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1

Laser Doppler flowmeter measures gas velocity  

Science.gov (United States)

Utilizing the large magnitudes of Doppler shifts obtainable from a CW gas laser, local velocity vectors are measured by using the visible light from the laser. This technique is applicable for the measurement of velocity of any moving surface.

Foreman, W.; Huffaker, R. M.

1966-01-01

2

Estimation of amputation level with a laser Doppler flowmeter.  

DEFF Research Database (Denmark)

Leg amputation levels were decided in 24 patients suffering from atherosclerosis, using the conventional techniques of segmental blood pressure and radioisotope skin clearance. The skin microcirculation was measured and recorded before operation with a laser doppler flowmeter. A high correlation was found between the successful amputation levels and the maximal blood perfusion of the skin measured in this way.

Gebuhr, Peter Henrik; JØrgensen, J P

1989-01-01

3

Doppler flowmeter  

Science.gov (United States)

A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

Karplus, Henry H. B. (Hinsdale, IL); Raptis, Apostolos C. (Downers Grove, IL)

1983-01-01

4

Routine clinical use of laser Doppler flowmeter to monitor free tissue transfer: preliminary results.  

Science.gov (United States)

Preliminary results indicate that a new laser Doppler flowmeter is more easily understood by nursing personnel than other laser Doppler units currently available. This monitor has demonstrated its capability in identifying and predicting tissue ischemia before clinically determined failure. Further evaluation of the device is warranted to define its use more clearly in the clinical setting. PMID:2958624

Jenkins, S D; Sepka, R S; Barwick, W J; Serafin, D; Klitzman, B

1987-07-01

5

Evaluation of cutaneous blood flow responses by 133Xe washout and a laser-Doppler flowmeter  

International Nuclear Information System (INIS)

A new method for noninvasive measurement of cutaneous blood flow is laser-Doppler flowmetry. The technique is based on the fact that laser light is back-scattered from the moving red blood cells, with Doppler-shifted frequencies; these impulses lead to photodetectors and are converted to flow signals. In this work we used a new system with a low noise level. Comparison was made between this technique and the atraumatic epicutaneous 133Xe technique for measurement of cutaneous blood flow during reactive hyperemia and orthostatic pressure changes. The laser-Doppler flowmeter seems to measure blood flow in capillaries as well as in arteriovenous anastomoses, while the 133Xe method probably measures only capillary flow. A calibration of the laser-Doppler method against the 133Xe method would appear to be impossible in skin areas where arteriovenous anastomoses are present. The changes in blood flow during reactive hyperemia, orthostatic pressure changes, and venous stasis were found to be parallel as measured by the two methods in skin areas without shunt vessels. The laser-Doppler flowmeter would appear to be a useful supplement to the 133Xe washout method in cutaneous vascular physiology, but it is important to keep in mind that different parameters may be measured

6

Evaluation of cutaneous blood flow responses by 133Xenon washout and a laser-Doppler flowmeter.  

Science.gov (United States)

A new method for noninvasive measurement of cutaneous blood flow is laser-Doppler flowmetry. The technique is based on the fact that laser light is back-scattered from the moving red blood cells, with Doppler-shifted frequencies; these impulses lead to photodetectors and are converted to flow signals. In this work we used a new system with a low noise level. Comparison was made between this technique and the atraumatic epicutaneous 133Xenon technique for measurement of cutaneous blood flow during reactive hyperemia and orthostatic pressure changes. The laser-Doppler flowmeter seems to measure blood flow in capillaries as well as in arteriovenous anastomoses, while the 133Xe method probably measures only capillary flow. A calibration of the laser-Doppler method against the 133Xe method would appear to be impossible in skin areas where arteriovenous anastomoses are present. The changes in blood flow during reactive hyperemia, orthostatic pressure changes, and venous stasis were found to be parallel as measured by the two methods in skin areas without shunt vessels. The laser-Doppler flowmeter would appear to be a useful supplement to the 133Xe washout method in cutaneous vascular physiology, but it is important to keep in mind that different parameters may be measured. PMID:6571731

Engelhart, M; Kristensen, J K

1983-01-01

7

A new laser Doppler flowmeter prototype for depth dependent monitoring of skin microcirculation  

Science.gov (United States)

Laser Doppler flowmetry (LDF) is now commonly used in clinical research to monitor microvascular blood flow. However, the dependence of the LDF signal on the microvascular architecture is still unknown. That is why we propose a new laser Doppler flowmeter for depth dependent monitoring of skin microvascular perfusion. This new laser Doppler flowmeter combines for the first time, in a device, several wavelengths and different spaced detection optical fibres. The calibration of the new apparatus is herein presented together with in vivo validation. Two in vivo validation tests are performed. In the first test, signals collected in the ventral side of the forearm are analyzed; in the second test, signals collected in the ventral side of the forearm are compared with signals collected in the hand palm. There are good indicators that show that different wavelengths and fibre distances probe different skin perfusion layers. However, multiple scattering may affect the results, namely the ones obtained with the larger fibre distance. To clearly understand the wavelength effect in LDF measurements, other tests have to be performed.

Figueiras, E.; Campos, R.; Semedo, S.; Oliveira, R.; Requicha Ferreira, L. F.; Humeau-Heurtier, A.

2012-03-01

8

Laser Doppler flow-meter assessment of iontophoretically applied norepinephrine on human finger skin circulation.  

Science.gov (United States)

A miniaturized technique to administer vasoactive substances iontophoretically into the human finger skin and to continuously assess the resulting reaction of the vessels is described. Cutaneous blood flow is measured with a laser Doppler flow-meter. The technique has been used in 9 healthy volunteers with norepinephrine as test substance. The described method is a convenient way to evaluate the effects of transdermally applied vasoactive substances in a semiquantitative way without risking central effects of the substance to influence the registered blood flow. PMID:2945868

Lindblad, L E; Ekenvall, L; Ancker, K; Rohman, H; Oberg, P A

1986-11-01

9

A new single-fibre laser Doppler flowmeter based on digital signal processing.  

Science.gov (United States)

A new laser Doppler flowmeter, based on a personal computer with a digital signal processor for detecting the blood perfusion in skeletal muscle, was designed and evaluated. An infrared laser diode (750 nm) fed a single optical fibre, 400 microns in diameter, which was introduced into the muscle. A PC equipped with a digital processing unit was used for emulation of the laser Doppler algorithm and for presentation of the measurement results. The Doppler signal power spectral density and corresponding flow values were visualized on the computer screen continuously in real-time, and could also be saved on the hard disk for off-line analyses. The graphic-user interface supported by Labwindows software made the system easy to use. It is possible to alter in the software the signal processing and the ways in which the signals and results are presented. The new system was evaluated by using a flow model as well as a mechanical model. The model studies showed linear relationships between particle velocity and flow in the range of 0-5 mm s-1. The system was also tested in measurements of the blood flow in the brachioradial muscle, and was found to have advantages over our previously used systems. PMID:8892236

Cai, H; Pettersson, H; Rohman, H; Larsson, S E; Oberg, P A

1996-10-01

10

Schlieren laser Doppler flowmeter for the human optical nerve head with the flicker stimuli  

Science.gov (United States)

We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the flowmeter is based on a Schlieren arrangement which collects only photons that encounter multiple scattering and are back-scattered out of the illumination point. LDF measurements are based on heterodyne detection of Doppler shifted back-scattered light. We also describe an automated analysis of the LDF signals which rejects artifacts and false signals such as blinks. By using a Doppler simulator consisting of a lens and a rotating diffusing wheel, we demonstrate that velocity and flow vary linearly with the speed of the wheel. A cohort of 12 healthy subjects demonstrated that flicker stimulation induces an increase of 17.8% of blood flow in the ONH.

Geiser, Martial H.; Truffer, Frederic; Evequoz, Hugo; Khayi, Hafid; Mottet, Benjamin; Chiquet, Christophe

2013-12-01

11

Evaluation of cutaneous blood flow responses by /sup 133/Xe washout and a laser-Doppler flowmeter  

Energy Technology Data Exchange (ETDEWEB)

A new method for noninvasive measurement of cutaneous blood flow is laser-Doppler flowmetry. The technique is based on the fact that laser light is back-scattered from the moving red blood cells, with Doppler-shifted frequencies; these impulses lead to photodetectors and are converted to flow signals. In this work we used a new system with a low noise level. Comparison was made between this technique and the atraumatic epicutaneous /sup 133/Xe technique for measurement of cutaneous blood flow during reactive hyperemia and orthostatic pressure changes. The laser-Doppler flowmeter seems to measure blood flow in capillaries as well as in arteriovenous anastomoses, while the /sup 133/Xe method probably measures only capillary flow. A calibration of the laser-Doppler method against the /sup 133/Xe method would appear to be impossible in skin areas where arteriovenous anastomoses are present. The changes in blood flow during reactive hyperemia, orthostatic pressure changes, and venous stasis were found to be parallel as measured by the two methods in skin areas without shunt vessels. The laser-Doppler flowmeter would appear to be a useful supplement to the 133Xe washout method in cutaneous vascular physiology, but it is important to keep in mind that different parameters may be measured.

Engelhart, M.; Kristensen, J.K.

1983-01-01

12

Pancreatic capillary blood flow during caerulein-induced pancreatitis evaluated by a laser-doppler flowmeter in rats  

Directory of Open Access Journals (Sweden)

Full Text Available PURPOSE: The pancreatic capillary blood flow (PCBF was studied to determine its alterations during caerulein-induced pancreatitis in rats. METHODS: Twenty rats were divided in groups: control and caerulein. A laser-Doppler flowmeter to measure PCBF continuously was used. Blood pressure (BP and heart rate (HR were monitored. Serum biochemistry analyses were determined. Histopathological study was performed. RESULTS: The PCBF measured a mean of 109.08 ± 14.54% and 68.24 ± 10.47% in control group and caerulein group, respectively. Caerulein group had a mean decrease of 31.75 ± 16.79%. The serum amylase was 1323.70 ± 239.10U.I-1 and 2184.60 ± 700.46U.I-1 in control and caerulein groups, respectively. There was a significant difference in the PCBF (p<0.05 and serum amylase (p<0.05 when compared to control and caerulein groups. Although micro and microvacuolization were seen in 30% in caerulein group, no significant difference was seen between the groups. CONCLUSION: A decrease in the PCBF may be one of the leading events and it is present before histopathological tissue injury had been established in this model of acute pancreatitis.

Meirelles Jr. Roberto Ferreira

2003-01-01

13

A Doppler flowmeter for use in theatre.  

Science.gov (United States)

We have developed a Doppler flowmeter based on a 10 MHz pencil probe and mean frequency estimator which overcomes many of the limitations of existing electromagnetic and ultrasonic flowmeters. The output of the flowmeter, which is proportional to the first moment of the Doppler power spectrum and hence mean blood velocity is linear from 1.3 to over 50 cm s-1 for pulsatile flow. Variation in vessel diameter and angle of insonation, which are the common sources of error in Doppler flowmetry, are minimised by constraining the vessel in a plastic cuff which fixes the probe angle at 50 degrees. A simple gauge is used to compress the vessel flat, before the cuff is applied, to measure the wall thickness to within 0.25 mm. The vessel internal diameter and hence blood flow can then be calculated using an experimentally determined calibration factor to compensate for non-even insonation. A range of sterilizable cuffs from 3-12 mm diameter have been built and the flowmeter is now being used routinely during all arterial reconstructive surgery. The accuracy and reproducibility of the system was tested for range of different sized silastic tubes on a hydraulic model and found to be less than 12% for vessels greater than 2 mm internal diameter. Satisfactory signals were easily obtained from all prosthetic materials with the exception of PTFE. The instantaneous output was compared to an electromagnetic flowmeter using a fast Fourier transform algorithm; the moduli of the harmonics were virtually identical but the Doppler system produced a smaller phase shift with increasing harmonics.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2949415

Beard, J D; Evans, J M; Skidmore, R; Horrocks, M

1986-11-01

14

Pancreatic capillary blood flow during caerulein-induced pancreatitis evaluated by a laser-doppler flowmeter in rats / Estudo das alterações do fluxo capilar pancreático após infusão de ceruleína avaliado por laser-Doppler em ratos  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: O fluxo capilar pancreático (FCP) foi estudado para determinar suas alterações durante a pancreatite aguda induzida por ceruleína, em ratos. MÉTODOS: Vinte ratos foram divididos em grupo controle e grupo ceruleína. Um laser-Doppler fluxímetro foi empregado para determinar, continuamente, o [...] FCP durante 120 minutos. A pressão arterial média (PAM) e a freqüência cardíaca (FC) foram determinadas, durante o experimento. Análise bioquímica sérica e estudo histopatológico, por microscopia ótica, do tecido pancreático foram realizados, ao final do experimento. RESULTADOS: O FCP foi em média 109,08 ± 2,17% e 68,24 ± 16,79% nos grupos controle e ceruleína , respectivamente. No grupo ceruleína, houve uma diminuição média de 31,75 ± 16,79%. Os níveis de amilase sérica foram de 1323,70 ± 239,10U.I-1 e 2184,60 ± 700,46U.I-1 nos grupos controle e ceruleína, respectivamente. Houve diferença significante (p Abstract in english PURPOSE: The pancreatic capillary blood flow (PCBF) was studied to determine its alterations during caerulein-induced pancreatitis in rats. METHODS: Twenty rats were divided in groups: control and caerulein. A laser-Doppler flowmeter to measure PCBF continuously was used. Blood pressure (BP) and hea [...] rt rate (HR) were monitored. Serum biochemistry analyses were determined. Histopathological study was performed. RESULTS: The PCBF measured a mean of 109.08 ± 14.54% and 68.24 ± 10.47% in control group and caerulein group, respectively. Caerulein group had a mean decrease of 31.75 ± 16.79%. The serum amylase was 1323.70 ± 239.10U.I-1 and 2184.60 ± 700.46U.I-1 in control and caerulein groups, respectively. There was a significant difference in the PCBF (p

Roberto Ferreira, Meirelles Jr.; Reginaldo, Ceneviva; José Liberato Ferreira, Caboclo; Michael M., Eisenberg.

15

Evaluation of a pulsed ultrasonic Doppler flowmeter  

Science.gov (United States)

The in vivo application of the pulsed ultrasound Doppler velocity meter (PUDVM) for measuring arterial velocity waveforms is reported. In particular, the performance of the PUDVM is compared with a hot film anemometer of proven accuracy.

Wells, M. K.

1973-01-01

16

The suitability of Doppler flowmeters for use in the minerals-processing industry  

International Nuclear Information System (INIS)

In this report, six commercially available Doppler flowmeters, which were operated under conditions likely to be encountered in the minerals-processing industry, are evaluated. The effects of the density and particle-size distribution of a flowing slurry and the optimum siting of the flowmeter probe are considered, and the results of tests on the response and linearity of the flowmeters are reported

17

Laser Doppler Velocimetry Workshop  

Science.gov (United States)

The potential of laser Doppler velocimetry as a technique for use in mapping flows in the several fluid systems under development for doing research on low-gravity processes, is investigated. Laser Doppler velocimetry techniques, equipment, and applications are summarized.

Owen, R. B.

1979-01-01

18

Laser Doppler Velocimetry Workshop.  

Science.gov (United States)

The potential of laser Doppler velocimetry as a technique for use in mapping flows in the several fluid systems under development for doing research on low-gravity processes, is investigated. Laser Doppler velocimetry techniques, equipment, and applicatio...

R. B. Owen

1979-01-01

19

Measurement of colonic blood flow with laser Doppler flowmetry.  

Science.gov (United States)

Colonic blood flow was measured with laser Doppler flowmetry during operation in 62 patients and during coloscopy in 15 patients. In 18 subjects mucosal and serosal laser Doppler signals were compared during 'resting' conditions, vascular occlusion, and reactive hyperemia. The mucosal (n = 36) and serosal (n = 36) flowmeter signals were of the same order of magnitude throughout the whole range of flowmeter signals (r = 0.96; p less than 0.001). In eight subjects total venous outflow from a colonic segment was measured simultaneously with flowmeter recordings from the serosal side. A correlation coefficient of 0.95 (n = 46; p less than 0.001) was obtained between total intestinal blood flow and serosal flowmeter signal during 'resting' and reduced blood flows. In this flow range a calibration curve was constructed for interpretation of the flowmeter signals in absolute flow units. The wall thickness of the bowel determined the quantitative relationship between flowmeter signal and total intestinal blood flow. It is concluded that laser Doppler flowmetry represents a potentially very interesting non-invasive, continuous method for the quantitative study of human intestinal blood flow. PMID:2946071

Ahn, H; Lindhagen, J; Lundgren, O

1986-09-01

20

Flowmeters  

International Nuclear Information System (INIS)

A fast response flowmeter for high speed transient flow measurement in water has a threaded body in a threaded hole in a cylinder confining the flow. The body carries a blade extending into the flow and disposed so that the face of the blade is presented to the flow. The blade carries a strain gauge and flow is measured in terms of strain. An apparatus for calibrating the flowmeter is also described. (author)

 
 
 
 
21

Flowmeter  

International Nuclear Information System (INIS)

A flowmeter with a conical rotor is described resting with the cone-shaped shell on a conical wall of the housing for non-flowing medium and lifting from the wall for flowing medium; in addition, it has slots in the cone-shaped shell. By a special shape and retaining slots it is achieved that the rotor exactly follows the changes of the flow velocity. (RW)

22

Evaluation of laser Doppler flowmetry in the assessment of intestinal blood flow in cat.  

Science.gov (United States)

Laser Doppler flowmetry with a differential detector system has been used in the assessment of blood flow in the feline small intestine. Simultaneous mucosal and serosal laser Doppler flowmeter recordings were compared with total blood flow of a bowel segment measured by an optical drop-recorder unit in 6 cats. Blood flow through the muscularis layer was estimated using the 85Kr washout technique. A correlation coefficient of r = 0.96 (mucosal recordings = 90, serosal recordings = 80, p less than 0.001) was obtained between laser Doppler flowmeter output signals and total blood flow at different levels of vascular tone, regardless of whether the flowmeter recordings were made from the mucosal or the serosal side of the bowel wall. At intense vasodilation, the flowmeters showed a tendency to underestimate blood flow. The flowmeter signals were at variance with the muscularis blood flow but were clearly correlated to the calculated mucosal-submucosal blood flow. The uneven blood flow distribution in the intestinal wall did not affect the ability of the flowmeters to reflect total blood flow from either side of the bowel wall. A calibration curve could be constructed for approximate interpretation of the laser Doppler signals in absolute flow units. However, further experiments in humans and further development of the technique must be performed to elucidate clinical applications of the method. PMID:3156061

Ahn, H; Lindhagen, J; Nilsson, G E; Salerud, E G; Jodal, M; Lundgren, O

1985-04-01

23

Holographic laser Doppler ophthalmoscopy  

CERN Document Server

We report laser Doppler ophthalmoscopic fundus imaging in the rat eye with near-IR heterodyne holography. Sequential sampling of the beat of the reflected radiation against a frequency-shifted optical local oscillator is made onto an array detector. Wide-field maps of fluctuation spectra in the 10 Hz to 25 kHz band exhibit angiographic contrasts in the retinal vascular tree without requirement of an exogenous marker.

Simonutti, Manuel; Sahel, J A; Gross, Michel; Samson, Benjamin; Magnain, Caroline; Atlan, Michael; 10.1364/OL.35.001941

2010-01-01

24

Direct calibration of a totally implantable pulsed Doppler ultrasonic blood flowmeter.  

Science.gov (United States)

A totally implantable pulsed Doppler ultrasonic blood flowmeter has recently been developed to provide information on the velocity-flow profile in a vessel as well as its diameter. Volume flow can be indirectly obtained according to the formula: Q = (phi/4)(diam)2-v. In order to determine the accuracy of this estimate, in vivo direct bleedout measurements were performed on the abdominal aorta of six dogs with an overall accuracy in 77 trials of +2.0 +/- 8.7% (mean +/- 1 SD). The best-fit mean linear regression line was found to be: flowmeter output = 1.013-true flow + 5.1 ml/min. The scatter in the flowmeter's accuracy is thought to be due to small variations in the angle of the transducer. The source of the 2% overestimation in the mean accuracy could not be directly attributed to any one condition; the error is sufficiently small that in many cases it can be neglected. PMID:140611

Allen, H V; Anderson, M F; Meindl, J D

1977-05-01

25

Assessment of blood flow in the small intestine with laser Doppler flowmetry.  

Science.gov (United States)

Blood flow in the small intestine was assessed in 48 patients by laser Doppler flowmetry. Mucosal and serosal flowmeter signals were compared during 'resting' conditions, vascular occlusion, and reactive hyperemia. Serosal flowmeter recordings were compared with the total blood flow of a bowel segment as measured by venous collection. The magnitudes of the mucosal (n = 49) and serosal (n = 49) flowmeter signals were comparable throughout the whole range of flowmeter signals (r = 0.97; p less than 0.001). A correlation coefficient of 0.95 (n = 51; p less than 0.001) was obtained between serosal flowmeter signals and total blood flow during 'resting' and reduced blood flows. During vasodilatation after a vascular occlusion, blood flow was underestimated by the flowmeter. A calibration curve could be constructed for approximate interpretation of the flowmeter signals in absolute flow units. The present study underlines the potential of laser Doppler flowmetry in the assessment of blood flow in the human small intestine. PMID:2946070

Ahn, H; Lindhagen, J; Nilsson, G E; Oberg, P A; Lundgren, O

1986-09-01

26

Laser Doppler velocimetry primer  

Science.gov (United States)

Advanced research in experimental fluid dynamics required a familiarity with sophisticated measurement techniques. In some cases, the development and application of new techniques is required for difficult measurements. Optical methods and in particular, the laser Doppler velocimeter (LDV) are now recognized as the most reliable means for performing measurements in complex turbulent flows. And such, the experimental fluid dynamicist should be familiar with the principles of operation of the method and the details associated with its application. Thus, the goals of this primer are to efficiently transmit the basic concepts of the LDV method to potential users and to provide references that describe the specific areas in greater detail.

Bachalo, William D.

1985-01-01

27

Laser Doppler Imaging of Microflow  

CERN Document Server

We report a pilot study with a wide-field laser Doppler detection scheme used to perform laser Doppler anemometry and imaging of particle seeded microflow. The optical field carrying the local scatterers (particles) dynamic state, as a consequence of momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne digital holography, which is used to map the scattered field in the object plane at a tunable frequency with a multipixel detector. We show that wide-field heterodyne laser Doppler imaging can be used for quantitative microflow diagnosis; in the presented study, maps of the first-order moment of the Doppler frequency shift are used as a quantitative and directional estimator of the Doppler signature of particles velocity.

Gross, Michel; Leng, Jacques

2013-01-01

28

Laser Doppler methods in electrophoresis  

Science.gov (United States)

Electrophoretic motion of particles, molecules, and biological cells can be readily measured by laser Doppler techniques. Small frequency shifts associated with the motion of the scatterers are detected by heterodyne detection of the scattered laser light. The principles of laser light scattering and heterodyne detection are reviewed. The central experimental problems associated with the application of electric fields to conducting solutions are considered in detail. Various types of laser Doppler spectrometers and electrophoresis chambers are compared both from fundamental physical points of view as well as in terms of resolving power of standard marker cells. As applications of the laser Doppler technique, measurements on proteins, virtues, nucleic acids, bioparticles and biological cells are reviewed.

Uzgiris, Egidijus E.

29

Ultrasound propagation in steel piping at electric power plant using clamp-on ultrasonic pulse doppler velocity-profile flowmeter  

International Nuclear Information System (INIS)

Venturi nozzles are widely used to measure the flow rates of reactor feedwater. This flow rate of nuclear reactor feedwater is an important factor in the operation of nuclear power reactors. Some other types of flowmeters have been proposed to improve measurement accuracy. The ultrasonic pulse Doppler velocity-profile flowmeter is expected to be a candidate method because it can measure the flow profiles across the pipe cross sections. For the accurate estimation of the flow velocity, the incidence angle of ultrasonic entering the fluid should be carefully estimated by the theoretical approach. However, the evaluation of the ultrasound propagation is not straightforward for the several reasons such as temperature gradient in the wedge or mode conversion at the interface between the wedge and pipe. In recent years, the simulation code for ultrasound propagation has come into use in the nuclear field for nondestructive testing. This article analyzes and discusses ultrasound propagation in steel piping and water, using the 3D-FEM simulation code and the Kirchhoff method, as it relates to the flow profile measurements in power plants with the ultrasonic pulse Doppler velocity-profile flowmeter. (author)

30

Doppler Free Laser Spectroscopy  

Science.gov (United States)

In this experiment you will use a technique known as saturation-absorption spectroscopy to study the hyperfine structure (hfs) of rubidium. This particular method is designed to overcome the limitations imposed by the Doppler-broadening of spectral lines while avoiding the need to work at low temperatures.

2012-01-09

31

Laser Doppler velocimetry for continuous flow solar-pumped iodine laser system  

Science.gov (United States)

A laser Doppler velocimetry (LDV) system was employed to measure the flow velocity profile of iodide vapor inside laser tubes of 36 mm ID and 20 mm ID. The LDV, which was operated in the forward scatter mode used a low power (15 mW) He-Ne laser beam. Velocity ranges from 1 m/s was measured to within one percent accuracy. The flow velocity profile across the laser tube was measured and the intensity of turbulence was determined. The flow of iodide inside the laser tube demonstrated a mixture of both turbulence and laminar flow. The flowmeter used for the laser system previously was calibrated with the LDV and found to be in good agreement.

Tabibi, Bagher M.; Lee, Ja H.

1991-01-01

32

Laser Doppler blood flowmetry multiple scattering study during reactive hyperaemia  

Science.gov (United States)

The goal of the present work is to analyse multiple scattering in laser Doppler blood flowmetry reactive hyperaemia experiments. For this purpose, three different kinds of outputs from a laser Doppler flowmeter are studied: the concentration of moving blood cells (CMBC), the linearised unfiltered flux and the unlinerised unfiltered flux. Three vascular occlusion lengths of time are observed on eight healthy volunteers. For each reactive hyperaemia experiment, the difference between the linearised unfiltered flux and the unlinearised unfiltered flux is calculated to examine the multiple scattering. The latter is considered as a function of time and compared to blood flux and concentration of erthrocyte variations. This work shows that, during reactive hyperaemia, the multiple scattering is predominant when the CMBC signal reaches its peak, the latter occurring at the peak of perfusion. However, very rapidly the multiple scattering becomes negligible whereas the CMBC and the linearised flux still take high values. Moreover, the longer the occlusion length of time, the longer the presence of the multiple scattering.

Humeau, Anne; Saumet, Jean L.; L'Huillier, Jean P.

2000-11-01

33

Borescopic Laser Doppler Velocimetry probe  

Science.gov (United States)

A miniature fiber-optic, single-velocity-component Laser Doppler Velocimetry (LDV) probe for measurement in cramped spaces, where access is very limited, has been designed, constructed, and tested. The probe design allows the main probe dimensions to be small (7mm in diameter). In addition, the proposed back-scatter collection scheme allows the main section to be as long as needed to access remote locations. The laser beams are first collimated by passing them through two separate collimating lenses. The collimated light then passes through 1 mm holes machined into a right angle prism-mirror and are focused to form the measurement probe volume using the focusing lens placed at the end of the probe extension tube. The light scattered by the particles in the flow is collected back by the focusing lens and is collimated. The collimated light then reflects off the right-angle mirror by 90 degrees, passes through the receiving lens, and is focused to the receiving fiber terminator. The receiving fiber-optic cable transmits the collected light to the photo-multiplier tube which then converts the signal into an electrical signal for further processing of the data. The probe working principle was proven in two types of jet flows.

O'Brien, Kory T.

34

Local regulation of blood flow evaluated simultaneously by 133-xenon washout and laser Doppler flowmetry  

Energy Technology Data Exchange (ETDEWEB)

The laser Doppler flowmeter and the 133-Xenon washout techniques of measuring cutaneous blood flow were compared for measuring the vasoconstrictor response of the hand during orthostatic maneuvres. Important discrepancies were detected for the two methods. When the hand was lowered by 40 cm a 40% decrease in blood flow was detected by the 133-Xenon method, while a 60% decrease was seen by the laser Doppler technique. Lowering the hand by 50 cm resulted in no further blood flow decrease when using the 133-Xenon method, but an 80% blood flow decrease was recorded with the laser Doppler method. A marked decrease in blood flow was recorded by the laser Doppler technique in hands that were sympathectomized or a hand that was subjected to a nerve blockade, strategies which should eliminate the orthostatic vasoconstrictor response of superficial cutaneous vessels. The 133-Xenon technique did not detect any blood flow changes in hands without sympathetic tone. We found the laser Doppler flowmetry technique unsatisfactory for measurement of blood flow changes that occur in nutritional vessels as this method measures total skin blood flow including non-capillary vessels.

Engelhart, M.; Petersen, L.J.; Kristensen, J.K.

1988-11-01

35

Laser Doppler diagnostics for orthodontia  

Science.gov (United States)

The results of statistical analysis of Doppler spectra of intensity fluctuations of light, scattered from mucous membrane of oral cavity of healthy volunteers and patients, abused by the orthodontic diseases, are presented. Analysis of Doppler spectra, obtained from tooth pulp of patients, is carried out. New approach to monitoring of blood microcirculation in orthodontics is suggested. Influence of own noise of Doppler measuring system on formation of the output signal is studied.

Ryzhkova, Anastasia V.; Lebedeva, Nina G.; Sedykh, Alexey V.; Ulyanov, Sergey S.; Lepilin, Alexander V.; Kharish, Natalia A.

2004-06-01

36

Beam-forming techniques with applications to pulsed Doppler ultrasonic flowmeters  

Science.gov (United States)

The near-field and array approaches to beam forming appear to be the most practical and useful methods for providing uniform illumination of the cross section of blood vessels. Through the near-field approach, the required beam patterns are produced in the near field of pulsed transducers and, as a result, it is most suitable for peripheral applications. Field patterns of pulsed transducers are defined and are investigated by theoretical analysis, numerical simulation, and experimental characterization to verify the validity and indicate the limitations of this approach. Transducers are designed and fabricated, based on these results, and are employed in the preliminary flowmeter system evaluation. The use of transducer arrays is the only viable approach to deepbody measurements and flexible beamwidth adjustment. A theory, founded on the finite Fourier-Bessel and Dini series expansions, is developed to synthesize circularly symmetrical beam patterns by means of concentric annular arrays. Its application to the generation of variable-width uniform beams results in a canonical design procedure. A prototype transducer array suitable for transcutaneous cardiac-output estimation was developed.

Fu, C. C.

37

A compact, laser diode based phase Doppler system  

Science.gov (United States)

Recent advances in laser diode technology provide the opportunity to reduce the size and cost of laser Doppler and phase Doppler anemometry systems. The application of laser diodes to phase Doppler systems is discussed, and the construction of a compact, laser diode based Doppler system is described. Test measurements in a monosized drop stream, a water spray and a fluidized bed are reported, demonstrating the functionality of such a system.

Sellens, R. W.

1990-05-01

38

Analysis of ultrasound propagation in high-temperature nuclear reactor feedwater to investigate a clamp-on ultrasonic pulse doppler flowmeter  

International Nuclear Information System (INIS)

The flow rate of nuclear reactor feedwater is an important factor in the operation of a nuclear power reactor. Venturi nozzles are widely used to measure the flow rate. Other types of flowmeters have been proposed to improve measurement accuracy and permit the flow rate and reactor power to be increased. The ultrasonic pulse Doppler system is expected to be a candidate method because it can measure the flow profile across the pipe cross section, which changes with time. For accurate estimation of the flow velocity, the incidence angle of ultrasound entering the fluid should be estimated using Snell's law. However, evaluation of the ultrasound propagation is not straightforward, especially for a high-temperature pipe with a clamp-on ultrasonic Doppler flowmeter. The ultrasound beam path may differ from what is expected from Snell's law due to the temperature gradient in the wedge and variation in the acoustic impedance between interfaces. Recently, simulation code for ultrasound propagation has come into use in the nuclear field for nondestructive testing. This article analyzes and discusses ultrasound propagation, using 3D-FEM simulation code plus the Kirchhoff method, as it relates to flow profile measurement in nuclear reactor feedwater with the ultrasonic pulse Doppler system. (author)

39

Atmospheric laser Doppler velocimetry - An overview  

Science.gov (United States)

Research, development, and application of atmospheric laser Doppler velocimetry are overviewed. Consideration is given to operation principles of CO2 heterodyne systems. Global wind, pollution, V/STOL flow, and true airspeed measurements are outlined. Wind energy, dust devils, water spouts, tornadoes, and aircraft wake vortices are covered.

Bilbro, J. W.

1980-01-01

40

Bone tissue phantoms for optical flowmeters at large interoptode spacing generated by 3D-stereolithography.  

Science.gov (United States)

A bone tissue phantom prototype allowing to test, in general, optical flowmeters at large interoptode spacings, such as laser-Doppler flowmetry or diffuse correlation spectroscopy, has been developed by 3D-stereolithography technique. It has been demonstrated that complex tissue vascular systems of any geometrical shape can be conceived. Absorption coefficient, reduced scattering coefficient and refractive index of the optical phantom have been measured to ensure that the optical parameters reasonably reproduce real human bone tissue in vivo. An experimental demonstration of a possible use of the optical phantom, utilizing a laser-Doppler flowmeter, is also presented. PMID:25136496

Binzoni, Tiziano; Torricelli, Alessandro; Giust, Remo; Sanguinetti, Bruno; Bernhard, Paul; Spinelli, Lorenzo

2014-08-01

 
 
 
 
41

Laser Doppler measurement of cutaneous blood flow  

International Nuclear Information System (INIS)

Laser Doppler velocimetry is an instrument system which has only recently been applied to the evaluation and quantitation of perfusion in the micro-vascular bed. The instrument is based on the Doppler principle, but uses low power laser light rather than the more commonly used ultrasound, and has a sample volume of approximately 1 mm/sup 3/. As it is non-invasive, it can be used on any skin surface or exposed microvascular bed and provides a continuous semi-quantitative measure of microcirculatory perfusion, it has a number of advantages as compared to other cutaneous blood flow measurement techniques. Initial studies have shown that it is easily used, and it has demonstrated good correlation with both xenon radio-isotope clearance and microsphere deposition techniques. Areas of current evaluation and utilization are in most major areas of medicine and surgery and include plastic, vascular and orthopaedic surgery, dermatology, gastro-enterology, rheumatology, burns and anaesthesiology

42

Catadioptric optics for laser Doppler velocimeter applications  

Science.gov (United States)

This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.

Dunagan, Stephen E.

1989-01-01

43

Laser Doppler velocimeter measurements in tornadolike vortices  

Science.gov (United States)

Using data recently gathered within the Purdue University tornado vortex chamber II (PU TVC II) using a state-of-the-art laser Doppler velocimeter (LDV), we present and discuss radial and vertical profiles of measured radial and tangential velocity components and derived vertical velocity component. A mean offset of the vortex from the centerline of the tornado vortex chamber (TVC) required a coordinate transformation of the measured data from a "chamber" reference frame to a "vortex" reference frame. Further, the impact of small vortex translations (vortex wander) on the data set is examined through the use of a simple mathematical model of the data collection process.

Lund, Donald E.; Snow, John T.

44

Establishment of normal ranges of laser Doppler blood flow in autologous tissue transplants.  

Science.gov (United States)

Over a 3-year period, 136 patients were monitored following free autologous tissue transplantation using a laser Doppler flowmeter linked to a computerized data-acquisition system. This monitoring system has indicated perfusion compromise in free flaps more rapidly than clinical observation alone. Most important, this has resulted in an increase in salvage rate from 50.0 to 82.4 percent. In addition, our overall success rate has increased from 92.6 to 97.8 percent since introducing this monitor clinically. Computerization also has facilitated the collection of data, which has enabled us to establish expected values for postoperative blood flow in several types of donor tissues used for microvascular reconstruction. Finally, this computerized monitoring system has relieved personnel from basing decisions on subjective data. PMID:1824878

Clinton, M S; Sepka, R S; Bristol, D; Pederson, W C; Barwick, W J; Serafin, D; Klitzman, B

1991-02-01

45

Parallax effects in laser Doppler spectroscopy  

International Nuclear Information System (INIS)

Parallax effects in laser Doppler spectroscopy, associated with the variation of the scattering angle during motion of a particle through the probed volume, were investigated by a numerical simulation method based on the Mie scattering theory. It was found that, in general, the shifts of the spectral profile parameters (the average frequency, broadening, asymmetry, and kurtosis) become significant as the parallax number N??=(2/?)?? (? is the angular size of the probed volume, ? = ?d/? is the relative particle diameter) increases. The anomalous ranges of the parameters of the particle and of the optical system, in which marked distortions (such as the polymodal nature and the splitting of the spectral profile) are observed even for a low parallax number (N?? || 1), were discovered. (laser applications and other topics in quantum electronics)

46

A miniature, battery operated laser Doppler anemometer  

Science.gov (United States)

A hand-held lithium battery-operated 30 mW laser diode backscatter LDA is described. The LDA is constructed in a tube of 30 mm diameter and 250 mm length. The tube also contains microoptical beam collimation, a miniature galilean telescope, a miniature beamsplitter and prism, spatial filtering, a solid state detector, an electronic amplifier, a bandpass filter, a discriminator, and either (1) telemetry to transmit Doppler signals to a remote signal processor, or (2) integral frequency analysis and LCD display of single-component velocity. All the components are mounted on microoptical benching. The velocity measurement range is as much as a few meters per second, and the system operates for a few hours before battery replacement is necessary. The development of this LDA into modular mechanical form for easier replication is described. How the principles of this concept are extended to laser TOF anemometry and particle sizing is also discussed.

Brown, R. G. W.; Burnett, J. G.; Hackney, N.

47

Laser Doppler blood flow measurements of common cutaneous donor sites for reconstructive surgery.  

Science.gov (United States)

The purpose of this study was to evaluate cutaneous blood flow in regions commonly used as donor sites in reconstructive surgery in order to better establish normal flow ranges. Flow was measured with the TSI Laserflo BPM 403 in 27 healthy volunteers and compared to the flow in uncomplicated postoperative autologous tissue transplants. The forehead produced the highest flow, with an average value of 6.50 +/- 0.31 (mean +/- SE), and the dorsalis pedis had the lowest flow, with an average value of 0.60 +/- 0.04. Gender differences were noted in the latissimus dorsi, pectoralis major, and rectus abdominis areas. There were no significant differences between smokers and nonsmokers, hand dominance, musculocutaneous and fasciocutaneous tissues, or supine and sitting body positions. Flow levels in volunteers were similar to those in postoperative surviving autologous tissue transplants. The site-specific flow and flow changes over long time periods (hours) have helped clinical monitoring of 77 patients in the last 24 months. In every case identified by the flowmeter as decreased perfusion, a definite etiology for low reduction was documented. Complications occurred in 12 patients, and the rate of salvaging compromised tissue has increased from 50 percent using temperature monitoring and clinical observation to 83 percent with the computerized laser Doppler flowmeter. PMID:2179975

Goldberg, J; Sepka, R S; Perona, B P; Pederson, W C; Klitzman, B

1990-04-01

48

Laser Doppler velocimetry and its application to turbulent flow measurements  

International Nuclear Information System (INIS)

The present state of development is reviewed of laser Doppler velocimetry, a new method of fluid flow characteristic measurement. The physical principles involved, the classification of the optical schemes utilized, the typical experimental arrangements, the nature of the laser Doppler velocimeter signal and methods of signal analysis are discussed. The comprehensive bibliography contains more than 300 references from 1964 to 1974. (author)

49

Wide-field stabilized Doppler flowmetry with the tracking scanning laser ophthalmoscope (TSLO)  

Science.gov (United States)

Real time, high-speed image stabilization with a retinal tracking scanning laser ophthalmoscope (TSLO) enables new approaches to established diagnostics. Large dynamic range, wide-field stabilized Doppler flowmetry imaging was demonstrated in initial human subject testing with a large frequency range and up to 40 deg fields of view. The retinal tracking system uses a confocal reflectometer with a closed loop optical servo system to lock onto features in the ocular fundus. The fundus imaging method is a quasi-confocal line-scanning laser ophthalmoscope (LSLO). By locking to the retina and performing a slow scan of the laser line imager taking up to 30 seconds, frequency-resolved retinal perfusion and vascular flow images were obtained. The tracking system and auto-relock algorithms after blinks allowed the full image to be captured free of eye motion artifacts. Image cubes comprised of 512 by 512 spatial pixels by 512 or more temporal pixels were captured with a line rate of up to 20 kHz. The line sensor integrates, as opposed to conventional SLO flowmeters, thus minimizing aliasing that contributes to velocity errors. Fast Fourier Transform (FFT) power spectra at each image pixel were computed. Image reconstruction accuracy was typically better than one pixel width. Doppler frequency resolution from 14 Hz to 3.675 kHz was demonstrated in this work. Pulsatile flow effects were observed. Normal adult subjects and patients were tested with or without mydriasis to characterize flow imaging performance.

Ferguson, R. D.; Hammer, Daniel X.; Elsner, Ann E.; Burns, Stephen A.; Webb, Robert H.; Weiter, John J.

2004-07-01

50

Application of laser Doppler velocimeter to chemical vapor laser system  

Science.gov (United States)

A laser Doppler velocimeter (LDV) system was used to measure iodide vapor flow fields inside two different-sized tubes. Typical velocity profiles across the laser tubes were obtained with an estimated +/-1 percent bias and +/-0.3 to 0.5 percent random uncertainty in the mean values and +/-2.5 percent random uncertainty in the turbulence-intensity values. Centerline velocities and turbulence intensities for various longitudinal locations ranged from 13 to 17.5 m/sec and 6 to 20 percent, respectively. In view of these findings, the effects of turbulence should be considered for flow field modeling. The LDV system provided calibration data for pressure and mass flow systems used routinely to monitor the research laser gas flow velocity.

Gartrell, Luther R.; Hunter, William W., Jr.; Lee, Ja H.; Fletcher, Mark T.; Tabibi, Bagher M.

1993-01-01

51

Ultraviolet-excimer laser-based incoherent Doppler lidar system  

Science.gov (United States)

The topics covered include the following: principles of Doppler measurements, laser backscatter, eye safety, demonstration concepts, the wavelength-meter, the interferometer detector, return signal model, and comparison of incoherent and coherent lidars.

Mcdermid, I. Stuart; Laudenslager, James B.; Rees, David

1985-01-01

52

Muscle activity characterization by laser Doppler Myography  

International Nuclear Information System (INIS)

Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin

53

Muscle activity characterization by laser Doppler Myography  

Science.gov (United States)

Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin.

Scalise, Lorenzo; Casaccia, Sara; Marchionni, Paolo; Ercoli, Ilaria; Primo Tomasini, Enrico

2013-09-01

54

Evaluating microcirculation by pulsatile laser Doppler signal  

Energy Technology Data Exchange (ETDEWEB)

Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 {+-} 5.54 ms, mean {+-} SD) than in WKY (76.92 {+-} 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 {+-} 1.98 ms) than in WKY (58.02 {+-} 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods.

Chao, P T [Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (China); Department of Physics, National Taiwan Normal University, Taipei, Taiwan (China); Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Jan, M Y [Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Hsiu, H [Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Department of Electrical Engineering, Yuan-ze University, Chun-Li, Taiwan (China); Hsu, T L [Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Wang, W K [Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (China); Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Wang, Y Y Lin [Department of Physics, National Taiwan Normal University, Taipei, Taiwan (China); Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China)

2006-02-21

55

Evaluating microcirculation by pulsatile laser Doppler signal  

International Nuclear Information System (INIS)

Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 ± 5.54 ms, mean ± SD) than in WKY (76.92 ± 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 ± 1.98 ms) than in WKY (58.02 ± 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods

56

Laser Doppler technology applied to atmospheric environmental operating problems  

Science.gov (United States)

Carbon dioxide laser Doppler ground wind data were very favorably compared with data from standard anemometers. As a result of these measurements, two breadboard systems were developed for taking research data: a continuous wave velocimeter and a pulsed Doppler system. The scanning continuous wave laser Doppler velocimeter developed for detecting, tracking and measuring aircraft wake vortices was successfully tested at an airport where it located vortices to an accuracy of 3 meters at a range of 150 meters. The airborne pulsed laser Doppler system was developed to detect and measure clear air turbulence (CAT). This system was tested aboard an aircraft, but jet stream CAT was not encountered. However, low altitude turbulence in cumulus clouds near a mountain range was detected by the system and encountered by the aircraft at the predicted time.

Weaver, E. A.; Bilbro, J. W.; Dunkin, J. A.; Jeffreys, H. B.

1976-01-01

57

Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser  

Science.gov (United States)

We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO2 laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

Lee, Teaghee; Choi, Jong Woon; Kim, Yong Pyung

2012-09-01

58

Pulsed laser-Doppler flowmetry for monitoring deep perfusion  

Science.gov (United States)

Measurements have been carried out using a pulsed laser-Doppler setup. The main advantage of pulsing a laser-diode is that much higher peak powers can be used, allowing a larger source-detector separation, resulting in a larger penetration depth. The method enables e.g. monitoring of cerebral perfusion as well as monitoring perfusion through organs (e.g. kidney).

Kolkman, Roy G. M.; Hondebrink, Erwin; Bolt, Rene A.; Steenbergen, Wiendelt; de Mul, Frits F. M.

2001-10-01

59

Miniature Laser Doppler Velocimeter for Measuring Wall Shear  

Science.gov (United States)

A miniature optoelectronic instrument has been invented as a nonintrusive means of measuring a velocity gradient proportional to a shear stress in a flow near a wall. The instrument, which can be mounted flush with the wall, is a variant of a basic laser Doppler velocimeter. The laser Doppler probe volume can be located close enough to the wall (as little as 100 micron from the surface) to lie within the viscosity-dominated sublayer of a turbulent boundary layer. The instrument includes a diode laser, the output of which is shaped by a diffractive optical element (DOE) into two beams that have elliptical cross sections with very high aspect ratios.

