loads were applied on an axis perpendicular to the direction of the longitudinal acoustic wave, as the specimens cooled from 50 degrees C to 20. The specimen with large (10%) plastic pre-strain was found to show a 4% change in d ln V/dT when applied elastic strain was 0.1%, but the effect was not linear in stress. Consistent with our previous reports, specimens with no significant plastic history showed no discernable coefficient.

  11. Simultaneous Measurement of Air Temperature and Humidity Based on Sound Velocity and Attenuation Using Ultrasonic Probe

    NASA Astrophysics Data System (ADS)

    Motegi, Takahiro; Mizutani, Koichi; Wakatsuki, Naoto

    2013-07-01

    In this paper, an acoustic technique for air temperature and humidity measurement in moist air is described. The previous ultrasonic probe can enable the estimation of temperature from sound velocity in dry air by making use of the relationship between sound velocity and temperature. However, temperature measurement using the previous ultrasonic probe is not suitable in moist air because sound velocity also depends on humidity, and the temperature estimated from the sound velocity measured in moist air must be adjusted. Moreover, a method of humidity measurement by using only an ultrasonic probe has not been established. Thus, we focus on sound attenuation, which depends on temperature and humidity. Our proposed technique utilizes two parameters, sound velocity and attenuation, and can measure both temperature and humidity simultaneously. The acoustic technique for temperature and humidity measurement has the advantages that instantaneous temperature and humidity can be measured, and the measurement is not affected by thermal radiation because air itself is used as a sensing element. As an experiment, temperature and humidity are measured in a chamber, and compared with the reference values. The experimental results indicate the achievement of a practical temperature measurement accuracy of within +/-0.5 K in moist air, of which the temperature is 293-308 K and relative humidity (RH) is 50-90% RH, and the simultaneous measurement of temperature and humidity.

  12. Measurement of temperature and velocity fields in a convective fluid flow in air using schlieren images.

    PubMed

    Martínez-González, A; Moreno-Hernández, D; Guerrero-Viramontes, J A

    2013-08-01

    A convective fluid flow in air could be regulated if the physical process were better understood. Temperature and velocity measurements are required in order to obtain a proper characterization of a convective fluid flow. In this study, we show that a classical schlieren system can be used for simultaneous measurements of temperature and velocity in a convective fluid flow in air. The schlieren technique allows measurement of the average fluid temperature and velocity integrated in the direction of the test beam. Therefore, in our experiments we considered surfaces with isothermal conditions. Temperature measurements are made by relating the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the schlieren system. The same schlieren images were also used to measure the velocity of the fluid flow by using optical flow techniques. The algorithm implemented analyzes motion between consecutive schlieren frames to obtain a tracked sequence and finally velocity fields. The proposed technique was applied to measure the temperature and velocity fields in natural convection of air due to unconfined and confined heated rectangular plates.

  13. Velocity and drop size measurements in a confined, swirl-stabilized, combusting spray

    NASA Technical Reports Server (NTRS)

    Bulzan, Daniel L.

    1996-01-01

    Drop size and velocity measurements in a confined, swirl-stabilized, reacting spray are presented. The configuration consisted of a center-mounted research air-assist atomizer surrounded by a coflowing air stream. A quartz tube surrounded the burner and provided the confinement. Both the air-assist and coflow streams had swirl imparted to them in the same direction with 45-degree-angle swirlers. The fuel and air entered the combustor at ambient temperature. The gas-phase measurements reported were obtained from the velocity drops with a mean diameter of four microns. Heptane fuel was used for all the experiments. Measurements of drop size and velocity, gas-phase velocity and drop number flux are reported for axial distances of 23, 5, 10, 15, 25, and 50 mm downstream of the nozzle. The measurements were performed using a two-component phase/Doppler particle analyzer. Profiles across the entire flowfield are presented.

  14. A pulsed wire probe for the measurement of velocity and flow direction in slowly moving air.

    PubMed

    Olson, D E; Parker, K H; Snyder, B

    1984-02-01

    This report describes the theory and operation of a pulsed-probe anemometer designed to measure steady three-dimensional velocity fields typical of pulmonary tracheo-bronchial airflows. Local velocities are determined by measuring the transport time and orientation of a thermal pulse initiated at an upstream wire and sensed at a downstream wire. The transport time is a reproducible function of velocity and the probe wire spacing, as verified by a theoretical model of convective heat transfer. When calibrated the anemometer yields measurements of velocity accurate to +/- 5 percent and resolves flow direction to within 1 deg at airspeeds greater than or equal to 10 cm/s. Spatial resolution is +/- 0.5 mm. Measured flow patterns typical of curved circular pipes are included as examples of its application.

  15. Use of hot wire anemometry to measure velocity of the limb during human movement.

    PubMed

    Sun, S C; Mote, C D; Skinner, H B

    1992-09-01

    Hot film anemometry, x-configuration probes were used in two experiments to evaluate their effectiveness at measurement of limb velocity. Data from tests with a probe attached to the end of a pendulum establish that the hot films measure velocity in the swing phase within 0.098 ms-1. The kinetic energy per unit mass of the pendulum was predicted within +/- 0.005 m2 s-2, from the measured velocity. In gait experiments with one human subject at speeds greater than 0.25 ms-1, the hot film anemometer and a video system predicted speeds within 0.083 ms-1. The hot film data are electronic signals that are easily stored and processed. The results from these experiments demonstrate that hot film anemometry is an effective and efficient method for direct measurement and analysis of the limb velocity.

  16. Workshop on Particle Capture, Recovery and Velocity/Trajectory Measurement Technologies

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E. (Editor)

    1994-01-01

    A workshop on particle capture, recovery, and velocity/trajectory measurement technologies was held. The primary areas covered were: (1) parent-daughter orbit divergence; (2) trajectory sensing; (3) capture medium development: laboratory experiments, and (4) future flight opportunities.

  17. Complementarity of weak lensing and peculiar velocity measurements in testing general relativity

    SciTech Connect

    Song, Yong-Seon; Zhao Gongbo; Bacon, David; Koyama, Kazuya; Nichol, Robert C.; Pogosian, Levon

    2011-10-15

    We explore the complementarity of weak lensing and galaxy peculiar velocity measurements to better constrain modifications to General Relativity. We find no evidence for deviations from General Relativity on cosmological scales from a combination of peculiar velocity measurements (for Luminous Red Galaxies in the Sloan Digital Sky Survey) with weak lensing measurements (from the Canadian France Hawaii Telescope Legacy Survey). We provide a Fisher error forecast for a Euclid-like space-based survey including both lensing and peculiar velocity measurements and show that the expected constraints on modified gravity will be at least an order of magnitude better than with present data, i.e. we will obtain {approx_equal}5% errors on the modified gravity parametrization described here. We also present a model-independent method for constraining modified gravity parameters using tomographic peculiar velocity information, and apply this methodology to the present data set.

  18. The influence of the arrangements of multi-sensor probe arrays on the accuracy of simultaneously measured velocity and velocity gradient-based statistics in turbulent shear flows

    NASA Astrophysics Data System (ADS)

    Vukoslavčević, P. V.; Wallace, J. M.

    2013-06-01

    A highly resolved turbulent channel flow direct numerical simulation (DNS) with Re τ = 200 has been used to investigate the influence of the arrangements of the arrays (array configurations), within the sensing area of a multi-array hot-wire probe on the measurement accuracy of velocity and velocity gradient-based statistics. To eliminate all effects related to the sensor response and array characteristics (such as sensor dimensions, overheat ratio, thermal cross talk, number and orientations of the sensors and uniqueness range) so that this study could be focused solely on the effects of the array configurations (positions and separations), a concept of a perfect array was introduced, that is, one that can exactly and simultaneously measure all three velocity components at its center. The velocity component values, measured by these perfect arrays, are simply the DNS values computed at these points. Using these velocity components, the velocity and velocity gradient-based statistics were calculated assuming a linear velocity variation over the probes' sensing areas. The calculated values are compared to the DNS values for various array arrangements to study the influence of these arrangements on the measurement accuracy. Typical array configurations that previously have been used for physical probes were tested. It is demonstrated that the array arrangements strongly influence the accuracy of some of the velocity and velocity gradient-based statistics and that no single configuration exists, for a given spatial resolution, which gives the best accuracy for all of the statistics characterizing a turbulent shear flow.

  19. Water Velocity Measurements on a Vertical Barrier Screen at the Bonneville Dam Second Powerhouse

    SciTech Connect

    Hughes, James S.; Deng, Zhiqun; Weiland, Mark A.; Martinez, Jayson J.; Yuan, Yong

    2011-11-22

    Fish screens at hydroelectric dams help to protect rearing and migrating fish by preventing them from passing through the turbines and directing them towards the bypass channels by providing a sweeping flow parallel to the screen. However, fish screens may actually be harmful to fish if they become impinged on the surface of the screen or become disoriented due to poor flow conditions near the screen. Recent modifications to the vertical barrier screens (VBS) at the Bonneville Dam second powerhouse (B2) intended to increase the guidance of juvenile salmonids into the juvenile bypass system (JBS) have resulted in high mortality and descaling rates of hatchery subyearling Chinook salmon during the 2008 juvenile salmonid passage season. To investigate the potential cause of the high mortality and descaling rates, an in situ water velocity measurement study was conducted using acoustic Doppler velocimeters (ADV) in the gatewell slot at Units 12A and 14A of B2. From the measurements collected the average approach velocity, sweep velocity, and the root mean square (RMS) value of the velocity fluctuations were calculated. The approach velocities measured across the face of the VBS varied but were mostly less than 0.3 m/s. The sweep velocities also showed large variances across the face of the VBS with most measurements being less than 1.5 m/s. This study revealed that the approach velocities exceeded criteria recommended by NOAA Fisheries and Washington State Department of Fish and Wildlife intended to improve fish passage conditions.

  20. 3D velocity measurement by a single camera using Doppler phase-shifting holography

    NASA Astrophysics Data System (ADS)

    Ninomiya, Nao; Kubo, Yamato; Barada, Daisuke; Kiire, Tomohiro

    2016-10-01

    In order to understand the details of the flow field in micro- and nano-fluidic devices, it is necessary to measure the 3D velocities under a microscopy. Thus, there is a strong need for the development of a new measuring technique for 3D velocity by a single camera. One solution is the use of holography, but it is well known that the accuracy in the depth direction is very poor for the commonly used in-line holography. At present, the Doppler phase-shifting holography is used for the 3D measurement of an object. This method extracts the signal of a fixed frequency caused by the Doppler beat between the object light and the reference light. It can measure the 3D shape precisely. Here, the frequency of the Doppler beat is determined by the velocity difference between the object light and the reference light. This implies that the velocity of an object can be calculated by the Doppler frequency. In this study, a Japanese 5 yen coin was traversed at a constant speed and its holography has been observed by a high-speed camera. By extracting only the first order diffraction signal at the Doppler frequency, a precise measurement of the shape and the position of a 5 yen coin has been achieved. At the same time, the longitudinal velocity of a 5 yen coin can be measured by the Doppler frequency. Furthermore, the lateral velocities are obtained by particle image velocimetry (PIV) method. A 5 yen coin has been traversed at different angles and its shapes and the 3D velocities have been measured accurately. This method can be applied to the particle flows in the micro- or nano-devices, and the 3D velocities will be measured under microscopes.

  1. Measuring two-dimensional components of a flow velocity vector using a hot-wire probe.

    PubMed

    Kiełbasa, Jan

    2007-08-01

    The article presents a single-hot-wire probe adapted to detect the direction of flow velocity. The modification consists of the introduction of a third support which allows to measure voltage at the central point of the wire. The sign of voltage difference DeltaU between both parts of the wire is the measure of the direction of flow velocity in a system of coordinates associated with the probe.

  2. Laser and acoustic Doppler techniques for the measurement of fluid velocities

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.

    1975-01-01

    An overview of current laser and acoustic Doppler techniques is presented. Results obtained by Doppler anemometry and conventional sensors are compared. Comparisons include simultaneous velocity measurements by hot wire and a three-dimensional laser anemometer made in a gaseous pipe flow as well as direct comparisons of atmospheric velocities measured with propeller and cup anemometry. Scanning techniques are also discussed. Conclusions and recommendations for future work are presented.

  3. Computer signal processing for ultrasonic attenuation and velocity measurements for material property characterizations

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1979-01-01

    Instrumentation and computer programming concepts that were developed for ultrasonic materials characterization are described. Methods that facilitate velocity and attenuation measurements are outlined. The apparatus described is based on a broadband, buffered contact probe using a pulse-echo approach for simultaneously measuring velocity and attenuation. Instrumentation, specimen condition, and signal acquisition and acceptance criteria are discussed. Typical results with some representative materials are presented.

  4. Computer signal processing for ultrasonic attenuation and velocity measurements for material property characterizations

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1979-01-01

    This report deals with instrumentation and computer programming concepts that have been developed for ultrasonic materials characterization. Methods that facilitate velocity and attenuation measurements are described. The apparatus described is based on a broadband, buffered contact probe using a pulse-echo approach for simultaneously measuring velocity and attenuation. Instrumentation, specimen condition, and signal acquisition and acceptance criteria are discussed. Typical results with some representative materials are presented.

  5. Concentration and velocity measurements in the flow of droplet suspensions through a tube

    NASA Astrophysics Data System (ADS)

    Kowalewski, T. A.

    1984-12-01

    Two optical methods, light absorption and LDA, are applied to measure the concentration and velocity profiles of droplet suspensions flowing through a tube. The droplet concentration is non-uniform and has two maxima, one near the tube wall and one on the tube axis. The measured velocity profiles are blunted, but a central plug-flow region is not observed. The concentration of droplets on the tube axis and the degree of velocity profile blunting depend on relative viscosity. These results can be qualitatively compared with the theory of Chan and Leal.

  6. Convective cloud top vertical velocity estimated from geostationary satellite rapid-scan measurements

    NASA Astrophysics Data System (ADS)

    Hamada, Atsushi; Takayabu, Yukari N.

    2016-05-01

    We demonstrate that the rate of development of cumulus clouds, as inferred from the so-called geostationary satellite "rapid-scan" measurements, is a good proxy for convective cloud top vertical velocity related to deep convective clouds. Convective cloud top vertical velocity is estimated from the decreasing rate of infrared brightness temperature observed by the Multi-functional Transport SATellite-1R (MTSAT-1R) over the ocean south of Japan during boreal summer. The frequency distribution of the estimated convective cloud top vertical velocity at each height is shown to distribute lognormally, and it is consistent with the statistical characteristics of direct measurements acquired in previous studies.

  7. Measuring Ultrasonic Acoustic Velocity in a Thin Sheet of Graphite Epoxy Composite

    NASA Technical Reports Server (NTRS)

    2008-01-01

    A method for measuring the acoustic velocity in a thin sheet of a graphite epoxy composite (GEC) material was investigated. This method uses two identical acoustic-emission (AE) sensors, one to transmit and one to receive. The delay time as a function of distance between sensors determines a bulk velocity. A lightweight fixture (balsa wood in the current implementation) provides a consistent method of positioning the sensors, thus providing multiple measurements of the time delay between sensors at different known distances. A linear fit to separation, x, versus delay time, t, will yield an estimate of the velocity from the slope of the line.

  8. Coherent Doppler Lidar for Measuring Velocity and Altitude of Space and Arial Vehicles

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Hines, Glenn D.; Petway, Larry; Barnes, Bruce W.

    2016-01-01

    A coherent Doppler lidar has been developed to support future NASA missions to planetary bodies. The lidar transmits three laser beams and measures line-of-sight range and velocity along each beam using a frequency modulated continuous wave (FMCW) technique. Accurate altitude and velocity vector data, derived from the line-of-sight measurements, enables the landing vehicle to precisely navigate from several kilometers above the ground to the designated location and execute a gentle touchdown. The same lidar sensor can also benefit terrestrial applications that cannot rely on GPS or require surface-relative altitude and velocity data.

  9. A nano cold-wire for velocity measurements

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Chun; Fu, Matthew; Fan, Yuyang; Byers, Clayton; Hultmark, Marcus

    2016-11-01

    We introduce a novel, strain-based sensor for both gaseous and liquid flows. The sensor consists of a free-standing, electrically conductive, nanoscale ribbon suspended between silicon supports. Due to its size, the nanoribbon deflects in flow under viscously dominated fluid forcing, which induces axial strain and a resistance change in the sensing element. The change in resistance can then be measured by a Wheatstone bridge, resulting in straightforward design and operation of the sensor. Since its operating principle is based on viscous fluid forcing, the sensor has high sensitivity especially in liquid or other highly viscous flows. A simple analytical model to understand the relation between forcing and strain is derived from the geometric and material constraints, and preliminary analysis using a low order model of the dynamic systems suggests that the sensor has a high frequency response. Lastly, a cylindrical structure to house the sensor with an axial and ventral channel to generate a pressure differential is being considered for typical velocimetry applications.

  10. Detection and analysis of multi-dimensional pulse wave based on optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Shen, Yihui; Li, Zhifang; Li, Hui; Chen, Haiyu

    2014-11-01

    Pulse diagnosis is an important method of traditional Chinese medicine (TCM). Doctors diagnose the patients' physiological and pathological statuses through the palpation of radial artery for radial artery pulse information. Optical coherence tomography (OCT) is an useful tool for medical optical research. Current conventional diagnostic devices only function as a pressure sensor to detect the pulse wave - which can just partially reflect the doctors feelings and lost large amounts of useful information. In this paper, the microscopic changes of the surface skin above radial artery had been studied in the form of images based on OCT. The deformation of surface skin in a cardiac cycle which is caused by arterial pulse is detected by OCT. The patient's pulse wave is calculated through image processing. It is found that it is good consistent with the result conducted by pulse analyzer. The real-time patient's physiological and pathological statuses can be monitored. This research provides a kind of new method for pulse diagnosis of traditional Chinese medicine.