Gharib, Morteza; Modarress, Darius; Forouhar, Siamak; Fourguette, Dominique; Taugwalder, Federic; Wilson, Daniel

2005-01-01

60

Three-dimensional imaging techniques for microvessels using multipoint laser Doppler velocimeter  

Science.gov (United States)

We have succeeded in measuring the blood flow velocity in microvessels noninvasively, using an advanced multipoint laser Doppler velocimeter (M-LDV). We developed the M-LDV using a semiconductor laser with a wavelength of 785 nm and were able to improve the measurement of opaque fluids, including blood. Initially, the calibration of our equipment was checked by measuring the flow velocity of water in the glass tube with an inner diameter of 0.55 mm. These values were equal to that calculated from the indicated values of a flowmeter and succeeded in imaging the flow velocity distribution in the glass tube as two-dimensional images. Finally, we enlarged the optical magnification, and measured microvessels of an experimental mouse's ear, and succeeded in imaging the blood flow velocity in microvessels as three-dimensional images. Compared with our previous report [T. Andoh et al., Jpn. J. Appl. Phys., Part 1 48, 017002 (2009)], the spatial resolution was improved by more than a factor of 10.

Ishida, H.; Shirakawa, H.; Andoh, T.; Akiguchi, S.; Kobayashi, D.; Ueyama, K.; Kuraishi, Y.; Hachiga, T.

2009-09-01

 
 
 
 
61

Blood flow measurement by laser Doppler method in orofacial region  

Directory of Open Access Journals (Sweden)

Full Text Available Laser Doppler is a noninvasive, objective, reproducible and painless method for measuring blood flow in tissue microcirculation. This method is based on the Doppler effect, the change in frequency of light reflecting from blood cells in motion. Light from helium-neon laser through optical fibers and probes is directed to the surface of the tissue in which the flow is measured. Light portion is reflected from the cells in motion and changes the frequency while another portion is reflected from the static tissue maintaining the same frequency as the initial light. The total reflected light, with changed and original frequency, reaches photo detector in the same probe where the emitter is and it is transformed into electrical impulse. In the orofacial region the laser Doppler method is used to examine blood flow in the mandible, teeth pulp and masticator muscles. A significant drawback of the laser Doppler method is its sensitivity to the ambient conditions during measuring and the fact that blood flow is measured in all blood vessels of examined microregion. Therefore, the circulation of isolated individual blood vessels can not be monitored. Laser Doppler method can give reliable indicators of blood flow in mouth tissue and method is acceptable for the patients.

Grga ?urica

2010-01-01

62

Critical design parameters in laser Doppler perfusion imaging  

Science.gov (United States)

Laser Doppler Perfusion Imaging (LDPI) is a method for visualization of tissue blood perfusion. A low power laser beam is used to step-wise scan a tissue area of interest and a perfusion estimate based on the backscattered, partially Doppler broadened, light is generated. Although the basic operating principle of LDPI is the same as that of conventional Laser Doppler Perfusion Monitoring (LDPM), significant differences exist between the implementation of the methods which must be taken into account in order to generate high quality perfusion images. The purpose of this study is to investigate the relevance of a number of LDPI design parameters, such as: (1) The influence of artifact noise when using a continuously moving laser beam instead of a step-wise moving beam to scan the image. (2) The signal processor output's dependency on the distance between the measurement object and the scanner head when using collimated laser light. (3) The speed and mode of the scanning. The results show a substantial rise in the noise level when using a continuously moving beam as opposed to a step-wise. Skin measurements using a collimated laser beam demonstrated an amplification factor dependency on the distance between the skin surface and the scanner head not present when using a divergent laser beam. The scanning speed is limited by the trade-off between the Doppler signal lower cut-off frequency and the image quality.

Arildsson, Mikael L.; Nilsson, Gert E.; Wardell, Karin

1996-05-01

63

Optimization of cw-QC lasers for Doppler and sub-Doppler molecular spectroscopy  

Science.gov (United States)

Inter-subband (Type I) quantum-cascade (QC) lasers have shown the potential to generate tunable mid-IR radiation with narrow intrinsic linewidths (optical configurations which preclude significant optical feedback and need for stringent mode coupling alignments, the cw-DFB-QC lasers show great promise to do high resolution sub-Doppler spectroscopy. By serendipitous events, a varient of 'mode- or level-crossing' spectroscopy was probably rediscovered, which may allow very high resolution, sub-Doppler features and/or hyperfine alignments to be probed with 'uni-directional' topologies. We will primarily discuss the basic features of the 'uni-directional' sub-Doppler spectroscopy concept in this report. It shows potential to be exploitable in multi-pass cells or ring configurations. The phenomena of satuation 'dips' in molecular transitions appear to be very accessible with sinusoidally current-modulated DFB-QC lasers. Observations of sub-Doppler structures, either induced by residual AM 'pulsation dips' and/or hyperfine level-crossing effects (due to weak Zeeman splittings by the earth's B-field) can be recovered with good contrast. If this phenomena is indeed implicated with long-lived coherent hyperfine alignments, due perhaps to coherent population trapping in 'dark-states,' then sub-Doppler signals from saturated 'level-crossings' can potentially be seen without recourse to expensive polarization optics, nor elaborate beam shaping and isolation techniques.

Kelly, James F.; Disselkamp, Robert S.; Sams, Robert L.; Blake, Thomas A.; Sharpe, Steven W.; Richter, Dirk A.; Fried, Alan

2002-09-01

64

Aeroacoustic flowmeter  

Science.gov (United States)

The flowmeter is based on a measurement of phase difference between two points on the circumference of a pipe separated axially by an integral multiple of sound wavelength. Plane sound waves are generated aeroacoustically by a non-protruding ring cavity energized either directly by the flow or by a subsidiary flow of the same medium. The frequency of the aeroacoustic source varies with temperature and therefore the temperature can be obtained. In the case of steam flow, temperature can be measured independently and therefore from the measured frequency (or speed of sound), the quality of wet steam can be measured. The flowmeter is linear in velocity and no calibrations are required.

Shakkottai, Parthasarathy (Inventor); Kwack, Eug Y. (Inventor)

1990-01-01

65

Ultrasonic flowmeters  

International Nuclear Information System (INIS)

A prototype ultrasonic flowmeter was assembled and tested. The theoretical basis of this prototype ultrasonic flowmeter is reviewed; the equipment requirements for a portable unit are discussed; the individual electronic modules contained in the prototype are described; the operating procedures and configuration are explained; and the data from preliminary calibrations are presented. The calibration data confirm that the prototype operates according to theoretical predictions and can indeed provide nonintrusive flow measurements to predicted accuracies for pipes larger than two inches, under single phase stable flow conditions

66

Holographic laser Doppler imaging of microvascular blood flow  

CERN Document Server

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency shifted reference beam, permits frequency selective imaging in the radiofrequency range. These Doppler images are acquired with an off axis Mach Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse method analysis of local first order optical fluctuation spectra at low radiofrequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1 to 10 millimeters per second range in vitro ...

Magnain, C; Boucneau, T; Simonutti, M; Ferezou, I; Rancillac, A; Vitalis, T; Sahel, J A; Paques, M; Atlan, M

2014-01-01

67

Methodology and reproducibility of bidirectional laser Doppler velocimetry  

International Nuclear Information System (INIS)

Bidirectional laser Doppler velocimetry in conjunction with monochromatic fundus photography allows non invasive measurement of retinal blood velocity. We have shown that it gives reproducible results in humans and experimental animals which agree well with those of the radioactively labelled microsphere technique. (author)

68

Dual beam translator for use in Laser Doppler anemometry  

Science.gov (United States)

A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

Brudnoy, David M. (Albany, NY)

1987-01-01

69

Coherent Doppler Laser Radar: Technology Development and Applications  

Science.gov (United States)

NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through headwind minimization. In addition to the airborne and space platforms, a coherent Doppler laser radar system in an unmanned aerial vehicle (UAV) could provide battlefield weather and target identification.

Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

2000-01-01

70

Video flowmeter  

Science.gov (United States)

A video flowmeter is described that is capable of specifying flow nature and pattern and, at the same time, the quantitative value of the rate of volumetric flow. An image of a determinable volumetric region within a fluid (10) containing entrained particles (12) is formed and positioned by a rod optic lens assembly (31) on the raster area of a low-light level television camera (20). The particles (12) are illuminated by light transmitted through a bundle of glass fibers (32) surrounding the rod optic lens assembly (31). Only particle images having speeds on the raster area below the raster line scanning speed may be used to form a video picture which is displayed on a video screen (40). The flowmeter is calibrated so that the locus of positions of origin of the video picture gives a determination of the volumetric flow rate of the fluid (10).

Lord, David E. (Livermore, CA); Carter, Gary W. (Livermore, CA); Petrini, Richard R. (Livermore, CA)

1983-01-01

71

Particle-fluid interaction corrections for flow measurements with a laser Doppler flowmeter  

Science.gov (United States)

A discussion is given of particle lags in mean flows, acoustic oscillations at single frequencies and in turbulent flows. Some simplified cases lead to exact solutions. For turbulent flows linearization of the equation of motion after assuming the fluid and particle streamlines coincide also leads to a solution. The results show that particle lags are a function of particle size and frequency of oscillation. Additional studies are necessary to evaluate the effect of turbulence when a major portion of the energy is concentrated in small eddies.

Berman, N. S.

1972-01-01

72

Influence of laser frequency noise on scanning Fabry-Perot interferometer based laser Doppler velocimetry  

Science.gov (United States)

In this work, we study the performance of a scanning Fabry-Perot interferometer based laser Doppler velocimeter (sFPILDV) and compare two candidate 1.5 um single-frequency laser sources for the system - a fiber laser (FL) and a semiconductor laser (SL). We describe a straightforward calibration procedure for the sFPI-LDV and investigate the effect of different degrees of laser frequency noise between the FL and the SL on the velocimeter's performance.

Rodrigo, Peter John; Pedersen, Christian

2014-03-01

73

Three-dimensional laser cooling at the Doppler limit  

CERN Document Server

Many predictions of the theory of Doppler cooling of 2-level atoms, notably the celebrated minimum achievable temperature $T_D=\\hbar \\Gamma/2 k_B$, have never been verified in a three-dimensional geometry. Here, we show that, despite their degenerate level structure, we can use Helium-4 atoms to achieve a situation in which these predictions can be verified. We make measurements of atomic temperatures, magneto-optical trap sizes, and the sensitivity of optical molasses to a power imbalance in the laser beams, finding excellent agreement with the Doppler theory. We show that the special properties of Helium, particularly its small mass and narrow transition linewidth, prevent effective sub-Doppler cooling with red-detuned optical molasses.

Chang, Rockson; Bouton, Quentin; Fang, Yami; Klafka, Tobias; Audo, Kevin; Aspect, Alain; Westbrook, Christoph I; Clément, David

2014-01-01

74

He II flowmetering  

International Nuclear Information System (INIS)

Flowmetering methods for He II are reviewed with emphasis on problems particular to this unique fluid. The flowmetering of He II is unusual because the fluid possesses a number of special properties: a high rate of heat conductivity, a low temperature (T < 2.2 K) and a high susceptibility to cavitation. Methods developed for metering He II flow include turbine flowmeters, venturis, fluidic flowmeters and flowmeters based on propagation of temperature or pressure pulses. (author)

75

Novel Doppler laser radar for diagnostics in fusion reactors  

International Nuclear Information System (INIS)

We describe the development of a novel Doppler laser radar (DOLAR) for remote measurement of flow velocity (0-10 m/s) and film thickness of liquid metal walls, currently being studied for their superior heat handling and self-healing characteristics. Small fluctuations in flow velocity(?mm/s) and flow thickness (?50 ?m) that may arise during plasma discharges can also be measured. The DOLAR is also designed for non intrusive mapping of features of plasma-facing solid surfaces with very high precision (?50 ?m). It can also measure the motion of structural components of a fusion reactor during plasma discharges and during plasma disruptions. The device utilizes frequency modulation laser radar principles for precision range measurements. Compensation of Doppler frequency shift is used to measure flow velocity. The DOLAR probe head is designed with acousto-optic and piezoelectric devices for operation in the harsh fusion environment

76

Remote intensity fluctuation measurements with a laser Doppler radar  

Science.gov (United States)

A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.

Kennedy, L. Z.; Bilbro, J. W.

1976-01-01

77

Catadioptric Optics for laser Doppler velocimeter applications  

Science.gov (United States)

In the design of a laser velocimeter system, attention must be given to the performance of the optical elements in their two principal tasks: focusing laser radiation into the probe volume, and collecting the scattered light. For large aperture applications, custom lens design and fabrication costs, long optical path requirements, and chromatic aberration (for two color operation) can be problematic. The adaptation of low cost Schmidt-Cassegrain astronomical telescopes to perform these laser beam manipulation and scattered light collection tasks is examined. A generic telescope design is analyzed using ray tracing and Gaussian beam propagation theory, and a simple modification procedure for converting from infinite to near unity conjugate ratio operation with image quality near the diffraction limit was identified. Modification requirements and performance are predicted for a range of geometries. Finally, a 200-mm-aperture telescope was modified for f/10 operation; performance data for this modified optic for both laser beam focusing and scattered light collection tasks agree well with predictions.

Dunagan, Stephen E.

1989-01-01

78

New signal analysis methods for laser doppler flowmetric recordings  

Science.gov (United States)

The laser Doppler flowmetry devices give a series of information like the blood flux and some statistical parameters, automatically estimated. There are also new important attempts based on the Fourier transform of the flow flux signal which gather more information from the laser Doppler flowmetry. The amplitude spectra estimated in these articles, exhibit a series of peaks corresponding to the cardiac variation of the blood flow and noise components of the flow flux signals, dependent on the state of the tooth. The aim of our investigations is to introduce new signal processing methods, based on wavelet continuous tranform, which express in a more sensitive manner the modifications of the flow flux signal with the state of the tooth, and to introduce new quantitative parameters, defined in a previous paper. These parameters express, in a more sensitive manner the modifications of the pulp flow flux signal in relation with the pulp tooth healt, and to introduce new quantitative parameters, defined in a previous paper. These parameters express, in a sensitive way the changes of the blood flux. For practical investigations we used a series of signals recorded with the aid of a Laser Doppler Blood Flow Monitoring device (Moor Instruments) and processed with the computer.

?g?nescu, G. E., Dr; Todea, Carmen

2014-01-01

79

A two color, dual beam backscattering laser Doppler velocimeter  

Science.gov (United States)

A laser Doppler velocimeter has been developed which uses two of the colors emitted from an argon ion laser for the simultaneous measurement of orthogonal velocities. Designed for use in a 2.13 m by 3.05 m wind tunnel, it is capable of traversing its focal volume across spatially unstable flows at scan speeds of up to 1.15 m/sec. Its optical layout and principles of operation are discussed and the data from a typical traversal of a trailing wing tip vortex are presented.

Grant, G. R.; Orloff, K. L.

1973-01-01

80

Two-color dual-beam backscatter laser Doppler velocimeter  

Science.gov (United States)

A laser Doppler velocimeter has been developed that uses two of the colors emitted from an argon-ion laser for the simultaneous measurement of orthogonal velocities. Designed for use in a 2.13- by 3.05-m wind tunnel, it is capable of traversing its focal volume across spatially unstable flows at scan speeds of up to 1.5 m/sec. Its optical layout and principles of operation are discussed, and the data from a typical traversal of a trailing wing-tip vortex are presented.

Grant, G. R.; Orloff, K. L.

1973-01-01

 
 
 
 
81

Reynolds stress measurements in cylindrical geometry using laser Doppler anemometry  

International Nuclear Information System (INIS)

Two-component one-point velocity correlation measurements in a cylindrical test section were performed using two-color Laser Doppler anemometry (LDA). In order to overcome the severe optical distortion effects in cylindrical geometry and achieve two-color spatial coincidence, two experimental methods were used: (1) attaching a rectangular, fluid-filled box to the pipe exterior; and (2) employing a laser-beam translating device. A description of these methods and some examples of coincidence data taken in pipe flow are presented

82

Generalized Laser Doppler Vibrometer noise maps  

Science.gov (United States)

In a previous work[1], the authors presented preliminary data showing how noise can be mapped as a function of beam focus and standoff distance. This analysis builds on the previous work, but presents a method of mapping laser Dopopler vibrometer (LDV) noise which can be broadly generalized. The apparatus used in the experiments is a Polytec OFV505 with a custom servo-actuated attachment to the focus ring, which is mounted to linear positioning stages to control standoff distance and dither location. A high resolution grid of measurement locations is generated to create a map of signal strength as a function of both standoff distance and "focus error" - a description of the degree to which the beam is defocused, expressed in terms of how the standoff would need to be adjusted in order to move the beam into focus. Using this approach, the particular optics of the LDV system are no longer directly a factor, as determining the relationship between the focus adjustment and standoff distance should be possible with any system. Further noise maps from experiments which dither the horizontal location of the measurement beam show how the signal field can change for nearby measurement locations on a rough surface and highlight the importance of averaging LDV measurements.

O'Malley, Patrick; Vignola, Joseph; Judge, John

2012-06-01

83

Some results obtained with laser Doppler and laser two focus anemometers in transonic steam flows  

Science.gov (United States)

A laser Doppler (LDA) and two types of laser transit velocimeters (LTV) have been used in steam. The facility comprises a two-dimensional tunnel and a small instructional turbine. For the LTVs only the backscatter alignment is applied, while both forward and backscatter configurations are examined for the LDA. In contrast to the LTV, the laser Doppler system requires seeding. A pneumatic atomizer produces water droplets upstream of the measuring station. A computer program accounts for droplet evaporation. This allows the ideal initial droplet diameter to be calculated. Using a particle-sizer the optimum atomizer is selected. It is explained how signals produced by big droplets are rejected. This is significantly simplified when the Doppler processor is interfaced with a multichannel analyzer. A comparison is made between the velocity distributions in a transonic steam turbine cascade obtained by the LDA processor and the LTVs where the signals are processed with either a multichannel analyzer or a correlator.

Decuypere, R.

84

Utilisation of laser Doppler and laser transit velocimeters in superheated, saturated and wet steam flows  

Science.gov (United States)

A laser Doppler (LDA) and two types of laser transit velocimeters (LTV) have been used in steam. The facility comprises a two-dimensional tunnel and a small instructional turbine. For the LTV's only the backscatter alignment is applied, while both forward and backscatter configurations are examined for the LDA. In contrast to the LTV, the laser Doppler system requires seeding. A pneumatic atomizer produces water droplets upstream of the measuring station. A computer program accounts for droplet evaporation. This allows the ideal initial droplet diameter to be calculated. Using a particle sizer the optimum atomizer is selected. It is explained how signals produced by big droplets are rejected. This is significantly simplified when the Doppler processor is interfaced with a multichannel analyzer. A comparison is made between the velocity distributions in a transonic steam turbine cascade obtained by the LDA processor and the LTV's where the signals are processed with either a multichannel analyzer or a correlator.

Decuypere, R.; Bosschaerts, W.

85

Radial pump impeller measurements using a laser Doppler velocimeter  

Science.gov (United States)

A shrouded fully transparent radial pump impeller with thin backswept blades has been tested using a laser Doppler velocimeter. Two components of the velocity were measured relative to the laboratory reference frame in a plane perpendicular to the axis of rotation. The velocity distribution is presented relative to the blades at different radii and different flow rates over the whole blade passage. The results show that the flow is essentially unsteady and, at low flow rate, highly influenced by viscous effects. A comparison between the experimental data and a potential flow theory shows good agreement at high flow rates.

Kannemans, H.

1980-03-01

86

Sub-Doppler modulation spectroscopy of potassium for laser stabilization  

International Nuclear Information System (INIS)

We study modulation spectroscopy of the potassium D2 transitions at 766.7 nm. The vapour pressure, controlled by heating a commercial reference cell, is first optimized using conventional saturated absorption spectroscopy. Heterodyne detection then yields sub-Doppler frequency discriminants suitable for stabilizing lasers in experiments with cold atoms. Comparisons are made between spectra obtained by direct modulation of the probe beam and those using modulation transfer from the pump via nonlinear mixing. Finally, suggestions are made for further optimization of the signals. (paper)

87

Sub-Doppler laser cooling and magnetic trapping of erbium  

CERN Document Server

We investigate cooling mechanisms in magneto-optically and magnetically trapped erbium. We find efficient sub-Doppler cooling in our trap, which can persist even in large magnetic fields due to the near degeneracy of two Lande g factors. Furthermore, a continuously loaded magnetic trap is demonstrated where we observe temperatures below 25 microkelvin. These favorable cooling and trapping properties suggest a number of scientific possibilities for rare-earth atomic physics, including narrow linewidth laser cooling and spectroscopy, unique collision studies, and degenerate bosonic and fermionic gases with long-range magnetic dipole coupling.

Berglund, Andrew J; McClelland, Jabez J

2008-01-01

88

Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO{sub 2} laser  

Energy Technology Data Exchange (ETDEWEB)

We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO{sub 2} laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

Lee, Teaghee; Choi, Jong Woon [Department of Information and Communication, Honam University, Seobong-dong 59-1, Gwansan-gu, Gwangju 506-714 (Korea, Republic of); Kim, Yong Pyung [College of Electronics and Information, Kyunghee University, 1 Seocheon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701 (Korea, Republic of)

2012-09-15

89

PC-integrated laser Doppler blood flow measurements in skin  

Science.gov (United States)

By irradiation of the skin with a diode laser the blood flow can be measured using the back scattered light. The majority of the back scattered light is scattered from fixed cells, but a small amount is scattered from moving erythrocytes and is Doppler shifted. The mixed light detected with a photodiode leads directly to a photocurrent proportional to the Doppler signal. A laser Doppler blood flow meter was developed, consisting of a PC-AT (66 MHz), a commercial A/D card (14 bit, 100 kHz) and a special head control card for two laser heads. The heads have a diameter of 35 mm and a height of 15 mm. The heads are fixed to the skin with tape. A DOS-Pascal software program provides the measurement, the calculation of a whole blood flow spectrum and shows the results on the screen with a time resolution of up to 50 Hz. The laser head is connected via 2 m cables with the head control card and contains a diode laser (5 mW, 670, 785 nm) a micro lens, two photodiodes and a pre-amplifier. On the head control card there is the current supply for the laser diodes, also the Doppler signals are band passed (400 Hz to 50 kHz), further amplified and fed into the A/D card. On the A/D card the analog signal is sampled with 100 kHz and digitized with 14 bit resolution. With 256 samples a frequency spectrum (128 channels, 0 - 50 kHz) is calculated by a FFT, but only the first 100 channels (0 - 39 kHz) are used to prevent ghosts. The measurements of the Doppler signal of the two laser heads need 5.2 ms and for all software calculations 15 ms are necessary. A quantitative recalculation of a velocity spectrum from the frequency spectrum is only possible if the velocity-, the irradiation-, and scattering-directions are known. In skin the small blood vessels have various directions and because of scattering in skin the irradiation of an erythrocyte can be assumed to be random. With this assumption of a random direction distribution a velocity spectrum can be calculated from the frequency spectrum. A flow spectrum is defined as the product of the velocity and the intensity at this velocity. The flow is defined as the integral over a given region of the flow spectrum. Four independent flow curves can be shown simultaneously on the screen and the frequency region for each flow can be set independently. The flows from low (1 - 3 mm/s) and high (7 - 9 mm/s) velocities show a different behavior and give the possibility to distinguish between the flow in the micro capillaries and larger vessels in the skin.

Doerschel, Klaus; Mueller, Gerhard J.

1996-05-01

90

Laser Doppler detection systems for gas velocity measurement.  

Science.gov (United States)

The velocity of gas flow has been remotely measured using a technique which involves the coherent detection of scattered laser radiation from small particles suspended in the fluid utilizing the doppler effect. Suitable instrumentation for the study of wind tunnel type and atmospheric flows are described. Mainly for reasons of spatial resolution, a function of the laser wavelength, the wind tunnel system utilizes an argon laser operating at 0.5 micro. The relaxed spatial resolution requirement of atmospheric applications allows the use of a carbon dioxide laser, which has superior performance at a wavelength of 10.6 micro, a deduction made from signal-to-noise ratio considerations. Theoretical design considerations are given which consider Mie scattering predictions, two-phase flow effects, photomixing fundamentals, laser selection, spatial resolution, and spectral broadening effects. Preliminary experimental investigations using the instrumentation are detailed. The velocity profile of the flow field generated by a 1.27-cm diam subsonic jet was investigated, and the result compared favorably with a hot wire investigation conducted in the same jet. Measurements of wind velocity at a range of 50 m have also shown the considerable promise of the atmospheric system. PMID:20076326

Huffaker, R M

1970-05-01

91

Holographic optical system for aberration corrections in laser Doppler velocimetry  

Science.gov (United States)

An optical system containing multifaceted holographic optical elements (HOEs) has been developed to correct for aberrations introduced by nonflat windows in laser Doppler velocimetry. The multifacet aberration correction approach makes it possible to record on one plate many sets of adjacent HOEs that address different measurement volume locations. By using 5-mm-diameter facets, it is practical to place 10-20 sets of holograms on one 10 x 12.5-cm plate, so that the procedure of moving the entire optical system to examine different locations may not be necessary. The holograms are recorded in dichromated gelatin and therefore are nonabsorptive and suitable for use with high-power argon laser beams. Low f-number optics coupled with a 90-percent efficient distortion-correcting hologram in the collection side of the system yield high optical efficiency.

Kim, R. C.; Case, S. K.; Schock, H. J.

1985-01-01

92

Particle analysis in the pulmonary tree by laser Doppler velocimetry  

Science.gov (United States)

Applications of two laser-based quasi-elastic light scattering instruments to the characterization of aerodynamic diameter, diffusion diameter, and electrostatic charge of respirable particles for estimating lung retention of inhaled particles are discussed. The methods provide means of real time, noninvasive in-situ measurements of the size and charge distributions of both inspired and expired particles, permitting quantitative determination of the lung retention of inhaled particles. The two instruments used are: 1) electrical single particle aerodynamic relaxation time (E-SPART) analyzer; and 2) photon correlator employing a dual-beam laser Doppler velocimeter. Both have advantages over the conventional optical particle counter in that they measure equivalent diameter and electrostatic charge independent of the optical scattering properties of the particles, while providing data on a single particle basis. Applications of these instruments in estimating health hazards from atmospheric pollutants and in evaluating the efficacy of therapeutic aerosols in treating diseases are briefly discussed.

Mazumder, Malay K.; Hiller, F. Charles

1987-03-01

93

Sympathetic skin vasoconstriction--further evaluation using laser Doppler techniques.  

Science.gov (United States)

The aim of this study was to quantify the reflex sympathetic vasoconstriction in skin at different depths. Twenty healthy subjects were studied. Finger skin blood flow was measured using laser Doppler perfusion imaging (LDPI) and laser Doppler perfusion monitoring (LDPM). In LDPM, a probe with fibres separated 0.25 mm (deep) and 0.14 mm (superficial) from the illuminating fibre was used. Local heating (40 degrees C) was achieved with a Peltier element, and reflex vasoconstriction induced by immersion of the contra-lateral hand and forearm for 3 min in water at 15 degrees C. The change in skin blood flow was measured and a vasoconstriction index (VAC: cooling/before cooling) calculated. VAC indices of LDPI, LDPM-0.25 and LDPM-0.14 were 0.60, 0.59 and 0.60, respectively. The two components of the LDPM perfusion value, blood cell velocity and concentration, were studied separately. Their contributions in LDPM-0.25 were roughly the same, whereas the velocity component dominated in LDPM-0.14, although their relative responses in the two channels were similar. We conclude that sympathetic skin vasoconstriction does not significantly differ in two compartments, as probed with fibres separated by 0.25 and 0.14 mm. Blood cell velocity is influenced in a proportional way, as is concentration. PMID:11380527

Holmlund, F; Freccero, C; Bornmyr, S; Castenfors, J; Johansson, A M; Nordquist, J; Sundkvist, G; Svensson, H; Wollmer, P

2001-05-01

94

Momentum transfer in laser-induced ablation of hard tissue measured by laser Doppler vibrometry  

Science.gov (United States)

A laser Doppler vibrometer was used in a pendulum experiment to measure the recoil momentum induced in hard tissue by pulsed infrared laser exposure. A Holmium:YAG laser was irradiated at bone and a superpulsed CO2 laser irradiated at dentin. Since the masses of the samples were known and the ablated masses were measured, this method allowed an indirect determination of the velocity of the ablated particles. In a second experiment performed with the CO2 laser the velocities of the ablated particles were measured directly by the time of flight detected by the laser beam of the vibrometer. The results of both methods are in good agreement; at a mean power of 0.5 Watt of the CO2 laser the velocity was 50 - 60 m/s increasing at higher mean powers.

Foth, Hans-Jochen; Barton, Thomas G.; Meyer, Dirk H.; Postel, Adriaen

1998-07-01

95

Measuring by laser Doppler vibrometry the recoil momentum of biological tissue under infrared laser ablation  

Science.gov (United States)

The recoil momentum of hard tissue induced by pulsed IR laser exposure was measured in a pendulum experiment using laser Doppler vibrometry. For the experiments bone was irradiated by holmium:YAG laser radiation and dentin by a superpulsed CO2 laser. Since the initial masses of the samples were known and the ablated masses were measured, this method allowed also an indirect determination of the velocity of the ablated particles. In a second experiment performed with the CO2 laser the velocities of the ablated particles were measured directly by the time of flight detected by the laser beam of the vibrometer. The technical realization as well as the limitations of the method is discussed; furthermore laser parameters are pointed out which induce critical acceleration risking serious damage to sensitive organs.

Barton, Thomas G.; Foth, Hans-Jochen; Meyer, Dirk H.; Postel, Adriaen

1998-06-01

96

Non-contact photoacoustic tomography with a laser Doppler vibrometer  

Science.gov (United States)

Most concurrent photoacoustic tomography systems are based on traditional ultrasound measurement regime, which requires the contact or acoustic coupling material between the biological tissue and the ultrasound transducer. This study investigates the feasibility of non-contact measurement of photacoustic signals generated inside biomedical tissues by observing the vibrations at the surface of the tissues with a commercial laser Doppler vibrometer. The vibrometer with 0- 2MHz measurement bandwidth and 5 MHz sampling frequency was integrated to a conventional rotational PAT data acquisition system. The data acquisition of the vibrometer was synchronized to the laser illumination from an Nd:YAG laser with output at 532nm. The laser energy was tuned to 17.5mJ per square centimeter. The PA signals were acquired at 120 angular locations uniformly distributed around the scanned objects. The frequency response of the measurement system was first calibrated. 2-inch-diamater cylindrical phantoms containing small rubber plates and biological tissues were afterwards imaged. The phantoms were made from 5% intralipid solution in 10% porcine gelatin to simulate the light scattering in biological tissue and to backscatter the measurement laser from the vibrometer. Time-domain backprojection method was used for the image reconstruction. Experiments with real-tissue phantoms show that with laser illumination of 17.5 mJ/cm2 at 532 nm, the non-contact photoacoustic (PA) imaging system with 15dB detection bandwidth of 2.5 MHz can resolve spherical optical inclusions with dimension of 500?m and multi-layered structure with optical contrast in strongly scattering medium. The experiment results prompt the potential implementation of the non-contact PAT to achieve "photoacoustic camera".

Xu, Guan; Wang, Cheng; Feng, Ting; Oliver, David E.; Wang, Xueding

2014-03-01

97

Series of calibration tests at national standard loops and industrial application experiences of new type flow-metering system by ultrasonic pulse-doppler profile-velocimetry  

International Nuclear Information System (INIS)

effect of deviated flow profile from expected ideal one. Series of calibration tests of UdFlow were conducted at the national standard loops in Mexico, CENAM (The Centro National de Metrologia) and in USA, NIST (National Institute of Standard and Technology) in order to evaluate the accuracy of the flowmeter. Four ultrasonic transducers are mounted on the surface of stainless steel piping circumferentially with the diameters of 100mm and 200mm to measure four velocity profiles. The calibration tests found a deviation better than 0.3% between the two devices in terms of the average of the values recorded by six rounds of each measurement. From the results of measurement conducted with Reynolds number varied, it was found that the overall average deviation between the two devices was better than 0.3%. (author)

98

Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry  

Science.gov (United States)

An experimental method for the determination of the flow-tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow-seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled in order to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diam and over the frequency range 100 Hz to 100 kHz. It was observed that unit-density spherical scatterers with diameters of 0.2 micron followed subsonic air turbulence frequency components up to 100 kHz with 98% fidelity.

Mazumder, M. K.; Kirsch, K. J.

1975-01-01

99

Short-time Fourier transform laser Doppler holography  

CERN Document Server

We report a demonstration of laser Doppler holography at a sustained acquisition rate of 250 Hz on a 1 Megapixel complementary metal-oxide-semiconductor (CMOS) sensor array and image display at 10 Hz frame rate. The holograms are optically acquired in off-axis configuration, with a frequency-shifted reference beam. Wide-field imaging of optical fluctuations in a 250 Hz frequency band is achieved by turning time-domain samplings to the dual domain via short-time temporal Fourier transformation. The measurement band can be positioned freely within the low radio-frequency spectrum by tuning the frequency of the reference beam in real-time. Video-rate image rendering is achieved by streamline image processing with commodity computer graphics hardware. This experimental scheme is validated by a non-contact vibrometry experiment.

Atlan, Michael

2012-01-01

100

Unsteady flow in rotating drums using laser Doppler velocimetry  

Science.gov (United States)

Non-destructive measurements by laser Doppler velocimetry is employed to study unsteady flow in a hollow drum filled with liquid. The drum is suddenly accelerated from rest or is suddenly decelerated from a steady rotation to rest. Pure water and glycerin-water mixtures are used as the test liquid in which polyethylenelatex particles are mixed as the light scattering tracer. The boundary layer formation, the time history of velocity, momentum and kinetic energy of the liquid, the wall-to-fluid force transfer, and the transient response time are determined. Also determined are the effects of side walls and fluid viscosity on the transient flow response. Of importance is the disclosure of Ekman layer instability near the inner radial wall of the test drum. It is actuated by the centripetal acceleration-induced buoyancy force.

Kawashima, G.; Yang, W.-J.

1988-01-01

 
 
 
 
101

High accuracy fuel flowmeter  

Science.gov (United States)

All three flowmeter concepts (vortex, dual turbine, and angular momentum) were subjected to experimental and analytical investigation to determine the potential portotype performance. The three concepts were subjected to a comprehensive rating. Eight parameters of performance were evaluated on a zero-to-ten scale, weighted, and summed. The relative ratings of the vortex, dual turbine, and angular momentum flowmeters are 0.71, 1.00, and 0.95, respectively. The dual turbine flowmeter concept was selected as the primary candidate and the angular momentum flowmeter as the secondary candidate for prototype development and evaluation.

1986-01-01

102

Remote measurement utilizing NASA's scanning laser Doppler systems. Volume 1. Laser Doppler wake vortex tracking at Kennedy Airport  

Science.gov (United States)

Test operations of the Scanning Laser Doppler System (SLDS) at Kennedy International Airport (KIA) during August 1974 through June 1975 are reported. A total of 1,619 data runs was recorded with a totally operational system during normal landing operations at KIA. In addition, 53 data runs were made during cooperative flybys with the C880 for a grand total of 1672 recorded vortex tracks. Test crews were in attendance at KIA for 31 weeks, of which 25 weeks were considered operational and the other six were packing, unpacking, setup and check out. Although average activity equates to 67 recorded landing operations per week, two periods of complete runway inactivity spanned 20 days and 13 days, respectively. The operation frequency therefore averaged about 88 operations per week.

Krause, M. C.; Wilson, D. J.; Howle, R. E.; Edwards, B. B.; Craven, C. E.; Jetton, J. L.

1976-01-01

103

Laser Doppler vibrometry with a single-frequency microchip green laser  

International Nuclear Information System (INIS)

We have developed a laser vibrometer based on an Nd:YVO4/YVO4/KTP monolithic single-frequency green laser operating at 532 nm, with a narrow linewidth of radiation. Two configurations of the laser Doppler vibrometer have been investigated—with the so-called single- and double-frequency Bragg shifts. Measurement of heterodyne signals as a mixing result of scattered and reference beams has been carried out. In both configurations we have obtained signals with a high S/N ratio of >30 dB with resolution bandwidth = 200 kHz for a vibrometer output power of 3 mW. In our opinion, stable single-frequency solid-state green lasers provide new opportunities for the development of miniature laser vibrometry

104

Laser Doppler vibrometry with a single-frequency microchip green laser  

Science.gov (United States)

We have developed a laser vibrometer based on an Nd:YVO4/YVO4/KTP monolithic single-frequency green laser operating at 532 nm, with a narrow linewidth of radiation. Two configurations of the laser Doppler vibrometer have been investigated—with the so-called single- and double-frequency Bragg shifts. Measurement of heterodyne signals as a mixing result of scattered and reference beams has been carried out. In both configurations we have obtained signals with a high S/N ratio of >30 dB with resolution bandwidth = 200 kHz for a vibrometer output power of 3 mW. In our opinion, stable single-frequency solid-state green lasers provide new opportunities for the development of miniature laser vibrometry.

Anto?czak, Arkadiusz J.; Kozio?, Pawe?; Sotor, Jaros?aw Z.; Kaczmarek, Pawe? R.; Abramski, Krzysztof M.

2011-11-01

105

Microcomputer-based laser Doppler velocimeter in marine biology  

Science.gov (United States)

A laser doppler velocimeter (LDV) has been designed and constructed for use in measuring ocean water flow velocity in the immediate vicinity of marine organisms anchored inside a water tunnel. The principal innovation reported here is the use of a microprocessor to produce an ''intelligent'' instrument which automatically calculates and displays the flow velocity. The resulting electronics design represents a considerable simplification over existing instruments which generally require the use of a separate autocorrelator and/or multi-channel analyzer (MCA) plus an external minicomputer. The LDV configuration employed is a crossed-beam design using a 2-mW He-Ne laser and inexpensive optics. A 48-channel 1-bit clipped autocorrelation function is implemented using a modified TTL design reported previously by Chen and co-workers. A Motorola 6800 micromodule updates the contents of each channel by direct memory access and displays the resulting correlogram on a CRT monitor. The velocity is periodically calculated (±5%) and displayed by LED digits.

Paul, Mark; Nicoli, D. F.

1980-09-01

106

Photonic Doppler velocimetry of laser-ablated ultrathin metals.  

Science.gov (United States)

Obtaining velocity information from the interaction of a laser pulse on a metal layer provides insight into the rapid dynamics of material removal and plasma plume physics during ablation. A traditional approach involves using a velocity interferometer system for any reflector (VISAR) on a reflective metal surface. However, when the target is a thin metal layer, the cohesion of the surface is quickly lost resulting in a large spread of particle velocities that cannot be easily resolved by VISAR. This is due to material ejection"confusing" the VISAR measurement surface, effectively washing out the spatial fringe visibility in the VISAR interferometer. A new heterodyne-based optical velocimeter method is the photonic Doppler velocimeter (PDV). Because PDV tracks motion in a frequency encoded temporal electro-optical signal, velocity information is preserved and allows for multiple velocity components to be recorded simultaneously. The challenge lies in extracting PDV velocity information at short (nanosecond) laser ablation time scales with rapidly varying heterodyne beats by using electronic, optical, and analytical techniques to recover the velocity information from a fleeting signal. Here we show how we have been able to obtain velocity information on the nanosecond time scale and are able to compare it to hydrodynamic simulations. Also, we examine refinements to our PDV system by increasing the bandwidth, utilizing different probes, and sampling different analysis techniques. PMID:17503901

Valenzuela, A R; Rodriguez, G; Clarke, S A; Thomas, K A

2007-01-01

107

Photonic Doppler velocimetry of laser-ablated ultrathin metals  

International Nuclear Information System (INIS)

Obtaining velocity information from the interaction of a laser pulse on a metal layer provides insight into the rapid dynamics of material removal and plasma plume physics during ablation. A traditional approach involves using a velocity interferometer system for any reflector (VISAR) on a reflective metal surface. However, when the target is a thin metal layer, the cohesion of the surface is quickly lost resulting in a large spread of particle velocities that cannot be easily resolved by VISAR. This is due to material ejection 'confusing' the VISAR measurement surface, effectively washing out the spatial fringe visibility in the VISAR interferometer. A new heterodyne-based optical velocimeter method is the photonic Doppler velocimeter (PDV). Because PDV tracks motion in a frequency encoded temporal electro-optical signal, velocity information is preserved and allows for multiple velocity components to be recorded simultaneously. The challenge lies in extracting PDV velocity information at short (nanosecond) laser ablation time scales with rapidly varying heterodyne beats by using electronic, optical, and analytical techniques to recover the velocity information from a fleeting signal. Here we show how we have been able to obtain velocity information on the nanosecond time scale and are able to compare it to hydrodynamic simulations. Also, we examine refinements to our PDV system by increasing the bandwidth, utilizing different probes, and sampling different analysis t probes, and sampling different analysis techniques

108

Diagnostic accuracy of laser Doppler flowmetry versus strain gauge plethysmography for segmental pressure measurement  

DEFF Research Database (Denmark)

To assess the diagnostic accuracy of laser Doppler flowmetry (LDF) with mercury-in-silastic strain gauge plethysmography (SGP) as a reference test for measuring the toe and ankle pressures in patients with known or suspected peripheral arterial disease (PAD).

HØyer, Christian; Sandermann, Jes

2013-01-01

109

Nonintrusive dynamic flowmeter  

Science.gov (United States)

Description of some of the design and performance characteristics of an ultrasonic dynamic flowmeter which combines nonintrusiveness, fast response, high accuracy, and high resolution and is intended for use with cryogenic liquids and water. The flowmeter measures to 1% accuracy the dynamic as well as the steady flow velocity averaged over the pipe area.

Pedersen, N. E.; Lynnworth, L. C.

1973-01-01

110

Differential oil flowmeter  

Science.gov (United States)

Difference in oil flow volume through two mechanical flowmeters is converted to analog signal by simple inexpensive circuit. Circuit can be implemented with only minor changes to conventional oil flowmeters and used to measure fuel consumed by oil fired furnace or water heater.

Powers, W. T.

1979-01-01

111

Remote measurement of the transverse wind velocity component using a laser Doppler velocimeter  

Science.gov (United States)

The wind speed transverse to the line-of-sight of a laser Doppler radar has been measured using the intensity fluctuations of the returned signal. These measurements were made at a range of 100 m with a CO2 CW laser Doppler velocimeter, which was simultaneously performing its design function of determining the radial velocity component. The transverse component measurements are compared with those obtained using a u, v, w Gill propeller anemometer.

Kennedy, L. Z.; Bilbro, J. W.

1979-01-01

112

Routine use of laser Doppler flowmetry for monitoring autologous tissue transplants.  

Science.gov (United States)

This is a report of a prospective study in which 41 consecutive autologous tissue transplants were monitored using the Laserflo BPM model 403 laser Doppler monitor (TSI Inc., St. Paul, MN). Flaps were monitored both intraoperatively and postoperatively, and clinical flap monitoring was compared with laser Doppler monitoring. Twenty-nine flaps had no problems as indicated by clinical or Doppler measurement. Twelve flaps underwent 13 reexplorations; one flap was explored twice. Five venous and five arterial anastomoses were corrected, with complete survival of the flaps. Three hematomas were evacuated. Two of these flaps failed. There were no instances where the laser Doppler indicated a problem with flap viability that subsequently did not merit reexploration. There were no instances of flap failure undetected by the laser Doppler. In comparison to the clinical monitoring, laser Doppler monitoring was more rapid and more precise in identifying problems with the flap. The use of this monitor has improved our salvage rate for flap reexploration from 50 to 85% and has provided a more objective standard for both nurses and physicians to evaluate flaps in the perioperative period. PMID:3069034

Jenkins, S; Sepka, R; Barwick, W J

1988-11-01

113

Doppler shift of a laser pulse beam scattered by a rotating cone and cylinder  

Science.gov (United States)

Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense.

Wang, Bao-Ping; Wang, Ming-Jun; Wu, Zhen-Sen; Li, Ying-Le; Xiang, Ning-Jing

2014-05-01

114

Dead time effects in laser Doppler anemometry measurements  

DEFF Research Database (Denmark)

We present velocity power spectra computed by the so-called direct method from burst-type laser Doppler anemometer (LDA) data, both measured in a turbulent round jet and generated in a computer. Using today’s powerful computers, we have been able to study more properties of the computed spectra than was previously possible, and we noted some unexpected features of the spectra that we now attribute to the unavoidable influence of a finite measurement volume (MV). The most prominent effect, which initially triggered these studies, was the appearance of damped oscillations in the higher frequency range, starting around the cutoff frequency due to the finite size of the MV. Using computer-generated data mimicking the LDA data, these effects have previously been shown to appear due to the effect of dead time, i.e., the finite time during which the system is not able to acquire new measurements. These dead times can be traced back to the fact that the burst-mode LDA cannot measure more than one signal burst at a time. Since the dead time is approximately equal to the residence time for a particle traversing a measurement volume, we are dealing with widely varying dead times, which, however, are assumed to be measured for each data point. In addition, the detector and processor used in the current study introduce a certain amount of fixed processing and data transfer times, which further contribute to the distortion of the computed spectrum. However, we show an excellent agreement between a measured spectrum and our modeled LDA data, thereby confirming the validity of our model for the LDA burst processor.

Velte, Clara Marika; Buchhave, Preben

2014-01-01

115

Low resource processing algorithms for laser Doppler blood flow imaging.  

Science.gov (United States)

The emergence of full field laser Doppler blood flow imaging systems based on CMOS camera technology means that a large amount of data from each pixel in the image needs to be processed rapidly and system resources need to be used efficiently. Conventional processing algorithms that are utilized in single point or scanning systems are therefore not an ideal solution as they will consume too much system resource. Two processing algorithms that address this problem are described and efficiently implemented in a field programmable gate array. The algorithms are simple enough to use low system resource but effective enough to produce accurate flow measurements. This enables the processing unit to be integrated entirely in an embedded system, such as in an application-specific integrated circuit. The first algorithm uses a short Fourier transformation length (typically 8) but averages the output multiple times (typically 128). The second method utilizes an infinite impulse response filter with a low number of filter coefficients that operates in the time domain and has a frequency-weighted response. The algorithms compare favorably with the reference standard 1024 point fast Fourier transform in terms of both resource usage and accuracy. The number of data words per pixel that need to be stored for the algorithms is 1024 for the reference standard, 8 for the short length Fourier transform algorithm and 5 for the algorithm based on the infinite impulse response filter. Compared to the reference standard the error in the flow calculation is 1.3% for the short length Fourier transform algorithm and 0.7% for the algorithm based on the infinite impulse response filter. PMID:21316289

Nguyen, Hoang C; Hayes-Gill, Barrie R; Zhu, Yiqun; Crowe, John A; He, Diwei; Morgan, Stephen P

2011-07-01

116

Pipe flow measurements of turbulence and ambiguity using laser-Doppler velocimetry  

Science.gov (United States)

The laser-Doppler ambiguities predicted by George and Lumley (1973) have been verified experimentally for turbulent pipe flows. Experiments were performed at Reynolds numbers from 5000 to 15,000 at the center line and near the wall. Ambiguity levels were measured from power spectral densities of FM demodulated laser signals and were compared with calculations based on the theory. The turbulent spectra for these water flows after accounting for the ambiguity were equivalent to hot-film measurements at similar Reynolds numbers. The feasibility of laser-Doppler measurements very close to the wall in shear flows is demonstrated.

Berman, N. S.; Dunning, J. W.

1973-01-01

117

Observation of sub-Doppler Laser Induced Nuclear Orientation of 85mRb  

International Nuclear Information System (INIS)

This paper reports on the first observation of sub-Doppler resolved gamma anisotropy produced by Laser Induced Nuclear Orientation (LINO). The anisotropy was produced by laser optical pumping the Dl transition of the 1?s 85mRb isomer. Sub-Doppler LINO is uniquely suited for resolving closely spaced hyperfine structure (hfs) of very shortlived isomers, whose lifetimes are between 50 nanoseconds and 1 milli-second. In addition, sub-Doppler LINO allows more precise measurements of hf splittings to be made. For example, this leads to more accurate measurements of nuclear magnetic dipole and electric quadrupole moments, as well as isomer shifts. LINO uses laser optical pumping to produce electronic alignment. This is transferred to the excited nucleus via the hyperfine interaction. When the oriented nuclei decay, anisotropy is observed in the spatial distribution of the emitted gamma rays. The hfs of the isomer is determined by monitoring the anisotropy as a function of laser detuning

118

Low noise electromagnetic flowmeter  

Science.gov (United States)

Parasitic hum is removed by using an isophase magnetic field created within flowmeter and an enclosure which prevents leakage of flux field. Method prevents contamination of flow conduit and eliminates zero point drift.

Cushing, V. J.

1972-01-01

119

Flowmeter for Clear Fluids  

Science.gov (United States)

Electronic flowmeter measures flow rate of clear or translucent fluids. Instrument produces electrical signal proportional to volume of fluid flowing through it per unit time. Optoelectronic instrument generates electrical signal proportional to fluid-flow rate.

White, P. R.; Mcintosh, W. R.

1986-01-01

120

The Vortex Flowmeter  

Science.gov (United States)

This Web site features a series of animations showing the operation of a vortex flowmeter that is used to measure flow in a process control system. Besides defining a vortex flowmeter, a Flash animation shows how it causes vortices around a blunt object obstructing the flow. A sine wave flow is created depending upon the flow velocity. After viewing several pages, a brief two question quiz is given with self-correcting answers.

2009-08-03

 
 
 
 
121

Nuclear magnetic resonance flowmeters  

International Nuclear Information System (INIS)

Designs and operation of contectless flowmeters based on nuclear magnetic resonance presenting simultaneous information on composition, viscosity and other liquid medium parameters are considered. Special attention is paid to the theory and physical nature of the processes occurring in initial converters and to estimation and means of reducing systematic and random errors. Comparative evaluation of all native and foreign flowmeters is made and fields of their application are pointed out

122

Laser Doppler holographic microscopy in transmission: application to fish embryo imaging  

CERN Document Server

We have extended Laser Doppler holographic microscopy to transmission geometry. The technique is validated with living fish embryos imaged by a modified upright bio-microcope. By varying the frequency of the holographic reference beam, and the combination of frames used to calculate the hologram, multimodal imaging has been performed. Doppler images of the blood vessels for different Doppler shifts, images where the flow direction is coded in RGB colors or movies showing blood cells individual motion have been obtained as well. The ability to select the Fourier space zone that is used to calculate the signal, makes the method quantitative.

Verrier, Nicolas; Gross, Michel

2014-01-01

123

A coherent laser Doppler wind profiler for the active control of wind turbines  

Science.gov (United States)

A low cost design concept for Fibre-based Coherent Laser Doppler Wind Profiler is presented for supporting an active pitch control of Wind Turbines (WTs). The system is based on a 1.5?m Continuous-Wave (CW) semiconductor laser source plus an erbium-doped fibre amplifier (EDFA) with an output power of 1W. A coherent detection method is used for Doppler frequency measurement. In addition, a concept of wind turbine predictive pitch control system is proposed for reducing the damage caused by wind turbulence. A mathematical simulation and the experimental result based on a lab setup are presented to show the calibration of such a system.

Shinohara, L.; Bogatscher, S.; Heussner, N.; Umesh-Babu, H.; Brunet, M.; Stork, W.

2012-03-01

124

Calibration technique for electromagnetic flowmeters  

Science.gov (United States)

Thermal calorimetric method is used to calibrate electromagnetic flowmeters for liquid alkali metals. The electromagnetic flowmeter is placed in the liquid metal flow system in series with a thermal calorimeter. Therefore, the calculated flow rate through the calorimeter can be compared directly with the respective electromagnetic flowmeter reading.

Sawochka, S. G.

1967-01-01

125

Fluid Mechanics of Borehole Flowmeters  

Science.gov (United States)

The sensitivity of an electromagnetic flowmeter to flow in a borehole is dependent on flow entering the well above the entrance of the flowmeter. This dependence influences the calibration of flowmeters that are freely hanging in a borehole or use a centralizer, but not flowmeters using a skirt or packer to force the entire wellbore flow through the flowmeter. A mathematical model based on conservation of momentum has been developed to simulate the flow around and through the flowmeter. The model has been numerically implemented in an axis-symmetric version of MODFLOW-2000. The numerical model has been calibrated using data from a laboratory simulator of flow to a 4 inch ID screened well in a highly-permeable homogeneous aquifer. The influence of inflow above the entrance is clearly evident in the laboratory data which mimics data acquired at the Boise Hydrogeophysical Site. The most dramatic influence occurs near an unperforated region, where two sections of the screen are connected. The laboratory data reveal that the flow through the flowmeter decreases as the tool moves upward into the region, even though total flow through the wellbore at the entrance of the flowmeter is increasing. Then, as the entrance of the flowmeter passes through the unperforated region, flow through the flowmeter increases despite constant total flow in the unperforated region. The ratio of flow through the flowmeter to flow through the borehole is a non-linear function of absolute flow rate and flow entering the screen along the sides of the tool. The ratio is too complex to be completely ascertained from physical calibration of the flowmeter. A numerical model is needed. Interpretation of flowmeter measurements without considering dynamic calibration can be misleading. We use PEST to estimate hydraulic conductivity in a layered aquifer from the combined flowmeter and aquifer model using axis-symmetric MODFLOW. A parameter estimation program such as PEST or UCODE is required because each flowmeter measurement position requires a separate MODFLOW simulation.

Clemo, T.; Barrash, W.; Johnson, T. C.

2005-12-01

126

Sidetone generator flowmeter  

Science.gov (United States)

A flowmeter is provided which uses the sidetones generated in a cavity formed in the wall of a flowpipe or the like in response to fluid flowing past the cavity to provide a measure of the flow velocity of that fluid. The dimensions of the cavity are such as to provide a dominant vibratory frequency which is sensed by a pressure sensor. The flowmeter is adapted for use for a range of frequencies in which the Strouhal number is constant and under these conditions the vibratory frequency is directly related to the flow rate. The tone generator cavity and pressure transducer form a unit which is connected in-line in the flowpipe.

Fritz, Robert J. (Schenectady, NY)

1986-01-01

127

He-Ne laser effects on blood microcirculation. An in vivo study through laser doppler flowmetry  

International Nuclear Information System (INIS)

Blood microcirculation performs an important function in tissue repair process, as well as in pain control, allowing for greater oxygenation of the tissues and the accelerated expulsion of metabolic products, that may be contributing to pain. Low Intensity Laser Therapy (LILT) is widely used to promote healing, and there is an assumption that it is mechanism of action may be due to an enhancement of blood supply. The purpose of this study was to evaluate, using laser Doppler flowmetry (LDF), the stated effects caused by radiation emitted by a He-Ne laser (?=632.8 nm) on blood microcirculation during tissue repair. To this end, 15 male mice were selected and received a liquid nitrogen provoked lesion, above the dorsal region, and blood flow was measured periodically, during 21 days. Due to radiation emission by the LDF equipment, a control group was established to evaluate possible effects caused by this radiation on microcirculation. To evaluate the He-Ne laser effects, a 1.15 J/cm2 dose was utilized, with an intensity of 6 mW/cm2. The results obtained demonstrate flow alterations, provoked by the lesion, and subsequent inflammatory response. There was no statistical difference between the studied groups. As per the analysis of the results there is no immediate effect due the radiation emitted by a He Ne laser on microcirculation, although a percentage increase was observed in day 7 on medium blood flow rate in irradiated specimens. New studies are necessary to validate the use of this wavelength, in order to promote beneficial alterations in blood supply in radiated areas. (author)

128

Application of laser Doppler velocimeter to velocity measurement of charged dust particles in high electric field  

International Nuclear Information System (INIS)

As a preliminary study for the collection process of dust particles in an electrostatic precipitator, a laser Doppler velocimeter with high spatial resolution and high accuracy was used to measure the moving velocity of small dust particles charged in a high electric field. For an optical system of the velocimeter, the differential type was adopted. To achieve the high sampling rate, the period-measuring system was used for obtaining the velocity data from Doppler beat signals. By means of the laser Doppler velocimeter constructed here, accurate measurements of the moving velocity and direction of dust particles as a function of the applied electrode voltage and polarity were performed over a sectional plane of the model electrostatic precipitator. The experimental results may be useful for revealing the collection process of dust particles in the high electric field and, therefore, for the design of the electrostatic precipitator. (orig.)

129

Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions  

CERN Document Server

Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a star-like geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S_{1/2}->5P_{3/2}->6S_{1/2}->nP in Rb atoms have shown that compared to the one- and two-photon laser excitation this approach provides much narrower line width and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

Ryabtsev, I I; Tretyakov, D B; Entin, V M; Yakshina, E A

2011-01-01

130

Measurement of two-component flow using ultrasonic flowmeters  

Science.gov (United States)

Calibration of transit-time and Doppler ultrasonic flowmeters under two-component flow conditions has been conducted on 400 mm (16-in.) pipe. Testing covered total flows of 0.19 to 1.89 m(exp 3)/s (3000 to 30,000 gpm) and void fractions up to 40 percent. Both flowmeter types accurately measured total volumetric flow over a portion of their ranges. Pipe average void fraction, based on a three-beam gamma densitometer, was used to determine water component flow under stratified flow conditions, with similar results.

Whitehouse, J. C.; Eghbali, D. A.; Flitton, V. E.; Anderson, D. G.

131

Accuracy of flowmeters measuring horizontal groundwater flow in an unconsolidated aquifer simulator.  

Science.gov (United States)

Borehole flowmeters that measure horizontal flow velocity and direction of groundwater flow are being increasingly applied to a wide variety of environmental problems. This study was carried out to evaluate the measurement accuracy of several types of flowmeters in an unconsolidated aquifer simulator. Flowmeter response to hydraulic gradient, aquifer properties, and well-screen construction was measured during 2003 and 2005 at the U.S. Geological Survey Hydrologic Instrumentation Facility in Bay St. Louis, Mississippi. The flowmeters tested included a commercially available heat-pulse flowmeter, an acoustic Doppler flowmeter, a scanning colloidal borescope flowmeter, and a fluid-conductivity logging system. Results of the study indicated that at least one flowmeter was capable of measuring borehole flow velocity and direction in most simulated conditions. The mean error in direction measurements ranged from 15.1 degrees to 23.5 degrees and the directional accuracy of all tested flowmeters improved with increasing hydraulic gradient. The range of Darcy velocities examined in this study ranged 4.3 to 155 ft/d. For many plots comparing the simulated and measured Darcy velocity, the squared correlation coefficient (r2) exceeded 0.92. The accuracy of velocity measurements varied with well construction and velocity magnitude. The use of horizontal flowmeters in environmental studies appears promising but applications may require more than one type of flowmeter to span the range of conditions encountered in the field. Interpreting flowmeter data from field settings may be complicated by geologic heterogeneity, preferential flow, vertical flow, constricted screen openings, and nonoptimal screen orientation.

Bayless, E. R.; Mandell, Wayne A.; Ursic, James R.

2011-01-01

132

Simultaneous multivelocity component laser Doppler velocimetry using one digital frequency processor  

Science.gov (United States)

Digital frequency processing used in conjunction with optical frequency shifting is an ideal way to achieve simultaneous multivelocity component measurements in laser Doppler velocimetry. This becomes obvious once realized that multivelocity component information at different frequency offsets can be obtained directly from the composite frequency spectrum of a single-channel digital frequency processor. The approach has numerous advantages over the very popular approach of using a different laser wavelength, photodetector, and signal processor for each velocity component.

Johnson, D. A.

1990-01-01

133

Doppler Ultrasound Guided-Endovenous Laser Treatment for Superficial Venous Valvular Insufficiency  

International Nuclear Information System (INIS)

Endovenous laser treatment (EVL T) is a new procedure for the treatment of varicose ill, which is done under Eco-Doppler guide being minimum invasive, with an easy, quickly, ambulatory and without incapacity technique, with success results between 95 and 97% according to the literature available, comparable traditional technique

134

Laser Doppler measurements of turbulent parameters in different multiple-propeller systems  

Energy Technology Data Exchange (ETDEWEB)

Using laser Doppler anemometry measurements in the r-y plane, two different vessels equipped with two downward pumping propeller were studied. In the turbulent flow, the integral flow, the integral scales, the Taylor microscales, and the Kolmogorov microscale were determined. The authors' comparison with the literature shows that this combination of propellers produces larger eddies than a Rushton turbine. (orig.)

Baudou, C.; Xuereb, C.; Costes, J.; Bertrand, J. [Centre National de la Recherche Scientifique, 31 - Toulouse (France). Inst. du Genie Chimique

2000-03-01

135

The e-Beam Sustained Laser Technology for Space-based Doppler Wind Lidar  

Science.gov (United States)

An overview is presented of GEC Avionics activities relating to the Spaceborne Doppler Wind Lidar. In particular, the results of design studies into the use of an e-beam sustained CO2 laser for spaceborne applications, and experimental work on a test bed system are discussed.

Brown, M. J.; Holman, W.; Robinson, R. J.; Schwarzenberger, P. M.; Smith, I. M.; Wallace, S.; Harris, M. R.; Willetts, D. V.; Kurzius, S. C.

1992-01-01

136

Vibration characteristics of aluminum material and its influences on laser Doppler voice acquisition  

Science.gov (United States)

Laser Doppler technology is widely used in precision vibration measurement such as voice acquisition. The fundamental of voice acquisition is to detect the vibration of targets induced by sound wave using a Laser Doppler voice acquisition system, and then demodulate the voice signal from interference signal. Therefore the target's vibration characteristics will be the principal factor influencing the effect of voice acquisition. In this paper, we focus on the plane structure's vibration characteristics caused by voice. There are mainly two parts in this paper, simulation and experimental verify. In simulation, the finite element method is used. The Finite Element Analysis method is widely used in material properties analysis, dynamic analysis, and acoustic analysis. Through finite element analysis method, the plane structure models of thick smooth aluminum are established by ANSYS. Then the frequency responses of different constraints are compared. The Laser Doppler voice acquisition system is applied to test and verify the simulation results. The response characteristics of aluminum board under different excitation frequency are measured. The experimental results and simulation results are compared to verify the correctness and reasonableness of simulation. At the same time, this provides theoretical guidance for Laser Doppler voice acquisition system to choose targets and improve voice acquisition performance.

Zhang, Yu-ze; Li, Li-yan; Tong, You-wan; Zeng, Hua-lin; Zhou, Yan

2013-09-01

137

Experimental data base of turbulent flow in rod bundles using laser doppler velocimeter  

International Nuclear Information System (INIS)

This report presents in detail the hydraulic characteristics measurements in subchannels of rod bundles using one-component LDV (Laser Doppler Velocimeter). In particular, this report presents the figures and tabulations of the resulting data. The detailed explanations about these results are shown in references publicated or presented at the conference. 4 kinds of experimental work were performed so far. (Author)

138

Multipoint laser Doppler vibrometry using holographic optical elements and a CMOS digital camera  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A laser Doppler vibrometer (LDV) is described in which holographic optical elements are used to provide the interferometer reference and object illumination beams. A complementary metal-oxide semiconductor camera, incorporating a digital signal processor, is used to carry out real-time signal processing of the interferometer output to allow multipoint LDV to be implemented.

Connelly, Michael J.; Szecowka, Przemyslaw M.; Jallapuram, Raghavendra; Martin, Suzanne; Toal, Vincent; Whelan, Maurice P.

2008-01-01

139

Flow Field Results of the Cambridge Stratified Swirl Burner Using Laser Doppler Anemometer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A series of flow fields generated by a turbulent methane/air stratified swirl burner are investigated using laser Doppler anemometer (LDA) to obtain the velocities in axial, radial and tangential directions. All mean and RMS of the LDA velocity results are supplied along with a report describing the experimental methodology, data processing routines and the data format.

Zhou, Ruigang; Sweeney, Mark; Hochgreb, Simone

2012-01-01

140

Doppler wind lidar using a MOPA semiconductor laser at stable single-frequency operation  

DEFF Research Database (Denmark)

A compact master-oscillator power-amplifier semiconductor laser (MOPA-SL) is a good candidate for a coherent light source (operating at 1550 nm) in a Doppler wind Lidar. The MOPA-SL requires two injection currents: Idfb for the distributed-feedback (DFB) laser section (master oscillator) and Iamp for the tapered amplifier section. The specified maximum current values are 0.7 A and 4.0 A for Idfb and Iamp. Although the MOPA-SL has been proven capable of producing single-frequency CW output beam, stable operation at this spectral condition has also been known to highly depend on the drive currents to the laser. This was done by observing the spectral characteristic of the laser using an optical spectrum at different drive current combinations. When using the laser for a Doppler wind Lidar application, a combination of (Idfb, Iamp) which is close to the center of an identified stable single-frequency regime is used. The current settings for the laser result in a highly stable Lidar as shown by a 5-day long continuous measurement of the Doppler shift produced by a constantly rotating diffusely reflecting target.

Rodrigo, Peter John; Pedersen, Christian

2009-01-01

 
 
 
 
141

Signal processing considerations for low signal to noise ratio laser Doppler and phase Doppler signals  

Science.gov (United States)

The relative performance of current methods used for estimating the phase and the frequency in LDV and phase Doppler applications in low signal to noise ratio conditions is analyzed. These methods include the Fourier analysis and the correlation techniques. Three methods that use the correlation function for frequency and phase estimations are evaluated in terms of accuracy and speed of processing. These methods include: (1) the frequency estimation using zero crossings counting of the auto-correlation function, (2) the Blackman-Tukey method, and (3) the AutoRegressive method (AR). The relative performance of these methods is evaluated and compared with the Fourier analysis method which provides the optimum performance in terms of the Maximum Likelihood (ML) criteria.

Ibrahim, K. M.; Wertheimer, G. D.; Bachalo, William D.

1991-01-01

142

Structure of a swirl-stabilized spray flame by imaging, laser Doppler velocimetry, and phase Doppler anemometry  

Science.gov (United States)

Data are presented which describe the mean structure of a steady, swirl-stabilized, kerosene spray flame in the near-injector region of a research furnace. The data presented include ensemble-averaged results of schlieren, luminosity, and extinction imaging, measurement of the gas phase velocity field by laser Doppler velocimetry, and characterization of the condensed phase velocity by phase Doppler anemometry. The results of these studies define six key regions in the flame: the dense spray region; the rich, two-phase, fuel jet; the main air jet; the internal product recirculation zone; the external product recirculation zone; and the gaseous diffusion flame zone. The first five of these regions form a conical mixing layer which prepares the air and fuel for combustion. The air and fuel jets comprise the central portion of this mixing layer and are bounded on either side by the hot product gases of the internal and external recirculation zones. Entrainment of these product gases into the air/fuel streams provides the energy required to evaporate the fuel spray and initiate combustion. Intermittency of the internal recirculation and spray jet flows accounts for unexpected behavior observed in the aerodynamics of the two phases. The data reported herein are part of the database being accumulated on this spray flame for the purpose of detailed comparison with numerical modeling.

Edwards, C. F.; Rudoff, R. C.

1991-01-01

143

[Laser Doppler vibrometry: a new tool for diagnosing hearing loss with an intact eardrum].  

Science.gov (United States)

The diagnosis of hearing loss with an intact eardrum frequently requires an entire battery of hearing tests, without the guarantee of an exact diagnosis. The techniques frequently provide only orientation for it, without establishing the site of the lesion and the etiology of the hearing loss. Laser Doppler vibrometry is a new technique, which has recently proved capable, of partially resolving this problem. The method is based on the study of the sound-induced vibration of the eardrum in humans in vivo, using a laser Doppler vibrometer. The method proved to be useful in the diagnosis of the pathology of the middle ear sound transmission system, avoiding the need for exploratory tympanotomy. Called "laser-audiometry", the method promises to become a new diagnostic tool for hearing impairment. PMID:17802945

Turcanu, Diana; Mâr?u, D; Dalhoff, E; Gummer, A W

2006-01-01

144

Laser Doppler blood flow complementary metal oxide semiconductor imaging sensor with analog on-chip processing  

International Nuclear Information System (INIS)

A 4x4 pixel array with analog on-chip processing has been fabricated within a 0.35 ?m complementary metal oxide semiconductor process as a prototype sensor for laser Doppler blood flow imaging. At each pixel the bandpass and frequency weighted filters necessary for processing laser Doppler blood flow signals have been designed and fabricated. Because of the space constraints of implementing an accurate ?0.5 filter at the pixel level, this has been approximated using the ''roll off'' of a high-pass filter with a cutoff frequency set at 10 kHz. The sensor has been characterized using a modulated laser source. Fixed pattern noise is present that is demonstrated to be repeatable across the array and can be calibrated. Preliminary blood flow results on a finger before and after occlusion demonstrate that the sensor array provides the potential for a system that can be scaled to a larger number of pixels for blood flow imaging

145

Ultrasonic flowmetering with reflected pulses  

Science.gov (United States)

Consolidated Edison of New York City has expressed the need for a new gasmeter for accurately monitoring large diameter interdistrict gas transmission lines for loss due to theft or leakage. A research effort aimed at developing a new flowmeter for Con Edison is described. The new flowmeter uses ultrasonic flowmetering technology in a novel way to meet Con Edison's four major design specifications: the flowmeter should be accurate to 0.5 percent of totalized flow over one year, it should be much simpler to install than a conventional flowmeter, essentially meaning that excavation be limited to that necessary to expose the upper surface of a buried main; its installation must not require service shutdown; and, the flowmeter should not require zero-flow calibration once installed in the gas main.

Hoyle, D. C.; Glicksman, L. R.; Peterson, C. R.

1984-09-01

146

Detection on micro-Doppler effect based on 1550 nm laser coherent radar  

Science.gov (United States)

A laser coherent detection system of 1550 nm wavelength was presented, and experimental research on detecting micro-Doppler effect in a dynamic target was developed. In this paper, the return signal in the time domain is decomposed into a set of components in different wavelet-scales by multi-resolution analysis, and the components are associated with the vibrational motions in a target. The micro-Doppler signatures are extracted by applying the reconstruction (inverse wavelet transform). During the course of the final data processing frequency analysis and time-frequency analysis are applied to analyze the vibrational signals and estimate the motion parameters successfully. The experimental results indicate that the micro-Doppler information in a moving can be effectively detected, and tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analysis and time-frequency analysis.

Jun, Zhang; Yang, Sun; Zenghui, Cao; Tengfei, Sun; Tiantian, Zheng

2014-01-01

147

Size, velocity and flow concentration measurements in sprays by laser-Doppler-anemometry  

Science.gov (United States)

A modified laser Doppler anemometer which uses the Doppler phase shift from two photodetectors for particle size correlations and measures the size and velocity of discrete small particles simultaneously is described. The new method delivers two-dimensional distributions for enclosed flow situations in multiphase flow systems with a very high spatial resolution and with accepted rates of counted events of about 250 per second. The local behavior of drops in the free flow situation of a spray generated by a water nozzle, and the role of the air entrainment are discussed. The presented experimental results verify the use of the Doppler-phase-shift method in complex multiphase flow systems like liquid atomization and spray systems.

Bauckhage, K.

148

Optical output enhances flowmeter accuracy  

Science.gov (United States)

Magnetic flowmeter with a direct-coupled optical output increases accuracy and operates independently of other system inputs. The design includes simple external adjustment and signal amplitude control.

Wolpin, E. G.

1965-01-01

149

TVO-Flowmeter  

International Nuclear Information System (INIS)

TVO-flowmeter has been field tested in boreholes in the crystalline bedrock. It is possible to measure the groundwater flow both across and along a borehole. Sensitivity is better than 1 ml/h (milliliter per hour) for the flow across the hole. This corresponds the flux value (Darcy velocity) of about 2*10-9 m/s. The system makes it possible to determine roughly the direction of the flow across the hole. The boreholes in the bedrock change flow conditions. The effects of the borehole and flowmeter-borehole combination are studied by theoretical models. Field examples are presented from flows along and across the hole. The sensitivity of the instrument is demonstrated. Several repeated measurements are presented. Examples are shown of the variation of the flow with time

150

Multiphase flowmeter measurement uncertainties  

Energy Technology Data Exchange (ETDEWEB)

The paper describes the state of the art in multiphase flow metering from a theoretical point of view, giving brief details of how the individual mass flowrates of each phase are derived. The limitations imposed by using such calculation procedures are then fully explained in terms of metering uncertainties. By referring to previous theoretical work, the level of uncertainty in the individual mass flowrate measurements for a typical multiphase flowmeter are shown to be in excess of 10 per cent for virtually all possible combinations of oil, water and gas phase fractions. Most importantly though, it is shown that the individual mass flowrate uncertainties are very dependent upon the flow composition. It is therefore concluded that for any multiphase flowmeter, uncertainty data must be qualified with a statement of the flow composition to which it applies. (author)

Millington, B.C.; Whitaker, T.S. (National Engineering Lab., East Kilbride (United Kingdom))

1992-01-01

151

Automatic flowmeter calibration system  

Science.gov (United States)

A system for automatically calibrating the accuracy of a flowmeter is described. The system includes a calculator capable of performing mathematical functions responsive to receiving data signals and function command signals. A prover cylinder is provided for measuring the temperature, pressure, and time required for accumulating a predetermined volume of fluid. Along with these signals, signals representing the temperature and pressure of the fluid going into the meter are fed to a plurality of data registers. Under control of a progress controller, the data registers are read out and the information is fed through a data select circuit to the calculator. Command signals are also produced by a function select circuit and are fed to the calculator set indicating the desired function to be performed. The reading is then compared with the reading produced by the flowmeter.

Lisle, R. V.; Wilson, T. L. (inventor)

1981-01-01

152

Multiphase-flowmeter experience  

Energy Technology Data Exchange (ETDEWEB)

Multiphase-flowmeters (MPFM`s) are finding increasing acceptance offshore, where operators are becoming more comfortable with the technology after several years of familiarization. Meters are being used in well testing, well management, and allocation of production. Since the first deliveries of the Framo engineering A/S meter in 1993, significant experience has been gained in both topside and subsea applications of the devices. The paper describes purposes, technology, Framo`s meter, applications, performance verification, and operational problems.

NONE

1998-04-01

153

Fiber-based multi-beam laser Doppler vibrometer for measuring transient vibrations  

Science.gov (United States)

This article presents a novel fiber-based multi-beam laser Doppler vibrometer (LDV). In this design, a single wavelength laser source at 1550 nm combined with several acousto-optic modulators (AOM) form the transmitter head of the LDV. At the receiver side, one single high-speed photo-detector is employed, instead of multiple detectors according to other reported multi-beam laser Doppler vibrometer.1, 2 Utilization of spatial encoding technique allows us to produce transmitted laser beams with different frequency shifts. In this work, a laser source passes through a sequence of totally four AOMs at different regimes, producing a 4×5 laser beam matrix which is then sent onto different points of vibrating targets for measurement. The backscattered light signals are collected back into a single mode fiber by a fiber collimator and combined with a common reference beam. This mixture of optical signals passes through an Erbium Doped Fiber Amplifier (EDFA) before it is detected by a high-speed fiber-based InGaAs photo-detector. With a digital demodulation algorithm implemented in Labview, the phase variations and thus the vibrations of different testing points can be extracted separately from their corresponding frequency bands. The experimental results show it is possible to do a precise vibration measurement on twenty testing points simultaneously using this novel multi-beam LDV.

Guo, M.; Fu, Y.; Phua, P. B.

2011-02-01

154

Flowmeter evaluation for on-orbit operations  

Science.gov (United States)

Various flowmetering concepts were flow tested to characterize the relative capabilities and limitations for on-orbit fluid-transfer operations. Performance results and basic operating principles of each flowmetering concept tested are summarized, and basic considerations required to select the best flowmeter(s) for fluid system application are discussed. Concepts tested were clamp-on ultrasonic, area averaging ultrasonic, offset ultrasonic, coriolis mass, vortex shedding, universal venturi tube, turbine, bearingless turbine, turbine/turbine differential-pressure hybrid, dragbody, and dragbody/turbine hybrid flowmeters. Fluid system flowmeter selection considerations discussed are flowmeter performance, fluid operating conditions, systems operating environments, flowmeter packaging, flowmeter maintenance, and flowmeter technology. No one flowmetering concept tested was shown to be best for all on-orbit fluid systems.

Baird, R. S.

1988-01-01

155

A study of radial-flow turbomachinery blade vibration measurements using Eulerian laser Doppler vibrometry  

Science.gov (United States)

The structural integrity of blades is critical to the health of turbomachinery. Since operational failure of these blades can possibly lead to catastrophic failure of the machine, it is important to have knowledge of blade conditions in an online fashion. Due to several practical implications, it is desired to measure blade vibration with a non-contact technique. The application of laser Doppler vibrometry towards the vibration based condition monitoring of axial-flow turbomachinery blades has been successfully demonstrated in previous work. In this paper the feasibility of using laser Doppler vibrometry to measure radial-flow turbomachinery blade vibrations is investigated with the aid of digital image correlation and strain gauge telemetry.

Oberholster, A. J.; Heyns, P. S.

2014-05-01

156

Comparative laser Doppler measurement on tooth pulp blood flow at 632 and 750 nm  

Science.gov (United States)

Laser-Doppler flowmetry has been used for the assessment of pulp blood flow in health and disease. General purpose laser Doppler instruments working at the Helium-Neon (632,8 nm) as well as IR (750 - 810 nm) wavelengths have been used in this application. Specially designed handheld equipment has also been used to assess blood supply to the tooth. A considerable difference in the measurement results have been noticed when using different wavelengths and probe designs. In this study some of the problems related to the use of various wavelengths and probe designs are studied in human teeth and in a physical model of a tooth. Our results support the early observation that measurements at different wavelengths and with different probe designs cannot be directly compared.

Oberg, P. Ake; Pettersson, Hans; Rohman, Hakan

1993-12-01

157

3D flow measurements in nuclear fuel rod bundles using Laser Doppler velocimetry  

International Nuclear Information System (INIS)

Using a two color Laser Doppler velocimeter, mean velocities and turbulence intensities have been measured in a complex geometric structure close to the 17 x 17 square lattice nuclear fuel rod bundles. Good accuracy of the control volume location and high data rate acquisition have been achieved. Comparisons are made between four different optical configurations measuring the same phenomenon. In this paper attention is focused not only on understandable discrepancies but also on unpredictable minor uncertainties

158

Analysis of Signal-to-Noise Ratio of the Laser Doppler Velocimeter  

DEFF Research Database (Denmark)

The signal-to-shot-noise ratio of the photocurrent of a laser Doppler anemometer is calculated as a function of the parameters which describe the system. It is found that the S/N is generally a growing function of receiver area, that few large particles are better than many small ones, and that generally the "fringe" or l"differential" mode configuration is equal to, or better than, the "reference beam" mode.

Lading, Lars

1973-01-01

159

Local Heating as a Predilatation Method for Measurement of Vasoconstrictor Responses with Laser-Doppler Flowmetry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studying microvascular responses to iontophoresis of vasoconstricting drugs contributes to a better understanding of the regulatory mechanisms of cutaneous vessels, but measuring these responses with laser-Doppler flowmetry at basal blood flow conditions is technically challenging. This study aimed to investigate whether the measurement of cutaneous vasoconstrictor responses to noradrenaline (NA) and phenylephrine (PE), delivered by iontophoresis, is facilitated by predilatation of the microv...

Henricson, Joakim; Baiat, Yashma; Sjo?berg, Folke

2011-01-01

160

Towards a velocity-resolved microvascular blood flow measure by decomposition of the laser Doppler spectrum  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The tissue microcirculation, as measured by laser Doppler flowmetry (LDF), comprises both capillary, arterial and venous blood flow. With the classical LDF approach, it has been impossible to differentiate between different vascular compartments. We suggest an alternative LDF algorithm that estimates at least three concentration measures of flowing red blood cells (RBCs), each associated with a predefined, physiologically relevant, absolute velocity in mm/s. As the RBC flow velocity depends o...

Larsson, Marcus; Stro?mberg, Tomas

2006-01-01

 
 
 
 
161

Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA) is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurements in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiment...

Marcos Pinotti; Faria, Edna M.

2006-01-01

162

Full-field high-speed laser Doppler imaging system for blood-flow measurements  

Science.gov (United States)

We describe the design and performance of a new full-field high-speed laser Doppler imaging system developed for mapping and monitoring of blood flow in biological tissue. The total imaging time for 256x256 pixels region of interest is 1.2 seconds. An integrating CMOS image sensor is utilized to detect Doppler signal in a plurality of points simultaneously on the sample illuminated by a divergent laser beam of a uniform intensity profile. The integrating property of the detector improves the signal-to-noise ratio of the measurement, which results in high-quality flow-images provided by the system. The new technique is real-time, non-invasive and the instrument is easy to use. The wide range of applications is one of the major challenges for a future application of the imager. High-resolution high-speed laser Doppler perfusion imaging is a promising optical technique for diagnostic and assessing the treatment effect of the diseases such as e.g. atherosclerosis, psoriasis, diabetes, skin cancer, allergies, peripheral vascular diseases, skin irritancy and wound healing. We present some biological applications of the new imager and discuss the perspectives for the future implementations of the imager for clinical and physiological applications.

Serov, Alexandre; Lasser, Theo

2006-02-01

163

Coherent summation of spatially distorted laser Doppler signals by using a two-dimensional heterodyne detector array  

Science.gov (United States)

Phase-sensitive coherent summation of individual heterodyne detector array signals was demonstrated for the enhanced detection of spatially distorted laser Doppler returns. With the use of a 2 x 2 heterodyne detector array, the phase and amplitude of a time-varying speckle pattern was detected, and the signal-to-noise ratio of the Doppler shift estimate was shown to be improved by a factor of 2, depending on the extent of spatial coherence loss. These results are shown to agree with a first-order analysis and indicate the advantage of coherent summation for both short-range laser Doppler velocimetry and long-range atmospheric coherent lidar.

Chan, Kin P.; Killinger, Dennis K.

1992-01-01

164

Measurement of isotope ratios by Doppler-free laser spectroscopy applying semiconductor diode lasers and thermionic diode detection  

International Nuclear Information System (INIS)

In this correspondence, where preliminary results of isotope ratio measurements in Ba are given, the authors will demonstrate the simple but powerful application of diode lasers in isotope-selective trace element detection and isotope dilution techniques using LEI Doppler-free two-photon spectroscopy and thermionic diode detection, which may become an easy to operate and low-cost alternative to mass spectrometry

165

Incident beam polarization for laser Doppler velocimetry employing a sapphire cylindrical window  

Science.gov (United States)

For laser Doppler velocimetry studies employing sapphire windows as optical access ports, the birefringency of sapphire produces an extra beam intersection volume which serves to effectively smear the acquired velocity flow field data. It is shown that for a cylindrical window geometry, the extra beam intersection volume may be eliminated with minimal decrease in the fringe visibility of the remaining intersection volume by suitably orienting the polarizations of the initial laser beams. For horizontally incident beams, these polarizations were measured at three intersection locations within the cylinder. It was found that the measured polarization angles agreed with the theoretical predictions.

Lock, J. A.; Schock, H. J.

1985-01-01

166

Doppler laser interferometry and low expansion materials - A merging of technologies  

Science.gov (United States)

An extremely sensitive, accurate, and versatile extensometer has been demonstrated for measuring minute thermally induced dimensional changes in large structures fabricated from materials with a near-zero, but difficult to predict, coefficient of thermal expansion (CTE) - such as laminated graphite-epoxy composites. The method employs a commercially available Doppler laser interferometer designed for extremely accurate translation measurements in large machine tools. Operation of the laser device is described together with the special precautions required, and results of thermally cycling a near-zero CTE graphite-epoxy I-beam.

Karlak, Robert F.; Hotz, Dave F.; Haas, Alan K.

1989-06-01

167

The remote measurement of tornado-like flows employing a scanning laser Doppler system  

Science.gov (United States)

The paper deals with a scanning laser Doppler velocimeter system employed in a test program for measuring naturally occurring tornado-like phenomena, known as dust devils. A description of the system and the test program is followed by a discussion of the data processing techniques and data analysis. The system uses a stable 15-W CO2 laser with the beam expanded and focused by a 12-inch telescope. Range resolution is obtained by focusing the optical system. The velocity of each volume of air (scanned in a horizontal plane) is determined from spectral analysis of the heterodyne signal. Results derived from the measurement program and data/system analyses are examined.

Jeffreys, H. B.; Bilbro, J. W.; Dimarzio, C.; Sonnenschein, C.; Toomey, D.

1977-01-01

168

Comparative study of the performance of semiconductor laser based coherent Doppler lidars  

DEFF Research Database (Denmark)

Coherent Doppler Lidars (CDLs), operating at an eye-safe 1.5-micron wavelength, have found promising applications in the optimization of wind-power production. To meet the wind-energy sector's impending demand for more cost-efficient industrial sensors, we have focused on the development of continuous-wave CDL systems using compact, inexpensive semiconductor laser (SL) sources. In this work, we compare the performance of two candidate emitters for an allsemiconductor CDL system: (1) a monolithic master-oscillator-power-amplifier (MOPA) SL and (2) an external-cavity tapered diode laser (ECTDL).

Rodrigo, Peter John; Pedersen, Christian

2012-01-01

169

Torsional vibration measurements on rotating shaft system using laser doppler vibrometer  

Science.gov (United States)

In this work, a laser torsional vibrameter was used to measure the torsion vibration of a rotating shaft system under electrical network impact. Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) are non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. Furthermore, a highly complex shafting system is analyzed by a modified Riccati torsional transfer matrix. The system is modeled as a chain consisting of an elastic spring with concentrated mass points, and the multi-segments lumped mass model is established for this shafting system. By the modified Riccati torsional transfer matrix method, an accumulated calculation is effectively eliminated to obtain the natural frequencies. The electrical network impacts can activize the torsional vibration of shaft system, and the activized torsion vibration frequencies contained the natural frequencies of shaft system. The torsional vibrations of the shaft system were measured under electrical network impacts in laser Doppler torsional vibrometer. By comparisons, the natural frequencies by measurement were consistent with the values by calculation. The results verify the instrument is robust, user friendly and can be calibrated in situ. The laser torsional vibrometer represents a significant step forward in rotating machinery diagnostics.

Xiang, Ling; Yang, Shixi; Gan, Chunbiao

2012-11-01

170

High-resolution (Doppler-limited) spectroscopy using quantum-cascade distributed-feedback lasers  

International Nuclear Information System (INIS)

Lasing characteristics were evaluated for distributed-feedback quantum-cascade (QC) lasers operating in a continuous mode at cryogenic temperatures. These tests were performed to determine the QC lasers close-quote suitability for use in high-resolution spectroscopic applications, including Doppler-limited molecular absorption and pressure-limited lidar applications. By use of a rapid-scan technique, direct absorbance measurements of nitric oxide (NO) and ammonia (NH3 ) were performed with several QC lasers, operating at either 5.2 or 8.5 ?m . Results include time-averaged linewidths of better than 40MHz and long-term laser frequency reproducibility, even after numerous temperature cycles, of 80MHz or better. Tuning rates of 2.5 cm-1 in 0.6ms can be easily achieved. Noise-equivalent absorbance of 3x10-6 was also obtained without optimizing the optical arrangement. copyright 1998 Optical Society of America

171

3-component doppler laser-two-focus velocimetry applied to a transonic centrifugal compressor  

Energy Technology Data Exchange (ETDEWEB)

The conventional laser-two-focus (L2F) method, also known as laser transit anemometry (LTA), measures two components of the flow vector in the plane normal to the optical axis by measuring the time-of-flight of particles crossing the two laser beams in the probe volume. Recently a new three component system was developed, named 3C, Doppler L2F, which operates with the same confocal optical set-up as the two component L2F system, thus enabling three component measurements even under the extremely difficult conditions of limited optical accessibility as they appear for example in centrifugal compressors. The new hybrid system combines the principle of the L2F technique with the basic idea of the doppler global velocimetry (DGV). The two velocity components in the plane perpendicular to the optical axis are measured by the L2F time-of-flight technique, the third velocity component in the direction of the optical axis is determined by analyzing the Doppler frequency shift of the scattered light. The system was developed with respect to an application in a transonic centrifugal compressor and designed in the shape of an optical probe. The set-up and all important components of the 3C, Doppler L2F system are described here in detail, as well as the principle of operation and calibration of the system. Tests on a free jet demonstrate the measurement accuracy of the hybrid technique. Its successful application to a transonic centrifugal compressor was the first time that three component velocity data could be collected from a high loaded, high speed centrifugal impeller. The data are presented and discussed. (orig.)

Foerster, W.; Karpinsky, G.; Krain, H.; Roehle, I.; Schodl, R. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Koeln (Germany). Inst. of Propulsion Technology

2002-07-01

172

Doppler global velocimetry with laser frequency modulation for precise measurements of velocity profiles; Doppler-Global-Velozimetrie mit Laserfrequenzmodulation zur praezisen Messung von Geschwindigkeitsprofilen  

Energy Technology Data Exchange (ETDEWEB)

A novel Doppler global velocimetry (DGV) method with laser frequency modulation is described which enables contactless measurements of the velocity in a plane of a flow. The measurement principle is based on the evaluation of a change in laser light intensity caused by a Doppler-frequency shift at the edge of a molecular absorption curve. The conventional DGV technique uses two cameras for referencing. As a result image misalignments occur causing high measurement errors. Using the novel DGV technique with laser frequency modulation, only one camera is necessary whereby misalignment errors can not occur and a lower measurement uncertainty is attainable. It is shown by experimental results that changes in light intensity do not cause a higher measurement error, if the modulation frequency has been chosen sufficiently high. The lowest uncertainty measured of the new DGV method was 0.02 m/s. (orig.)

Fischer, A.; Buettner, L.; Czarske, J. [Technische Univ. Dresden (Germany). Professur fuer Mess- und Prueftechnik; Muller, H.; Eggert, M. [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

2006-04-15

173

Transient flowmeter calibration facility  

Science.gov (United States)

An apparatus for defining the free surface of a moving column of a fluid in a vertical pipe to enhance the accuracy of measurements of transient rate of flow of the fluid using electromagnetic flowmeter is described. It provides a neutrally buoyant plug which stays in contact with the free surface of the column of the fluid at all times and thus defines the free surface of the fluid moving in the vertical pipe accurately and reduces the oscillations of the free surface of the fluid.

Lefebvre, Paul

1990-12-01

174

Medical diagnosis of the cardiovascular system on the carotid artery with IR laser Doppler vibrometer  

Science.gov (United States)

Laser Doppler Vibrometry (LDV) is known to be a possible diagnosis tool for many cardiac applications as the detection and monitoring of some important vital parameters (Heart Rate, Heart Rate Variability, Pulse Wave Velocity) in a non-contact and non-intrusive way. The technique has become known as Optical Vibrocardiography (VCG) i.e. by measuring the vibrations on the carotid artery or on the thorax [1-5]. The aim of the present study is to interpret the vibrational signal acquired from the carotid artery in relation to the electrocardiographic and hemodynamic aspects and to enable the extraction of further medical information relevant for diagnosis purpose. For the investigation an infrared (IR) Laser Doppler Vibrometer has been used. The acquired VCG signals have been processed and compared with the simultaneously acquired electrocardiogram and the color-coded Doppler sonogram. This has enabled a deeper understanding of the signature of the vibrational signal. Furthermore, in this paper, we also discuss the medical value of the VCG signal obtained from the carotid artery.