  11. Comparison of atenolol versus bisoprolol with noninvasive hemodynamic and pulse wave assessment.

    PubMed

    Aparicio, Lucas S; Alfie, José; Barochiner, Jessica; Cuffaro, Paula E; Giunta, Diego H; Elizondo, Cristina M; Tortella, Juan J; Morales, Margarita S; Rada, Marcelo A; Waisman, Gabriel D

    2015-05-01

    We aimed to compare atenolol versus bisoprolol regarding general hemodynamics, central-peripheral blood pressure (BP), pulse wave parameters, and arterial stiffness. In this open-label, crossover study, we recruited 19 hypertensives, untreated or with stable monotherapy. Patients were randomized to receive atenolol (25-50 mg) or bisoprolol (2.5-5 mg), and then switched medications after 4 weeks. Studies were performed at baseline and after each drug period. In pulse wave analyses, both drugs significantly increased augmentation index (P < .01) and ejection duration (P < .02), and reduced heart rate (P < .001), brachial systolic BP (P ≤ .01), brachial diastolic BP (P ≤ .001), and central diastolic BP (P ≤ .001), but not central systolic BP (P ≥ .06). Impedance cardiographic assessment showed a significantly increased stroke volume (P ≤ .02). There were no significant differences in the effects between drugs. In conclusion, atenolol and bisoprolol show similar hemodynamic characteristics. Failure to decrease central systolic BP results from bradycardia with increased stroke volume and an earlier reflected aortic wave.

  12. Doubly-excited pulse-waves on flowing liquid films: experiments and numerical simulations

    NASA Astrophysics Data System (ADS)

    Adebayo, Idris; Xie, Zhihua; Che, Zhizhao; Wray, Alex; Matar, Omar

    2016-11-01

    The interaction patterns between doubly-excited pulse waves on a flowing liquid film are studied both experimentally and numerically. The flowing film is constituted on an inclined glass substrate while pulse-waves are excited on the film surface by means of a solenoid valve connected to a relay which receives signals from customised Matlab routines. The effect of varying the system parameters i.e. film flow rate, inter-pulse interval and substrate inclination angle on the pulse interaction patterns are then studied. Results show that different interaction patterns exist for these binary pulses; which include a singular behaviour, complete merger, partial merger and total non-coalescence. A regime map of these patterns is then plotted for each inclination angles examined, based on the film Re and the inter-pulse interval. Finally, the individual effect of the system parameters on the merging distance of these binary pulses in the merger mode is then studied and the results validated using both numerical simulations and mathematical modelling. Funding from the Nigerian Government (for Idris Adebayo), and the EPSRC through a programme Grant MEMPHIS (EP/K003976/1) gratefully acknowledged.

  13. Measurement of fast-changing low velocities by photonic Doppler velocimetry

    SciTech Connect

    Song Hongwei; Wu Xianqian; Huang Chenguang; Wei Yangpeng; Wang Xi

    2012-07-15

    Despite the increasing popularity of photonic Doppler velocimetry (PDV) in shock wave experiments, its capability of capturing low particle velocities while changing rapidly is still questionable. The paper discusses the performance of short time Fourier transform (STFT) and continuous wavelet transform (CWT) in processing fringe signals of fast-changing low velocities measured by PDV. Two typical experiments are carried out to evaluate the performance. In the laser shock peening test, the CWT gives a better interpretation to the free surface velocity history, where the elastic precursor, main plastic wave, and elastic release wave can be clearly identified. The velocities of stress waves, Hugoniot elastic limit, and the amplitude of shock pressure induced by laser can be obtained from the measurement. In the Kolsky-bar based tests, both methods show validity of processing the longitudinal velocity signal of incident bar, whereas CWT improperly interprets the radial velocity of the shocked sample at the beginning period, indicating the sensitiveness of the CWT to the background noise. STFT is relatively robust in extracting waveforms of low signal-to-noise ratio. Data processing method greatly affects the temporal resolution and velocity resolution of a given fringe signal, usually CWT demonstrates a better local temporal resolution and velocity resolution, due to its adaptability to the local frequency, also due to the finer time-frequency product according to the uncertainty principle.

  14. Diode Laser Velocity Measurements by Modulated Filtered Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Mach, J. J.; Varghese, P. L.; Jagodzinski, J. J.

    1999-01-01

    The ability of solid-state lasers to be tuned in operating frequency at MHz rates by input current modulation, while maintaining a relatively narrow line-width, has made them useful for spectroscopic measurements. Their other advantages include low cost, reliability, durability, compact size, and modest power requirements, making them a good choice for a laser source in micro-gravity experiments in drop-towers and in flight. For their size, they are also very bright. In a filtered Rayleigh scattering (FRS) experiment, a diode laser can be used to scan across an atomic or molecular absorption line, generating large changes in transmission at the resonances for very small changes in frequency. The hyperfine structure components of atomic lines of alkali metal vapors are closely spaced and very strong, which makes such atomic filters excellent candidates for sensitive Doppler shift detection and therefore for high-resolution velocimetry. In the work we describe here we use a Rubidium vapor filter, and work with the strong D(sub 2) transitions at 780 nm that are conveniently accessed by near infrared diode lasers. The low power output of infrared laser diodes is their primary drawback relative to other laser systems commonly used for velocimetry. However, the capability to modulate the laser frequency rapidly and continuously helps mitigate this. Using modulation spectroscopy and a heterodyne detection scheme with a lock-in amplifier, one can extract sub-microvolt signals occurring at a specific frequency from a background that is orders of magnitude stronger. The diode laser modulation is simply achieved by adding a small current modulation to the laser bias current. It may also be swept repetitively in wavelength using an additional lower frequency current ramp.

  15. A Vector Measurement-based Angular Velocity Estimation Scheme for Maneuvering Spacecraft

    NASA Astrophysics Data System (ADS)

    Jo, Sujang; Bang, Hyochoong; Leeghim, Henzeh

    2017-01-01

    A new practical approach to estimate the body angular velocity of maneuvering spacecraft using only vector measurements is presented. Several algorithms have been introduced in previous studies to estimate the angular velocity directly from vector measurements at two time instants. However, these direct methods are based on the constant angular velocity assumption, and estimation results may be invalid for attitude maneuvers. In this paper, an estimation scheme to consider attitude disturbances and control torques is proposed. The effects of angular velocity variation on estimation results are quantitatively evaluated, and an algorithm to minimize estimation errors is designed by selecting the optimal time interval between vector measurements. Without losing the simplicity of direct methods, the design parameters of the algorithm are restricted to the expected covariance of disturbances and the maximum angular acceleration. By applying the proposed estimation scheme, gyroscopes can be directly replaced by attitude sensors such as star trackers.

  16. Flow measurements in sewers based on image analysis: automatic flow velocity algorithm.

    PubMed

    Jeanbourquin, D; Sage, D; Nguyen, L; Schaeli, B; Kayal, S; Barry, D A; Rossi, L

    2011-01-01

    Discharges of combined sewer overflows (CSOs) and stormwater are recognized as an important source of environmental contamination. However, the harsh sewer environment and particular hydraulic conditions during rain events reduce the reliability of traditional flow measurement probes. An in situ system for sewer water flow monitoring based on video images was evaluated. Algorithms to determine water velocities were developed based on image-processing techniques. The image-based water velocity algorithm identifies surface features and measures their positions with respect to real world coordinates. A web-based user interface and a three-tier system architecture enable remote configuration of the cameras and the image-processing algorithms in order to calculate automatically flow velocity on-line. Results of investigations conducted in a CSO are presented. The system was found to measure reliably water velocities, thereby providing the means to understand particular hydraulic behaviors.

  17. Characterization of intermetallic precipitates in a Nimonic alloy by ultrasonic velocity measurements

    SciTech Connect

    Murthy, G.V.S. Sridhar, G.; Kumar, Anish; Jayakumar, T.

    2009-03-15

    Ultrasonic velocity measurements have been carried out in Nimonic 263 specimens thermally aged at 923 and 1073 K for durations up to 75 h and correlated with the results of hardness measurements and electron microscopy studies. The ultrasonic velocities and hardness results obtained in the specimens thermally aged at both temperatures clearly indicated that ultrasonic velocity is more sensitive to the initiation of the precipitation, whereas the influence of precipitation on hardness can be observed only after the precipitates attain a minimum size to influence the movement of dislocations. Further, ultrasonic velocity measurements also revealed faster kinetics and a lesser amount of precipitation at 1073 K compared to 923 K due to higher solubility of precipitate-forming elements.

  18. Fabry-Perot interferometer measurement of static temperature and velocity for ASTOVL model tests

    NASA Technical Reports Server (NTRS)

    Kourous, Helen E.; Seacholtz, Richard G.

    1995-01-01

    A spectrally resolved Rayleigh/Mie scattering diagnostic was developed to measure temperature and wing-spanwise velocity in the vicinity of an ASTOVL aircraft model in the Lewis 9 x 15 Low Speed Wind Tunnel. The spectrum of argon-ion laser light scattered by the air molecules and particles in the flow was resolved with a Fabry-Perot interferometer. Temperature was extracted from the spectral width of the Rayleigh scattering component, and spanwise gas velocity from the gross spectral shift. Nozzle temperature approached 800 K, and the velocity component approached 30 m/s. The measurement uncertainty was about 5 percent for the gas temperature, and about 10 m/s for the velocity. The large difference in the spectral width of the Mie scattering from particles and the Rayleigh scattering from gas molecules allowed the gas temperature to be measured in flow containing both naturally occurring dust and LDV seed (both were present).

  19. Front-crawl instantaneous velocity estimation using a wearable inertial measurement unit.

    PubMed

    Dadashi, Farzin; Crettenand, Florent; Millet, Grégoire P; Aminian, Kamiar

    2012-09-25

    Monitoring the performance is a crucial task for elite sports during both training and competition. Velocity is the key parameter of performance in swimming, but swimming performance evaluation remains immature due to the complexities of measurements in water. The purpose of this study is to use a single inertial measurement unit (IMU) to estimate front crawl velocity. Thirty swimmers, equipped with an IMU on the sacrum, each performed four different velocity trials of 25 m in ascending order. A tethered speedometer was used as the velocity measurement reference. Deployment of biomechanical constraints of front crawl locomotion and change detection framework on acceleration signal paved the way for a drift-free integration of forward acceleration using IMU to estimate the swimmers velocity. A difference of 0.6 ± 5.4 cm · s(-1) on mean cycle velocity and an RMS difference of 11.3 cm · s(-1) in instantaneous velocity estimation were observed between IMU and the reference. The most important contribution of the study is a new practical tool for objective evaluation of swimming performance. A single body-worn IMU provides timely feedback for coaches and sport scientists without any complicated setup or restraining the swimmer's natural technique.

  20. Transient velocity measurement in dusty boundary layyr developed behind a shock wave

    NASA Astrophysics Data System (ADS)

    Modarress, D.

    The results of recent particle velocity measurements at the 4 x 4 inch shock tube at TRW are presented. The measurements were made in a dusty boundary layer induced by the passage of a normal shock wave over a dust bed. The dust particle velocity was measured using a single component laser velocimeter. The measurement of the transient flow was made with a fast digitizer, at a sample rate of 100 MHz. Processing of the signal was achieved through software. A number of routines for detection of acceptable signal and discrimination against background noise was developed and evaluated. The velocity time history of the dust particles behind the moving shock waves at a number of heights above the dust level were measured. Simultaneous measurement of the laser light beam extinction was used to evaluate the dust density profile behind the shock wave.

  1. In vivo lateral blood flow velocity measurement using speckle size estimation.

    PubMed

    Xu, Tiantian; Hozan, Mohsen; Bashford, Gregory R

    2014-05-01

    In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method

  2. Revisiting the Influence of Unidentified Binaries on Velocity Dispersion Measurements in Ultra-faint Stellar Systems

    NASA Astrophysics Data System (ADS)

    McConnachie, Alan W.; Côté, Patrick

    2010-10-01

    Velocity dispersion measurements of recently discovered Milky Way satellites with MV >~ -7 imply that they posses high mass-to-light ratios. The expected velocity dispersions due to their baryonic mass are ~0.2 km s-1, but values gsim3 km s-1 are measured. We perform Monte Carlo simulations of mock radial velocity measurements of these systems assuming that they have mass-to-light ratios similar to globular clusters and posses an unidentified binary star population, to determine if these stars could boost the velocity dispersion to the observed values. We find that this hypothesis is unlikely to produce dispersions much in excess of ~4.5 km s-1, in agreement with previous work. However, for the systems with the potentially smallest velocity dispersions, values consistent with observations are produced in 5%-40% of our simulations for binary fractions in excess of f bin(P <= 10 yr)~ 5%. This sample includes the dwarf galaxy candidates that lie closest to classical globular clusters in MV - rh space. Considered as a population, it is unlikely that all of these dwarf galaxy candidates have mass-to-light ratios typical of globular clusters, but boosting of the observed dispersion by binaries from near-zero values cannot be ruled out at high confidence for several individual dwarf galaxy candidates. Given the importance of obtaining accurate velocity dispersions and dynamical masses for the faintest satellites, it is clearly desirable to directly exclude the possible effect of binaries on these systems. This requires multi-epoch radial velocity measurements with individual uncertainties of lsim1 km s-1 to identify spectroscopic binaries with orbital velocities of the order of the observed velocity dispersion.

  3. Observations of Velocity Conditions near a Hydroelectric Turbine Draft Tube Exit using ADCP Measurements

    SciTech Connect

    Cook, Christopher B.; Richmond, Marshall C.; Serkowski, John A.

    2007-10-01

    Measurement of flow characteristics near hydraulic structures is an ongoing challenge because of the need to obtain rapid measurements of time-varying velocity over a relatively large spatial domain. This paper discusses use of an acoustic Doppler current profiler (ADCP) to measure the rapidly diverging flow exiting from an operating hydroelectric turbine draft tube exit. The resolved three-dimensional velocity vectors show a highly complex and helical flow pattern developed near to and downstream of the exit. Velocity vectors were integrated across the exit and we computed an uneven percentage of flow (67%/33%) passing through the two draft tube barrels at a mid-range turbine discharge, consistent with physical model results. In addition to the three-dimensional velocity vectors, the individual one-dimensional velocities measured by each of the four ADCP beams can be separately used as calibration and validation datasets for numerical and physical models. This technique is demonstrated by comparing along-beam ADCP velocity measurements to data collected in a scaled physical model.

  4. Laser-induced fluorescence diagnostic for temperature and velocity measurements in a hydrogen arcjet plume.

    PubMed

    Liebeskind, J G; Hanson, R K; Cappelli, M A

    1993-10-20

    A diagnostic has been developed to measure velocity and translational temperature in the plume of a 1-kW-class arcjet thruster operating on hydrogen. Laser-induced fluorescence with a narrow-band cw laser is used to probe the Balmer α transition of excited atomic hydrogen. The velocity is determined from the Doppler shift of the fluorescence excitation spectrum, whereas the temperature is inferred from the lineshape. Analysis shows that although Doppler broadening is the only significant broadening mechanism, the fine structure of the transition must be taken into account. Near the exit plane, axial velocities vary from 4 to 14 km/s, radial velocities vary from 0 to 4 km/s, and swirl velocities are shown to be relatively small. Temperatures from 1000 to 5000 K indicate high dissociation fractions.

  5. PMN-PT single crystal, high-frequency ultrasonic needle transducers for pulsed-wave Doppler application.

    PubMed

    Zhou, Qifa; Xu, Xiaochen; Gottlieb, Emanuel J; Sun, Lei; Cannata, Jonathan M; Ameri, Hossein; Humayun, Mark S; Han, Pengdi; Shung, K Kirk

    2007-03-01

    High-frequency needle ultrasound transducers with an aperture size of 0.4 mm were fabricated using lead magnesium niobate-lead titanate (PMN-33% PT) as the active piezoelectric material. The active element was bonded to a conductive silver particle matching layer and a conductive epoxy backing through direct contact curing. An outer matching layer of parylene was formed by vapor deposition. The active element was housed within a polyimide tube and a 20-gauge needle housing. The magnitude and phase of the electrical impedance of the transducer were 47 omega and -38 degrees, respectively. The measured center frequency and -6 dB fractional bandwidth of the PMN-PT needle transducer were 44 MHz and 45%, respectively. The two-way insertion loss was approximately 15 dB. In vivo high-frequency, pulsed-wave Doppler patterns of blood flow in the posterior portion and in vitro ultrasonic backscatter microscope (UBM) images of the rabbit eye were obtained with the 44-MHz needle transducer.

  6. Ice Velocity Measurements From The First Sentinel-1a Full Antarctic Ice Sheet Campaign

    NASA Astrophysics Data System (ADS)

    Hogg, A. E.; Shepherd, A.; Gourmelen, N.; Nagler, T.