Mignanelli, Laura; Rembe, Christian; Kroschel, Kristian; Luik, Armin; Castellini, Paolo; Scalise, Lorenzo

2014-05-01

175

Relationship between peripheral and coronary function using laser Doppler imaging and transthoracic echocardiography.  

Science.gov (United States)

Vascular dysfunction in the coronary and peripheral circulations is an early prognostic marker of future cardiovascular events. Measurements of coronary and peripheral vascular function in resistance vessels can be made, but rely on invasive procedures, which make them unsuitable for routine application. An assessment of the direct correlation between vascular responses in skin and coronary vessels has not been made previously. In 27 normal healthy subjects (18-55 years of age), we examined the relationship between peripheral and coronary vascular function. Cutaneous perfusion was measured using the non-invasive technique of laser Doppler imaging during iontophoresis of acetylcholine and sodium nitroprusside, and cutaneous vascular conductance was calculated (laser Doppler perfusion/mean arterial pressure). Coronary flow reserve was measured using transthoracic echocardiography during intravenous adenosine infusion. Mean diastolic velocities were measured at baseline and peak hyperaemic conditions from the Doppler signal recordings. CVR (coronary velocity reserve) was defined as the ratio of hyperaemic to basal mean diastolic velocities. There were significant positive correlations between CVR and cutaneous vascular conductance for acetylcholine (r=0.399, P=0.039) and sodium nitroprusside (r=0.446, P=0.020). These results support the idea that peripheral measurements of skin blood flow are representative of generalized microvascular function including that of the coronary circulation in normal healthy subjects. PMID:18338981

Khan, Faisel; Patterson, Dean; Belch, Jill J F; Hirata, Kumiko; Lang, Chim C

2008-11-01

176

Development of the immersed sodium flowmeter  

International Nuclear Information System (INIS)

The immersed sodium flowmeter is a flowmeter of all-sealed construction, which can operate in sodium. The immersed sodium flowmeter can be used for resolve the flow measuring problems of the in-reactor component of LMFBR. The construction of this flowmeter is presented. The calibration test for this flowmeter has been made in the sodium test loop that simulates practical condition under sodium. The agreement between the calibration test data and the theoretical calculation values is very good

177

Nonlinear ultrasonic image of fatigue cracks by using laser doppler vibrometry  

International Nuclear Information System (INIS)

A nonlinear acoustic effect is a sensitive tool to detect a micro-scale crack or the early stage of cracking during the fatigue process. Such damage produces a nonlinear stress-strain relationship, and the nonlinearity can be measured by a higher harmonic component in the frequency domain. The 2nd harmonic component and higher harmonic components are subtracted using laser Doppler vibrometry. Because the laser beam can be focused on the smallest spot, the localized nonlinear acoustic parameters can be determined. As the damage increases, the level of nonlinearity increases, which can be used for the diagnosis of micro-cracks. Using a scanning laser beam, localized nonlinear acoustic parameters can be mapped around a cracked specimen. Various nonlinear parameters are chosen and tested around the crack tip, and the most sensitive nonlinear parameter for a micro-crack or closed crack can be optimized

178

Particle sizing by photon correlation laser Doppler anemometer in the submicron/nanometer size range  

Science.gov (United States)

A particle sizing algorithm is developed for nanoparticle sizing with laser Doppler anemometry/velocimetry systems. A model-based signal processing method is used to estimate the particle size from the autocorrelation curve corresponding to a single particle transit. Two kinds of figures of merit functions are combined to improve the sensitivity. The optimal setup parameters (refractive index, wavelength, and observation direction) and trajectory error are investigated in independent simulation studies. At 514-nm illumination wavelength, the most sensitive size region is found below 300 nm down to the sizing limit (20 photons on average from a single particle transit). The required laser power is searched for by the lower sizing limit based on the calibration measurement. The size estimation of a polystyrene sphere particle of 50 nm diameter requires at least 123-kW/cm2 laser power density at 350 nm, while 587 kW/cm2 at 514 nm is used in the studied system.

Vámos, Lénárd; Jani, Péter

2010-01-01

179

Dynamics of shocks in laser-launched flyer plates probed by photon Doppler velocimetry  

Science.gov (United States)

We investigated the launch and impact with glass targets for four different thicknesses of Al laser-launched flyer plates by monitoring the flight with photon Doppler velocimetry (PDV). The amplitudes and damping times of the reverberating shocks in the flyers, created by short laser pulse launching, were investigated as a function of pulse duration using 10 or 20 ns laser pulses. The shorter pulse duration showed a surprisingly more efficient damping process in the thicker flyers. The durations of the supported shocks in the glass targets were also measured as a function of flyer thickness. The supported shock durations were significantly shorter than the common picture of shock round-trip transit time in the flyer.

Curtis, A. D.; Dlott, D. D.

2014-05-01

180

New method of laser doppler flowmetry signal processing in pulp vitality evaluation after teeth cosmetic treatment  

Science.gov (United States)

The present study aims to assess the pulp vitality before and after different tooth bleaching procedures, in order to determine the changes in pulpal microcirculation and whether they are reversible or not. Twelve volunteers were included in this study. For each volunteer, the pulpal blood flow of maxillary teeth was assessed prior to treatment using Laser Doppler Flowmetry. The "in office" bleaching technique was used 6 anterior teeth, with two different gels, a conventional one chemically activated (Group I 3teeth) and another one activated using Nd:YAG laser (Group II-3 teeth). The bleaching agents were applied on counterpart teeth and, after obtaining a esthetic results for each tooth, the pulpal blood flow was assessed using Laser Doppler Flowmetry immediately after treatment and then after one day and one week. All data were collected and statistically analyzed. Immediately after treatment, the assessment showed an increase of pulpal blood flow, for both study groups, but higher in Group I as compared to Group II (pblood flow with non - significant differences between the study groups (plead to irreversible damage to the dental pulp, when used correctly.

Todea, Carmen; Sarpe, Amalia; Vitez, Bogdan; Draganescu, Gheorghe

2014-01-01

 
 
 
 
181

New type of embedded laser Doppler velocimeter for measurement of rotary wings boundary layer  

Science.gov (United States)

An experimental method has been developed to determine the velocity profiles across the boundary layer of rotary wings. The measurement, based on laser Doppler velocimetry, has been tested on a helicopter rotor blade in hover. The main components of the prototype are embedded in an untwisted blade. The beams converging at the measurement volume, which can be moved along perpendicular to the surface, and the signals backscattered by flow particles, are collected through rotating fiber optic cables to a transmitter insuring the connection with fixed components (laser source, photomultipliers, burst spectrum analyzer, computer, etc.). Measurements, performed in a frame linked to the rotating blade for one radial distance from the rotation axis and at a chord abscissa x/c=0.25, have involved the tangential velocity component (chordwise) and the crossflow component (spanwise). The boundary layer has been explored at different rotating speeds of the blade. The accuracy of velocity components measurements has been evaluated in the region very close to the wall and far from the wall. The velocity profiles obtained in different hovering test conditions have shown the efficiency of the present embedded laser Doppler velocimeter method, which can also be applied to rotors in forward flight, wind turbines, etc. Undoubtly, the new database obtained on the rotating boundary layer will constitute an essential support for the physical models and computational works.

Favier, D.; Maresca, C.; Nsi Mba, M.; Berton, E.; Agnes, A.

1997-06-01

182

Experimental and clinical application of laser doppler flowmetry in gastric and duodenal ulcerative bleedings  

Directory of Open Access Journals (Sweden)

Full Text Available The research goal is to develop a new objective diagnostic method of prerecurrence syndrome that will prognose bleeding recurrence from gastroduodenal ulcers. Materials and methods. Method of laser Doppler flowmetry (LDF of the regional perfusion of tissue has been used. The experimental part has been done on 30 white laboratory rats. Characteristics of regional tissue perfusion in the simulation and laser hemostasis of bleeding have been studied. Gastroduodenal endoscopy has been performed with laser Doppler flowmetry (ELDF in clinical conditions to predict the recurrence of ulcerative bleeding. The prognostic method of gastroduodenal ulcerative bleeding was used in 58 patients hospitalized with such pathology and activity of bleeding Forrest II. Results. The study of microcirculation parameters and experimental hemostasis has showed the possibility of using LDF to measure its performance. Effective hemostasis has been accompanied by a significant decrease in perfusion. On the basis of microcirculation parameters in ulcerative bleeding, medical adrenaline test has been proposed for an objective verification pre-recurrence syndrome. To evaluate the effectiveness of endoscopic hemostasis perfusion has been measured before and after its implementation. Conclusion. ELDF has objectified the prognosis of ulcerative bleeding recurrence, verified pre-recurrence syndrome and evaluated the efficacy of endoscopic hemostasis

Afanasieva G.A.

2011-12-01

183

Laser Doppler velocity measurements in subsonic, transonic, and supersonic turbulent boundary layers  

Science.gov (United States)

Recent measurements have used laser Doppler velocimetry to make direct measurements of the Reynolds stress in turbulent boundary layers in the Mach number range 1.5 to 3.0. A serious anomaly, however, is exhibited in these measurements in that the maximum of -u-prime v-prime occurs much farther from the wall than is reasonable for flow at constant pressure. The purpose of the present experiments was to obtain redundant data over a substantial range of Mach numbers (0.1-2.2) in an effort to resolve the anomaly in turbulent shearing stress.

Dimotakis, P. E.; Lang, D. B.; Collins, D. J.

1979-01-01

184

The application of laser Doppler velocimetry to trailing vortex definition and alleviation  

Science.gov (United States)

A laser Doppler velocimeter whose focal volume can be rapidly traversed through a flowfield has been used to overcome the problem introduced by excursions of the central vortex filament within a wind tunnel test section. The basic concepts of operation of the instrument are reviewed and data are presented which accurately define the trailing vortex from a square-tipped rectangular wing. Measured axial and tangential velocity distributions are given, both with and without a vortex dissipator panel installed at the wing tip. From the experimental data, circulation and vorticity distributions are obtained and the effect of turbulence injection into the vortex structure is discussed.

Orloff, K. L.; Grant, G. R.

1973-01-01

185

Measurement of turbulent flow using ultrasound velocity profile method. 2. Comparison with laser doppler velocimetry  

International Nuclear Information System (INIS)

Ultrasonic Velocity Profile (UVP) measuring method has many advantages over the conventional flow measurement methods, such as measurement of an instantaneous velocity profile on a line with the transducer was measured, and it is applicable to opaque liquids because of possible to measure from outside of the wall. This method has capabilities applicable to various flow measurements, but requires a large measurement volume. In this paper, the effect of the measurement volume on the mean velocity profile have been investigated for fully developed turbulent flows in a vertical pipe and was compared with a result obtained by Direct Numerical Simulation (DNS) and results of Laser Doppler Velocimetry (LDV) measurement. (author)

186

Determination of air and hydrofoil pressure coefficient by laser doppler anemometry  

Directory of Open Access Journals (Sweden)

Full Text Available Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp was experimentally determined by Laser Doppler Anemometry (LDA measurements. Two models were tested: model of airplane G4 (Super Galeb and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles.

Risti? Slavica S.

2010-01-01

187

Adaptive Model-Based Mine Detection/Localization using Noisy Laser Doppler Vibration Measurements  

Energy Technology Data Exchange (ETDEWEB)

The acoustic detection of buried mines is hampered by the fact that at the frequencies required for obtaining useful penetration, the energy is quickly absorbed by the ground. A recent approach which avoids this problem, is to excite the ground with a high-level low frequency sound, which excites low frequency resonances in the mine. These resonances cause a low-level vibration on the surface which can be detected by a Laser Doppler Vibrometer. This paper presents a method of quickly and efficiently detecting these vibrations by sensing a change in the statistics of the signal when the mine is present. Results based on real data are shown.

Sullivan, E J; Xiang, N; Candy, J V

2009-04-06

188

Pulsed-laser Doppler flowmetry provides basis for deep perfusion probing  

Science.gov (United States)

A setup for pulsed-laser Doppler flowmetry (LDF) measurements has been built and tested. Measurements were carried out comparing continuous-wave and pulsed LDF. With pulsed LDF a higher peak power can be injected into the tissue without exceeding the safety limits. This enables a much larger spacing between the locations of illumination and detection. Thus, the penetration depth, and thus the measurement volume, can be enlarged using the pulsed-LDF method. This method will allow, e.g., monitoring of the cerebral perfusion.

Kolkman, Roy G. M.; Hondebrink, Erwin; Bolt, René A.; Steenbergen, Wiendelt; de Mul, Frits F. M.

2001-11-01

189

Determination of Capsaicin Induced Increase in Dermal Blood Flow Using Laser Doppler Flowmetry Technique  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the present study, we evaluated laser Doppler flowmetry technique using LDF100C (Biopac systems) by determining blood flow changes following acute application of capsaicin on 12 healthy human subjects. Capsaicin applied locally (topical application) at a dose of 0.075% produced significant increase in mean dermal blood flow from 31.4 ± 3.1 Blood Perfusion Units (BPU) to 115. 7 ± 24.6 Blood Perfusion Units (BPU) after 30 minutes, also there was significant difference in dermal blood flow ...

Sunil Kumar Reddy Khambam; Madireddy Umamaheshwar Rao Naidu; Pingali Usha Rani; Takallapalli Ramesh Kumar Rao

2011-01-01

190

High resolution laser spectroscopy in cold supersonic molecular beams. Cooling, reduction of Doppler width and applications  

International Nuclear Information System (INIS)

The cooling of molecules during the adiabatic expansion of supersonic seeded molecular beams is reviewed and illustrated by the example of NO2-molecules. The reduction of the Doppler-width by collimation of the beam and the cooling to low rotational temperatures brings a significant simplification of the complex NO2-absorption spectrum and allows its assignment. The measured rotational temperature was Trot = 10K. Some examples from our work illustrate this promising technique of high resolution laser spectroscopy in cold beams. (author). 17 refs, 4 figs

191

Ultrasonic flowmeters: a progress report  

International Nuclear Information System (INIS)

This progress report describes the components and system configuration of the prototype ultrasonic flowmeter and initial flow testing. It is the second in a series of progress reports on the development and testing of ultrasonic flowmetering concepts. The greatest advantage of an ultrasonic flowmeter is that the instrument can be installed on the outside of a pipe with no modifications required. The flow is measured through the pipe walls. However, complex electronic systems are needed for the measurements. The ultrasonic flowmeter features: high resolution limited only by the electronics; fast response since there are no moving parts; measurement over a wide range of flow conditions; portability; and can be used for a range of different pipe sizes. No current alternative method of measuring flow combines all these advantages

192

New float flowmeter  

Science.gov (United States)

A new float flowmeter design is presented based on the null method, with electric output signal and either manual or automatic current control in a coil to bring the float back to zero position. The instrument concerned is a constriction-type device and based on its theory a simple expression can be derived for describing the input-output relationship in quadratic terms. In addition to a description of the device, the static calibration curves using air at 295.16±0.50 K are also provided for volumetric flowrates ranging from 11 to 16 dm3/min and Reynolds numbers between 500 and 800. Typical inaccuracy is 1.8% of flowrate over this range.

Vallascas, Rinaldo

1987-08-01

193

Parâmetros dopplervelocimétricos na avaliação da perviedade da anastomose portossistêmica intra-hepática transjugular (TIPS): estudo prospectivo / Doppler flowmeter parameters for evaluation of transjugular intrahepatic porto-systemic shunts (TIPS) patency: prospective study  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Estudar as alterações hemodinâmicas consideradas normais após a realização da anastomose portossistêmica intra-hepática transjugular (TIPS) e a eficácia dos parâmetros sugestivos de estenose do TIPS com o ultra-som Doppler. MATERIAIS E MÉTODOS: Dezesseis pacientes foram avaliados de maneir [...] a prospectiva, no período de dezembro de 2001 a março de 2003. As avaliações foram realizadas 24-48 horas após o TIPS e a seguir em intervalos regulares de 30 dias, três meses, seis meses e um ano, com ultra-som modo B, Doppler pulsado, Doppler colorido e de amplitude em diferentes pontos da prótese relacionados ao TIPS. A angiografia foi realizada apenas para a confirmação dos resultados e terapêutica pertinente. RESULTADOS: Até o momento apenas os achados de fluxo contínuo no terço proximal da prótese e o gradiente de velocidade entre dois pontos da prótese apresentaram significância estatística para o diagnóstico de estenose do TIPS (p Abstract in english OBJECTIVE: To assess the hemodynamic changes considered normal after transjugular intrahepatic porto-systemic shunt (TIPS) placement and the efficacy of TIPS parameters suggestive of stenosis using Doppler sonography. MATERIALS AND METHODS: Sixteen patients were prospectively evaluated from December [...] , 2001 to March, 2003 after TIPS placement. Evaluations were performed 24 to 48 hours after the procedure and then at intervals of 30 days, three months, six months and one year using B mode, color Doppler, power Doppler and spectral Doppler in different TIPS related sites. Angiography was performed only to confirm Doppler findings and treatment. RESULTS: To date the only statistically significant parameters for diagnosis of TIPS stenosis were continuous flow pattern in the proximal third of TIPS and the velocity gradient between the two sites (p

Antonio Sergio Zafred, Marcelino; Maria Cristina, Chammas; Ilka Regina Souza de, Oliveira; André Cosme de, Oliveira; Osvaldo Ignácio, Pereira; Francisco César, Carnevale; Osmar de Cássio, Saito; Giovanni Guido, Cerri.

194

Laser system for Doppler cooling of ytterbium ion in an optical frequency standard  

Science.gov (United States)

A laser system for Doppler cooling of ytterbium ion on the 2S1/2 ? 2P1/2 transition in a single-ion optical frequency standard is developed. The second harmonic of a semiconductor laser with a wavelength of 739 nm is used for cooling. The laser frequency is doubled in a nonlinear BiBO crystal embedded in a ring resonator, which also serves as a reference for laser frequency stabilisation. Second-harmonic power of ~100 ?W is generated at a wavelength of 369.5 nm. Diode laser radiation is modulated by an electro-optic modulator at 14.75 GHz to generate a sideband exciting the 2S1/2 (F = 0) ? 2P1/2 (F = 1) hyperfine component of the cooling transition that is not excited by resonant cooling light. The sideband relative intensity of a few percent proved to be sufficient to reduce the ion dwelling time in the 2S1/2 (F = 0) state to less than 10-4 s and increase the cooling efficiency.

Chepurov, S. V.; Lugovoy, A. A.; Kuznetsov, S. N.

2014-06-01

195

Laser Doppler technique for nondestructive evaluation of mechanical heart valves kinematics  

Science.gov (United States)

Laser techniques for vibration measurement, due to their non-contact nature, represents an interesting alternative investigational tool to be tested in biomedical and clinic fields. A particular application could be as evaluation method in design and quality control of artificial organs. Aim of this study is to investigate the application of laser vibrometry to the study of mechanical heart valves in-vitro, with an ad hoc set-up. A heterodyne laser Doppler vibrometry system, which allows the measurement of both vibrational velocity and displacement was used. Three different approaches have been carried out, in order to stress the limits of the laser vibrometry technique for testing heart valve prostheses. Critical points and difficulties to build up experimental studies in this field were clearly pointed out. In the present study only one laser head was used, the aim of the authors being to test the feasibility of a simplified approach on mechanical cardiac valves. Starting from that analysis a comparison could be made to assess the capability to discriminate between normal and malfunctioning devices. The advantage of the proposed test bench is that it could provide a non-contact, non-destructive analysis of the valve under the same working conditions as those upon implantation. The proposed method could furnish a typical "fingerprint" characterizing each valve behavior in repeatable experimental conditions.

Grigioni, Mauro; Daniele, Carla; Morbiducci, U.; Del Gaudio, C.; D'Avenio, Giuseppe; Di Meo, D.; Barbaro, Vincenzo

2004-06-01

196

Experimental investigation of buried landmine detection using time division multiplexing of multibeam laser Doppler vibrometer channels  

Science.gov (United States)

Producing vibration images of buried landmines using a multi-beam laser Doppler vibrometer (MB-LDV) operating from a stationary platform have been accomplished in the past. Detection from a continuously moving platform can reduce the time of detection compared to stop-and-stare measurement. However, there is a speed limitation, imposed by the required spatial and frequency resolution. NCPA proposed a concept of time division multiplexing (TDM) of laser beams of a MB-LDV to overcome that speed limitation. The system, based on 16-beam MB-LDV, has been built and experimentally tested at an Army test facility. Vibration velocity profiles of buried mines have been obtained at different system speeds. Algorithms for speckle noise reduction in continuously moving MB-LDV signals have been developed and explored. The results of the current data collection, recent past data collection as well as the results of the effectiveness of speckle noise reduction techniques are presented.

Burgett, Richard; Aranchuk, Vyacheslav; Aranchuk, Ina

2012-06-01

197

High resolution laser induced fluorescence Doppler velocimetry utilizing saturated absorption spectroscopy  

International Nuclear Information System (INIS)

A high resolution laser induced fluorescence (LIF) system has been developed to measure the flow velocity field of neutral particles in an electron-cyclotron-resonance argon plasma. The flow velocity has been determined by the Doppler shift of the LIF spectrum, which is proportional to the velocity distribution function. Very high accuracy in velocity determination has been achieved by installing a saturated absorption spectroscopy unit into the LIF system, where the absolute value and scale of laser wavelength are determined by using the Lamb dip and the fringes of a Fabry-Perot interferometer. The minimum detectable flow velocity of a newly developed LIF system is ±2 m/s, and this performance remains unchanged in a long-time experiment. From the radial measurements of LIF spectra of argon metastable atoms, it is found that there exists an inward flow of neutral particles associated with neutral depletion.

198

Visualization of solitary waves via laser Doppler vibrometry for heavy impurity identification in a granular chain  

International Nuclear Information System (INIS)

We study the propagation of highly nonlinear solitary waves in a one-dimensional granular chain composed of homogeneous spherical particles that includes a heavy impurity. We experimentally investigate the transmission and backscattering behavior of solitary waves in the region of the impurity by using a laser Doppler vibrometer. To assess the sensitivity of solitary waves to various impurity masses, this non-contact measurement technique is complemented by a conventional contact measurement method based on an instrumented sensor particle. By leveraging these two schemes, we find that the travelling time and attenuation of backscattered solitary waves are highly sensitive to the location and mass of an inserted impurity. The experimental results are found to be in satisfactory agreement with the numerical results obtained from a discrete element model and the theoretical predictions based on nonlinear wave dynamics and classical contact theory. This study demonstrates that laser Doppler vibrometry can be an efficient tool to visualize highly nonlinear wave propagation in granular media. With a view towards potential applications, highly nonlinear solitary waves can be employed as nondestructive probing signals to identify heavy impurities embedded in ordered granular architectures. (paper)

199

Agent-based station for on-line diagnostics by self-adaptive laser Doppler vibrometry  

Science.gov (United States)

A self-adaptive diagnostic system based on laser vibrometry is proposed for quality control of mechanical defects by vibration testing; it is developed for appliances at the end of an assembly line, but its characteristics are generally suited for testing most types of electromechanical products. It consists of a laser Doppler vibrometer, equipped with scanning mirrors and a camera, which implements self-adaptive bahaviour for optimizing the measurement. The system is conceived as a Quality Control Agent (QCA) and it is part of a Multi Agent System that supervises all the production line. The QCA behaviour is defined so to minimize measurement uncertainty during the on-line tests and to compensate target mis-positioning under guidance of a vision system. Best measurement conditions are reached by maximizing the amplitude of the optical Doppler beat signal (signal quality) and consequently minimize uncertainty. In this paper, the optimization strategy for measurement enhancement achieved by the down-hill algorithm (Nelder-Mead algorithm) and its effect on signal quality improvement is discussed. Tests on a washing machine in controlled operating conditions allow to evaluate the efficacy of the method; significant reduction of noise on vibration velocity spectra is observed. Results from on-line tests are presented, which demonstrate the potential of the system for industrial quality control.

Serafini, S.; Paone, N.; Castellini, P.

2013-12-01

200

Investigation of time-resolved single detector Doppler global velocimetry using sinusoidal laser frequency modulation  

Science.gov (United States)

We present a new Doppler global velocimetry (DGV) technique that is based on sinusoidal laser frequency modulation: FM-DGV. DGV is an optical method to measure two-dimensional velocity fields in fluid flows. The measurement principle is based on measuring the Doppler shift of the laser frequency with the use of an absorption cell converting frequency variations into intensity variations. In order to measure the scattered light intensity, conventional DGV systems use a signal and a reference camera. Using the FM-DGV technique, no additional reference camera is required. Thus significant error sources can be eliminated, e.g. image misalignment errors, which can limit the performance of conventional DGV. In this paper, a comparison between both DGV systems and an error analysis of the FM-DGV system is given. The parameter optimization of the FM-DGV is discussed as well. A minimum measured standard deviation of 0.02 m s-1 was achieved. Measurement results of applications to a rotating glass disc as a calibration object, a free jet flow and a laminar boundary layer flow are presented to demonstrate the ability of FM-DGV also for low-speed and unsteady flow conditions.

Fischer, Andreas; Büttner, Lars; Czarske, Jürgen; Eggert, Michael; Grosche, Gesine; Müller, Harald

2007-08-01

 
 
 
 
201

Fractal Dimension Characterization of in-vivo Laser Doppler Flowmetry signals  

Science.gov (United States)

Laser Doppler Blood Flow meter uses tissue backscattered light to non-invasively assess the blood flow rate. qualitatively. As there is large spatial variability and the temporal heterogeneity in tissue microvasculature, the measured blood flow rate is expressed in relative units. A non-linear approach in order to understand the dynamics of the microcirculation led to the fractal characterization of the blood flow signals. The study presented in the paper aims to analyze the fractal behavior of Laser Doppler Flow (LDF) signals and to quantitatively estimate the fractal dimension of waveforms using Box-Counting method. The measured Fractal dimension is an estimate of temporal variability of tissue perfusion. The rate at which fractal dimension varies as a function of location between individuals, exhibits a weak correlation with time. Further studies with a larger number of subjects are necessary to test the generality of the findings and if changes in dimension are reproducible in given individuals. In conclusion, the fractal dimension determined by Box-counting method may be useful for characterizing LDF time series signals. Future experiments evaluating whether the technique can be used to quantify microvascular dysfunction, as commonly occurring in conditions such as Diabetes, Raynaud's phenomenon, Erythromelalgia and Achenbach syndrome needs to be evaluated.

Srinivasan, Gayathri; Sujatha, N.

202

Parâmetros dopplervelocimétricos na avaliação da perviedade da anastomose portossistêmica intra-hepática transjugular (TIPS: estudo prospectivo Doppler flowmeter parameters for evaluation of transjugular intrahepatic porto-systemic shunts (TIPS patency: prospective study  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Estudar as alterações hemodinâmicas consideradas normais após a realização da anastomose portossistêmica intra-hepática transjugular (TIPS e a eficácia dos parâmetros sugestivos de estenose do TIPS com o ultra-som Doppler. MATERIAIS E MÉTODOS: Dezesseis pacientes foram avaliados de maneira prospectiva, no período de dezembro de 2001 a março de 2003. As avaliações foram realizadas 24-48 horas após o TIPS e a seguir em intervalos regulares de 30 dias, três meses, seis meses e um ano, com ultra-som modo B, Doppler pulsado, Doppler colorido e de amplitude em diferentes pontos da prótese relacionados ao TIPS. A angiografia foi realizada apenas para a confirmação dos resultados e terapêutica pertinente. RESULTADOS: Até o momento apenas os achados de fluxo contínuo no terço proximal da prótese e o gradiente de velocidade entre dois pontos da prótese apresentaram significância estatística para o diagnóstico de estenose do TIPS (p OBJECTIVE: To assess the hemodynamic changes considered normal after transjugular intrahepatic porto-systemic shunt (TIPS placement and the efficacy of TIPS parameters suggestive of stenosis using Doppler sonography. MATERIALS AND METHODS: Sixteen patients were prospectively evaluated from December, 2001 to March, 2003 after TIPS placement. Evaluations were performed 24 to 48 hours after the procedure and then at intervals of 30 days, three months, six months and one year using B mode, color Doppler, power Doppler and spectral Doppler in different TIPS related sites. Angiography was performed only to confirm Doppler findings and treatment. RESULTS: To date the only statistically significant parameters for diagnosis of TIPS stenosis were continuous flow pattern in the proximal third of TIPS and the velocity gradient between the two sites (p < 0.001. Different non-statistically significant parameters were also observed. CONCLUSION: Doppler sonography is an efficient tool for the diagnosis of shunt patency and TIPS related complications such as stenosis. However, it is necessary to study a larger number of patients in order to determine a group of parameters that would help in the follow-up of these patients, thus using portal angiography only for indicated treatment.

Antonio Sergio Zafred Marcelino

2004-12-01

203

Self-Calibrating Respiratory-Flowmeter Combination  

Science.gov (United States)

Dual flowmeters ensure accuracy over full range of human respiratory flow rates. System for measurement of respiratory flow employs two flowmeters; one compensates for deficiencies of other. Combination yields easily calibrated system accurate over wide range of gas flow.

Westenskow, Dwayne R.; Orr, Joseph A.

1990-01-01

204

High-resolution (Doppler-limited) spectroscopy using quantum-cascade distributed-feedback lasers  

Energy Technology Data Exchange (ETDEWEB)

Lasing characteristics were evaluated for distributed-feedback quantum-cascade (QC) lasers operating in a continuous mode at cryogenic temperatures. These tests were performed to determine the QC lasers{close_quote} suitability for use in high-resolution spectroscopic applications, including Doppler-limited molecular absorption and pressure-limited lidar applications. By use of a rapid-scan technique, direct absorbance measurements of nitric oxide (NO) and ammonia (NH{sub 3} ) were performed with several QC lasers, operating at either 5.2 or 8.5 {mu}m . Results include time-averaged linewidths of better than 40thinspthinspMHz and long-term laser frequency reproducibility, even after numerous temperature cycles, of 80thinspthinspMHz or better. Tuning rates of 2.5 cm{sup {minus}1} in 0.6thinspthinspms can be easily achieved. Noise-equivalent absorbance of 3{times}10{sup {minus}6} was also obtained without optimizing the optical arrangement. {copyright} {ital 1998} {ital Optical Society of America}

Sharpe, S.W.; Kelly, J.F.; Hartman, J.S. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99532 (United States); Gmachl, C.; Capasso, F.; Sivco, D.L.; Baillargeon, J.N.; Cho, A.Y. [Bell Laboratories, Lucent Technologies, 700 Mountain Avenue, Murray Hill, New Jersey 07974 (United States)

1998-09-01

205

Development of JSNS target vessel diagnosis system using laser Doppler method  

Energy Technology Data Exchange (ETDEWEB)

When an intense pulsed proton beam with a power of 1 MW is irradiated to a mercury target, a pressure wave caused by the proton beam gives a vibration on the target vessel. Pitting damage also occurs on the target vessel, especially incident beam area, resulting in shortening of a life-time. It is very important to monitor the vibration of the target vessel from the view point of the life-time estimation. We developed the target vessel diagnosis system using laser Doppler method and successfully installed it in an actual pulsed spallation source. The diagnosis system consists of retro-reflecting corner-cube mirror (reflective mirror) on the target, mirror assembly in a reflector plug and laser source-detector. The newly developed reflective mirror, made by nickel, was installed by vacuum silver brazing on the target vessel to detect the target vibration. In order to pass the laser beam to the target vessel, a mirror assembly was installed inside the reflector plug. It is replaceable using a remote handling machine during a maintenance period. Nd-YAG laser beam (wave length: 533 nm) with the power of 50 mW was adopted to detect the target vibration. The first proton beam to the target in the spallation neutron source (JSNS) was provided on 30 May 2008. The first signal related to the target vibration was also detected by using this target vessel diagnosis system.

Teshigawara, M., E-mail: teshigawara.makoto@jaea.go.j [Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Wakui, T.; Naoe, T.; Kogawa, H.; Maekawa, F.; Futakawa, M.; Kikuchi, K. [Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken 319-1195 (Japan)

2010-03-15

206

Development of JSNS target vessel diagnosis system using laser Doppler method  

International Nuclear Information System (INIS)

When an intense pulsed proton beam with a power of 1 MW is irradiated to a mercury target, a pressure wave caused by the proton beam gives a vibration on the target vessel. Pitting damage also occurs on the target vessel, especially incident beam area, resulting in shortening of a life-time. It is very important to monitor the vibration of the target vessel from the view point of the life-time estimation. We developed the target vessel diagnosis system using laser Doppler method and successfully installed it in an actual pulsed spallation source. The diagnosis system consists of retro-reflecting corner-cube mirror (reflective mirror) on the target, mirror assembly in a reflector plug and laser source-detector. The newly developed reflective mirror, made by nickel, was installed by vacuum silver brazing on the target vessel to detect the target vibration. In order to pass the laser beam to the target vessel, a mirror assembly was installed inside the reflector plug. It is replaceable using a remote handling machine during a maintenance period. Nd-YAG laser beam (wave length: 533 nm) with the power of 50 mW was adopted to detect the target vibration. The first proton beam to the target in the spallation neutron source (JSNS) was provided on 30 May 2008. The first signal related to the target vibration was also detected by using this target vessel diagnosis system.

207

Einsatzmoeglichkeiten der Laser-Doppler-Anemimetrie bei der Untersuchung der Transsonischen Wechselwirkung Zwischen Verdichtungsstoss und Grenzschicht (Application Possibilities of Laser Doppler Anemometry in the Investigation of the Transonic Interaction Between Shock Wave and Boundary Layer).  

Science.gov (United States)

A laser Doppler anemometer was used in a transonic wind tunnel to investigate the flows about wing profiles containing shock waves and separated zones. Flow states characterized by the absence or the presence of a shock-induced separation were created. Th...

H. J. Schaefer, G. Horny, H. J. Pfeifer, E. Stanewsky

1983-01-01

208

Qualification Testing of Laser Diode Pump Arrays for a Space-Based 2-micron Coherent Doppler Lidar  

Science.gov (United States)

The 2-micron thulium and holmium-based lasers being considered as the transmitter source for space-based coherent Doppler lidar require high power laser diode pump arrays operating in a long pulse regime of about 1 msec. Operating laser diode arrays over such long pulses drastically impact their useful lifetime due to the excessive localized heating and substantial pulse-to-pulse thermal cycling of their active regions. This paper describes the long pulse performance of laser diode arrays and their critical thermal characteristics. A viable approach is then offered that allows for determining the optimum operational parameters leading to the maximum attainable lifetime.

Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Singh, Upendra N.; Kavaya, Michael J.

2007-01-01

209

Observation of optical Ramsey interference frings in collinear ion beam-laser beam interaction by Doppler switching  

International Nuclear Information System (INIS)

We report the observation of optical Ramsey interference fringes in collinear ion beam-laser beam interaction. The analogue of separated fields is created by Doppler switching the ions in two successive zones of the common beam path. New conditions to study quantum interference effects are offered by this method. (orig.)

210

The influence of wavelength and probe configuration on findings of a skin vasoconstriction test when using laser Doppler perfusion devices.  

Science.gov (United States)

The aim of this study was to establish the degree to which a standardized test based on laser Doppler blood flow measurement is dependent on the particular equipment set-up being used. For this purpose, we examined finger skin blood flow with laser Doppler instruments in 20 healthy subjects. In laser Doppler perfusion monitoring (LDPM), we used a custom-made probe with two detecting fibers placed 0.25 and 1.2 mm from the illuminating fiber, respectively, and two laser Doppler perfusion imagers (LDPI) with a wavelength of 632.8 nm and 780 nm, respectively. Warming of the hand was achieved with a Peltier element, and reflex vasoconstriction was induced by immersing the other hand for 3 min into a water bath kept at 15 degrees C. As a measure for the change in skin blood flow, a vasoconstriction index (VAC: cooling/before cooling) was calculated and used for the comparison of the different devices. VAC values gathered around 0.6 for all devices. However, LDPI with a wavelength of 632.8 nm showed a slightly higher VAC index, and the difference was significant. We conclude that using a standardized test is the most appropriate for monitoring changes in blood flow rather than recording and comparing discrete values in intermittent recordings. Although a difference was noted when comparing the devices, different fiber separations and wavelengths seem then to be of little consequence. PMID:16403539

Freccero, Carolin; Wollmer, Per; Sundkvist, Göran; Svensson, Henry

2006-01-01

211

Interrelations of laser doppler flowmetry and brain tissue oxygen pressure during ischemia and reperfusion induced by an experimental mass lesion.  

Science.gov (United States)

The objective of this study was to assess interrelations between bilateral changes of cortical laser doppler flowmetry and intraparenchymal, subcortical partial tissue oxygen tension in the course of an experimental trauma. Ten animals served as a sham group, 8 Sprague-Dawley rats received an unilateral, focal parietal mass lesion. The bilateral course of cortical blood flow measured by laser doppler flowmetry (LDF) was correlated with subcortical, intraparenchymal partial tissue oxygen tension [p(ti)O2]. In the sham-operated group, laser doppler mean flow values drifted between 9.0% and 9.5% and showed no significant changes over time neither between the hemispheres nor within each hemisphere. Absolute mean p(ti)O2 in sham-operated animals was 32.4 mm Hg in the left and 30.5 mm Hg in the right hemisphere. In the trauma group, mean laser doppler flow values during maximum brain compression decreased ipsilateral to 20.3% and contralateral to 34.4% of the baseline values. P(ti)O2 decreased ipsilateral from 25.9 to 6.6 mm Hg (25.4%) and contralateral from 22.6 to 9.8 mm Hg (43.6%). After balloon deflation, cortical LDF was restored much faster compared to p(ti)O2, but did not reach baseline values [ipsilateral 61.6% (p question whether the values obtained represent the microcirculatory situation of the human brain. PMID:10619194

Burger, R; Vince, G H; Meixensberger, J; Bendszus, M; Roosen, K

1999-12-01

212

He-Ne laser effects on blood microcirculation. An in vivo study through laser doppler flowmetry; Efeito do laser de helio neonio sobre a microcirculacao sanguinea durante a reparacao tecidual. Estudo in vivo por meio de fluxometria laser doppler  

Energy Technology Data Exchange (ETDEWEB)

Blood microcirculation performs an important function in tissue repair process, as well as in pain control, allowing for greater oxygenation of the tissues and the accelerated expulsion of metabolic products, that may be contributing to pain. Low Intensity Laser Therapy (LILT) is widely used to promote healing, and there is an assumption that it is mechanism of action may be due to an enhancement of blood supply. The purpose of this study was to evaluate, using laser Doppler flowmetry (LDF), the stated effects caused by radiation emitted by a He-Ne laser ({lambda}=632.8 nm) on blood microcirculation during tissue repair. To this end, 15 male mice were selected and received a liquid nitrogen provoked lesion, above the dorsal region, and blood flow was measured periodically, during 21 days. Due to radiation emission by the LDF equipment, a control group was established to evaluate possible effects caused by this radiation on microcirculation. To evaluate the He-Ne laser effects, a 1.15 J/cm{sup 2} dose was utilized, with an intensity of 6 mW/cm{sup 2}. The results obtained demonstrate flow alterations, provoked by the lesion, and subsequent inflammatory response. There was no statistical difference between the studied groups. As per the analysis of the results there is no immediate effect due the radiation emitted by a He Ne laser on microcirculation, although a percentage increase was observed in day 7 on medium blood flow rate in irradiated specimens. New studies are necessary to validate the use of this wavelength, in order to promote beneficial alterations in blood supply in radiated areas. (author)

Nunez, Silvia Cristina

2002-07-01

213

Maximum-likelihood estimates of the frequency and other parameters of signals of laser Doppler measuring systems operating in the one-particle-scattering mode  

International Nuclear Information System (INIS)

Maximum-likelihood equations are presented for estimates of the Doppler frequency (speed) and other unknown parameters of signals of laser Doppler anemometers and lidars operating in the one-particle-scattering mode. Shot noise was assumed to be the main interfering factor of the problem. The error correlation matrix was calculated and the Rao - Cramer bounds were determined. The results are confirmed by the computer simulation of the Doppler signal and the numerical solution of the maximum-likelihood equations for the Doppler frequency. The obtained estimate is unbiased, and its dispersion coincides with the Rao-Cramer bound. (laser applications and other topics in quantum electronics)

214

Measurement uncertainty and temporal resolution of Doppler global velocimetry using laser frequency modulation.  

Science.gov (United States)

A Doppler global velocimetry (DGV) measurement technique with a sinusoidal laser frequency modulation is presented for measuring velocity fields in fluid flows. A cesium absorption cell is used for the conversion of the Doppler shift frequency into a change in light intensity, which can be measured by a fiber coupled avalanche photo diode array. Because of a harmonic analysis of the detector element signals, no errors due to detector offset drifts occur and no reference detector array is necessary for measuring the scattered light power. Hence, large errors such as image misalignment errors and beam split errors are eliminated. Furthermore, the measurement system is also capable of achieving high measurement rates up to the modulation frequency (100 kHz) and thus opens new perspectives to multiple point investigations of instationary flows, e.g., for turbulence analysis. A fundamental measurement uncertainty analysis based on the theory of Cramér and Rao is given and validated by experimental results. The current relation between time resolution and measurement uncertainty, as well as further optimization strategies, are discussed. PMID:18641765

Fischer, Andreas; Büttner, Lars; Czarske, Jürgen; Eggert, Michael; Müller, Harald

2008-07-20

215

A multi-point laser Doppler vibrometer with fiber-based configuration.  

Science.gov (United States)

Laser Doppler vibrometer (LDV) is a non-contact optical interferometric system to measure vibrations of structures and machines with a high precision. Normal LDV can only offer a single-point measurement. Scanning LDV is usually impractical to do measurement on transient events. In this paper, a fiber-based self-synchronized multi-point LDV is proposed. The multiple laser beams with different frequency shifts are generated from one laser source. The beams are projected onto a vibrating object, reflected and interfered with a common reference beam. The signal including vibration information of multiple spatial points is captured by one single-pixel photodetector. The optical system is mainly integrated by fiber components for flexibility in measurement. Two experiments are conducted to measure a steady-state simple harmonic vibration of a cantilever beam and a transient vibration of a beam clamped at both ends. In the first measurement, a numerical interpolation is applied to reconstruct the mode shape with increased number of data points. The vibration mode obtained is compared with that from FEM simulation. In transient vibration measurement, the first five resonant frequencies are obtained. The results show the new-reported fiber-based multipoint LDV can offer a vibration measurement on various spatial points simultaneously. With the flexibility of fiber configuration, it becomes more practical for dynamic structural evaluation in industrial areas. PMID:24387407

Yang, C; Guo, M; Liu, H; Yan, K; Xu, Y J; Miao, H; Fu, Y

2013-12-01

216

A multi-point laser Doppler vibrometer with fiber-based configuration  

International Nuclear Information System (INIS)

Laser Doppler vibrometer (LDV) is a non-contact optical interferometric system to measure vibrations of structures and machines with a high precision. Normal LDV can only offer a single-point measurement. Scanning LDV is usually impractical to do measurement on transient events. In this paper, a fiber-based self-synchronized multi-point LDV is proposed. The multiple laser beams with different frequency shifts are generated from one laser source. The beams are projected onto a vibrating object, reflected and interfered with a common reference beam. The signal including vibration information of multiple spatial points is captured by one single-pixel photodetector. The optical system is mainly integrated by fiber components for flexibility in measurement. Two experiments are conducted to measure a steady-state simple harmonic vibration of a cantilever beam and a transient vibration of a beam clamped at both ends. In the first measurement, a numerical interpolation is applied to reconstruct the mode shape with increased number of data points. The vibration mode obtained is compared with that from FEM simulation. In transient vibration measurement, the first five resonant frequencies are obtained. The results show the new-reported fiber-based multipoint LDV can offer a vibration measurement on various spatial points simultaneously. With the flexibility of fiber configuration, it becomes more practical for dynamic structural evaluation in industrial areas

217

Laser Doppler anemometry measurements in a circulating fluidized bed of metal particles  

DEFF Research Database (Denmark)

Laser Doppler Anemometry (LDA) measurements were performed in a 1/9 scale model of a 12 MW circulating fluidized bed (CFB) boiler. The model was operated according to scaling laws. The 2D-LDA system used was positioned in two different ways to obtain the three velocity components u, v and w of the solid phase from which the particle kinetic stresses were determined. The measured velocity profiles are in agreement with previous data from the full-scale boiler, i.e. showing a flat profile over the core region of the riser with a pronounced wall layer. The particle kinetic stresses are found to be anisotropic and strongly influenced by large scale effects originating from the bottom-bed bubbles.

Ibsen, Claus Hübbe; Solberg, Tron

2002-01-01

218

Generation and fluid dynamics of scattering aerosols in laser Doppler velocimetry  

Science.gov (United States)

An experimental study on the particle-fluid interactions of scattering aerosols was performed using monodisperse aerosols of different particle sizes for the application of laser Doppler velocimeters in subsonic turbulence measurements. Particle response was measured by subjecting the particles to an acoustically excited flow field where the particle Reynolds numbers were controlled to simulate the corresponding values of fluid turbulence. The test aerosols were fairly monodisperse with a mean diameter that could be controlled over the size range from 0.1 to 1.0 micron. Experimental results on the generation of a fairly monodisperse aerosol of solid particles and liquid droplets and on the aerosol response in the frequency range 100 Hz to 100 kHz are presented. The present study indicates that a unit density spherical scatterer of 0.3 micron-diameter would be an optimum choice as tracer particles for subsonic air turbulence measurements.

Mazumder, M. K.; Hoyle, B. D.; Kirsch, K. J.

1974-01-01

219

An experimental study of a three-dimensional thrust augmenting ejector using laser Doppler velocimetry  

Science.gov (United States)

Flow field measurements were obtained in a three-dimensional thrust augmenting ejector using laser Doppler velocimetry and hot wire anemometry. The primary nozzle, segmented into twelve slots of aspect ratio 3.0, was tested at a pressure ratio of 1.15. Results are presented on the mean velocity, turbulence intensity, and Reynolds stress progressions in the mixing chamber of the constant area ejector. The segmented nozzle was found to produce streamwise vortices that may increase the mixing efficiency of the ejector flow field. Compared to free jet results, the jet development is reduced by the presence of the ejector walls. The resulting thrust augmentation ratio of this ejector was also calculated to be 1.34.

Storms, Bruce Lowell

1989-01-01

220

Investigation of supersonic separated flow in a compression corner by laser Doppler anemometry  

Science.gov (United States)

A single-component, computer-operated, three dimensional traversing laser Doppler velocimetry system was designed and constructed for a supersonic wind tunnel. The model was a 10 deg compression corner, providing an example of laminar boundary layer separation. Static pressure data and color schlieren photographs were taken. The Mach number was 2.42 and the Reynolds number was 213,000. The flow was seeded with submicron sized oil droplets. The trend of decreasing upstream influence with increasing Reynolds number was confirmed. Mean velocity profiles provided experimental evidence of reversed flow. Points of separation and reattachment were consistent with those determined by schlieren and pressure scans. The flow was of the laminar type until downstream of reattachment. Individual mean velocity and turbulence profiles, as well as velocity histograms are presented.

Baroth, E. C.; Holt, M.

1983-01-01

 
 
 
 
221

Barriers to the management of Diabetes Mellitus – is there a future role for Laser Doppler Flowmetry?  

Directory of Open Access Journals (Sweden)

Full Text Available Diabetes Mellitus (DM is a chronic disease that carries a significant disease burden in Australia and worldwide. The aim of this paper is to identify current barriers in the management of diabetes, ascertain whether there is a benefit from early detection and determine whether LDF has the potential to reduce the disease burden of DM by reviewing the literature relating to its current uses and development. In this literature review search terms included; laser Doppler flowmetry, diabetes mellitus, barriers to management, uses, future, applications, vasomotion, subcutaneous, cost. Databases used included Google Scholar, Scopus, Science Direct and Medline. Publications from the Australian government and textbooks were also utilised. Articles reviewed had access to the full text and were in English.

Minnie Au

2012-12-01

222

EURISOL-DS Multi-MW Target: Cavitations detection by the a Laser Doppler Vibrometer  

CERN Document Server

This technical note summarises the innovative measurement devices used within Task #2 of the European Isotope Separation On-Line Radioactive Ion Beam Facility Design Study (EURISOL-DS) to detect the occurrence of cavitation in liquid metal flowing inside the CGS target mock-up.During the METEX hydraulic experiment carried out at IPUL (Institute of Physics of the University of Latvia), a Laser Doppler Vibrometer was used to characterize the wall vibrations of the beam window at different flow regimes. A series of tests proved the high sensitivity of the LDV to detect the occurrence of cavitation in the liquid metal flowing inside the target. In this context, a dedicated test procedure was developed to establish the validity of using LDV for detecting the onset of cavitation.

Cyril Kharoua, Yacine Kadi, Jacques Lettry, Laure Blumenfeld, Karel Samec (CERN)Knud Thomsen, Sergej Dementevjs, Rade Milenkovich (PSI)Anatoli Zik, Erik Platacis (IPUL)

223

Laser-Doppler anemometry technique applied to two-phase dispersed flows  

International Nuclear Information System (INIS)

The ultimate aim of this experimental investigation is to study droplet hydrodynamics under conditions simulating steam water droplet flow predicted to occur during the reflood portion of LOCA. This research will support the development of advanced systems code for which constitutive laws must be developed ultimately for predicting heat transfer during core reflooding in the vicinity of the rising water level where droplets are formed by violent boiling and broken up by the Leidenfrost phenomenon. The technique involved the utilization of SUNY-SB developed Laser-Doppler anemometer and experimental hardware for flow measurements. In order to do this, an entirely new methodology and the accompanying special electronic instrumentation would have to be developed. To test and verify this new scheme, a solid particle-water flow system has been used. Some preliminary results are presented

224

Numerical solutions and laser-Doppler measurements of spin-up  

Science.gov (United States)

The spin-up flow in a cylinder of homogeneous fluid has been examined both experimentally and numerically. A series of laser-Doppler measurements was made of the zonal flow over a range of Ekman numbers and Rossby numbers at various locations in the interior of the flow. These measurements exceed previous ones in accuracy. The weak inertial modes excited by the impulsive start are detectable. The numerical simulations used the primitive equations in axisymmetric form and employed finite-difference techniques on both constant and variable grids. The number of grid points necessary to resolve the Ekman layers was determined. A thorough comparison of the simulations and the experimental measurements is made which includes the details of the amplitude and frequency of the inertial modes. Agreement to within the experimental tolerance is achieved. Analytical results for conditions identical to those in the experiments are not available but some similar linear and nonlinear theories are also compared with the experiments.

Warn-Varnas, A.; Piacsek, S.; Fowlis, W. W.; Lee, S. M.

1978-01-01

225

Simulating translation-induced laser speckle dynamics in photon Doppler velocimetry.  

Science.gov (United States)

Historically, single-beam optical velocimetry has been limited to measuring only the component of velocity along the beam. However, theoretical work and recent experimental results have shown that laser speckle dynamics may be exploited to measure lateral motion, thereby gaining information about surface dynamics across an additional degree of freedom. In the use of photon Doppler velocimetry (PDV), this new information is considered "free" in that it is already contained within the PDV signal, needing only to be extracted and interpreted correctly. In this manuscript, we relate speckle dynamics to the lateral motion of a planar scattering surface in the PDV coordinate system via the space-time correlation function of the diffracted electric field. Next, we relate the characteristic time scale of speckle intensity fluctuations in the PDV signal to the rate of lateral surface translation and to parameters characterizing the optical probe. Analytical results are compared with a numerical simulation and found to be in close agreement. PMID:25090201

Warren, Will J; Moro, Erik A; Briggs, Matthew E; Flynn, Eric B

2014-07-20

226

Doppler Spectrometry for Ultrafast Temporal Mapping of Density Dynamics in Laser-Induced Plasmas  

International Nuclear Information System (INIS)

We present high resolution measurements of the ultrafast temporal dynamics of the critical surface in moderately overdense, hot plasma by using two-color, pump-probe Doppler spectrometry. Our measurements clearly capture the initial inward motion of the plasma inside the critical surface of the pump laser which is followed by outward expansion. The measured instantaneous velocity and acceleration profiles are very well reproduced by a hybrid simulation that uses a 1D electromagnetic particle-in-cell simulation for the initial evolution and a hydrodynamics simulation for the later times. The combination of high temporal resolution and dynamic range in our measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations.

227

Flow visualization on the linear compressor cascade endwall using oil flows and laser Doppler anemometry  

Science.gov (United States)

Surface oil flow visualizations were conducted in the VPI&SU Department of AOE Low Speed Linear Cascade Wind Tunnel on the endwall. Oil flow visualizations of the endwall flow features (passage flow, cross flow and tip leakage vortex) for tip gap to chord ratios (t/c) of 1.65% and 3.3% are discussed in detail. For the first time, quantitative comparisons are made between the oil-flow direction and the wall shear stress direction obtained from laser Doppler anemometer experimental results. The oil flow streaks are aligned with the wall shear stress direction, except near separation, which is proved theoretically and experimentally. Wall shear stress directions in the oil-flow images are measured and the separation line in the oil flow is calibrated based on the skin friction results from the LDA measurement.

Tian, Qing; Simpson, Roger L.; Tang, Genglin

2004-09-01

228

Higher-order spectral analysis in laser-Doppler flowmetry signal processing.  

Science.gov (United States)

This paper presents an application of higher order statistics and spectra to the problem of laser-Doppler Flowmetry (LDF) for microcirculation monitoring. The proposed signal processing technique computes the bispectra of LDF signals after appropriate pre-processing and extracts features which can be used for classification of the signals to a normal or patient category. Bispectra are defined in terms of the third-order moments or cumulants of signals and are shown to contain valuable information for the above classification of LDF signals. Experimental studies, including (a) a set of 17 normal subjects and 69 patients with Raynaud's phenomenon and (b) 50 LDF-signals separated to four groups from patients that have different pathologic characteristics, are described and results are presented which illustrate the performance of the proposed approach when applied to the LDF signals. PMID:10463299

Alexopoulos, V; Kollias, S; Leger, P; Boccalon, H; Csiki, Z

1999-01-01

229

Laser Doppler velocimeter for vehicle application with improved signal-to-noise ratio  

Science.gov (United States)

Laser Doppler velocimeter (LDV) with improved signal-to-noise ratio (SNR) is presented to measure the vehicle velocity. A novel optical structure named split-reuse type configuration is developed to improve the SNR of LDV. Reference measurements were provided by measuring the outer surface of a precision single-axis turntable. Under these conditions, the measurement uncertainty of the instrument is better than 0.56 % with 95 % confidence interval. The split-reuse type LDV has been tested with an automobile on the open road, and the measurement results are comparing with the results of a precision spatial filter velocimeter, which verify the feasibility of split-reuse type LDV to measure the self-velocity of vehicle.

Nie, Xiaoming; Zhou, Jian; Long, Xingwu

2014-09-01

230

Current concepts in assessment of microvascular endothelial function using laser Doppler imaging and iontophoresis.  

Science.gov (United States)

Effective evaluation of endothelial function is a powerful tool for determining patients at risk of development and progression of cardiovascular disease. As an alternative to invasive tests of endothelial function, several noninvasive methods have been developed, including the use of laser Doppler flowmetry/imaging to measure cutaneous perfusion accompanied by iontophoresis of acetylcholine and sodium nitroprusside. It is clear from previous studies that this technique provides an easy, validated, and reproducible method for investigators to assess and monitor endothelial function in patients with a variety of pathologic conditions, but it may also be used to examine disease progression over time and responsiveness to treatment, thereby facilitating clinical trials. However, a standardization of protocols would help reduce the apparent controversy seen in the literature. With its increasing use by other groups, it is anticipated that further published studies will help to provide a better understanding of the development and progression of cardiovascular disease. PMID:18555183

Turner, Jamie; Belch, Jill J F; Khan, Faisel

2008-05-01

231

Evaluation of microvascular reactivity with laser Doppler flowmetry in chronic kidney disease.  

Science.gov (United States)

Cardiovascular diseases are the major causes of mortality in patients with chronic kidney disease (CKD). The complex process of accelerated athero- and arteriosclerosis in CKD is associated with this phenomenon, where endothelial dysfunction (ED) is one of the initial steps. Hence, the early diagnosis of ED can potentially lead to early interventions which could result in a better outcome for these patients. Several methodologies have been developed for the diagnosis of ED. Laser Doppler flowmetry (LDF) enables us to study the microcirculation continuously in a non-invasive manner. In our review we would like to focus on different tests developed for LDF, like postocclusive reactive hyperaemia, local heating, iontophoresis, microdialysis or analysis of flowmotion. We would also like to summarize the available data in CKD with these methodologies to enlighten their perspectives in the clinical use on this patient population. PMID:24255889

Babos, Levente; Járai, Zoltán; Nemcsik, János

2013-08-01

232

A novel laser Doppler velocimeter and its integrated navigation system with strapdown inertial navigation  

Science.gov (United States)

In order to suppress the error accumulation effect of inertial navigation system (INS), an idea of building an integrated navigation system using a laser Doppler velocimeter (LDV) together with strapdown inertial navigation (SIN) is proposed. The basic principle of LDV is expounded while a novel LDV with advanced optical structure is designed based on the split and reuse technique, and the process of dead reckoning using an integrated system which consists of LDV and SIN is discussed detailedly. The results of theory and experiment show that: the split and reuse type LDV has great advantages of high accuracy and signal-to-noise ratio, which has greatly enhanced the position accuracy of the navigation system. The position error has been decreased from 1166 m in 2 h with pure SIN to 20 m in 2 h with the integrated system.

Zhou, Jian; Nie, Xiaoming; Lin, Jun

2014-12-01

233

On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement.  

Science.gov (United States)

Pulse wave velocity (PWV) is an important marker for cardiovascular risk. The Laser Doppler vibrometry has been suggested as a potential technique to measure the local carotid PWV by measuring the transit time of the pulse wave between two locations along the common carotid artery (CCA) from skin surface vibrations. However, the present LDV setups are still bulky and difficult to handle. We present in this paper a more compact LDV system integrated on a CMOS-compatible silicon-on-insulator substrate. In this system, a chip with two homodyne LDVs is utilized to simultaneously measure the pulse wave at two different locations along the CCA. Measurement results show that the dual-LDV chip can successfully conduct the PWV measurement. PMID:23847745

Li, Yanlu; Segers, Patrick; Dirckx, Joris; Baets, Roel

2013-07-01

234

Measurement of velocity distribution and turbulence in a special wind tunnel using a laser Doppler velocimeter  

Science.gov (United States)

The flow behavior in a jet mixing visualization chamber for turbulent fuel spray mixing with air under compression, e.g., at top dead center in diesel engines, was investigated with a laser Doppler velocimeter. The measurements were performed in two cuts in the profile perpendicular to the flow direction. The range of flow conditions in the measuring chamber was tested. The measurements were conducted with and without turbulence grids and shear flow grids behind the inlet nozzle. Wire grids did not enhance the turbulence in the measuring chamber. One of the tested shear flow grids produced shear flow as expected. A turbulence grid whose design was based on experimental results, produced a turbulence degree of up to 30% over the whole measuring cross section.

Mueller, J.; Petersen, J. C.; Pilz, E.; Wiegand, H.

1981-06-01

235

Automatic measurement of field-dependent elastic modulus and damping by laser Doppler vibrometry  

International Nuclear Information System (INIS)

A method for characterizing the magnetoelastic dependence of both Young's modulus and damping on the magnetic field is presented. It is based on laser Doppler vibrometry and free longitudinal vibration in soft ferromagnetic rods and wires, and offers a broad range of improved features including accuracy, lack of interaction with the sample, speed of measurement, full automation, high resolution and the possibility of stress-dependence studies. All these allow samples to be perfectly characterized in the full magnetic field range, estimating the behaviour of the specimen as different magnetization curves are followed and discovering critical points that had been overlooked in previous works. As an example, the magnetoelastic characterization of nickel rods is described, and excellent results are obtained which are consistent with the hysteresis loop of nickel and the theory of magnetic domains in ferromagnetic materials

236

Laser Doppler velocimeter measurement in the tip region of a compressor rotor  

Science.gov (United States)

The axial and tangential velocity components near the tip region of a compressor rotor were measured by a laser Doppler velocimeter. The measurements were taken at 25 radial locations in the outer twenty percent of the blade span and at 10 axial locations upstream, inside and at the exit of the rotor. The results are interpreted to derive the behavior of the leakage flow, annulus wall boundary layer growth, inviscid effects and the rotor wake decay characteristics in the tip region. The inviscid and annulus wall boundary layer effects dominate up to quarter chord, beyond which the leakage phenomena has a major influence in altering the flow characteristics in the outer ten percent of the blade span. The annulus wall boundary layer undergoes drastic change through the passage. The velocity field measured near the leading edge reveals the effects of rapid acceleration near the suction surface and the stagnation point on the pressure surface.

Murthy, K. N. S.; Lakshminarayana, B.

1984-01-01

237

SHOOT flowmeter and pressure transducers  

Science.gov (United States)

A venturi flowmeter has been designed and constructed for the Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The calibration results obtained from the SHOOT venturi demonstrate the ability of the flowmeter to meet the requirements of the SHOOT experiment. Flow rates as low as 20 cu dm/h and as high as 800 cu dm/h have been measured. Performances of the SHOOT differential and absolute pressure transducers, which have undergone calibration and vibration tests, are also included. Throughout the tests, the responses of the transducers remained linear and repeatable to within + or - 1 percent of the full scales of the transducers.

Kashani, A.; Wilcox, R. A.; Spivak, A. L.; Daney, D. E.; Woodhouse, C. E.

1990-03-01

238

Cost-effectiveness of laser Doppler imaging in burn care in the Netherlands  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Early accurate assessment of burn depth is important to determine the optimal treatment of burns. The method most used to determine burn depth is clinical assessment, which is the least expensive, but not the most accurate. Laser Doppler imaging (LDI is a technique with which a more accurate (>95% estimate of burn depth can be made by measuring the dermal perfusion. The actual effect on therapeutic decisions, clinical outcomes and the costs of the introduction of this device, however, are unknown. Before we decide to implement LDI in Dutch burn care, a study on the effectiveness and cost-effectiveness of LDI is necessary. Methods/design A multicenter randomised controlled trial will be conducted in the Dutch burn centres: Beverwijk, Groningen and Rotterdam. All patients treated as outpatient or admitted to a burn centre within 5 days post burn, with burns of indeterminate depth (burns not obviously superficial or full thickness and a total body surface area burned of ? 20% are eligible. A total of 200 patients will be included. Burn depth will be diagnosed by both clinical assessment and laser Doppler imaging between 2–5 days post burn in all patients. Subsequently, patients are randomly divided in two groups: ‘new diagnostic strategy’ versus ‘current diagnostic strategy’. The results of the LDI-scan will only be provided to the treating clinician in the ‘new diagnostic strategy’ group. The main endpoint is the effect of LDI on wound healing time. In addition we measure: a the effect of LDI on other patient outcomes (quality of life, scar quality, b the effect of LDI on diagnostic and therapeutic decisions, and c the effect of LDI on total (medical and non-medical costs and cost-effectiveness. Discussion This trial will contribute to our current knowledge on the use of LDI in burn care and will provide evidence on its cost-effectiveness. Trial registration NCT01489540

Hop M Jenda

2013-02-01

239

Permanent magnet flowmeter having improved output terminal means  

Science.gov (United States)

Disclosed is an improved permanent magnet flowmeter capable of withstanding bending stresses in the direction of induced emf signals. The flowmeter includes a unique terminal arrangement integrally formed with the flowmeter by trepanning opposing wall sections of the flowmeter body. The terminal arrangement provides increased flowmeter sensitivity by increasing the strength of the induced emf signals.

August, Charles (Darien, IL); Myers, Harry J. (Downers Grove, IL)

1984-01-01

240

Permanent-magnet flowmeter having improved output-terminal means  

Science.gov (United States)

Disclosed is an improved permanent magnet flowmeter capable of withstanding bending stresses in the direction of induced emf signals. The flowmeter includes a unique terminal arrangement integrally formed with the flowmeter by trepanning opposing wall sections of the flowmeter body. The terminal arrangement provides increased flowmeter sensitivity by increasing the strength of the induced emf signals.

August, C.; Myers, H.J.

1981-10-26

 
 
 
 
241

Dynamic Calibration of Gas Flowmeters.  

Science.gov (United States)

A major difficulty in obtaining the dynamic response of flowmeters is assessing the true dynamic flow, since this depends on the pneumatic impedance of the system of wmeasuring element is part. A method is described for obtaining the impedance from the co...

K. R. Maslen

1972-01-01

242

Dynamic calibration of turbine flowmeters  

Science.gov (United States)

Turbine flowmeters are calibrated dynamically by means of frequency response tests, provided small perturbations are used. The indicated flow is related to the actual flow by a first order lag function. This lag function is completely defined by the breakpoint frequency which is directly proportional to mean flow rate.

Stevens, G. H.

1969-01-01

243

Skin blood flow from gas transport: helium xenon and laser Doppler compared  

International Nuclear Information System (INIS)

A study was designed to compare three independent measures of cutaneous blood flow in normal healthy volunteers: xenon-133 washout, helium flux, and laser velocimetry. All measurements were confined to the volar aspect of the forearm. In a large group of subjects we found that helium flux through intact skin changes nonlinearly with the controlled local skin temperature whereas helium flux through stripped skin, which is directly proportional to skin blood flow, changes linearly with cutaneous temperature over the range 33 degrees to 42 degrees. In a second group of six volunteers we compared helium flux through stripped skin to xenon-133 washout (intact skin) at a skin temperature of 33 degrees, and we found an essentially linear relationship between helium flux and xenon measured blood flow. In a third group of subjects we compared helium flux blood flow (stripped skin) to laser doppler velocimetric (LDV) measurements (intact skin) at adjacent skin sites and found a nonlinear increase in the LDV skin blood flow compared to that determined by helium over the same temperature range. A possible explanation for the nonlinear increases of helium flux through intact skin and of LDV output with increasing local skin temperature is that they reflect more than a change in blood flow. They may also reflect physical changes in the stratum corneum, which alters its diffusional resistance to gas flux and its optical characteristics

244

Effect of low level laser therapy on revascularization of free gingival graft using ultrasound Doppler flowmetry.  

Science.gov (United States)

Low level laser therapy (LLLT) is widely used during the post-operative period to accelerate the healing process. It promotes beneficial biological action on neovascularization with anti-inflammatory and analgesic effects. Two systemically healthy patients with Miller's grade II recession on 33 and 41, respectively, were treated with free gingival graft. After surgery, second patient received LLLT using a 830 nm diode laser, with output power of 0.1 W on the first day half hour following surgery, on the third day, seventh day, and lastly on the ninth day. Both the patients were asked to assess the pain on second, fourth and tenth day using a Numerical Rating Scale and revascularization of the grafted area was assessed using a color Doppler ultrasound imaging on the fourth and the ninth day. Neovascularization was noted in both the patients but the second patient elicited marked increase in vascularity on the fourth as well as the tenth day and drastic reduction in pain on day four, with no change on the tenth day. The results showed that LLLT was an effective adjunctive treatment in promoting reevascularization and pain control during early healing of free gingival graft. PMID:25024560

Arunachalam, Lalitha T; Sudhakar, Uma; Janarthanam, Akila Sivaranjani; Das, Nimisha Mithra

2014-05-01

245

Femtosecond laser pulse train effect on Doppler profile of cesium resonance lines  

Science.gov (United States)

We present direct observation of the velocity-selective optical pumping of the Cs ground state hyperfine levels induced by the femtosecond (fs) laser oscillator centered at either D2 (6 2S1/2?6 2P3/2, 852 nm) or D1 (6 2S_{1/2}to6 2P1/2, 894 nm) cesium line. We utilized previously developed modified direct frequency comb spectroscopy (DFCS) which uses a fixed frequency comb for the excitation and a weak cw scanning probe laser centered at the 133Cs 6 2S1/2?6 2P3/2 transition (D2 line) for ground levels population monitoring. The frequency comb excitation changes the usual Doppler absorption profile into a specific periodic, comblike structure. The mechanism of the velocity selective population transfer between the Cs ground state hyperfine levels induced by fs pulse train excitation is verified in a theoretical treatment of the multilevel atomic system subjected to a pulse train resonant field interaction.

Vuji?i?, N.; Vdovi?, S.; Aumiler, D.; Ban, T.; Skenderovi?, H.; Pichler, G.

2007-03-01

246

Applications of spectral analysis and filter design in laser frequency locking for Na Doppler lidars  

Science.gov (United States)

A dye ring laser is stabilized to a D2a Doppler-free feature of sodium vapor using a LabVIEW®-based, phase-sensitive servo. Locking precision and stability, at better than +/-1 MHz, are suitable for Na lidar applications. This performance was achieved with improved digital filtering and new approaches to the problem. The inverse (type II) Chebyshev discrete filter employed demonstrates superior filtering and computational efficiency plus improved flexibility. New approaches include the determination of optimum modulation frequency, laser-tuning sensitivity, and bandwidth requirements via spectral analyses of the noise spectrum, derivative scan, and modulated spectrum. This practice guides a user in selecting the system operation parameters and negotiating the trade-offs involved when expanding the filter's passband. Allan deviation plots provide a quantitative description of the short- and long-term frequency excursions. A comparison of Allan deviation plots before and after locking shows a substantial improvement in stability throughout time scales from 0.10 to 10 s.

Smith, John A.; Chu, Xinzhao; Huang, Wentao; Tan, Bo

2009-10-01

247

Dual-beam laser Doppler vibrometer for measurement of pulse wave velocity in elastic vessels  

Science.gov (United States)

When a fluid flowing through an elastic vessel is subjected to a sudden change in pressure gradient, pressure pulses will propagate through the fluid. Velocity of these pulse waves (PWV) can be determined by simultaneous detection of wall distension on two separate points on the vessel wall, along its trajectory. PWV depends on wall stiffness, and under certain circumstances, wall stiffness can be calculated from the propagation velocity. Optical interferometry is a noncontacting technique that allows measurement of wall distension on discrete locations. In this work we propose a miniaturized dual-beam laser Doppler vibrometer (LDV) to measure wall distension simultaneously at two locations. Our dual-beam LDV is based on a single laser source and one acousto-optic modulator with as much as possible of the interferometer optics shared among the different beams. The dual-beam LDV was used for simultaneous detection of wall distension of several elastic vessels of different stiffness. We found that PWV as measured in elastic vessels agrees well with theoretically expected values, and measurement precision is better than 5%. Moreover, the dual-beam LDV performs almost as good as commercial systems for detection of PWV. The dual-beam LDV can have applications in cardiovascular risk management. Stiffness of large arteries has a very good predictive value for cardiovascular disease and overall mortality. This parameter can be estimated from arterial PWV. Current methods to measure arterial PWV suffer from several shortcomings. A dual-beam LDV can offer substantial advantages over existing techniques.

Campo, Adriaan; Dirckx, Joris

2011-08-01

248

Nonperturbing measurements of spatially distributed underwater acoustic fields using a scanning laser Doppler vibrometer  

Science.gov (United States)

Localized changes in the density of water induced by the presence of an acoustic field cause perturbations in the localized refractive index. This relationship has given rise to a number of nonperturbing optical metrology techniques for recording measurement parameters from underwater acoustic fields. A method that has been recently developed involves the use of a Laser Doppler Vibrometer (LDV) targeted at a fixed, nonvibrating, plate through an underwater acoustic field. Measurements of the rate of change of optical pathlength along a line section enable the identification of the temporal and frequency characteristics of the acoustic wave front. This approach has been extended through the use of a scanning LDV, which facilitates the measurement of a range of spatially distributed parameters. A mathematical model is presented that relates the distribution of pressure amplitude and phase in a planar wave front with the rate of change of optical pathlength measured by the LDV along a specifically orientated laser line section. Measurements of a 1 MHz acoustic tone burst generated by a focused transducer are described and the results presented. Graphical depictions of the acoustic power and phase distribution recorded by the LDV are shown, together with images representing time history during the acoustic wave propagation.

Harland, Andy R.; Petzing, Jon N.; Tyrer, John R.

2004-01-01

249

Field performance of an all-semiconductor laser coherent Doppler lidar.  

Science.gov (United States)

We implement and test what, to our knowledge, is the first deployable coherent Doppler lidar (CDL) system based on a compact, inexpensive all-semiconductor laser (SL). To demonstrate the field performance of our SL-CDL remote sensor, we compare a 36 h time series of averaged radial wind speeds measured by our instrument at an 80 m distance to those simultaneously obtained from an industry-standard sonic anemometer (SA). An excellent degree of correlation (R2=0.994 and slope=0.996) is achieved from a linear regression analysis of the CDL versus SA wind speed data. The lidar system is capable of providing high data availability, ranging from 85% to 100% even under varying outdoor (temperature and humidity) conditions during the test period. We also show the use of our SL-CDL for monitoring the dependence of aerosol backscatter on relative humidity. This work points to the feasibility of a more general class of low-cost, portable remote sensors based on all-SL emitters for applications that require demanding laser stability and coherence. PMID:22739880

Rodrigo, Peter John; Pedersen, Christian

2012-06-15

250

Characterization and demonstration of a 12-channel Laser-Doppler vibrometer  

Science.gov (United States)

Scanning laser-Doppler vibrometry is the standard optical, non-contact technology for vibration measurement applications in all areas of mechanical engineering. The vibration signals are measured from the different measurement points at different time points. This requires synchronization and the technology is limited to repeatable or periodic events. We have explored a new solution for the optical setup of the sensing system of a multi-channel vibrometer that we present in this paper. Our optical system is a 12-channel vibrometer and consists of a 12-channel interferometer unit which is connected with 12 optical fibers to a sensor head with 12 fiber-coupled objective lenses. Every objective lens can be focused manually and is placed in a sphere which can be tilted and fixed by a blocking screw. Thus it is possible to adjust a user defined measurement grid by hand. The user can define the geometry of the measurement grid in a camera image displayed in the software by just clicking on the laser foci. We use synchronous analog-digital conversion for the 12 heterodyne detector signals and a digital 12-channel-demodulator which is connected via USB to a computer. We can realize high deflection angles, good sensitivity, proper resolution, sufficient vibration bandwidth, and high maximum vibration amplitudes. In this paper, we demonstrate the optical and electrical setup of the manually adjustable 12-channel vibrometer, we present the experimentally evaluated performance of our device, and we present first measurements from real automotive applications.

Haist, T.; Lingel, C.; Osten, W.; Bendel, K.; Giesen, M.; Gartner, M.; Rembe, C.

2013-04-01

251

Trace analysis of rubidium hyperfine structure in a flame atomizer using sub-Doppler laser wave-mixing spectroscopy.  

Science.gov (United States)

Nonlinear laser wave mixing is a versatile spectroscopic method for trace elemental analysis at high spectral resolution. Sub-Doppler spectral resolution allows isotope and hyperfine structure measurements of some of the elements even when using a room-pressure analytical flame (i.e., sub-Doppler but Lorentzian broadened spectra). A non-planar wave-mixing optical setup offers some advantages as compared to the conventional planar wave-mixing setup including better signal collection efficiency and easier optical alignment. Using our absorption-based wave mixing, a detection limit of 0.05 ng/mL (i.e., 50 parts-per-trillion) is reported for Rb in an air/acetylene flame, while still maintaining sub-Doppler spectral resolution for the infrared 780.0-nm Rb transition line. PMID:14686765

Weed, Kenneth M; Tong, William G

2003-12-01

252

A simulation environment for assisting system design of coherent laser doppler wind sensor for active wind turbine pitch control  

Science.gov (United States)

In order to assist a system design of laser coherent Doppler wind sensor for active pitch control of wind turbine systems (WTS), we developed a numerical simulation environment for modeling and simulation of the sensor system. In this paper we present this simulation concept. In previous works, we have shown the general idea and the possibility of using a low cost coherent laser Doppler wind sensing system for an active pitch control of WTS in order to achieve a reduced mechanical stress, increase the WTS lifetime and therefore reduce the electricity price from wind energy. Such a system is based on a 1.55?m Continuous-Wave (CW) laser plus an erbium-doped fiber amplifier (EDFA) with an output power of 1W. Within this system, an optical coherent detection method is chosen for the Doppler frequency measurement in megahertz range. A comparatively low cost short coherent length laser with a fiber delay line is used for achieving a multiple range measurement. In this paper, we show the current results on the improvement of our simulation by applying a Monte Carlo random generation method for positioning the random particles in atmosphere and extend the simulation to the entire beam penetrated space by introducing a cylindrical co-ordinate concept and meshing the entire volume into small elements in order to achieve a faster calculation and gain more realistic simulation result. In addition, by applying different atmospheric parameters, such as particle sizes and distributions, we can simulate different weather and wind situations.

Shinohara, Leilei; Pham Tran, Tuan Anh; Beuth, Thorsten; Umesh Babu, Harsha; Heussner, Nico; Bogatscher, Siegwart; Danilova, Svetlana; Stork, Wilhelm

2013-05-01

253

Evaluation of endoscopic laser Doppler flowmetry for measurement of human gastric blood flow  

International Nuclear Information System (INIS)

Endoscopic measurement of gastric blood perfusion by laser Doppler flowmetry (LDF) has been evaluated in 28 patients and 15 healthy vounteers. During the recordings it was necessary to keep the probe in light contact with the mucosa to obtain stable curves and to avoid artificial Doppler signals caused by relative movements between the gastric wall and the probe. Gastric distention by air insufflation did not influence the recorded flow level significantly when air insufflation was moderate. The intravenous injection of 0.6 mg atropine did not cause any significant alteration in recorded blood flow, and this drug may be used as premedication before endoscopic blood flow measurements. Recordings with both 4 kHz and 12 kHz bandwidth of the LDF instruments showed a relative constant relationship for different flow levels, the flow values measured with 12 kHz being about twice the corresponding values measured with 4 kHz. With 12 kHz bandwith more of the disturbance signal is recorded, which makes analysis of endoscopic recorded flow curves difficult and inaccurate. It is therefore recommended to use 4 kHz bandwidth during endoscopic measurements in conscious humans. Blood flow measurements from both sides of the gastric wall were consistently of the same order of magnitude (r=0.91), and the endoscopically recorded output signal increased in three of five patients when a reflecting mirror was placed at the serosal side. The results indicate that endoscopic LDF usually reps indicate that endoscopic LDF usually represents blood perfusion in all layers of the gastric wall

254

21 CFR 868.2320 - Uncompensated thorpe tube flowmeter.  

Science.gov (United States)

... false Uncompensated thorpe tube flowmeter. 868.2320 Section 868.2320...868.2320 Uncompensated thorpe tube flowmeter. (a) Identification. An uncompensated thorpe tube flowmeter is a device intended for...

2010-04-01

255

21 CFR 868.2350 - Gas calibration flowmeter.  

Science.gov (United States)

...2010-04-01 false Gas calibration flowmeter. 868.2350 Section 868.2350 ...Devices § 868.2350 Gas calibration flowmeter. (a) Identification. A gas calibration flowmeter is a device intended for medical...

2010-04-01

256

21 CFR 870.2100 - Cardiovascular blood flowmeter.  

Science.gov (United States)

...2010-04-01 false Cardiovascular blood flowmeter. 870.2100 Section 870.2100... § 870.2100 Cardiovascular blood flowmeter. (a) Identification. A cardiovascular blood flowmeter is a device that is connected to...

2010-04-01

257

21 CFR 868.2340 - Compensated thorpe tube flowmeter.  

Science.gov (United States)

...2010-04-01 false Compensated thorpe tube flowmeter. 868.2340 Section 868.2340...868.2340 Compensated thorpe tube flowmeter. (a) Identification. A compensated thorpe tube flowmeter is a device intended for...

2010-04-01

258

21 CFR 868.2300 - Bourdon gauge flowmeter.  

Science.gov (United States)

...2010-04-01 2010-04-01 false Bourdon gauge flowmeter. 868.2300 Section 868.2300...Monitoring Devices § 868.2300 Bourdon gauge flowmeter. (a) Identification. A bourdon gauge flowmeter is a device intended for...

2010-04-01

259

21 CFR 868.2350 - Gas calibration flowmeter.  

Science.gov (United States)

...2010-04-01 2010-04-01 false Gas calibration flowmeter. 868.2350 Section 868.2350...Monitoring Devices § 868.2350 Gas calibration flowmeter. (a) Identification. A gas calibration flowmeter is a device intended for...

2010-04-01

260

Ultrasonic Doppler measurement of renal artery blood flow  

Science.gov (United States)

An extensive evaluation of the practical and theoretical limitations encountered in the use of totally implantable CW Doppler flowmeters is provided. Theoretical analyses, computer models, in-vitro and in-vivo calibration studies describe the sources and magnitudes of potential errors in the measurement of blood flow through the renal artery, as well as larger vessels in the circulatory system. The evaluation of new flowmeter/transducer systems and their use in physiological investigations is reported.

Freund, W. R.; Meindl, J. D.

1975-01-01

 
 
 
 
261

Feasibility Study of Velocity and Temperature Measurements of an Arcjet Flow using Laser Resonance Doppler Velocimetric (LRDV) Technique  

Science.gov (United States)

Thermal Protection System (TPS) materials are used in space vehicles to shield from high heating environment encountered during their atmospheric reentry. Arcjet wind tunnels are used to simulate the flowfield encountered by the spacecrafts, and are used for testing TPS materials. How well these tests simulate the actual heating environment encountered by space vehicles depends on the characteristics of the simulated flow. The flow characterization requires the determination of temperature, concentration, and velocity of the various atomic and molecular species present in the flow. However, determining these parameters requires a complex set of both analytical and experimental procedures. The ability to properly simulate the flight environment is directly related to the accuracy with which these techniques can be used to define the arcjet Laser Resonance Doppler Velocimetric (LRDV) technique can be used to accurately determine the velocity and temperature of a gaseous species. In this technique, the medium is probed with a laser beam that is in resonance with an absorbing transition of the species. The absorption lineshape is Doppler-shifted due to the flow velocity of the species, and the frequency shift is detected as the variation in intensity of the fluorescence emitted by the species. Thus a measurement of the Doppler shift and the width of a spectral line can give both the temperature and the velocity of the flowfield. This summer, our project was to make a feasibility study to set up an experimental arrangement for the laser resonance Doppler velocimetric technique using a ring dye laser. Experiments required troubleshooting, cleaning, testing, and alignment of two lasers and several diagnostics instruments. All instruments and lasers necessary for the project worked well, but the output power of the broadband fundamental dye laser was limited to about 20 mW. This was quite low as compared to that necessary to obtain second harmonic oscillation at 327.49 nm for the LRDV studies. Further optimization of the dye laser optical elements is necessary before it can be used for the experiment, which requires narrowband (about 20 Mhz) laser operation.

Rob, Mohammad A.

1996-01-01

262

Single-point relative process using Laser-Doppler velocimetry for calibration of flow sensors at temperatures above 100 C  

International Nuclear Information System (INIS)

Due to technical difficulties, the calibration of flow sensors of heat meters above 100 C cannot be performed by the gravimetric standard method. A novel method using a laser Doppler velocimeter (LDV) was therefore developed, based on the gravimetric method below 100 C and on Reynolds' similarity law. This method allows a turbine meter to be calibrated as a secondary flowrate standard with a relative uncertainty below 0,2% for temperatures of up to 180 C. (orig.)

263

Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures  

International Nuclear Information System (INIS)

Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

264

Investigation into the structure of a swirling flow in a model of a vortex combustion chamber by laser doppler anemometry  

Science.gov (United States)

The structure of an isothermal swirling flow is investigated experimentally in a model of a vortex combustion chamber with a horizontal rotation axis and a distributed input of air-fuel jets. The averaged and pulsation characteristics of the velocity field in various sections of the model are measured using laser Doppler anemometry. The features of internal aerodynamics of a new design of a steam-generator firebox are analyzed.

Anufriev, I. S.; Anikin, Yu. A.; Fil'kov, A. I.; Loboda, E. L.; Agafontseva, M. V.; Kasymov, D. P.; Tizilov, A. S.; Astanin, A. V.; Pesterev, A. V.; Evtyushkin, E. V.

2013-01-01

265

A Tool for the Spectral Analysis of the Laser Doppler Anemometer Data of the Cambridge Stratified Swirl Burner  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A series of flow fields generated by a turbulent methane/air stratified swirl burner are investigated using laser Doppler anemometer (LDA). The LDA provides flow field measurements with comparatively high temporal resolutions. However, processing of the power spectral energy density (PSD) and autocorrelation functions (ACF) of the flow velocity by LDA is complicated by the random, intermittent nature of the LDA signal caused by random arrival of particles at the measuring volume. A tool is de...

Zhou, Ruigang; Balusamy, Saravanan; Hochgreb, Simone

2012-01-01

266

Testresults KROHNE 8-inch ultrasonic flowmeter  

Energy Technology Data Exchange (ETDEWEB)

A new development in the field of ultrasonic liquid flowmeasurements has been achieved with the multichannel liquid ultrasonic flowmeter; the first for use in maintenance-free custody transfer applications. Although ultrasonic flowmeters are used for applications in the oil industry for many years, this new development will have a big impact on custody transfer flow measurement. Not only because of the compactness, but also because of the low investment and operating cost of this flowmeter. This paper describes the system and the method of operation as well as practical experiences and achieved test results of this flowmeter. (author)

Boer, A.H.; Volmer, W.

1997-07-01

267

Laser-Doppler-Velocimetry on the basis of frequency selective absorption: set-up and test of a Doppler Gloval Velocimeter; Laser-Doppler-Velocimetry auf der Basis frequenzselektiver Absorption: Aufbau und Einsatz eines Doppler Global Velocimeters  

Energy Technology Data Exchange (ETDEWEB)

A Doppler Global Velocimeter was set up in the frame of a PhD thesis. This velocimeter is optimized to carry out high accuracy, three component, time averaged planar velocity measurements. The anemometer was successfully applied to wind tunnel and test rig flows, and the measurement accuracy was investigated. A volumetric data-set of the flow field inside an industrial combustion chamber was measured. This data field contained about 400.000 vectors. DGV measurements in the intake of a jet engine model were carried out applying a fibre bundle boroskope. The flow structure of the wake of a car model in a wind tunnel was investigated. The measurement accuracy of the DGV-System is {+-}0.5 m/s when operated under ideal conditions. This study can serve as a basis to evaluate the use of DGV for aerodynamic development experiments. (orig.) [German] Im Rahmen der Dissertation wurde ein auf hohe Messgenauigkeit optimiertes DGV-Geraet fuer zeitlich gemittelte Drei-Komponenten-Geschwindigkeitsmessungen entwickelt und gebaut, an Laborstroemungen, an Teststaenden und an Windkanaelen erfolgreich eingesetzt und das Potential der Messtechnik, insbesondere im Hinblick auf Messgenauigkeit, untersucht. Im Fall einer industriellen Brennkammer konnte ein Volumen-Datensatz des Stroemungsfeldes erstellt werden, dessen Umfang bei ca. 400.000 Vektoren lag. Es wurden DGV-Messungen mittels eines flexiblen Endoskops auf Basis eines Faserbuendels durchgefuehrt und damit die Stroemung in einem Flugzeugeinlauf vermessen. Es wurden DGV-Messungen im Nachlauf eines PKW-Modells in einem Windkanal durchgefuehrt. Die Messgenauigkeit des erstellten DGV-Systems betraegt unter Idealbedingungen {+-}0,5 m/s. Durch die Arbeit wurde eine Basis zur Beurteilung des Nutzens der DGV-Technik fuer aerodynamische Entwicklungsarbeiten geschaffen. (orig.)

Roehle, I.

1999-11-01

268

The “Swiss-cheese Doppler-guided laser tonsillectomy”: a new safe cribriform approach to intracapsular tonsillectomy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Outpatient laser ablation of palatine tonsils is a very interesting procedure that has been recently introduced as a routine in head and neck surgery departments. The aim of this study was to describe a new strategy using a Doppler-guided fibre optic neodymium-yttrium–aluminium–garnet (YAG) laser to remove up to 80 % of tonsillar tissue, as assessed in the long-term postoperative clinical evaluation of the volume of the tonsils at the follow-up, and leaving the capsule in place, thus avo...

Palmieri, B.; Iannitti, T.; Fistetto, G.; Rottigni, V.

2013-01-01

269

Laser-Doppler velocity profile sensor with submicrometer spatial resolution that employs fiber optics and a diffractive lens  

International Nuclear Information System (INIS)

We report a novel laser-Doppler velocity profile sensor for microfluidic and nanofluidic applications and turbulence research. The sensor's design is based on wavelength-division multiplexing. The high dispersion of a diffractive lens is used to generate a measurement volume with convergent and divergent interference fringes by means of two laser wavelengths. Evaluation of the scattered light from tracers allows velocity gradients to be measured in flows with submicrometer spatial resolution inside a measurement volume of 700-?m length. Using diffraction optics and fiber optics, we achieved a miniaturized and robust velocity profile sensor for highly resolved velocity measurements

270

Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow  

Directory of Open Access Journals (Sweden)

Full Text Available Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurements in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiments were conducted for non-pulsate flow (to study the valve performance in the peak flow for the aorta Reynolds number ranging from 3300 to 6800. LDA interrogation volume visited five thousand and one hundred points along the flow (2500 points upstream and 2600 points downstream for each Reynolds number. Post-processing methodology was employed to obtain haemolytic potential colour-coded maps, which were related to turbulent quantities. It was observed that haemolytic regions tend to move downstream the valve when the flow rate is increased.

Pinotti Marcos

2006-01-01

271

Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA) is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurem [...] ents in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiments were conducted for non-pulsate flow (to study the valve performance in the peak flow) for the aorta Reynolds number ranging from 3300 to 6800. LDA interrogation volume visited five thousand and one hundred points along the flow (2500 points upstream and 2600 points downstream) for each Reynolds number. Post-processing methodology was employed to obtain haemolytic potential colour-coded maps, which were related to turbulent quantities. It was observed that haemolytic regions tend to move downstream the valve when the flow rate is increased.

Marcos, Pinotti; Edna M. de, Faria.

2006-09-01

272

Verification and validation of a patient simulator for test and evaluation of a laser doppler vibrometer  

Science.gov (United States)

In the medical community, patient simulators are used to educate and train nurses, medics and doctors in rendering dierent levels of treatment and care to various patient populations. Students have the opportunity to perform real-world medical procedures without putting any patients at risk. A new thrust for the U.S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate (NVESD), is the use of remote sensing technologies to detect human vital signs at stando distances. This capability will provide medics with the ability to diagnose while under re in addition to helping them to prioritize the care and evacuation of battleeld casualties. A potential alternative (or precursor) to human subject testing is the use of patient simulators. This substitution (or augmenting) provides a safe and cost eective means to develop, test, and evaluate sensors without putting any human subjects at risk. In this paper, we present a generalized framework that can be used to accredit patient simulator technologies as human simulants for remote physiological monitoring (RPM). Results indicate that we were successful in using a commercial Laser Doppler Vibrometer (LDV) to exploit pulse and respiration signals from a SimMan 3G patient simulator at stando (8 meters).

Byrd, Kenneth A.; Yauger, Sunny

2012-06-01

273

Particle flow within a transonic compressor rotor passage with application to laser-Doppler velocimetry  

Science.gov (United States)

A theoretical analysis was conducted of the dynamic behavior of micron size particles moving in the three-dimensional flow field of a rotating transonic axial-flow air compressor rotor. The particle velocity lag and angular deviation relative to the gas were determined as functions of particle diameter, mass density and radial position. Particle size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that the particles move essentially on gas stream surfaces and that particle tracking is relatively insensitive to the rotor radial coordinate. Velocity lag and angular deviation increased whenever particle size or mass density increased, and particle tracking was more sensitive to a change in particle diameter than to a corresponding change in mass density. Results indicated that velocity and angular deviations generally less than 1 percent and 1 degree could be achieved with 1 gm/cc tracer particles with diameters of 1 micron or less.