    2015-12-01

    We present an overview of ice velocity measurements produced from data acquired during the first Sentinel-1 full Antarctic ice sheet campaign. Satellite observations acquired over the past 25 years have shown marked ice velocity speed up on individual Antarctic ice streams, with ice velocity increases of over 42% observed on Pine Island Glacier. In Antarctica, areas of ice velocity speed up are dynamically unstable and comprise the largest component of ice sheet sea level rise contribution. However, despite a clear long term trend for increasing ice velocity in many regions, speed up has not been constant through time and multiple years with no significant change have also been observed. It is necessary to make present day measurements of ice velocity to provide an independent means of measuring ice mass loss from the most rapidly changing ice sheet regions. However the spatiotemporal coverage of historical ice velocity measurements has been limited by a paucity of suitable data over the full Antarctic ice sheet and to date, parts of east Antarctica have been observed only a few times during the last 25 years. We present 12 months of ice velocity measurements on 10 key Antarctic ice streams, produced from the normalised cross-correlation of real-valued intensity features in Interferometric Wide Swath (IW) mode Sentinel-1a data. A time series of ice velocity measurements produced from short 12-day repeat Sentinel-1a data over Pine Island Glacier shows that in 2014 and 2015 the ice surface speed has remained constant at ~4 km/year. A Sentinel-1a ice velocity map of the Antarctic Peninsula demonstrates that good quality measurements can be obtained along the full length of the Peninsula using Sentinel-1a. TOPS mode SAR Interferometry (InSAR) results shows that interferometric coherence can be preserved over the 12-day repeat period on stable slower flowing ice covered terrain, however on fast flowing ice streams such as Totten Glacier in East Antarctica and Pine

  7. High-speed non-intrusive measurements of fuel velocity fields at high-pressure injectors

    NASA Astrophysics Data System (ADS)

    Gürtler, Johannes; Schlüßler, Raimund; Fischer, Andreas; Czarske, Jürgen

    2017-03-01

    Using a single high-speed camera and a frequency modulated laser, a novel approach is presented for fast velocity field measurements in unsteady spray flows. The velocity range is from zero up to several 100 m/s, which requires a high measurement rate and a large dynamic. Typically, flow measurements require to seed tracer particles to the fluid. A paradigm shift to seeding-free measurements is presented. The light scattered at the phase boundaries of the fluid droplets is evaluated. In order to validate the high-speed measurement system, a detailed uncertainty analysis is performed by means of measurements as well as simulations. Thereby, variations of the scattered light intensity, which are based on the high temporal velocity gradients, are found to be the main contribution to the uncertainty. The eventually measurement results, obtained at a measurement rate of 500 kHz, exhibit spray velocities ranging from 0 m/s up to 400 m/s in less than 1 ms, and the detection of unsteady and irregular flow phenomena with a characteristic time of several μs is achieved. This demonstrates the high measurement rate, the high temporal resolution and the large measurement range of the proposed high-speed measurement system.

  8. Molecular Rayleigh Scattering Diagnostic for Dynamic Temperature, Velocity, and Density Measurements

    NASA Technical Reports Server (NTRS)

    Mielke, Amy R.; Elam, Kristie A.; Sung, Chi-Jen

    2006-01-01

    A molecular Rayleigh scattering technique is developed to measure dynamic gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 16 kHz. A high power CW laser beam is focused at a point in an air jet plume and Rayleigh scattered light is collected and spectrally resolved. The spectrum of the light, which contains information about the temperature and velocity of the flow, is analyzed using a Fabry-Perot interferometer. The circular interference fringe pattern is divided into four concentric regions and sampled at 1 and 16 kHz using photon counting electronics. Monitoring the relative change in intensity within each region allows for measurement of gas temperature and velocity. Independently monitoring the total scattered light intensity provides a measure of gas density. A low speed heated jet is used to validate the measurement of temperature fluctuations and an acoustically excited nozzle flow is studied to validate velocity fluctuation measurements. Power spectral density calculations of the property fluctuations, as well as mean and fluctuating quantities are presented. Temperature fluctuation results are compared with constant current anemometry measurements and velocity fluctuation results are compared with constant temperature anemometry measurements at the same locations.

  9. Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Park, C.B.; Hunter, J.A.; Harris, J.B.; Ivanov, J.

    2002-01-01

    Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated Vs and borehole measured Vs in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived Vs values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis. ?? 2002 Elsevier Science Ltd. All rights reserved.

  10. Velocity Measurement in a Dual-Mode Supersonic Combustor using Particle Image Velocimetry

    NASA Technical Reports Server (NTRS)

    Goyne, C. P.; McDaniel, J. C.; Krauss, R. H.; Day, S. W.; Reubush, D. E. (Technical Monitor); McClinton, C. R. (Technical Monitor); Reubush, D. E.

    2001-01-01

    Temporally and spatially-resolved, two-component measurements of velocity in a supersonic hydrogen-air combustor are reported. The combustor had a single unswept ramp fuel injector and operated with an inlet Mach number of 2 and a flow total temperature approaching 1200 K. The experiment simulated the mixing and combustion processes of a dual-mode scramjet operating at a flight Mach number near 5. The velocity measurements were obtained by seeding the fuel with alumina particles and performing Particle Image Velocimetry on the mixing and combustion wake of the ramp injector. To assess the effects of combustion on the fuel air-mixing process, the distribution of time-averaged velocity and relative turbulence intensity was determined for the cases of fuel-air mixing and fuel-air reacting. Relative to the mixing case, the near field core velocity of the reacting fuel jet had a slower streamwise decay. In the far field, downstream of 4 to 6 ramp heights from the ramp base, the heat release of combustion resulted in decreased flow velocity and increased turbulence levels. The reacting measurements were also compared with a computational fluid dynamics solution of the flow field. Numerically predicted velocity magnitudes were higher than that measured and the jet penetration was lower.

  11. STARE velocities: 3. Double-pulse and multi-pulse measurements

    NASA Astrophysics Data System (ADS)

    Uspensky, M.; Koustov, A.; Sofieva, V.; Amm, O.; Kauristie, K.; Schmidt, W.; Nielsen, E.; Pulkkinen, T.; Pellinen, R.; Pirjola, R.

    The STARE coherent radars are a powerfull instrument for studying the auroral zone electrodynamics, first of all with respect to plasma convection. For decades, the radars have been using the double-pulse (DP) technique to measure the velocity. Recently, the multi-pulse (MP) scheme has been implemented. The detailed comparisons (Uspensky et al., 2003, 2004) between EISCAT and STARE MP measurements showed a good performance of the MP scheme for convection estimates, contrary to the known difficulties of the DP method. In the present study we consider differences in the velocity estimates by the MP and DP schemes in order to evaluate the uncertainties of the convection predictions by the DP scheme. We confirm previous warnings by Schlegel et al. (1986) and Schlegel and Thomas (1988) that the STARE DP scheme with fixed pulse separation can give a systematic error in the velocity estimate. We show that the DP velocities are typically smaller than the MP velocities, especially for large flow angle observations in the afternoon/evening sector. We also report occasional cases of small DP velocity overestimations. It is argued that the observed differences between DP and MP velocities originate from a minor, but not negligible, correlation between the signals coming from the main and aliasing volumes of the DP scheme particularly under the condition of broad backscatter spectra.

  12. Measurement of tendon velocities using vector tissue Doppler imaging: a feasibility study.

    PubMed

    Eranki, Avinash; Bellini, Lindsey; Prosser, Laura; Stanley, Christopher; Bland, Daniel; Alter, Katharine; Damiano, Diane; Sikdar, Siddhartha

    2010-01-01

    We have developed a vector Doppler ultrasound imaging method to directly quantify the magnitude and direction of muscle and tendon velocities during movement. The goal of this study was to evaluate the feasibility of using vector Tissue Doppler Imaging (vTDI) for estimating the tibialis anterior tendon velocities during dorsiflexion in children with cerebral palsy who have foot drop. Our preliminary results from this study show that tendon velocities estimated using vTDI have a strong linear correlation with the joint angular velocity estimated using a conventional 3D motion capture system. We observed a peak tendon velocity of 5.66±1.45 cm/s during dorsiflexion and a peak velocity of 8.83±2.13 cm/s during the passive relaxation phase of movement. We also obtained repeatable results from the same subject 3 weeks apart. Direct measurements of muscle and tendon velocities may be used as clinical outcome measures and for studying efficiency of movement control.

  13. A new test chamber to measure material emissions under controlled air velocity

    SciTech Connect

    Bortoli, M. de; Ghezzi, E.; Knoeppel, H.; Vissers, H.

    1999-05-15

    A new 20-L glass chamber for the determination of VOC emissions from construction materials and consumer products under controlled air velocity and turbulence is described. Profiles of air velocity and turbulence, obtained with precisely positioned hot wire anemometric probes, show that the velocity field is homogeneous and that air velocity is tightly controlled by the fan rotation speed; this overcomes the problem of selecting representative positions to measure air velocity above a test specimen. First tests on material emissions show that the influence of air velocity on the emission rate of VOCs is negligible for sources limited by internal diffusion and strong for sources limited by evaporation. In a velocity interval from 0.15 to 0.30 m s{sup {minus}1}, an emission rate increase of 50% has been observed for pure n-decane and 1,4-dichlorobenzene and of 30% for 1,2-propanediol from a water-based paint. In contrast, no measurable influence of turbulence could be observed during vaporization of 1,4-dichlorobenzene within a 3-fold turbulence interval. Investigations still underway show that the chamber has a high recovery for the heavier VOC (TXIB), even at low concentrations.

  14. Seismic velocities and attenuation from borehole measurements near the Parkfield prediction zone, Central California

    USGS Publications Warehouse

    Gibbs, James F.; Roth, Edward F.

    1989-01-01

    Shear (S)- and compressional (P)- wave velocities were measured to a depth of 195 m in a borehole near the San Andreas fault where a recurrence of a moderate Parkfield earthquake is predicted. S-wave velocities determined from orthogonal directions of the S-wave source show velocity differences of approximately 20 percent. An average shear-wave Q of 4 was determined in relatively unconsolidated sands and gravels of the Paso Robles Formation in the depth interval 57.5-102.5 m.

  15. Doppler measurement of implosion velocity in fast Z-pinch x-ray sources

    NASA Astrophysics Data System (ADS)

    Jones, B.; Jennings, C. A.; Bailey, J. E.; Rochau, G. A.; Maron, Y.; Coverdale, C. A.; Yu, E. P.; Hansen, S. B.; Ampleford, D. J.; Lake, P. W.; Dunham, G.; Cuneo, M. E.; Deeney, C.; Fisher, D. V.; Fisher, V. I.; Bernshtam, V.; Starobinets, A.; Weingarten, L.

    2011-11-01

    The observation of Doppler splitting in K-shell x-ray lines emitted from optically thin dopants is used to infer implosion velocities of up to 70 cm/μs in wire-array and gas-puff Z pinches at drive currents of 15-20 MA. These data can benchmark numerical implosion models, which produce reasonable agreement with the measured velocity in the emitting region. Doppler splitting is obscured in lines with strong opacity, but red-shifted absorption produced by the cooler halo of material backlit by the hot core assembling on axis can be used to diagnose velocity in the trailing mass.

  16. Measurements of Terminal Velocities of Cirrus Clouds in the Upper Trosphere

    NASA Astrophysics Data System (ADS)

    Bai Nee, Jan; Chen, W. N.; Chiang, C. W.; Das, S. K.

    2016-06-01

    Cirrus clouds are composed of ice crystals condensed from humidity due to low temperature condition in the upper atmosphere. The microphysics of cirrus clouds including sizes and shapes of ice particles are not well understood but are important in climate modeling. Ice crystal will fall under gravitational sedimentation to reach terminal velocities which depend on the size, mass, and ice habit. We studied here the terminal velocity of cirrus clouds by using lidar observations at Chungli (25N, 121E). The terminal velocities for a few cases of stable cirrus clouds are measured to determine the ice particle sizes and processes in the upper atmosphere.

  17. VELOCITY-FIELD MEASUREMENTS OF A SHOCK-ACCELERATED FLUID INSTABILITY

    SciTech Connect

    K. PRESTRIDGE; C. ZOLID; ET AL

    2001-05-01

    A cylinder of heavy gas (SF{sub 6}) in air is hit by a Mach 1.2 shock. The resultant Richtmyer-Meshkov instability is observed as it propagates through the test section of the shock tube. Six images are taken after shock impact, and the velocity field at one time is measured using Particle Image Velocimetry (PIV). The images of the density field show the development of a secondary instability in the cylinder. The velocity field provides us with information about the magnitudes of the velocities as well as the magnitude of the vorticity in the flow.

  18. Measurement of velocity deficit at the downstream of a 1:10 axial hydrokinetic turbine model

    SciTech Connect

    Gunawan, Budi; Neary, Vincent S; Hill, Craig; Chamorro, Leonardo

    2012-01-01

    Wake recovery constrains the downstream spacing and density of turbines that can be deployed in turbine farms and limits the amount of energy that can be produced at a hydrokinetic energy site. This study investigates the wake recovery at the downstream of a 1:10 axial flow turbine model using a pulse-to-pulse coherent Acoustic Doppler Profiler (ADP). In addition, turbine inflow and outflow velocities were measured for calculating the thrust on the turbine. The result shows that the depth-averaged longitudinal velocity recovers to 97% of the inflow velocity at 35 turbine diameter (D) downstream of the turbine.

  19. Distance and velocity measurements by the use of an orthogonal Michelson interferometer.

    PubMed

    Chang, Y S; Chien, P Y; Chang, M W

    1997-01-01

    A novel signal processing scheme for detecting distance and velocity signals simultaneously is demonstrated. In this method, a frequency-modulated diode laser is used to illuminate a dual-channel Michelson interferometer with two orthogonal output signals. The distance and the velocity signals then exist on the beat frequencies of the output interferometric signal. Two interferometric output signals with a quadrature phase shift are used to adjust the gating time period of frequency counters for beat-frequency measurement. The distance and velocity signals can thus be obtained from the counting number within the gated-in time period.

  20. Measurement of gas flow velocity: anemometer with a vibrating hot wire.

    PubMed

    Kiełbasa, Jan

    2010-01-01

    I propose a new method to measure velocity of a gas flow, which utilizes the time derivative of the voltage observed on a vibrating hot-wire sensor. The wire vibrates with an amplitude a and a frequency f, and is kept perpendicular to the gas flow direction in the plane containing the flow velocity vector v(g). When the parameters of vibrations are tuned, the number of zeros per vibration period of the hot-wire voltage function changes. I demonstrate that at the point of change, the unknown gas velocity is directly expressed by the parameters of vibrations v(g)=2pifa. Therefore, the velocity can be measured without any prior calibration of the hot-wire speed-voltage curve and the method can be used for gases of slowly changing temperature or composition.

  1. An experiment to measure the one-way velocity of propagation of electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Kolen, P.; Torr, D. G.

    1982-01-01

    An experiment involving commercially available instrumentation to measure the velocity of the earth with respect to absolute space is described. The experiment involves the measurement of the one-way propagation velocity of electromagnetic radiation down a high-quality coaxial cable. It is demonstrated that the experiment is both physically meaningful and exceedingly simple in concept and in implementation. It is shown that with currently available commercial equipment one might expect to detect a threshold value for the component of velocity of the earth's motion with respect to absolute space in the equatorial plane of approximately 10 km/s, which greatly exceeds the velocity resolution required to detect the motion of the solar system with respect to the center of the galaxy.

  2. Unsteady-flow velocity measurements around an intake valve of a reciprocating engine

    SciTech Connect

    El Tahry, S.H.; Khalighi, B.; Kuziak, W.R. Jr.

    1987-01-01

    In the present work, measurements of the velocity profiles in the valve curtain area of an internal combustion engine were made using hot-wire anemometry. The three components of velocity were measured under a variety of engine speeds, valve lifts, and inlet pipe configurations. From an analysis of the results, it was found that during the intake stroke, a region spanning about 60 crank angle degrees and centered at the middle of the intake stroke could be identified where transient effects had little effect on the intake velocity profiles. In this region, the velocity profiles were fairly insensitive to engine speed and to the type of inlet pipe used, but were sensitive to the valve lift. Surrounding this region, in the early and late parts of the intake stroke, the profiles were found to be influenced by transient effects and were sensitive to engine speed, type of inlet pipe, and valve lift.

  3. Sound-velocity measurements for HFC-134a and HFC-152a with a spherical resonator

    NASA Astrophysics Data System (ADS)

    Hozumi, T.; Koga, T.; Sato, H.; Watanabe, K.

    1993-07-01

    A spherical acoustic resonator was developed for measuring sound velocities in the gaseous phase and ideal-gas specific heats for new refrigerants. The radius of the spherical resonator, being about 5 cm, was determined by measuring sound velocities in gaseous argon at temperatures from 273 to 348 K and pressures up to 240 kPa. The measurements of 23 sound velocities in gaseous HFC-134a (1,1,1,2-tetrafluoroethane) at temperatures of 273 and 298 K and pressures from 10 to 250 kPa agree well with the measurements of Goodwin and Moldover. In addition, 92 sound velocities in gaseous HFC-152a (1,1-difluoroethane) with an accuracy of ±0.01% were measured at temperatures from 273 to 348 K and pressures up to 250 kPa. The ideal-gas specific heats as well as the second acoustic virial coefficients have been obtained for both these important alternative refrigerants. The second virial coefficients for HFC-152a derived from the present sound velocity measurements agree extremely well with the reported second virial coefficient values obtained with a Burnett apparatus.

  4. Shock-induced phase transition of Tin: Experimental study with velocity and temperature measurements

    NASA Astrophysics Data System (ADS)

    Chauvin, Camille; Bouchkour, Zakaria; Sinatti, Frédéric; Petit, Jacques

    2017-01-01

    To investigate polymorphic transition and melting on release of Tin, experiments under shock wave compression have been carried out from 10 GPa to 44 GPa with both velocity and temperature measurements. Interface Sn/LiF velocity has been recorded using Photon Doppler Velocimeter (PDV) measurement technique and interface Sn/LiF temperature has been performed thanks to an optical pyrometer appropriate to detect low and high temperatures (respectively <1000 K and > 1000 K). While PDV measurements are common and accurate, temperature remains often imprecise due to the lack of knowledge on the emissivity of the sample. The use of an emissive layer at the interface Sn/LiF helps to estimate an accurate temperature measurement which can be compared to our numerical simulations. The profiles of both velocity and radiance records are in good agreement and display the polymorphic transition and the melting on release of Tin. Besides, temperature profiles can show complementary singularities particularly during phase transition, not visible on velocity profiles. This paper will discuss the evidence of phase transitions on temperature measurements, the complementarity with velocity measurements and the advantages of an emissive layer.