Maxwell, B. R.

1975-01-01

274

Particle flow in blade passages of turbomachinery with application to laser-Doppler velocimetry  

Science.gov (United States)

A theoretical analysis was conducted of the dynamic behavior of micron size particles entrained in gas flow on the two-dimensional blade-to-blade surface of a circular stationary cascade of turbine stator blades. The particle velocity lag and angular deviation relative to the gas was determined as a function of particle diameter and mass density. Particles size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that velocity lag and angular deviation increased whenever particle size or mass density increased, and that particle tracking was more sensitive to a change in particle diameter than to a change in mass density. Results indicated that LDV applications employing 1 gm/cc tracer particles with diameters greater than approximately 1 micron, or 0.5 micron diameter particles with mass densities greater than 4 gm/cc would experience velocity and angular deviations generally greater than 2 percent and 1 degree, respectively.

Maxwell, B. R.

1974-01-01

275

Disbond detection of composite repair patches on concrete structures using laser Doppler vibrometer  

Science.gov (United States)

A technique is presented capable of detecting hidden voids underneath a composite patch adhered to concrete structures as reinforcement. The approach is based upon local membrane vibration of a thin panel when it becomes debonded from the host structure. A state-of-the-art laser Doppler vibrometer is used for high-sensitivity, high-speed and noncontact surface vibration detection. The composite repair patch is excited by piezoelectric patch actuators over a wide frequency range to ensure the presence of the local resonance modes in the scanning image. The results show that both boundary and inner disbonds are detectable by this technique, and the location as well as the size of a disbond as small as 0.75 by 1 in2 can be detected when the excitation frequencies are properly selected and the response image is post-processed. The technology has demonstrated its potential for applications such as quality assurance in concrete infrastructure reinforcement and metal structure repair by composite wrapping or patching. It is also appropriate for delamination detection of composite products during manufacturing.

Sun, Fanping P.; Rogers, Craig A.; Chaudhry, Zaffir A.

1996-04-01

276

Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry  

Science.gov (United States)

The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC×mm/s), and more accurate due to the combination with DRS.

Fredriksson, Ingemar; Burdakov, Oleg; Larsson, Marcus; Strömberg, Tomas

2013-12-01

277

Dynamic Rotor Deformation and Vibration Monitoring Using a Non-Incremental Laser Doppler Distance Sensor  

International Nuclear Information System (INIS)

Monitoring rotor deformations and vibrations dynamically is an important task for improving the safety and the lifetime as well as the energy efficiency of motors and turbo machines. However, due to the high rotor speed encountered in particular at turbo machines, this requires concurrently a high measurement rate and high accuracy, which can not be fulfilled by most commercially available sensors. To solve this problem, we developed a non-incremental laser Doppler distance sensor (LDDS), which is able to measure simultaneously the in-plane velocity and the out-of-plane position of moving rough solid objects with micrometer precision. In addition, this sensor concurrently offers a high temporal resolution in the microsecond range, because its position uncertainty is in principle independent of the object velocity in contrast to conventional distance sensors, which is a unique feature of the LDDS. Consequently, this novel sensor enables precise and dynamic in-process deformation and vibration measurements on rotating objects, such as turbo machine rotors, even at very high speed. In order to evidence the capability of the LDDS, measurements of rotor deformations (radial expansion), vibrations and wobbling motions are presented at up to 50,000 rpm rotor speed.

278

Accurate estimation of normal incidence absorption coefficients with confidence intervals using a scanning laser Doppler vibrometer  

Science.gov (United States)

When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.

Vuye, Cedric; Vanlanduit, Steve; Guillaume, Patrick

2009-06-01

279

Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA) is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurem [...] ents in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiments were conducted for non-pulsate flow (to study the valve performance in the peak flow) for the aorta Reynolds number ranging from 3300 to 6800. LDA interrogation volume visited five thousand and one hundred points along the flow (2500 points upstream and 2600 points downstream) for each Reynolds number. Post-processing methodology was employed to obtain haemolytic potential colour-coded maps, which were related to turbulent quantities. It was observed that haemolytic regions tend to move downstream the valve when the flow rate is increased.

Marcos, Pinotti; Edna M. de, Faria.

280

Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry.  

Science.gov (United States)

The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC×mm/s), and more accurate due to the combination with DRS. PMID:24352692

Fredriksson, Ingemar; Burdakov, Oleg; Larsson, Marcus; Strömberg, Tomas

2013-12-01

 
 
 
 
281

Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry  

Science.gov (United States)

Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

Strömberg, Tomas; Karlsson, Hanna; Fredriksson, Ingemar; Nyström, Fredrik H.; Larsson, Marcus

2014-05-01

282

Laser Doppler anemometer measurements of local fluid recirculation in model rod bundle assemblies  

International Nuclear Information System (INIS)

Experimental studies have been performed at Pacific Northwest Laboratories to investigate the thermal-hydraulic characteristics of model rod-bundle assemblies subjected to conditions representative of certain postulated accident or emergency shutdown scenarios. Studies related to both light water and liquid metal cooled nuclear reactors have been conducted. The bulk of the experimental data gathered during these studies has been laser Doppler anemometer (LDA) measurements of fluid velocity distributions within rod bundle assemblies. The objectives of the various tests were to extend the useful data base for evaluating thermal-hydraulic computer codes used for safety related reactor analysis. Of particular interest has been the ability of the LDA to detect and quantify areas of local fluid recirculation, such as have been found immediately downstream of simulated fuel ballooning blockages and in zones of large differential buoyancy forces for heated rod bundles operated with severe radial power skews. The non-intrusive nature of the LDA technique is considered important for such measurements of induced countercurrent flow

283

Multifractal spectra of laser Doppler flowmetry signals in healthy and sleep apnea syndrome subjects  

Science.gov (United States)

Laser Doppler flowmetry (LDF) signals give a peripheral view of the cardiovascular system. To better understand the possible modifications brought by sleep apnea syndrome (SAS) in LDF signals, we herein propose to analyze the complexity of such signals in obstructive SAS subjects, and to compare the results with those obtained in healthy subjects. SAS is a pathology that leads to a drop in the parasympathetic tone associated with an increase in the sympathetic tone in awakens SAS patients. Nine men with obstructive SAS and nine healthy men participated awaken in our study and LDF signals were recorded in the forearm. In our work, complexity of LDF signals is analyzed through the computation and analysis of their multifractal spectra. The multifractal spectra are estimated by first estimating the discrete partition function of the signals, then by determining their Renyi exponents with a linear regression, and finally by computing their Legendre transform. The results show that, at rest, obstructive SAS has no or little impact on the multifractal spectra of LDF signals recorded in the forearm. This study shows that the physiological modifications brought by obstructive SAS do not modify the complexity of LDF signals when recorded in the forearm.

Buard, Benjamin; Trzepizur, Wojciech; Mahe, Guillaume; Chapeau-Blondeau, François; Rousseau, David; Gagnadoux, Frédéric; Abraham, Pierre; Humeau, Anne

2009-07-01

284

Serial assessment of laser Doppler flow during acute pain crises in sickle cell disease.  

Science.gov (United States)

Changes in basal laser Doppler flowmetry (LDF) of skin blood flow in sickle cell disease are reported to have pathophysiologic relevance in pain crisis. This is the first study to strictly control for LDF variability in determining the value of serial, basal (unprovoked) skin LDF as a practical method to assess resolution of acute pain crisis in sickle cell patients. Daily LDF measurements were repeated on the exact same skin areas of the calf and forehead throughout each of 12 hospital admissions for uncomplicated acute pain crisis. A progressive increase in perfusion was observed in the calf throughout hospitalization as pain crisis resolved, but measurement reproducibility in the calf was poor. Reproducibility in the forehead was better, but no significant trend over time in perfusion was seen. There was no significant correlation between perfusion and pain scores over time. There was also no significant pattern of LDF oscillations over time. In conclusion, only perfusion units and not oscillatory patterns of LDF have probable pathophysiological significance in sickle cell disease vaso-occlusion. The reproducibility of basal skin LDF specifically in sickle cell disease needs to be confirmed. PMID:24857171

Shi, Patricia Ann; Manwani, Deepa; Olowokure, Olugbenga; Nandi, Vijay

2014-12-01

285

A three-velocity-component laser-Doppler velocimeter for measurements inside the linear compressor cascade  

Science.gov (United States)

A 24'' (610 mm) access laser-Doppler velocimeter (LDV) system was developed to make simultaneous three-velocity-component measurements in a low speed linear cascade wind tunnel with moving wall simulation. The probe has a 610 mm access length and achieves a measurement spatial resolution of 100 ?m by using off-axis optical heads. With the relatively large access length, the LDV probe allows for measurements from the side of a wind tunnel instead of through the tunnel floor, while the high spatial resolution allows for quality near-wall measurements. The probe has been tested in a zero-pressure gradient 2D turbulent boundary layer and the test results agree well with the experimental data measured with different LDV systems and hot-wire anemometery for the boundary layer flows. The energy spectral density was estimated using a slot correlation, and Von Kármán’s model for the energy-spectrum function was used to analyze the measured spectral data to estimate the turbulent kinetic energy dissipation rate, which compares favorably with the measured production values in the log-layer region of the turbulent boundary layer. Measurements are presented for the moving endwall boundary layer at the inlet of the linear compressor cascade facility to validate the capability of this LDV for tip leakage flow measurements. These results indicate that the moving endwall reduces velocity gradients in the near-wall region and results in less production of Reynolds stresses and turbulent kinetic energy compared to the stationary endwall case.

Tian, Qing; Lowe, K. Todd; Simpson, Roger L.

2007-10-01

286

Laser Doppler flowmetry: characteristics of a modified single-fibre technique.  

Science.gov (United States)

The single-fibre percutaneous laser Doppler technique has been used in previous studies of intramuscular blood flow. This method facilitates studies of blood flow in deep tissue volumes and minimises the tissue trauma. The technique has been further developed with the aim of improving the signal quality. This has been accomplished by modifying the geometry of the fibre tip. By melting the fibre core material, lenses of different shapes are formed. Flat, spherical and 'pear'-type tips have been manufactured and are evaluated theoretically and experimentally. The paraxial theory cannot accurately predict the position of zones of highest irradiance. Therefore, a ray-tracing program has been developed in the C language, by means of which some of the optical properties of the modified fibre tips can be simulated. Iso-irradiance graphs and beam profiles are calculated for the three different fibre tips. Measured and calculated irradiance curves are used for evaluation of the properties of the ray-tracing model. The three types of fibre tips are also evaluated and compared in flow models. The sphere and pear-type probes show a higher flow sensitivity than the flat-end type. These improvements in flow sensitivity are interpreted as being related to the larger, strongly irradiated tissue volumes in front of the fibres. Intramuscular measurements with the pear-type probe show high sensitivities to induced blood flow changes. PMID:8857305

Cai, H; Rohman, H; Larsson, S E; Oberg, P A

1996-01-01

287

Physiological effects of indomethacin and celecobix: an S-transform laser Doppler flowmetry signal analysis  

Science.gov (United States)

Conventional signal processing typically involves frequency selective techniques which are highly inadequate for nonstationary signals. In this paper, we present an approach to perform time-frequency selective processing of laser Doppler flowmetry (LDF) signals using the S-transform. The approach is motivated by the excellent localization, in both time and frequency, afforded by the wavelet basis functions. Suitably chosen Gaussian wavelet functions are used to characterize the subspace of signals that have a given localized time-frequency support, thus enabling a time-frequency partitioning of signals. In this paper, the goal is to study the influence of various pharmacological substances taken by the oral way (celecobix (Celebrex®), indomethacin (Indocid®) and placebo) on the physiological activity behaviour. The results show that no statistical differences are observed in the energy computed from the time-frequency representation of LDF signals, for the myogenic, neurogenic and endothelial related metabolic activities between Celebrex and placebo, and Indocid and placebo. The work therefore proves that these drugs do not affect these physiological activities. For future physiological studies, there will therefore be no need to exclude patients having taken cyclo-oxygenase 1 inhibitions.

Assous, S.; Humeau, A.; Tartas, M.; Abraham, P.; L'Huillier, J. P.

2005-05-01

288

Physiological effects of indomethacin and celecobix: an S-transform laser Doppler flowmetry signal analysis  

International Nuclear Information System (INIS)

Conventional signal processing typically involves frequency selective techniques which are highly inadequate for nonstationary signals. In this paper, we present an approach to perform time-frequency selective processing of laser Doppler flowmetry (LDF) signals using the S-transform. The approach is motivated by the excellent localization, in both time and frequency, afforded by the wavelet basis functions. Suitably chosen Gaussian wavelet functions are used to characterize the subspace of signals that have a given localized time-frequency support, thus enabling a time-frequency partitioning of signals. In this paper, the goal is to study the influence of various pharmacological substances taken by the oral way (celecobix (Celebrex (registered) ), indomethacin (Indocid (registered) ) and placebo) on the physiological activity behaviour. The results show that no statistical differences are observed in the energy computed from the time-frequency representation of LDF signals, for the myogenic, neurogenic and endothelial related metabolic activities between Celebrex and placebo, and Indocid and placebo. The work therefore proves that these drugs do not affect these physiological activities. For future physiological studies, there will therefore be no need to exclude patients having taken cyclo-oxygenase 1 inhibitions

289

Physiological effects of indomethacin and celecobix: an S-transform laser Doppler flowmetry signal analysis  

Energy Technology Data Exchange (ETDEWEB)

Conventional signal processing typically involves frequency selective techniques which are highly inadequate for nonstationary signals. In this paper, we present an approach to perform time-frequency selective processing of laser Doppler flowmetry (LDF) signals using the S-transform. The approach is motivated by the excellent localization, in both time and frequency, afforded by the wavelet basis functions. Suitably chosen Gaussian wavelet functions are used to characterize the subspace of signals that have a given localized time-frequency support, thus enabling a time-frequency partitioning of signals. In this paper, the goal is to study the influence of various pharmacological substances taken by the oral way (celecobix (Celebrex (registered) ), indomethacin (Indocid (registered) ) and placebo) on the physiological activity behaviour. The results show that no statistical differences are observed in the energy computed from the time-frequency representation of LDF signals, for the myogenic, neurogenic and endothelial related metabolic activities between Celebrex and placebo, and Indocid and placebo. The work therefore proves that these drugs do not affect these physiological activities. For future physiological studies, there will therefore be no need to exclude patients having taken cyclo-oxygenase 1 inhibitions.

Assous, S [Groupe ISAIP-ESAIP, 18, rue du 8 mai 1945, BP 80022, 49180 Saint Barthelemy d' Anjou Cedex (France); Humeau, A [Groupe ISAIP-ESAIP, 18, rue du 8 mai 1945, BP 80022, 49180 Saint Barthelemy d' Anjou Cedex (France); Tartas, M [Laboratoire de Physiologie et d' Explorations Vasculaires, Centre Hospitalier Universitaire d' Angers, 49033 Angers Cedex 01 (France); Abraham, P [Laboratoire de Physiologie et d' Explorations Vasculaires, Centre Hospitalier Universitaire d' Angers, 49033 Angers Cedex 01 (France); L' Huillier, J P [Ecole Nationale Superieure d' Arts et Metiers (ENSAM), Laboratoire Procedes Materiaux Instrumentation (LPMI), 2, boulevard du Ronceray, BP 3525, 49035 Angers Cedex (France)

2005-05-07

290

Non-invasive technique for assessment of vascular wall stiffness using laser Doppler vibrometry  

Science.gov (United States)

It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter is best known when estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery in the groin, but may also be determined locally from short-distance measurements on a short vessel segment. In this work, we propose a novel, non-invasive, non-contact laser Doppler vibrometry (LDV) technique for evaluating PWV locally in an elastic vessel. First, the method was evaluated in a phantom setup using LDV and a reference method. Values correlated significantly between methods (R ? 0.973 (p ? 0.01)); and a Bland-Altman analysis indicated that the mean bias was reasonably small (mean bias ? -2.33 ms). Additionally, PWV was measured locally on the skin surface of the CCA in 14 young healthy volunteers. As a preliminary validation, PWV measured on two locations along the same artery was compared. Local PWV was found to be between 3 and 20 m s-1, which is in line with the literature (PWV = 5-13 m s-1). PWV assessed on two different locations on the same artery correlated significantly (R = 0.684 (p < 0.01)). In summary, we conclude that this new non-contact method is a promising technique to measure local vascular stiffness in a fully non-invasive way, providing new opportunities for clinical diagnosing.

Campo, Adriaan; Segers, Patrick; Heuten, Hilde; Goovaerts, Inge; Ennekens, Guy; Vrints, Christiaan; Baets, Roel; Dirckx, Joris

2014-06-01

291

Resonant Doppler velocimeter  

Science.gov (United States)

Narrow linewidth tunable lasers augur a new kind of laser Doppler velocimetry employing resonant absorption and fluorescence from trace atomic species rather than scattering from particles. This technique may provide better turbulence and small volume information than present velocimetry.

Miles, R. B.

1975-01-01

292

High resolution Doppler lidar based on actively stabilized ring dye laser  

International Nuclear Information System (INIS)

A CW Doppler lidar has been developed. Heterodyne detection techniques are used for the recording of Doppler shifted collected backscattered signals induced by the motion of remote sources. The system has been tested for remote measurements of Doppler shifts due to rotating objects, aerosols and flowing liquids. Water and gaseous discharge flow rates have been measured remotely for simulation purposes. The system is capable of measuring Doppler shifts as low as 0.25 MHz corresponding to 0.1 m/sec velocities

293

Laser Doppler velocimeter measurements and laser sheet imaging in an annular combustor model. M.S. Thesis, Final Report  

Science.gov (United States)

An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.

Dwenger, Richard Dale

1995-01-01

294

Influence of coherent light on blood microcirculation in human oral cavity mucous membrane: an objective monitoring by laser photoplethysmography and Doppler flowmetry  

Science.gov (United States)

Integrated device for laser therapy and monitoring of blood microcirculation has been developed. Influence of laser irradiation on the statement of blood microcirculation in mucous membrane of human oral cavity has been investigated. Changes of blood saturation and velocity of blood microcirculation have been studied by methods of laser photoplethysmography and Doppler diagnostics. Influence of coherent light on the intensity of microcirculation in the capillary net of mucous membrane has been demonstrated directly during the short-time session of laser therapy.

Kharish, Natalia A.; Lepilin, Alexander V.; Lychagov, Vladislav V.; Safonkina, Elena V.; Sedykh, Alexey V.; Ulyanov, Sergey S.

2004-06-01

295

Flowmeter determines mix ratio for viscous adhesives  

Science.gov (United States)

Flowmeter determines mix ratio for continuous flow mixing machine used to produce an adhesive from a high viscosity resin and aliphatic amine hardener pumped through separate lines to a rotary blender. The flowmeter uses strain gages in the two flow paths and monitors their outputs with appropriate instrumentation.

Lemons, C. R.

1967-01-01

296

Design and operation of target flowmeters  

Science.gov (United States)

Target flowmeters are discussed. The principle of operation, design and construction, reliability, performance evaluation, ranging and pressure drop, rangeability and calibration, and signal conditioning and application of these instruments are examined. Representative data are given. Gas flow measurement with target flowmeter is discussed in an appendix.

Clark, W. T.

297

Doppler line shapes in the photolysis of laser excited, aligned molecules: Application to the vibrationally mediated photodissociation of HN3  

Science.gov (United States)

A general expression for the Doppler profile for fragments produced in the photodissociation of laser excited, aligned molecules, as in vibrationally mediated photodissociation (VMP), is presented. In contrast to one-photon dissociation, for which the Doppler profile depends only on the second moment of the fragment molecular-frame angular distribution, the profile in the case of VMP is sensitive to several moments of the angular distribution, up to k=4. In addition, the profile for a near-prolate molecule depends on the angle ?a between the electronic transition moment ? and the a inertial axis. This theory is applied to the analysis and interpretation of Doppler profiles in the laser fluorescence detection of NH(a 1?) fragments, of rotational angular momenta N=7 and 10, from the 532 nm VMP of HN3 excited to the second N-H stretch overtone level (3?1). For both ?-doublets of these rotational levels, the second moment of the molecular-frame angular distribution ?2,0= was found to be positive, in agreement with previous results for high-J fragments from one-photon photolysis of HN3. The profiles are consistent with a value of ˜0° for the angle ?a. These values for ?a and ?2,0 are inconsistent with simple expectations based on planar, prompt dissociation upon excitation to the lowest singlet excited state (1A?) and suggest the importance of nonplanar geometries in the dissociation dynamics.

Barnes, Rhett James; Sinha, Amitabha; Dagdigian, Paul J.; Lambert, H. Mark

1999-07-01

298

High Accuracy Fuel Flowmeter, Phase 1  

Science.gov (United States)

Technology related to aircraft fuel mass - flowmeters was reviewed to determine what flowmeter types could provide 0.25%-of-point accuracy over a 50 to one range in flowrates. Three types were selected and were further analyzed to determine what problem areas prevented them from meeting the high accuracy requirement, and what the further development needs were for each. A dual-turbine volumetric flowmeter with densi-viscometer and microprocessor compensation was selected for its relative simplicity and fast response time. An angular momentum type with a motor-driven, spring-restrained turbine and viscosity shroud was selected for its direct mass-flow output. This concept also employed a turbine for fast response and a microcomputer for accurate viscosity compensation. The third concept employed a vortex precession volumetric flowmeter and was selected for its unobtrusive design. Like the turbine flowmeter, it uses a densi-viscometer and microprocessor for density correction and accurate viscosity compensation.

Mayer, C.; Rose, L.; Chan, A.; Chin, B.; Gregory, W.

1983-01-01

299

Autonomous structural health monitoring technique for interplanetary drilling applications using laser Doppler velocimeters  

Science.gov (United States)

The research work presented in this thesis is devoted to the formulation and field testing of a dynamics-based structural health monitoring system for an interplanetary subsurface exploration drill system. Structural health monitoring is the process of detecting damage or other types of defects in structural and mechanical systems that have the potential to adversely affect the current or future performance of these systems. Interplanetary exploration missions, specifically to Mars, involve operations to search for water and other signs of extant or past life. Such missions require advanced robotic systems that are more susceptible to structural and mechanical failures, which motivates a need for structural health monitoring techniques relevant to interplanetary exploration systems. Strict design requirements for interplanetary exploration missions create unique research problems and challenges compared with structural health monitoring procedures and techniques developed to date. These challenges include implementing sensors and devices that will not interfere with the drilling operation, producing "real-time" diagnostics of the drilling condition, and developing an automation procedure for complete autonomous operations. The first research area involves modal analysis experiments to understand the dynamic characteristics of interplanetary drill structural systems in operation. These experiments also validate the use of Laser Doppler Velocimeter sensors in real-time structural health monitoring and prove the drill motor system adequately excites the drill for dynamic measurements and modal analysis while the drill is in operation. The second research area involves the development of modal analysis procedures for rotating structures using a Chebyshev signal filter to remove harmonic component and other noise from the rotating drill signal. This filter is necessary to accurately analyze the condition of the rotating drill auger tube while in operation. The third research area involves the development of structural dynamic models to represent the drill system under nominal and expected drilling fault conditions. These models are compared with the modal analysis experimental results and provide theoretical means to analyze the drilling operation and predict fault conditions. The fourth research area involves the formulation of a complete autonomous system to collect and perform the dynamic analysis of the drill signal, identify fault-diagnostic results, and relay these results to the drill Executive computer. The formulated system includes the signal filter, trained Neural Networks, and an automation procedure. Trained Neural Networks are implemented to provide a rapid-response method of relating and comparing the current drill signal with the fault-based structural dynamic models developed in this thesis. Lastly, an automation procedure, and the corresponding software, is developed to interface the measurement equipment, signal filter, Neural Networks, and drill Executive computer to provide a complete hands-off operation of the structural health monitoring system. The fifth research area involves field testing and validation of the developed structural health monitoring system through three field campaigns. Two of these field campaigns were completed at a Mars-analog site in the Canadian Arctic. The automated dynamics-based structural health monitoring technique developed in this thesis presents advanced research accomplishments leading to real-time, autonomous structural health monitoring, and it has been successfully demonstrated on an operating dynamic system. Other major contributions of this thesis work include the formulation and demonstration of real-time, autonomous structural health monitoring in rotating structures using Laser Doppler Velocimeter sensors.

Statham, Shannon M.

300

A laser-lock concept to reach cm/s-precision in Doppler experiments with Fabry-Perot wavelength calibrators  

CERN Document Server

State-of-the-art Doppler experiments require wavelength calibration with precision at the cm/s level. A low-finesse Fabry-Perot interferometer (FPI) can provide a wavelength comb with a very large bandwidth as required for astronomical experiments, but unavoidable spectral drifts are difficult to control. Instead of actively controlling the FPI cavity, we propose to passively stabilize the interferometer and track the time-dependent cavity length drift externally. A dual-finesse cavity allows drift tracking during observation. The drift of the cavity length is monitored in the high-finesse range relative to an external standard: a single narrow transmission peak is locked to an external cavity diode laser and compared to an atomic frequency. Following standard locking schemes, tracking at sub-mm/s precision can be achieved. This is several orders of magnitude better than currently planned high-precision Doppler experiments. It allows freedom for relaxed designs rendering this approach particularly interesting...

Reiners, A; Ulbrich, R G

2014-01-01

 
 
 
 
301

Laser-Doppler-measurements of power-density-spectra in a turbulent channel flow  

International Nuclear Information System (INIS)

In this paper the results of measurements in a turbulent channel flow are presented. A Laser-Doppler-Anemometer is used. The fluid is water. The velocity component in the direction of the main flow and one component perpendicular to it are recorded. Both the Reynolds-number and the distance to the wall are varied. Particularly, the power-density-spectra of the velocity fluctuations are evaluated. These spectra are investigated in details distinguishing three different wavenumber ranges. The range of lower wavenumbers, respectively frequencies are presented by an approximation equation, and an empirical length-scale appearing in that equation is determined. A subrange having an -1-exponent is also investigated. The theoretically predicted shape of the spectrum in the intermediate wavenumber range is verified by the measurements. The two wavenumbers representing the lower respectively the upper limit of that range are determined as a function of Reynolds-number. In the upper range, the spectra are contaminated by a significant amount of noise which is shown to be a consequence of the measurement-method itself. The reasons and possible method to eliminate the noise are discussed. The spectral variation of the energy ratio for the different velocity directions and the existence of isotropy were considered. The results are spectra in a Reynolds-number range where the validity of the common 'universal' relations cannot be generally assumed. The deductions can be used to support models which are employed for the numerical simulation of turbulent flows and which require the knowledge of power-density-spectra. (orig.)

302

Experimental investigation of a vertical planar jet by ultrasound and laser Doppler velocimetry  

International Nuclear Information System (INIS)

An experimental investigation on the velocity field of a water-jet injected vertically into a water pool was conducted. The jet flowed from a thin rectangular nozzle and was considered to be quasi-planar as it was confined along two parallel planes. Velocity measurements of the jet and the surrounding entrained flow regions were made respectively by ultrasound and laser Doppler velocimetries (UDV and LDV). In contrast to LDV, UDV operates on the principle of pulsed ultrasound echography and in our experiment, a single transducer held at a 10deg angle with respect to horizontal (x-axis) was vertically traversed. The measured velocity thus represents the velocity component along this beam angle. The hydraulic diameter (D) based Reynolds numbers of flow were, Re=1.79 x 104 (UDV), 3.58 x 104 (LDV), 7.15 x 104 (LDV), corresponding to average exit velocities of 0.5, 1.0 and 2.0 m/s. Comparisons of the traditional jet parameters, such as the decay of the centerline and jet's half-radius vs. axial distance (z-axis), against established data confirmed proper jet-like behavior of our test facility. The conclusions from the experiments were as follows: (1) that UDV shows trends and magnitudes similar to data obtained by LDV; both velocimetry methods are applicable to this type of experimental flow configuration, (2) data presented as the axial decay of centerline velocity and jet half-radius, are consistent and similar to past experimental data, mostly of gas jets, and (3) radial profiles show agreement with a past correlation up to R/R1/2=1. There are differences however, between the correlation and the data, for R/R1/2?1, the latter which were showed consistent trends. (author)

303

Influence of pulsatility on the development of intracardiac jets: an in vitro laser Doppler study.  

Science.gov (United States)

So far, it has been hypothesized that numerical data obtained in steady flow conditions apply to pulsatile flows. In order to study the modifications of the velocity fields due to pulsatility, jets were produced by 8 orifices (with a diameter "D" of 4.4 to 11.3 mm) included in a chamber of 50 mm. The velocity was measured using laser Doppler anemometry with a pulsatile flow ("pf") and compared to the values obtained in steady ("sf"): at maximum velocity, the longitudinal velocity profile is qualitatively similar to this observed in steady flow: it is made of a plateau followed by an hyperbolic velocity decay in the turbulent area. The length of the core ("Lpf") is strongly related to "D" (Lpf = 3.72 D + 5.49, r = .99) and the velocity decay depends on the ratio between the distance "x" from the orifice and "D" (V/Vo = 2.83D/x + 3.46, r = .85, where V is the velocity at "x" and Vo the initial velocity). During the acceleration and the deceleration, the laminar core is disturbed by turbulences. The comparison of "pf" data with "sf" data demonstrated similar diameters at the origin of the jets (Dpf = 0.96 Dsf + .12, r = .99), but significant (p less than .0001) differences both for "L" and "V/Vo": Lpf = .91Lsf + 6.58, r = .97, V/Vopf = .63 V/Vosf + .34, r = .76. Thus, pulsatility modifies velocity fields and the results obtained in steady flow conditions do not apply to pulsatile jets. PMID:1834246

Diebold, B; Delouche, A; Abergel, E; Delouche, P; Dumée, P; Péronneau, P

1991-01-01

304

A performance study of a laser Doppler vibrometer for measuring waveforms from piezoelectric transducers.  

Science.gov (United States)

The stresses at transducer contacts were estimated from accurate particle velocity measurements by using a laser Doppler vibrometer (LDV). We then evaluated the performance of LDV for ultrasonic waveform measurements in physical model experiments that are employed for modeling seismic observations. For such experiments, the characteristics of the source and detector should be exactly known. Disc-shaped compression and shear-mode piezoelectric transducers were attached on a flat surface of a steel semicircular column, and ultrasonic waves were excited by single-shot sine waves with 0.25, 0.5, and 1 MHz frequencies. Radial and transverse components were measured by LDV at a distance of 150 mm from the source. The maximum amplitudes of waves with respect to radiation angle give a radiation pattern of a transducer. Each observed radiation pattern was fitted to the calculated radiation pattern by assuming a harmonically oscillating stress distributed uniformly on a flat circular area. The observed radiation patterns show fairly good agreement with the calculated radiation patterns for both radial and transverse components when the source frequencies are 0.25 and 0.5 MHz. Because the best-fit stress values were independently estimated from the radial and the transverse radiation patterns, the 2 stress values should be equal for each source and frequency. The discrepancy between the estimated radial and transverse stress values becomes larger as the source frequency increases. Provided that coincidence of the 2 stress values indicates the validity of waveform measurements, the results suggest that LDV is applicable for measuring the 3-D particle-velocity at frequencies up to 0.5 MHz. PMID:19574154

Fukushima, Yo; Nishizawa, Osamu; Sato, Haruo

2009-07-01

305

Aerodynamic particle size measurement by laser--Doppler velocimetry. Publication number 343  

Energy Technology Data Exchange (ETDEWEB)

A method of measuring the aerodynamic diameter of aerosol particles was investigated. The method consists of accelerating particles in a coverging nozzle and measuring their velocities near the exit of th nozzle with a laser--Doppler velocimeter. The experimental studies utilized a test nozzle with a converging angle of approximately 15/sup 0/ and an exit diameter of about .1 cm. The pressure drop across the nozzle was varied from 2.54 to 276 cm of H/sub 2/O, and particle velocity was observed to vary from approximately 0.5 to 1.0 times the gas velocity at the exit of the nozzle. A theoretical analysis utilized boundary layer theory to predict the velocity of the gas in the nozzle, and then the equations of particle motion were integrated to give the theoretical particle velocities. These values agreed with the experimental values to within a few percent. The effects of nozzle geometry, flow rate, particle density, and particle size were studied using the results of calculations made with dimensionless equations. The velocity of a particle in a given nozzle and flow depends upon the aerodynamic diameter of the particle and the particle density. The geometry and flow can be chosen to minimize the effect of particle density. Assuming that the density of particles in the atmosphere ranges from 1 g/cm/sup 3/ to 3 g/cm/sup 3/, the aerodynamic diameter of particles can be measured with an uncertainty of +- 10% in the size range from .5 ..mu..m to 10 ..mu..m.

Wilson, J.C.

1977-12-01

306

Studies on a Laser Doppler Interferometry gravity mission by a semi-analytical approach  

Science.gov (United States)

In the last decade, three satellite missions (CHAMP, GRACE and GOCE) have been successfully launched for the Earth gravity field observation from space. In particular, GOCE will provide a very accurate static model in terms of spherical harmonic expansion up to degree 200 and beyond, while GRACE is more sensible to time variations of the gravity field at lower resolution. A possible goal for a future mission is to measure both gravity and its variations at high resolution. This can be reached by a GRACE-like mission concept, with GOCE-quality accelerometers on board and a link between the two co-orbiting satellites based on a Laser Doppler Interferometer. In 2005 an early study on this future mission was conducted by Thales Alenia Space, leading to the definition of a possible mission profile. In that study a time-wise approach was used with the approximation of considering separately each harmonic degree of the potential in the Fourier solution of the Hill equations. This was done to obtain a fully analytical solution. In this work this approximation has been removed and the error budget of the mission has been recomputed by a semi-analytical approach. It comes out that the main effect of the approximation was in the zonal harmonics, meaning that the effect of polar gaps due to the orbit inclination was underestimated. For the other coefficients the degradation was of one order of magnitude at most, especially at low-medium harmonic degrees. An alternative mission profile based on two couples of satellites flying on two orbits with different inclination is also evaluated.

Lisa, Pertusini; Mirko, Reguzzoni; Fernando, Sansò

2010-05-01

307

Sub-Doppler resolution laser-induced nuclear orientation of 85mRb (t1/2=1.0 ?s)  

International Nuclear Information System (INIS)

We report the first observation of sub-Doppler resolved gamma anisotropy produced by Laser Induced Nuclear Orientation (LINO). The anisotropy was produced by laser optical pumping the D1 transition of the 1?s 85mRb isomer. (orig./WL)

308

Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry  

Science.gov (United States)

We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s-1 impacts with transparent target materials. Laser-launching Al flyers 25-100 ?m thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns.

Curtis, Alexander D.; Banishev, Alexandr A.; Shaw, William L.; Dlott, Dana D.

2014-04-01

309

Laser-driven flyer plates for shock compression science: launch and target impact probed by photon Doppler velocimetry.  

Science.gov (United States)

We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s(-1) impacts with transparent target materials. Laser-launching Al flyers 25-100 ?m thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns. PMID:24784627

Curtis, Alexander D; Banishev, Alexandr A; Shaw, William L; Dlott, Dana D

2014-04-01

310

Low flow vortex shedding flowmeter  

Science.gov (United States)

The purpose was to continue a development project on a no moving parts vortex shedding flowmeter used for flow measurement of hypergols. The project involved the design and construction of a test loop to evaluate the meter for flow of Freon which simulates the hypergol fluids. Results were obtained on the output frequency characteristics of the flow meter as a function of flow rate. A family of flow meters for larger size lines and ranges of flow was sized based on the results of the tested meter.

Waugaman, Charles J.

1989-01-01

311

Comparison between /sup 133/Xenon washout technique and Laser Doppler flowmetry in the measurement of local vasoconstrictor effects on the microcirculation in subcutaneous tissue and skin  

Energy Technology Data Exchange (ETDEWEB)

Changes in skin blood flow measured by Laser Doppler flowmetry and changes in subcutaneous blood flow measured by /sup 133/Xenon washout technique were compared during activation of the local sympathetic mediated veno-arteriolar vaso-constrictor reflex by lowering the area of investigation below heart level. The measurements were performed in tissue with and without sympathetic innervation. In five subjects, who all had been cervically sympathectomized for manual hyperhidrosis, the Laser Doppler and /sup 133/Xenon blood flow measurements were performed simultaneously on the sympathetically denervated forearm, and on the calf with preserved sympathetic nerve supply. The Laser Doppler method registered a 23% reduction in skin blood flow during lowering of the extremities independently of the sympathetic nerve supply to the skin. The /sup 133/Xenon method recorded a 44% decrease in blood flow in innervated and unchanged blood flow in denervated subcutaneous tissue during lowering of the extremities. Our results indicate that the Laser Doppler method and /sup 133/Xenon method are not comparable, and that the Laser Doppler method is not useful in measuring local sympathetic mediated blood flow changes.

Kastrup, J.; Buelow, J.; Lassen, N.A.

1987-10-01

312

Microsurgical laser Doppler probe for simultaneous intraoperative monitoring of cochlear blood flow and electrocochleography from the round window  

Science.gov (United States)

The aim of this project is the development of a microsurgical laser Doppler (LD) probe that simultaneously monitors blood flow and Electrocochleography (ECochG) from the round window of the ear. The device will prevent neurosensory hearing loss during acoustic neuroma surgery by preventing damage to the internal auditory nerve and to the cochlear blood flow supply. A commercially available 0.5 mm diameter Laser-Doppler velocimetry probe (LaserFlo, Vasamedics) was modified to integrate an ECochG electrode. A tube for suction and irrigation was incorporated into a sheath of the probe shaft, to facilitate cleaning of the round window (RW) and allow drug delivery to the round window membrane. The prototype microprobe was calibrated on a single vessel model and tested in vivo in a rabbit model. Preliminary results indicate that the microprobe was able to measure changes in cochlear blood flow (CBF) and ECochG potentials from the round window of rabbits in vivo. The microprobe is suitable for monitoring cochlear blood flow and auditory cochlear potentials during human surgery.

Abiy, Lidet; Telischi, Fred; Parel, Jean-Marie A.; Manns, Fabrice; Saettele, Ralph; Morawski, Krzysztof; Ozdamar, Ozcan; Borgos, John; Delgado, Rafael; Miskiel, Edward; Yavuz, Erdem

2003-06-01

313

Continuous-scanning laser Doppler vibrometry: Extensions to arbitrary areas, multi-frequency and 3D capture  

Science.gov (United States)

To date, differing implementations of continuous scan laser Doppler vibrometry have been demonstrated by various academic institutions, but since the scan paths were defined using step or sine functions from function generators, the paths were typically limited to 1D line scans or 2D areas such as raster paths or Lissajous trajectories. The excitation was previously often limited to a single frequency due to the specific signal processing performed to convert the scan data into an ODS. In this paper, a configuration of continuous-scan laser Doppler vibrometry is demonstrated which permits scanning of arbitrary areas, with the benefit of allowing multi-frequency/broadband excitation. Various means of generating scan paths to inspect arbitrary areas are discussed and demonstrated. Further, full 3D vibration capture is demonstrated by the addition of a range-finding facility to the described configuration, and iteratively relocating a single scanning laser head. Here, the range-finding facility was provided by a Microsoft Kinect, an inexpensive piece of consumer electronics.

Weekes, B.; Ewins, D.; Acciavatti, F.

2014-05-01

314

New applications of scanning laser Doppler vibrometry (SLDV) to nondestructive diagnosis of artwork: mosaics, ceramics, inlaid wood, and easel painting  

Science.gov (United States)

During the last years the growing importance of the correct determination of the state of conservation of artworks has been stated by all personalities in care of Cultural Heritage. There exist many analytical methodologies and techniques to individuate the physical and chemical characteristics of artworks, but at present their structural diagnostics mainly rely on the expertise of the restorer and the typical diagnostic process is accomplished mainly through manual and visual inspection of the object surface. The basic idea behind the proposed technique is to substitute human senses with measurement instruments: surfaces are very slightly vibrated by mechanical actuators, while a laser Doppler vibrometer scans the objects measuring surface velocity and producing 2D or 3D maps. Where a defect occurs velocity is higher than neighboring areas so defects can be easily spotted. Laser vibrometers also identify structural resonance frequencies thus leading to a complete characterization of defects. This work will present the most recent results coming out of the application of Scanning Laser Doppler Vibrometers (SLDV) to different types of artworks: mosaics, ceramics, inlaid wood and easel painting. Real artworks and samples realized on purpose have been studied using the proposed technique and different measuring issues resulting from each artwork category will be described.

Castellini, Paolo; Esposito, Enrico; Marchetti, Barbara; Paone, Nicola; Tomasini, Enrico P.

2001-10-01

315

Non-mechanical scanning laser Doppler velocimetry with sensitivity to direction of transverse velocity component using optical serrodyne frequency shifting  

Science.gov (United States)

This paper proposes a non-mechanical axial scanning laser Doppler velocimeter (LDV) with sensitivity to the direction of the transverse velocity component using optical serrodyne frequency shifting. Serrodyne modulation via the electro-optic effect of a LiNbO3 (LN) phase shifter is employed to discriminate the direction of the transverse velocity component. The measurement position is scanned without any moving mechanism in the probe by changing the wavelength of the light input to the probe. The experimental results using a sensor probe setup indicate that both the scan of the measurement position and the introduction of directional sensitivity are successfully demonstrated.

Maru, Koichi; Watanabe, Kento

2014-05-01

316

Development and application of a three-dimensional laser Doppler velocimeter system to internal and external flows  

International Nuclear Information System (INIS)

A three-dimensional, tri-orthogonal, two-color, and Bragg-diffracted laser Doppler velocimeter system has been developed to measure simultaneously the three components of local mean velocity (u, v, w) and the associated turbulent quantities. The system is designed to measure flow parameters in very complex and highly three-dimensional, in both the mean-flow and the turbulent structure, internal and external flows. The developed system has successfully used to study the secondary motions by both the Reynolds-stress gradients and pressure gradients, corner flows, and turbulent boundary layer flow cases. 8 refs

317

Effect of clenbuterol on cardiopulmonary parameters and intramuscular blood flow by laser Doppler flowmetry in anesthetized ponies  

Science.gov (United States)

The cardiopulmonary affects and the affects on muscular microperfusion of the beta adrenergic agonist, clenbuterol (0.8 mcg/kg intravenously), were investigated in dorsally recumbent anesthetized ponies. Muscle microcirculation was measured by laser Doppler flowmetry, utilizing fine optical fiber probes. Other measurements included heart rate, cardiac output, arterial blood pressure, and arterial blood gas tensions. Clenbuterol injection caused a regular, but transitory rise in muscle microcirculation, an increase in heart rate, and cardiac output and a decrease in mean arterial blood pressure. Clenbuterol did appear to prevent the continuing fall in arterial blood oxygen tensions seen in the treatment groups, but had only minimal affects in reversing the hypoxia already present.

Lee, Yong H.; Clarke, Kathleen W.; Alibhai, Hatim I. K.

1994-09-01

318

A laser-lock concept to reach cm s-1-precision in Doppler experiments with Fabry-Pérot wavelength calibrators  

Science.gov (United States)

State-of-the-art Doppler experiments require wavelength calibration with precision at the cm s-1 level. A low-finesse Fabry-Pérot interferometer (FPI) can provide a wavelength comb with a very large bandwidth as required for astronomical experiments, but unavoidable spectral drifts are difficult to control. Instead of actively controlling the FPI cavity, we propose to passively stabilize the interferometer and track the time-dependent cavity length drift externally using the 87Rb D2 atomic line. A dual-finesse cavity allows drift tracking during observation. In the low-finesse spectral range, the cavity provides a comb transmission spectrum tailored to the astronomical spectrograph. The drift of the cavity length is monitored in the high-finesse range relative to an external standard: a single narrow transmission peak is locked to an external cavity diode laser and compared to an atomic frequency from a Doppler-free transition. Following standard locking schemes, tracking at sub-mm s-1 precision can be achieved. This is several orders of magnitude better than currently planned high-precision Doppler experiments, and it allows freedom for relaxed designs including the use of a single-finesse interferometer under certain conditions. All components for the proposed setup are readily available, rendering this approach particularly interesting for upcoming Doppler experiments. We also show that the large number of interference modes used in an astronomical FPI allows us to unambiguously identify the interference mode of each FPI transmission peak defining its absolute wavelength solution. The accuracy reached in each resonance with the laser concept is then defined by the cavity length that is determined from the one locked peak and by the group velocity dispersion. The latter can vary by several 100 m s-1 over the relevant frequency range and severely limits the accuracy of individual peak locations, although their interference modes are known. A potential way to determine the absolute peak positions is to externally measure the frequency of each individual peak with a laser frequency comb (LFC). Thus, the concept of laser-locked FPIs may be useful for applying the absolute accuracy of an LFC to astronomical spectrographs without the need for an LFC at the observatory.

Reiners, A.; Banyal, R. K.; Ulbrich, R. G.

2014-09-01

319

Improvements in or relating to vortex-shedding fluid flowmeters  

International Nuclear Information System (INIS)

A fluid flowmeter has a conduit and an obstacle in the fluid flow which extends to outside the conduit. Successive vortices break away from the obstacle transmitting movement to the obstacle outside the conduit. This movement is sensed e.g. by a laser interferometer or a piezoelectric sensor which may be outside a containment wall. The obstacle may be symmetrical in a cross-section taken parallel to the flow and eg of rectangular or circular shape or it may be of semi-circular cross-section. (author)

320

Time-resolved fuel injector flow characterisation based on 3D laser Doppler vibrometry  

Science.gov (United States)

Hydrodynamic turbulence and cavitation are known to play a significant role in high-pressure atomizers, but the small geometries and extreme operating conditions hinder the understanding of the flow’s characteristics. Diesel internal flow experiments are generally conducted using x-ray techniques or on transparent, and often enlarged, nozzles with different orifice geometries and surface roughness to those found in production injectors. In order to enable investigations of the fuel flow inside unmodified injectors, we have developed a new experimental approach to measure time-resolved vibration spectra of diesel nozzles using a 3D laser vibrometer. The technique we propose is based on the triangulation of the vibrometer and fuel pressure transducer signals, and enables the quantitative characterisation of quasi-cyclic internal flows without requiring modifications to the injector, the working fluid, or limiting the fuel injection pressure. The vibrometer, which uses the Doppler effect to measure the velocity of a vibrating object, was used to scan injector nozzle tips during the injection event. The data were processed using a discrete Fourier transform to provide time-resolved spectra for valve-closed-orifice, minisac and microsac nozzle geometries, and injection pressures ranging from 60 to 160?MPa, hence offering unprecedented insight into cyclic cavitation and internal mechanical dynamic processes. A peak was consistently found in the spectrograms between 6 and 7.5?kHz for all nozzles and injection pressures. Further evidence of a similar spectral peak was obtained from the fuel pressure transducer and a needle lift sensor mounted into the injector body. Evidence of propagation of the nozzle oscillations to the liquid sprays was obtained by recording high-speed videos of the near-nozzle diesel jet, and computing the fast Fourier transform for a number of pixel locations at the interface of the jets. This 6–7.5?kHz frequency peak is proposed to be the natural frequency for the injector’s main internal fuel line. Other spectral peaks were found between 35 and 45?kHz for certain nozzle geometries, suggesting that these particular frequencies may be linked to nozzle dependent cavitation phenomena.

Crua, Cyril; Heikal, Morgan R.

2014-12-01

 
 
 
 
321

Smart ultrasonic flowmeter used for the operation support of water resource management in the agricultural areas  

Science.gov (United States)

Ultrasonic sensors transmit acoustic waves and receive them later. This is done by ultrasonic transducers, which transform an ultrasonic wave into an electrical signal and vice versa. Often, it is possible to use the same transducer for both transmitting and receiving. The most important parts of any ultrasonic sensor are the transducers. The spectral and spatial radiation characteristics of these components are the prime determinants of sensor performance. Such transducers must have a robust design, stable radiation pattern (high directivity) and good receiving sensitivity. Intelligent ultrasonic sensors have the possibility to extract the information about the variables to be measured, carried by the ultrasonic signals efficiently and with accuracy. To achieve this performance, the signals are processed by dedicated hardware (accurate electronic measuring devices). Ultrasound has the property, that its velocity is strongly affected by the flow velocity of the fluids in which it propagates. The ultrasonic flowmeters have gained a lot of attention over the past few years; they have several advantages over the differential pressure flowmeter, turbine meters, coriolis meters and vortex meters. They are widely used to measure the flow of liquids, first, they are either less intrusive (wetted flowmeter) or non-intrusive (clamp-on flowmeter), depending on the model. Also, they don't have moving parts that are subject to wear over time, and with minimum obstruction of the flow. Ultrasonic flowmeter are not limited to clean liquids (Transit time flowmeter), a special type of ultrasonic flowmeter can also accurately measure the flow of slurries and liquids with many impurities (Doppler flowmeter). This part of paper describes the intelligent ultrasonic sensor. The conception or the realization of intelligent ultrasonic sensor requires the synthesis of several technologies, a knowledge in the fields of sensor, digital ultrasonic signal processing, distributed system and networks. This new generation of devices is used in agricultural field (irrigation monitoring), based on transit-time principle with single-path or multi-path scheme. Finally, the goals of this work consist in integrating the smart sensor into irrigation systems monitoring in order to evaluate potential advantages and demonstrate their performance, on the other hand, to understand and use ultrasonic approach for determining flow characteristics and improving flow measurements by reducing errors caused by disturbances of the flow profiles.

Elmostafa, Ziani; Mustapha, Bennouna; Boissier, Raymond

2008-10-01

322

Laser Doppler vibrometry on rotating structures in coast-down: resonance frequencies and operational deflection shape characterization  

Science.gov (United States)

In rotating machinery, variations of modal parameters with rotation speed may be extremely important in particular for very light and undamped structures, such as helicopter rotors or wind turbines. The natural frequency dependence on rotation speed is conventionally measured by varying the rotor velocity and plotting natural frequencies versus speed in the so-called Campbell diagram. However, this kind of analysis does not give any information about the vibration spatial distribution i.e. the mode shape variation with the rotation speed must be investigated with dedicated procedures. In several cases it is not possible to fully control the rotating speed of the machine and only coast-down tests can be performed. Due to the reduced inertia of rotors, the coast-down process is usually an abrupt transient and therefore an experimental technique, able to determine operational deflection shapes (ODSs) in short time, with high spatial density and accuracy, appears very promising. Moreover coast-down processes are very difficult to control, causing unsteady vibrations. Hence, a very efficient approach for the rotation control and synchronous acquisition must be developed. In this paper a continuous scanning system able to measure ODSs and natural frequencies excited during rotor coast-down is shown. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the rotor surface, in order to measure the ODS, and to follow the rotation of the rotor itself even in coast-down. With a single measurement the ODSs can be recovered from the LDV output time history in short time and with huge data saving. This technique has been tested on a laboratory test bench, i.e. a rotating two-blade fan, and compared with a series of non-contact approaches based on LDV: traditional experimental modal analysis (EMA) results obtained under non-rotating conditions by measuring on a sequence of points on the blade surface excited by an impact hammer, continuous scanning LDV measuring the ODS of the structure excited by an impact hammer modulating the laser output, tracking laser Doppler vibrometry (TLDV) operating at different rotation speeds under stationary conditions, tracking continuous scanning laser Doppler vibrometry (TCSLDV) operating at different rotation speeds under stationary conditions. EMA and TLDV have been performed over the same grid of points sufficiently dense to have ODSs with adequate spatial resolution, it requiring long measurement time. The application of different techniques allowed us to completely characterize the tested bladed rotor and to validate the continuous scanning application to transient rotator processes.

Martarelli, M.; Castellini, P.; Santolini, C.; Tomasini, E. P.

2011-11-01

323

Scanning Laser Doppler Vibrometer Measurements Inside Helicopter Cabins in Running Conditions: Problems and Mock-up Testing  

International Nuclear Information System (INIS)

The present work deals with the analysis of problems and potentials of laser vibrometer measurements inside helicopter cabins in running conditions. The paper describes the results of a systematic measurement campaign performed on an Agusta A109MKII mock-up. The aim is to evaluate the applicability of Scanning Laser Doppler Vibrometer (SLDV) for tests in simulated flying conditions and to understand how performances of the technique are affected when the laser head is placed inside the cabin, thus being subjected to interfering inputs. Firstly a brief description of the performed test cases and the used measuring set-ups are given. Comparative tests between SLDV and accelerometers are presented, analyzing the achievable performances for the specific application. Results obtained measuring with SLDV placed inside the helicopter cabin during operative excitation conditions are compared with those performed with the laser lying outside the mock-up, these last being considered as 'reference measurements'. Finally, in order to give an estimate of the uncertainty level on measured signals, a study linking the admitted percentage of noise content on vibrometer signals due to laser head vibration levels will be introduced.

324

Design and evaluation of a short coherence length laser-based Doppler wind Lidar system for wind energy applications  

Science.gov (United States)

Nowadays larger horizontal axis wind turbines (HAWT) are setup in difficult to access locations adding an overhead to the production cost as well as the Operation & Maintenance (O&M) costs. In order to cover those overhead cost, Lidar assisted preview control of wind turbine blade pitch system is prosperous both on research and industry applications. However, there are not a lot of choices to remote sense the wind field inflow. Doppler wind Lidar systems have been proved to be advantageous on such applications. However due to the economical consideration, the state-of-the-art wind Lidar systems are only limited on research. Therefore, developing a cost efficient wind Lidar to support the pitch control of HAWT to reduce the material requirement, lower the O&M cost and decrease the cost of energy (COE) in the long term is our motivation. Our current main focusing of investigations has been laid on the optical design of emitting and receiving system, and the evaluation of the low cost laser system instead of using a high cost fiber laser as a transmitter. The short coherence length lasers brings a higher phase noise into the detection, normally it is not used for the coherent Lidars system. However, such a laser can achieve a higher output power with a low cost which is very important for the market. In order to bring such kind of laser into the application, different sending, receiving, and detection design is simulated and tested. Those testing results are presented in this paper.

Shinohara, Leilei; Asche-Tauscher, Julian; Fox, Maik; Beuth, Thorsten; Stork, Wilhelm

2014-05-01

325

Development of a wireless sensor for the measurement of chicken blood flow using the laser Doppler blood flow meter technique.  

Science.gov (United States)

Here, we report the development of an integrated laser Doppler blood flow micrometer for chickens. This sensor weighs only 18 g and is one of the smallest-sized blood flow meters, with no wired line, these are features necessary for attaching the sensor to the chicken. The structure of the sensor chip consists of two silicon cavities with a photo diode and a laser diode, which was achieved using the microelectromechanical systems technique, resulting in its small size and significantly low power consumption. In addition, we introduced an intermittent measuring arrangement in the measuring system to reduce power consumption and to enable the sensor to work longer. We were successfully able to measure chicken blood flow for five consecutive days, and discovered that chicken blood flow shows daily fluctuations. PMID:23362244

Nishihara, Kei; Iwasaki, Wataru; Nakamura, Masaki; Higurashi, Eiji; Soh, Tomoki; Itoh, Toshihiro; Okada, Hironao; Maeda, Ryutaro; Sawada, Renshi

2013-06-01

326

Detailed study of the Fourier transform of the time-interval photon statistics distribution applied to laser Doppler velocimetry  

Energy Technology Data Exchange (ETDEWEB)

In this paper a technique consisting of measuring the Fourier transform Q/sub F/ of the time-interval photon statistics distribution is studied when applied to laser Doppler velocimetry. It is supposed that a device that changes the Gaussian intensity profile of the laser beam into a uniform intensity profile is used. A theoretical model for a fluid with a constant velocity is obtained and verified by two ways: experimentally and by a computer-simulation method. Then the experimental conditions for which the signal can be approached to a Lorentzian curve and the error involved in the determination of the fluid velocity are studied from the theoretical model. It is concluded that the measurement of Q/sub F/ is a useful technique for very low intensities.

Rebolledo, M.A.; Alvarez, J.M.; Amare, J.C.

1988-09-15

327

Modelling and experimental analysis of the performance of a laser Doppler vibrometer used to measure vibrations through combustive flows  

Science.gov (United States)

The problem of measuring surface vibrations by a laser Doppler vibrometer operating with the measuring beam across a combustive flow is discussed, in order to assess the possibility of experimentally determining the dynamic behaviour of a burner under operating conditions. The instrument performance is analysed in terms of interfering and modifying inputs through the development of a model of the interferometer and by experimental validation of its predictions. Experiments are carried out on an unconfined CH 4 flame of a Bunsen burner and a metal surface under a known forced vibration. The laser vibrometer output is influenced by the presence of the flame: major effects are optical path length variations of the measuring arm of the interferometer and beam movements. All effects occur at the typical flame flickering frequency and cause a distorted vibration spectra and a reduced signal-to-noise ratio. Beam wandering and defocusing are documented by image acquisition.

Paone, Nicola; Revel, Gian Marco

1998-08-01

328

ECG-triggering of the laser Doppler signal: an approach for perfusion imaging on the beating calf heart  

Science.gov (United States)

Laser Doppler perfusion imaging (LDPI) has successfully been used to map the myocardial perfusion on patients undergoing coronary bypass surgery on the arrested heart. The need for intra-operative evaluation of graft function is obvious in routine surgery but even more imperative when adapting new surgical techniques where the procedure is performed on the beating heart. When using LDPI on the beating heart, artifacts originating from the movement of the heart are superimposed on the Doppler signal. We have investigated a method to reduce these artifacts by controlling the sampling sequence with ECG-triggering. The method has been assessed in an animal model on the beating calf heart. After sternotomy, an area covering 1 cm2 was imaged at the anterior wall of the left ventricle. In this area, six perfusion images were captured each of them recorded at fixed, but different time intervals in the cardiac cycle. In addition continuous measurements at one spot was done during 1 - 2 minutes. The signal recorded during pumping action was high compared to measurements performed in the same muscle area during infusion of blood with a syringe pump. Repeated measurements captured at a fixed delay time from the R-peak in the same areas at the same heart frequency showed reproducibility. ECG-triggering of the laser Doppler signal is the first step in our attempts to adapt LDPI to enabling assessment of myocardial perfusion on the beating heart. Further technical achievements and in-vivo investigations are, however, needed and will be performed by our research team in future studies.

Wardell, Karin; Karlsson, Daniel M.; Loenn, Urban; Traff, Stefan; Casimir-Ahn, Henrik

2001-06-01

329

Laser Radar Range-Doppler Imaging and Simulation on High-speed Target  

Energy Technology Data Exchange (ETDEWEB)

On the basic of the representation of the principle of Doppler imaging, an echo model of high-speed target illuminated by broadband linear frequency modulated (LFM) signal was established in this paper. For high-speed target, because of its nonlinear echo phase and time-varying Doppler frequency shift, the Doppler spectrum of the target acquired by the traditional Fourier method was ambiguous, and the same in the radar images of the target. Therefore, an adaptive Wigner-Ville time-frequency analysis method was presented in the paper, that is, the local fuzzy function could be obtained by applying the two-dimensional adding Window Fourier Transform to signal's Wigner-Ville distribution, which made the kernel function, not only be adaptive to time, but also to the frequency. Finally, the simulation results show that the method has a good time-frequency concentration, and effectively control the cross-term interference.

Guo Hualing; Deng Jiahao; Cai Kerong, E-mail: guohualing@nuc.edu.cn [National Key Laboratory for Mechatronics Engineering and Control, Beijing Institute of Technology, Beijing 100081 (China)

2011-02-01

330

Laser Radar Range-Doppler Imaging and Simulation on High-speed Target  

Science.gov (United States)

On the basic of the representation of the principle of Doppler imaging, an echo model of high-speed target illuminated by broadband linear frequency modulated (LFM) signal was established in this paper. For high-speed target, because of its nonlinear echo phase and time-varying Doppler frequency shift, the Doppler spectrum of the target acquired by the traditional Fourier method was ambiguous, and the same in the radar images of the target. Therefore, an adaptive Wigner-Ville time-frequency analysis method was presented in the paper, that is, the local fuzzy function could be obtained by applying the two-dimensional adding Window Fourier Transform to signal's Wigner-Ville distribution, which made the kernel function, not only be adaptive to time, but also to the frequency. Finally, the simulation results show that the method has a good time-frequency concentration, and effectively control the cross-term interference.

Hua-ling, Guo; Jia-hao, Deng; Ke-rong, Cai

2011-02-01

331

Flowmeter for pressure-driven chromatography systems  

Science.gov (United States)

A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 .mu.m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of .mu.L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

Paul, Phillip H. (Livermore, CA); Arnold, Don W. (Livermore, CA)

2003-01-01

332

Electromechanical flowmeter accurately monitors fluid flow  

Science.gov (United States)

Electromechanical flowmeter remotely and accurately monitors the flow rate and total volume of a transparent liquid discharged from a dispensing system. A dual dispensing tube system provides a relative reference level which permits compensation for temperature variations.

Grant, D. J.

1965-01-01

333

Automated secondary standard for liquid flowmeters  

Science.gov (United States)

Calibration time is reduced from one hour to fifteen minutes. Accuracies of flowmeter calibrations are approximately 99.75 percent, using this standard. Standard is also used to test or set flow switches.

Hobart, H. F.

1977-01-01

334

Development of the immersed sodium flowmeter  

International Nuclear Information System (INIS)

An immersed sodium flowmeter of the range 3 m3/h is developed. It is a flowmeter of entire-sealed construction, it can be operated in sodium. Its construction, the theoretical calculation of the calibration characteristic and the pressure loss, the test facility and the calibration test are presented in detail. It analytical expression of the calibration characteristic in the temperature limit 200?600 degree C and the error analysis are given. The basic error of this immersed sodium flowmeter is below +-2.3% of the measuring range. The immersed sodium flowmeter can be used to resolve the sodium flowrate measuring problems of the in-reactor component of LMFBR, for example, the flowrate measuring of the in-reactor sodium purification loop, the flowrate measuring of the immersed sodium pump and the flowrate measuring of the in-reactor test component

335

Nuclear magnetic resonance blood flowmeter  

International Nuclear Information System (INIS)

An improved nuclear magnetic resonance blood flowmeter is described for non-invasively measuring blood flow in a human limb comprising; polarizing magnet means for generating a substantially uniform magnetic field; a limb receiving lumen for supporting a human limb within the field generated by the polarizing magnet means so that blood molecules within the limb are magnetically polarized thereby; transmitter means located adjacent the lumen for inducing a nuclear magnetic resonance response in the blood molecules of the human limb disposed within the lumen; scanning means including: first means for generating a first pair of opposing magnetic fields within the lumen for cancelling the nuclear magnetic resonance response induced by the transmitter means everywhere except within a first null plane along which the first opposing magnetic fields cancel each other; second means for generating a second pair of opposing magnetic fields; and control means coupled to the first and second means for generating the first and second pair of opposing magnetic fields

336

Implementation and calibration of a laser Doppler velocimeter in order to measure liquids velocity  

Directory of Open Access Journals (Sweden)

Full Text Available Un sistema ? optico se aplic ? o y calibro con la t ? ecnica de l ? aser Doppler de diagnostico diferencial o configuraci ? on de doble haz, con detecci ? on hacia adelante, con el fin de medir un componente del vector de velocidad en l ? ?quidos transl ? ucidos. Este documento describe dos etapas, la primera es la calibraci ? on del veloc ? ?metro Doppler l ? aser a trav ? es de un objetivo rotatorio, y un acoplador ? optico que permiten verificar que las frecuencias que son detectados por el sistema ? optico, corresponden a las velocidades de rotaci ? on de dicho dispositivo. La segunda etapa es la medici ? on de la velocidad del l ? ?quido en un sistema de flujo estrecha que permite obtener r ? egimen de flujo laminar (bajo n ? umero de Reynolds, y se determin ? o la velocidad de componente ortogonal al patr ? on de interferencia franjas. Esta velocidad se calcula mediante la detecci ? on de la frecuencia de cambio en la intensidad que sufre la periferia (frecuencia Doppler donde las part ? ?culas artificiales o naturales (siembra sumergidos en el fluido a trav ? es de ellos. La radiaci ? on de la luz dispersa por la siembra conten ? ?a la se ? nal Doppler que se recoge con un fotodetector y se muestran en una computadora como un espectro de frecuencia.

C.F. Ord\\u00F3\\u00F1ez Urbano

2013-01-01

337

Using ordinal logistic regression to evaluate the performance of laser-Doppler predictions of burn-healing time  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Laser-Doppler imaging (LDI of cutaneous blood flow is beginning to be used by burn surgeons to predict the healing time of burn wounds; predicted healing time is used to determine wound treatment as either dressings or surgery. In this paper, we do a statistical analysis of the performance of the technique. Methods We used data from a study carried out by five burn centers: LDI was done once between days 2 to 5 post burn, and healing was assessed at both 14 days and 21 days post burn. Random-effects ordinal logistic regression and other models such as the continuation ratio model were used to model healing-time as a function of the LDI data, and of demographic and wound history variables. Statistical methods were also used to study the false-color palette, which enables the laser-Doppler imager to be used by clinicians as a decision-support tool. Results Overall performance is that diagnoses are over 90% correct. Related questions addressed were what was the best blood flow summary statistic and whether, given the blood flow measurements, demographic and observational variables had any additional predictive power (age, sex, race, % total body surface area burned (%TBSA, site and cause of burn, day of LDI scan, burn center. It was found that mean laser-Doppler flux over a wound area was the best statistic, and that, given the same mean flux, women recover slightly more slowly than men. Further, the likely degradation in predictive performance on moving to a patient group with larger %TBSA than those in the data sample was studied, and shown to be small. Conclusion Modeling healing time is a complex statistical problem, with random effects due to multiple burn areas per individual, and censoring caused by patients missing hospital visits and undergoing surgery. This analysis applies state-of-the art statistical methods such as the bootstrap and permutation tests to a medical problem of topical interest. New medical findings are that age and %TBSA are not important predictors of healing time when the LDI results are known, whereas gender does influence recovery time, even when blood flow is controlled for. The conclusion regarding the palette is that an optimum three-color palette can be chosen 'automatically', but the optimum choice of a 5-color palette cannot be made solely by optimizing the percentage of correct diagnoses.

Pape Sarah A

2009-02-01

338

Repeatability of the evaluation of systemic microvascular endothelial function using laser doppler perfusion monitoring: clinical and statistical implications  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english OBJECTIVE: An awareness of the repeatability of biological measures is required to properly design and calculate sample sizes for longitudinal interventional studies. We investigated the day-to-day repeatability of measures of systemic microvascular reactivity using laser Doppler perfusion monitorin [...] g. METHODS: We performed laser Doppler perfusion monitoring in combination with skin iontophoresis using acetylcholine and sodium nitroprusside as well as post-occlusive reactive and thermal hyperemia twice within two weeks. The repeatability was assessed by calculating the within-subject standard deviations, limits of agreement, typical errors and intra-class correlation coefficients between days 1 and 2. The ratio of the within-subject standard deviation to the mean values obtained on days 1 and 2 (within-subject standard deviation/GM) was used to determine the condition with the best repeatability. RESULTS: Twenty-four healthy subjects, aged 24.6 + 3.8 years, were recruited. The area under the curve of the vasodilatory response to post-occlusive reactivity showed marked variability (within-subject standard deviation/GM = 0.83), while the area under the curve for acetylcholine exhibited less variability (within-subject standard deviation/ GM = 0.52) and was comparable to the responses to sodium nitroprusside and thermal treatment (within-subject standard deviations/GM of 0.67 and 0.56, respectively). The area under the blood flow/time curve for vasodilation during acetylcholine administration required the smallest sample sizes, the area under the blood flow/time curve during post-occlusive reactivity required the largest sample sizes, and the area under the blood flow/time curves of vasodilation induced by sodium nitroprusside and thermal treatment required intermediate sizes. CONCLUSIONS: In view of the importance of random error related to the day-to-day repeatability of laser Doppler perfusion monitoring, we propose an original and robust statistical methodology for use in designing prospective clinical studies.

Eduardo, Tibiriçá; Alessandra SM, Matheus; Bruno, Nunes; Sandro, Sperandei; Marilia B., Gomes.

339

Time domain algorithm for accelerated determination of the first order moment of photo current fluctuations in high speed laser Doppler perfusion imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Advances in optical array sensor technology allow for the real time acquisition of dynamic laser speckle patterns generated by tissue perfusion, which, in principle, allows for real time laser Doppler perfusion imaging (LDPI). Exploitation of these developments is enhanced with the introduction of faster algorithms to transform photo currents into perfusion estimates using the first moment of the power spectrum. A time domain (TD) algorithm is presented for determining the first-order spectra...

2009-01-01

340

Electro-kinetics of charged-sphere suspensions explored by integral low-angle super-heterodyne laser Doppler velocimetry  

Science.gov (United States)

We investigated the flow behaviour of colloidal charged-sphere suspensions using a newly designed integral low-angle super-heterodyne laser Doppler velocimetry instrument, which combines the advantages of several previous approaches. Sample conditions ranged from strong electrostatic interactions with pronounced short-range order to individual particles with no spatial correlations. The obtained power spectra correspond to diffusion broadened velocity distributions across the complete sample cross section. The excellent performance of the instrument is highlighted in detail by the example of electro-kinetic flow of suspensions in a closed cell of a rectangular cross section. We demonstrate the excellent performance of our approach with the example of electro-phoretic-electro-osmotic experiments, showing that a comprehensive flow characterization becomes possible by analysing the measured electro-kinetic mobilities, the flow-profile, an effective diffusion coefficient and the integrated scattering density. We briefly discuss present limitations, possible extensions and interesting applications in other fields.

Palberg, Thomas; Köller, Tetyana; Sieber, Bastian; Schweinfurth, Holger; Reiber, Holger; Nägele, Gerhard

2012-11-01

 
 
 
 
341

Photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid  

International Nuclear Information System (INIS)

The authors present an optically based method combining photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid. The frequency spectrum of a silicon cantilever measured in water over frequencies ranging up to 10 MHz shows that the method allows us to excite and detect higher modes, from fundamental to fifth flexural, without enhancing spurious resonances. By reducing the tip oscillation amplitude using higher modes, the average tip-sample force gradient due to chemical bonds is effectively increased to achieve high-spatial-resolution imaging in liquid. The method's performance is demonstrated by atomic resolution imaging of a mica surface in water obtained using the second flexural mode with a small tip amplitude of 99 pm; individual atoms on the surface with small height differences of up to 60 pm are clearly resolved.

342

An LDA (Laser-Doppler Anemometry) investigation of three-dimensional normal shock wave boundary-layer interactions  

Science.gov (United States)

Nonintrusive measurements were made of a normal shock wave/boundary layer interaction. Two dimensional measurements were made throughout the interaction region while 3-D measurements were made in the vicinity of the shock wave. The measurements were made in the corner of the test section of a continuous supersonic wind tunnel in which a normal shock wave had been stabilized. Laser Doppler Anemometry, surface pressure measurement and flow visualization techniques were employed for two freestream Mach number test cases: 1.6 and 1.3. The former contained separated flow regions and a system of shock waves. The latter was found to be far less complicated. The results define the flow field structure in detail for each case.

Chriss, R. M.; Hingst, W. R.; Strazisar, A. J.; Keith, T. G., Jr.

1989-01-01

343

Laser Doppler Velocimetry for Joint Measurements of Acoustic and Mean Flow Velocities : LMS-based Algorithm and CRB Calculation  

CERN Document Server

This paper presents a least mean square (LMS) algorithm for the joint estimation of acoustic and mean flow velocities from laser doppler velocimetry (LDV) measurements. The usual algorithms used for measuring with LDV purely acoustic velocity or mean flow velocity may not be used when the acoustic field is disturbed by a mean flow component. The LMS-based algorithm allows accurate estimations of both acoustic and mean flow velocities. The Cram\\'er-Rao bound (CRB) of the associated problem is determined. The variance of the estimators of both acoustic and mean flow velocities is also given. Simulation results of this algorithm are compared with the CRB and the comparison leads to validate this estimator.

Simon, Laurent; Degroot, Anne; Lionet, Louis; 10.1109/TIM.2008.917670

2009-01-01

344

Transient thermo-mechanical analysis of smart power switches by a laser Doppler vibrometer and numerical simulations  

Science.gov (United States)

In the paper, application of a laser Doppler vibrometry (LDV) technique for the surface thermal expansion measurement of the semiconductor power devices is presented. As the LDV method can provide a signal directly proportional to the velocity of the surface deformation even for step inputs, the study of a thermal deformation transient process has been accomplished. The time dependence of surface out-of-plane displacement was obtained by integration of the measured velocity time dependences for several discrete surface points. The LDV results of transient performance were confronted with those simulated by the finite-element method. Such a numerical/experimental analysis has been carried out on a composite multilayer structure of a smart power switch device operating under short circuit conditions. A good quantitative coincidence was achieved between thermo-mechanical modelling and LDV measurements.

Košel, V.; Držík, M.; Šatka, A.; Chlpík, J.; Glavanovics, A.; Donoval, D.

2011-01-01

345

A fast time-domain algorithm for the assessment of tissue blood flow in laser-Doppler flowmetry  

Energy Technology Data Exchange (ETDEWEB)

In this study, we derive a fast, novel time-domain algorithm to compute the nth-order moment of the power spectral density of the photoelectric current as measured in laser-Doppler flowmetry (LDF). It is well established that in the LDF literature these moments are closely related to fundamental physiological parameters, i.e. concentration of moving erythrocytes and blood flow. In particular, we take advantage of the link between moments in the Fourier domain and fractional derivatives in the temporal domain. Using Parseval's theorem, we establish an exact analytical equivalence between the time-domain expression and the conventional frequency-domain counterpart. Moreover, we demonstrate the appropriateness of estimating the zeroth-, first- and second-order moments using Monte Carlo simulations. Finally, we briefly discuss the feasibility of implementing the proposed algorithm in hardware. (note)

Binzoni, Tiziano [Departement des Neurosciences Fondamentales, University of Geneva (Switzerland); Seelamantula, Chandra Sekhar [Department of Electrical Engineering, Indian Institute of Science, Bangalore (India); Van De Ville, Dimitri, E-mail: tiziano.binzoni@unige.c [Departement de l' Imagerie et des Sciences de l' Information Medicale, University Hospital, Geneva (Switzerland)

2010-07-07

346

Applying Laser Doppler Anemometry inside a Taylor-Couette geometry - Using a ray-tracer to correct for curvature effects  

CERN Document Server

In the present work it will be shown how the curvature of the outer cylinder affects Laser Doppler anemometry measurements inside a Taylor-Couette apparatus. The measurement position and the measured velocity are altered by curved surfaces. Conventional methods for curvature correction are not applicable to our setup, and it will be shown how a ray-tracer can be used to solve this complication. By using a ray-tracer the focal position can be calculated, and the velocity can be corrected. The results of the ray-tracer are verified by measuring an a priori known velocity field, and after applying refractive corrections good agreement with theoretical predictions are found. The methods described in this paper are applied to measure the azimuthal velocity profiles in high Reynolds number Taylor-Couette flow for the case of outer cylinder rotation.

Huisman, Sander G; Sun, Chao

2012-01-01

347

Transient thermo-mechanical analysis of smart power switches by a laser Doppler vibrometer and numerical simulations  

International Nuclear Information System (INIS)

In the paper, application of a laser Doppler vibrometry (LDV) technique for the surface thermal expansion measurement of the semiconductor power devices is presented. As the LDV method can provide a signal directly proportional to the velocity of the surface deformation even for step inputs, the study of a thermal deformation transient process has been accomplished. The time dependence of surface out-of-plane displacement was obtained by integration of the measured velocity time dependences for several discrete surface points. The LDV results of transient performance were confronted with those simulated by the finite-element method. Such a numerical/experimental analysis has been carried out on a composite multilayer structure of a smart power switch device operating under short circuit conditions. A good quantitative coincidence was achieved between thermo-mechanical modelling and LDV measurements

348

Time-resolved and doppler-reduced laser spectroscopy on atoms  

International Nuclear Information System (INIS)

Radiative lifetimes have been studied in neutral boron, carbon, silicon and strontium, in singly ionized gadolinium and tantalum and in molecular carbon monoxide and C2. The time-resolved techniques were based either on pulsed lasers or pulse-modulated CW lasers. Several techniques have been utilized for the production of free atoms and ions such as evaporation into an atomic beam, sputtering in hollow cathodes and laser-produced plasmas. Hyperfine interactions in boron, copper and strontium have been examined using quantum beat spectroscopy, saturation spectroscopy and collimated atomic beam spectroscopy. Measurement techniques based on effusive hollow cathodes as well as laser produced plasmas in atomic physics have been developed. Investigations on laser produced plasmas using two colour beam deflection tomography for determination of electron densities have been performed. Finally, new possibilities for view-time-expansion in light-in-flight holography using mode-locked CW lasers have been demonstrated. (au)

349

Measurements of velocity spectra using time-resolving Doppler global velocimetry with laser frequency modulation and a detector array  

Science.gov (United States)

Measuring velocity spectra in turbulent flows requires methods providing a high temporal resolution and a low measurement uncertainty. Hot-wire anemometry is often used, but it is intrusive. Laser Doppler anemometry is non-intrusive, but due to the statistical arrival of individual tracers provides no constant measurement rate. We therefore propose the use of Doppler global velocimetry (DGV), which is a contactless method allowing temporally equidistant measurements of continuous signals. Additionally, 2d measurements are possible instead of single point measurements. The commonly applied slow cameras are substituted by a fibre coupled detector array consisting of 25 avalanche photo diodes, which increases temporal resolution up to 10 ?s. Contrarily to conventional DGV, a sinusoidal laser frequency modulation enables omitting the reference detector array. A correction of beam splitting and image misalignment errors is thus not necessary, but disturbances due to temporal fluctuations of the scattered light can occur and have to be reduced by increasing the modulation frequency. We validate the proposed system capability of synchronously measuring velocity spectra at multiple points in turbulent flows by presenting experimental results. The acquired velocity spectra in a wind tunnel experiment show good agreement with hot-wire comparison measurements within 0.1 m/s. An uncertainty analysis is given, which allows the achievable measurement uncertainty to be estimated as a function of the desired temporal resolution. An uncertainty down to 0.2 m/s can, for example, be achieved assuming a desired temporal resolution of 1 ms. These promising results open new perspectives for turbulence and correlation studies in flows such as to investigate the turbulence characteristics behind a truncated cylinder attached to a plate or the inlet of an aircraft turbine for flow characterisation in industry.

Fischer, Andreas; Büttner, Lars; Czarske, Jürgen; Eggert, Michael; Müller, Harald

2009-10-01

350

Wavelength modulation diode laser absorption signals from Doppler broadened absorption profiles  

International Nuclear Information System (INIS)

It has previously been shown that the nth harmonic output from a wavelength modulation absorption spectrometry (WMS) instrumentation can be expressed in terms of various Fourier coefficients (primarily the nth) of the wavelength modulated lineshape function for the transition of the species under investigation. Explicit expressions for an arbitrary Fourier coefficient of a wavelength modulated Lorentzian lineshape function have previously been derived and used for predicting WMS signals from homogeneously (collisionally) broadened transitions. This work derives explicit expressions for an arbitrary Fourier coefficient of a wavelength modulated Gaussian shaped absorption profile, which thus makes possible the description of WMS signals also from inhomogeneously (Doppler) broadened absorption profiles

351

Measurements of ultrasonic waves by means of laser Doppler velocimeter and an experimental study of elastic wave propagation in inhomogeneous media; Laser doppler sokudokei ni yoru choonpa keisoku to ganseki wo mochiita fukinshitsu baishitsu no hado denpa model jikken  

Energy Technology Data Exchange (ETDEWEB)

In the study of seismic wave propagation, a model experimenting technique has been developed using a laser Doppler velocimeter (LDV) as the sensor. This technique, not dependent on conventional piezoelectric devices, only irradiates the specimen with laser to measure the velocity amplitude on the target surface, eliminating the need for close contact between the specimen and sensor. In the experiment, elastic penetration waves with their noise levels approximately 0.05mm/s were observed upon application of vibration of 10{sup 6}-10{sup 5}Hz. The specimen was stainless steel or rock, and waveforms caught by the LDV and piezoelectric device were compared. As the result, it was found that the LDV is a powerful tool for effectively explaining elastic wave propagation in inhomogeneous media. The piezoelectric device fails to reproduce accurately the waves to follow the initial one while the LDV detect the velocity amplitude on the specimen surface in a wide frequency range encouraging the discussion over the quantification of observed waveforms. 10 refs., 7 figs.

Nishizawa, O.; Sato, T. [Geological Survey of Japan, Tsukuba (Japan); Lei, X. [Dia Consultants Company, Tokyo (Japan)

1996-05-01

352

Laser Doppler velocimetry measurement at a hard-to-reach intake port of a two-stroke engine  

Science.gov (United States)

To understand better the complex scavenging process in ported two-stroke engines, optical set-ups were designed for velocity measurements at the exit of an intake port of a motoring and firing single-cylinder propane-fueled two-stroke engine by laser Doppler velocimetry. The radial velocity component was measured at the center of one port at engine speeds of 600, 900, and 1200 rpm. Laser beams entered the engine from the top through a quartz window and the light scattered by the seed particles was collected at 90° through the exhaust ports and a side window. The noise produced by the piston head was analyzed and separated from the signal generated by the seed particles. Analysis of the results from this engine showed that, in general, differences in both magnitude and the shape of the plotted results were observed when the engine was firing. A backflow into the intake system was observed at 600 rpm; this backflow decreased in strength, shifted in crank angle at 900 rpm, and eventually was eliminated at an engine speed of 1200 rpm.

Chehroudi, B.; Schuh, D.

353

Microvascular origin of laser-Doppler flux signal from the surface of normal and injured liver of the rat.  

Science.gov (United States)

Although laser-Doppler flowmetry (LDF) is a widely used technique, little is known about its microvascular origin from the surface of the liver. In the present study, we attempted to identify the microvascular bed interrogated by the laser light, by correlating perfusion and red blood cell velocity data obtained using intravital fluorescence microscopy (IVFM) with the LDF signal recorded under normal conditions and following liver injury. Sprague-Dawley rats which underwent hepatic artery ligation (HAL) or nonarterialized liver transplantation (NOLT) served as in vivo models of reduced sinusoidal red blood cell velocity (RBC(vel)) and altered homogeneity of perfusion, respectively. Three groups of animals were studied: HAL (n = 8), NOLT (n = 8), and sham-operated control (n = 8). Homogeneous perfusion of the sinusoids and liver lobules and reduced sinusoidal RBC(vel) were initially confirmed in the HAL group. In addition, significantly reduced sinusoidal and lobular perfusion was observed in the NOLT liver. HAL caused a 28% reduction in the LDF signal (P vel) and LDF signal (y = 0.78x + 50.98, r2 = 0.71, P blood flow in the sinusoids, compared to other microvessels, has a significant influence on the LDF signal from the surface of the liver. PMID:11678638

Tawadrous, M N; Zhang, X Y; Wheatley, A M

2001-11-01

354

Development and Application of an Ultrasonic Gas Flowmeter  

International Nuclear Information System (INIS)

This paper describes the development and the field application of the ultrasonic gas flowmeter for accurate measurement of the volumetric flow rate of gases in a harsh environmental conditions in iron and steel making company. This ultrasonic flowmeter is especially suited for measuring LDG, COG, BFG gases produced in iron and steel making process. This is a transit time type ultrasonic flowmeter. We have developed the transmitting and receiving algorithm of ultrasonic wave and the ultrasonic signal processing algorithm to develope a transit time type ultrasonic flowmeter. We have evaluated the performance of ultrasonic flowmeter by the calibration system with Venturi type standard flowmeter. We has confirmed its reliability by extensive field tests for a year in POSCO, iron and steel making company. Now we have developed the commercial model of ultrasonic flowmeter and applied to the POSCO gas line

355

Particle Size And Velocity Measurement On Flows Of Transparent Or Non Transparent Spherical Particles By Laser-Doppler-Anemometry; Problems Of Practical Application  

Science.gov (United States)

In many applications of fluid atomization there is a high demand for point or overall measured data of size and flux of the liquid or solidified drops. For a few years the phase-Doppler-method (LDVS) besides of the Visibility/Intensity-method has proofed out as a very useful instrument for the analysis of such spray situations. In spite of the well known velocity measurement of particles by laser-Doppler-anemometry the particle sizing by this method is more complex and asks for both a more sophisticated electronic signal processing and above all a knowledge of the optical character of the particles under observation. The paper shows the influence of the light scattering character of different spherical particles on the necessary evaluation of Phase-Doppler data. After a brief description of the Phase-Doppler-method including the basic physical principles it will be shown the Phase difference dependency of doppler bursts on different photodetector positions on one hand and on the refraction index and particle size on the other. For both transparent and non transparent particles there will be compared the results of the complex Mie light scattering calculations with simplified geometrical based calculations and experiments to find out detection angles which give unambiguous particle size informations and in addition allow an experimental arrangement as simple as possible. The results show that in many cases where particles are not totally transparent a back-scatter-arrangement of the photodetectors should be possible. Although the requirement of particle's sphericity may restrict the applicability of the phase-Doppler-laser-anemometry we should confirm that very often in multiphase flow systems the dispersed particles are drops or bubbles or if solid have a spherical shape. In the latter case we only need a sufficient smoothness of particle surface. The experimental results presented here are obtained from very different fluids ranging from water to molten metal.

Bauckhage, K.; Fritsching, U.; Heuermann, J.; Schulte, G.

1989-01-01

356

High accuracy fuel flowmeter. Phase 2C and 3: The mass flowrate calibration of high accuracy fuel flowmeters  

Science.gov (United States)

A facility for the precise calibration of mass fuel flowmeters and turbine flowmeters located at AMETEK Aerospace Products Inc., Wilmington, Massachusetts is described. This facility is referred to as the Test and Calibration System (TACS). It is believed to be the most accurate test facility available for the calibration of jet engine fuel density measurement. The product of the volumetric flow rate measurement and the density measurement, results in a true mass flow rate determination. A dual-turbine flowmeter was designed during this program. The dual-turbine flowmeter was calibrated on the TACS to show the characteristics of this type of flowmeter. An angular momentum flowmeter was also calibrated on the TACS to demonstrate the accuracy of a true mass flowmeter having a 'state-of-the-art' design accuracy.

Craft, D. William

1992-01-01

357

Decomposition of a laser-Doppler spectrum for estimation of speed distribution of particles moving in an optically turbid medium: Monte Carlo validation study  

International Nuclear Information System (INIS)

A method for measurement of distribution of speed of particles moving in an optically turbid medium is presented. The technique is based on decomposition of the laser-Doppler spectrum. The theoretical background is shown together with the results of Monte Carlo simulations, which were performed to validate the proposed method. The laser-Doppler spectra were obtained by Monte Carlo simulations for assumed uniform and Gaussian speed distributions of particles moving in the turbid medium. The Doppler shift probability distributions were calculated by Monte Carlo simulations for several anisotropy factors of the medium, assuming the Hanyey-Greenstein phase function. The results of the spectra decomposition show that the calculated speed distribution of moving particles match well the distribution assumed for Monte Carlo simulations. This result was obtained for the spectra simulated in optical conditions, in which the photon is scattered with the Doppler shift not more than once during its travel between the source and detector. Influence of multiple scattering of the photon is analysed and a perspective of spectrum decomposition under such conditions is considered. Potential applications and limitations of the method are discussed

358

BOREHOLE FLOWMETERS: FIELD APPLICATION AND DATA ANALYSIS  

Science.gov (United States)

This paper reviews application of borehole flowmeters in granular and fractured rocks. asic data obtained in the field are the ambient flow log and the pumping-induced flow log. hese basic logs may then be used to calculate other quantities of interest. he paper describes the app...

359

Reducing Fatigue in a Rotary Flowmeter  

Science.gov (United States)

Redesign of vanes straightening flow of liquid in rotary flowmeter increase fatigue lives of vanes and rotor. Purpose of vanes to eliminate turbulence so proportionality between flow and rotor speed constant. Nonuniform but symmetrical, new spacing of straightener vanes prevents flow wake from strongly interacting with rotor blades. At same time, vanes ensure accurate flow-rate measurement.

Rao, G.

1987-01-01

360

Development of permanent-magnet sodium flowmeter  

International Nuclear Information System (INIS)

Two permanent-magnet sodium flowmeters of rangs 5 m3/h and 0.5 m3/h are developed. Their constructions, the theoretical calculations of calibration characteristic and pressure loss, the calibration test and the error analysis are presented. The analytical expressions of the calibration characteristic are given

 
 
 
 
361

Analysis and Calibration of Tubular Flowmeters.  

Science.gov (United States)

Capillary flowmeters are capable of accurate measurement of gas flow rates when the flow rate is sufficiently low. However, for large flow rates entrance effects exist throughout a tube of reasonable length and must be accounted for in the meter calibrati...

D. A. Willoughby, P. A. Kittle

1966-01-01

362

Measurements of velocity profiles in a supersonic wind tunnel using the Laser-Doppler Method  

International Nuclear Information System (INIS)

A laser-velocimeter has been installed on a 100 x 100-mm-supersonic wind tunnel for measurements of mean velocity distributions and intensities of turbulence in the boundary layer of the tunnel at supersonic Mach numbers M = 1.75 and 2.5. The measured values, being reduced by means of a double counter method, have been compared with those formerly found using a combined pressure and temperature probe. The good correspondence of both results confirms that the laser-velocimetry is available as a non-interfering method for surveying supersonic flows. (orig.)

363

Gingival blood flow under total combs by functional pressure evaluated with laser-Doppler flowmetry, a non-invasive method of blood flow measurement  

International Nuclear Information System (INIS)

Gingival blood flow under total-combs by functional pressure evaluated with Laser-Doppler Flowmetry, a non-invasive method of blood flow measurement. Microcirculation of gum's capillary system can be measured non-invasive by Laser-Doppler-Flowmetry (LDF). Circulation, defined by the number of floating erythrocytes per unit of time, is measured by a fibro-optical Laser-Doppler-Flowmetry. The task was to examine, if there is any change of gum's circulation during strain and relief. Circulation on defined measurepoints, divided on the four quadrants, was determined among maximal strain and subsequent relief, on one probationer (complete denture bearer). Before every measure session systemic pressure was taken. LDF-value was taken on top of jaw-comb, in doing so, to get reproducible result and a satisfying fixation of the probe, there was made an artificial limb of the upper and lower comb. In the upper comb a dynamometer-box, which determined minimal and maximal comb pressure, was integrated. The received results of the LDF-measurement, expressed as perfusion units (PU) were lower under applied pressure than by pressure points more distant. Hyperemia, resulting during relief, seemed the more intense, the less perfusion was before. This new, non-invasive kind of circulation measurement seems to be quite predestined to be used for gingival diagnostic under artificial limb in the future. (author)

364

Use of small turbine-type flowmeters to measure flow in large pipes  

Science.gov (United States)

Measurement of mass flow in large pipes using small turbine-type flowmeters is discussed. Experiments for determining accuracy of flowmeter and applicability to various types of flow measurement are reported. Illustration of turbine flowmeter and calibration curve are included.

Minkin, H. L.; Hobart, H. F.