  5. Adaptive method for quantifying uncertainty in discharge measurements using velocity-area method.

    NASA Astrophysics Data System (ADS)

    Despax, Aurélien; Favre, Anne-Catherine; Belleville, Arnaud

    2015-04-01

    Streamflow information provided by hydrometric services such as EDF-DTG allow real time monitoring of rivers, streamflow forecasting, paramount hydrological studies and engineering design. In open channels, the traditional approach to measure flow uses a rating curve, which is an indirect method to estimate the discharge in rivers based on water level and punctual discharge measurements. A large proportion of these discharge measurements are performed using the velocity-area method; it consists in integrating flow velocities and depths through the cross-section [1]. The velocity field is estimated by choosing a number m of verticals, distributed across the river, where vertical velocity profile is sampled by a current-meter at ni different depths. Uncertainties coming from several sources are related to the measurement process. To date, the framework for assessing uncertainty in velocity-area discharge measurements is the method presented in the ISO 748 standard [2] which follows the GUM [3] approach. The equation for the combined uncertainty in measured discharge u(Q), at 68% level of confidence, proposed by the ISO 748 standard is expressed as: Σ 2 2 2 -q2i[u2(Bi)+-u2(Di)+-u2p(Vi)+-(1ni) ×-[u2c(Vi)+-u2exp(Vi)

  6. Instantaneous velocity field measurement of objects in coaxial rotation using digital image velocimetry

    NASA Technical Reports Server (NTRS)

    Cho, Y.-C.; Park, H.

    1990-01-01

    The instantaneous velocity fields of time-dependent flows, or of a collection of objects moving with spatially varying velocities, can be measured by means of digital image velocimetry (DIV). DIV overcomes several shortcomings of such existing techniques as laser-speckle or particle-image velocimetry. Attention is presently given to numerically generated images representing objects in uniform motion which are then used for the experimental validation of DIV.

  7. Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Lau, Matthew

    2011-01-01

    The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

  8. Measurement of irregularities in angular velocities of rotating assemblies in memory devices on magnetic carriers

    NASA Technical Reports Server (NTRS)

    Virakas, G. I.; Matsyulevichyus, R. A.; Minkevichyus, K. P.; Potsyus, Z. Y.; Shirvinskas, B. D.

    1973-01-01

    Problems in measurement of irregularities in angular velocity of rotating assemblies in memory devices with rigid and flexible magnetic data carriers are discussed. A device and method for determination of change in angular velocities in various frequency and rotation rate ranges are examined. A schematic diagram of a photoelectric sensor for recording the signal pulses is provided. Mathematical models are developed to show the amount of error which can result from misalignment of the test equipment.

  9. Assimilation of Sonic Velocity and Thin Section Measurements from the NEEM Ice Core

    NASA Astrophysics Data System (ADS)

    Hay, Michael; Pettit, Erin; Kluskiewicz, Dan; Waddington, Edwin

    2016-04-01

    We examine the measurement of crystal orientation fabric (COF) in ice cores using thin sections and sound-wave velocities, focusing on the NEEM core in Greenland. Ice crystals have substantial plastic anisotropy, with shear orthogonal to the crystallographic c-axis occuring far more easily than deformation in other orientations. Due to strain-induced grain-rotation, COFs can become highly anisotropic, resulting in bulk anisotropic flow. Thin-section measurements taken from ice cores allow sampling of the crystal fabric distribution. Thin-section measurements, however, suffer from sampling error, as they sample a small amount of ice, usually on the order of a hundred grans. They are typically only taken at intervals of several meters, which means that meter-scale variations in crystal fabric are difficult to capture. Measuring sonic velocities in ice cores provides an alternate method of determining crystal fabric. The speed of vertical compression waves is affected by the vertical clustering of c-axes, but is insensitive to azimuthal fabric anisotropy. By measuring splitting between the fast and slow shear-wave directions, information on the azimuthal distribution of orientations can be captured. Sonic-velocity measurements cannot capture detailed information on the orientation distribution of the COF, but they complement thin-section measurements with several advantages. Sonic-logging measurements can be taken at very short intervals, eliminating spatial gaps. In addition, sonic logging samples a large volume of ice with each measurement, reducing sampling error. Our logging tool has a depth resolution of around 3m/s, and can measure velocity features on the order of 1m/s. Here, we show the results of compression-wave measurements at NEEM. We also combine sonic-velocity measurements and thin-section measurements to produce a more accurate and spatially-complete representation of ice-crystal orientations in the vicinity of the NEEM core.

  10. In vivo PIV measurement of red blood cell velocity field in microvessels considering mesentery motion.

    PubMed

    Sugii, Yasuhiko; Nishio, Shigeru; Okamoto, Koji

    2002-05-01

    As endothelial cells are subject to flow shear stress, it is important to determine the detailed velocity distribution in microvessels in the study of mechanical interactions between blood and endothelium. Recently, particle image velocimetry (PIV) has been proposed as a quantitative method of measuring velocity fields instantaneously in experimental fluid mechanics. The authors have developed a highly accurate PIV technique with improved dynamic range. spatial resolution and measurement accuracy. In this paper, the proposed method was applied to images of the arteriole in the rat mesentery using an intravital microscope and high-speed digital video system. Taking the mesentery motion into account, the PIV technique was improved to measure red blood cell (RBC) velocity. Velocity distributions with spatial resolutions of 0.8 x 0.8 microm were obtained even near the wall in the centre plane of the arteriole. The arteriole velocity profile was blunt in the centre region of the vessel cross-section and sharp in the near-wall region. Typical flow features for non-Newtonian fluid were shown. Time-averaged velocity profiles in six cross sections with different diameters were compared.

  11. Characterization of the alumina-zirconia ceramic system by ultrasonic velocity measurements

    SciTech Connect

    Carreon, Hector; Ruiz, Alberto; Medina, Ariosto; Barrera, Gerardo; Zarate, Juan

    2009-08-15

    In this work an alumina-zirconia ceramic composites have been prepared with {alpha}-Al{sub 2}O{sub 3} contents from 10 to 95 wt.%. The alumina-zirconia ceramic system was characterized by means of precise ultrasonic velocity measurements. In order to find out the factors affecting the variation in wave velocity, the ceramic composite have been examined by X-ray diffraction (XRD) and (SEM) scanning electron microscopy. It was found that the ultrasonic velocity measurements changed considerably with respect to the ceramic composite composition. In particular, we studied the behavior of the physical material property hardness, an important parameter of the ceramic composite mechanical properties, with respect to the variation in the longitudinal and shear wave velocities. Shear wave velocities exhibited a stronger interaction with microstructural and sub-structural features as compared to that of longitudinal waves. In particular, this phenomena was observed for the highest {alpha}-Al{sub 2}O{sub 3} content composite. Interestingly, an excellent correlation between ultrasonic velocity measurements and ceramic composite hardness was observed.

  12. Velocity measurement of pneumatically conveyed solid particles using an electrostatic sensor

    NASA Astrophysics Data System (ADS)

    Xu, C.; Zhou, B.; Yang, D.; Tang, G.; Wang, S.

    2008-02-01

    The paper proposes a method to measure the mean velocity of solid particles based on the spatial filtering effect of the electrostatic sensor. To determine the relationship between the spatial frequency characteristics of the sensor and solid particle velocity, a general formula is derived by analyzing quantitatively the spatial filtering characteristics of the electrostatic sensor along with the accepted assumptions. The effects of the geometric parameters of the sensor, particle velocity distribution, particle concentration distribution over the cross-section of a pneumatic pipeline, particle size, particle material type and frequency resolution on particle velocity measurement accuracy are also discussed in detail. Experiments are performed on a bench-scale gravity-fed particle flow experimental rig to test the performance of the velocity measurement system. The off-line experimental results show that the system repeatability is within ±5% over the velocity range of 2-6 m s-1 for concentrations of solid particles in the range of 0.5-6.0%.

  13. Optimization of Doppler velocity echocardiographic measurements using an automatic contour detection method.

    PubMed

    Gaillard, E; Kadem, L; Pibarot, P; Durand, L-G

    2009-01-01

    Intra- and inter-observer variability in Doppler velocity echocardiographic measurements (DVEM) is a significant issue. Indeed, imprecisions of DVEM can lead to diagnostic errors, particularly in the quantification of the severity of heart valve dysfunction. To minimize the variability and rapidity of DVEM, we have developed an automatic method of Doppler velocity wave contour detection, based on active contour models. To validate our new method, results obtained with this method were compared to those obtained manually by an experienced echocardiographer on Doppler echocardiographic images of left ventricular outflow tract and transvalvular flow velocity signals recorded in 30 patients, 15 with aortic stenosis and 15 with mitral stenosis. We focused on three essential variables that are measured routinely by Doppler echocardiography in the clinical setting: the maximum velocity, the mean velocity and the velocity-time integral. Comparison between the two methods has shown a very good agreement (linear correlation coefficient R(2) = 0.99 between the automatically and the manually extracted variables). Moreover, the computation time was really short, about 5s. This new method applied to DVEM could, therefore, provide a useful tool to eliminate the intra- and inter-observer variabilities associated with DVEM and thereby to improve the diagnosis of cardiovascular disease. This automatic method could also allow the echocardiographer to realize these measurements within a much shorter period of time compared to standard manual tracing method. From a practical point of view, the model developed can be easily implanted in a standard echocardiographic system.

  14. Optimization of detonation velocity measurements using a chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Barbarin, Y.; Lefrançois, A.; Zaniolo, G.; Chuzeville, V.; Jacquet, L.; Magne, S.; Luc, J.; Osmont, A.

    2015-05-01

    Dynamic measurements of detonation velocity profiles are performed using long Chirped Fiber Bragg Gratings (CFBGs). Such thin probes, with a diameter of typically 150 μm, are inserted directly into a high explosive sample or simply positioned laterally. During the detonation, the width of the reflected optical spectrum is continuously reduced by the propagation of the wave-front, which physically shortens the CFBG. The reflected optical intensity delivers a ramp down signal type, which is directly related to the detonation velocity profile. Experimental detonation velocity measurements were performed on the side of three different high explosives (TNT, B2238 and V401) in a bare cylindrical stick configuration (diameter: 2 inches, height: 10 inches). The detonation velocity range covered was 6800 to 9000 m/s. The extraction of the detonation velocity profiles requires a careful calibration of the system and of the CFBG used. A calibration procedure was developed, with the support of optical simulations, to cancel out the optical spectrum distortions from the different optical components and to determine the wavelength-position transfer function of the CFBG in a reproducible way. The 40-mm long CFBGs were positioned within the second half of the three high explosive cylinders. The excellent linearity of the computed position-time diagram confirms that the detonation was established for the three high explosives. The fitted slopes of the position-time diagram give detonation velocity values which are in very good agreement with the classical measurements obtained from discrete electrical shorting pins.

  15. Pilot model expansion tunnel test flow properties obtained from velocity, pressure, and probe measurements

    NASA Technical Reports Server (NTRS)

    Friesen, W. J.; Moore, J. A.

    1973-01-01

    Velocity-profile, pitot-pressure, and supplemental probe measurements were made at the nozzle exist of an expansion tunnel (a modification to the Langley pilot model expansion tube) for a nozzle net condition of a nitrogen test sample with a velocity of 4.5 km/sec and a density 0.005 times the density of nitrogen at standard conditions, both with the nozzle initially immersed in a helium atmosphere and with the nozzle initially evacuated. The purpose of the report is to present the results of these measurements and some of the physical properties of the nitrogen test sample which can be inferred from the measured results. The main conclusions reached are that: the velocity profiles differ for two nozzle conditions; regions of the flow field can be found where the velocity is uniform to within 5 percent and constant for several hundred microseconds; the velocity of the nitrogen test sample is reduced due to passage through the nozzle; and the velocity profiles do not significantly reflect the large variations which occur in the inferred density profiles.

  16. A novel velocity measuring system for fragments based on retroreflective laser screen

    NASA Astrophysics Data System (ADS)

    Zhao, Donge; Zhou, Hanchang

    2011-06-01

    The flying velocity of fragment is a key parameter to evaluate the damage power of warhead. Due to small volume, large amount, irregular shape, high velocity, arbitrary flying direction, wide distribution and serious measuring environment, it's very difficult to measuring the velocity of fragment. We adopt two fan-shaped laser screens combining with retroreflective cooperation objects to construct detect module, and break through the laser screen transmitting-receiving integration optoelectronic detection technique. The signals of the fragment flying through the screens are collected, saved and processed by software. The system can realize a real-time, non-contact, reproducible, all-weather optoelectronic measurement for fragment velocity during warhead explosion. Using the developed prototype, we successfully acquired the analog signals when five fragments flying through two laser screens for certain an explosion warhead, and obtained their velocities which can be regarded as instantaneous velocities at the midpoint between two screens. The result validates the accuracy of the method and its feasibility of engineering application.

  17. Molecular Rayleigh Scattering Techniques Developed for Measuring Gas Flow Velocity, Density, Temperature, and Turbulence

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Seasholtz, Richard G.; Elam, Kristie A.; Panda, Jayanta

    2005-01-01

    Nonintrusive optical point-wise measurement techniques utilizing the principles of molecular Rayleigh scattering have been developed at the NASA Glenn Research Center to obtain time-averaged information about gas velocity, density, temperature, and turbulence, or dynamic information about gas velocity and density in unseeded flows. These techniques enable measurements that are necessary for validating computational fluid dynamics (CFD) and computational aeroacoustic (CAA) codes. Dynamic measurements allow the calculation of power spectra for the various flow properties. This type of information is currently being used in jet noise studies, correlating sound pressure fluctuations with velocity and density fluctuations to determine noise sources in jets. These nonintrusive techniques are particularly useful in supersonic flows, where seeding the flow with particles is not an option, and where the environment is too harsh for hot-wire measurements.

  18. Rayleigh Scattering Diagnostic for Measurement of Temperature and Velocity in Harsh Environments

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Greer, Lawrence C., III

    1998-01-01

    A molecular Rayleigh scattering system for temperature and velocity measurements in unseeded flows is described. The system is capable of making measurements in the harsh environments commonly found in aerospace test facilities, which may have high acoustic sound levels, varying temperatures, and high vibration levels. Light from an argon-ion laser is transmitted via an optical fiber to a remote location where two flow experiments were located. One was a subsonic free air jet; the second was a low-speed heated airjet. Rayleigh scattered light from the probe volume was transmitted through another optical fiber from the remote location to a controlled environment where a Fabry-Perot interferometer and cooled CCD camera were used to analyze the Rayleigh scattered light. Good agreement between the measured velocity and the velocity calculated from isentropic flow relations was demonstrated (less than 5 m/sec). The temperature measurements, however, exhibited systematic errors on the order of 10-15%.

  19. Combined CARS/LDA instrument for simultaneous temperature and velocity measurements

    NASA Astrophysics Data System (ADS)

    Goss, L. P.; Trump, D. D.; Roquemore, W. M.

    1988-01-01

    The performance of a combined CARS/LDA instrument capable of measuring temperature and two velocity components with a time coincidence of about 4 μs is evaluated in a turbulent premixed propane-air Bunsen-burner flame. Measurements near the base of the flame exhibit negative axial correlations, indicative of normal gradient transport; those near the flame tip show strong positive axial correlations, indicative of transport counter to the temperature gradient. The radial correlations are positive both in the reaction zone and in the plume. An analysis of temperature data from measurements made (1) independent of and (2) coincidental with LDA measurements indicates that the CARS/LDA instrument provides a density-weighted velocity, temperature, and velocity temperature correlation due to the density variations in the flame.

  20. Mean Velocity, Turbulence Intensity and Turbulence Convection Velocity Measurements for a Convergent Nozzle in a Free Jet Wind Tunnel. Comprehensive Data Report

    NASA Technical Reports Server (NTRS)

    Mccolgan, C. J.; Larson, R. S.

    1977-01-01

    The effect of flight on the mean flow and turbulence properties of a 0.056m circular jet were determined in a free jet wind tunnel. The nozzle exit velocity was 122 m/sec, and the wind tunnel velocity was set at 0, 12, 37, and 61 m/sec. Measurements of flow properties including mean velocity, turbulence intensity and spectra, and eddy convection velocity were carried out using two linearized hot wire anemometers. This report contains the raw data and graphical presentations. The final technical report includes a description of the test facilities, test hardware, along with significant test results and conclusions.

  1. High-resolution OH LIF velocity measurement technique for high-speed reacting flows

    NASA Technical Reports Server (NTRS)

    Klavuhn, K. G.; Gauba, G.; Mcdaniel, J. C.

    1992-01-01

    A nonintrusive optical technique was developed for the quantitative study of velocity fields in steady, high-speed, reacting flows. A narrow-linewidth laser source was tuned through an isolated OH absorption line to measure the Doppler-shifted linecenter frequency relative to an iodine reference line. A counterpropagating beam approach was used to eliminate collisional impact shift effects. Pointwise measurements of velocity were made in a unique reacting underexpanded jet facility as an extensive calibration of the technique over a wide range of flow conditions. The extension of the technique to planar measurements is also discussed.

  2. Feasibility of using a reliable automated Doppler flow velocity measurements for research and clinical practices

    NASA Astrophysics Data System (ADS)

    Zolgharni, Massoud; Dhutia, Niti M.; Cole, Graham D.; Willson, Keith; Francis, Darrel P.

    2014-03-01

    Echocardiographers are often unkeen to make the considerable time investment to make additional multiple measurements of Doppler velocity. Main hurdle to obtaining multiple measurements is the time required to manually trace a series of Doppler traces. To make it easier to analyse more beats, we present an automated system for Doppler envelope quantification. It analyses long Doppler strips, spanning many heartbeats, and does not require the electrocardiogram to isolate individual beats. We tested its measurement of velocity-time-integral and peak-velocity against the reference standard defined as the average of three experts who each made three separate measurements. The automated measurements of velocity-time-integral showed strong correspondence (R2 = 0.94) and good Bland-Altman agreement (SD = 6.92%) with the reference consensus expert values, and indeed performed as well as the individual experts (R2 = 0.90 to 0.96, SD = 5.66% to 7.64%). The same performance was observed for peak-velocities; (R2 = 0.98, SD = 2.95%) and (R2 = 0.93 to 0.98, SD = 2.94% to 5.12%). This automated technology allows <10 times as many beats to be acquired and analysed compared to the conventional manual approach, with each beat maintaining its accuracy.

  3. Design of a Non-scanning Lidar for Wind Velocity and Direction Measurement

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Peng, Zhangxian

    2016-06-01

    A Doppler lidar system for wind velocity and direction measurement is presented. The lidar use a wide field of view (FOV) objective lens as an optical antenna for both beam transmitting and signal receiving. By four fibers coupled on different position on the focal plane, the lidar can implement wind vector measurement without any scanning movement.

  4. Measurement of Velocity and Power Balance in a Two-Dimensional MPD Arcjet

    NASA Astrophysics Data System (ADS)

    Kinefuchi, Kiyoshi; Funaki, Ikkoh; Toki, Kyoichiro; Shimizu, Yukio

    Velocity and temperature measurements were conducted for a two-dimensional magnetoplasmadynamic arcjet with hydrogen propellant. To obtain the velocities of both atoms and ions, laser absorption spectroscopy was employed for atom, and time-of-flight technique was used for ions. In a quasi-steady operation at 13kA/0.65g/s, larger ions velocity (33km/s) than that of the atoms (13km/s) was found in the case of flared anode configuration, which implies that large mean free path between the ions and atoms prohibited momentum transfer from the ions to the neutral particles. This velocity difference was not observed in the case of converging-diverging anode, where the high-density plasma inside the discharge chamber enhances momentum transfer from ions to atoms. In addition to the velocity difference, diagnostics by probe methods revealed high ion temperature in comparison with that of electrons at the thruster exit. Using the velocities and temperatures together with the densities of each particle, energy flux of the magnetoplasmadynamic arcjet was discussed. The large energy deposition into thermal and internal energy modes near the thruster exit indicated a large amount of pressure energy that should be converted to velocity energy by an appropriate nozzle design to further improve the thrust performance.

  5. Evaluation of agreement between temporal series obtained from electrocardiogram and pulse wave.

    NASA Astrophysics Data System (ADS)

    Leikan, GM; Rossi, E.; Sanz, MCuadra; Delisle Rodríguez, D.; Mántaras, MC; Nicolet, J.; Zapata, D.; Lapyckyj, I.; Siri, L. Nicola; Perrone, MS

    2016-04-01

    Heart rate variability allows to study the cardiovascular autonomic nervous system modulation. Usually, this signal is obtained from the electrocardiogram (ECG). A simpler method for recording the pulse wave (PW) is by means of finger photoplethysmography (PPG), which also provides information about the duration of the cardiac cycle. In this study, the correlation and agreement between the time series of the intervals between heartbeats obtained from the ECG with those obtained from the PPG, were studied. Signals analyzed were obtained from young, healthy and resting subjects. For statistical analysis, the Pearson correlation coefficient and the Bland and Altman limits of agreement were used. Results show that the time series constructed from the PW would not replace the ones obtained from ECG.

  6. [Experimental use of intraoperative pulse wave Doppler in the study of vascular microanastomosis].

    PubMed

    La Rosa, A; Bonoldi, A P; Bagliani, A; Pagella, C; Rossi, D; Digiacomo, A; Zonta, A

    1990-02-01

    Personal experience with pulse wave Doppler (PWD) at 20 MHz with real time signal spectral analysis in FFT (Fast Fourier Transform), for the valuation of the vascular microanastomosis patency degree is reported. Fifty-nine Sprague-Dawley rats have been studied after abdominal aorta dissection: in 19 (group A) an organic stenosis has been simulated varying from 5% to 95% by a 8/0 silk suture; in 40 rats (group B and C) we the abdominal aorta was stitched with interrupted suture after transversal section. In the group C (20 rats) a longitudinal arteriotomy on abdominal aorta within 10-15 min from anastomosis was performed to value under microscopic control the suture line. The PWD technique is able to recognize stenoses more than 10% of intraluminal diameter, showing a higher sensibility than traditional techniques.

  7. Comparison of phase velocities from array measurements of Rayleigh waves associated with microtremor and results calculated from borehole shear-wave velocity profiles

    USGS Publications Warehouse

    Liu, Hsi-Ping; Boore, David M.; Joyner, William B.; Oppenheimer, David H.; Warrick, Richard E.; Zhang, Wenbo; Hamilton, John C.; Brown, Leo T.

    2000-01-01

    Shear-wave velocities (VS) are widely used for earthquake ground-motion site characterization. VS data are now largely obtained using borehole methods. Drilling holes, however, is expensive. Nonintrusive surface methods are inexpensive for obtaining VS information, but not many comparisons with direct borehole measurements have been published. Because different assumptions are used in data interpretation of each surface method and public safety is involved in site characterization for engineering structures, it is important to validate the surface methods by additional comparisons with borehole measurements. We compare results obtained from a particular surface method (array measurement of surface waves associated with microtremor) with results obtained from borehole methods. Using a 10-element nested-triangular array of 100-m aperture, we measured surface-wave phase velocities at two California sites, Garner Valley near Hemet and Hollister Municipal Airport. The Garner Valley site is located at an ancient lake bed where water-saturated sediment overlies decomposed granite on top of granite bedrock. Our array was deployed at a location where seismic velocities had been determined to a depth of 500 m by borehole methods. At Hollister, where the near-surface sediment consists of clay, sand, and gravel, we determined phase velocities using an array located close to a 60-m deep borehole where downhole velocity logs already exist. Because we want to assess the measurements uncomplicated by uncertainties introduced by the inversion process, we compare our phase-velocity results with the borehole VS depth profile by calculating fundamental-mode Rayleigh-wave phase velocities from an earth model constructed from the borehole data. For wavelengths less than ~2 times of the array aperture at Garner Valley, phase-velocity results from array measurements agree with the calculated Rayleigh-wave velocities to better than 11%. Measurement errors become larger for wavelengths 2

  8. Acoustic resolution photoacoustic Doppler velocity measurements in fluids using time-domain cross-correlation

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2013-03-01

    Blood flow measurements have been demonstrated using the acoustic resolution mode of photoacoustic sensing. This is unlike previous flowmetry methods using the optical resolution mode, which limits the maximum penetration depth to approximately 1mm. Here we describe a pulsed time correlation photoacoustic Doppler technique that is inherently flexible, lending itself to both resolution modes. Doppler time shifts are quantified via cross-correlation of pairs of photoacoustic waveforms generated in moving absorbers using pairs of laser light pulses, and the photoacoustic waves detected using an ultrasound transducer. The acoustic resolution mode is employed by using the transducer focal width, rather than the large illuminated volume, to define the lateral spatial resolution. The use of short laser pulses allows depth-resolved measurements to be obtained with high spatial resolution, offering the prospect of mapping flow within microcirculation. Whilst our previous work has been limited to a non-fluid phantom, we now demonstrate measurements in more realistic blood-mimicking phantoms incorporating fluid suspensions of microspheres flowing along an optically transparent tube. Velocities up to 110 mm/s were measured with accuracies approaching 1% of the known velocities, and resolutions of a few mm/s. The velocity range and resolution are scalable with excitation pulse separation, but the maximum measurable velocity was considerably smaller than the value expected from the detector focal beam width. Measurements were also made for blood flowing at velocities up to 13.5 mm/s. This was for a sample reduced to 5% of the normal haematocrit; increasing the red blood cell concentration limited the maximum measurable velocity so that no results were obtained for concentrations greater than 20% of a physiologically realistic haematocrit. There are several possible causes for this limitation; these include the detector bandwidth and irregularities in the flow pattern. Better

  9. Development of thermal image velocimetry techniques to measure the water surface velocity

    NASA Astrophysics Data System (ADS)

    Saket, A.; Peirson, W. L.; Banner, M. L.; Barthelemy, X.

    2016-05-01

    Particle image velocimetry (PIV) is a state-of-the-art non-intrusive technique for velocity and fluid flow measurements. Due to ongoing improvements in image hardware and processing techniques, the diversity of applications of the PIV method continues to increase. This study presents an accurate thermal image velocimetry (TIV) technique using a CO2 laser source to measure the surface wave particle velocity using infrared imagery. Experiments were carried out in a 2-D wind wave flume with glass side walls for deep-water monochromatic and group waves. It was shown that the TIV technique is robust for both unforced and wind-forced group wave studies. Surface wave particles attain their highest velocity at the group crest maximum and slow down thereafter. As previously observed, each wave crest slows down as it approaches its crest maximum but this study demonstrates that the minimum crest speed coincides with maximum water velocity at the wave crest. Present results indicate that breaking is initiated once the water surface particle velocity at the wave crest exceeds a set proportion of the velocity of the slowing crest as it passes through the maximum of a wave group.

  10. Coda wave interferometry for the measurement of thermally induced ultrasonic velocity variations in CFRP laminates

    NASA Astrophysics Data System (ADS)

    Livings, Richard; Dayal, Vinay; Barnard, Dan

    2016-02-01

    Ultrasonic velocity measurement is a well-established method to measure properties and estimate strength as well as detect and locate damage. Determination of accurate and repeatable ultrasonic wave velocities can be difficult due to the influence of environmental and experimental factors. Diffuse fields created by a multiple scattering environment have been shown to be sensitive to homogeneous strain fields such as those caused by temperature variations, and Coda Wave Interferometry has been used to measure the thermally induced ultrasonic velocity variation in concrete, aluminum, and the Earth's crust. In this work, we analyzed the influence of several parameters of the experimental configuration on the measurement of thermally induced ultrasonic velocity variations in a carbon-fiber reinforced polymer plate. Coda Wave Interferometry was used to determine the relative velocity change between a baseline signal taken at room temperature and the signal taken at various temperatures. The influence of several parameters of the experimental configuration, such as the material type, the receiver aperture size, and fiber orientation on the results of the processing algorithm was evaluated in order to determine the optimal experimental configuration.---This work is supported by the NSF Industry/University Cooperative Research Program of the Center for Nondestructive Evaluation at Iowa State University.

  11. System identification of velocity mechanomyogram measured with a capacitor microphone for muscle stiffness estimation.

    PubMed

    Uchiyama, Takanori; Tomoshige, Taiki

    2017-04-01

    A mechanomyogram (MMG) measured with a displacement sensor (displacement MMG) can provide a better estimation of longitudinal muscle stiffness than that measured with an acceleration sensor (acceleration MMG), but the displacement MMG cannot provide transverse muscle stiffness. We propose a method to estimate both longitudinal and transverse muscle stiffness from a velocity MMG using a system identification technique. The aims of this study are to show the advantages of the proposed method. The velocity MMG was measured using a capacitor microphone and a differential circuit, and the MMG, evoked by electrical stimulation, of the tibialis anterior muscle was measured five times in seven healthy young male volunteers. The evoked MMG system was identified using the singular value decomposition method and was approximated with a fourth-order model, which provides two undamped natural frequencies corresponding to the longitudinal and transverse muscle stiffness. The fluctuation of the undamped natural frequencies estimated from the velocity MMG was significantly smaller than that from the acceleration MMG. There was no significant difference between the fluctuations of the undamped natural frequencies estimated from the velocity MMG and that from the displacement MMG. The proposed method using the velocity MMG is thus more advantageous for muscle stiffness estimation.

  12. Influence of precession on velocity measurements in a strong laboratory vortex

    NASA Astrophysics Data System (ADS)

    Wunenburger, R.; Andreotti, B.; Petitjeans, P.

    A strong laboratory vortex is generated in a cylindrical cell using a rotating disk and stretched by pumping the fluid out through a hole in the centre of the top of the cell. The velocity field is measured by means of laser Doppler anemometry and Doppler ultrasonic anemometry which are both non intrusive methods. The vortex exhibits a slight precession which induces temporal fluctuations of the velocity at the measurement point. Due to the centrifugal force, the tracers concentrate in a tubular region around the vortex, leading to spatial variations of the measurement counting rate. Under these two effects, the probability density function (PDF) of the one point velocity exhibits a strong non-Gaussian behaviour. In order to access the details of the velocity profile of the vortex in its own system of reference, the influence of the vortex precession, of the spatial variations of the concentration in tracers and of the intrinsic measurement dispersion is investigated and a model is proposed. It allows to recover statistically the characteristics of the vortex and to deduce the trajectory of its centre from the instantaneous velocity profiles.

  13. Measurements of Dendritic Growth Velocities in Undercooled Melts of Pure Nickel Under Static Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Gao, Jianrong; Zhang, Zongning; Zhang, Yingjie

    2012-01-01

    Dendritic growth velocities in undercooled melts of pure Ni have been intensively studied over the past fifty years. However, the literature data are at marked variance with the prediction of the widely accepted model for rapid dendritic growth both at small and at large undercoolings. In the present work, bulk melts of pure Ni samples of high purity were undercooled by glass fluxing treatment under a static magnetic field. The recalescence processes of the samples at different undercoolings were recorded using a high-speed camera, and were modeled using a software to determine the dendritic growth velocities. The present data confirmed the effect of melt flow on dendritic growth velocities at undercoolings below 100 K. A comparison of the present data with previous measurements on a lower purity material suggested an effect of impurities on dendritic growth velocities at undercoolings larger than 200 K as well.

  14. Relative velocity measurement from the spectral phase of a match-filtered linear frequency modulated pulse.

    PubMed

    Pinson, Samuel; Holland, Charles W

    2016-08-01

    Linear frequency modulated signals are commonly used to perform underwater acoustic measurements since they can achieve high signal-to-noise ratios with relatively low source levels. However, such signals present a drawback if the source or receiver or target is moving. The Doppler effect affects signal amplitude, delay, and resolution. To perform a correct match filtering that includes the Doppler shift requires prior knowledge of the relative velocity. In this paper, the relative velocity is extracted directly from the Doppler cross-power spectrum. More precisely, the quadratic coefficient of the Doppler cross-power-spectrum phase is proportional to the relative velocity. The proposed method achieves velocity estimates that compare favorably with Global Positioning System ground truth and the ambiguity method.

  15. Measurement of velocity and vorticity fields in the wake of an airfoil in periodic pitching motion

    NASA Astrophysics Data System (ADS)

    Booth, Earl R., Jr.

    1987-12-01

    The velocity field created by the wake of an airfoil undergoing a prescribed pitching motion was sampled using hot wire anemometry. Data analysis methods concerning resolution of velocity components from cross wire data, computation of vorticity from velocity time history data, and calculation of vortex circulation from vorticity field data are discussed. These data analysis methods are applied to a flow field relevant to a two dimensional blade-vortex interaction study. Velocity time history data were differentiated to yield vorticity field data which are used to characterize the wake of the pitching airfoil. Measurement of vortex strength in sinusoidal and nonsinusoidal wakes show vortices in the sinusoidal wake have stronger circulation and more concentrated vorticity distributions than the tailored nonsinusoidal wake.

  16. Short-term velocity measurements at Columbia Glacier, Alaska; August-September 1984

    USGS Publications Warehouse

    Vaughn, B.H.; Raymond, C.F.; Rasmussen, Lowell A.; Miller, D.S.; Michaelson, C.A.; Meier, M.F.; Krimmel, R.M.; Fountain, A.G.; Dunlap, W.W.; Brown, C.S.

    1985-01-01

    Ice velocity data are presented for the lower reach of Columbia Glacier, Alaska. The data span a 29 day period and contain 1,072 angle sightings from two survey stations to 22 markers placed on the ice surface, and 1,621 laser measurements of the distance to one of those markers (number 11) from another station. These short-interval observations were made to investigate the dynamics of the glacier and to provide input to models for estimation of future retreat and iceberg discharge. The mean ice velocity (at marker number 11) was approximately 9 m/day and ranged from 8 to < 15 m/day. The data set includes a well defined 2-day, 50% velocity increase and a clear pattern of velocity fluctuations of about 5% with approximately diurnal and semiurnal periods. (Author 's abstract)

  17. Rayleigh Scattering Diagnostic for Measurement of Velocity and Density Fluctuation Spectra

    NASA Astrophysics Data System (ADS)

    Seasholtz, Richard G.; Panda, Jayanta; Elam, Kristie A.

    2002-04-01

    A new molecular Rayleigh scattering based flow diagnostic is used for the first time to measure the power spectrum of gas density and radial velocity component in the plumes of high speed jets. The technique is based on analyzing the Rayleigh scattered light with a Fabry-Perot interferometer used in the static, imaging mode. The PC based data acquisition system is capable of simultaneous sampling of velocity and density at rates to 100 kHz and data record lengths to 10 million. Velocity and density power spectra and velocity-density cross spectra are presented for a subsonic jet, an underexpanded screeching jet, and for Mach 1.4 and Mach 1.8 supersonic jets. Software and hardware interfaces were developed to allow computer control of all aspects of the experiment and data acquisition.

  18. Rayleigh Scattering Diagnostic for Measurement of Velocity and Density Fluctuation Spectra

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, Jayanta; Elam, Kristie A.

    2002-01-01

    A new molecular Rayleigh scattering based flow diagnostic is used for the first time to measure the power spectrum of gas density and radial velocity component in the plumes of high speed jets. The technique is based on analyzing the Rayleigh scattered light with a Fabry-Perot interferometer used in the static, imaging mode. The PC based data acquisition system is capable of simultaneous sampling of velocity and density at rates to 100 kHz and data record lengths to 10 million. Velocity and density power spectra and velocity-density cross spectra are presented for a subsonic jet, an underexpanded screeching jet, and for Mach 1.4 and Mach 1.8 supersonic jets. Software and hardware interfaces were developed to allow computer control of all aspects of the experiment and data acquisition.

  19. Measurement of velocity and vorticity fields in the wake of an airfoil in periodic pitching motion

    NASA Technical Reports Server (NTRS)

    Booth, Earl R., Jr.

    1987-01-01

    The velocity field created by the wake of an airfoil undergoing a prescribed pitching motion was sampled using hot wire anemometry. Data analysis methods concerning resolution of velocity components from cross wire data, computation of vorticity from velocity time history data, and calculation of vortex circulation from vorticity field data are discussed. These data analysis methods are applied to a flow field relevant to a two dimensional blade-vortex interaction study. Velocity time history data were differentiated to yield vorticity field data which are used to characterize the wake of the pitching airfoil. Measurement of vortex strength in sinusoidal and nonsinusoidal wakes show vortices in the sinusoidal wake have stronger circulation and more concentrated vorticity distributions than the tailored nonsinusoidal wake.

  20. Rayleigh Scattering Diagnostic for Simultaneous Measurements of Dynamic Density and Velocity

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, J.

    2000-01-01

    A flow diagnostic technique based on the molecular Rayleigh scattering of laser light is used to obtain dynamic density and velocity data in turbulent flows. The technique is based on analyzing the Rayleigh scattered light with a Fabry-Perot interferometer and recording information about the interference pattern with a multiple anode photomultiplier tube (PMT). An artificial neural network is used to process the signals from the PMT to recover the velocity time history, which is then used to calculate the velocity power spectrum. The technique is illustrated using simulated data. The results of an experiment to measure the velocity power spectrum in a low speed (100 rn/sec) flow are also presented.

  1. Correlation and spectral measurements of fluctuating pressures and velocities in annular turbulent flow. [PWR; BWR

    SciTech Connect

    Wilson, R.J.; Jones, B.G.; Roy, R.P.

    1980-02-01

    An experimental study of the fluctuating velocity field, the fluctuating static wall pressure and the in-stream fluctuating static pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field; fluctuating static wall pressure and in-stream fluctuating static pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, the cross-correlation between the fluctuating static wall pressure and the fluctuating static pressure in the core region of the flow and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained.

  2. Novel Optical Technique Developed and Tested for Measuring Two-Point Velocity Correlations in Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory A.; Goldburg, Walter I.

    2002-01-01

    A novel technique for characterizing turbulent flows was developed and tested at the NASA Glenn Research Center. The work is being done in collaboration with the University of Pittsburgh, through a grant from the NASA Microgravity Fluid Physics Program. The technique we are using, Homodyne Correlation Spectroscopy (HCS), is a laser-light-scattering technique that measures the Doppler frequency shift of light scattered from microscopic particles in the fluid flow. Whereas Laser Doppler Velocimetry gives a local (single-point) measurement of the fluid velocity, the HCS technique measures correlations between fluid velocities at two separate points in the flow at the same instant of time. Velocity correlations in the flow field are of fundamental interest to turbulence researchers and are of practical importance in many engineering applications, such as aeronautics.

  3. Precision measurement of transverse velocity distribution of a strontium atomic beam

    NASA Astrophysics Data System (ADS)

    Gao, F.; Liu, H.; Xu, P.; Tian, X.; Wang, Y.; Ren, J.; Wu, Haibin; Chang, Hong

    2014-02-01

    We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of 88Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10) kHz.

  4. Velocity Field Measurements of Human Coughing Using Time Resolved Particle Image Velocimetry

    NASA Astrophysics Data System (ADS)

    Khan, T.; Marr, D. R.; Higuchi, H.; Glauser, M. N.

    2003-11-01

    Quantitative fluid mechanics analysis of human coughing has been carried out using new Time Resolved Particle Image Velocimetry (TRPIV). The study involves measurement of velocity vector time-histories and velocity profiles. It is focused on the average normal human coughing. Some work in the past on cough mechanics has involved measurement of flow rates, tidal volumes and sub-glottis pressure. However, data of unsteady velocity vector field of the exiting highly time-dependent jets is not available. In this study, human cough waveform data are first acquired in vivo using conventional respiratory instrumentation for various volunteers of different gender/age groups. The representative waveform is then reproduced with a coughing/breathing simulator (with or without a manikin) for TRPIV measurements and analysis. The results of this study would be useful not only for designing of indoor air quality and heating, ventilation and air conditioning systems, but also for devising means of protection against infectious diseases.

  5. Precision measurement of transverse velocity distribution of a strontium atomic beam

    SciTech Connect

    Gao, F.; Liu, H.; Tian, X.; Xu, P.; Wang, Y.; Ren, J.; Wu, Haibin; Chang, Hong

    2014-02-15

    We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of {sup 88}Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10) kHz.

  6. Simultaneous multiple-point velocity measurements using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C.; Hiller, B.; Hanson, R. K.

    1983-01-01

    A technique is demonstrated for measuring velocity at multiple locations in a plane of a gaseous flowfield using Doppler-shifted absorption with fluorescence detection from iodine molecules, excited by a sheet of tunable single-axial-mode argon-ion laser radiation at 514.5 nm. Measurements were made simultaneously at 10,000 points in an iodine-seeded supersonic flow field with a 100 x 100 element photodiode array camera and were found to agree well with a numerical solution for the velocity field. The accuracy with which a component of velocity can be measured is limited, in the current approach, by the iodine linewidth to about 5 m/sec.

  7. Sampling artifact in volume weighted velocity measurement. II. Detection in simulations and comparison with theoretical modeling

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Zhang, Pengjie; Jing, Yipeng

    2015-02-01

    Measuring the volume weighted velocity power spectrum suffers from a severe systematic error due to imperfect sampling of the velocity field from the inhomogeneous distribution of dark matter particles/halos in simulations or galaxies with velocity measurement. This "sampling artifact" depends on both the mean particle number density n¯P and the intrinsic large scale structure (LSS) fluctuation in the particle distribution. (1) We report robust detection of this sampling artifact in N -body simulations. It causes ˜12 % underestimation of the velocity power spectrum at k =0.1 h /Mpc for samples with n¯ P=6 ×10-3 (Mpc /h )-3 . This systematic underestimation increases with decreasing n¯P and increasing k . Its dependence on the intrinsic LSS fluctuations is also robustly detected. (2) All of these findings are expected based upon our theoretical modeling in paper I [P. Zhang, Y. Zheng, and Y. Jing, Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling, arXiv:1405.7125.]. In particular, the leading order theoretical approximation agrees quantitatively well with the simulation result for n¯ P≳6 ×10-4 (Mpc /h )-3 . Furthermore, we provide an ansatz to take high order terms into account. It improves the model accuracy to ≲1 % at k ≲0.1 h /Mpc over 3 orders of magnitude in n¯P and over typical LSS clustering from z =0 to z =2 . (3) The sampling artifact is determined by the deflection D field, which is straightforwardly available in both simulations and data of galaxy velocity. Hence the sampling artifact in the velocity power spectrum measurement can be self-calibrated within our framework. By applying such self-calibration in simulations, it is promising to determine the real large scale velocity bias of 1013M⊙ halos with ˜1 % accuracy, and that of lower mass halos with better accuracy. (4) In contrast to suppressing the velocity power spectrum at large scale, the sampling artifact causes an overestimation of the velocity

  8. Ultrasonic measurements of velocity for modulus assessment of a material using a delay line approach

    NASA Astrophysics Data System (ADS)

    Ko, R. T.; Chen, M. Y.; Hoppe, W. C.; Blackshire, J. L.

    2013-01-01

    In an effort to evaluate the modulus of materials at elevated temperatures, an ultrasonic delay line approach was developed. The setup was tested with a known material, an aluminum alloy, using delay lines at ambient temperature to examine the feasibility of this approach. Due to the low frequency used, interference occurred between multiple passes of the ultrasound through the material resulting a lower than expected measured velocity. Incorporation of a transmission coefficient in the model of the experiment corrected the expected timing of the ultrasonic signals, reconciling the model to measurements of velocity.

  9. The measurement of abrasive particles velocities in the process of abrasive water jet generation

    NASA Astrophysics Data System (ADS)

    Zeleňák, Michal; Foldyna, Josef; Říha, Zdeněk

    2014-08-01

    An optimization of the design of the abrasive cutting head using the numerical simulation requires gathering as much information about processes occurring in the cutting head as possible. Detailed knowledge of velocities of abrasive particles in the process of abrasive water jet generation is vital for the verification of the numerical model. A method of measurement of abrasive particles at the exit of focusing tube using the FPIV technique was proposed and preliminary tests are described in the paper. Results of analysis of measured velocity fields are presented in the paper.

  10. Ultrafast fiber grating sensor systems for velocity, position, pressure, and temperature measurements

    NASA Astrophysics Data System (ADS)

    Udd, Eric; Udd, Ingrid; Benterou, Jerry J.; Rodriguez, George

    2016-05-01

    In 2006 an approach was developed that used chirped fiber gratings in combination with a high speed read out configuration to measure the velocity and position of shock waves after detonation of energetic materials. The first demonstrations were conducted in 2007. Extensions of this technology were made to measure pressure and temperature as well as velocity and position during burn, deflagration and detonation. This paper reviews a series of improvements that have been made by Columbia Gorge Research, LLC, Lawrence Livermore National Lab and Los Alamos National Lab in developing and improving this technology.

  11. Solar luminosity oscillations from two stations and correlation with velocity measurements

    NASA Astrophysics Data System (ADS)

    Jimenez, A.; Palle, Pere L.; Roca Cortés, Teodoro; Andersen, N. B.; Domingo, V.; Jones, A. R.; Alvarez, M.; Ledezma, E.

    1988-12-01

    Since 1984 the measurements of a quadruple photometer sited at the Observatorio del Teide (Izana, Tenerife) made it possible to identify the p-mode luminosity spectrum with simultaneous velocity observations. Comparing this data, the adiabatic behavior of solar atmosphere and theoretical expectations from solar models were tested. In order to increase the signal-to-noise ratio and reduce the sidebands due to the night-time data gaps, a second identical photometer was set-up in December 1987, at the Observatorio de San Pedro Martir (Baja California Norte, Mexico). Results of the observations of these two stations are analyzed and compared with simultaneous velocity measurements.

  12. Ultrasonic velocity measurement using phase-slope cross-correlation methods

    NASA Technical Reports Server (NTRS)

    Hull, D. R.; Kautz, H. E.; Vary, A.

    1984-01-01

    Computer implemented phase-slope and cross-correlation methods are introduced for measuring time delays between pairs of broadband ultrasonic pulse-echo signals for determining velocity in engineering materials. The phase-slope and cross-correlation methods are compared with the overlap method which is currently in wide use. Comparison of digital versions of the three methods shows similar results for most materials having low ultrasonic attenuation. However, the cross-correlation method is preferred for highly attenuating materials. An analytical basis for the cross-correlation method is presented. Examples are given for the three methods investigated to measure velocity in representative materials in the megahertz range.

  13. Phase-resolved measurements of ion velocity in a radio-frequency sheath.

    PubMed

    Jacobs, Brett; Gekelman, Walter; Pribyl, Pat; Barnes, Michael

    2010-08-13

    The time-dependent argon-ion velocity distribution function above and within the plasma sheath of an rf-biased substrate has been measured using laser-induced fluorescence in a commercial plasma processing tool. Discharge parameters were such that the 2.2 MHz rf-bias period was on the order of the ion transit time through the sheath (τ{ion}/τ{rf}=0.3). This work embodies the first time-resolved measurement of ion velocity distribution functions within an rf-biased sheath over a large area (30 cm diameter) silicon wafer substrate.

  14. An industrial light-field camera applied for 3D velocity measurements in a slot jet

    NASA Astrophysics Data System (ADS)

    Seredkin, A. V.; Shestakov, M. V.; Tokarev, M. P.

    2016-10-01

    Modern light-field cameras have found their application in different areas like photography, surveillance and quality control in industry. A number of studies have been reported relatively low spatial resolution of 3D profiles of registered objects along the optical axis of the camera. This article describes a method for 3D velocity measurements in fluid flows using an industrial light-field camera and an alternative reconstruction algorithm based on a statistical approach. This method is more accurate than triangulation when applied for tracking small registered objects like tracer particles in images. The technique was used to measure 3D velocity fields in a turbulent slot jet.

  15. Measuring preheat in laser-drive aluminum using velocity interferometer system for any reflector: Experiment

    SciTech Connect

    Shu, Hua; Fu, Sizu; Huang, Xiuguang; Wu, Jiang; Xie, Zhiyong; Zhang, Fan; Ye, Junjian; Jia, Guo; Zhou, Huazhen

    2014-08-15

    In this paper, we systematically study preheating in laser-direct-drive shocks by using a velocity interferometer system for any reflector (VISAR). Using the VISAR, we measured free surface velocity histories of Al samples over time, 10–70 μm thick, driven directly by a laser at different frequencies (2ω, 3ω). Analyzing our experimental results, we concluded that the dominant preheating source was X-ray radiation. We also discussed how preheating affected the material initial density and the measurement of Hugoniot data for high-Z materials (such as Au) using impedance matching. To reduce preheating, we proposed and tested three kinds of targets.

  16. Application of IR imaging for free-surface velocity measurement in liquid-metal systems

    DOE PAGES

    Hvasta, M. G.; Kolemen, E.; Fisher, A.

    2017-01-05

    Measuring free-surface, liquid-metal flow velocity is challenging to do in a reliable and accurate manner. This paper presents a non-invasive, easily calibrated method of measuring the surface velocities of open-channel liquid-metal flows using an IR camera. Unlike other spatially limited methods, this IR camera particle tracking technique provides full field-of-view data that can be used to better understand open-channel flows and determine surface boundary conditions. Lastly, this method could be implemented and automated for a wide range of liquid-metal experiments, even if they operate at high-temperatures or within strong magnetic fields.

  17. Exploitation of SAR data for measurement of ocean currents and wave velocities

    NASA Technical Reports Server (NTRS)

    Shuchman, R. A.; Lyzenga, D. R.; Klooster, A., Jr.

    1981-01-01

    Methods of extracting information on ocean currents and wave orbital velocities from SAR data by an analysis of the Doppler frequency content of the data are discussed. The theory and data analysis methods are discussed, and results are presented for both aircraft and satellite (SEASAT) data sets. A method of measuring the phase velocity of a gravity wave field is also described. This method uses the shift in position of the wave crests on two images generated from the same data set using two separate Doppler bands. Results of the current measurements are pesented for 11 aircraft data sets and 4 SEASAT data sets.

  18. Radial velocity discriminated coronal photometric measurements at the July 11, 1991 total eclipse

    NASA Astrophysics Data System (ADS)

    Beavers, Willet I.; Eitter, Joseph J.

    2009-03-01

    The results from a set of 12 solar corona radial velocity measurements in the 400-440 nm spectral band during the total solar eclipse of July 11, 1991 are reported. The measurements show that the orbital motion of the F-corona material near the sun in the ecliptic plane is consistent with Keplerian motion and predominantly, but not exclusively, prograde, as is usually assumed. This work demonstrates a method of using the measured radial velocities to sort out the relative amounts of K-corona, near-earth F-corona, near-solar F-corona, and scattered light in each measurement for each observation point W and E of the sun between 2.5 Ro(solar radii) and 5 Ro along the celestial equator and at three points north of the sun. The near-solar F-corona component is quite weak, contributing only 7-14% of the total signal in each case. The stronger diffraction component from near-earth F-corona is estimated to have been produced by particles with radii of about 11μ. In contrast, the scattered light component appears as strong zero-velocity features dominating all the measurements. The measurements W and E of the sun and near the ecliptic plane also show evidence of a red-shift velocity of at least 330 km s -1, suggestive of a high-speed dust outflow from the sun.

  19. Full-depth englacial vertical ice sheet velocities measured using phase-sensitive radar

    NASA Astrophysics Data System (ADS)

    Kingslake, Jonathan; Hindmarsh, Richard C. A.; Adalgeirsdóttir, Gusfinna; Conway, Howard; Corr, Hugh F. J.; Gillet-Chaulet, Fabien; Martín, Carlos; King, Edward C.; Mulvaney, Robert; Pritchard, Hamish D.

    2014-12-01

    We describe a geophysical technique to measure englacial vertical velocities through to the beds of ice sheets without the need for borehole drilling. Using a ground-based phase-sensitive radio echo sounder (pRES) during seven Antarctic field seasons, we measure the temporal changes in the position of englacial reflectors within ice divides up to 900 m thick on Berkner Island, Roosevelt Island, Fletcher Promontory, and Adelaide Island. Recorded changes in reflector positions yield "full-depth" profiles of vertical ice velocity that we use to examine spatial variations in ice flow near the divides. We interpret these variations by comparing them to the results of a full-Stokes simulation of ice divide flow, qualitatively validating the model and demonstrating that we are directly detecting an ice-dynamical phenomenon called the Raymond Effect. Using pRES, englacial vertical ice velocities can be measured in higher spatial resolution than is possible using instruments installed within the ice. We discuss how these measurements could be used with inverse methods to measure ice rheology and to improve ice core dating by incorporating pRES-measured vertical velocities into age modeling.

  20. The Effect of Periosteal Resection on Tibial Growth Velocity Measured by Microtransducer Technology in Lambs

    PubMed Central

    Sansone, Jason M.; Wilsman, Norman J.; Leiferman, Ellen M.; Noonan, Kenneth J.

    2010-01-01

    Background Disruption of the periosteum, whether traumatic or elective, has long been known to accelerate growth in the developing skeleton. However, the extent, timing, and mechanism of the resultant increase in growth velocity (if any) remain undefined. The primary research questions were: Does periosteal resection result in a change (increase) in growth velocity of a long bone at the growth plate? When after the resection does the effect start and for how long? Finally, which of several cellular mechanisms is most likely responsible for the change in growth velocity. Methods Five lambs underwent proximal tibial growth plate periosteal resection with subsequent measurement of growth velocity by implantable microtransducers or fluorochrome labeling. This former technique provided real-time growth velocity data with a resolution of about 10µm (width of a proliferative zone chondrocyte). These measurements were accurate at up to four weeks postoperative, as verified by fluorochrome labeling, and radiographic measurement. Two lambs were continued on the study for an additional three weeks. Histomorphometric and stereological assessment of chondrocytic kinetic parameters was performed on control and experimental tibiae following euthanasia. Results Periosteal resection increased growth velocity in every lamb, at every time point, and in a consistent and sustained manner. Histomorphometric correlation to this phenomenon indicated that the cellular basis of this acceleration was most likely the result of hypertrophic chondrocyte axial elongation, rather than changes in chondrocyte proliferation, magnitude of hypertrophic chondrocytic swelling, or increased matrix production. Conclusions Periosteal resection creates immediate and sustained acceleration of growth resulting from axial elongation of the hypertrophic chondrocyte. While the increase in growth velocity was consistent, the absolute magnitude of the acceleration suggests that periosteal resection be considered

  1. Application of dual-focus fluorescence correlation spectroscopy to microfluidic flow-velocity measurement.

    PubMed

    Arbour, Tyler J; Enderlein, Jörg

    2010-05-21

    Several methods exist to measure and map fluid velocities in microfluidic devices, which are vital to understanding properties on the micro- and nano-scale. Fluorescence correlation spectroscopy (FCS) is a method traditionally exploited for its ability to measure molecular diffusion coefficients. However, several reports during the past decade have shown that FCS can also be successfully used to measure precise flow rates in microfluidics with very high spatial resolution, making it a competitive alternative to other common flow-measurement methods. In 2007 we introduced a modified version of conventional FCS that overcomes many of the artifacts troubling the standard technique. Here we show how the advantages of this method, called dual-focus FCS, extend to flow measurements. To do so, we have measured the velocity flow profile along the cross-section of a square-bore microfluidic channel and compared the result to the theoretical prediction.

  2. Measuring melt and velocity of Alaskan mountain glaciers using phase-sensitive radar and differential GPS

    NASA Astrophysics Data System (ADS)

    Neuhaus, S.; Tulaczyk, S. M.

    2015-12-01

    Alaskan glaciers show some of the highest rates of retreat worldwide, contributing to sea level rise. This retreat is due to both increased velocity and increased melt. We seek to understand the role of glacial meltwater on velocity. Matanuska glacier, a land terminating glacier in Alaska, has been well-studied using traditional glaciological techniques, but new technology has emerged that allows us to measure melt and velocity more accurately. We employed high-resolution differential GPS to create surface velocity profiles across flow in the ablation zone during the summer of 2015. We also measured surface ablation using stakes and measured basal melt using phase-sensitive radar designed by the British Antarctic Survey. The positions acquired by differential GPS are obtained to a resolution of less than 0.5m, while feature tracking using time-lapse photography for the same time period yields positions with greater and more variable uncertainty. The phase-sensitive radar provides ice thinning rates. Phase-sensitive radar together with ground penetrating radar provides us with an understanding of the internal structure of the glacier. This suite of data allows us to determine the relative importance of surface melt, basal melt, and internal deformation on ice velocity in warm mountain glaciers.

  3. Image correlation algorithm for measuring lymphocyte velocity and diameter changes in contracting microlymphatics.

    PubMed

    Dixon, J Brandon; Gashev, Anatoliy A; Zawieja, David C; Moore, James E; Coté, Gerard L

    2007-03-01

    Efforts have recently been made to estimate wall shear stress throughout the contractile cycle of mesenteric rat lymphatics with a high speed video microscopy system. This was prompted by reports in the literature that lymphatic pumping is related to wall shear stress. While one can estimate wall shear stress by tracking lymphocyte velocity, it is prohibitively tedious to manually track particles over a reasonable time frame for a good number of experiments. To overcome this, an image correlation method similar to digital particle imaging velocimetry was developed and tested on contracting lymphatics to measure both vessel diameter and fluid velocity. The program tracked temporal fluctuations in spatially averaged velocity with a standard error of prediction of 0.4 mm/s. From these studies we have measured velocities ranging from -2 to 4 mm/s. Diameter changes were also measured with a standard error of 7 microm. These algorithms and techniques could be beneficial for investigating various changes in contractile behavior as a function of changes in velocity and wall shear stress.

  4. Measurement of a velocity field in microvessels using a high resolution PIV technique.

    PubMed

    Sugii, Yasuhiko; Nishio, Shigeru; Okamoto, Koji

    2002-10-01

    Because endothelial cells are subject to flow shear stress, it is important to determine the velocity distribution in microvessels during studies of the mechanical interactions between the blood and the endothelium. Particle image velocimetry (PIV) is a quantitative method for measuring velocity fields instantaneously in experimental fluid mechanics. The authors have developed a high-resolution PIV technique that improves the dynamic flow range, spatial resolution, and measurement accuracy. The proposed method was applied to images of the arteriole in the rat mesentery, using an intravital microscope and high-speed digital video system. Taking the mesentery motion into account, the PIV technique was improved to measure red blood cell (RBC) velocity. Velocity distributions with spatial resolutions of 0.8 3 0.8 mm were obtained even near the wall in the center plane of the arteriole. The arteriole velocity profile was blunt in the center region of the vessel cross-section and sharp in the near-wall region. Typical flow features for non-Newtonian fluid are shown.

  5. Turbulent velocity and concentration measurements in a macro-scale multi-inlet vortex nanoprecipitation reactor

    NASA Astrophysics Data System (ADS)

    Liu, Zhenping; Fox, Rodney; Hill, James; Olsen, Michael

    2013-11-01

    Flash Nanoprecipitation (FNP) is a technique to produce monodisperse functional nanoparticles. Microscale multi-inlet vortex reactors (MIVR) have been effectively applied to FNP due to their ability to provide rapid mixing and flexibility of inlet flow conditions. A scaled-up MIVR could potentially generate large quantities of functional nanoparticles, giving FNP wider applicability in industry. In the presented research, the turbulent velocity field inside a scaled-up, macroscale MIVR is measured by particle image velocimetry (PIV). Within the reactor, velocity is measured using both two-dimensional and stereoscopic PIV at two Reynolds numbers (3500 and 8750) based on the flow at each inlet. Data have been collected at numerous locations in the inlet channels, the reaction chamber, and the reactor outlet. Mean velocity and Reynolds stresses have been obtained based on 5000 instantaneous velocity realizations at each measurement location. The turbulent mixing process has also been investigated with passive scalar planar laser-induced fluorescence and simultaneous PIV/PLIF. Velocity and concentration results are compared to results from previous experiments in a microscale MIVR. Scaled profiles of turbulent quantities are similar to those previously found in the microscale MIVR.

  6. Laser-optic Measurements of Velocity of Particles in the Powder Stream at Coaxial Laser Cladding

    NASA Astrophysics Data System (ADS)

    Sergachev, D. V.; Mikhal'chenko, A. A.; Kovalev, O. B.; Kuz'min, V. I.; Grachev, G. N.; Pinaev, P. A.

    The problems of particle velocity and temperature measurement can be solved with commonly-known methods of registration based on spectrometry and a complex of laser and optical means. The diagnostic technique combines two independent methods of particle velocity measurement, namely the passive way which is based on the intrinsic radiation of the heated particles in a gas flow, and the active one which utilizes the effect of the laser beam scattering. It is demonstrated that the laser radiation can affect significantly the particles velocity at the laser cladding. Presented bar charts of statistical distributions of the particles velocities illustrate two modes of the coaxial nozzle performance, with and without СО2-laser radiation. Different types of powders (Al2O3, Mo, Ni, Al) were used in tests, the particle size distributions were typical for the laser cladding; air, nitrogen, argon were used as working gases, continuous radiation of the СО2 laser reached 3 kW. It is shown that in the laser-radiation field, the powder particles undergo extra acceleration due to the laser evaporation and reactive force occurrence resulting from the recoil pressure vapors from the beamed part of particles' surfaces. The observed effect of particles acceleration depends on the particles concentration in the powder flow. Due to the laser acceleration, the velocities of individual particles may reach the values of about 80 - 100 m/s. The trichromatic pyrometry method was utilized to measure the particles temperature in the powder flow.

  7. Velocity Measurements of Free Surface Liquid Metal Flows in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Pfeffer, Scott; Ji, Hantao; Nornberg, Mark; Rhoads, John

    2008-11-01

    A potential probe diagnostic was developed and calibrated to map the velocity profile of free-surface liquid metal channel flow and quantify the effect an applied magnetic field played in shaping the velocity profile. The setup for this experiment consists of a wide aspect ratio channel sealed from the air, with argon replacing the air in the channel, placed within an electromagnet capable of producing more than a 2000 Gauss field perpendicular to the flow. An alloy of GaInSn, which is liquid at room temperature, is pumped through the channel by a screw pump at a specified rate. The velocity profile is obtained by measuring the voltage across pairs of probes. Various materials were used to determine which probe material would maximize the signal from the voltage induced by the Hall effect and reduce the voltage due to thermoelectric effects. Extensive calibration was then carried out to ensure an accurate velocity measurement. After amplification and filtering this signal gives us a good measurement of the velocity of the liquid metal over the cross-section of a specific probe.

  8. Measurements of neutral and ion velocity distribution functions in a Hall thruster

    NASA Astrophysics Data System (ADS)

    Svarnas, Panagiotis; Romadanov, Iavn; Diallo, Ahmed; Raitses, Yevgeny

    2015-11-01

    Hall thruster is a plasma device for space propulsion. It utilizes a cross-field discharge to generate a partially ionized weakly collisional plasma with magnetized electrons and non-magnetized ions. The ions are accelerated by the electric field to produce the thrust. There is a relatively large number of studies devoted to characterization of accelerated ions, including measurements of ion velocity distribution function using laser-induced fluorescence diagnostic. Interactions of these accelerated ions with neutral atoms in the thruster and the thruster plume is a subject of on-going studies, which require combined monitoring of ion and neutral velocity distributions. Herein, laser-induced fluorescence technique has been employed to study neutral and single-charged ion velocity distribution functions in a 200 W cylindrical Hall thruster operating with xenon propellant. An optical system is installed in the vacuum chamber enabling spatially resolved axial velocity measurements. The fluorescence signals are well separated from the plasma background emission by modulating the laser beam and using lock-in detectors. Measured velocity distribution functions of neutral atoms and ions at different operating parameters of the thruster are reported and analyzed. This work was supported by DOE contract DE-AC02-09CH11466.

  9. Measurements of the anisotropy of ultrasonic velocity in freshly excised and formalin-fixed myocardial tissue

    NASA Astrophysics Data System (ADS)

    Baldwin, Steven L.; Yang, Min; Marutyan, Karen R.; Wallace, Kirk D.; Holland, Mark R.; Miller, James G.

    2005-07-01

    The objective of this study was to quantify the anisotropy of ultrasonic velocity in freshly excised myocardial tissue and to examine the effects of formalin-fixation. Through-transmission radio-frequency-based measurements were performed on ovine and bovine myocardial specimens from 24 different hearts. A total of 81 specimens were obtained from specific locations within each heart to investigate the possibility of regional differences in anisotropy of velocity in the left ventricular wall and septum. No regional differences were observed for either lamb or cow myocardial specimens. In addition, no specific species-dependent differences were observed between ovine and bovine myocardium. Average values of velocity at room temperature for perpendicular and parallel insonification were 1556.9+/-0.6 and 1565.2+/-0.7 m/s (mean+/-standard error), respectively, for bovine myocardium (N=45) and 1556.3+/-0.6 and 1564.7+/-0.7 m/s for ovine myocardium (N=36). Immediately after measurements of freshly excised myocardium, ovine specimens were fixed in formalin for at least one month and then measurements were repeated. Formalin-fixation appears to increase the overall velocity at all angles of insonification and to increase the magnitude of anisotropy of velocity.

  10. 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.

  11. 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.

  12. In-Situ Continuous Detonation Velocity Measurements Using Fiber-optic Bragg Grating Sensors

    SciTech Connect

    Benterou, J; Udd, E; Wilkins, P; Roeske, F; Roos, E; Jackson, D

    2007-07-25

    In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation and detonation research requires continuous measurement of low order detonation velocities as the detonation runs up to full order detonation for a given density and initiation pressure pulse. A novel detector of detonation velocity is presented using a 125 micron diameter optical fiber with an integral chirped fiber Bragg grating as an intrinsic sensor. This fiber is embedded in the explosive under study and interrogated during detonation as the fiber Bragg grating scatters light back along the fiber to a photodiode, producing a return signal dependant on the convolution integral of the grating reflection bandpass, the ASE intensity profile and the photodetector response curve. Detonation velocity is measured as the decrease in reflected light exiting the fiber as the grating is consumed when the detonation reaction zone proceeds along the fiber sensor axis. This small fiber probe causes minimal perturbation to the detonation wave and can measure detonation velocities along path lengths tens of millimeters long. Experimental details of the associated equipment and preliminary data in the form of continuous detonation velocity records within nitromethane and PBX-9502 are presented.

  13. Comprehensive spatiotemporal glacier and ice sheet velocity measurements from Landsat 8

    NASA Astrophysics Data System (ADS)

    Moon, Twila; Fahnestock, Mark; Scambos, Ted; Klinger, Marin; Haran, Terry

    2015-04-01

    Combining newly developed software with Landsat 8 image returns, we are now producing broad-coverage ice velocity measurements on weekly to monthly scales across ice sheets and glaciers. Using new image-to-image cross correlation software, named PyCorr, we take advantage of the improved radiometric resolution of the Landsat 8 panchromatic band to create velocity maps with sub-pixel accuracy. Landsat 8's 12-bit radiometric resolution supports measurement of ice flow in uncrevassed regions based on persistent sastrugi patterns lasting weeks to a few months. We also leverage these improvements to allow for ice sheet surface roughness measurements. Landsat 8's 16-day repeat orbit and increased image acquisition across the Greenland and Antarctic ice sheets supports development of seasonal to annual ice sheet velocity mosaics with full coverage of coastal regions. We also create time series for examining sub-seasonal change with near real time processing in areas such as the Amundsen Sea Embayment and fast flowing Greenland outlet glaciers. In addition, excellent geolocation accuracy enables velocity mapping of smaller ice caps and glaciers, which we have already applied in Alaska and Patagonia. Finally, PyCorr can be used for velocity mapping with other remote sensing imagery, including high resolution WorldView satellite data.

  14. The in situ permeable flow sensor: A device for measuring groundwater flow velocity

    SciTech Connect

    Ballard, S.; Barker, G.T.; Nichols, R.L.

    1994-03-01

    A new technology called the In Situ Permeable Flow Sensor has been developed at Sandia National Laboratories. These sensors use a thermal perturbation technique to directly measure the direction and magnitude of the full three dimensional groundwater flow velocity vector in unconsolidated, saturated, porous media. The velocity measured is an average value characteristic of an approximately 1 cubic meter volume of the subsurface. During a test at the Savannah River Site in South Carolina, two flow sensors were deployed in a confined aquifer in close proximity to a well which was screened over the entire vertical extent of the aquifer and the well was pumped at four different pumping rates. In this situation horizontal flow which is radially directed toward the pumping well is expected. The flow sensors measured horizontal flow which was directed toward the pumping well, within the uncertainty in the measurements. The observed magnitude of the horizontal component of the flow velocity increased linearly with pumping rate, as predicted by theoretical considerations. The measured horizontal component of the flow velocity differed from the predicted flow velocity, which was calculated with the assumptions that the hydraulic properties of the aquifer were radially homogeneous and isotropic, by less than a factor of two. Drawdown data obtained from other wells near the pumping well during the pump test indicate that the hydraulic properties of the aquifer are probably not radially homogeneous but the effect of the inhomogeneity on the flow velocity field around the pumping well was not modeled because the degree and distribution of the inhomogeneity are unknown. Grain size analysis of core samples from wells in the area were used to estimate the vertical distribution of hydraulic conductivity.

  15. On the Measurement of the Velocity of Light Emitted by an Ultrarelativistic Source

    NASA Astrophysics Data System (ADS)

    Kupryaev, N. V.

    2015-01-01

    By analytical calculations it has been shown that in papers on the measurement of the velocity of light published in 2011 in the journals Uspekhi Fizicheskikh Nauk [Physics-Uspekhi] and Pis'ma v ZhETF [JRTP Letters], in actual fact the velocity of a light pulse from a relativistic clot of electrons was not measured. All that was done was to compare the velocity of light emitted by an ultrarelativistic source with the velocity of light from a fixed source, i.e., both in the first and second variants (one independent quantity was compared with another), in essence, it was simply postulated. In the first variant a glass plate was used as the fixed light source, and in the second variants, a synchrotron pulse was used as the reference signal. The velocity of light was calculated using a calculated time based on the postulate of the special theory of relativity (STR) on the invariance of the velocity of light. This, of course, contradicts the Newton-Ritz hypothesis on ballistic addition of velocities, but at the present time this idea is not taken seriously. Practically none of the serious contemporary critics of STR, apart, of course, from amateurs, holds this point of view. The result cannot be considered as a direct experimental confirmation of the second postulate of Einstein's special theory of relativity, i.e., its main part, which speaks of the constancy of the velocity of light in all inertial reference frames, but only of that part which speaks of the independence of the velocity of light on motion of the source. Moreover, this same result stands as equal proof of the so-called theory of the luminiferous ether, which held sway up to the creation of the special theory of relativity and which has now been revived, i.e., it does not distinguish between these two theories. It is fundamentally impossible in principle to measure the velocity of light by the proposed method, it is only possible to postulate it.

  16. Using motionally-induced electric signals to indirectly measure ocean velocity: Instrumental and theoretical developments

    NASA Astrophysics Data System (ADS)

    Szuts, Zoltan B.

    2012-04-01

    The motion of conductive sea water through the earth’s magnetic field generates electromagnetic (EM) fields through a process called motional induction. Direct measurements of oceanic electric fields can be easily converted to water velocities by application of a first order theory. This technique has been shown to obtain high quality velocities through instrumental advances and an accumulation of experience during the past decades. EM instruments have unique operational considerations and observe, for instance, vertically-averaged horizontal velocity (from stationary sensors) or vertical profiles of horizontal velocity (from expendable probes or autonomous profiling floats). The first order theory describes the dominant electromagnetic response, in which vertically-averaged and vertically-varying horizontal velocities are proportional to electric fields and electric currents, respectively. After discussions of the first order theory and deployment practices, operational capabilities are shown through recently published projects that describe stream-coordinate velocity structure of the Antarctic Circumpolar Current, quickly-evolving overflow events in the Denmark Strait, and time-development of momentum input into the ocean from a hurricane. A detailed analysis of the Gulf Stream at its separation point from the continental slope serves as a case study for interpreting EM measurements, including the incorporation of geophysical knowledge of the sediment. In addition, the first order approximation is tested by the many features at this location that contradict the approximation’s underlying assumptions: sharp horizontal velocity gradients, steep topography, and thick and inhomogeneous sediments. Numerical modeling of this location shows that the first order assumption is accurate to a few percent (a few cm s-1) in almost all cases. The errors in depth-varying velocity are <3% (1-3 cm s-1), are substantiated by the direct observations, and can be corrected by

  17. Velocity Mapping Toolbox (VMT): a processing and visualization suite for moving-vessel ADCP measurements

    NASA Astrophysics Data System (ADS)

    Jackson, R.; Parsons, D. R.; Czuba, J. A.; Mueller, D. S.; Rhoads, B. L.; Engel, F.; Oberg, K. A.; Best, J. L.; Johnson, K. K.; Riley, J. D.

    2011-12-01

    In addition to their common application to measurement of discharge in rivers, acoustic Doppler current profilers (ADCP) provide valuable hydrodynamic data required for understanding geomorphic and fluvial processes. The increasing use of ADCPs to explore the characteristics of complex natural flows has led to a need for standardized post-processing methods for managing, analyzing, and displaying three-dimensional velocity data. Thus far, no standard analytical technique exists for averaging velocity data from multiple ADCP transects to produce a composite depiction of three-dimensional velocity fields. A new software tool, the Velocity Mapping Toolbox (VMT), is presented herein to address this important need. VMT is a Matlab-based toolbox for processing, analyzing, and displaying velocity data collected along multiple ADCP transects. The software can be used to explore patterns of three-dimensional fluid motion through several methods for calculation of secondary flows and includes capabilities for analyzing the acoustic backscatter and bathymetric data from the ADCP. A user-friendly graphical user interface (GUI) enhances program functionality and provides ready access to two- and three- dimensional plotting functions, allowing rapid display and interrogation of velocity, backscatter, and bathymetry data. This presentation describes the basic processing methods employed by VMT and highlights the capabilities of the toolbox through some example applications.

  18. Gas transfer velocities measured at low wind speed over a lake

    USGS Publications Warehouse

    Crusius, J.; Wanninkhof, R.

    2003-01-01

    The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1-min-averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10-m height, U10: (1) a bilinear dependence with a break in the slope at ???3.7 m s-1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 3.7 m s-1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ???3.7 m s-1 are virtually identical to the theoretical predictions for transfer across a smooth surface.

  19. Development of new measuring technique using sound velocity for CO2 concentration in Cameroonian volcanic lakes

    NASA Astrophysics Data System (ADS)

    Sanemasa, M.; Saiki, K.; Kaneko, K.; Ohba, T.; Kusakabe, M.; Tanyileke, G.; Hell, J.

    2012-12-01

    1. Introduction Limnic eruptions at Lakes Monoun and Nyos in Cameroon, which are sudden degassing of magmatic CO2 dissolved in the lake water, occurred in 1984 and 1986, respectively. The disasters killed about 1800 people around the lakes. Because of ongoing CO2 accumulation in the bottom water of the lakes, tragedy of limnic eruptions will possibly occur again. To prevent from further disasters, artificial degassing of CO2 from the lake waters has been undergoing. Additionally, CO2 monitoring of the lake waters is needed. Nevertheless, CO2 measurement is done only once or twice a year because current methods of CO2 measurement, which require chemical analysis of water samples, are not suitable for frequent measurement. In engineering field, on the other hand, a method to measure salt concentration using sound velocity has been proposed (Kleis and Sanchez, 1990). This method allows us to evaluate solute concentration fast. We applied the method to dissolved CO2 and examined the correlation between sound velocity and CO2 concentration in laboratory experiment. Furthermore, using the obtained correlation, we tried to estimate the CO2 concentration of waters in the Cameroonian lakes. 2. Laboratory experiment We examined the correlation between sound velocity and CO2 concentration. A profiler (Minos X, made by AML oceanography) and pure water were packed in cylindrical stainless vessel and high-pressure CO2 gas was injected to produce carbonated water. The profiler recorded temperature, pressure and sound velocity. Change of sound velocity was defined as difference of sound velocity between carbonated water and pure water under the same temperature and pressure conditions. CO2 concentration was calculated by Henry's law. The result indicated that the change of sound velocity [m s-1] is proportional to CO2 concentration [mmol kg-1], and the coefficient is 0.021 [m kg s-1 mmol-1]. 3. Field application Depth profiles of sound velocity, pressure, and temperature of Lakes

  20. Measurement of sound velocities of laser-shocked iron at pressures up to 800 GPa

    NASA Astrophysics Data System (ADS)

    Sakaiya, T.; Takahashi, H.; Kondo, T.; Shigemori, K.; Kadono, T.; Hironaka, Y.; Osaki, N.; Irifune, T.

    2011-12-01

    When we consider the structure of the Earth's interior, the sound velocity is one of the important physical properties of the interior materials because it can be directly compared with the seismological data which can yield the physical properties of the Earth's interior. Although it needs to measure the sound velocity of the interior material under high pressure and temperature, the sound velocity measurement of the materials on the condition over 200 GPa and 4000 K, such as the Earth's core condition, is technically difficult in static compression technique (e.g. diamond anvil cell: DAC) [1-3]. Therefore, in such higher pressure and temperature, dynamic compression technique, such as gas gun, is used. Although some works about the sound velocity of pure iron have been done by gas gun [4-6], it is not enough to discuss about the Earth's core which consists mainly of iron. We performed laser-shock experiments of iron at GEKKO-XII Laser System HIPER irradiation facility in Institute of Laser Engineering, Osaka University (ILE) [7]. The laser-shock compression can generate pressures over 1TPa, which are much higher pressures than previous works by gas gun. The sound velocities of iron were measured by side-on radiography [6]. The laser-irradiated target (Fe) is backlit with an x ray emitted from a high-Z foil (Ti) that is located along the side of the target and that is irradiated by a separate laser. The intensity distribution of the x ray transmitted through the target is imaged onto an x-ray streak camera. When the motion of the front surface and rear surface of the target is obtained from the radiograph, we can obtain the velocity of the shock and rarefaction wave. The rarefaction wave propagates the target with the sound velocity. The pressure generated by the laser-shock compression is obtained from the shock velocity and particle velocity of the target. The particle velocity is obtained from the time revolution of the front surface in the radiograph. In this

  1. An algorithm to estimate unsteady and quasi-steady pressure fields from velocity field measurements.

    PubMed

    Dabiri, John O; Bose, Sanjeeb; Gemmell, Brad J; Colin, Sean P; Costello, John H

    2014-02-01

    We describe and characterize a method for estimating the pressure field corresponding to velocity field measurements such as those obtained by using particle image velocimetry. The pressure gradient is estimated from a time series of velocity fields for unsteady calculations or from a single velocity field for quasi-steady calculations. The corresponding pressure field is determined based on median polling of several integration paths through the pressure gradient field in order to reduce the effect of measurement errors that accumulate along individual integration paths. Integration paths are restricted to the nodes of the measured velocity field, thereby eliminating the need for measurement interpolation during this step and significantly reducing the computational cost of the algorithm relative to previous approaches. The method is validated by using numerically simulated flow past a stationary, two-dimensional bluff body and a computational model of a three-dimensional, self-propelled anguilliform swimmer to study the effects of spatial and temporal resolution, domain size, signal-to-noise ratio and out-of-plane effects. Particle image velocimetry measurements of a freely swimming jellyfish medusa and a freely swimming lamprey are analyzed using the method to demonstrate the efficacy of the approach when applied to empirical data.

  2. Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight

    NASA Technical Reports Server (NTRS)

    Berry, John D.

    1997-01-01

    Drag caused by separated flow behind the hub of a helicopter has an adverse effect on aerodynamic performance of the aircraft. To determine the effect of separated flow on a configuration used extensively for helicopter aerodynamic investigations, an experiment was conducted using a laser velocimeter to measure velocities in the wake of a model helicopter hub operating at Mach-scaled conditions in forward flight. Velocity measurements were taken using a laser velocimeter with components in the vertical and downstream directions. Measurements were taken at 13 stations downstream from the rotor hub. At each station, measurements were taken in both a horizontal and vertical row of locations. These measurements were analyzed for harmonic content based on the rotor period of revolution. After accounting for these periodic velocities, the remaining unsteady velocities were treated as turbulence. Turbulence intensity distributions are presented. Average turbulent intensities ranged from approximately 2 percent of free stream to over 15 percent of free stream at specific locations and azimuths. The maximum average value of turbulence was located near the rear-facing region of the fuselage.

  3. Edge Ion Velocity Measurements with a Novel Doppler Spectrometer at the Alcator C-Mod Tokamak

    NASA Astrophysics Data System (ADS)

    Graf, Alexander; May, Mark; Beiersdorfer, Peter; Terry, Jim

    2006-10-01

    A high throughput, f/# ˜3.1, transmission grating Doppler spectrometer for visible light (3500-6700 å) is currently measuring ion or neutral velocities and temperatures at the Alcator C-Mod tokamak. The ion velocities are measured through the Doppler shift of impurities that are present in the plasma. A line width of as small as 0.4 å(velocity sensitivity of ˜10^5 cm/s) has been measured using calibration lamps. The spectrometer is fiber optically coupled and has access to toroidal and poloidal views. A spectral survey has been done with various views of the C-Mod plasma identifying various intrinsic impurities. The first Doppler measurements of B II were recorded with ˜15 ms per frame. Additional Doppler velocity and temperature measurements in both poloidal and toroidal directions for some of the brighter impurities (e.g. He II and N III), will be given. This work is supported was performed under the auspices of the DoE by UC LLNL under contract W-7405-ENG-48 and also under DoE Coop. Agreement DE-FC02-99ER54512.

  4. Relative position finite-time coordinated tracking control of spacecraft formation without velocity measurements.

    PubMed

    Hu, Qinglei; Zhang, Jian

    2015-01-01

    This paper investigates finite-time relative position coordinated tracking problem by output feedback for spacecraft formation flying without velocity measurement. By employing homogeneous system theory, a finite-time relative position coordinated tracking controller by state feedback is firstly developed, where the desired time-varying trajectory given in advance can be tracked by the formation. Then, to address the problem of lack of velocity measurements, a finite-time output feedback controller is proposed by involving a novel filter to recover unknown velocity information in a finite time. Rigorous proof shows that the proposed control law ensures global stability and guarantees the position of spacecraft formation to track a time-varying reference in finite time. Finally, simulation results are presented to illustrate the performance of the proposed controller.

  5. Two-phase velocity measurements around cylinders using particle image velocimetry

    SciTech Connect

    Hassan, Y.A.; Philip, O.G.; Schmidl, W.D.

    1995-09-01

    The particle Image Velocimetry flow measurement technique was used to study both single-phase flow and two-phase flow across a cylindrical rod inserted in a channel. First, a flow consisting of only a single-phase fluid was studied. The experiment consisted of running a laminar flow over four rods inserted in a channel. The water flow rate was 126 cm{sup 3}/s. Then a two-phase flow was studied. A mixture of water and small air bubbles was used. The water flow rate was 378 cm{sup 3}/s and the air flow rate was approximately 30 cm{sup 3}/s. The data are analyzed to obtain the velocity fields for both experiments. After interpretation of the velocity data, forces acting on a bubble entrained by the vortex were calculated successfully. The lift and drag coefficients were calculated using the velocity measurements and the force data.

  6. Rayleigh Scattering Diagnostic for Dynamic Measurement of Velocity Fluctuations in High Speed Jets

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, Jayanta; Elam, Kristie A.

    2001-01-01

    A flow diagnostic technique based on the molecular Rayleigh scattering of laser light is used to obtain dynamic density and velocity data in a high speed flow. The technique is based on analyzing the Rayleigh scattered light with a Fabry-Perot interferometer used in the static, imaging mode. An analysis is presented that established a lower bound for measurement uncertainty of about 20 m/sec for individual velocity measurements obtained in a 100 microsecond time interval. Software and hardware interfaces were developed to allow computer control of all aspects of the experiment and data acquisition. The signals from three photomultiplier tubes were simultaneously recorded using photon counting at a 10 kHz sampling rate and 10 second recording periods. Density and velocity data, including distribution functions and power spectra, taken in a Mach 0.8 free jet, are presented.

  7. Ultraviolet Molecular Rayleigh Scattering Used to Measure Velocity in High-Speed Flow

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.

    1997-01-01

    Molecular Rayleigh scattering offers a means to measure gas flow parameters including density, temperature, and velocity. No seeding of the flow is necessary. The Rayleigh scattered power is proportional to the gas density, the spectral width is related to the gas temperature, and the shift in the frequency of the spectral peak is proportional to one component of the fluid velocity. Velocity measurements based on Rayleigh scattering are more suitable for high-speed flow, where the bulk fluid velocity is on the order of, or larger than, the molecular thermal velocities. Use of ultraviolet wavelengths for Rayleigh scattering diagnostics is attractive for two reasons. First, the Rayleigh scattering cross section is proportional to the inverse 4th power of the wavelength. And second, the reflectivity of metallic surfaces is generally less than it is at longer wavelengths. This is of particular interest in confined flow situations, such as in small wind tunnels and aircraft engine components, where the stray laser light scattered from the windows and internal surfaces in the test facility limits the application of Rayleigh scattering diagnostics. In this work at the NASA Lewis Research Center, molecular Rayleigh scattering of the 266-nm fourth harmonic of a pulsed, injection seeded Nd:YAG (neodymium:yttriumaluminum- garnet) laser was used to measure velocity in a supersonic free air jet with a 9.3- mm exit diameter. The frequency of the Rayleigh scattered light was analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode, with the images recorded on a cooled, high-quantum-efficiency charge-coupled discharge (CCD) camera. In addition, some unshifted light from the same laser pulse was imaged through the interferometer to generate a reference. Data were obtained with single laser pulses at velocities up to Mach 1.3. The measured velocities were in good agreement with velocities calculated from isentropic flow relations. Our conclusion from

  8. New experimental technique for the measurement of the velocity field in thin films falling over obstacles

    NASA Astrophysics Data System (ADS)

    Landel, Julien R.; Daglis, Ana; McEvoy, Harry; Dalziel, Stuart B.

    2014-11-01

    We present a new experimental technique to measure the surface velocity of a thin falling film. Thin falling films are important in various processes such as cooling in heat exchangers or cleaning processes. For instance, in a household dishwasher cleaning depends on the ability of a thin draining film to remove material from a substrate. We are interested in the impact of obstacles attached to a substrate on the velocity field of a thin film flowing over them. Measuring the velocity field of thin falling films is a challenging experimental problem due to the small depth of the flow and the large velocity gradient across its depth. We propose a new technique based on PIV to measure the plane components of the velocity at the surface of the film over an arbitrarily large area and an arbitrarily large resolution, depending mostly on the image acquisition technique. We perform experiments with thin films of water flowing on a flat inclined surface, made of glass or stainless steel. The typical Reynolds number of the film is of the order of 100 to 1000, computed using the surface velocity, the film thickness and the kinematic viscosity of the film. We measure the modification to the flow field, from a viscous-gravity regime, caused by small solid obstacles, such as three-dimensional hemispherical obstacles and two-dimensional steps. We compare our results with past theoretical and numerical studies. This material is based upon work supported by the Defense Threat Reduction Agency under Contract No. HDTRA1-12-D-0003-0001.

  9. Bubble velocity, diameter, and void fraction measurements in a multiphase flow using fiber optic reflectometer

    NASA Astrophysics Data System (ADS)

    Lim, Ho-Joon; Chang, Kuang-An; Su, Chin B.; Chen, Chi-Yueh

    2008-12-01

    A fiber optic reflectometer (FOR) technique featuring a single fiber probe is investigated for its feasibility of measuring the bubble velocity, diameter, and void fraction in a multiphase flow. The method is based on the interference of the scattered signal from the bubble surface with the Fresnel reflection signal from the tip of the optical fiber. Void fraction is obtained with a high accuracy if an appropriate correction is applied to compensate the underestimated measurement value. Velocity information is accurately obtained from the reflected signals before the fiber tip touches the bubble surface so that several factors affecting the traditional dual-tip probes such as blinding, crawling, and drifting effects due to the interaction between the probe and bubbles can be prevented. The coherent signals reflected from both the front and rear ends of a bubble can provide velocity information. Deceleration of rising bubbles and particles due to the presence of the fiber probe is observed when they are very close to the fiber tip. With the residence time obtained, the bubble chord length can be determined by analyzing the coherent signal for velocity determination before the deceleration starts. The bubble diameters are directly obtained from analyzing the signals of the bubbles that contain velocity information. The chord lengths of these bubbles measured by FOR represent the bubble diameters when the bubble shape is spherical or represent the minor axes when the bubble shape is ellipsoidal. The velocity and size of bubbles obtained from the FOR measurements are compared with those obtained simultaneously using a high speed camera.

  10. Inertial Navigation System/Doppler Velocity Log (INS/DVL) Fusion with Partial DVL Measurements

    PubMed Central

    Tal, Asaf; Klein, Itzik; Katz, Reuven

    2017-01-01

    The Technion autonomous underwater vehicle (TAUV) is an ongoing project aiming to develop and produce a small AUV to carry on research missions, including payload dropping, and to demonstrate acoustic communication. Its navigation system is based on an inertial navigation system (INS) aided by a Doppler velocity log (DVL), magnetometer, and pressure sensor (PS). In many INSs, such as the one used in TAUV, only the velocity vector (provided by the DVL) can be used for aiding the INS, i.e., enabling only a loosely coupled integration approach. In cases of partial DVL measurements, such as failure to maintain bottom lock, the DVL cannot estimate the vehicle velocity. Thus, in partial DVL situations no velocity data can be integrated into the TAUV INS, and as a result its navigation solution will drift in time. To circumvent that problem, we propose a DVL-based vehicle velocity solution using the measured partial raw data of the DVL and additional information, thereby deriving an extended loosely coupled (ELC) approach. The implementation of the ELC approach requires only software modification. In addition, we present the TAUV six degrees of freedom (6DOF) simulation that includes all functional subsystems. Using this simulation, the proposed approach is evaluated and the benefit of using it is shown. PMID:28241410