1972-01-01

365

A near infrared laser frequency comb for high precision Doppler planet surveys  

Directory of Open Access Journals (Sweden)

Full Text Available Perhaps the most exciting area of astronomical research today is the study of exoplanets and exoplanetary systems, engaging the imagination not just of the astronomical community, but of the general population. Astronomical instrumentation has matured to the level where it is possible to detect terrestrial planets orbiting distant stars via radial velocity (RV measurements, with the most stable visible light spectrographs reporting RV results the order of 1?m/s. This, however, is an order of magnitude away from the precision needed to detect an Earth analog orbiting a star such as our sun, the Holy Grail of these efforts. By performing these observations in near infrared (NIR there is the potential to simplify the search for distant terrestrial planets by studying cooler, less massive, much more numerous class M stars, with a tighter habitable zone and correspondingly larger RV signal. This NIR advantage is undone by the lack of a suitable high precision, high stability wavelength standard, limiting NIR RV measurements to tens or hundreds of m/s [1, 2]. With the improved spectroscopic precision provided by a laser frequency comb based wavelength reference producing a set of bright, densely and uniformly spaced lines, it will be possible to achieve up to two orders of magnitude improvement in RV precision, limited only by the precision and sensitivity of existing spectrographs, enabling the observation of Earth analogs through RV measurements. We discuss the laser frequency comb as an astronomical wavelength reference, and describe progress towards a near infrared laser frequency comb at the National Institute of Standards and Technology and at the University of Colorado where we are operating a laser frequency comb suitable for use with a high resolution H band astronomical spectrograph.

Bally J.

2011-07-01

366

Fiber optic laser Doppler velocimeter with non-mechanical scanning of spatially encoded points for cross-sectional velocity distribution measurement  

Science.gov (United States)

A fiber-optic laser Doppler velocimeter (LDV) combining non-mechanical scanning and multipoint measurement is proposed for two-dimensional velocity distribution measurement on a cross-sectional plane. The LDV consists of a main body including a tunable laser and LiNbO3 phase-shifter array, and a probe including diffraction gratings. The phaseshifter array is used to generate spatially encoded measurement points aligned in the transverse direction by multichannel optical serrodyne modulation, and these points are axially scanned with wavelength change. Two-dimensional velocitydistribution measurement is demonstrated using a probe setup with an 8-channel beam array.

Maru, Koichi; Watanabe, Kento

2014-07-01

367

Experimental determination of mode correction factors for thermal method spring constant calibration of AFM cantilevers using laser Doppler vibrometry  

International Nuclear Information System (INIS)

Mode correction factors (MCFs) represent a significant adjustment to the spring constant values measured using the thermal cantilever calibration method. Usually, the ideal factor of 0.971 for a tipless rectangular cantilever is used, which adjusts the value by 3% for the first flexural mode. An experimental method for determining MCFs has been developed that relies on measuring the areas under the first few resonance peaks for the flexural mode type. Using this method, it has been shown that MCFs for the first flexural mode of commercially available atomic force microscope cantilevers actually vary from 0.95 to 1.0, depending on the shape and end mass of the cantilever. Triangular shaped cantilevers tend to lower MCFs with tipless versions providing the lowest values. Added masses (including tips) tend to increase the first flexural mode’s MCF to higher values with large colloid probes at the high extreme. Using this understanding and applying it to the recently developed laser Doppler vibrometry thermal calibration method it is now possible to achieve very accurate and precise cantilever spring constant calibrations (uncertainties close to ±1%) with commonly available commercial cantilevers such as tipped rectangular and triangular cantilevers, and colloid probes. (paper)

368

Mode shape reconstruction of an impulse excited structure using continuous scanning laser Doppler vibrometer and empirical mode decomposition  

Science.gov (United States)

For vibration testing, discrete types of scanning laser Doppler vibrometer (SLDV) have been developed and have proven to be very useful. For complex structures, however, SLDV takes considerable time to scan the surface of structures and require large amounts of data storage. To overcome these problems, a continuous scan was introduced as an alternative. In this continuous method, the Chebyshev demodulation (or polynomial) technique and the Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. As an alternative, in this paper, the Hilbert-Huang transform approach is applied to impact excitation cases in terms of a numerical approach, where the vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a clamped-clamped beam was chosen as the test rig in the numerical simulation and real experiment. This paper shows that with additional innovative steps of using ideal bandpass filters and nodal point determination in the postprocessing, the Hilbert-Huang transformation can be used to create a better mode shape reconstruction even in the impact excitation case.

Kyong, Yongsoo; Kim, Daesung; Dayou, Jedol; Park, Kyihwan; Wang, Semyung

2008-07-01

369

Smoothing and statistical evaluation of laser Doppler velocimetry data of turbulent flows in rotating and reciprocating machinery  

Science.gov (United States)

Arbitrarily time-distributed velocity information acquired by laser Doppler velocimeter systems needs special care when evaluated wrt. the mean velocity and the components of the Reynolds stress tensor. In rotating machinery, the arrival time information can be uniquely mapped to the angular position ? of the runner blades by using encoder signals relating a fixed runner position to an arrival time. It is convenient to statistically evaluate the velocity information of the detected particles in an angular window [?0-??/2,?0+??/2] in order to obtain mean velocities and turbulence values for an angular position ?0. This approach has the inconvenience that turbulence values calculated from standard deviations are influenced by a possible variation in the mean velocity in the evaluation window. Other problems that arise with this ``evaluation window'' method are the influence of unevenly angular-distributed velocity information on the mean velocity or the poor resolution of maxima and minima of the mean velocity, which is similar to the problem pointed out by Jakoby etal. but being of second-order nature. In this paper, different improvements in the ``evaluation window'' method wrt these problems based on ideas found in a paper by McDonald and Owen are presented. A confidence interval calculation, generalizing the methods of Boutier, for all calculated values is included, which allows an appropriate window size ?? to be chosen for each particular situation. The different methods are compared using examples from wake flows of axial hydraulic turbomachinery measured in air and water.

Glas, W.; Forstner, M.; Kuhn, K.; Jaberg, H.

370

Repeatability, Reproducibility and Standardisation of a Laser Doppler Imaging Technique for the Evaluation of Normal Mouse Hindlimb Perfusion  

Directory of Open Access Journals (Sweden)

Full Text Available Background. Preclinical perfusion studies are useful for the improvement of diagnosis and therapy in dermatologic, cardiovascular and rheumatic human diseases. The Laser Doppler Perfusion Imaging (LDPI technique has been used to evaluate superficial alterations of the skin microcirculation in surgically induced murine hindlimb ischemia. We assessed the reproducibility and the accuracy of LDPI acquisitions and identified several critical factors that could affect LDPI measurements in mice. Methods. Twenty mice were analysed. Statistical standardisation and a repeatability and reproducibility analysis were performed on mouse perfusion signals with respect to differences in body temperature, the presence or absence of hair, the type of anaesthesia used for LDPI measurements and the position of the mouse body. Results. We found excellent correlations among measurements made by the same operator (i.e., repeatability under the same experimental conditions and by two different operators (i.e., reproducibility. A Bland-Altman analysis showed the absence of bias in repeatability (p = 0.29 or reproducibility (p = 0.89. The limits of agreement for repeatability were –0.357 and –0.033, and for reproducibility, they were –0.270 and 0.238. Significant differences in perfusion values were observed in different experimental groups. Conclusions. Different experimental conditions must be considered as a starting point for the evaluation of new drugs and strategic therapies.

Arturo Brunetti

2012-12-01

371

Non-invasive laser Doppler perfusion measurements of large tissue volumes and human skeletal muscle blood RMS velocity  

International Nuclear Information System (INIS)

This study proposes the implementation of an algorithm allowing one to derive absolute blood root-mean-square (RMS) velocity values from laser Doppler perfusion meter (LDP) data. The algorithm is based on the quasi-elastic light scattering theory and holds for multiple scattering. While standard LDP measurements are normally applicable to a small region of interest (?1 mm2), the present method allows the analysis of both small and large tissue volumes with small and large interoptode spacings (e.g., 1.5 cm). The applicability and the limits of the method are demonstrated with measurements on human skeletal muscle using a custom-built near-infrared LDP meter. Human brachioradialis muscle RMS velocity values of 9.99 ± 0.01 and 5.58 ± 0.03 mm s-1 at 1.5 cm and of 5.18 ± 0.01 and 2.54 ± 0.09 mm s-1 at 2 cm were found when the arm was (a) at rest and (b) occluded, respectively. At very large optode spacings or very high moving particle densities, the theory developed here would need to be amended to take into account second-order effects

372

Non-invasive laser Doppler perfusion measurements of large tissue volumes and human skeletal muscle blood RMS velocity  

Science.gov (United States)

This study proposes the implementation of an algorithm allowing one to derive absolute blood root-mean-square (RMS) velocity values from laser Doppler perfusion meter (LDP) data. The algorithm is based on the quasi-elastic light scattering theory and holds for multiple scattering. While standard LDP measurements are normally applicable to a small region of interest (~1 mm2), the present method allows the analysis of both small and large tissue volumes with small and large interoptode spacings (e.g., 1.5 cm). The applicability and the limits of the method are demonstrated with measurements on human skeletal muscle using a custom-built near-infrared LDP meter. Human brachioradialis muscle RMS velocity values of 9.99 +/- 0.01 and 5.58 +/- 0.03 mm s-1 at 1.5 cm and of 5.18 +/- 0.01 and 2.54 +/- 0.09 mm s-1 at 2 cm were found when the arm was (a) at rest and (b) occluded, respectively. At very large optode spacings or very high moving particle densities, the theory developed here would need to be amended to take into account second-order effects.

Binzoni, T.; Leung, T. S.; Boggett, D.; Delpy, D.

2003-08-01

373

Multifractal analysis of central (electrocardiography) and peripheral (laser Doppler flowmetry) cardiovascular time series from healthy human subjects  

International Nuclear Information System (INIS)

Analysis of the cardiovascular system (CVS) activity is important for several purposes, including better understanding of heart physiology, diagnosis and forecast of cardiac events. The central CVS, through the study of heart rate variability (HRV), has been shown to exhibit multifractal properties, possibly evolving with physiologic or pathologic states of the organism. An additional viewpoint on the CVS is provided at the peripheral level by laser Doppler flowmetry (LDF), which enables local blood perfusion monitoring. We report here for the first time a multifractal analysis of LDF signals through the computation of their multifractal spectra. The method for estimation of the multifractal spectra, based on the box method, is first described and tested on a priori known synthetic multifractal signals, before application to LDF data. Moreover, simultaneous recordings of both central HRV and peripheral LDF signals, and corresponding multifractal analyses, are performed to confront their properties. With the scales chosen on the partition functions to compute Renyi exponents, LDF signals appear to have broader multifractal spectra compared to HRV. Various conditions for LDF acquisitions are tested showing larger multifractal spectra for signals recorded on fingers than on forearms. The results uncover complex interactions at central and peripheral CVS levels

374

Studies of blood flow in human nasal mucosa with /sup133/Xe washout technique and laser doppler flowmetry  

International Nuclear Information System (INIS)

The techniques were applied for studies of the influence of environmental temperature on the human nasal mucosa, for studies of mediators in nasal allergy and for studies of the sympathetic neurogenic control of blood flow in the nasal mucosa. The results show that the two techniques are complementary to one another. The /sup133/Xe washout technique is useful for semiquantitative estimations of blood flow in the deeper parts of the mucosa, while the laser doppler technique is especially suited for continuous recordings of relative blood flow changes in the superficial part of the mucosa. Vascular changes may take part in body temperature regulation changes may take part in body temperature regulation as well as in conditioning of respiratory air. The results support the theories that changes in nasal mucosal blood flow are related to body temperature control, while conditioning of inspiratory air may be more dependent on mucosal blood content. The observed dissociation between changes in the resistance and the capacitance vessels also illustrates that these vascular segments are regulated in different ways. The present results indicate that leukotriene D/sub4/ might contribute to an increased blood flow in the nasal mucosa and to blockage of the nasal airway in the acute allergic reaction. Vasomotion is demonstrated to be present in the nasal mucosa, and it appears to be partly dependent on sympathetic neurogenic activity. The development of the present techniques, means that vascular changes involved in normal nasal function and in nasal disease may be evaluated by a new approach. (author)

375

A primary standard for the volume flow rate of natural gas under high pressure based on laser Doppler velocimetry  

Science.gov (United States)

In December 2003, the Physikalisch-Technische Bundesanstalt (PTB) started the development of an optical-based primary flow rate standard for application in natural gas under high pressures (up to 5.5 MPa). The concept underlying this technology will be presented in this paper. The technical approach is based on the application of a conventional laser Doppler velocimeter (LDV) as well as on a new LDV-based boundary layer sensor. Both technologies are used to determine the characteristic values of the core flow and the boundary layer in a nozzle flow in a separated approach. Because of the high relevance to the demonstration of traceability and to the evaluation of the uncertainty, the related data processing (especially for the boundary layer) is explained in detail. Finally, after summarizing the uncertainty budget for the optical-based primary standard, we will demonstrate the approval of the new primary standard by means of a comparison with the established conventional traceability of PTB for high-pressure natural gas.

Mickan, B.; Strunck, V.

2014-10-01

376

Nondestructive techniques for detection of delamination in ceramic tile: a laboratory comparison between IR thermal cameras and laser Doppler vibrometers  

Science.gov (United States)

In ceramic tile industry, delamination is one of the more important and difficult problems to detect. Among all the general non-destructive evaluation methods, optical inspection technique seem to be particularly suitable. A method based on acquisition and processing of IR thermal images is proposed. Measurements have been performed by artificial heating by an IR quartz lamp. The performance of the technique has been evaluated experimentally and results show that the examine defects in the measured samples have been correctly detected. Another proposed technique for detection of delaminations and voids in structures is vibration monitoring by a scanning laser doppler vibrometer (SLDV). The basic idea is that a defected area will show as a higher velocity one. Structure excitation may be performed by acoustic means, thus allowing for a remote contactless measurement system. Our tests put in evidence that IR thermal images provide a very fast defect detection method appropriate for on line applications, while SLDV results show a better geometrical definition of defects shapes.

De Andrade, Roberto M.; Esposito, Enrico; Paone, Nicola; Revel, Gian M.

1999-02-01

377

Multifractal analysis of heart rate variability and laser Doppler flowmetry fluctuations:comparison of results from different numerical methods  

Energy Technology Data Exchange (ETDEWEB)

To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology.

Humeau, Anne; Buard, Benjamin; Chapeau-Blondeau, Francois; Rousseau, David [Laboratoire d' Ingenierie des Systemes Automatises (LISA), Universite d' Angers, 62 avenue Notre Dame du Lac, 49000 Angers (France); Mahe, Guillaume; Abraham, Pierre, E-mail: anne.humeau@univ-angers.f [Laboratoire de Physiologie et d' Explorations Vasculaires, UMR CNRS 6214-INSERM 771, Centre Hospitalier Universitaire d' Angers, 49033 Angers cedex 01 (France)

2010-10-21

378

Calibration of feedwater flowmeter by high Reynolds number calibration facility  

International Nuclear Information System (INIS)

A high Reynolds number calibration facility for feedwater flowmeter in nuclear power plant is described in the paper. This calibration facility is achieved a 1.8x107 Reynolds number which is equivalent one with the actual plant. A calibration result of ultrasonic flowmeters, which are used to measure feedwater flowrate in a nuclear power plant, is also described under a variety of upstream conditions. Through these calibrations, the calibration method of feedwater flowmeter is suggested. (author)

379

Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor  

Directory of Open Access Journals (Sweden)

Full Text Available A new laser air-motion sensor measures the true airspeed with an uncertainty of less than 0.1 m s?1 (standard error and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard-error uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the Global Positioning System, then indicate (via integrations of the hydrostatic equation during climbs and descents that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 °C. For airspeed, pressure and temperature these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that the new laser air-motion sensor, combined with parametrized fits to correction factors for the measured dynamic and ambient pressure, provides a measurement of temperature that is independent of any other temperature sensor.

W. A. Cooper

2014-03-01

380

Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor  

Directory of Open Access Journals (Sweden)

Full Text Available A new laser air-motion sensor measures the true airspeed with a standard uncertainty of less than 0.1 m s?1 and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the global positioning system, then indicate (via integrations of the hydrostatic equation during climbs and descents that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 °C. For airspeed, pressure and temperature, these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that although the initial calibration of the measured static and dynamic pressures requires a measured temperature, once calibrated these measured pressures and the measurement of airspeed from the new laser air-motion sensor provide a measurement of temperature that does not depend on any other temperature sensor.

W. A. Cooper

2014-09-01

 
 
 
 
381

Sub-Doppler absorption narrowing in atomic vapor at two intense laser fields  

Science.gov (United States)

We have experimentally studied electromagnetically induced transparency (EIT) and absorption (EIA) in hot 85Rb atomic vapor using probe and coupling light with comparable power levels. We have shown that strong-probe EIT has different linewidth and appears in fewer configurations than does usual, weak probe EIT. In V-scheme, where optical pumping and saturation are dominant mechanisms, narrow EIT is possible only when a probe is tuned to a closed transition. The width of the EIT resonance increases with laser intensity with non-linear dependence, similar to the weak-probe EIT in ?- scheme. The EIT in ?- scheme was observed when two transitions had balanced population losses. The EIA was modified for the case of a strong probe as well: in four-level N-scheme with Zeeman sublevels the EIA was observed only for a cycling transition when F’=F+1, where F and F’ are the angular momenta of the 5 2S1/2 (ground) and 5 2P3/2 (excited) state hyper-fine levels, respectively. The combination of strong probe and strong coupling laser beam intensities allows observation of an absorption dip due to three-photon resonance in a four-level scheme that involves the Raman transitions via virtual level.

Krmpot, Aleksandar J.; Mijailovi?, Marina M.; Pani?, Bratimir M.; Luki?, Dragan V.; Kova?evi?, Aleksander G.; Panteli?, Dejan V.; Jelenkovi?, Branislav M.

2005-03-01

382

In situ testing of CO2 laser on dental pulp function: Effects on microcirculation  

Energy Technology Data Exchange (ETDEWEB)

The effect of CO2 laser irradiation on pulpal microcirculation was studied in cat canines. The enamel surfaces of 4 teeth were exposed with energy densities of 304-1440J/cm2, using either a handpiece or a microslad, with a focal spot of 0.21mm and 0.33mm respectively. Pulpal blood flow (PBF) before and following lasing was recorded through the intact tooth surface by a laser Doppler flowmeter. CO2 laser irradiation caused an increase in PBF, which was immediate and transient. The PBF increase was higher in a large pulp than in a small pulp, and it was inversely related to the focal spot size. These findings confirm that the dental pulp is thermally affected by CO2 lasing of the tooth surface, however, without extensive pulp coagulation. It is concluded that the effects of laser irradiation on the pulpal microcirculation may be studied in situ by means of the presented methodology.

Friedman, S.; Liu, M.; Doerscher-Kim, J.K.; Kim, S. (Department of Endodontics, Hadassah-Hebrew University School of Dental Medicine, Jerusalem (Israel))

1991-01-01

383

Contactless electromagnetic phase-shift flowmeter for liquid metals  

International Nuclear Information System (INIS)

We present a concept and test results of an eddy-current flowmeter for liquid metals. The flow rate is determined by applying a weak ac magnetic field to a liquid metal flow and measuring the flow-induced phase disturbance in the external electromagnetic field. The phase disturbance is found to be more robust than that of the amplitude used in conventional eddy-current flowmeters. The basic characteristics of this type of flowmeter are analysed using simple theoretical models, where the flow is approximated by a solid body motion. Design of such a flowmeter is presented and its test results are reported

384

Contactless Electromagnetic Phase-Shift Flowmeter for Liquid Metals  

CERN Document Server

We present a concept and test results of an induction flowmeter for liquid metals. The flow rate is determined by applying a weak AC magnetic field to a liquid metal flow and measuring the flow-induced phase disturbance in the external electromagnetic field. The phase disturbance is found to be more robust than that of the amplitude used in conventional AC flowmeters. The basic characteristics of this type of flowmeter are analysed using simple theoretical models where the flow is approximated by a solid body motion. Design of such a flowmeter is presented and its test results reported.

Priede, J?nis; Gerbeth, Gunter

2010-01-01

385

The NMR blood flowmeter--applications.  

Science.gov (United States)

Nuclear Magnetic Resonance (NMR) permits the noninvasive measurement of blood flow signals unimpaired by clothes, bandages, casts, etc. The cylindrical crossed-coil NMR blood flowmeter was used to measure blood flow through a cross-section of the human forearm. Two calibration procedures are described: one for pulsatile flows and the other for flows with a high non-pulsatile component. Flow measurements from normal arms, from limbs with arterial obstruction, arteriovenous hemodialysis fistulas or other conditions are reported. An application of the flow scanning technique for separation of flow signals from individual arteries (e.g., ulnar and radial) is described. The flat crossed-coil NMR flowmeter was applied to detect blood flow from individual arteries (e.g., brachial, popliteal, etc.). Applications of a ranging technique developed to detect signals at predetermined depths are described. PMID:6459530

Salles-Cunha, S X; Halbach, R E; Battocletti, J H; Sances, A

1981-01-01

386

A New Approach to Laminar Flowmeters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. A...

2010-01-01

387

Theory of the Lorentz force flowmeter  

International Nuclear Information System (INIS)

A Lorentz force flowmeter is a device for the contactless measurement of flow rates in electrically conducting fluids. It is based on the measurement of a force on a magnet system that acts upon the flow. We formulate the theory of the Lorentz force flowmeter which connects the measured force to the unknown flow rate. We first apply the theory to three specific cases, namely (i) pipe flow exposed to a longitudinal magnetic field (ii) pipe flow under the influence of a transverse magnetic field and (iii) interaction of a localized distribution of magnetic material with a uniformly moving sheet of metal. These examples provide the key scaling laws of the method and illustrate how the force depends on the shape of the velocity profile and the presence of turbulent fluctuations in the flow. Moreover, we formulate the general kinematic theory which holds for arbitrary distributions of magnetic material or electric currents and for any velocity distribution and which provides a rational framework for the prediction of the sensitivity of Lorentz force flowmeters in laboratory experiments and in industrial practice

388

Laser Doppler velocimetry for measurement of nonlinearity in the vibrations of the middle ear  

Science.gov (United States)

At audible Frequencies and at sound pressure below 96 dB SPL the mammalian middle ear is known to behave as an almost entirely linear system. However, as we go to higher sound pressure levels, smaller nonlinear distortions begin to appear, and increase with increasing pressure level. Some modern hearing aids seek to remedy hearing impairment by amplifying sounds to sound pressure levels as high as 130 or 140 dB SPL. Thus at these levels the small nonlinear distortions can become significant, and understanding their behaviour could help us to improve the design of these hearing aids. In order to measure the tiny vibration amplitudes of the middle ear, and to detect the even smaller nonlinear distortions, a very sensitive measurement and analysis method is needed. The tiny vibration amplitudes of the middle ear can easily be measured with laser vibrometry. Thanks to the highly linear response of LDV, the technique is also able to measure small nonlinearities. To detect the nonlinear distortions we developed a sophisticated measurement and analysis method based on the use of multisine excitation signals. These signals are specially designed to measure nonlinear systems. We will describe our set up and our stimulation and analysis method in detail, we will then go on to present some results of measurements at different points along the ossicular chain.

Peacock, John; Dirckx, Joris

2014-05-01

389

A solid state laser system for Doppler-free spectroscopy of muonium  

CERN Document Server

to 1MHz, was found to be of the order of 80-120 MHz for a 30-40 mJ output. This chirp was shown to be the result of a fast change of the refractive index in the alexandrite rods, and was found to be directly proportional to the population inversion change during the Q-switched pulse. A method of chirp compensation was developed leading to a reduction of the chirp by an order of magnitude i.e. to the level of 5-15 MHz. The alexandrite output was frequency tripled using LBO and BBO crystals with a conversion efficiency in excess of 10 %, yielding UV pulse energies of 3 to 6 mJ. The 1S-2S transition frequency has been measured to be 2,455,528,940.99 (9.75)(3.5) MHz which is in agreement with the theoretical value of 2,455,528,934.61 (3.44) MHz. Measurement of 1S-2S interval in deuterium, performed primarily to study systematic errors, represents the best pulsed measurement to date and is in an agreement with values obtained with cw lasers. The thesis describes a new high precision measurement of the 1S-2S transi...

Bakule, P

1998-01-01

390

The use of laser Doppler imaging as an aid in clinical management decision making in the treatment of vesicant burns.  

Science.gov (United States)

Vesicants are a group of chemicals recognised, under the terms of the Chemical Weapons Convention, as potential chemical warfare agents whose prime effect on the skin is to cause burns and blistering. Experience of the clinical management of these injuries is not readily available and therefore an accurate assessment of the severity of the lesion and extent of tissue involvement is an important factor when determining the subsequent clinical management strategy for such lesions. This study was performed to assess the use of laser Doppler imaging (LDI) as a noninvasive means of assessing wound microvascular perfusion following challenge with the vesicant agents (sulphur mustard or lewisite) by comparing the images obtained with histopathological analysis of the lesion. Large white pigs were challenged with sulphur mustard (1.91 mg cm(-2)) or lewisite (0.3 mg.cm(-2)) vapour for periods of up to 6 h At intervals of between 1 h and 7 days following vesicant challenge, LDI images were acquired and samples for routine histopathology were taken. The results from this study suggest that LDI was: (i) a simple, reproducible and noninvasive means of assessing changes in tissue perfusion, and hence tissue viability, in developing and healing vesicant burns; (ii) the LDI images correlates well with histopathological assessment of the resulting lesions and the technique was sufficiently sensitive enough to discriminate between skin lesions of different aetiology. These attributes suggest that LDI would be a useful investigative tool that could aid clinical management decision making in the early treatment of vesicant agent-induced skin burns. PMID:9915668

Brown, R F; Rice, P; Bennett, N J

1998-12-01

391

Pulsatile blood flow in human bone assessed by laser-Doppler flowmetry and the interpretation of photoplethysmographic signals.  

Science.gov (United States)

Human bone blood flow, mean blood speed and the number of moving red blood cells were assessed (in arbitrary units), as a function of time, during one cardiac cycle. The measurements were obtained non-invasively on five volunteers by laser-Doppler flowmetry at large interoptode spacing. The investigated bones included: patella, clavicle, tibial diaphysis and tibial malleolus. As hypothesized, we found that in all bones the number of moving cells remains constant during cardiac cycles. Therefore, we concluded that the pulsatile nature of blood flow must be completely determined by the mean blood speed and not by changes in blood volume (vessels dilation). Based on these results, it is finally demonstrated using a mathematical model (derived from the radiative transport theory) that photoplethysmographic (PPG) pulsations observed by others in the literature, cannot be generated by oscillations in blood oxygen saturation, which is physiologically linked to blood speed. In fact, possible oxygen saturation changes during pulsations decrease the amplitude of PPG pulsations due to specific features of the PPG light source. It is shown that a variation in blood oxygen saturation of 3% may induce a negative change of ?1% in the PPG signal. It is concluded that PPG pulsations are determined by periodic 'positive' changes of the reduced scattering coefficient of the tissue and/or the absorption coefficient at constant blood volume. No explicit experimental PPG measurements have been performed. As a by-product of this study, an estimation of the arterial pulse wave velocity obtained from the analysis of the blood flow pulsations give a value of 7.8 m s(-1) (95% confidence interval of the sample mean distribution: [6.7, 9.5] m s(-1)), which is perfectly compatible with data in the literature. We hope that this note will contribute to a better understanding of PPG signals and to further develop the domain of the vascular physiology of human bone. PMID:23443008

Binzoni, Tiziano; Tchernin, David; Hyacinthe, Jean-Noël; Van De Ville, Dimitri; Richiardi, Jonas

2013-03-01

392

Speckle noise influence on measuring turbulence spectra using time-resolved Doppler global velocimetry with laser frequency modulation  

International Nuclear Information System (INIS)

A novel Doppler global velocimeter (DGV) with high temporal resolution is presented as a tool for measuring spatially resolved flow turbulence spectra for three components in order to characterize complex flows, e.g. in turbomachines. The proposed DGV technique is based on a sinusoidal laser frequency modulation. Its maximum available measurement rate equals the modulation frequency and amounts currently to 100 kHz. The harmonic analysis of the detector array signals reduces errors due to detector offset drifts, detector sensitivity changes, ambient light, camera misalignment and beam splitting errors in comparison with conventional DGV systems. The achievable statistical errors are considered by theoretical investigations and by experiments regarding detector noise as well as temporal and spatial scattered light fluctuations, e.g. due to speckles. An error propagation finally provides the determination of the noise power spectral density occurring as virtual turbulence in the measured turbulence spectra. It amounts to about 1.2 × 10?4 (m2 s?2) Hz?2 for mean flow velocities up to 40 m s?1 and 1 nW mean scattered light power per detector element. It rises for higher flow velocities in dependence on the flow turbulence. For the example of a nozzle flow with a mean velocity of 85 m s?1, which is disturbed by a cylinder, the final uncertainty is demonstrated to result in an effective bandwidth oflt in an effective bandwidth of the acquired turbulence spectra of 10 kHz and is thus sufficiently high for flow turbulence analysis. The measured velocity spectra agree well with comparison measurements using a hot-wire anemometer

393

Speckle noise influence on measuring turbulence spectra using time-resolved Doppler global velocimetry with laser frequency modulation  

Science.gov (United States)

A novel Doppler global velocimeter (DGV) with high temporal resolution is presented as a tool for measuring spatially resolved flow turbulence spectra for three components in order to characterize complex flows, e.g. in turbomachines. The proposed DGV technique is based on a sinusoidal laser frequency modulation. Its maximum available measurement rate equals the modulation frequency and amounts currently to 100 kHz. The harmonic analysis of the detector array signals reduces errors due to detector offset drifts, detector sensitivity changes, ambient light, camera misalignment and beam splitting errors in comparison with conventional DGV systems. The achievable statistical errors are considered by theoretical investigations and by experiments regarding detector noise as well as temporal and spatial scattered light fluctuations, e.g. due to speckles. An error propagation finally provides the determination of the noise power spectral density occurring as virtual turbulence in the measured turbulence spectra. It amounts to about 1.2 × 10-4 (m2 s-2) Hz-2 for mean flow velocities up to 40 m s-1 and 1 nW mean scattered light power per detector element. It rises for higher flow velocities in dependence on the flow turbulence. For the example of a nozzle flow with a mean velocity of 85 m s-1, which is disturbed by a cylinder, the final uncertainty is demonstrated to result in an effective bandwidth of the acquired turbulence spectra of 10 kHz and is thus sufficiently high for flow turbulence analysis. The measured velocity spectra agree well with comparison measurements using a hot-wire anemometer.

Fischer, Andreas; König, Jörg; Czarske, Jürgen

2008-12-01

394

FIELD TESTING OF PROTOTYPE ACOUSTIC EMISSION SEWER FLOWMETER  

Science.gov (United States)

This investigation concerns verifying the operating principles of the acoustic emission flowmeter (U.S. Patent 3,958,458) in the natural environment of three different storm sewer field sites in Nassau County, New York. The flowmeter is a novel, passive, nonintrusive method that ...

395

A theoretical model for determining turbine flowmeter sensitivity  

Science.gov (United States)

Analytical model of turbine-type flowmeter guides in the selection of valid extrapolation of available calibration data. An expression for flowmeter performance is developed to include the effects of fluid friction, bearing drag, and magnetic drag upon helical rotor design.

Smith, R. L.

1967-01-01

396

Photonic doppler velocimetry  

International Nuclear Information System (INIS)

We are developing a novel fiber-optic approach to laser Doppler velocimetry as a diagnostic for high explosives tests. Using hardware that was originally developed for the telecommunications industry, we are able to measure surface velocities ranging from centimeters per second to kilometers per second. Laboratory measurements and field trials have shown excellent agreement with other diagnostics

397

Measurement of blood flow velocity in a model of stenosis in vitro and in mesenteric vessels in vivo using non-invasive micro multipoint laser Doppler velocimetry  

Science.gov (United States)

Our research goal is to carry out two-dimensional (2D) and three-dimensional (3D) measurements of the velocity distribution within a single vessel. We modified a non-invasive beam laser Doppler velocimeter using near-infrared light, and linearized the laser to carry out simultaneous multipoint measurements. We also scanned the measurement line in the direction of depth to allow 3D imaging of vascular blood flow in opaque areas in vivo. We used micro multipoint laser Doppler velocimetry (LDV) and a device with improved spatial resolution from 250 to 125 µm. We compared actual and calculated values using a rotating disk with an attached microwire. To demonstrate the effectiveness of the proposed system, blood flowing at a constant rate through a glass capillary and the velocity distribution of flow in the capillary were measured and mapped. The average flow velocity was calculated from the cross-sectional area and flow rate in the glass capillary, and we compared the calculated and measured values. To obtain an image of blood flow velocity in vivo, we measured both 2D and 3D flow velocity distributions in mouse mesenteric vessels.

Akiguchi, Shunsuke; Ishida, Hiroki; Andoh, Tsugunobu; Hachiga, Tadashi; Shimizu, Tadamichi; Kuraishi, Yasushi; Shirakawa, Hiroki; Ueyama, Koji

2012-04-01

398

The influence of wellbore inflow on electromagnetic borehole flowmeter measurements  

Science.gov (United States)

This paper describes a combined field, laboratory, and numerical study of electromagnetic borehole flowmeter measurements acquired without the use of a packer or skirt to block bypass flow around the flowmeter. The most significant finding is that inflow through the wellbore screen changes the ratio of flow through the flowmeter to wellbore flow. Experiments reveal up to a factor of two differences in this ratio for conditions with and without inflow through the wellbore screen. Standard practice is to assume the ratio is constant. A numerical model has been developed to simulate the effect of inflow on the flowmeter. The model is formulated using momentum conservation within the borehole and around the flowmeter. The model is embedded in the MODFLOW-2000 ground water flow code. ?? 2009 National Ground Water Association.

Clemo, T.; Barrash, W.; Reboulet, E. C.; Johnson, T. C.; Leven, C.

2009-01-01

399

Slug flow measurement using a current-sensing electromagnetic flowmeter  

Energy Technology Data Exchange (ETDEWEB)

In order to investigate the characteristics of two-phase slug flow, a current-sensing electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. Theory of a current-sensing electromagnetic flowmeter with high temporal resolution was also developed. A flow pattern coefficient and a localization parameter were introduced for developing two-phase flow. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under singlephase flow was {+-}2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble.

Ahn, Yeh Chan; Oh, Byung Do; Kim, Moo Hwan [Pohang Univ. of Science and Tech., Pohang (Korea, Republic of); Cha, Jae Eun [KAERI, Taejon (Korea, Republic of)

2003-07-01

400

Slug flow measurement using a current-sensing electromagnetic flowmeter  

International Nuclear Information System (INIS)

In order to investigate the characteristics of two-phase slug flow, a current-sensing electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. Theory of a current-sensing electromagnetic flowmeter with high temporal resolution was also developed. A flow pattern coefficient and a localization parameter were introduced for developing two-phase flow. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under singlephase flow was ±2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble

 
 
 
 
401

An investigation of the motion of small particles as related to the formulation of zero gravity experiments. [experimental design using laser doppler velocimetry  

Science.gov (United States)

The nature of Brownian motion and historical theoretical investigations of the phenomemon are reviewed. The feasibility of using a laser anemometer to perform small particle experiments in an orbiting space laboratory was investigated using latex particles suspended in water in a plastic container. The optical equipment and the particle Doppler analysis processor are described. The values of the standard deviation obtained for the latex particle motion experiment were significantly large compared to corresponding velocity, therefore, their accuracy was suspect and no attempt was made to draw meaningful conclusions from the results.

Sastry, V. S.

1980-01-01

402

Development of a wet gas flowmeter  

Energy Technology Data Exchange (ETDEWEB)

A new multiphase flowmeter, particularly suited for wet gas metering, has been developed. The meter working principle is the isokinetic sampling of the gas-liquid mixture, followed by separation and individual metering of the gas and the liquid phase. The liquid flowrate is derived from the value of the sampled liquid flowrate. The gas flowrate is measured with a multiphase nozzle. Preliminary tests have shown that both the gas and the liquid flowrates can be determined with an error less than 5%. The meter can be autocalibrated and allows the water-cut to be measured with any prescribed precision. (author)

Andreussi, P.; Ciandri, P.; Faluomi, V. [TRA Sistemi, Pisa (Italy)

2000-07-01

403

Three-component laser Doppler velocimetry measurements in the vicinity of mechanical heart valves in a mock-circulatory loop  

Science.gov (United States)

Streakline flow visualization and three-component laser Doppler velocimetry were conducted in a mock-circulatory loop on four mechanical heart valve types in the mitral position. Measurements were conducted in the regurgitant flow region proximal to the valve. Results for the Bjork-Shiley Monostrutsp{TM} valve showed a highly non-uniform flow at valve closure, with very large velocities in the minor orifice region. These velocities were on the order of 15-20 mps and lasted less than one millisecond. Following closure, an interval of sustained regurgitant flow persisted for the duration of systole. Reynolds stresses were calculated from three-dimensional data, and yielded a maximum of 8,100 dyne/cmsp2. Values as high as 80,000 dyne/cmsp2 were calculated during the initial spike, but due to the intermittency of the spike, they are artificially high. Similar measurements were conducted in the minor orifice of the Medtronic-Hall valve, and maximum velocities of about 4 mps were measured during the sustained regurgitant flow. Maximum Reynolds shear stresses were about 7,000 dyne/cmsp2. The velocity spike at closing was noted with this valve also. Two-component measurements around the center hole in the occluder showed a sustained jet with maximum velocities of about 1 mps, and maximum Reynolds shear stresses of about 2,000 dyne/cmsp2. Measurements in the St. Jude Medical valve showed velocities and stresses to be very low. No closing spike was measured, and sustained velocities were observed in the hinge region of about 0.2 mps with maximum stresses of about 1,000 dyne/cmsp2. The CarboMedicssp{TM} valve showed a regurgitant jets emanating from the gap between the leaflet and valve housing ring, with velocities of 3.3 mps for the duration of systole, and calculated stresses of 8,100 dyne/cmsp2. No closing spike was noted. Differences between two and three-dimensional Reynolds shear stresses were significant only at locations where two-dimensional calculated values were small (a few hundred dyne/cmsp2). The effect of gap width on maximum shear stress for the Bjork-Shiley Monostrutsp{TM} valve produced inconclusive results. Comparison of stresses with clinical blood damage data showed the Medtronic-Hall and CarboMedicssp{TM} valves to correlate well; however, comparisons with clinical data for the other two valves were inconclusive.

Meyer, Richard Scott

404

Different imaging methods in the comparative assessment of vascular lesions: color-coded duplex sonography, laser Doppler perfusion imaging, and infrared thermography  

Science.gov (United States)

Aim of the study was the comparative investigation of cutaneous and subcutaneous vascular lesions. By means of color coded duplex sonography (CCDS), laser doppler perfusion imaging (LDPI) and infrared thermography (IT) we examined hemangiomas, vascular malformations and portwine stains to get some evidence about depth, perfusion and vascularity. LDI is a helpful method to get an impression of the capillary part of vascular lesions and the course of superficial vessels. CCDS has disadvantages in the superficial perfusion's detection but connections to deeper vascularizations can be examined precisely, in some cases it is the only method for visualizing vascular malformations. IT gives additive hints on low blood flow areas or indicates arterial-venous-shunts. Only the combination of all imaging methods allows a complete assessment, not only for planning but also for controlling the laser treatment of vascular lesions.

Urban, Peter; Philipp, Carsten M.; Weinberg, Lutz; Berlien, Hans-Peter

1997-12-01

405

Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.  

Energy Technology Data Exchange (ETDEWEB)

A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers). Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured - MWNTs and Ag{sub 2}Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37 {+-} 26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag{sub 2}Ga nanoneedles have a greater optical scattering efficiency than MWNTs, their vibration spectra was more extensively studied. The thermal vibration spectra of Ag{sub 2}Ga nanoneedles was measured under both ambient and low-vacuum conditions. The operational deflection shapes of the vibrating Ag{sub 2}Ga nanoneedles was also measured, allowing confirmation of the eigenmodes of vibration. The modulus of the crystalline nanoneedles was 84.3 {+-} 1.0 GPa. Gas damping is the dominate mechanism of energy loss for nanowires oscillating under ambient conditions. The measured quality factors, Q, of oscillation are in line with theoretical predictions of air damping in the free molecular gas damping regime. In the free molecular regime, Q{sub gas} is linearly proportional to the density and diameter of the nanowire and inversely proportional to the air pressure. Since the density of the Ag{sub 2}Ga nanoneedles is three times that of the MWNTs, the Ag{sub 2}Ga nanoneedles have greater Q at atmospheric pressures. Our initial measurements of Q for Ag{sub 2}Ga nanoneedles in low-vacuum (10 Torr) suggest that the intrinsic Q of these nanoneedles may be on the order of 1000. The epitaxial carbon that grows after heating (000{bar 1}) silicon carbide (SiC) to high temperatures (1450-1600) in vacuum was also studied. At these high temperatures, the surface Si atoms sublime and the remaining C atoms reconstruct to form graphene. X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the quality of the few-layer graphene (FLG) surface. The XPS studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples. STM studies revealed a wide variety of nanometer-scale features that include sharp carbon-rich ridges, moire superlattices, one-dimensional line defects, and grain boundaries. By imaging these features with atomic scale resolution, considerable insight into the growth mechanisms of FLG on the carbon-face of SiC is obtained.

Biedermann, Laura Butler

2009-09-01

406

Laser Doppler Velocimetry Primer.  

Science.gov (United States)

Advanced research in experimental fluid dynamics required a familiarity with sophisticated measurement techniques. In some cases, the development and application of new techniques is required for difficult measurements. Optical methods and in particular, ...

W. D. Bachalo

1985-01-01

407

Coronary stents cause high velocity fluctuation with a flow acceleration and flow reduction in jailed branches: an in vitro study using laser-Doppler anemometry.  

Science.gov (United States)

Flow disturbance and reduced blood flow have been associated with higher restenosis rates and clinical adverse events after coronary interventions. In the present study, we sought to investigate flow alterations that occurred after stent implantation in a coronary model, within and adjacent to the stented segment. Two stents (Carbostent, Tetrastent) with different strut design were deployed in the left anterior descending artery (LAD) of a 1:1 scaled silicon coronary model. The model was mounted into an artificial circulation and showed distensibility and rheologic behavior comparable to human coronaries. Flow profiles were assessed using laser-Doppler anemometry. Both stents induced a transitional flow within the stents, in the jailed branch as well as in the adjacent segments. However, the alterations in flow were less marked using the Carbostent having stents with thinner struts and a larger strut cell area, and thus seem to be more favorable in avoiding bifurcation lesions. This study shows precisely that stent implantation induces flow disturbances in segments known to be prone for restenosis. Investigations using laser-Doppler measurements may enlighten rheologic phenomena inducing restenosis and help in optimizing stent design and deployment techniques. PMID:23380899

Dörler, Jakob; Frick, Matthias; Hilber, Monika; Breitfuss, Harald; Abdel-Hadi, Mohammed N; Pachinger, Otmar; Liepsch, Dieter; Schwarzacher, Severin P

2012-01-01

408

A New Approach to Laminar Flowmeters  

Directory of Open Access Journals (Sweden)

Full Text Available After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. After a subsequent analysis on how these non-linearity errors can be reduced, a new disposition of this type of flowmeters is introduced. This device makes used of flow elements having pressure taps at three locations along its length and connected to three isolated chambers. In this way, the static pressure can be measured at three locations and contributed to by the pressure taps at the level of each chamber. Thus the linearization error is reduced with an additional advantage of producing a reduced pressure drop.

Alvaro Deibe

2010-11-01

409

The NMR blood flowmeter--design.  

Science.gov (United States)

Two types of crossed-coil nuclear magnetic resonance (NMR) blood flowmeter detectors have been developed for the noninvasive measurement of blood flow. The first is a cylindrical coil configuration suitable for limb blood measurement. A cylindrical flowmeter (12.5 cm internal diam) operating at a nuclear resonance frequency of 3.2 MHz has been applied to measurement of flow in the forearm. The second type is the flat crossed-coil detector, which retains many of the operational advantages of the cylindrical detector, but is suitable for blood flow measurement of almost any surface of the body. Three flat crossed-coil detectors are described, operating at NMR frequencies of 9, 21.4, and 75 MHz. Two types of intermediate frequency signal processors have been used in the NMR receivers, a simple diode type, and a synchronous detector. The synchronous detector is preferred for its ease of operation and superior stability. Modular detection systems containing transmitter, receiver, post-detector signal conditioning, and power supply have been designed for all of the flat crossed-coil detectors. A self-contained synchronous detector module is included in the 21.4 and 75 MHz systems. PMID:6459529

Halbach, R E; Battocletti, J H; Salles-Cunha, S X; Sances, A

1981-01-01

410

Analytical modeling of electromagnetic induction flowmeters  

International Nuclear Information System (INIS)

Precise measurement of the flow rate of the cooling sodium in fast breeders is of crucial importance for the safety of the reactor. For the case of big size pipes, this task is classically achieved by using a conduction electromagnetic flowmeter. Nevertheless, when the presence of electrodes, placed in direct contact with the liquid metal, has to be avoided, or when geometrical considerations are of prime importance, the use of a contactless induction flowmeter can be more convenient. In its most simple version, it is composed of three closely spaced coaxial coils wound around the circular pipe to be monitored. The center coil, which acts as the primary excitator, is supply with an a.c. current and delivers a poloidal magnetic field. Two other measuring coils are placed symmetrically with respect to the central one and are electrically connected in opposition in such a way that the resulting induced voltage in these coils will be zero when the fluid is at rest. When the fluid is moving, the convection of the magnetic field lines by the flow is responsible for an unbalance between the induced voltage in each one of the end coils

411

A new approach to laminar flowmeters.  

Science.gov (United States)

After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry